2025 AQA A-Level Biology
Paper 1 | Complete Exam
Questions with Verified
Answers | Fully Updated &
Graded A+ | NEW!! NEW!!!
What is the function of the cell membrane? - ANS✔✔---To control what
enters and leaves the cell, acts as a barrier between the cell and its
environment.
What is the function of cholesterol in the CSM? - ANS✔✔---Make
phospholipids pack more closely together, restricting the movement of
the phospholipids, making the membrane less fluid/more rigid.
What is simple diffusion? - ANS✔✔---The (passive) movement of
particles from an area of high concentration to an area of low
concentration.
What is facilitated diffusion? - ANS✔✔---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? -
ANS✔✔---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?
- ANS✔✔---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? - ANS✔✔--- Concentration
gradient, thickness of exchange surface and surface area.
What are the factors affecting facilitated diffusion? - ANS✔✔---Number
of transport proteins and strength of gradient.
What structural feature of the cell membrane allows substances
to enter/leave? - ANS✔✔---Partially permeable
What is the fluid mosaic model? - ANS✔✔---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. - ANS✔✔---
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 osmosis? - ANS✔✔---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? - ANS✔✔---Water potential
gradient.
Thickness of exchange surface.
, Surface area of exchange surface.
Outline a method for RP3 (investigation of osmosis using potato chips). -
ANS✔✔---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? - ANS✔✔---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. - ANS✔✔---
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. - ANS✔✔---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.
Paper 1 | Complete Exam
Questions with Verified
Answers | Fully Updated &
Graded A+ | NEW!! NEW!!!
What is the function of the cell membrane? - ANS✔✔---To control what
enters and leaves the cell, acts as a barrier between the cell and its
environment.
What is the function of cholesterol in the CSM? - ANS✔✔---Make
phospholipids pack more closely together, restricting the movement of
the phospholipids, making the membrane less fluid/more rigid.
What is simple diffusion? - ANS✔✔---The (passive) movement of
particles from an area of high concentration to an area of low
concentration.
What is facilitated diffusion? - ANS✔✔---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? -
ANS✔✔---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?
- ANS✔✔---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? - ANS✔✔--- Concentration
gradient, thickness of exchange surface and surface area.
What are the factors affecting facilitated diffusion? - ANS✔✔---Number
of transport proteins and strength of gradient.
What structural feature of the cell membrane allows substances
to enter/leave? - ANS✔✔---Partially permeable
What is the fluid mosaic model? - ANS✔✔---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. - ANS✔✔---
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 osmosis? - ANS✔✔---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? - ANS✔✔---Water potential
gradient.
Thickness of exchange surface.
, Surface area of exchange surface.
Outline a method for RP3 (investigation of osmosis using potato chips). -
ANS✔✔---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? - ANS✔✔---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. - ANS✔✔---
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. - ANS✔✔---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.
