A level Bio 1.4 Protein and Enzymes

A student investigated starch digestion by mixing starch with a solution of the enzyme used to digest starch. The student did a biochemical test for protein when starch digestion was completed.

The student’s test for protein was positive. Explain why. (2)

(Positive because) enzymes are protein (1)

(because) enzymes not used up (in reactions) (1)

A scientist investigated the hydrolysis of the protein casein.

The scientist:

• mixed a solution of a protease enzyme with a solution of casein

• then measured the casein concentration in the mixture at intervals

• controlled all relevant variables appropriately.

For this investigation, identify:

the independent variable and the dependant variable (2)

(independant) Time (of measurement/test/sample taken) (1)

(Dependant) Casein concentration (1)

Describe the primary structure of all proteins (2)

Sequence/order of amino acids (1)

(Joined by) peptide bonds (1) 

Complete the passage with the appropriate terms

ATP synthase comprises several polypeptides, so is said to have a _______________ structure. It catalyses the synthesis of an ATP molecule by a _______________ reaction; this involves the _______________ of a water molecule. The ATP synthase in the figure above is in a mitochondrion so would catalyse reactions during _______________.

1) Quaternary 

2) Condensation 

3) Release/loss/formation

4) (Aerobic) respiration  

All correct = 2 marks, 2–3 correct = 1 mark,

As shown in the figure above, ATP synthase has two functions.

• It catalyses the synthesis of ATP.

• It allows the movement of H+ ions.

Suggest how the shape of the ATP synthase allows it to have these two

functions.

Explain your answers.(4)