Biology Paper 1

Explain the importance of emulsification in the digestion of lipids. (2)

1. (Small droplets) increase surface area

2. (So) faster/increased (rate of) lipase/enzyme hydrolysis/activity

Explain the importance of the role of micelles in the absorption of lipids. (2)

1. Carry fatty acids to cell

2. (So) fatty acid diffuses (into cell)

Describe and explain the adaptations of leaves that maximise gas exchange. Do not refer to organelles in your answer. [4 marks]

1. Many stomata

2. Stomata allow (gas) diffusion

3. Air spaces in mesophyll

4. Large surface area of cells/cell membranes for (rapid) diffusion

5. Large (leaf) surface area to volume ratio so high/increases diffusion (rate)

6. Thin (leaves) so short diffusion distance/ pathway;

Define the quaternary structure of a protein. [1 mark]

More than 1 polypeptide

Explain how two enzymes with different amino acid sequences can catalyse the same reaction. [2 marks]

1. active sites have similar tertiary structures/amino acid sequences

2. form enzyme-substrate complexes

Describe the complete digestion of starch by a mammal. [4 marks]

1. Hydrolysis

2. (Of) glycosidic bonds;

3. (Starch) to maltose by amylase

4. (Maltose) to glucose by disaccharidase/maltase

5. Membrane-bound (disaccharidase/maltase);

Name the bond formed between a fatty acid and glycerol in a triglyceride molecule. [1 mark]

Ester

On Figure 1, draw a circle around the part of the fatty acid molecule and the part of the glycerol molecule that is removed to form a bond in a triglyceride molecule.

Circle drawn around H in one of the HO groups of the glycerol

AND the OH group of the fatty acid

Use Table 1 to describe the relationship between fatty acid structure and fatty acid melting point. [1 mark]

As (number of C) double bonds increases, melting point decreases

Vitamin A is a fat-soluble substance.

Micelles are involved in the process of vitamin A absorption.

Describe the process of vitamin A absorption into cells lining the ileum. [3 marks]

1. Combine/mix/join with bile salts

2. Make (more) soluble

3. (Micelles) breakdown close to cells OR Transport to cells/lining

4. Diffuses (into cells/ileum)

Describe how we breathe in. [3 marks]

1. Diaphragm contracts pulling diaphragm down

2. External intercostal muscles contract pulling/moving ribs upwards/outwards

3. Volume increase and pressure decrease in thorax/lungs

Explain why the scientist used very thin slices of alveolar tissue with the optical microscope. [2 marks]

1. Single/few layer(s) of cells/tissue

2. Light can pass through

Small tears may occur in the layers of tissue in an aorta wall. These tears weaken the wall without bursting the aorta. Scientists:

• measured the aorta diameter (d) in a large population of people over 60 years of age

• calculated the risk of an aorta wall developing a tear

Blood may push through the tears in the aorta wall. This produces a balloon-like swelling called an aneurysm and increases the aorta diameter. Aneurysms can cause the aorta to burst.

Using all the information, what can you conclude about aorta diameter and the risk of developing an aneurysm? [3 marks]

1. Small diameters are low risk of tears so unlikely to/do not have aneurysms

   • OR As diameter increases, risk of tears increases and (risk of developing) aneurysms increase

2. Few people have/at high risk of tear

   • OR Few people have/at high risk of aneurysms

3. Diameters > / above 4.5 (cm) at high risk (of tears) so may have aneurysms

4. (High risk of) tear does not mean aneurysm will/has occurred