AQA A LEVEL BIOLOGY Paper 1 Questions With Accurate
Answers
What is the function of the cell membrane? - Accurate answers To control what enters and leaves
the cell, acts as a barrier between the cell and its environment.
What structural feature of the cell membrane allows substances to enter/leave? - Accurate answers
Partially permeable
What is the fluid mosaic model? - Accurate answers States that a membrane is a fluid structure
(because phospholipids are constantly moving) with a "mosaic" of various proteins embedded in it
Describe the structure and function of phospholipids. - Accurate answers Hydrophilic head and
hydrophobic tail, arranged in a bilayer (heads face outwards, tails face inwards). Lipid-soluble
substances only allowed to pass through.
What is the function of cholesterol in the CSM? - Accurate answers Make phospholipids pack more
closely together, restricting the movement of the phospholipids, making the membrane less fluid/more
rigid.
What is simple diffusion? - Accurate answers The (passive) movement of particles from an area of
high concentration to an area of low concentration.
What is facilitated diffusion? - Accurate answers The passive movement of a large/charged particle
down its concentration gradient through a carrier/channel protein.
What is the process of facilitated diffusion using a carrier protein? - Accurate answers Large
molecule binds to a carrier protein in membrane.
Protein changes shape.
Protein releases the large molecule on the opposite side of the membrane.
What is the process of facilitated diffusion using a channel protein? - Accurate answers Channel
proteins form pores in membrane.
Charged particles can diffuse down their concentration gradients to the opposite side of the membrane.
What are the factors affecting simple diffusion? - Accurate answers Concentration gradient,
thickness of exchange surface and surface area.
What are the factors affecting facilitated diffusion? - Accurate answers Number of transport
proteins and strength of gradient.
What is osmosis? - Accurate answers Diffusion of water through a partially permeable membrane
from an area of high water potential to an area of lower water potential.
What are the factors affecting osmosis? - Accurate answers Water potential gradient.
Thickness of exchange surface.
, Surface area of exchange surface.
Outline a method for RP3 (investigation of osmosis using potato chips). - Accurate answers
Produce a series of dilutions from 1M sucrose solution (of a variety of different concentrations, 0M,
0.2M, 0.4M, 0.6M, 0.8M, 1M).
Use a cork borer to cut potatoes into identically-sized chips.
Blot them dry with a paper towel and measure the mass of each using a mass balance.
Place one chip into each of the sucrose solutions.
Put the test tubes into a water bath at 30°C for 20 minutes.
Take them out and reweigh the mass of the chips.
Calculate the %change in mass for each chip.
What is active transport? - Accurate answers The active process of moving molecules from an area
of low concentration to an area of high concentration using ATP.
Name one type of carrier protein and describe how it works. - Accurate answers Co-transporters.
Bind two molecules at once.
The concentration gradient of one of the molecules is used to move the other molecule against its own
concentration gradient.
Give an example of co-transport in mammals. - Accurate answers Glucose/Na+ co-transport.
Na+ actively transported out of the ileum epithelial cells into the blood by the Na+/K+ pump. This
creates a concentration gradient, higher concentration of Na+ in lumen than inside cell.
Na+ Defuses into the epithelial cells from the lumen Na+/glucose co-transporter proteins.
Co-transporter carries glucose into the cell with the sodium so glucose concentration inside the cell
increases.
Glucose diffuses out of the cell, down its concentration gradient, through a protein channel, into the
blood, by facilitated diffusion.
What are the factors affecting active transport? - Accurate answers Speed of individual carrier
proteins.
Number of carrier proteins present.
Rate of respiration/availability of ATP.
3.2.1 Cell Structure - Accurate answers
Eukaryotic cells - Accurate answers Complex, include all animal and plant cells (& algal/fungal
cells).
Algal and fungal cells - Accurate answers Algal: same organelles as plant cells including cell wall
and chloroplasts.
Fungal: similar to plant cells but cell walls made of chitin and no chloroplasts.
Organelles in eukaryotic cells: - Accurate answers Membrane-bound compartments which
separate metabolic reactions within a cell.
Nucleus - Accurate answers Contains chromosomes which are made from protein bound linear
DNA.
