AQA A LEVEL BIOLOGY Paper1 Exam 2023/2024, Exams of Biology

Download AQA A LEVEL BIOLOGY Paper1 Exam 2023/2024 and more Exams Biology in PDF only on Docsity! 1 [Date] AQA A LEVEL BIOLOGY Paper1 Exam 2023/2024  What is the function of the cell membrane? - Correct answer To control what enters and leaves the cell, acts as a barrier between the cell and its environment.  What structural feature of the cell membrane allows substances to enter/leave? - Correct answer Partially permeable  What is the fluid mosaic model? - Correct answer States that a membrane is a fluid structure (because phospholipids are constantly moving) with a "mosaic" of various proteins embedded in it  Describe the structure and function of phospholipids. - Correct answer Hydrophilic head and hydrophobic tail, arranged in a bilayer (heads face outwards, tails face inwards). Lipid-soluble substances only allowed to pass through.  What is the function of cholesterol in the CSM? - Correct answer Make phospholipids pack more closely together, restricting the movement of the phospholipids, making the membrane less fluid/more rigid.  What is simple diffusion? - Correct answer The (passive) movement of particles from an area of high concentration to an area of low concentration.  What is facilitated diffusion? - Correct answer The passive movement of a large/charged particle down its concentration gradient through a carrier/channel protein.  What is the process of facilitated diffusion using a carrier protein? - Correct answer Large molecule binds to a carrier protein in membrane.  Protein changes shape.  Protein releases the large molecule on the opposite side of the membrane. 2 [Date]  What is the process of facilitated diffusion using a channel protein? - Correct answer Channel proteins form pores in membrane.  Charged particles can diffuse down their concentration gradients to the opposite side of the membrane.  What are the factors affecting simple diffusion? - Correct answer Concentration gradient, thickness of exchange surface and surface area.  What are the factors affecting facilitated diffusion? - Correct answer Number of transport proteins and strength of gradient.  What is osmosis? - Correct answer Diffusion of water through a partially permeable membrane from an area of high water potential to an area of lower water potential.  What are the factors affecting osmosis? - Correct answer Water potential gradient.  Thickness of exchange surface.  Surface area of exchange surface.  Outline a method for RP3 (investigation of osmosis using potato chips). - Correct answer Produce a series of dilutions from 1M sucrose solution (of a variety of different concentrations, 0M, 0.2M, 0.4M, 0.6M, 0.8M, 1M).  Use a cork borer to cut potatoes into identically-sized chips.  Blot them dry with a paper towel and measure the mass of each using a mass balance.  Place one chip into each of the sucrose solutions.  Put the test tubes into a water bath at 30°C for 20 minutes.  Take them out and reweigh the mass of the chips.  Calculate the %change in mass for each chip.  What is active transport? - Correct answer The active process of moving molecules from an area of low concentration to an area of high concentration using ATP.  Name one type of carrier protein and describe how it works. - Correct answer Co- transporters. 5 [Date]  Cell wall (plants) - Correct answer Usually made of cellulose (chitin, fungi).  Support cells and prevents them from changing shape.  Cell vacuole (plants) - Correct answer Found in cytoplasm.  Contains cell sap.  Membrane surrounding this is called the tonoplast.  Maintains pressure inside the cell, keeping cell rigid/stops wilting.  Prokaryotic cells - Correct answer Smaller and simpler than eukaryotic cells.  Plasma membrane - Correct answer Made of lipids and proteins.  Controls movement of substances in/out of cell.  Cell wall - Correct answer Made of murein (glycoprotein).  Capsule (slime) - Correct answer Protects the bacteria from attack by cells of the immune system.  Flagellum - Correct answer Rotates to make the cell move.  Viruses - Correct answer Acellular.  Invade and reproduce inside the cells of other organisms.  What is magnification? - Correct answer How much bigger the image is that the specimen.  What is resolution? - Correct answer The ability of the microscope to distinguish between two points that are close together.  Light/optical microscopes - Correct answer Uses light. 6 [Date]  Max resolution of 0.2micrometers  Max magnification of x1,500  Electron microscopes - Correct answer Use electrons.  Vacuum only so no living specimen.  Max resolution of 0.0002micrometers  Max magnification of x1,500,000  TEM - Correct answer Uses electromagnets to focus a beam of electrons through the specimen.  Thin specimen only.  SEM - Correct answer Scans a beam of electrons across the specimen.  3-D image.  Can be used on a thick specimen - but lower resolution than TEM.  What is the process of cell fractionation? - Correct answer 1 Homogenisation - Play cells in ice-cold, isotonic, buffer solution and grind up in a blender.  2 Filtration - filter the solution through a gauze to separate out any debris.  3 Ultracentrifugation - pour the cell fragments into a tube and put the tube into a centrifuge. Spin at a low speed. The heaviest organelles (nucleus) will fall to the bottom and will form the pellets. The rest of the organelles stay suspended in the supernatant. The supernatant is drained off poured into another tube and spun again at a higher speed. The heaviest organelles (mitochondria) will fall to the bottom, forming a pellet. The process repeats.  