Bio Moc Exam preparation

Question 1

Discuss the evidence for the theory that mitochondria may have evolved from free-living prokaryotes by endosymbiosis. [3 marks]

Answer 1

c. they have their own «circular» DNA AND reproduce on their own ✔
d. they have «70s» ribosomes AND can manufacture «their own» proteins ✔
e. have organelle«s» similar to free-living prokaryotes ✔

Question 2

Outline four types of membrane transport, including their use of energy. [4 marks]

Answer 2

a. simple diffusion is passive movement of molecules/ions along a concentration gradient ✔
b. facilitated diffusion is passive movement of molecules/ions along a concentration gradient through a protein channel «without use of energy» ✔
c. osmosis is the passage of water through a membrane from lower solute concentration to higher ✔ OWTTE
d. active transport is movement of molecules/ions against the concentration gradient«through membrane pumps» with the use of ATP/energy ✔

Question 3

Draw the structure of a dipeptide. [3 marks]

Answer 3

a. two amino acids, one with NH2/NH3+end and one with COOH/COO– end ✔
b. peptide bond between C=0 and N—H correctly drawn ✔
c. «chiral» C with H and R group on each amino acid ✔
d. peptide bond labelled/clearly indicated between C terminal of one amino acid and N terminal of the second amino acid ✔

Question 4

Explain the advantages of having both lipid and carbohydrate as energy stores in the human body.
[2 marks]

Answer 4

a. lipid is long-term energy storage

c. lipids store more energy «per gram»

Question 5

Sketch a graph to show the effect of temperature on the activity of enzymes. [2 marks]

Answer 5

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Question 6

Explain enzyme–substrate specificity. [3 marks]

Answer 6

a. enzymes are proteins with specific 3-D geometry/shape
b. enzymes with active site that binds with the substrate/reactants
c. active site shape only allows it to bind with specific substrates «with complementary shapes»

Question 7

Outline the function of codons. [1 mark]

Answer 7

«three bases on mRNA» coding for one amino acid «in a polypeptide» ✔

Question 8

Determine the sequence of amino acids that could be translated from the sequence of mRNA. [1 mark]

Answer 8

met-ser-arg-arg

Question 9

Determine the DNA base sequence transcribed to form this sequence of mRNA. [1 mark]

Answer 9

TAC TCG GCT TCC ATC GAC

Question 10

Suggest a hypothesis that accounts for the slightly different meaning of some codons in a very limited number of organisms. [1 mark]

Answer 10

the genetic code is not «in fact» universal

Question 11

State the type of reaction that removes water while linking amino acids together to form polypeptides.
[1 mark]

Answer 11

Condensation

Question 12

Label the parts of the DNA diagram indicated by I, II, III and IV. [2 marks]

Answer 12

a. I. cytosine
b. II. sugar-phosphate/covalent/phosphodiester bond
c. III. phosphate
d. IV. deoxyribose

Question 13

Explain how model making helped Watson and Crick to establish the structure of DNA. [2 marks]

Answer 13

b. built scale models of components of DNA

c. then attempted to fit them together in a way that agreed with the data «from separate sources»

Question 14

Outline the role of the enzyme helicase in replication.

[1 mark]

Answer 14

separates strands/double helix (by breaking hydrogen bonds)

Question 15

Outline the role of the enzyme DNA polymerase in replication.
[2 marks]

Answer 15

a. links nucleotides together to form a new strand of DNA

b. uses pre-existing strand of DNA as template

Question 16

List three characteristics of eukaryotic homologous chromosomes. [3 marks]

Answer 16

b. carry the same sequence of genes ✔
c. «but» not necessarily the same alleles «of those genes» ✔
d. both are present when nucleus is in diploid state ✔

Question 17

Using the following table, compare and contrast anaerobic cell respiration in yeasts and in humans. The first row has been completed
as an example. [3 marks]

Answer 17

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Question 18

Using the Punnett grid, explain how two parents can have children with any of the different ABO blood groups.
[3 marks]

Answer 18

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Question 19

State an application of plasmids in biotechnology. [1 mark]

Answer 19

to produce insulin/useful protein

Question 20

Meiosis in humans produces cells that participate in fertilization. Outline the processes involved in meiosis.
[5 marks]

Answer 20

a. meiosis reduces a diploid cell into (four) haploid cell(s);
b. (during prophase I) homologous chromosomes pair up/synapsis;
c. chromatids (break and) recombine / crossing over
d. (metaphase I) (homologous chromosomes) at the equator of the spindle / middle of cell;
e. (anaphase I) (homologous) chromosomes separate and move to opposite poles;

Question 21

Explain how evolution by natural selection depends on mutations. [4 marks]

Answer 21

a. mutations cause variation among organisms of same species/population;
b. some variations/mutations make individual more suited to its environment/way of life;
c. individuals that are better adapted survive and produce offspring;
d. individuals pass on genetic characteristics/mutation/variation to offspring;

Question 22

The images show parts of plants belonging to two different phyla.

State the phylum of plant X and of plant Y.
X:
Y:
[2 marks]

Answer 22

X: Filicinophyta ✔
Y: Coniferophyta/Conifera/Gymnosperms ✔

Question 23

Outline the types of evidence that can be used to place a species in a particular clade. [3 marks]

Answer 23

a. a clade is a group of organisms that have evolved from a common ancestor ✔
b. identify the base sequences of a gene ✔
c. identify amino acid sequence of a protein ✔

Question 24

The cladogram includes four marsupial (non-placental mammal) families.

Deduce the family that is most closely related to the Diprotodontoidea.
[1 mark]

Answer 24

Vombatidae/wombats ✔

Question 25

Distinguish between absorption of red, green and blue light by chlorophyll. [2 marks]

Answer 25

a. absorbs at blue and red (in high amount);

b. greatest absorption is of blue light / more blue light than red light absorbed;
c. low absorption of green light / green light is reflected;

Question 26

Draw a graph to show the effect of increasing light intensity on the rate of photosynthesis. [1 mark]

Answer 26

k

Question 27

Explain one way of directly measuring the rate of photosynthesis. [2 marks]

Answer 27

a. production of oxygen (which is a by-product of photosynthesis);
b. uptake of carbon dioxide (as carbon dioxide used as raw material for photosynthesis);