AQA A Level Biology Paper One Revision: Key Concepts and Questions, Exams of Biology

Download AQA A Level Biology Paper One Revision: Key Concepts and Questions and more Exams Biology in PDF only on Docsity! AQA A Level Biology Paper One Revision AQA A Level Biology Paper One Revision Questions and Answers (119 Terms) Updated 2024-2025. What's the type of bond between glycerol and a fatty acid in a phospholipid? - Answer: Ester bonds How would a fatty acid be unsaturated? - Answer: If it contained a double bond between adjacent carbon atoms in the hydrocarbon chain. 1 AQA A Level Biology Paper One Revision Suggest one advantage of the different percentage of cholesterol in red blood cells compared with cells lining the ileum. - Answer: Red blood cells would be free in blood, and not supported by other cells which ensures that cholesterol will maintain its shape. E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why. - Answer: - Cells are unable to change shape due to the cell having a cell wall. - This makes the cell rigid since it is made of murein. Explain the difference between starch molecules and cellulose molecules - Answer: - Starch formed w a glucose, Cellulose w b glucose - Position of hydrogen and hydroxyl groups on carbon atom 1 are inverted. How is starch adapted for its role? - Answer: - Insoluble, meaning that it doesn't affect water potential. How is cellulose adapted for its function in plant cells? - Answer: - Long and straight chains -Become linked together with hydrogen bonds which form fibrils - Provides strength for cell wall. 2 AQA A Level Biology Paper One Revision so different amino acids code for different proteins Cutting x thin for optical microscope - Answer: For more light to pass through so a single cell can be viewed DNA has antiparallel strands Shape of nucleotides is aligned differently Enzymes with specific shapes have active sites ONLY substrates with specific shapes can bind with active site - Answer: How can nerve cells be affected by a virus? - Answer: The outside of a virus has proteins, with complementary shapes to the receptor Receptor only found on membrane of nerve cells. Advantage of programmed cell death - Answer: Prevents the replication of viruses. Prevents replications of mutations/mutations of a cell How is DNA a polymer? - Answer: It has repeating units 5 AQA A Level Biology Paper One Revision Two ways ATP is a suitable energy source - Answer: releases small amount of energy instant energy release Equation of ATP being synthesized by ADP - Answer: ADP + Pi --> ATP Why do humans synthesize a huge amount of ATP? - Answer: - It cannot be stored - Only releases a small amount of energy at a time Function of ATP - Answer: metabolic processes provide energy for muscle movement changes shapes of carrier proteins for active transport secretes cell products net yield of ATP from anaerobic respiration - Answer: 2 molecules advantage of ATP as an energy storage molecule in a cell - Answer: cannot pass out of cell releases small amount of energy 6 AQA A Level Biology Paper One Revision Advantage of mitochondria in muscle cells having more cristae - Answer: larger surface area for electron transport chain more enzymes for ATP production muscles use more ATP than skin cells How does centrifuging a culture obtain a cell-free liquid? - Answer: Heavy cells form pellets which move to the bottom of the tube when centrifuged From there the liquid can be removed. One function of lisosomes - Answer: break down cells What are the terms of cell fractionation? What temp should it be and what should be done at first? - Answer: break open cells to remove debris the solution MUST be cold - to reduce activity of enzymes breaking down organelles. Name two structures in a eukaryotic cell that cannot be identified using an optical microscope - Answer: ribosome endoplasmic reticulum 7 AQA A Level Biology Paper One Revision Describe and explain how centrifuging the culture allowed the scientists to obtain a cell-free liquid - Answer: Large dense cells, spinning allows pellets to move to the bottom of the centrifuge. Liquid can be removed. Lysosomes - Answer: break down food and worn out cell parts one advantage of different percentage of cholesterol in RBC compared with cells lining ileum - Answer: RBC are free in blood which means that cholesterol can maintain shape high blood pressure leads to an accumulation of tissue fluid - Answer: how tissuse fluid is formed - Answer: 2 ways pathogens cause disease - Answer: releases toxins that kills cells how does the monoclonal antibody prevent the regulatory protein from working - Answer: tertiary structure complimentary to regulatory protein binds to form complex regulatory protein is not complementary to receptor 10 AQA A Level Biology Paper One Revision the advantage of closing stomata - Answer: water is lost through stomata, closure prevents water loss, this maintains the water content of cells how does the uptake of co2 increase when stomata closes? - Answer: through the upper surface of the leaf (waxy cuticle) how would the mutation of a tumor suppressant gene result in tumor formation? - Answer: tumor suppressor would not be able to control cell division meaning that rate of cell division would be too fast. why would there be a % decrease in people vaccinated - Answer: fewer cases would be reported + fear of side effects why is a virus described as inactive - Answer: no more cells are infected, virus is not replicating advantage of cell death - Answer: prevents cell replication limitations of a TEM to investigating cell structure - Answer: cell must be dead image produced is not 3D specimen must be thin principles of a TEM microscope - Answer: