RESPIRATION - COMPREHENSIVE QUESTION PAPER

SECTION A: MULTIPLE CHOICE QUESTIONS (MCQs) - 100 Questions

Choose the correct option for each question.

Respiration is a: a) Physical process b) Chemical process c) Biochemical process d) Mechanical process
The word equation for respiration is: a) CO₂ + H₂O → Glucose + O₂ b) Glucose + O₂ → CO₂ + H₂O + Energy c) Glucose → Ethanol + CO₂ d) Light + CO₂ → Glucose
Respiration is an _______ process: a) Endothermic b) Exothermic c) Isothermic d) Adiabatic
The main energy currency of the cell is: a) ADP b) ATP c) Glucose d) Oxygen
ATP stands for: a) Adenosine Triphosphate b) Adenine Triphosphate c) Adenosine Tetraphosphate d) Adenine Tetraphosphate
Aerobic respiration occurs in the presence of: a) Carbon dioxide b) Water c) Oxygen d) Nitrogen
Anaerobic respiration occurs in: a) Presence of oxygen b) Absence of oxygen c) Presence of carbon dioxide d) Presence of water
Which type of respiration releases more energy? a) Aerobic b) Anaerobic c) Both equal d) Neither
Alcoholic fermentation produces: a) Lactic acid b) Ethanol c) Acetic acid d) Formic acid
Yeast performs which type of respiration in absence of oxygen? a) Aerobic b) Anaerobic c) Both d) Neither
In plants, respiration occurs in: a) Only leaves b) Only roots c) Only stems d) All living cells
Photosynthesis is a _______ process: a) Catabolic b) Anabolic c) Neither d) Both
Respiration is a _______ process: a) Catabolic b) Anabolic c) Neither d) Both
Photosynthesis occurs during: a) Day only b) Night only c) Day and night d) Never
Respiration occurs during: a) Day only b) Night only c) Day and night d) Never
In photosynthesis, plants take in: a) Oxygen b) Carbon dioxide c) Nitrogen d) Hydrogen
In respiration, plants take in: a) Oxygen b) Carbon dioxide c) Nitrogen d) Hydrogen
The breakdown of glucose in respiration is: a) Complete in aerobic b) Incomplete in anaerobic c) Both a and b d) Neither
Waterlogged soil conditions lead to: a) Aerobic respiration b) Anaerobic respiration c) No respiration d) Photosynthesis
Chlorophyll is required for: a) Respiration b) Photosynthesis c) Both d) Neither
Energy is released in respiration in the form of: a) Heat b) Light c) ATP d) Sound
The reactants of aerobic respiration are: a) CO₂ and H₂O b) Glucose and O₂ c) Ethanol and CO₂ d) Light and CO₂
The products of aerobic respiration are: a) Glucose and O₂ b) CO₂, H₂O and Energy c) Ethanol and CO₂ d) Only energy
Which process stores energy? a) Respiration b) Photosynthesis c) Both d) Neither
Which process releases energy? a) Respiration b) Photosynthesis c) Both d) Neither
Anaerobic respiration in plants produces: a) Lactic acid b) Ethanol c) Acetic acid d) Citric acid
The amount of energy released in anaerobic respiration is: a) More than aerobic b) Less than aerobic c) Same as aerobic d) No energy
Most plants and animals perform: a) Aerobic respiration b) Anaerobic respiration c) Both d) Neither
Bacteria can perform: a) Only aerobic b) Only anaerobic c) Both types d) No respiration
In the word equation of alcoholic fermentation, glucose breaks down into: a) CO₂ and H₂O b) Ethanol and CO₂ c) Lactic acid d) ATP only
Respiration is vital for: a) Growth b) Movement c) Reproduction d) All of these
Body temperature is maintained using energy from: a) Photosynthesis b) Respiration c) Digestion d) Excretion
The gas exchange in photosynthesis involves: a) Taking O₂, releasing CO₂ b) Taking CO₂, releasing O₂ c) No gas exchange d) Taking N₂
The gas exchange in respiration involves: a) Taking O₂, releasing CO₂ b) Taking CO₂, releasing O₂ c) No gas exchange d) Taking N₂
Photosynthesis occurs only in cells with: a) Nucleus b) Mitochondria c) Chlorophyll d) Ribosomes
The complementary process to photosynthesis is: a) Digestion b) Respiration c) Excretion d) Reproduction
Light energy is converted to chemical energy in: a) Respiration b) Photosynthesis c) Digestion d) Excretion
Chemical energy is released from food in: a) Respiration b) Photosynthesis c) Digestion d) Absorption
Glucose is synthesized in: a) Respiration b) Photosynthesis c) Digestion d) Excretion
Glucose is broken down in: a) Respiration b) Photosynthesis c) Absorption d) Excretion
Oxygen is produced in: a) Respiration b) Photosynthesis c) Digestion d) Excretion
Carbon dioxide is produced in: a) Respiration b) Photosynthesis c) Both d) Neither
Water is required for: a) Respiration only b) Photosynthesis only c) Both processes d) Neither
Energy is stored as chemical energy in: a) Respiration b) Photosynthesis c) Both d) Neither
The continuous process in plants is: a) Photosynthesis b) Respiration c) Both d) Neither
Alcoholic fermentation is carried out by: a) Animals b) Green plants c) Yeast d) Bacteria only
Root tissues in waterlogged conditions perform: a) Aerobic respiration b) Anaerobic respiration c) Photosynthesis d) No metabolic process
The incomplete breakdown of glucose occurs in: a) Aerobic respiration b) Anaerobic respiration c) Photosynthesis d) Digestion
ATP molecules serve as: a) Food storage b) Energy currency c) Structural component d) Enzyme
Organic substances like glucose are used in: a) Photosynthesis b) Respiration c) Both d) Neither
