AQA A Level Biology 2022 Past Paper 1: Exercises and Questions, Exams of Advanced Education

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AQA A level Biology 2022 Past

Paper 1

1. Describe the structure and function of the nucleus - Structure:
2. Nuclear envelope and pores
3. Chromosomes/chromatin 3)Nucleolus Function: (2 max)
4. Stores genetic information/material for polypeptides (production)
5. DNA replication
6. Production of mRNA/tRNA OR Transcription occurs
7. Production of rRNA/ribosomes 1.2) Name the main polymer that forms the following cell walls - Plant cell wall : cellulose Fungal cell wall: Chiten 1.3) Suggest one reason the scientists used biomass instead of the number of individuals of each plant species when collecting data to measure diversity - individual organisms could not be separated/identified OR too time-consuming OR too small/numerous to count individuals 1.4) - 0.7-0. 2.1) C difficile is a bacterial species that causes disease in humans

Antibiotic resistant strains of C. diffcile have become a common cause of infection acquired when in hospital Explain how the use of antibiotics has led to antibiotic- resistant strains - 1) Some bacteria have alleles for resistance (due to mutation))

2. (exposure to) antibiotics is the selection pressure OR Non resistant bacteria die OR resistant bacteria survive/reproduce
3. more antibiotics used in hospital (compared with elsewhere) OR Patients have weakened immune system 2.2) Name another disaccharide formed from two glucose molecules - maltose 2.3) Scientists investigeted the effect of trehalose on the growth rate of C. difficile. They grew populations of non-resistantand antibiotic resistant C. difficle on separate agar plates with: -No carbohydrate added

• Trehalose added They measured the growth rate of the C. dificle Describe how the scientists could use aseptic techniqies to transfer 0.3cm&3 of C-diffucule in liquid culture from a bottle on to an agar plate - 1) Wash hands with soap/ disinfect surfaces

2. use sterile pipette/syringe 3 (remove bottle lid and) flame neck of bottle
3. remove the lid of (agar) plate at an angle
4. place pipette/spreader into disinfectant (immediately after use)
5. Use sterile spreader/inoculating loo
6. Work close to upward air movement (convection current)

2.4) Use figure 2 to evaluate whether more trehalose in the diet could be a factor in the increased number of antibiotic resistant C. difficile infections - For

1. Resistant bacteria grow faster with trehalose
2. So resistant bacteria (likely to) increase in frequency in the population/people
3. Resistant bacteria (likely to) outcompete non-resistant bacteria Against:
4. In laboratory not in people
5. other disaccharides (in the diet) might affect bacteria
6. Other bacterial species (in the body) might affect bacteria
7. no stats test to see if difference/increase is significant
8. no data for both resistant and non- resistant bacteria growing together
9. no data for different concetrations of trehalose 3.1) Give two features of all prokaryotic cells that are not features of eurkaryotic cells - 1) smaller 70S ribosomes no membrane bound organelles (or example mitochondria) circular loop of DNA ( in cytoplasm) DNA free in cytoplasm DNA not associated with histones/proteins Murien/peptidoglycan in cell wall 3.3) The amino acids on side of each AP helix have hydrophobic properties The amino acids on the opposite side of each helix have hydrophilic properties Suggest how these properties of the APS allow them to become positioned across the membrane and make a channel through which ions can pass - 1) Hydrophobic sides next to face/ fatty acid tails or hydrprobic side next to/faces hydrophonic part of phospholipid bilayer

2. Hydrophilic side allows ion movement through or hydrophilic sides form a channel 3.4) Maths q - 3.5) The APs damage prokaryotic cells but do not damage the eukaryotic cells in the organisms that produce them Prokaryotic cell membranes do not contain cholesterol Assess why the APs do not damage the eukaryotic cells of the organisms that produce them - 1) Cholesterol stabilizes the cell surface membrane OR cholesterol restricts the movement of molecules/phospholipids/fatty acids (making up the membrane) or holds together for restricts movement
3. (So) APs do not make channels in (eukaryotic) membranes or (So) APS cannot enter the eukaryotic membrane 3.6) Scientists observed these APs on prokaryotes using a transmission electron miscroscope. They strained the APs using a monoclonal antibody with gold attached to it. Suggest how these tecniques allowed observation of APs on prokaryotes - 1) Antibody binds to AP
4. (as antibody/tertiary structure is ) complementary (to AP)
5. Gold interacts with electrons in TEM
6. TEM used as it has a high resolution 4.1) Describe viral replication - 1) Attachment proteins attach to receptors
7. (viral) nucleic acid enters cell (eg rna/dna/genetic material for nucleic acid)
8. Nucleic acid replicated in cell OR reverse transcriptase makes DNA from RNA

4. Cell produces (viral) proteins/capsid/enzymes
5. virus assembled and released (from cell) 4.2) Mitosis vs Binary Fission - Replication of linear DNA- only mitosis Replication of circular DNA - binary fission only produces 2 daughter cells- both mitosis and binary fission produces 4 daugher cells- neither happens in prokaryotic cells- binary fission happens in eurkaryotic cells - mitosis 4.3) Complete figure 6 to show the chromosomes inside the daughter cells formed after the second meiotic division - NA 4.4) A student concluded that there were more mothers of age >37 with MM2 errors than with MM errors Using figure 7 and suitable calculations show why this conclusion is not valid - 197 with MM1 and 83/82.8 with MM
6. Two enzymes P and Q, are proteins with Quaternary structure which catalyse the same reaction, but they have different amino acid sequences 5.1) Define the quanternary structure of a protein - 1) more than 1 polypeptide 5.2) Explain how two enzymes with different amino acid sequences can catalyse the same reaction - 1) (Both) active sites have similar/identical tertiary structures or (both) active sites have identical amino acid sequences
7. (so) form enzyme-substrate complexes (with the same substrate)

