Question

4 the diagram shows part of the cell surface membrane of an animal cell. the table shows the concentration of substances in the extracellular and intracellular environment.

	extracellular	intracellular
partial pressure of oxygen /mmhg	150	107
partial pressure of carbon dioxide /mmhg	65	94
concentration of glucose /mg dl⁻¹	101	132

which statements correctly describe the movements of substances across the membrane?
1 oxygen diffuses through molecules m into the cell.
2 glucose diffuses through molecules m out of the cell.
3 molecule l has a hydrophobic channel for carbon dioxide to move out of the cell.
4 molecule l has a hydrophilic channel for glucose to move into the cell.
a 1 and 3 only
b 1 and 4 only
c 2 and 3 only
d 2 and 4 only

Explanation:

1. Analyze Statement 1: Molecules M are phospholipids (part of the bilayer). Oxygen is non - polar and can diffuse through the phospholipid bilayer (molecules M) from an area of higher partial pressure (extracellular, 150 mmHg) to lower (intracellular, 107 mmHg) into the cell. So statement 1 is correct.
2. Analyze Statement 2: Glucose concentration is higher intracellularly (132 mg dL⁻¹) than extracellularly (101 mg dL⁻¹). Diffusion is from high to low concentration, so glucose should move into the cell, not out. And glucose moves through protein channels (molecule L, not M). So statement 2 is incorrect.
3. Analyze Statement 3: Carbon dioxide is non - polar and can diffuse through the phospholipid bilayer (molecules M) or through the cell membrane without a hydrophobic channel in L (since L is a protein, and carbon dioxide diffuses freely). Also, carbon dioxide has a higher partial pressure intracellularly (94 mmHg) than extracellularly (65 mmHg), so it moves out of the cell, but not through a hydrophobic channel in L. So statement 3 is incorrect.
4. Analyze Statement 4: Molecule L is a protein (channel protein). Glucose is polar, so it needs a hydrophilic channel (in molecule L) to move from an area of lower concentration (extracellular, 101 mg dL⁻¹) to higher concentration (intracellular, 132 mg dL⁻¹) via facilitated diffusion. So statement 4 is correct.

Only statements 1 and 4 are correct.

Answer:

B. 1 and 4 only