Living organisms obtain energy from: a) Inorganic substances b) Organic substances c) Water d) Air
The process that occurs in all living cells is: a) Photosynthesis b) Respiration c) Reproduction d) Growth
Exothermic processes: a) Absorb energy b) Release energy c) Store energy d) Transform energy
Endothermic processes: a) Absorb energy b) Release energy c) Store energy d) Destroy energy
Life processes require energy from: a) Photosynthesis b) Respiration c) Digestion d) Excretion
The building up of food molecules occurs in: a) Catabolic process b) Anabolic process c) Both d) Neither
The breaking down of food molecules occurs in: a) Catabolic process b) Anabolic process c) Both d) Neither
Daytime occurrence is characteristic of: a) Respiration b) Photosynthesis c) Both d) Neither
Nighttime occurrence is characteristic of: a) Respiration only b) Photosynthesis only c) Both d) Neither
Continuous occurrence is characteristic of: a) Respiration b) Photosynthesis c) Both d) Neither
Limited oxygen supply leads to: a) Aerobic respiration b) Anaerobic respiration c) Photosynthesis d) No respiration
Complete breakdown of glucose produces: a) Ethanol b) Lactic acid c) CO₂ and H₂O d) Only CO₂
Incomplete breakdown of glucose produces: a) CO₂ and H₂O b) Ethanol and CO₂ c) Only H₂O d) Only O₂
The presence of light is essential for: a) Respiration b) Photosynthesis c) Both d) Neither
Mitochondria are associated with: a) Photosynthesis b) Respiration c) Both d) Neither
Chloroplasts are associated with: a) Photosynthesis b) Respiration c) Both d) Neither
The reverse process of photosynthesis is: a) Digestion b) Respiration c) Excretion d) Absorption
Vital for plant life are: a) Photosynthesis only b) Respiration only c) Both processes d) Neither
Distinct processes in plants are: a) Photosynthesis and respiration b) Growth and reproduction c) Absorption and excretion d) All of these
Energy transformation in photosynthesis: a) Chemical to light b) Light to chemical c) Heat to chemical d) Chemical to heat
Energy transformation in respiration: a) Chemical to light b) Light to chemical c) Chemical to usable energy d) Heat to chemical
The main difference between aerobic and anaerobic respiration is: a) Products formed b) Oxygen requirement c) Energy released d) All of these
Fermentation is a type of: a) Aerobic respiration b) Anaerobic respiration c) Photosynthesis d) Digestion
Lactic acid fermentation occurs in: a) Yeast b) Plants c) Animals d) Bacteria
The gas released during alcoholic fermentation is: a) Oxygen b) Carbon dioxide c) Nitrogen d) Hydrogen
Waterlogged conditions prevent: a) Photosynthesis b) Aerobic respiration c) Anaerobic respiration d) All processes
The energy currency ATP is synthesized during: a) Photosynthesis b) Respiration c) Both d) Neither
Food molecules are organic substances like: a) Water b) Glucose c) Carbon dioxide d) Oxygen
The biochemical process of energy release is: a) Photosynthesis b) Respiration c) Digestion d) Absorption
Living cells continuously perform: a) Photosynthesis b) Respiration c) Reproduction d) Growth
The complementary nature of photosynthesis and respiration means: a) They are opposite b) They are similar c) They support each other d) They are independent
Plant tissues that lack oxygen perform: a) Aerobic respiration b) Anaerobic respiration c) Photosynthesis d) No respiration
The amount of energy in aerobic respiration is: a) Small b) Large c) Moderate d) No energy
The amount of energy in anaerobic respiration is: a) Small b) Large c) Moderate d) No energy
Oxygen is consumed in: a) Photosynthesis b) Respiration c) Both d) Neither
Carbon dioxide is consumed in: a) Photosynthesis b) Respiration c) Both d) Neither
The process that builds up glucose is: a) Respiration b) Photosynthesis c) Digestion d) Excretion
The process that breaks down glucose is: a) Respiration b) Photosynthesis c) Absorption d) Reproduction
Energy for movement comes from: a) Photosynthesis b) Respiration c) Digestion d) Excretion
Energy for growth comes from: a) Photosynthesis b) Respiration c) Absorption d) Reproduction
Light-dependent process is: a) Respiration b) Photosynthesis c) Both d) Neither
Light-independent process is: a) Respiration b) Photosynthesis c) Both d) Neither
The feature common to both processes is: a) Light requirement b) Chlorophyll requirement c) Energy involvement d) Oxygen production
The feature different in both processes is: a) Energy involvement b) Occurrence in plants c) Gas exchange d) Cell requirement
Alcoholic beverages are produced by: a) Aerobic respiration b) Anaerobic respiration c) Photosynthesis d) Digestion
Bread making involves: a) Aerobic respiration b) Anaerobic respiration c) Photosynthesis d) Fermentation
The process essential for survival is: a) Photosynthesis b) Respiration c) Both d) Neither
Energy storage occurs in: a) Respiration b) Photosynthesis c) Digestion d) Excretion
Energy release occurs in: a) Respiration b) Photosynthesis c) Absorption d) Reproduction
The most efficient type of respiration is: a) Aerobic b) Anaerobic c) Fermentation d) All equal

