AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS, Exams of Biology

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AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS air spaces between them = rapid diffusion, long and narrow and are packed with chloroplast the thin tissue of the leaf allows light to reach mesophyll - correct answer Name three advantages of mesophyll in the leaf stroma in the fluid filled matrix - correct answer where does the LIR occur? 100 stacked discs of thylakoids - correct answer what is the grana? chlorophyll absorbs light energy, excite electrons, move along carriers etc releasing energy, used to join ADP and pi to form ATP, photolysis of water produces protons electrons oxygen, NADP reduced by electrons - correct answer describe the light dependent reaction starting with Photolysis electron is oxidised that reduces NADP, carries out series of redox reactions along the electron transport chain that is then accepted by oxygen that is the terminal electron receptor which oxidises NADPH back to NADP - correct answer describe the electron transport chain AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS contain both DNA and RNA so proteins can be manufactured quickly, thylakoid membrane has a large SA for rapid DF and a network of proteins in the Grana to maximise the absorbance of light - correct answer name three advantages of the structure of a chloraplast CO2 combines 5 carbon ribulose-bi-phosphate to make 6 carbon molecule that is then catalysed by rubisco to create two 3 phosphate glycerate molecules that are then reduced via NADP and energy from ATP from LDR to triose phosphate that will eventually turn into glucose, NADP reformed and goes back to LDR - correct answer describe the process of the LIR phosphorylated glucose is broken down in two 3 carbon molecules called pyruvate (happens in the matrix mitochondria - correct answer what is glycolysis and where does it happen? pyruvate is decarboxylated and dehydrogenated to acetate NAD is reduced - correct answer what happens in the link reaction after Glycolysis? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS producers or lost to the atmosphere - correct answer describe the nitrogen cycle phosphates from rocks are eroded into oceans and running water that is absorbed by plants and excreted into the soil via death that then taken up by water to form new rocks - correct answer describe the phosphorus cycle algae build up on surface of water due to nitrogen from water that limits light to lower level plants that can no longer photosynthesise and die that are fed on by saprobiants that multiply and take up oxygen in the water so that O2 becomes the limiting factor and larger organsims die as a result that are also fed on by saprobiants that release toxins into the water - correct answer what is eutrophication? natural = dead decomposing plants and artificial = mined from rocks t provides nutrients to plant - correct answer what is an example of a natural and artificial fertiliser? the change of speed of direction in response to a stimulus - correct answer what is kinesis? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS response to a stimulus where the direction is determined by the stimulus itself that is moving the entire organism away or towards - correct answer what is taxis? the detectable change in the external or internal environment - correct answer what is a stimulus? IAA moves down a concentration gradient to the dark side of the shoot that then increases the growth of that side to increase more than that of the light side so the plant curves towards the light (phototrophism) ,in roots however, IAA inhibits growth and so builds up on the underside of the root so the plant can more on the top so that it bends towards gravity (gravitrophsim) - correct answer what is the base movement of IAA in plants and roots? where the active transport of H+ ions from cytoplasm into the spaces in the cell wall casuing the cell wall to become more plastic - correct answer what is the acid growth hypothesis? brain and spinal cord - correct answer What does the CNS consist of? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS provides a voluntary/autonomic nervous system to provide a quick response with a thought process to avoid overloading the brain so that it can carryout other actions at the same time - correct answer what does the PNS do? stimulus - receptor - sensory neurone - coordinator - motor neurone - effector - response - correct answer name the pathway of the detection of a stimulus chemoreceptors detect change in PH from the increase of CO2 in the blood that sends a nerve impulse to the medulla oblongata, nerve impulse sent to SAN via the sympathetic nervous system that initiates a wave of excitation across the atria, causing it to contract, there is a short delay by non conducting tissue while the ventricles fill and then the AVN releases another wave of excitation down the Purkinje tissue and bundles of his to the apex of the heart that then contracts from the base up, the more impulse to SAN = faster contraction of the heart to increase the heart rate, opposite = reduced impulse via parasympathetic - correct answer Describe the cardiac cycle with reference to increase heart rate Contraction within the muscle itself - correct answer What does myogenic mean? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS depolarises the neurone, and as more sodium draws in, more gates open until threshold has been reached and then begins action potential that repolarises the neurone by closing the sodium voltage gate channels and opening the potassium voltage gate channels until it has gone below resting potential where the refractory period occurs and no action potential can occur (sodium-potassium pump) then the process is repeated at each node of Ranvier until it reaches the synapse - correct answer Describe the process of a nervous impulse The jumping of an action potential from node ranvier to node ranvier - correct answer What is saltatory conduction? Diameter of a axon(larger = greater conductance), temperature (enzymes) and myelinated sheath (no myelin sheath = less saltatory conduction so less action potentials can occur along the same neurone = slower) - correct answer What affects the speed of a nervous impulse? Temporal summation occurs when a high frequency of action potentials in the presynaptic neuron invokes postsynaptic potentials that summate with each other - correct answer What is temporal summation? