AQA GCSE Biology Paper 1 – Complete
Revision Notes & Exam Practice (2025
Updated)
What does a nucleus do? - ANSW✔-It contains genetic material and controls the activities of the cell
What does cytoplasm do? - ANSW✔-It's a gel-like substance where most of the chemical reactions
happen. It contains enzymes that control these chemical reactions
What does a cell membrane do? - ANSW✔-It holds the cell together and controls what goes in and out
What do mitochondria do? - ANSW✔-These are where most of the reactions for aerobic respiration
occur. Respiration transfers energy that the cell needs to work
What do ribosomes do? - ANSW✔-This is where protein synthesis takes place - where proteins are
made in the cell
What do cell walls do? - ANSW✔-They are made of cellulose and they support and strengthen the cell
What does a vacuole do? - ANSW✔-It contains cell sap and helps maintain the shape of the cell
What do chloroplasts do? - ANSW✔-This is where photosynthesis occurs, which makes food for the
plant. They contain chlorophyll - a green pigment - which absorbs light needed for photosynthesis
,What do bacterial cells contain? - ANSW✔-Cytoplasm, cell membrane, cell wall, flagella, ribosomes,
mitochondria, slime capsule, plasmids (small rings of DNA) and a single circular strand of DNA that floats
freely in the cytoplasm
What do bacterial cells NOT contain? - ANSW✔-A nucleus
What is the equation for magnification? - ANSW✔-Image size divided by actual size
What is differentiation? - ANSW✔-The process by which a cell changes to become specialised for its
job
What are undifferentiated cells called? - ANSW✔-Stem cells
What are sperm cells specialised for and how are they specialised? - ANSW✔-Reproduction - they
transport the male DNA to the female DNA
-It has a flagella and a streamlined head to help it swim towards the egg
-There are lots of mitochondria in the cell to provide the energy needed
-It carries enzymes in its head to help digest through the egg cell membranes
What are nerve cells specialised for and how are they specialised? - ANSW✔-Rapid signalling - they
carry electrical signals from one part of the body to another
-They are long to cover more distance
-They have branched connections at their ends to connect to other nerve cells and form a network
throughout the body
What are muscle cells specialised for and how are they specialised? - ANSW✔-Contraction - they need
to contract quickly
-They are long so they have space to contract
-They contain lots of mitochondria to generate the energy needed for contraction
,What are root hair cells specialised for and how are they specialised? - ANSW✔-Absorbing water and
minerals
-They are cells on the surface of plant roots which grow into long hairs that stick out into the soil
-They have a large surface area for absorbing water and mineral ions from the soil
What are chromosomes? - ANSW✔-Coiled up lengths of DNA molecules that are found in the nuclei
What do multicellular organisms use mitosis for? - ANSW✔-To grow or replace cells that have been
damaged
What are stem cells? - ANSW✔-They are undifferentiated cells that divide to produce lots more
undifferentiated cells. They then differentiate into different types of cell
Where are stem cells found? - ANSW✔-In early human embryos or the bone marrow of adults
What do embryonic stem cells do? - ANSW✔-1) Used to replace faulty cells in sick people - insulin-
producing cells for diabetes and nerve cells for paralysed spinal injuries
2) Used to replace faulty blood cells
What is diffusion? - ANSW✔-Diffusion is the movement of particles from an area of high concentration
to an area of low concentration
Name the substances that can diffuse through cell membranes - ANSW✔-Glucose, water, oxygen and
amino acids
Name two substances that can't diffuse through cell membranes - ANSW✔-Protein and starch
What is osmosis? - ANSW✔-Osmosis is the passive movement of water molecules through a partially
permeable cell membrane from an area of high water concentration to an area of low water
concentration
, What are the two main differences between active transport and diffusion? - ANSW✔-Active transport
uses energy whereas diffusion doesn't. Active transport goes against the concentration gradient
whereas diffusion goes along it
Adaptations of Exchange Surfaces - ANSW✔-1) Large surface area - lots of substances can diffuse at
once
2) Lots of blood vessels - to get stuff into and out of the blood quickly
3) Thin membrane - short distance for substances to diffuse
4) Often ventilated - air moves in & out
Give two ways that the villi in the small intestine are adapted for absorbing digested food - ANSW✔-1)
A single layer of surface cells
2) A very good blood supply to assist quick absorption
Explain how the leaves are adapted to maximise the amount of carbon dioxide that gets into their cells -
ANSW✔-1) The exchange surface in a leaf is covered in stomata which the carbon dioxide diffuses
through
2) The leaf has a flattened shape which increases the area of its exchange surface, therefore it's more
effective
3) The walls of the cells inside the leaf act as another exchange surface
4) The air spaces inside the leaf increase the area of the exchange surface which increases the chance
for carbon dioxide to enter the cells
What affects the rate of diffusion? - ANSW✔-Concentration gradient - the steeper the gradient, the
faster the rate
Temperature - the higher the temperature, the faster the rate (the particles have more energy thus
move around faster)
Surface area - the larger it is, the faster the rate
Diffusion distance - the shorter the distance, the faster the rate
Examples of active transport - ANSW✔-Plants = Root hairs absorb minerals and water. Each branch of
a root will be covered in tiny hairs, therefore increasing the surface area for the absorption of minerals
