cell membrane

Question 1

Describe two functions of the structure made from the parts labelled hydrophobic tails

Answer 1

form(water) impermeable barrier to water-soluble substances / selectively
permeable / allows non-polar molecules to pass through;

allows cell to maintain different concentrations either side

Question 2

extrinsic protein function

Answer 2

(surface / extrinsic protein) for cell recognition / binding to
hormones / identification

Question 4

Explain how three features of a plasma membrane adapt it for its functions.

Answer 4

phospholipid bilayer (as a barrier);

2 forms a barrier to water soluble / charged substances /
allows non-polar substances to pass

OR

maintains a different environment on each side / compartmentalisation;

3 bilayer is fluid;

4 can bend to take up different shapes for phagocytosis /
form vesicles / self repair;

5 channel proteins (through the bilayer) / intrinsic protein;

6 let water soluble / charged substances through / facilitated diffusion;

7 carrier proteins (through the bilayer);

8 allow facilitated diffusion / active transport;

9 surface proteins / extrinsic proteins, glycoproteins / glycolipids;

10 cell recognition / act as antigens / receptors;

11 cholesterol;

12 regulates fluidity / increases stability;

Question 5

Describe and explain two features you would expect to find in a cell specialised for absorption

Answer 5

Folded membrane/microvilli so large surface area (for absorption);

Reject references to ‘villi’.

Accept ‘brush border’ for ‘microvilli’.

2. Large number of co-transport/carrier/channel proteins so fast rate (of absorption)

OR

Large number of co-transport/carrier proteins for active transport

OR

Large number of co-transport/carrier/channel proteins for facilitated diffusion;

3. Large number of mitochondria so make (more) ATP (by respiration)

OR

Large number of mitochondria for aerobic respiration

OR

Large number of mitochondria to release energy for active transport;

4. Membrane-bound (digestive) enzymes so maintains concentratio

Question 6

Draw phospholipids on Figure 2 to show how the carrier protein, SGLT1, would fit into the cell-surface membrane.

Do not draw more than eight phospholipids.

LEARN TO DRAW PHOSPHOLIPIDS

Answer 6

https://www.thestudentroom.co.uk/attachment.php?attachmentid=1069252

Question 7

shows the SGLT1 polypeptide with NH2 at one end and COOH at the other end.

Describe how amino acids join to form a polypeptide so there is always NH2 at one end and COOH at the other end.

You may use a diagram in your answer.

Answer 7

One amine/NH2 group joins to a carboxyl/COOH group to form a peptide bond;

.

2. (So in chain) there is a free amine/NH2 group at one end and a free carboxyl/COOH group at the other