Topic 4A and 4B

Question 1

1(a) Products from sugarcane, such as starch and cellulose, are used to make bioplastic.
(i) How many of the following statements about starch are correct?
* contains α-glucose and β-glucose molecules
* contains amylose and amylopectin
* stored in the tonoplast (1)

A none
B one
C two
D three

Answer 1

B- one

Question 2

(ii) How many of the following statements about a cellulose molecule are correct?
* contains α-glucose and β-glucose molecules
* contains 1,4 glycosidic bonds
* forms hydrogen bonds with other cellulose molecules (1)
A none
B one
C two
D three

Answer 2

C-two

Question 3

(b) Bioplastic bags made from sugarcane take up to six months to decompose. Bacteria secrete enzymes onto the bags during the process of decomposition.
(i) Name two structures found in bacterial cells that are involved in the synthesis of these enzymes. (1)

Answer 3

bacterial chromosome and 70s chromosome

Question 4

(ii) Decomposition of bioplastic bags occurs faster if there is increased bacterial growth. Explain the conditions needed for increased bacterial growth. (3)

Answer 4

oxygen for aerobic respiration
glucose for respiration
optimum temperature for faster enzyme.

Question 5

2 (a) State what is meant by the term species. (1)

Answer 5

a group of organisms that are capable of mating and produce fertile offspring

Question 6

*(ii) The ironwood tree has wood containing chemical compounds called naphthoquinones. These compounds have antibacterial properties. Scientists are investigating whether these compounds could be used to develop a drug to treat people infected with Y. pestis. Describe the methods that would be used to trial a drug containing these compounds. (6)

Answer 6

the compound needs to be extracted from trees and used to make a drug.
compounds tested on Y. pestis in vitro
tested on human cells
phase 1 small scale tests on healthy people.
review by independent scientists to see if work can progress to stage 2.
phase 2 - drug tested on small groups of patients who have the plague
appropriate concentrations identified
phase 3 - drug tested on larger groups of patients who have the plague.
placed randomly in two groups - one group receives a drug containing the chemical compounds and the other receives the placebo.
double-blind test
analyze results with appropriate statistical test

Question 7

(ii) Explain the importance of each of these ions to the plant. (3)

Answer 7

calcium ions to make calcium pectate
to hold cells together
magnesium ions to make chlorophyll so photosynthesis can occur.
nitrates are needed to make amino acids.

Question 8

(iii) The bacterium Pseudomonas aeruginosa causes lung infections in humans. Describe how a drug containing flavonoids could be tested in a stage II drug trial. (2)

Answer 8

(flavonoid drug) tested on small numbers of patients with P.aeruginosa
use of double-blind trial.

Question 9

(b) Explain how the arrangement of cellulose molecules and secondary thickening in xylem vessels contributes to the physical properties of the cell wall. (4)

Answer 9

cellulose molecules can be organized into microfibrils. (1)
due to layers of cellulose arranged in different directions. (1)
hydrogen bonds in cellulose molecules add strength. (1)
cellulose microfibrils held together by pectin. (1)
lignin makes outside of xylem vessels impermeable to water. (1)

Question 10

(b) The photograph shows a bottle of oil extracted from the plant oregano. This plant is native to the Mediterranean and western Asian countries. Oregano oil contains antimicrobial substances. This oil can be used in the production of plastic used to package food. Explain why this packaging may be chosen over traditional oil‑based plastic packaging. (2)

Answer 10

plant-based packaging is more sustainable than traditional oil-based packaging (1)
the antimicrobial property of the oregano oil will reduce the number of L.monocytogenes bacteria. (1)
resulting in fewer people getting the microbial disease (1)