IGCSE BIOLOGY EXAM 2025/2026
QUESTIONS AND ANSWERS 100% PASS
What does an animal cell consist of? - ANS Cell membrane, cytoplasm, mitochondria, nucleus
What does a plant cell consist of? - ANS Permanent vacuole, cell membrane, cell wall,
mitochondria, chloroplasts which are full of chlorophyll, cytoplasm, nucleus
What is their role of the nucleus? - ANS Controls the activity of the cells
What is the role of the cell membrane? - ANS Selectively permeable membrane which
controls the substances passing in and out of the cell
What is the role of mitochondria? - ANS Carry out some of the reactions of respiration to
release energy that the cell can use
What is the role of cytoplasm? - ANS Complex material made of many different structures
where all the chemical reactions take place
What is the role of the cell wall? - ANS Made of carbohydrate called cellulose which is a
tough material that helps the cell keep its shape,it is freely permeable
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,What is the role of chloroplasts? - ANS These contain chlorophyll and are green. The
chloroplasts absorb light energy to make food in the process of photosynthesis
What is the role of the vacuole? - ANS This is a permanent feature of the cell and is filled
with cell sap which is a store of dissolved sugars, mineral ions and other solutes
What is a catalyst and state the link between a catalyst and enzyme - ANS An enzyme is a
biological catalyst which means that it speeds up a reaction without being used up itself
How are the activities of a cell controlled? - ANS The nucleus contains genes, which control
the production of enzymes, which catalyst reactions in the cytoplasm
What is a metabolic reaction? - ANS A chemical reaction taken place inside a cell
Describe th process of enzyme 'lock and key' action - ANS 1. The substrate enters the
enzymes active site as it's active site is complimentary to the enzymes forming an enzyme
substrate complex
2. The reaction takes place and products are formed which leave the active site
Name one factor which affects enzymes - ANS Temperature: in the human body work best at
37C which is their optimum temperature. After this point the enzymes departure as the active
site changes shape. Before this point, as the temperature rises, so does the rate of reaction as it
will give the molecules of molecules of enzyme and substrate more energy, so they will collide
more frequently
Describe an investigation which shows the effect of temperature on enzymes - ANS Starch
and amylase:
C--> change the temperature of each solution of amylase and starch
O--> Use the same amount of starch and amylase in each solution and keep them in the water
baths for the same amount of time
R--> Repeat the tests for each temperature
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,M-->Use iodine to test for starch once you've placed the solution on a spotting tile. Time in
minutes and when iodine has changed colour from black/brown- yellow no more starch is
present
S--> Keep the concentration the same so the same amount of amylase and starch in each test
tube and the length of time in the water bath.
How do cells get energy and what can this energy be used for? - ANS Get energy through the
process of respiration and energy can be used to contract muscle cells to produce movement,
for active transport of ions and minerals, building large molecules such as proteins and cell
division and also release glucose in small amounts when aerobic
What is the word and symbol equation for aerobic respiration? - ANS Glucose + Oxygen -->
Carbon Dioxide + Water (+ Energy)
C6H12O6 + 6O2 --> 6CO2 + 6H2O (+ Energy)
What is anaerobic respiration and how does it differ from aerobic respiration? -
ANS Anaeobic respiration is when cells respite without the use of oxygen. Unlike aerobic
respiration glucose is not completely broken down and less energy is released.
Give two examples where cells respite anaerobically - ANS In yeast and muscle cells
State the word and symbol equation which occurs when yeast resources anaerobically -
ANS Glucose --> Ethanol + Carbon Dioxide (+ Some energy)
C6H12O6 --> 2C2H5OH + 2CO2 (+Some Energy)
State the word and symbol equation which occurs when muscle cells respite anaerobically -
ANS Glucose --> Ethanol (+ Some energy)
C6H12O6 --> 2C3H6O3 (+Some Energy)
What is oxygen debt? - ANS The volume of oxygen needed to completely oxidize the lactic
acid that builds up in the body during anaerobic respiration
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, Describe the term 'Diffusion' - ANS Diffusion is the movement of substances (ions and
molecules) from a high concentration to a low concentration (down the concentration gradient)
with the help of kinetic energy of the particles.
What can speed up the rate of diffusion? - ANS A higher concentration gradient
Higher temperature which means that the particles have more kinetic energy
Distance is decreased
Surface area increased
Describe the term 'active transport' - ANS Active transport is when substance move from a
high concentration to a low concentration (up the concentration gradient) with the use of ATP
from respiration.
The leaf: describe what happens with carbon dioxide and oxygen when a leaf cell is
photosynthesising - ANS The concentration of CO2 is greater outside the leaf so diffuses into
the cell to be used for photosynthesis whilst oxygen in the leaf is more concentrated so diffuses
out of the leaf cell
Describe the term 'osmosis' - ANS Osmosis is the diffusion of water molecules from high
water potential to a low water potential through a partially permeable membrane.
Give an example where osmosis occurs - ANS In plant roots
Describe an experiment to investigate diffusion - ANS Demonstration of diffusion in a jelly:
Using agar blocks dyed with potassium Permanganate and dilute hydrochloric acid in a breaker.
Agar jelly has the consistency similar to the cytoplasm of a cell which means that it has a high
water content so it can show how substances diffuse through a cell. When hydrochloric acid
comes into contact with potassium permanganate, the purple colour.
