A+ Level AQA Biology questions and
answers (100% correct well researched
and detailed answers)
Describe the nucleus.
Outline the functions. - answersA large organelle surrounded by a nuclear envelope
which contains many pores. The nucleus contains chromosomes.
The nucleus controls the cell's activities by controlling the transcription of DNA. The
pores allow substances to move between the nucleus and the cytoplasm. The nucleolus
makes ribosomes.
Describe mitochondrion.
Outline the functions. - answersThey are usually oval-shaped and have a double
membrane. The inner membrane is folded to form structures called cristae. Inside is the
matrix, which contains enzymes involved in respiration.
The site of aerobic respiration, where ATP is produced. They are found in large
numbers in cells that are very active and require a lot of energy.
Describe the structure of chloroplasts.
Outline the functions. - answersA small, flattened structure found in plant and algal
cells. It is surrounded by a double membrane, and has membrane inside called
thylakoid membranes. They are stacked up in some parts to form grana. Grana are
linked together by lamellae.
The site where photosynthesis takes place. Some parts happen in the grana, and other
parts happen in the stroma. (thick fluid found in chloroplasts)
Describe the structure of the Golgi apparatus.
Outline the functions. - answersA group of fluid-filled, membrane-bound, flattened sacs.
Vesicles are often seen at the edges of the sacs.
It processes and packages new lipids and proteins. It also makes lysosomes.
Describe the structure of a Golgi vesicle.
Outline the functions. - answersA small fluid-filled sac in the cytoplasm, surrounded by a
membrane, and produced by the Golgi apparatus.
Stores lipids and proteins made by the Golgi apparatus and transports them out of the
cell via the cell surface membrane.
Describe the structure of a lysosome.
,Outline the functions. - answersA round organelle surrounded by a membrane, with no
clear internal structure. It's a type of Golgi vesicle.
Contains digestive enzymes called lysozymes, that are kept separate from the
cytoplasm by the membrane. They can be used to digest invading cells or the break
down worn out components of the cell.
Describe the structure of a ribosome.
Outline the functions. - answersA very small organelle that either floats free in the
cytoplasm or is attached to the rough endoplasmic reticulum. It is made up of proteins
and RNA, and is not surrounded by a membrane.
It is the site where proteins are made.
Describe the structure of the rough endoplasmic reticulum. (RER)
Outline the functions. - answersA system of membranes enclosing a fluid-filled space.
The surface is covered with ribosomes.
They fold and process proteins that have been made at the ribosomes.
Describe the structure of the smooth endoplasmic reticulum. (SER)
Outline the functions. - answersA system of membranes enclosing a fluid-filled space.
The surface is completely smooth.
Synthesises and processes lipids.
Describe the structure of the cell wall.
Outline the functions. - answersA rigid structure that surrounds cells in plants, algae and
fungi. In plants and algae its mainly made from cellulose, but it in fungi it is made of
chitin.
It supports the cell and prevents them from changing shape.
Describe the structure of the cell vacuole.
Outline the functions. - answersA membrane-bound organelle found in the cytoplasm of
plant cells. It contains cell-sap, a weak solution of sugar and salts. The surrounding
membrane is called the tonoplast.
Helps to maintain pressure and rigidity inside the cell. This stops the plants wilting. It is
also involved in the isolation of unwanted chemicals inside the cell.
How are epithelial cells in the small intestine specialised to absorb food efficiently? -
answers1)The intestine walls have lots of villi, which increase surface area for
absorption
2)The epithelial cells on the surface of the villi have folds in their cell-surface membrane
called micro-villi, increasing SA even more.
, 3)They have lots of mitochondria to provide energy.
What are specialised cells grouped together to form? - answersTissues
What is a tissue? - answersA group of cells working together to perform a particular
function. Different tissues work together to form organs, organs make up an organ
system.
What are cell-surface membranes? - answersA barrier between the cell and its
environment
What is the role of a cell-surface membrane? - answersTo control which substances
leave and enter the cell by being partially permeable
How can substances move across the cell-surface membrane? - answersBy osmosis,
diffusion and active transport
What model is used to describe cell membranes? - answersThe fluid mosaic model
What is the basic structure of most cell membranes? - answersLipids, proteins and
carbohydrates
How thick is the phospholipid-bilayer? - answersAbout 7mm
Why is the membrane described as having a fluid mosaic structure? - answersBecause
it is a flexible structure, as the phospholipids move relative to one another so the
membrane can change shape. There are also various proteins embedded in it, of all
shapes and sizes, like tiles in a mosaic.
Name the other components in the continuous bilayer - answersCholesterol molecules,
channel proteins, carrier proteins, receptor proteins, (glyco)lipids, (glyco)proteins
Explain the roles of the different types of proteins present in the phospholipid bilayer -
answersIntrinsic channel proteins which form water-filled tubes to allow water soluble
ions to diffuse across the membrane.
Intrinsic carrier proteins that bind to ions or molecules like glucose and amino acids, and
change shape in order to move these molecules across the membrane.
Extrinsic receptor proteins on the surface which allow the cell to detect chemicals
released from other cells. The chemicals signal a cell response in some way.