Answers
What is the function of the cell membrane? - Accurate answers To control what enters and leaves
the cell, acts as a barrier between the cell and its environment.
What structural feature of the cell membrane allows substances to enter/leave? - Accurate answers
Partially permeable
What is the fluid mosaic model? - Accurate answers States that a membrane is a fluid structure
(because phospholipids are constantly moving) with a "mosaic" of various proteins embedded in it
Describe the structure and function of phospholipids. - Accurate answers Hydrophilic head and
hydrophobic tail, arranged in a bilayer (heads face outwards, tails face inwards). Lipid-soluble
substances only allowed to pass through.
What is the function of cholesterol in the CSM? - Accurate answers Make phospholipids pack more
closely together, restricting the movement of the phospholipids, making the membrane less fluid/more
rigid.
What is simple diffusion? - Accurate answers The (passive) movement of particles from an area of
high concentration to an area of low concentration.
What is facilitated diffusion? - Accurate answers The passive movement of a large/charged particle
down its concentration gradient through a carrier/channel protein.
What is the process of facilitated diffusion using a carrier protein? - Accurate answers Large
molecule binds to a carrier protein in membrane.
Protein changes shape.
Protein releases the large molecule on the opposite side of the membrane.
What is the process of facilitated diffusion using a channel protein? - Accurate answers Channel
proteins form pores in membrane.
Charged particles can diffuse down their concentration gradients to the opposite side of the membrane.
What are the factors affecting simple diffusion? - Accurate answers Concentration gradient,
thickness of exchange surface and surface area.
What are the factors affecting facilitated diffusion? - Accurate answers Number of transport
proteins and strength of gradient.
What is osmosis? - Accurate answers Diffusion of water through a partially permeable membrane
from an area of high water potential to an area of lower water potential.
What are the factors affecting osmosis? - Accurate answers Water potential gradient.
Thickness of exchange surface.
, Surface area of exchange surface.
Outline a method for RP3 (investigation of osmosis using potato chips). - Accurate answers
Produce a series of dilutions from 1M sucrose solution (of a variety of different concentrations, 0M,
0.2M, 0.4M, 0.6M, 0.8M, 1M).
Use a cork borer to cut potatoes into identically-sized chips.
Blot them dry with a paper towel and measure the mass of each using a mass balance.
Place one chip into each of the sucrose solutions.
Put the test tubes into a water bath at 30°C for 20 minutes.
Take them out and reweigh the mass of the chips.
Calculate the %change in mass for each chip.
What is active transport? - Accurate answers The active process of moving molecules from an area
of low concentration to an area of high concentration using ATP.
Name one type of carrier protein and describe how it works. - Accurate answers Co-transporters.
Bind two molecules at once.
The concentration gradient of one of the molecules is used to move the other molecule against its own
concentration gradient.
Give an example of co-transport in mammals. - Accurate answers Glucose/Na+ co-transport.
Na+ actively transported out of the ileum epithelial cells into the blood by the Na+/K+ pump. This
creates a concentration gradient, higher concentration of Na+ in lumen than inside cell.
Na+ Defuses into the epithelial cells from the lumen Na+/glucose co-transporter proteins.
Co-transporter carries glucose into the cell with the sodium so glucose concentration inside the cell
increases.
Glucose diffuses out of the cell, down its concentration gradient, through a protein channel, into the
blood, by facilitated diffusion.
What are the factors affecting active transport? - Accurate answers Speed of individual carrier
proteins.
Number of carrier proteins present.
Rate of respiration/availability of ATP.
3.2.1 Cell Structure - Accurate answers
Eukaryotic cells - Accurate answers Complex, include all animal and plant cells (& algal/fungal
cells).
Algal and fungal cells - Accurate answers Algal: same organelles as plant cells including cell wall
and chloroplasts.
Fungal: similar to plant cells but cell walls made of chitin and no chloroplasts.
Organelles in eukaryotic cells: - Accurate answers Membrane-bound compartments which
separate metabolic reactions within a cell.
Nucleus - Accurate answers Contains chromosomes which are made from protein bound linear
DNA.