SECTION B: SHORT ANSWER QUESTIONS (1 Mark) - 100 Questions

Answer in one word or one sentence.

What is respiration?
Write the word equation for respiration.
Is respiration an exothermic or endothermic process?
What is the full form of ATP?
What is the main energy currency of the cell?
Define aerobic respiration.
Define anaerobic respiration.
Which type of respiration releases more energy?
Name the products of alcoholic fermentation.
Which organism commonly performs alcoholic fermentation?
Where does respiration occur in plants?
Is photosynthesis anabolic or catabolic?
Is respiration anabolic or catabolic?
When does photosynthesis occur?
When does respiration occur?
What gas do plants take in during photosynthesis?
What gas do plants take in during respiration?
What gas do plants release during photosynthesis?
What gas do plants release during respiration?
Name two types of respiration.
What conditions lead to anaerobic respiration in plant roots?
What is required for photosynthesis to occur in plant cells?
Name the reactants of aerobic respiration.
Name the products of aerobic respiration.
Which process stores energy - photosynthesis or respiration?
Which process releases energy - photosynthesis or respiration?
What type of energy transformation occurs in photosynthesis?
What type of energy transformation occurs in respiration?
Name one example where anaerobic respiration occurs.
What is the word equation for alcoholic fermentation?
Why is respiration called a biochemical process?
What activities require energy from respiration?
How are photosynthesis and respiration related?
What is meant by complementary processes?
Why do plants need both photosynthesis and respiration?
What happens to glucose during respiration?
What happens during the breakdown of food molecules?
Name the process that builds up food molecules.
Why is ATP called the energy currency?
What is the difference between complete and incomplete breakdown?
Under what conditions does alcoholic fermentation occur?
Name two organisms that perform anaerobic respiration.
What is the main difference between aerobic and anaerobic respiration?
Why is oxygen important for aerobic respiration?
What happens when oxygen supply is limited?
Which cells in plants have chlorophyll?
In which cells does respiration occur?
What is the source of energy for photosynthesis?
What is the source of energy in respiration?
Name the process opposite to photosynthesis.
What makes respiration an exothermic reaction?
How is energy captured during respiration?
What is the role of mitochondria?
What is the role of chloroplasts?
Why do plants respire continuously?
When do plants perform photosynthesis?
What gas exchange occurs during photosynthesis?
What gas exchange occurs during respiration?
Name the end products of glucose breakdown in aerobic respiration.
Name the end products of glucose breakdown in anaerobic respiration.
Which type of fermentation occurs in yeast?
What conditions are needed for aerobic respiration?
What conditions are needed for anaerobic respiration?
Why is less energy released in anaerobic respiration?
What is meant by waterlogged conditions?
How do waterlogged conditions affect plant roots?
What is the main substrate for respiration?
What is the main product of photosynthesis?
Why is glucose important for living organisms?
What happens to the energy stored in glucose?
Name the process that occurs in all living cells.
Name the process that occurs only in green plant cells.
What is the significance of continuous respiration?
Why doesn't photosynthesis occur at night?
What is the role of oxygen in aerobic respiration?
What is the role of carbon dioxide in photosynthesis?
How do plants obtain energy for their life processes?
What is the difference between day and night processes in plants?
Why is respiration essential for life?
What is the relationship between photosynthesis and respiration?
Name one industrial application of fermentation.
What type of respiration occurs in muscle cells during intense exercise?
How does anaerobic respiration help organisms survive?
What is the importance of ATP in cellular processes?
Why do both plants and animals need respiration?
What is meant by energy currency?
How is chemical energy stored in ATP?
What initiates the process of respiration?
Where is the energy from respiration utilized?
What is the fundamental difference between photosynthesis and respiration?
Why are photosynthesis and respiration called complementary?
What happens when plants cannot perform photosynthesis?
What happens when respiration stops in living organisms?
How do plants balance photosynthesis and respiration?
What is the net effect of photosynthesis and respiration in plants?
Why is glucose the preferred substrate for respiration?
How does temperature affect respiration?
What is the evolutionary significance of aerobic respiration?
Why do plants need both processes to survive?
What determines the type of respiration in an organism?

SECTION C: SHORT ANSWER QUESTIONS (2 Marks) - 50 Questions

Answer in 2-3 sentences.

Explain why respiration is called a biochemical process.
Compare the energy released in aerobic and anaerobic respiration.
Describe the conditions required for aerobic respiration.
Explain what happens during alcoholic fermentation.
Why do plant roots in waterlogged soil perform anaerobic respiration?
Distinguish between the reactants of photosynthesis and respiration.
Explain why ATP is called the energy currency of the cell.
Describe the gas exchange that occurs during respiration.
Compare the occurrence of photosynthesis and respiration in terms of time.
Explain why photosynthesis is called an anabolic process.
Describe why respiration is called a catabolic process.
Explain the complementary relationship between photosynthesis and respiration.
Compare the energy transformations in photosynthesis and respiration.
Describe what happens to glucose during aerobic respiration.
Explain why anaerobic respiration produces less energy.
Compare the products of aerobic and anaerobic respiration.
Describe the role of oxygen in cellular respiration.
Explain why respiration occurs continuously in living cells.
Compare the locations where photosynthesis and respiration occur.
Describe the importance of respiration for living organisms.
Explain how yeast performs fermentation.
Compare complete and incomplete breakdown of glucose.
Describe the conditions that favor anaerobic respiration.
Explain why plants need both photosynthesis and respiration.
Compare the gas exchanges in photosynthesis and respiration.
Describe the role of chlorophyll in photosynthesis vs respiration.
Explain the significance of the exothermic nature of respiration.
Compare the energy requirements of photosynthesis and respiration.
Describe what makes aerobic respiration more efficient.
Explain the difference between fermentation and respiration.
Compare the substrates used in photosynthesis and respiration.
Describe the cellular locations of photosynthesis and respiration.
Explain why both processes are essential for plant survival.
Compare the environmental conditions needed for both processes.
Describe the relationship between glucose production and consumption in plants.
Explain how respiration provides energy for life processes.
Compare the oxygen requirements of both processes.
Describe the carbon dioxide exchange in both processes.
Explain why respiration is vital for maintaining body temperature.
Compare the complexity of aerobic vs anaerobic pathways.
Describe how plants balance energy production and consumption.
Explain the role of respiration in plant growth and development.
Compare the efficiency of energy capture in both processes.
Describe the importance of continuous ATP production.
Explain how waterlogged conditions affect plant metabolism.
Compare the evolutionary advantages of aerobic respiration.
Describe the relationship between breathing and cellular respiration.
Explain why some organisms can survive without oxygen.
Compare the industrial applications of aerobic and anaerobic processes.
Describe how environmental factors affect the rate of respiration.

SECTION D: LONG ANSWER QUESTIONS (3 Marks) - 25 Questions

Answer in 4-5 sentences with detailed explanation.