Some of the proteins will have a short polysaccharide attached, which are
glycoproteins.
answers (100% correct well researched
and detailed answers)
Describe the nucleus.
Outline the functions. - answersA large organelle surrounded by a nuclear envelope
which contains many pores. The nucleus contains chromosomes.
The nucleus controls the cell's activities by controlling the transcription of DNA. The
pores allow substances to move between the nucleus and the cytoplasm. The nucleolus
makes ribosomes.
Describe mitochondrion.
Outline the functions. - answersThey are usually oval-shaped and have a double
membrane. The inner membrane is folded to form structures called cristae. Inside is the
matrix, which contains enzymes involved in respiration.
The site of aerobic respiration, where ATP is produced. They are found in large
numbers in cells that are very active and require a lot of energy.
Describe the structure of chloroplasts.
Outline the functions. - answersA small, flattened structure found in plant and algal
cells. It is surrounded by a double membrane, and has membrane inside called
thylakoid membranes. They are stacked up in some parts to form grana. Grana are
linked together by lamellae.
The site where photosynthesis takes place. Some parts happen in the grana, and other
parts happen in the stroma. (thick fluid found in chloroplasts)
Describe the structure of the Golgi apparatus.
Outline the functions. - answersA group of fluid-filled, membrane-bound, flattened sacs.
Vesicles are often seen at the edges of the sacs.
It processes and packages new lipids and proteins. It also makes lysosomes.
Describe the structure of a Golgi vesicle.
Outline the functions. - answersA small fluid-filled sac in the cytoplasm, surrounded by a
membrane, and produced by the Golgi apparatus.
Stores lipids and proteins made by the Golgi apparatus and transports them out of the
cell via the cell surface membrane.
Describe the structure of a lysosome.
,Outline the functions. - answersA round organelle surrounded by a membrane, with no
clear internal structure. It's a type of Golgi vesicle.
Contains digestive enzymes called lysozymes, that are kept separate from the
cytoplasm by the membrane. They can be used to digest invading cells or the break
down worn out components of the cell.
Describe the structure of a ribosome.
Outline the functions. - answersA very small organelle that either floats free in the
cytoplasm or is attached to the rough endoplasmic reticulum. It is made up of proteins
and RNA, and is not surrounded by a membrane.
It is the site where proteins are made.
Describe the structure of the rough endoplasmic reticulum. (RER)
Outline the functions. - answersA system of membranes enclosing a fluid-filled space.
The surface is covered with ribosomes.
They fold and process proteins that have been made at the ribosomes.
Describe the structure of the smooth endoplasmic reticulum. (SER)
Outline the functions. - answersA system of membranes enclosing a fluid-filled space.
The surface is completely smooth.
Synthesises and processes lipids.
Describe the structure of the cell wall.
Outline the functions. - answersA rigid structure that surrounds cells in plants, algae and
fungi. In plants and algae its mainly made from cellulose, but it in fungi it is made of
chitin.
It supports the cell and prevents them from changing shape.
Describe the structure of the cell vacuole.
Outline the functions. - answersA membrane-bound organelle found in the cytoplasm of
plant cells. It contains cell-sap, a weak solution of sugar and salts. The surrounding
membrane is called the tonoplast.
Helps to maintain pressure and rigidity inside the cell. This stops the plants wilting. It is
also involved in the isolation of unwanted chemicals inside the cell.
How are epithelial cells in the small intestine specialised to absorb food efficiently? -
answers1)The intestine walls have lots of villi, which increase surface area for
absorption
2)The epithelial cells on the surface of the villi have folds in their cell-surface membrane
called micro-villi, increasing SA even more.
, 3)They have lots of mitochondria to provide energy.
What are specialised cells grouped together to form? - answersTissues
What is a tissue? - answersA group of cells working together to perform a particular
function. Different tissues work together to form organs, organs make up an organ
system.
What are cell-surface membranes? - answersA barrier between the cell and its
environment
What is the role of a cell-surface membrane? - answersTo control which substances
leave and enter the cell by being partially permeable
How can substances move across the cell-surface membrane? - answersBy osmosis,
diffusion and active transport
What model is used to describe cell membranes? - answersThe fluid mosaic model
What is the basic structure of most cell membranes? - answersLipids, proteins and
carbohydrates
How thick is the phospholipid-bilayer? - answersAbout 7mm
Why is the membrane described as having a fluid mosaic structure? - answersBecause
it is a flexible structure, as the phospholipids move relative to one another so the
membrane can change shape. There are also various proteins embedded in it, of all
shapes and sizes, like tiles in a mosaic.
Name the other components in the continuous bilayer - answersCholesterol molecules,
channel proteins, carrier proteins, receptor proteins, (glyco)lipids, (glyco)proteins
Explain the roles of the different types of proteins present in the phospholipid bilayer -
answersIntrinsic channel proteins which form water-filled tubes to allow water soluble
ions to diffuse across the membrane.
Intrinsic carrier proteins that bind to ions or molecules like glucose and amino acids, and
change shape in order to move these molecules across the membrane.
Extrinsic receptor proteins on the surface which allow the cell to detect chemicals
released from other cells. The chemicals signal a cell response in some way.
Some of the proteins will have a short polysaccharide attached, which are
glycoproteins.
