3.2.3 Transport Across Membranes

Question 1

Explain why an optical microscope can’t be used to see a plasma membrane

Answer 1

Doesn’t have a high enough magnification
Light has a longer wavelength

Question 2

Mucus contains glycoproteins. One is a polypeptide with the sugar lactose attached
Describe how lactose is formed + where in the cell it would be attached to a polypeptide to form a glycoprotein

Answer 2

Formed glucose + galactose
Joined by condensation reaction
Joined by glycosidic bond
Added to polypeptide in golgi apparatus

Question 3

Putting bee honey on a cut kills bacteria. Honey contains a high concentration of sugar.
Use your knowledge of water potential to suggest how putting honey on a cut kills bacteria.

Answer 3

Water potential in bacterial cells higher than in honey
Water leaves bacteria cells by osmosis
Loss of water stops metabolic reactions.

Question 4

Explain why the rate of CO2 falls to 0 when a light is switched off

Answer 4

No use of carbon dioxide in photosynthesis
No diffusion gradient for carbon dioxide into leaf, only one out of the leaf

Question 5

Explain how a monoclonal antibody could prevent a protein from working

Answer 5

Has specific tertiary structure
Binds to regulator protein
No longer complementary

Question 6

Describe the structure of a cell membrane

Answer 6

Phospholipid bilayer - impedes polar molecules
Heads on outside, tails inside
Proteins, glycoproteins, glycolipids
Cholesterol - restricts movements