Christmas

Question 1

The action of the carrier protein X in figure 1 is linked to a membrane-bound ATP hydrolase enzyme

Explain the function of ATP hydrolase

Answer 1

Releases energy (ATP > ADP + Pi)

Allows ions to be moved against the concentration gradient

Question 2

The movement of NA out of the cell allows the absorption of glucose into the cell lining the ileum

Explain how

Answer 2

Creates a concentration gradient of sodium in the blood

This means sodium and glucose can move into the cells using facilitated diffusion, down the concentration gradient

Question 3

Describe and explain two features you would expect to find in a cell specialised for absorption

Answer 3

Villi and microvilli to increase surface area

Lots of mitochondria for ATP

Question 4

Describe how amino acids join to form a polypeptide so there is always NH2 and COOH at ends

Answer 4

One amine group joins to one carboxyl group to form a peptide bond

Free amine at one end of chain and free carboxyl at other end

Question 5

Suggest how one antibody can be specific to tick protein and and to alpha-gal

Answer 5

Tick protein + alpha gal have a similar shape

Antibody complementary to both

Question 6

Describe a method the student could use to prepare colour standards and use them to give data for the total extracted

Answer 6

Use known concentration of extract

Prepare dilution series

Compare results with colour standards

Question 7

Explain how cellulose molecules are adapted for their function in plant cells

Answer 7

Provides strength to cell wall

Long straight chains

Linked by hydrogen bonds forming fibrils

Question 8

Explain why aspirin doesn’t affect other enzymes

Answer 8

Affects one monomer

Not found in all active sites

Question 9

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

Answer 9

Homogenisation breaks open cells

Filter to remove debris

Isotonic medium to prevent damage to mitochondria by osmosis

Kept cold to prevent enzyme activity

Centrifuge at slow speed to separate heavy organelles (nucleus)

Respin supernatant at high speed to get pellet of mitochondria

Question 10

Describe the principles and limitation of using a TEM to investigate cell structure

Answer 10

Electrons pass through specimen

Denser parts absorb more electrons so, appear darker

Electrons have a short wavelength and so a high resolution

Cannot view living specimen

Specimen must be very thin

Artefacts present

Image in 2D