Explain the process of respiration and its importance for living organisms. Include the word equation and mention why it's called an exothermic process.
Compare and contrast aerobic and anaerobic respiration. Include their word equations, energy yield, and examples of organisms that perform each type.
Describe the complementary relationship between photosynthesis and respiration in plants. Explain how these processes balance each other and why both are essential.
Explain alcoholic fermentation in detail. Include the conditions required, organisms involved, word equation, and its practical applications.
Discuss the differences between photosynthesis and respiration in terms of their nature, energy changes, reactants, products, and occurrence.
Explain why plant roots in waterlogged soil switch to anaerobic respiration. Describe the consequences of this change and how it affects the plant.
Describe the role of ATP in cellular processes. Explain how it's produced during respiration and why it's called the energy currency of the cell.
Explain the concept of energy transformation in both photosynthesis and respiration. Discuss how these transformations are crucial for life on Earth.
Compare the efficiency of aerobic and anaerobic respiration. Explain why aerobic respiration is more efficient and under what conditions organisms use anaerobic respiration.
Describe the gas exchange processes in photosynthesis and respiration. Explain how these complement each other in maintaining atmospheric balance.
Explain why respiration is called a catabolic process while photosynthesis is anabolic. Describe the significance of these opposing processes in plant metabolism.
Discuss the continuous nature of respiration versus the intermittent nature of photosynthesis. Explain how plants manage their energy needs throughout day and night.
Explain the breakdown of glucose in both aerobic and anaerobic conditions. Compare the products formed and energy released in each case.
Describe the importance of respiration for various life processes. Explain how the energy from respiration is used for growth, movement, reproduction, and temperature regulation.
Explain how different environmental conditions affect the type of respiration performed by organisms. Give specific examples and their consequences.
Discuss the evolutionary significance of aerobic respiration. Explain why most complex organisms depend on aerobic respiration for their survival.
Explain the relationship between photosynthesis and respiration in maintaining the oxygen-carbon dioxide cycle in nature.
Describe how plants balance their energy production through photosynthesis and energy consumption through respiration during different times of the day.
Explain the concept of fermentation as a survival mechanism. Discuss how organisms use fermentation when normal respiration is not possible.
Compare the cellular locations and requirements for photosynthesis and respiration. Explain why respiration can occur in all cells while photosynthesis cannot.
Discuss the practical applications of understanding respiratory processes. Include examples from industry, medicine, and agriculture.
Explain how the study of respiration helps us understand the energy flow in ecosystems. Discuss the connection between producers and consumers.
Describe the factors that can affect the rate of respiration in organisms. Explain how these factors influence energy production and organism survival.
Explain the biochemical significance of respiration being an exothermic process. Discuss how organisms capture and utilize this released energy.
Discuss the interdependence of photosynthesis and respiration in maintaining life on Earth. Explain how disruption of either process affects the global ecosystem.

Answer Key

Respiration - Answer Script

SECTION A: MULTIPLE CHOICE QUESTIONS (MCQs)

c) Biochemical process
b) Glucose + O₂ → CO₂ + H₂O + Energy
b) Exothermic
b) ATP
a) Adenosine Triphosphate
c) Oxygen
b) Absence of oxygen
a) Aerobic
b) Ethanol
b) Anaerobic
d) All living cells
b) Anabolic
a) Catabolic
a) Day only
c) Day and night
b) Carbon dioxide
a) Oxygen
c) Both a and b
b) Anaerobic respiration
b) Photosynthesis
c) ATP
b) Glucose and O₂
b) CO₂, H₂O and Energy
b) Photosynthesis
a) Respiration
b) Ethanol
b) Less than aerobic
a) Aerobic respiration
c) Both types
b) Ethanol and CO₂
d) All of these
b) Respiration
b) Taking CO₂, releasing O₂
a) Taking O₂, releasing CO₂
c) Chlorophyll
b) Respiration
b) Photosynthesis
a) Respiration
b) Photosynthesis
a) Respiration
b) Photosynthesis
a) Respiration
b) Photosynthesis only
b) Photosynthesis
b) Respiration
c) Yeast
b) Anaerobic respiration
b) Anaerobic respiration
b) Energy currency
b) Respiration
b) Organic substances
b) Respiration
b) Release energy
a) Absorb energy
b) Respiration
b) Anabolic process
a) Catabolic process
b) Photosynthesis
a) Respiration only
a) Respiration
b) Anaerobic respiration
c) CO₂ and H₂O
b) Ethanol and CO₂
b) Photosynthesis
b) Respiration
a) Photosynthesis
b) Respiration
c) Both processes
a) Photosynthesis and respiration
b) Light to chemical
c) Chemical to usable energy
d) All of these
b) Anaerobic respiration
c) Animals
b) Carbon dioxide
b) Aerobic respiration
b) Respiration
b) Glucose
b) Respiration
b) Respiration
c) They support each other
b) Anaerobic respiration
b) Large
a) Small
b) Respiration
a) Photosynthesis
b) Photosynthesis
a) Respiration
b) Respiration
b) Respiration
b) Photosynthesis
a) Respiration
c) Energy involvement
c) Gas exchange
b) Anaerobic respiration
d) Fermentation
c) Both
b) Photosynthesis
a) Respiration
a) Aerobic

SECTION B: SHORT ANSWER QUESTIONS (1 Mark)