5.3) Describe what the scientists should place in the control tubes of the investigation - 1) Same volume of (each) buffer/pH solution

2. same concentration/mass of substrate (at start)
3. same concentration/mass of denatured enzyme 5.4) Give 3 conclusions you can make from figure 8 - 1) Both/P and Q (are) active at pH 8.
4. P is (equally/most) active at both pHs OR Q is less active than P at both pHs OR P is not affected by pH (change) OR Q is affected by pH (change)
5. Q is denatured/not active at pH 7. OR Q is less active than the control at pH 7.
6. Reaction occurs without enzymes(s) OR Reaction occurs in the control
7. All (reactions) reach same end (point) OR Substrate is not used up 6.1) Explain the rate of transpiration between 5 am and midday shown in figure 9 - 1) (Rate of) transpiration/evporation increases due to increased temperature OR (Rate of) transpiration/evaporation increases due to increased light intensity OR (Rate of) transpiration/evaporation increases due to increased wind/air movement
8. (so) increased kinetic energy (causing more water loss)

3. Stomata open (at sunrise/after 5am) allowing gas exchange
4. (Some) stomata close at midday/after 11am (reducing transpiration) 6.2) Maths - 0.8-0.75 / 0.75 x100=6.667-6.7% 6.3) Describe an experiment that you could do to investigate whether the mangrove root cells have a lower water potential than sea water - 1) Record mass/length before and after
5. Place in sea water for (specificied/equal) time
6. Method to remove surface water
7. Increase in mass/length shows cells have lower water potential OR Increase in mass/length shows water has been absorbed by osmosis 7.1) Complete Table 3 to give three differences between DNA molecules and tRNA molecules - 1) Deoxyribose v ribose
8. Double stranded v single stranded
9. Many nucleotides v few
10. Thymine base v uracil base
11. Linear v clover leaf (strucutre)
12. Does not bind to amino acid v does bind to amino acid
13. No exposed bases v anticodon 7.2) The scientists broke open the cells to produce a suspension of cell contents Describe how the scientists would remove large orgaelles from this suspension of cell contents - 1) Use centrifuge/centrifugation at slow/low/increasing speed
14. Large/dense organelles (removed) in (first/early) pellet OR less dense organelles (removed) in supernatant

7.3) Explain the position of the bands of ribosomes in tubes A and B in figure 10 - Tube A : 1)(ribosomes bound to) rough endoplasmic reticulum

2. Are denser/heavier so move further down Tube B:
3. (only free ribosomes because) membrane/phospholipids/endoplasmic reticulum dissolved (by detergent) 8.1) To observe the fish gills with the optical microscope, the scientists used two different stains. The first stain binds to DNA; the second stain binds to the red blood cells. Explain why a second stain would be needed to stain the red blood cells. Suggest which molecule the stain could to in the red blood cells - Explaination - (red blood cells) do not have nucleus/DNA Molecule: Haemoglobin 8.2) Maths - 8.3) The damage to the gills causes uncontrolled cell division in the cells around the capillaries in the gill filaments Other than SA:V ratio, describe one way this uncontrolled cell division changes the gills, as shown in Figure 11 Explain how this difference would affect gas exchange - Difference: 1)more cells (between water and capillary/blood) OR wider/thicker filament/lamella Explaination: 2)longer diffusion pathway/distance

3. (so) slower gas exchange OR (so) slower rate of diffusion 8.4) Use Figure 12 to complete Table 5 to show two differences between the circulation of blood in fish and the circulation of blood in a mammal - Difference 1: Fish- 2 chambers Mammal- 4 chambers Difference 2: Fish-Blood does not return to heart after being oxygenated Mammal- Blood returns to the heart after being oxygenated Difference 3: Fish- single circulation Mammal- double circulation Difference 4: One vein (carrying blood towards the heart) Mammal: two veins (carrying blood towards heart) Difference 5: Fish- Blood reaching blood capillaries at low(er) pressure Mammal - Blood reaching blood capillaries at high(er) pressure Difference 6: Fish- one artery (carrying blood away) Mammal- two arteries (carrying blood away) 9.1) Describe the transport of carbohydrates in plants - 1) Sucrose actively transported into phloem cell OR Sucrose is co-transported/moved with H+ into phloem (cell)

2. (By) companion/transfer cells
3. Lowers water potential (in phloem) and water enters (from xylem) by osmosis 4)( Produces) high(er) hydrostatic pressure
4. Mass flow to respiring cells
5. Unloaded/removed (from phloem) by active transport 9.2) Compare and contrast the strucure of starch and the structure of cellulose - 1) Both polysarccaride OR both are made up of glucose monomers
6. Both contain glycosidic bonds (between glucose monomers)
7. Both contain carbon,hydrogen and oxygen
8. Starch has alpha glucose and cellulose has beta glucose
9. Starch is helical/coiled and cellulose is straight
10. Starch (molecule) is branched and cellulose is not/unbranched
11. Cellulose has (micro/macro) fibrils and starch does not 9.3) Describe the complete digestion of starch by a mammal - 1) Hydrolysis
12. (of) glycosidic bonds
13. (starch) to maltose by amylase
14. Maltose to glucose by maltase
15. membrane bound (maltase)