Home / IB DP Biology- B2.1 Membranes and membrane transport – IB Style Questions For SL Paper 1A

IB DP Biology- B2.1 Membranes and membrane transport - IB Style Questions For SL Paper 1A -New Syllabus

IBDP Biology SL Paper 1 - All Chapters

Question

Which molecule is paired with the component of the cell membrane that allows it to pass through the membrane?

 MoleculeComponent of the cell membrane
AInsulinAquaporin
BGlycogenChannel protein
COestradiolPhospholipid bilayer
DCarbon dioxidePump protein
▶️ Answer/Explanation

Correct Answer: \( \boxed{\mathbf{C}} \)

Oestradiol is a lipid-soluble steroid hormone that passes directly through the phospholipid bilayer by simple diffusion. In contrast, insulin and glycogen are too large to diffuse across the membrane, and carbon dioxide diffuses through the bilayer rather than a pump protein.

Question

The diagram represents a section of a cell membrane with labelled components. Which labelled structure is responsible for enabling cell recognition?
▶️ Answer/Explanation
Detailed solution

Label A points to a glycoprotein with an attached carbohydrate chain. These carbohydrate side groups act as identification markers on the cell surface and are essential for cell recognition and communication. Therefore, the structure that enables recognition between cells is A.
✅ Answer: (A)

Question

The diagram shows protein channels involved in the passive movement of a substance into the cell across the cell membrane.

protein channel diffusion diagram

What describes this movement?

A. Energy of ATP is used to transport substances into the cell.
B. Substances can move from areas of low to areas of high concentration.
C. The proteins ensure that movement of substances is only in one direction.
D. Net movement occurs until the concentrations in and out of the cell are equal.

▶️ Answer/Explanation

Answer: D. Net movement occurs until the concentrations in and out of the cell are equal.

Explanation:
The diagram shows protein channels embedded in a cell membrane that help substances move into the cell from the extracellular space to the intracellular space.

This type of movement is known as passive transport (specifically, facilitated diffusion), and it has the following key features:

  • No energy (ATP) is required for this process.
  • Substances move from high to low concentration, following the concentration gradient.
  • Movement continues until concentrations are equal on both sides, a state called equilibrium.
  • The proteins do not control direction—movement depends on concentration differences.
  • Movement from low to high concentration would require energy (i.e., active transport), not shown here.

Option Analysis:

A. Incorrect – Passive transport does not require ATP.

B. Incorrect – Movement from low to high concentration requires energy (active transport).

C. Incorrect – Proteins in passive transport do not force one-way movement; it is driven by concentration differences.

D. Correct – In diffusion, net movement continues until concentrations inside and outside the cell reach equilibrium.

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