Respiration is the biochemical process of releasing energy from organic substances.
Glucose + Oxygen → Carbon Dioxide + Water + Energy.
Exothermic.
Adenosine Triphosphate.
ATP (Adenosine Triphosphate).
Respiration that occurs in the presence of oxygen.
Respiration that occurs in the absence of oxygen.
Aerobic respiration.
Ethanol and Carbon Dioxide.
Yeast.
In all living cells.
Anabolic.
Catabolic.
During the day (in the presence of light).
Continuously (day and night).
Carbon dioxide.
Oxygen.
Oxygen.
Carbon dioxide.
Aerobic and anaerobic respiration.
Waterlogged soil conditions.
Chlorophyll and light.
Glucose and Oxygen.
Carbon Dioxide, Water, and Energy.
Photosynthesis.
Respiration.
Light energy to chemical energy.
Chemical energy to usable energy (ATP).
Yeast (alcoholic fermentation) or muscle cells (lactic acid fermentation).
Glucose → Ethanol + Carbon Dioxide + Energy.
It involves chemical reactions occurring within living organisms.
Growth, movement, and maintaining body temperature.
They are complementary processes; the products of one are the reactants of the other.
Two processes that balance or complete each other.
Photosynthesis produces food, and respiration releases energy from that food.
It is broken down to release energy.
Energy is released.
Photosynthesis.
It is the main molecule used by cells to store and transfer energy.
Complete breakdown yields more energy than incomplete breakdown.
In the absence of oxygen.
Yeast and some bacteria.
The requirement of oxygen and the amount of energy released.
It acts as the final electron acceptor, allowing for maximum energy release.
Anaerobic respiration occurs.
Cells in leaves and sometimes stems.
In all living cells.
Sunlight.
The chemical bonds in glucose.
Respiration.
It releases energy in the form of heat and ATP.
It is captured in the form of ATP molecules.
They are the site of aerobic respiration.
They are the site of photosynthesis.
To continuously provide energy for life processes.
During the day, in the presence of light.
Intake of CO₂ and release of O₂.
Intake of O₂ and release of CO₂.
Carbon dioxide and water.
Ethanol and carbon dioxide (in yeast) or lactic acid (in animals).
Alcoholic fermentation.
Presence of oxygen.
Absence of oxygen.
The breakdown of glucose is incomplete.
Soil saturated with water, leaving no air spaces.
They switch to anaerobic respiration.
Glucose.
Glucose.
It is the primary source of energy for most organisms.
It is released during respiration to power cellular activities.
Respiration.
Photosynthesis.
It ensures a constant supply of energy for survival.
It requires light energy.
It is the final electron acceptor in the electron transport chain.
It is the carbon source for building glucose.
Through respiration.
Photosynthesis occurs during the day, while respiration occurs day and night.
It provides the energy required for all life functions.
They are complementary, with the products of one being the reactants of the other.
Brewing and baking.
Lactic acid fermentation (a type of anaerobic respiration).
It allows them to produce some ATP even when oxygen is unavailable.
It provides readily usable energy for cellular work.
To break down food and release energy for their life processes.
A molecule that stores and transports chemical energy within cells.
In the high-energy phosphate bonds.
The presence of glucose and the cell's need for energy.
In all metabolic activities, such as growth, repair, and movement.
Photosynthesis is an anabolic process that stores energy, while respiration is a catabolic process that releases energy.
The reactants of one process are the products of the other, creating a cycle.
They cannot produce their own food and will eventually die.
The organism dies due to a lack of energy.
Plants balance these processes based on the availability of light and their energy needs.
During the day, photosynthesis usually outweighs respiration, leading to a net production of oxygen and glucose.
It is a simple sugar that is easily broken down to release energy.
Higher temperatures generally increase the rate of respiration up to an optimal point.
It allowed for the evolution of larger, more complex multicellular organisms that require more energy.
Photosynthesis creates food, and respiration provides the energy from that food.
The presence or absence of oxygen and the organism's metabolic machinery.

SECTION C: SHORT ANSWER QUESTIONS (2 Marks)