3.4.4 Genetic Diversity and Adaptation - Correct answer  What is an allele? - Correct answer Different versions of a gene.  What is genetic diversity? - Correct answer The number of different alleles of genes in a species or population. 7 [Date]  How is genetic diversity increased? - Correct answer Mutations in DNA.  Gene flow.  What allows natural selection to take place? - Correct answer Genetic diversity.  What is a genetic bottleneck? - Correct answer An event that causes a big reduction in a population.  What are the effects of a genetic bottleneck? - Correct answer Reduces the number of different alleles in the gene pool so reduces genetic diversity.  What is a type of genetic bottleneck? - Correct answer The founder effect.  Describes what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool.  What is the effect of natural selection? - Correct answer Increases advantageous alleles in a population.  Natural selection leads to... - Correct answer Adaption  Types of adaptations: - Correct answer Structural, physiological, behavioral  What is directional selection? - Correct answer Favours individuals at one end of the phenotypic range.  What is stabilising selection? - Correct answer Selection favouring average individuals.  RP6 (aseptic techniques). - Correct answer Aseptic techniques - preventing contamination by unwanted microorganisms, regularly disinfect work surface, use sterile equipment, wash hands with soap and water. 10 [Date]  What is a protein made up of? - Correct answer Amino acids (monomers).  What is the general structure of an amino acid? - Correct answer (NH2)(R) - C - (H) (COOH)  How are two amino acids joined? - Correct answer Peptide bond formed by a condensation reaction (molecule of water eliminated).  What is the primary structure of a protein? - Correct answer Sequence of amino acids in the polypeptide chain.  What is the secondary structure of a protein? - Correct answer Hydrogen bonding forms between amino acids and so make it coil or fold into alpha helix or beta pleated sheet.  What is the tertiary structure of a protein? - Correct answer More bonds form (hydrogen and ionic bonds). Forms final 3D structure (for single chain proteins).  What is the quaternary structure of a protein? - Correct answer Made up of several different polypeptide chains held together by bonds.  What are the different functions of proteins? - Correct answer Structural proteins. Transport proteins.  Antibodies. Enzymes.  Outline a method for the biuret test. - Correct answer Add a few drops of NaOH solution to the test sample. Add some copper(||) sulphate solution. If the protein is present the solution turns purple if there is no protein the solution will stay blue.  What is an enzyme? - Correct answer A biological catalyst. Catalyses metabolic reactions. 11 [Date]  How do enzymes work? - Correct answer They lower the activation energy to speed up the rate of reaction.  Describe the 'lock and key' model. - Correct answer This is where the substrate fits into the enzyme in the same way the key fits into a lock.  Describe the 'induced fit' model. - Correct answer The substrate doesn't only have to be the right shape to fit the active site but also has to make the active site change shape in the right way.  Factors affecting enzyme activity: - Correct answer Temperature, pH, enzyme concentration, substrate concentration.  How does a competitive inhibitor work? - Correct answer A competitive inhibitor is of similar shape to the substrate, and is complementary to the active site. They attach to the active site before the substrate thus blocking it, but interact weakly so they dont stay permanently - compete for active site.  How does a non-competitive inhibitor work? - Correct answer They bind to another binding site other than the active site and alter the shape of the enzyme so the substrate can no longer bind to the active site.  3.1.2 Carbohydrates - Correct answer  What are the monomers that make up carbohydrates? - Correct answer Monosaccharides.  How are two monosaccharides joined? - Correct answer By a condensation reaction, forming a glycosidic bond (eliminating a water molecule). 12 [Date]  Maltose is made up of... - Correct answer 2 glucose molecules.  Lactose is made up of... - Correct answer Glucose and galactose.  Sucrose is made up of... - Correct answer Fructose and glucose.  What are the two isomers of glucose? - Correct answer Alpha and beta glucose.  How does alpha-glucose differ from beta-glucose? - Correct answer In alpha-glucose, the hydroxyl group is placed below the plane of the ring of carbons; in beta-glucose, the hydroxyl group is placed above the plane of the ring.  Outline a method for the Benedict's test. - Correct answer Add Benedict's reagent to a sample and heat it in a water bath has been brought to the boil. If the test is positive it will form a coloured precipitate.  (Blue -> brick red)  could filter the precipitate and weigh it to compare amount of reducing sugar.  For non reducing sugar:  Add dilute hydrochloric acid and carefully heat in a water bath that's been brought to the boil.  Neutralise with sodium hydrogen carbonate.  Carry out Benedict's test as normal.  What is the structure of starch? - Correct answer Contains two polysaccharides of alpha glucose (amylose and amylopectin).  