2013 Unit 1 Jan

Question 1

Explain how downward movement of the diaphragm leads to air entering the lungs.

Answer 1

• Increases volume in lungs/thorax
• Lowers pressure in lungs/thorax
• Air pushed in by higher outside/ down pressure gradient

Question 2

This photograph was taken using a transmission electron microscope. The structure of the organelles visible in the photograph could not have been seen using an optical
(light) microscope. Explain why.

Answer 2

Optical microscope
• Has low resolution/ not high enough resolution
• Because wavelength of light not short enough/too long

Question 3

Name the monosaccharides of which the following disaccharides are composed.

Sucrose

Answer 3

• Fructose

* Glucose

Question 4

Name the monosaccharides of which the following disaccharides are composed.

Lactose

Answer 4

• Galactose

* Glucose

Question 5

Name the monosaccharides of which the following disaccharides are composed.

Maltose

Answer 5

• Glucose

* Glucose

Question 6

Where is the enzyme amylase is

produced

Answer 6

• Pancreas

Question 7

The product of the reaction catalysed

by the enzyme amylase

Answer 7

• Produces maltose

Question 8

Where is the enzyme maltase is

produced

Answer 8

• In/on epithelium (of small intestine)

Question 9

The product of the reaction catalysed by the enzyme maltase

Answer 9

• Produces glucose

Question 10

Cholera bacteria produce toxins which increase secretion of chloride ions into the lumen of the intestine.
Explain why this results in severe diarrhoea (watery faeces).

Answer 10

• Water lost into gut/water moves into gut/water leaves cells
• Low(er) water potential of intestine/gut (lumen)
• Osmosis/movement down a water potential
• Less/not enough water (reabsorbed)

Question 11

The functional form of TK is only produced when
a phosphate group is added to TK.

Addition of a phosphate group to the non-functional form of TK leads to production of the functional form of TK.
Explain how.

Answer 11

• Phosphate changes the active site
• Active site complementary to substrate
• Enzyme-substrate complex can form

Question 12

In these patients, the right ventricle still produces sufficient blood flow to keep the patient alive.
Suggest why the left ventricle requires the help of the artificial heart but the right
ventricle does not.

Answer 12

• Left ventricle pumps to whole body(except lungs)/pumps blood further
• Left ventricle does most work/produces greater pressure/produces greater force

Question 13

The pulse felt in the artery in the wrist can be recorded and used to measure heart rate.
Suggest why the pulse felt can be used to measure heart rate.

Answer 13

• Caused by pressure/surge of blood

* From one contraction/ beat of left ventricle/heart

Question 14

People with AIDS die because they are unable to produce an immune response to pathogens
Explain why this leads to death.

Answer 14

• Infected by/susceptible to other pathogens
• Pathogens reproduce/cause disease in host
• Damage cells/tissues/organs
• Release toxins

Question 15

Explain why each of the following means that a vaccine might not be effective against
HIV.

HIV rapidly enters host cells

Answer 15

• HIV enters cells before antibodies can bind to/destroy it

* Antibodies cannot enter cells (to destroy HIV)/stay in blood

Question 16

Explain why each of the following means that a vaccine might not be effective against HIV.

HIV shows a lot of antigenic variability

Answer 16

• Antigen on HIV changes
• Specific antibody/receptor no longer binds to new antigen
• Many different strains of HIV/many antigens present on HIV
• Not possible to make vaccines for all antigens

Question 17

Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer.
Describe other ways by which substances cross this membrane.

Answer 17

By Osmosis 
• From a high water potential to a low water potential 
• Through aquaporins/water channels;
By Facilitated Diffusion
• Channel/carrier protein
• Down a concentration gradient 
By Active Transport
• Carrier protein/protein pumps
• Against concentration gradient 
• Using ATP/energy from respiration

Question 18

Atheroma formation increases a person’s risk of dying.

Explain how.

Answer 18

• Atheroma is fatty material/cholesterol/
• In wall of artery;
• (Higher risk of) aneurysm
• (Higher risk of) thrombus formation/blood clot;
• Blocks coronary artery;
• Less oxygen/glucose to heart muscle/cells;
• Reduces/prevents respiration;
• Causing myocardial infarction/heart attack;
• Blocks artery to brain;
• Causes stroke/