IB Biology HL B2.1 Membranes and membrane transport questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

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Question 1

Multiple choiceMedium1 mark

A researcher measures cell adhesion and cell recognition before and after selectively removing carbohydrate chains from glycoproteins and glycolipids on the extracellular surface of the plasma membrane. The results are shown.

Cell condition	Cells adhering to other cells (%)	Cells correctly recognized (%)
Untreated	82	91
Carbohydrate chains removed	46	52

What conclusion is supported by the results?

Show answer and explanation

Answer: A. Removing the extracellular carbohydrate chains lowered adhesion from 82% to 46% and correct recognition from 91% to 52%. The paired decreases support a role for these structures in both processes.
B: accounts for the decrease in recognition but overlooks the decrease in adhesion.
C: accounts for the decrease in adhesion but overlooks the decrease in recognition.
D: reverses the relationship: removal decreased both responses, rather than increasing them.
Remember: membrane carbohydrate chains can contribute to cell adhesion and cell recognition.

Question 2

Paper 2Medium16 marks

A researcher investigated the movement of different solutes across a model phospholipid bilayer. The same apparatus was used for separate trials, one solute per trial. Figure 1 shows the initial conditions for each trial. After 30.0 minutes, the amount of solute detected in chamber B was measured.

Solute tested	Description	Amount detected in chamber B after 30.0 min / nmol
Steroid	Non-polar molecule	15.2
Glucose	Polar molecule	1.6
Sodium ions	Ions	0.8
Polymer	Large, hydrophilic molecule	0.2

(a)

State the independent variable, the dependent variable and one variable controlled in the investigation.

[3]

(b)

Calculate the percentage of the initial amount of steroid detected in chamber B after 30.0 minutes.

[2]

(c)

Compare the amounts detected in chamber B for the four solutes.

[3]

(d)

Explain how the structure of the phospholipid bilayer accounts for the results for the steroid and the other three solutes.

[4]

(e)

A student concludes that the bilayer is an effective barrier to every solute tested. Evaluate this conclusion using the data.

[4]

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