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
QUESTIONS AND ANSWERS 100% PASS
What does an animal cell consist of? - ANS Cell membrane, cytoplasm, mitochondria, nucleus
What does a plant cell consist of? - ANS Permanent vacuole, cell membrane, cell wall,
mitochondria, chloroplasts which are full of chlorophyll, cytoplasm, nucleus
What is their role of the nucleus? - ANS Controls the activity of the cells
What is the role of the cell membrane? - ANS Selectively permeable membrane which
controls the substances passing in and out of the cell
What is the role of mitochondria? - ANS Carry out some of the reactions of respiration to
release energy that the cell can use
What is the role of cytoplasm? - ANS Complex material made of many different structures
where all the chemical reactions take place
What is the role of the cell wall? - ANS Made of carbohydrate called cellulose which is a
tough material that helps the cell keep its shape,it is freely permeable
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,What is the role of chloroplasts? - ANS These contain chlorophyll and are green. The
chloroplasts absorb light energy to make food in the process of photosynthesis
What is the role of the vacuole? - ANS This is a permanent feature of the cell and is filled
with cell sap which is a store of dissolved sugars, mineral ions and other solutes
What is a catalyst and state the link between a catalyst and enzyme - ANS An enzyme is a
biological catalyst which means that it speeds up a reaction without being used up itself
How are the activities of a cell controlled? - ANS The nucleus contains genes, which control
the production of enzymes, which catalyst reactions in the cytoplasm
What is a metabolic reaction? - ANS A chemical reaction taken place inside a cell
Describe th process of enzyme 'lock and key' action - ANS 1. The substrate enters the
enzymes active site as it's active site is complimentary to the enzymes forming an enzyme
substrate complex
2. The reaction takes place and products are formed which leave the active site
Name one factor which affects enzymes - ANS Temperature: in the human body work best at
37C which is their optimum temperature. After this point the enzymes departure as the active
site changes shape. Before this point, as the temperature rises, so does the rate of reaction as it
will give the molecules of molecules of enzyme and substrate more energy, so they will collide
more frequently
Describe an investigation which shows the effect of temperature on enzymes - ANS Starch
and amylase:
C--> change the temperature of each solution of amylase and starch
O--> Use the same amount of starch and amylase in each solution and keep them in the water
baths for the same amount of time
R--> Repeat the tests for each temperature
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,M-->Use iodine to test for starch once you've placed the solution on a spotting tile. Time in
minutes and when iodine has changed colour from black/brown- yellow no more starch is
present
S--> Keep the concentration the same so the same amount of amylase and starch in each test
tube and the length of time in the water bath.
How do cells get energy and what can this energy be used for? - ANS Get energy through the
process of respiration and energy can be used to contract muscle cells to produce movement,
for active transport of ions and minerals, building large molecules such as proteins and cell
division and also release glucose in small amounts when aerobic
What is the word and symbol equation for aerobic respiration? - ANS Glucose + Oxygen -->
Carbon Dioxide + Water (+ Energy)
C6H12O6 + 6O2 --> 6CO2 + 6H2O (+ Energy)
What is anaerobic respiration and how does it differ from aerobic respiration? -
ANS Anaeobic respiration is when cells respite without the use of oxygen. Unlike aerobic
respiration glucose is not completely broken down and less energy is released.
Give two examples where cells respite anaerobically - ANS In yeast and muscle cells
State the word and symbol equation which occurs when yeast resources anaerobically -
ANS Glucose --> Ethanol + Carbon Dioxide (+ Some energy)
C6H12O6 --> 2C2H5OH + 2CO2 (+Some Energy)
State the word and symbol equation which occurs when muscle cells respite anaerobically -
ANS Glucose --> Ethanol (+ Some energy)
C6H12O6 --> 2C3H6O3 (+Some Energy)
What is oxygen debt? - ANS The volume of oxygen needed to completely oxidize the lactic
acid that builds up in the body during anaerobic respiration
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, Describe the term 'Diffusion' - ANS Diffusion is the movement of substances (ions and
molecules) from a high concentration to a low concentration (down the concentration gradient)
with the help of kinetic energy of the particles.
What can speed up the rate of diffusion? - ANS A higher concentration gradient
Higher temperature which means that the particles have more kinetic energy
Distance is decreased
Surface area increased
Describe the term 'active transport' - ANS Active transport is when substance move from a
high concentration to a low concentration (up the concentration gradient) with the use of ATP
from respiration.
The leaf: describe what happens with carbon dioxide and oxygen when a leaf cell is
photosynthesising - ANS The concentration of CO2 is greater outside the leaf so diffuses into
the cell to be used for photosynthesis whilst oxygen in the leaf is more concentrated so diffuses
out of the leaf cell
Describe the term 'osmosis' - ANS Osmosis is the diffusion of water molecules from high
water potential to a low water potential through a partially permeable membrane.
Give an example where osmosis occurs - ANS In plant roots
Describe an experiment to investigate diffusion - ANS Demonstration of diffusion in a jelly:
Using agar blocks dyed with potassium Permanganate and dilute hydrochloric acid in a breaker.
Agar jelly has the consistency similar to the cytoplasm of a cell which means that it has a high
water content so it can show how substances diffuse through a cell. When hydrochloric acid
comes into contact with potassium permanganate, the purple colour.
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
