DP Biology (first assessment 2025)

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Question 19M.2.HL.TZ1.3b

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.2.HL.TZ1.3b
Level HL Paper 2 Time zone TZ1
Command term Explain Question number b Adapted from N/A
b.
[Maximum mark: 2]
19M.2.HL.TZ1.3b
(b)

Explain how valves control the flow of blood through the heart.

[2]

Markscheme

a. valves open and close in response to changes in blood pressure/heart contraction/pumping ✔

b. valve prevents backflow/maintains direction of blood flow ✔

c. valves allow heart chambers to fill/to empty ✔

Examiners report

Most candidates knew that heart valves prevent backflow of blood but that was all. There were a variety of misconceptions such as that valves pump blood or that the SA node sends signals to the valves to make them open/close.

Syllabus sections