LEVEL BIOLOGY Paper 1 2022AQA A, Exams of Advanced Education

Download LEVEL BIOLOGY Paper 1 2022AQA A and more Exams Advanced Education in PDF only on Docsity! LEVEL BIOLOGY Paper 1 2022AQA A What is the function of the cell membrane? - 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? - Partially permeable What is the fluid mosaic model? - 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. - 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? - Make phospholipids pack more closely together, restricting the movement of the phospholipids, making the membrane less fluid/more rigid. What is simple diffusion? - The (passive) movement of particles from an area of high concentration to an area of low concentration. What is facilitated diffusion? - 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? - Large molecule binds to a carrier protein in membrane. Protein changes shape. Protein releases the large molecule on the opposite side of the membrane. What is the process of facilitated diffusion using a channel protein? - 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? - Concentration gradient, thickness of exchange surface and surface area. What are the factors affecting facilitated diffusion? - Number of transport proteins and strength of gradient. What is osmosis? - 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? - Water potential gradient. Thickness of exchange surface. Surface area of exchange surface. Outline a method for RP3 (investigation of osmosis using potato chips). - 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? - 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. - Co-transporters. Bind two molecules at once. The concentration gradient of one of the molecules is used to move the other molecule against its own concentration gradient. Prokaryotic cells - Smaller and simpler than eukaryotic cells. Plasma membrane - Made of lipids and proteins. Controls movement of substances in/out of cell. Cell wall - Made of murein (glycoprotein). Capsule (slime) - Protects the bacteria from attack by cells of the immune system. Flagellum - Rotates to make the cell move. Viruses - Acellular. Invade and reproduce inside the cells of other organisms. What is magnification? - How much bigger the image is that the specimen. What is resolution? - The ability of the microscope to distinguish between two points that are close together. Light/optical microscopes - Uses light. Max resolution of 0.2micrometers Max magnification of x1,500 Electron microscopes - Use electrons. Vacuum only so no living specimen. Max resolution of 0.0002micrometers Max magnification of x1,500,000 TEM - Uses electromagnets to focus a beam of electrons through the specimen. Thin specimen only. SEM - 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? - 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 - What is an allele? - Different versions of a gene. What is genetic diversity? - The number of different alleles of genes in a species or population. How is genetic diversity increased? - Mutations in DNA. Gene flow. What allows natural selection to take place? - Genetic diversity. What is a genetic bottleneck? - An event that causes a big reduction in a population. What are the effects of a genetic bottleneck? - Reduces the number of different alleles in the gene pool so reduces genetic diversity. What is a type of genetic bottleneck? - 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? - Increases advantageous alleles in a population. Natural selection leads to... - Adaption Types of adaptations: - Structural, physiological, behavioral What is directional selection? - Favours individuals at one end of the phenotypic range. What is stabilising selection? - Selection favouring average individuals. RP6 (aseptic techniques). - Aseptic techniques - preventing contamination by unwanted microorganisms, regularly disinfect work surface, use sterile equipment, wash hands with soap and water. 3.3.2 Gas Exchange - State the two adaptations of gas exchange surfaces. - Thin so short diffusion distance Large surface area Describe the gas exchange system in fish. - Countercurrent (blood flows through the lamellae in one direction and water flows over in the opposite direction, maintains a high concentration gradient). Water enters the fish through its mouth and passes through the gills. Each gill is made of lots of thin plates called gill filaments which are covered in lots of lamellae, which increase the surface area. Lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion. What is the quaternary structure of a protein? - Made up of several different polypeptide chains held together by bonds. What are the different functions of proteins? - Structural proteins. Transport proteins. Antibodies. Enzymes. Outline a method for the biuret test. - 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? - A biological catalyst. Catalyses metabolic reactions. How do enzymes work? - They lower the activation energy to speed up the rate of reaction. Describe the 'lock and key' model. - This is where the substrate fits into the enzyme in the same way the key fits into a lock. Describe the 'induced fit' model. - 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: - Temperature, pH, enzyme concentration, substrate concentration. How does a competitive inhibitor work? - 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? - 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 - What are the monomers that make up carbohydrates? - Monosaccharides. How are two monosaccharides joined? - By a condensation reaction, forming a glycosidic bond (eliminating a water molecule). Maltose is made up of... - 2 glucose molecules. Lactose is made up of... - Glucose and galactose. Sucrose is made up of... - Fructose and glucose. What are the two isomers of glucose? - Alpha and beta glucose. How does alpha-glucose differ from beta-glucose? - 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. - 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? - 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? - Iodine test. Add iodine dissolved in potassium iodide solution to the test sample. If starch is present the sample changes from brown-orange to a blue-black colour. Describe the structure of glycogen. - Similar to amylopectin. Lots of sidebranches so glucose can be released quickly. Very compact molecule so good for storage. What is cellulose used for? - Cell walls. (Structural support) Describe the structure of cellulose. - Straight cellulose chains made of beta glucose. Chains linked together by hydrogen bonds to form strong fibres called microfibrils. 3.3.4 Mass Transport - What is haemoglobin? - Quaternary, globular protein What is haemoglobin made up of? - 4 polypeptide chains. One haem group per chain, contains iron ion. How many oxygen molecules can hemoglobin carry? - 4 Haemoglobin has a ____ affinity for oxygen - High. What does haemoglobin form when it binds to oxygen? - Oxyhaemoglobin. What is the equation for the reaction between Hb and O2? - Hb + 4O2 —> HbO8 Describe the structure of capillaries and the importance. - 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? - 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? - 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? - 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... - One-way opening for blood to flow through in veins. Outline the cardiac cycle. - 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. How can an atheroma result in a heart attack? - 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? - Transports water and mineral ions in plants. (Substances move up the plant). How does water move up the plant? - 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? - 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? - The loss of water from a plant by evaporation. What is the main function of the phloem? - Transports organic substances like sugars up and down the plant. What are some adaptations of the phloem? - Sieve tube elements have no nucleus and few organelles. Companion cells carry out living functions for the sieve cells. What is translocation? - The movement of solutes to where they're needed in a plant. Moves solutes form source (high conc) to sink (low conc). Explain the mass flow hypothesis. - 1 translocation, at the source, high conc of solute, active transport of solutes from companion cells to sieve tube elements, wp lowered in sieve tube elements so water enters by osmosis from xylem/companion cells, pressure increases inside ste at source end. 2 at the sink, low conc of solute, solutes removed to be used up, wp increases inside sieve tube so water leaves by osmosis, pressure decreases inside sieve tube elements. 3 mass flow, pressure gradient from source to sink, solutes pushed from source to sink, solutes used/stored at sink. 3.4.6 Biodiversity - Define biodiversity. - The variety of living organisms in an area. What is a habitat? - Place where an organism lives. What is a community? - All the populations of different species in a habitat. How is biodiversity reduced? - Agricultural practices. Name some agricultural practices. - Woodland clearance. Hedgerow removal. Pesticides. Herbicides. Monoculture.