Cell Membrane Structure

Question 1

Describe the fluid mosaic model of membranes?

Answer 1

Fluid: phospholipid bilayer in which individuals phospholipids can move= membrane has flexible shape
Mosaic: extrinsic & intrinsic proteins of different sizes and shapes are embedded

Question 2

Explain the role of cholesterol & glycolipids in membranes?

Answer 2

Cholesterol: steroid molecules in plasma membranes: connects phospholipids and reduces fluidity to make bilayer more stable
Glycolipids: cell signalling & cell recognition

Question 3

Explain the function of extrinsic and transmembrane proteins in membranes

Answer 3

-binding sites/ receptors e.g for hormones & drugs
-antigen (glycoproteins)
-bind cells together
-involved in cell signalling

Question 4

Explain the function of intrinsic transmembrane proteins in membranes

Answer 4

-electron carriers (respiration/photosynthesis)
-channel protein (facilitated diffusion)
-carrier protein (facilitated diffusion/active transport)

Question 5

Explain the function of membranes within cells

Answer 5

-provides internal transport system
-selectively permeable to regulate passage of molecules into/out of organelle or within molecules
-provide reaction surface
-isolate organelle from cytoplasm for specific metabolic reactions

Question 6

Explain the function of cell surface membrane

Answer 6

-isolated cytoplasm from extracellular environment
-selectively permeable to regulate transport of substance
-involved in cell signalling/ cell recognition

Question 7

Name and explain factors which affect membrane permeability

Answer 7

-Temperature: high temperature denatures membrane proteins/phospholipid molecules have more kinetic energy & move further apart
-pH: changes tertiary structure of membrane proteins
-use of a solvent: may dissolve membrane

Question 8

How could colorimetry be used to investigate membrane permeability?

Answer 8

1) use plant tissue with soluble pigment in vacuole= pigment diffuses into solution
2)select colorimeter filter with complementary colour
3) use distilled water to set colorimeter to 0. Measure absorbable/% transmission value of solution
4)high absorbance/low transmission= more pigment in solution