electrons pass through thin specimen 11 AQA A Level Biology Paper One Revision denser parts absorb more electrons dense parts are darker electrons have short wavelength so there is a high resoloution interphase + mitosis = two genetically identical cells. how? - Answer: - dna is replicated via complementary base pairing - two identical chromatids produced - each chromatid moves to opposite ends of the cell. two structures in a eukaryotic cell which is not visible in optical microscope - Answer: ribosomes cell surface membrane how tissue fluid formed - Answer: outward pressure forces small molecules out of capilary why hydrostatic pressure falls from the arteriole end of the capilary to the venule end of the capilary - Answer: friction against capillary lining. mechanism that causes forced expiration (4) - Answer: contraction of intercostal muscles decrease in volume of chest air pushed down a pressure gradient 12 AQA A Level Biology Paper One Revision relationship between temp of water, oxygen in water + rate of ventilation - Answer: as water temp increases, oxygen conc falls and ventilation rate increases countercurrent flow and how it leads to efficient gas exchange in the gills of the fish: - Answer: water and blood flow in opposite directions maintains diffusion gradient across the whole length of the lamellae volume of water passing over gills increases if the temp of water increases. why? - Answer: increased metabolism so less oxygen is dissolved in water process which oxygen passes from an alveolus in the blood - Answer: simple diffusion structure of an amino acid - Answer: polymer of amino acids joined by peptide bonds formed by condensation primary structure in order of amino acids secondary structure is folding of polypeptide chain due to hydrogen bonds how proteins are digested - Answer: hydrolisis of peptide bonds endopeptidases break polypeptides into smaller peptide chains expopeptidases remove terminal amino acids dipeptidases hyrolisise dipeptides into amino acids 15 AQA A Level Biology Paper One Revision how mrna is produced in the nucleus of the cell - Answer: dna helicase breaks hydrogen bonds only one dna strand act as template rna nucleotides attracted to exposes bases attraction according to base pairing rule RNA polymerase joins RNA nucleotides together pre-mrna spliced to remove introns why maltose is hydrolyzed by maltase - Answer: active site is complementary to maltase ONLY maltose can bind to form an enzyme substrate complex function of coronary arteries - Answer: carry oxygenated blood to heart muscles The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why. - Answer: aorta is directly linked to heart aorta has elastic tissues aorta has stretch one advantage of capillaries are narrow - Answer: large surface area of blood in contact with walls of capillaries importance of maintaining a constant blood ph - Answer: to avoid enzymes in blood being affected by change in pH 16 AQA A Level Biology Paper One Revision this could lead to a change in shape of hemoglobin so less oxygen would be able to bind with hemoglobin how are sickle cells adapted for mass transport - Answer: very little cytoplasm so it is more easier for thick walls to resist pressure one other way in which companion cells are adapted for the transport of sugars between cells - Answer: mitochondria release energy for active transport how is a high pressure produced by translocation in the leaves - Answer: water potential becomes lower water enters phloem by osmosis increased volume of water = increased pressure comparison of facilitated diffusion and active transport - Answer: facilitated diffusion: involves channel proteins. does not use atp. down a conc gradient. active transport: only involves carrier proteins. uses atp. against a conc gradient. mass flow hypothesis for mechanism of translocation in plants - Answer: leaf sugars actively trasnported by phloem by companion cells lowers WP of sieve cell increase in pressure causes mass movement sugars used conversed in roots (stored as starch) for respiration for storage 17 AQA A Level Biology Paper One Revision allows different combination of maternal and paternal chromosomes. Phylogenetic group - Answer: grouped according to evolutionary links how is carbon dioxide converted to other substances in the light independent stage of photosynthesis? - Answer: carbon dioxide combines with RuBp produces 2 glycerate 3-phosphate GP converted to triose phosphate using reduced NADP and energy from ATP, triose phosphate converts to glucose. Primary, Secondary and Quaternary Structure of Amino Acids - Answer: - Primary structure is order of amino acids; - Secondary structure is folding of polypeptide chain due to hydrogen bonding. - Quaternary Structure is two or more polypeptide chains. reverse transcriptase - Answer: An enzyme encoded by some certain viruses (retroviruses) that uses RNA as a template for DNA synthesis. RNA polymerase - Answer: Enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription 20 AQA A Level Biology Paper One Revision Lymphocytes - Answer: A type of white blood cell that make antibodies to fight off infections mass transport in plants - Answer: The transport of water and solutes in the xylem and phloem xylem carries water source cell - facilitated diffusion of glucose into companion cell, active transport into phloem - through sieve cells (negatively charged at the top) glucose travels down phloem which travels to companion cells and then sink cells by active transport . + charged. Capsid - Answer: Outer protein coat of a virus Helper T cells - Answer: help the immune system by increasing the activity of killer cells and stimulating the suppressor T cells 21