2012 Unit 1 June

Question 1

The scientists used a transmission electron microscope to study the structure of the
amoeba. Explain why

Answer 1

• High/ better resolution
• Shorter wavelength
• To see internal structures/
organelles/named
organelles;

Question 2

Air moves into the lungs between times P and Q. Explain how the diaphragm
causes this.

Answer 2

• Diaphragm contracts/moves
down/ flattens;
• Increases volume (of thorax)
• Decrease in pressure;
• Air moves from high to lower
pressure/down pressure
gradient;

Question 3

Describe how oxygen in air in the alveoli enters the blood in capillaries.

Answer 3

• Diffusion;
• Across (alveoli)epithelium/
(capillary) endothelium;

Question 4

What is a pathogen?

Answer 4

• Organism that causes
disease
•

Question 5

When a pathogen enters the body it may be destroyed by phagocytosis.
Describe how.

Answer 5

• Phagocyte recognises
(foreign) antigen;
• (Pathogen)engulfed to form phagosome
• Phagosome fuses/joins with
lysosome;
• Lysosome contains enzymes;
• Pathogen digested/ molecules
hydrolysed;

Question 6

Explain why these antibodies are only effective against a specific pathogen.

Answer 6

• Antigens (on pathogen) are a
specific shape
• Antibody complementary to antigen/ antibody-antigen complex forms;

Question 7

Describe how the student would show that reducing sugars were present in a
solution.

Answer 7

• Add Benedict’s;
• Heat;
• Red/orange/yellow/green
(shows reducing sugar
present);

Question 8

The peptides released when gluten is digested cannot be absorbed by
facilitated diffusion (lines 2 – 3). Suggest why

Answer 8

• Too big/ wrong shape;
• To pass through membrane
• Carrier / channel protein
•

Question 9

Explain why the peptides cause an immune response (

Answer 9

• Foreign/(act as) antigen /non-self

Question 10

The heart controls and coordinates the regular contraction of the atria and ventricles.
Describe how.

Answer 10

• SAN → AVN → bundle of His fibres
•  Impulses / electrical activity
(over atria)
• Atria contract;
• Non-conducting tissue
(between atria and ventricles)
• Delay (at AVN) ensures atria
empty/ ventricles fill before
ventricles contract;
• Ventricles contract from
apex upwards

Question 11

The diet of a person can increase the risk of coronary heart disease.
Explain how.

Answer 11

• Too much saturated fat/
cholesterol in diet;
• Increase in LDL/ cholesterol in
blood;
• Fatty deposits/
plaques in artery walls;
•  Blocks
coronary arteries;
• Less oxygen/ glucose to heart
muscle /tissue/ cells
• Increase in blood pressure
• (Increased risk of )clot /
thrombosis