AQA A-level Biology
A molecule has a better chance of passing through the phospholipid bilayer if... - ANSWER✅✅✅It is
a small molecule,
is not a charged molecule,
it is not an ion.
Those that pass through best are lipid soluble and hydrophobic molecules.
Describe an experiment you could carry out to test how temperature affects membrane permeability -
ANSWER✅✅✅+Cut beetroot into 5 identical pieces that have the same surface area, and rinse them
to remove any pigment that leaked while cutting.
+Add the pieces into 5 separate test tubes, each containing 5cm cubed of water.
+Place the test tubes in water baths of different temperatures for the same length of time.
+Remove the beetroot from the test tubes, leaving the coloured liquid.
+Using a colorimeter, measure how much of the light is absorbed when passing through the 5 liquids.
The higher the absorbance, the more pigment has been released, therefore the higher the membrane
permeability.
Describe and explain phospholipids - ANSWER✅✅✅The head is hydrophilic.
The tail is hydrophobic.
The molecules are arranged into a bilayer of polar molecules, with the heads pointing towards the
outside of the membrane, and the tails pointing inward.
Describe eukaryotic cells - ANSWER✅✅✅They are complex cells and include all animal and plant
cells, as well as all algae and fungi cells.
Describe mitochondrion.
Outline the functions. - ANSWER✅✅✅They 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.
AQA A-level Biology
,AQA A-level Biology
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 cell surface plasma membrane.
Outline the functions. - ANSWER✅✅✅It is found on the inside of cells that also have a cell wall
(plants), and is mainly made up of lipids and proteins.
It controls the movement of substances in and out of the cell. It also has receptor molecules on it, to
allow it to respond to chemicals like hormones.
Describe the experiment you could do to find the water potential of potato cells -
ANSWER✅✅✅+make different concentrations of sucrose solution in test tubes, making 15cm cubed
of each
+Cut potatoes into identically sized chips, about 1cm in diameter
+divide the chips into groups of three and measure the masses of each group.
+place one group into each sucrose solution
+leave the chips in the solutions for at least 20 minutes
+remove the chips and gently dab with paper towel
+weigh each group again and record the results
+calculate % mass change for each group
+Use the results to make a calibration curve
The potato chips will gain water in solutions with high water potential, and lose water in solutions with a
lower water potential.
Describe the nucleus.
Outline the functions. - ANSWER✅✅✅A large organelle surrounded by a nuclear envelope which
contains many pores. The nucleus contains chromosomes.
AQA A-level Biology
, AQA A-level Biology
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 the process of facilitated diffusion using carrier proteins - ANSWER✅✅✅A large molecule
attaches to the carrier protein, then the protein changes shape, which in turn releases the molecule on
the other side of the membrane.
Describe the process of facilitated diffusion using protein channels - ANSWER✅✅✅Channel proteins
form pores in the membrane for charged particles to diffuse through.
Different channel proteins diffuse different charged particles.
Describe the structure of a Golgi vesicle.
Outline the functions. - ANSWER✅✅✅A 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. - ANSWER✅✅✅A 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. - ANSWER✅✅✅A 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.
AQA A-level Biology
A molecule has a better chance of passing through the phospholipid bilayer if... - ANSWER✅✅✅It is
a small molecule,
is not a charged molecule,
it is not an ion.
Those that pass through best are lipid soluble and hydrophobic molecules.
Describe an experiment you could carry out to test how temperature affects membrane permeability -
ANSWER✅✅✅+Cut beetroot into 5 identical pieces that have the same surface area, and rinse them
to remove any pigment that leaked while cutting.
+Add the pieces into 5 separate test tubes, each containing 5cm cubed of water.
+Place the test tubes in water baths of different temperatures for the same length of time.
+Remove the beetroot from the test tubes, leaving the coloured liquid.
+Using a colorimeter, measure how much of the light is absorbed when passing through the 5 liquids.
The higher the absorbance, the more pigment has been released, therefore the higher the membrane
permeability.
Describe and explain phospholipids - ANSWER✅✅✅The head is hydrophilic.
The tail is hydrophobic.
The molecules are arranged into a bilayer of polar molecules, with the heads pointing towards the
outside of the membrane, and the tails pointing inward.
Describe eukaryotic cells - ANSWER✅✅✅They are complex cells and include all animal and plant
cells, as well as all algae and fungi cells.
Describe mitochondrion.
Outline the functions. - ANSWER✅✅✅They 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.
AQA A-level Biology
,AQA A-level Biology
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 cell surface plasma membrane.
Outline the functions. - ANSWER✅✅✅It is found on the inside of cells that also have a cell wall
(plants), and is mainly made up of lipids and proteins.
It controls the movement of substances in and out of the cell. It also has receptor molecules on it, to
allow it to respond to chemicals like hormones.
Describe the experiment you could do to find the water potential of potato cells -
ANSWER✅✅✅+make different concentrations of sucrose solution in test tubes, making 15cm cubed
of each
+Cut potatoes into identically sized chips, about 1cm in diameter
+divide the chips into groups of three and measure the masses of each group.
+place one group into each sucrose solution
+leave the chips in the solutions for at least 20 minutes
+remove the chips and gently dab with paper towel
+weigh each group again and record the results
+calculate % mass change for each group
+Use the results to make a calibration curve
The potato chips will gain water in solutions with high water potential, and lose water in solutions with a
lower water potential.
Describe the nucleus.
Outline the functions. - ANSWER✅✅✅A large organelle surrounded by a nuclear envelope which
contains many pores. The nucleus contains chromosomes.
AQA A-level Biology
, AQA A-level Biology
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 the process of facilitated diffusion using carrier proteins - ANSWER✅✅✅A large molecule
attaches to the carrier protein, then the protein changes shape, which in turn releases the molecule on
the other side of the membrane.
Describe the process of facilitated diffusion using protein channels - ANSWER✅✅✅Channel proteins
form pores in the membrane for charged particles to diffuse through.
Different channel proteins diffuse different charged particles.
Describe the structure of a Golgi vesicle.
Outline the functions. - ANSWER✅✅✅A 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. - ANSWER✅✅✅A 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. - ANSWER✅✅✅A 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.
AQA A-level Biology
