2015 Unit 1

Question 1

Maltose is hydrolysed by the enzyme maltase

Explain why maltase catalysed only this reaction

Answer 1

• Active site of enzyme has a specific shape/ tertiary structure.
• Active site complementary to substrate
• Only maltose can bind
• To form enzyme substrate complex

Question 2

Give two ways in which pathogens can cause disease

Answer 2

• Releases toxins

* Kills cells/tissues

Question 3

Putting Bee honey on a cut kills bacteria. Honey contains a high concentration of sugar.

Suggest how putting honey on a cut kills bacteria

Answer 3

• Water potential in bacterial cells is higher than in honey
• Water leaves bacteria by osmosis
• Loss of water stops metabolic reactions

Question 4

When a person has an asthma attack, the airways in the lungs become narrower.

Give one reason why the airways become narrower

Answer 4

• Lining inflamed/swollen/ muscle(around airways) contracts/ more mucus produced

Question 5

Describe how you could use the emulsion test to show the presence of oil in a sample of fish?

Answer 5

• Shake with ethanol/alcohol
• Then add water
• White/milky/cloudy layer indicates oil

Question 6

Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells?

Answer 6

• Cell homogenisation to break open cells
• Filter to remove (large) debris
• Use isotonic solution to prevent damage to organelles
• Keep cold to prevent damage by enzymes/ use buffer solution to prevent protein denaturation
• Centrifuge to separate heavy organelles
• Re-spin at higher speed to get mitochondria in pellet/at bottom

Question 7

Describe the principles and the limitations of using a transmission electron microscope to investigate cell structure

Answer 7

Principles
• Electrons pass through thin specimen
• Denser parts absorb more electrons
• So denser parts appear darker
• Electrons have a shorter wavelength so give high resolution
Limitations
• Cannot look at living material: must be in vacuum.• Specimen must be very thin • Artefacts present • Long preparation time • Only 2D images produced

Question 8

Which organ produces amylase

Answer 8

• Pancreas

Question 9

Which organ produces maltase

Answer 9

• Small intestine

Question 10

This organelle function is protein synthesis, what is this organelle

Answer 10

• Ribosomes

Question 11

This organelle function is to modify proteins ( for example, adds carbohydrates to proteins). What is this organelle?

Answer 11

• Golgi Apparatus

Question 12

This organelle function is aerobic respiration. What is this organelle

Answer 12

• Mitochondria

Question 13

Monosaccharides and disaccharides taste sweet. The lactose-free milk made after hydrolysis with lactase tastes sweeter than the cows milk containing lactose. Suggest why

Answer 13

• Lactose hydrolysed to galactose and glucose
• So more sugar molecules
• So more sugars produced that are sweeter than lactose