Respiration is called a biochemical process because it involves a series of chemical reactions that occur inside the living cells of an organism. These reactions break down organic molecules like glucose to produce energy for life functions.
Aerobic respiration releases a large amount of energy (around 38 ATP from one glucose molecule) because glucose is completely broken down. Anaerobic respiration releases a much smaller amount of energy (only 2 ATP) because the breakdown of glucose is incomplete.
Aerobic respiration requires a continuous supply of oxygen and the presence of glucose. It also needs specific enzymes and occurs within the mitochondria of the cell to proceed efficiently.
During alcoholic fermentation, which occurs in the absence of oxygen, yeast breaks down glucose into ethanol and carbon dioxide. This process releases a small amount of energy, which the yeast uses to survive.
In waterlogged soil, the air spaces are filled with water, depriving the roots of oxygen. To survive, the root cells switch to anaerobic respiration, breaking down glucose without oxygen to produce a small amount of ATP.
The reactants of photosynthesis are carbon dioxide and water, which are low-energy molecules. The reactants of respiration are glucose and oxygen, which are high-energy molecules.
ATP is called the energy currency because it is the principal molecule for storing and transferring energy in cells. Just as currency is used for economic transactions, ATP is used for energy-requiring processes in the cell, "paying" for cellular work.
During respiration, an organism takes in oxygen from the environment and releases carbon dioxide as a waste product. This gas exchange occurs in all living cells as they break down glucose for energy.
Photosynthesis only occurs during the daytime when light is available. In contrast, respiration is a continuous process that happens 24/7, both day and night, as living cells constantly require energy.
Photosynthesis is an anabolic process because it builds up complex organic molecules (glucose) from simpler inorganic ones (CO₂ and water). This process requires an input of energy (light) to create chemical bonds.
Respiration is a catabolic process because it breaks down complex organic molecules (glucose) into simpler ones (CO₂ and water). This breakdown releases the chemical energy stored in the glucose bonds.
Photosynthesis and respiration are complementary because the products of one process are the reactants for the other. Photosynthesis produces glucose and oxygen, which are then used in respiration. Respiration produces carbon dioxide and water, which are used in photosynthesis.
In photosynthesis, light energy is converted into chemical energy and stored in the bonds of glucose. In respiration, the chemical energy stored in glucose is released and converted into a usable form of chemical energy, ATP.
During aerobic respiration, glucose is completely broken down in the presence of oxygen. This multi-step process occurs mainly in the mitochondria and results in the production of carbon dioxide, water, and a large amount of ATP.
Anaerobic respiration produces less energy because the breakdown of glucose is incomplete. Without oxygen to act as the final electron acceptor, the process cannot extract all the energy stored in the glucose molecule, leaving much of it in the waste products like ethanol or lactic acid.
The products of aerobic respiration are carbon dioxide, water, and a large amount of ATP. The products of anaerobic respiration (in yeast) are ethanol, carbon dioxide, and a small amount of ATP.
Oxygen is crucial for aerobic respiration as it acts as the final electron acceptor in the electron transport chain. This role allows for the complete breakdown of glucose and the maximum release of energy in the form of ATP.
Respiration occurs continuously because all living cells require a constant supply of energy to perform their vital functions, such as maintenance, repair, growth, and movement. ATP, the product of respiration, is constantly being used and must be replenished.
Photosynthesis occurs only in cells containing chlorophyll, primarily in the chloroplasts of plant leaves. Respiration occurs in the cytoplasm and mitochondria of every living cell in an organism, including plants, animals, and microbes.
Respiration is vital for living organisms because it provides the energy necessary for all life processes. This energy, in the form of ATP, powers everything from muscle contraction and nerve impulses to growth and reproduction.
Yeast performs fermentation in an anaerobic environment (without oxygen). It breaks down sugars like glucose into ethanol and carbon dioxide, releasing a small amount of energy (ATP) for its own survival. This process is utilized in baking and brewing.
Complete breakdown of glucose, as seen in aerobic respiration, oxidizes the glucose molecule entirely to CO₂ and H₂O, releasing a large amount of energy. Incomplete breakdown, as in anaerobic respiration, only partially breaks down glucose, yielding less energy and producing organic byproducts like ethanol.
Anaerobic respiration is favored in conditions where oxygen is scarce or absent. This includes environments like waterlogged soils, the deep tissues of animals during strenuous exercise, or in microorganisms like yeast used in industrial fermentation.
Plants need photosynthesis to create their own food (glucose) by capturing light energy. They need respiration to break down that glucose to release the stored chemical energy in a usable form (ATP) to power their cellular activities, growth, and metabolism.
In photosynthesis, the gas exchange involves taking in carbon dioxide and releasing oxygen. In respiration, the exchange is the opposite: taking in oxygen and releasing carbon dioxide.
Chlorophyll is essential for photosynthesis as it captures light energy, but it plays no role in respiration. Respiration is a separate process that occurs in the mitochondria and cytoplasm, independent of chlorophyll.
The exothermic nature of respiration means it releases energy. This released energy is not all lost as heat; a significant portion is efficiently captured in the chemical bonds of ATP, which then powers cellular work.
Photosynthesis is an energy-storing process that requires an input of light energy. Respiration is an energy-releasing process that breaks down stored chemical energy.
Aerobic respiration is more efficient because the complete oxidation of glucose to CO₂ and water releases the maximum possible energy from the molecule. The use of oxygen as a final electron acceptor is key to this high energy yield.
Respiration is a general term for the metabolic processes that produce ATP. Fermentation is a specific type of anaerobic respiration that does not use an electron transport chain, resulting in a much lower energy yield and producing characteristic byproducts like ethanol or lactic acid.
The primary substrate for respiration is glucose, a high-energy organic molecule. The substrates for photosynthesis are carbon dioxide and water, which are low-energy inorganic molecules.
Photosynthesis occurs in the chloroplasts of plant cells. Respiration begins in the cytoplasm and is completed in the mitochondria of all eukaryotic cells.
Both processes are essential for plant survival because they are interlinked. Photosynthesis provides the fuel (glucose), and respiration burns that fuel to provide the energy (ATP) needed for the plant to live, grow, and reproduce.
Photosynthesis requires light, moderate temperatures, and sufficient CO₂ and water. Respiration occurs under a wider range of conditions but is also affected by temperature; it does not require light.
In plants, glucose is produced during the day via photosynthesis. This glucose is then consumed continuously by respiration to provide a steady supply of energy for the plant's metabolic needs, both day and night.
Respiration breaks the chemical bonds in glucose in a controlled, step-by-step process. The energy released from these bonds is captured and stored in the high-energy phosphate bonds of ATP molecules, which can then be easily used by the cell.
Photosynthesis consumes CO₂ and releases oxygen. Respiration consumes oxygen and releases CO₂.
Photosynthesis consumes carbon dioxide from the atmosphere to build glucose. Respiration releases carbon dioxide as a waste product from the breakdown of glucose.
Respiration is an exothermic process, meaning it releases heat. This heat helps warm-blooded animals maintain a constant internal body temperature, which is essential for optimal enzyme function.
Aerobic pathways are more complex, involving glycolysis, the Krebs cycle, and the electron transport chain to maximize energy extraction. Anaerobic pathways are simpler, consisting mainly of glycolysis followed by fermentation steps to regenerate NAD+.
Plants balance energy by regulating the rates of photosynthesis and respiration. During the day, photosynthesis rates are high, producing more glucose than is immediately needed for respiration, allowing for storage. At night, the plant relies on these stored reserves for energy through respiration.
The ATP produced during respiration provides the energy for all aspects of plant growth and development. This includes cell division, nutrient uptake from the soil, and the synthesis of proteins and other essential molecules.
Aerobic respiration is highly efficient, capturing about 38-40% of the energy from glucose in ATP. Photosynthesis is less efficient in terms of overall energy capture from sunlight, but it is the ultimate source of energy for most ecosystems.
Continuous ATP production is crucial because cells do not store large amounts of ATP. It is constantly being used to power cellular activities, so it must be continuously generated through respiration to meet the cell's immediate energy demands.
Waterlogged conditions starve plant roots of oxygen, forcing them into inefficient anaerobic respiration. This leads to a severe energy deficit and a buildup of toxic ethanol, which can damage root cells and eventually kill the plant.
The evolution of aerobic respiration was a major turning point in the history of life. The high energy yield allowed for the development of complex, multicellular organisms with specialized tissues and active lifestyles, which would not be possible with the low energy output of anaerobic processes.
Breathing (or gas exchange) is the physical process of bringing oxygen into the body and expelling carbon dioxide. Cellular respiration is the biochemical process that occurs inside cells to use that oxygen to break down glucose and produce ATP.
Some simple organisms, like certain bacteria and yeasts, can survive without oxygen because they have metabolic pathways for anaerobic respiration or fermentation. This allows them to generate enough ATP to meet their lower energy demands in anaerobic environments.
Anaerobic processes are used industrially for brewing (ethanol fermentation) and making yogurt and cheese (lactic acid fermentation). Aerobic processes are fundamental to wastewater treatment, where microbes are used to break down organic waste.
Environmental factors like temperature, and the availability of oxygen and glucose, significantly affect the rate of respiration. Generally, the rate increases with temperature to an optimum, and the presence of oxygen allows for the much more efficient aerobic pathway.