Revision Notes & Exam Practice (2025
Updated)
What does a nucleus do? - ANSW✔-It contains genetic material and controls the activities of the cell
What does cytoplasm do? - ANSW✔-It's a gel-like substance where most of the chemical reactions
happen. It contains enzymes that control these chemical reactions
What does a cell membrane do? - ANSW✔-It holds the cell together and controls what goes in and out
What do mitochondria do? - ANSW✔-These are where most of the reactions for aerobic respiration
occur. Respiration transfers energy that the cell needs to work
What do ribosomes do? - ANSW✔-This is where protein synthesis takes place - where proteins are
made in the cell
What do cell walls do? - ANSW✔-They are made of cellulose and they support and strengthen the cell
What does a vacuole do? - ANSW✔-It contains cell sap and helps maintain the shape of the cell
What do chloroplasts do? - ANSW✔-This is where photosynthesis occurs, which makes food for the
plant. They contain chlorophyll - a green pigment - which absorbs light needed for photosynthesis
,What do bacterial cells contain? - ANSW✔-Cytoplasm, cell membrane, cell wall, flagella, ribosomes,
mitochondria, slime capsule, plasmids (small rings of DNA) and a single circular strand of DNA that floats
freely in the cytoplasm
What do bacterial cells NOT contain? - ANSW✔-A nucleus
What is the equation for magnification? - ANSW✔-Image size divided by actual size
What is differentiation? - ANSW✔-The process by which a cell changes to become specialised for its
job
What are undifferentiated cells called? - ANSW✔-Stem cells
What are sperm cells specialised for and how are they specialised? - ANSW✔-Reproduction - they
transport the male DNA to the female DNA
-It has a flagella and a streamlined head to help it swim towards the egg
-There are lots of mitochondria in the cell to provide the energy needed
-It carries enzymes in its head to help digest through the egg cell membranes
What are nerve cells specialised for and how are they specialised? - ANSW✔-Rapid signalling - they
carry electrical signals from one part of the body to another
-They are long to cover more distance
-They have branched connections at their ends to connect to other nerve cells and form a network
throughout the body
What are muscle cells specialised for and how are they specialised? - ANSW✔-Contraction - they need
to contract quickly
-They are long so they have space to contract
-They contain lots of mitochondria to generate the energy needed for contraction
,What are root hair cells specialised for and how are they specialised? - ANSW✔-Absorbing water and
minerals
-They are cells on the surface of plant roots which grow into long hairs that stick out into the soil
-They have a large surface area for absorbing water and mineral ions from the soil
What are chromosomes? - ANSW✔-Coiled up lengths of DNA molecules that are found in the nuclei
What do multicellular organisms use mitosis for? - ANSW✔-To grow or replace cells that have been
damaged
What are stem cells? - ANSW✔-They are undifferentiated cells that divide to produce lots more
undifferentiated cells. They then differentiate into different types of cell
Where are stem cells found? - ANSW✔-In early human embryos or the bone marrow of adults
What do embryonic stem cells do? - ANSW✔-1) Used to replace faulty cells in sick people - insulin-
producing cells for diabetes and nerve cells for paralysed spinal injuries
2) Used to replace faulty blood cells
What is diffusion? - ANSW✔-Diffusion is the movement of particles from an area of high concentration
to an area of low concentration
Name the substances that can diffuse through cell membranes - ANSW✔-Glucose, water, oxygen and
amino acids
Name two substances that can't diffuse through cell membranes - ANSW✔-Protein and starch
What is osmosis? - ANSW✔-Osmosis is the passive movement of water molecules through a partially
permeable cell membrane from an area of high water concentration to an area of low water
concentration
, What are the two main differences between active transport and diffusion? - ANSW✔-Active transport
uses energy whereas diffusion doesn't. Active transport goes against the concentration gradient
whereas diffusion goes along it
Adaptations of Exchange Surfaces - ANSW✔-1) Large surface area - lots of substances can diffuse at
once
2) Lots of blood vessels - to get stuff into and out of the blood quickly
3) Thin membrane - short distance for substances to diffuse
4) Often ventilated - air moves in & out
Give two ways that the villi in the small intestine are adapted for absorbing digested food - ANSW✔-1)
A single layer of surface cells
2) A very good blood supply to assist quick absorption
Explain how the leaves are adapted to maximise the amount of carbon dioxide that gets into their cells -
ANSW✔-1) The exchange surface in a leaf is covered in stomata which the carbon dioxide diffuses
through
2) The leaf has a flattened shape which increases the area of its exchange surface, therefore it's more
effective
3) The walls of the cells inside the leaf act as another exchange surface
4) The air spaces inside the leaf increase the area of the exchange surface which increases the chance
for carbon dioxide to enter the cells
What affects the rate of diffusion? - ANSW✔-Concentration gradient - the steeper the gradient, the
faster the rate
Temperature - the higher the temperature, the faster the rate (the particles have more energy thus
move around faster)
Surface area - the larger it is, the faster the rate
Diffusion distance - the shorter the distance, the faster the rate
Examples of active transport - ANSW✔-Plants = Root hairs absorb minerals and water. Each branch of
a root will be covered in tiny hairs, therefore increasing the surface area for the absorption of minerals
