the one Flashcards
MCQ 1-5
1-C
2-C
3-C
4-A
5-D
MCQ 6-10
6-A (TEM>SEM)
7-B
8-C
9-D
10-D
MCQ 11-15
11-C
12-C
13-D
14-A
15-A
2 other roles of mitosis (2)
Repair by replacing damaged cells with identical healthy cells.
Tissue repair
Development of body plans
Clonal expansion
Why do plants reproduce asexually by mitosis instead of meiosis
Mitosis produces 2 genetically identical daughter cells, whereas meiosis produces 4 genetically different daughter cells.
Mitosis ensures all daughter plants receive advantageous/desirable alleles.
Why do bacteria undergo binary fission instead of mitosis (2)
Bacteria have simplified cytoskeleton with no centrioles
So bacteria unable to produce spindle fibers needed to pull chromosomes to opposite poles of the cell
Bacteria have no nucleus
Bacteria have circular DNA, not linear
Advantages and disadvantages of cloning in plants and animals (6)
Advantages:
Cloned plants can be produced non-seasonally / all year round so that supply is still reliable
Guarantees quality of crop and livestock yield / genetic modifications can be carried to the next generation
Can be used when sexual reproduction is not possible / rare species
More cloned plants can be produced more quickly than from germinating seeds.
Desirable alleles always passed on to offspring.
disadvantages of cloning in plants and animals (6)
Low hybrid vigour / increased chance of inbreeding depression
Increased chance of homozygous recessive genotypes could lead to genetic disorders / health issues (e.g. large offspring syndrome in cloned cows)
Cloned plants have low genetic diversity so more susceptible to the same environmental change / selection pressure
Success rate of SCNT is still very low
Ethical issues due to reduced lifespan of clones
Some people may be against the consumption of cloned crops/animals
Chromosome frog q
1024 (2)
Dependent and independent variables for hydrogen peroxide experiment (2)
Independent variable is concentration of hydrogen peroxide
Dependent variable is volume of O2 produced
Calculate the initial rate of activity at 2 a.u.
0.117 cm3 per second or round to 0.18 cm3 per second
How do you produce 8 a.u. Solution (2)
Serial dilutions with dilution factor of 0.4
Use a measuring cylinder to measure 4cm3 of 20 a.u. and 6cm3 of distilled water. Mix and stir to produce a homogenous solution.
Standard Deviation: (2)
2.3
Comment on the repeatability of the results (2)
the higher the standard deviation, the lower the repeatability.
At 2 a.u. the standard deviation is at most 1, so highly repeatable.
But at 20 a.u. the standard deviation increases up to 9.0, so has low repeatability at this concentration
Why was potato used instead of liver (2)
Potato has less catalase, so less O2 lost before delivery tube can be connected
Potatoes will give off the same volume of gas in a longer time, so the percentage uncertainty using potatoes is less than using liver
Suggest an improvement to method (1)
Take the cylinders from the same potato
Suggest 2 reasons why volume of O2 measured may be inaccurate (2)
O2 is a soluble gas so will dissolve in the water of the water trough
Oxygen is also used up by respiration in potato cells.
Explain the graph shape for 20 a.u. (3)
At 20 a.u the H2O2 substrate concentration is high. So high frequency of collisions between enzyme catalase and H2O2 substrate.
So high rate of formation of enzyme substrate complex when substrate enters complementary active site. So high initial rate of product formation
As reaction progresses, H2O2 used up, so substrate concentration decreases. Substrate concentration is limiting factor, and rate of reaction decreases.
More oxygen produced at 20 a.u because there are more moles of H2O2 at 20 a.u for same given volume.
Suggest another means of immobilizing enzyme (1)
Membrane separation by microencapsulation
Enclose in a partially permeable membrane
Suggest why activity of immobilized enzymes is reduced (2)
Shape of active site changed, so no longer complementary to shape of substrate molecule
Enzyme not able to mix with the substrate molecules fully, so lower rate of successful collision between enzyme and substrate
Delay with entrapment as reactants must diffuse into / products must diffuse out of the matrix
Why is immobilized yeast more expensive than immobilized invertase? (1)
Yeast is living so may need correct conditions and nutrients to stay alive
immobilised yeast would still have to undergo downstream processing afterwards
Lactose experiment (6)
practically carried out,
control variables are clearly identified,
processing of results is explained
common answers included Benedict’s test, colorimetry, repeating the experiment to calculate means, and using a t-test to compare them.
Action of mucous membranes: (2)
Goblet cells secrete sticky mucus which trap virus
Ciliated epithelial cells waft mucus entrapped pathogens up and out of airways.
Antibody vs Fab Fragment - 2 similarities and 1 difference (3)
Sim 1: Both have 2 variable region binding site to bind to separate 2 pathogenic antigens.
Sim 2: Both have disulphide bridges / hinge region joining the polypeptide chain subunits together.
Dif 1: Fab has 4 polypeptide chains of the same length, whereas antibody has 2 long heavy chains and 2 light short chains / Fab has no heavy chains
