Biological Membranes | OCR A-Level Biology A (H420)
Biological Membranes
- 60 questions
- 4 subtopics
- Module 2: Foundations in biology
- Component 01, Component 02 and Component 03
Biological membranes is the fifth section of Module 2.
It covers the fluid mosaic model and what each component of a membrane does, the conditions that make a membrane leak, the four ways substances cross it, and osmosis in animal and plant cells.
Sample questions from Biological Membranes
Answer each one closed book first, then open the answer.
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Membrane structure and the fluid mosaic model
Explain how phospholipids are arranged in a membrane bilayer.
Show the answer
Phospholipids arrange with their hydrophilic (phosphate) heads facing outward towards the aqueous environments and their hydrophobic (fatty acid) tails facing inward, away from water. -
Membrane structure and the fluid mosaic model
What is the function of carrier proteins in membranes?
Show the answer
They bind to specific molecules and change shape to transport them across the membrane, in facilitated diffusion or active transport. -
Factors affecting membrane permeability
Why does ethanol increase the leakage of pigment from beetroot cells?
Show the answer
Ethanol dissolves the phospholipids in the tonoplast and plasma membrane, allowing the red pigment (betalain) to leak out. -
Factors affecting membrane permeability
What happens to membrane proteins above about 60 degrees Celsius?
Show the answer
They denature, losing the tertiary structure that channel and carrier function depends on, so the membrane leaks freely. -
Diffusion, active transport, endocytosis and exocytosis
Why is ATP required for active transport?
Show the answer
Energy from ATP is needed to change the shape of carrier proteins so they can move substances against the concentration gradient. -
Diffusion, active transport, endocytosis and exocytosis
Does simple diffusion require ATP? Explain.
Show the answer
No; diffusion is a passive process driven by the kinetic energy of molecules moving down their concentration gradient. -
Osmosis and water potential
Describe what happens to an animal cell in a solution with lower water potential than the cell.
Show the answer
Water leaves the cell by osmosis; the cell shrinks and becomes crenated (wrinkled). -
Osmosis and water potential
How can the water potential of plant tissue be determined experimentally?
Show the answer
Plant tissue is placed in a range of solution concentrations; the concentration at which there is no change in mass or length indicates the solution has the same water potential as the tissue.
The 4 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Membrane structure and the fluid mosaic model | What a membrane does at the cell surface and inside organelles, and the phospholipids, cholesterol, glycolipids, channel, carrier and receptor proteins and glycoproteins that make it up. | 21 |
| Factors affecting membrane permeability | How temperature and organic solvents damage a membrane, and the beetroot investigation that measures the pigment released. | 10 |
| Diffusion, active transport, endocytosis and exocytosis | Simple and facilitated diffusion, active transport and the ATP it needs, endocytosis and exocytosis, and which of these processes are passive. | 13 |
| Osmosis and water potential | Water potential and the direction water moves, lysis and crenation in animal cells, turgor and plasmolysis in plant cells, and the percentage change in mass calculation. | 16 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby sections
OCR A-Level Biology A Active Recall Guide
Every section, not just this one. 1,833 questions with their answers.