Biology by Bradford
2.3.A, 2.3.BThe fluid mosaic model
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2.3 Plasma Membrane: revision map
The subtopic in the middle and four tasks round it: label a diagram, complete a table and fill 11 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Plasma Membrane
AP Biology ยท Unit 2 Cell Structure and FunctionHover over a box to see it. Untick it to leave it off this sheet and its printout.
Name2.3.AA phospholipid bilayer
Each phospholipid has a polar, phosphate head and two nonpolar fatty acid tails. In water the molecules arrange themselves into a with the heads facing the watery cytoplasm and extracellular fluid and the tails shielded in the middle. The interior is hydrophobic, so it is a barrier to ions and large polar molecules. The membrane is described as a fluid mosaic because its phospholipids and many of its proteins can move sideways.
Topic 2.3Plasma Membrane
2.3.A, 2.3.BWhat is in a membrane
| Component | Role |
|---|---|
| protein | spans the bilayer; forms channels and carriers, or acts as a receptor |
| Peripheral protein | attached to one surface; can be an enzyme or anchor the cytoskeleton |
| sits between phospholipids in animal membranes and moderates fluidity | |
| Glycoprotein | carries a short carbohydrate chain used in cell |
2.3.BKeeping the membrane fluid
The fluidity of a membrane depends on its lipids. Fatty acids with double bonds are and kinked, so the tails pack loosely and the membrane stays fluid. At low temperature, cholesterol stops the tails from packing too tightly, and at high temperature it stops them from moving too freely, so it acts as a fluidity buffer. Cells that live in cold conditions make membranes richer in the kinked kind of fatty acid.
Word bank bilayercholesterolCholesterolglycoproteinhydrophilicIntegralintegral proteinperipheral proteinphospholipidrecognitionunsaturated
Answer key
Every box on the sheet with its gaps filled in, as the subtopic reads in full.
LabelThe fluid mosaic model
- phospholipid
- integral protein
- cholesterol
- peripheral protein
- glycoprotein
GapsA phospholipid bilayer
Each phospholipid has a polar, hydrophilic phosphate head and two nonpolar fatty acid tails. In water the molecules arrange themselves into a bilayer with the heads facing the watery cytoplasm and extracellular fluid and the tails shielded in the middle. The interior is hydrophobic, so it is a barrier to ions and large polar molecules. The membrane is described as a fluid mosaic because its phospholipids and many of its proteins can move sideways.
TableWhat is in a membrane
Component Role Integral protein spans the bilayer; forms channels and carriers, or acts as a receptor Peripheral protein attached to one surface; can be an enzyme or anchor the cytoskeleton Cholesterol sits between phospholipids in animal membranes and moderates fluidity Glycoprotein carries a short carbohydrate chain used in cell recognition GapsKeeping the membrane fluid
The fluidity of a membrane depends on its lipids. Fatty acids with double bonds are unsaturated and kinked, so the tails pack loosely and the membrane stays fluid. At low temperature, cholesterol stops the tails from packing too tightly, and at high temperature it stops them from moving too freely, so it acts as a fluidity buffer. Cells that live in cold conditions make membranes richer in the kinked kind of fatty acid.