Amylose - Long unbranched chain of alpha glucose. Coiled, compact, good for storage.  Amylopectin - Long branched chain of alpha glucose, Sidebranches allow enzymes to reach the glycosidic bonds easily so glucose released quickly.  Insoluble in water so doesn't affect water potential of cell.  What test can be used for starch? - Correct answer Iodine test. 15 [Date]  What is the general pattern of blood circulation in a mammal? - Correct answer Right side of heart:  Heart, pulmonary artery, lungs, pulmonary vein, heart. Back to left side.  Left side:  Heart, aorta, body (renal artery, renal vein) vena cava, heart. Back to right side.  Which two words describe the mammalian circulatory system? - Correct answer Closed, double.  What is the function of the coronary arteries? - Correct answer Supply oxygenated blood to the heart muscle.  How does the structure of the heart relate to its function? - Correct answer AV valves, prevent backflow of blood from ventricles to atria.  SL valves, prevent backflow of blood from arteries to ventricles.  Left has thicker muscular wall, generates high blood pressure for blood to travel around body.  Right has thinner muscular wall, generates lower blood pressure, blood travels to lungs, high blood pressure would damage alveoli.  Describe the structure and function of arteries. - Correct answer Carry blood from heart to rest of body.  Thick muscle layer, to maintain high pressure & contracts to move blood along.  Elastic tissue layer, to stretch and recoil.  Smooth endothelium, to reduce friction.  Narrow lumen, to increase pressure.  Describe the structure and function of arterioles. - Correct answer Division of arteries to smaller vessels, direct blood flow to capillaries.  Thicker muscle layer than arteries.  Constrict to reduce blood flow (narrows lumen).  Dilate to increase blood flow (widens lumen).  Describe the structure and function of veins. - Correct answer Take deoxygenated blood back to heart under low pressure (except for pulmonary vein). 16 [Date]  Wider lumen, little muscle/elastic tissue.  Contain valves to stop backflow of blood.  Contraction of skeletal muscles maintains blood flow in veins.  Describe the structure of capillaries and the importance. - Correct answer Capillary wall is one cell thick, short diffusion pathway for rapid diffusion.  Capillary bed made of large network of branched capillaries, large surface area for rapid diffusion.  Narrow lumen, reduces flow rate so more time for diffusion.  Pores in walls between cells, allows substances to escape for diffusion.  What is tissue fluid? - Correct answer A watery substance containing glucose, amino acids, oxygen, and other nutrients. It supplies these to the cells, while also removing any waste materials.  How is tissue fluid formed? - Correct answer At arteriole end of capillaries.  Higher blood pressure inside capillaries than tissue fluid pressure. Forces fluid out of capillaries. Large plasma proteins remain in capillaries.  How is tissue fluid returned to the circulatory system? - Correct answer At venule end of capillaries.  Hydrostatic pressure reduces as fluid leaves capillary. Increased concentration in plasma proteins lowers wp of capillary. Water re-enters capillary by osmosis. Excess water taken up by lymph system and returned to circulatory system.  Valves are... - Correct answer One-way opening for blood to flow through in veins.  Outline the cardiac cycle. - Correct answer Atrial systole - atria contract, volume decreases and pressure increases inside the atria, AV valves open, blood is pushed into ventricles.  Ventricular systole - ventricles contract, volume decreases and pressure increases, SL valves open & AV valves close, blood pushed through arteries.  Diastole - ventricles and atria relax, SL valves close, blood fills atria from veins, flows passively to ventricles as AV valves open. 17 [Date]  How can an atheroma result in a heart attack? - Correct answer Narrows coronary arteries. Restricts blood flow to heart muscle. Not as much oxygen supplied to heart. Anaerobically respires, not as much ATP produced, not enough energy, lactate produced, damages heart.  What is the main job of the xylem? - Correct answer Transports water and mineral ions in plants. (Substances move up the plant).  How does water move up the plant? - Correct answer Using cohesion and tension.  Water evaporates from the leaves at the top of the xylem, this creates tension, pulls more water to the leaf, cohesion allows water molecules to be pulled up as a column. Water enters stem through roots.  What are some adaptations of the xylem? - Correct answer Elongated cells with no end walls to form a continuous column.  Hollow so slows water flow.  Thick cells walls and rigid for stability.  Narrow lumen for increased cohesion.  Waterproof so no evaporation.  What is transpiration? - Correct answer The loss of water from a plant by evaporation.  What is the main function of the phloem? - Correct answer Transports organic substances like sugars up and down the plant.  What are some adaptations of the phloem? - Correct answer Sieve tube elements have no nucleus and few organelles. Companion cells carry out living functions for the sieve cells.  What is translocation? - Correct answer The movement of solutes to where they're needed in a plant. Moves solutes form source (high conc) to sink (low conc).