Alevel Biology aqa questions

Alevel Biology aqa questions qs I didn't get

name and describe five ways substances can move across the cell surface membrane into a cell (5 marks)

1. (Simple) diffusion of small/non-polar molecules down a

concentration gradient;

2. Facilitated diffusion down a concentration gradient via

protein carrier/channel;

3. Osmosis of water down a water potential gradient;

4. Active transport against a concentration gradient via

protein carrier using ATP;

5. Co-transport of 2 different substances using a carrier

protein;

describe the structure of DNA (5 marks)

1. Polymer of nucleotides;

2. Each nucleotide formed from deoxyribose, a

phosphate (group) and an organic/nitrogenous base;

3. Phosphodiester bonds (between nucleotides);

4. Double helix/2 strands held by hydrogen bonds;

5. (Hydrogen bonds/pairing) between adenine, thymine

and cytosine, guanine;

describe how a triglyceride molecule if formed (3 marks)

1. One glycerol and three fatty acids;

2. Condensation (reactions) and removal of

three molecules of water;

3. Ester bond(s) (formed);

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

1. Folded membrane/microvilli so large surface

area (for absorption);

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 concentration gradient (for fast

absorption);

Describe the role of micelles in the absorption of fats into the cells lining the ileum.

1. Micelles include bile salts and fatty acids;

2. Make the fatty acids (more) soluble in water;

3. Bring/release/carry fatty acids to cell/lining (of the

ileum);

4. Maintain high(er) concentration of fatty acids to

cell/lining (of the ileum);

5. Fatty acids (absorbed) by diffusion;