SECTION D: LONG ANSWER QUESTIONS (3 Marks)

Respiration is a fundamental biochemical process where living organisms break down organic substances, primarily glucose, to release energy. This energy is captured in the form of ATP and is essential for all life activities like growth, movement, and maintaining body temperature. The overall word equation is: Glucose + Oxygen → Carbon Dioxide + Water + Energy. It is called an exothermic process because it releases energy into the surroundings, partly as heat and partly as usable chemical energy in ATP.
Aerobic and anaerobic respiration are two types of cellular respiration. Aerobic respiration requires oxygen, completely breaks down glucose, and yields a large amount of energy (approx. 38 ATP). Its equation is Glucose + Oxygen → CO₂ + H₂O + Energy. It is performed by most plants and animals. In contrast, anaerobic respiration occurs without oxygen, incompletely breaks down glucose, and yields very little energy (2 ATP). In yeast, the equation is Glucose → Ethanol + CO₂ + Energy. It is performed by organisms like yeast and some bacteria, and in animal muscle cells during intense exercise.
Photosynthesis and respiration are complementary processes vital for plant life. Photosynthesis uses light energy, CO₂, and water to build glucose and release oxygen. Respiration uses that glucose and oxygen to release chemical energy (ATP), CO₂, and water. They are a perfect cycle: the products of photosynthesis are the reactants for respiration, and vice-versa. Both are essential because photosynthesis provides the food/fuel for the plant, while respiration unlocks the energy from that fuel, allowing the plant to power its growth and metabolism day and night.
Alcoholic fermentation is a type of anaerobic respiration carried out by organisms like yeast in the absence of oxygen. During this process, glucose is broken down into ethanol and carbon dioxide, releasing a small amount of energy (2 ATP). The word equation is Glucose → Ethanol + Carbon Dioxide + Energy. This process is commercially important; the carbon dioxide produced makes bread rise, and the ethanol produced is the basis for alcoholic beverages like beer and wine.
Photosynthesis and respiration differ in several key ways.
- Nature: Photosynthesis is an anabolic (building up) process, while respiration is a catabolic (breaking down) process.
- Energy: Photosynthesis stores light energy as chemical energy, whereas respiration releases stored chemical energy.
- Reactants/Products: Photosynthesis uses CO₂ and water to produce glucose and oxygen. Respiration uses glucose and oxygen to produce CO₂, water, and energy.
- Occurrence: Photosynthesis occurs only in cells with chlorophyll during the day. Respiration occurs in all living cells continuously, day and night.
When soil becomes waterlogged, the air spaces are filled with water, cutting off the oxygen supply to the plant roots. To survive, the root cells are forced to switch from efficient aerobic respiration to inefficient anaerobic respiration. This has severe consequences: the energy production drops dramatically, hindering nutrient uptake and root growth. Furthermore, the byproduct, ethanol, is toxic to the plant cells and its accumulation can lead to root death and ultimately the death of the plant.
ATP (Adenosine Triphosphate) is the universal energy currency of the cell. It is a small molecule that stores and transports chemical energy. During respiration, the energy released from the breakdown of glucose is used to add a phosphate group to ADP (Adenosine Diphosphate), forming ATP. This process "charges" the molecule. When the cell needs energy for any process, like muscle contraction or active transport, it breaks a phosphate bond in ATP, releasing the stored energy and converting it back to ADP.
Photosynthesis and respiration are central to energy transformation on Earth. In photosynthesis, plants capture light energy from the sun and convert it into chemical energy, storing it in the bonds of glucose molecules. This is the primary way energy enters most ecosystems. Respiration then performs the reverse transformation, releasing the chemical energy stored in glucose and converting it into a form usable by the cell (ATP) to power all life functions. This flow of energy from the sun to producers and then to consumers is fundamental to life.
Aerobic respiration is vastly more efficient than anaerobic respiration. It can generate up to 38 ATP molecules from a single glucose molecule, while anaerobic respiration only produces 2 ATP. This is because the complete oxidation of glucose in the presence of oxygen releases its full energy potential. Organisms use anaerobic respiration only as a survival mechanism when oxygen is not available, as it provides a small but immediate supply of ATP, which is better than none at all.
The gas exchange processes in photosynthesis and respiration are opposite and complementary, creating a balance in the atmosphere. During photosynthesis, plants consume large amounts of carbon dioxide from the atmosphere and release oxygen as a byproduct. During respiration, all organisms (including plants) consume oxygen and release carbon dioxide. This reciprocal exchange helps to maintain the relatively stable levels of oxygen and carbon dioxide in the atmosphere that are essential for life.
Respiration is called a catabolic process because it involves the breakdown (catabolism) of large, complex molecules (glucose) into smaller, simpler ones (CO₂ and H₂O), releasing energy in the process. Conversely, photosynthesis is an anabolic process because it involves building (anabolism) large, complex molecules (glucose) from small, simple ones (CO₂ and H₂O), which requires an input of energy. These opposing processes of building up and breaking down are central to a plant's metabolism, allowing it to create and utilize energy reserves.
Respiration is a continuous process because organisms need a constant supply of energy to stay alive, regardless of the time of day. In contrast, photosynthesis is intermittent, as it is entirely dependent on the availability of light. To manage their energy needs, plants produce an excess of glucose during the day through photosynthesis and store it as starch. At night, or during periods of low light, they break down these stored reserves through respiration to ensure a continuous energy supply.
The breakdown of glucose yields vastly different outcomes depending on the presence of oxygen. In aerobic conditions, glucose is completely oxidized to carbon dioxide and water, releasing a large amount of energy (up to 38 ATP). In anaerobic conditions, glucose is only partially broken down. In yeast, the products are ethanol and carbon dioxide, while in animal muscles, it is lactic acid. In both anaerobic cases, the energy released is very small (only 2 ATP) because most of the chemical energy remains locked in the organic byproducts.
