biological molecules old spec exam questions

Question 1

suggest 3 reasons why it is more efficient to attach lactase to the beads.

Answer 1

-no need to remove from milk
-beads can be reused
-allows continuous process

Question 2

In the control experiments, cooked wheat was chopped up to copy the effect of
chewing.
Suggest a more appropriate control experiment. Explain your suggestion. (2)

Answer 2

add boiled salvia
salivary amylase denatured but otherwise same as other experiments.

Question 3

Explain what these results suggest about the effect of chewing on the digestion of
starch in wheat. (3)

Answer 3

some starch already digested when chewing
faster digestion of chewed starch
same digestion without chewing at end

Question 4

In humans, the enzyme maltase breaks down maltose to glucose.
This takes place at normal body temperature.
Explain why maltase:
* only breaks down maltose
* allows this reaction to take place at normal body temperature. (5)

Answer 4

-maltase has specific tertiary structure
-complimentary to maltose
-shape of active site changes slightly to mould around substrate/induced fit
-enzyme acts as a catalyst
-by forming enzyme substrate complex.

Question 5

Explain how a sports drink could provide an energy boost when running. (3)

Answer 5

-contains salt so glucose is absorbed more rapidly
-more glucose supplied to muscle cells for respiration
-increased respiration rate- more energy released.

Question 6

hydrogen bonds are important in cellulose molecules. Explain why. (2)

Answer 6

-forms microfibrals, which provides strengh/rigidity.
-hydrogen bonds strong in large numbers.

Question 7

Use the information in the figure to explain two ways in which fatty acids are important in
the formation of new cells. (4)

Answer 7

fatty acids used to produce phospholipids
-phospholipids in cell membrane

-fatty acids respired to release energy
-used for protein synthesis to produce proteins.

Question 8

describe the role of DNA polymerase in DNA replication. (1)

Answer 8

-joins adjacent nucleotides

Question 9

other than being similar, give two ways in which prokaryotic DNA is different from eukaryotic DNA. (2)

Answer 9

-no histone proteins
-no introns
-circular DNA/not linear.

Question 10

The DNA of the virus is different from that of other organisms. Use the table
above and your knowledge of DNA to suggest what this difference is. Explain
your answer. (2)

Answer 10

A not equal to T and C not equal to G
-no base pairings
-DNA is single stranded.

Question 10

Humans and grasshoppers have very similar percentages of each base in
their DNA but they are very different organisms.
Use your knowledge of DNA structure and function to explain how this is
possible.
……………………………………………………………………………………………………. (2)

Answer 10

-different genes
-different order of bases
-so different proteins

Question 11

The events that take place during interphase and mitosis lead to the production of two
genetically identical cells. Explain how. (4)

Answer 11

-DNA replicated
-2 sister chromatids joined by centromere
-sister chromatids pulled to opposite poles of the cell
-complimentary base pairings

Question 13

explain the difference in the structure of starch and cellulose

Answer 13

-starch is made from alpha glucose wheras cellulose is made from beta glucose
-position of hydrogen and hydroxyl groups on carbon 1 atom inverted.