CAP 4 bio questions Flashcards
describe the structure of DNA (5 marks)
- polymer of nucleotides
- each nucleotide formed from deoxyribose a phosphate group and a nitrogenous base
- phosphodiester bonds between nucleotides
- double helix held by hydrogen bonds
- hydrogen bonds between adenine, thymine, and cytosine, guanine
name and describe five ways substances can move across the cell surface membrane into a cell (5 marks)
- simple diffusion of small non polar molecules down a concentration gradient
- facilitated diffusion down a concentration gradient via carrier protein
- osmosis of water down a water potential gradient
- active transport against a concentration gradient via a protein carrier using ATP
- co transport of 2 different substances using a carrier protein
contrast the structure of the two cells visible in the electron micrographs shown in figure 14 (5 marks)
- magnification figures show A is bigger than B
- A has a nucleus whereas B has free DNA
- A has a mitochondria whereas B does not
- A has a Golgi body whereas B does not
- A has no cell wall whereas B has a murein cell wall
other than those stated, suggest two variables the student should have kept constant in this investigation (1 mark)
- mass of woodlice
- volume of soda lime
describe how the student used the apparatus in figure 1 to reset the drop of coloured liquid to the right hand end of the tubing (2 marks)
- open the 3 way tap
- push the syringe down
the student also set up a control experiment
suggest a suitable control experiment and explain why it was necessary (2 marks)
- no woodlice and all other conditions the same
- to show that woodlice are causing the drop to move
using figure 3, what can you conclude about the relationship between:
the percentage of light absorbed and the rate of photosynthesis and the colour of light and the rate of photosynthesis (2 marks)
- Percentage of light absorbed at each wavelength correlates with rate of photosynthesis
- increased rate of photosynthesis with blue and red light and lower lower with green light
give three environmental factors that should be controlled when measuring the rate of photosynthesis in this investigation (2 marks)
- concentration of carbon dioxide
- light intensity
- temperature
describe how the products of the light dependent reaction are used in the light independent reaction to produce triose phosphate (3 marks)
- ATP and reduced NADP
- ATP provides energy
- GP reduced to triose phosphate
molasses is a solution obtained from beet plants. the sugars present in molasses are sucrose, glucose and fructose (1 mark)
2
a student used the biochemical test for reducing sugars on a clear sample of molasses
Describe the biochemical test for a reducing sugar
Explain the result expected from the test on the sample of molasses (3 marks )
- heat with Benedict’s reagent
- red precipitate
- because glucose is a reducing sugar Explain
use your understanding of osmosis to explain why the air pressure in the tube increased (3 marks)
- molasses has a lower water potential
- water moves in across a partially permeable bladder
- decreased air volume
The scientist observed that the air pressure inside the tube increased by 160kpa compared with 800kpa in the first investigation
suggest the change the scientist made to the molasses to cause this smaller increase in air pressure (2 marks)
- diluted molasses
- used 1 in 5 molasses to water
describe the appearance and behaviour of chromosomes during prophase and during anaphase of mitosis (4 marks)
- in prophase chromosomes continue to condense
- chromosomes become visible
- chromosomes attach to spindle
- centromeres divide
complete the word equation used to determine each mitosis index in figure 4 (1 mark)
mitotic index = number of cells in mitosis + total number of cells
the scientist used data from figure 4 to calculate a correlation coefficient. the scientist then used a statistical test to determine the probability associated with the value of r. r= -0.98 (P<0.05)
- strong significant negative correlation
- because probability of correlation occurring by chance is less than 5%
- reject null hypothesis
what can you conclude about the effect that distance from the root tip has on the proportion of cells in different stages of the cell cycle (3 marks)
- larger proportion of cells in mitosis closer to tip
- more cells in interphase further from tip
- no cells in mitosis after 2mm
give three structural difference between an mRNA molecule and a tRNA molecule (3 marks)
mRNA
1. has codons
2. no hydrogen bonds
3. no amino acid binding site
tRNA
1. has anticodons
2. has hydrogen bonds
3. has amino acid binding site
the amino acids coded by this mRNA base sequence form part of the enzymes active site
- name the type of mutation that occurred to produce the mutated gene
- give the change in DNA caused by this mutation
- explain the effect this mutation will have on the function of the enzyme (4 marks)
- substitution
- guanine to thymine
- no change in amino acid
- so no change in primary structure
suggest and explain why the results for variety D are different from the results for variety E (2 marks)
- More PPO in E
- so more enzyme substrate complexes form