Respiration is crucial as it provides the energy for all fundamental life processes. The ATP generated powers growth through cell division and synthesis of new materials. It enables movement, from muscle contractions in animals to internal movements within cells. Energy from respiration is also required for reproduction and for maintaining a stable internal environment, such as regulating body temperature in warm-blooded animals. Without a constant supply of energy from respiration, life would cease.
The type of respiration performed is primarily determined by the availability of oxygen. In oxygen-rich environments, most organisms will perform aerobic respiration due to its high efficiency. However, if oxygen becomes scarce, some organisms can switch to anaerobic respiration. For example, human muscle cells switch to lactic acid fermentation during intense exercise when oxygen delivery is insufficient. Similarly, yeast switches to alcoholic fermentation in anaerobic conditions, a process harnessed in baking and brewing. The consequence of this switch is a drastic reduction in energy production.
The evolution of aerobic respiration was a pivotal event in the history of life on Earth. Early life forms were anaerobic, limited by the small energy yield of their metabolism. Once photosynthesis evolved and oxygen began to accumulate in the atmosphere, organisms that developed the machinery for aerobic respiration gained a massive advantage. The huge increase in energy efficiency allowed for the evolution of larger, more complex, multicellular organisms with specialized tissues and active lifestyles, shaping the biodiversity we see today.
Photosynthesis and respiration are the two key processes that drive the oxygen-carbon dioxide cycle. Photosynthesis, carried out by plants, algae, and some bacteria, removes CO₂ from the atmosphere and releases O₂. Respiration, carried out by nearly all living organisms, consumes O₂ and releases CO₂. This global cycle is in a delicate balance, with the processes essentially reversing each other, maintaining the composition of the atmosphere and making life on Earth possible for aerobic organisms.
Plants expertly balance their energy budget throughout the day. During daylight hours, the rate of photosynthesis typically exceeds the rate of respiration. This means the plant produces more glucose and oxygen than it consumes, allowing it to store the excess glucose as starch for later use. At night, photosynthesis stops, and the plant relies entirely on respiration, breaking down the stored starch to provide the continuous supply of ATP needed to maintain its life functions until sunrise.
Fermentation is a crucial survival mechanism for organisms in anaerobic conditions. When oxygen is unavailable for aerobic respiration, the cell's primary pathway for making ATP (the electron transport chain) shuts down. Fermentation provides an alternative route to regenerate the NAD+ molecules needed for glycolysis to continue. By allowing glycolysis to proceed, the cell can continue to produce a small but vital amount of ATP, enabling the organism to survive short periods without oxygen.
Photosynthesis is confined to the chloroplasts, which are organelles found only in the green parts of plants (mainly leaves) because they contain the necessary chlorophyll pigment to capture light. In contrast, respiration occurs in all living cells of an organism. It starts in the cytoplasm (glycolysis) and is completed in the mitochondria. This is because every single cell, whether in a root, stem, or leaf, requires a constant supply of energy to live, and mitochondria are the powerhouses that provide this energy.
Understanding respiration has numerous practical applications. In medicine, it is key to understanding metabolic diseases and the effects of oxygen deprivation. In agriculture, knowledge of root respiration helps in developing better soil management and irrigation practices to prevent waterlogging and crop failure. Industrially, the anaerobic respiration of yeast (fermentation) is the basis of the multi-billion dollar baking and brewing industries, while aerobic respiration of microbes is used in bioremediation and wastewater treatment.
The study of respiration is fundamental to understanding energy flow in ecosystems. It explains how the chemical energy, initially captured from sunlight by producers (plants) through photosynthesis, is transferred through the food chain. Consumers (herbivores, carnivores) obtain this energy by eating other organisms and then release it through their own respiration to power their life activities. This flow of energy from producers to consumers, with energy being lost as heat at each respiratory step, defines the structure and function of all ecosystems.
Several factors can affect the rate of respiration. Temperature is a key factor; as temperature rises, the rate of respiration increases up to an optimal point, beyond which enzymes denature. The concentration of oxygen and glucose (the reactants) also influences the rate; more reactants can lead to a faster rate, up to a saturation point. These factors are critical for an organism's survival, as its ability to produce energy must match its metabolic demands, which can change with activity level and environmental conditions.
The exothermic nature of respiration, meaning it releases energy, is biochemically significant because this is the very energy that sustains life. Organisms have evolved highly efficient mechanisms, primarily the electron transport chain in mitochondria, to capture a large portion of this released energy. Instead of losing it all as heat, it is trapped in the high-energy bonds of ATP. This captured energy is then readily available to drive all other endothermic (energy-requiring) reactions in the cell, from synthesizing molecules to muscle movement.
Photosynthesis and respiration are completely interdependent and essential for maintaining life on a global scale. Photosynthesis, performed by producers, is the ultimate source of nearly all organic matter and oxygen on Earth. Respiration, performed by almost all organisms, is the process that releases the energy stored in that organic matter. A disruption in photosynthesis would eliminate the food and oxygen supply, while a disruption in respiration would halt the recycling of carbon and prevent organisms from accessing energy, leading to a collapse of the global ecosystem.

Respiration

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