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS Spatial summation is a mechanism of invoking an action potential in a neuron with input from multiple presynaptic cells - correct answer What is spatial summation? Transmitter released that attaches to chloride ion protein channels on the post synaptic neurone, the channels open and chloride ions move into the post synaptic neurone by FDF, binding of neurotransmitter = K+ channels to open and release potassium in synapse so the potential decreases that causes hypolarisation so AP will not occur as sodium not present - correct answer How does synaptic inhibition occur? Combine multiple impulses at the same synapse so Brain is not overloaded with info + can stimulate multiple impulses in different neurones at the same time - correct answer What are the functions of a synapse? Calcium ions open because of AP that move into synaptic knob via FDF, this causes vesicles to fuse with the presynaptic neurone membrane that release acetylcholine into the synaptic cleft, acetylcholine then binds to protein receptors on the sodium ion channels on the post synaptic neurone that diffuse across a concentration gradient that causes a influx of sodium ions in the post synaptic neurone that causes an AP, acetylcholine then broken by acetylcholinerase into AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS choline and Ethanoic acid and diffuses back across the synaptic cleft but does not cause an action potential in the pre synaptic neurone as it is not in its acetylcholine form - correct answer Describe the transmission across a cholinegenic synapse? Calcium ions from sarcoplasmic reticulum causes by AP diffuse into muscle via concentration gradient that then causes tropomyosin to move that exposes the binding site of the actin filament, an ADP molecule then attaches to the myosin head that causes it to form a cross bridge with actin filament binding site, the actin filament is then pulled by the myosin head changing shape/angle that releases ADP, ATP then allows the myosin head to detach from the actin filament that is then broken by ATPase which provides the energy for myosin head to change back to its original shape and the process is repeated - correct answer Describe how the contraction of skeletal muscles work? Sliding filament theory - correct answer What is the theory behind skeletal muscle contraction called? The distance between two Z lines - correct answer What is the sarcomere? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS Breakdown of glycogen into glucose - correct answer What is glyconeolysis? Conversion of glucose to glycogen - correct answer What is glycogenesis? Diet - correct answer What factor affects blood glucose concentration? Islets of Langerhans - correct answer Where are B cells and A cells produced? Released by A cells, detects fall in blood glucose concentration, activates enzymes for gluconeogenesis and glyconeolysis - correct answer What does glucagon do? Binds to protein receptors on the pancreas liver membrane that causes it to change shape vesicles fuse with the membrane containing transport channels, this activates cyclic amp as a second messenger to activate enzymes that undergo glycogenolysis or gluconeogenesis - correct answer How does adrenaline affect blood glucose concentration? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS when water potential of the blood is too low detection by receptors hypothalamus which then sends a signal to the pituitary gland to secrete more ADH increasing the permeability through the recruitment of aquaporins opening channels in the DCT and collecting duct more water is absorbed by osmosis down a water potential gradient - correct answer Explain the role of ADH if the production of concentrated urine Mechanism that returns a change in the internal environment back to its optimum state - correct answer What is negative feedback? Enhancing of an effect created by its own influence - correct answer What is positive feedback? Rental artery, Afferent arteriole, Glomerulus, efferent arteriole, Bowman capsule, proximal conveluted tubule, descending limb of loop of henle, ascending limb of loop of henle, distal conveluted tubule, collecting duct - correct answer What is pathway of the nephron? Inorganic ions, glucose, amino acids, vitamins nitrogenous waste and some hormones - correct answer What is in the filtrate? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS Vasodilation, vasoconstriction and easing blood pressure - correct answer What effects the rate of glomerular filtration? Hydrostatic pressure squeeze out small molecules filtrate from basement membrane in glomerulus into the Bowmans capsule via ultrafiltration barriers consisting of podocytes that allow the filtrate to pass beneath them but stop any larger molecules like blood cells and proteins from entering the capsule - correct answer How is glomerular filtrate formed? Sodium actively transported out into blood capillaries that diffuses down concentration gradient in lumen to epithelial cells via facilitated diffusion through carrier proteins that also co-transport all valuable ions so that they can be reabsorbed by PCT (85% of reabsorption occurs in PCT) - correct answer Describe the process of the reabsorption of glucose and water in the proximal convoluted tubule Sodium diffuses out of ascending limb into interstitial space between ascending and descending, sodium moves into descending limb and water moves out of it into blood capillaries, thus as filtrate moves through loop of henle it lowers its water potential until it reaches the bottom of AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS Predators eat prey, prey numbers decrease, less resources = predators decrease so prey can then repopulate, more food = more predators and so on - correct answer Cycle of predation Systematic sampling - correct answer What would you use a belt transact for? Gradual change along a shore/line - correct answer What Does systematic sampling measure? Estimated population size = total in first sample X total in second sample divided by number of marked recaptured - correct answer What is the calculation for mark release recapture? Pioneer species reproduce a-sexually in inhabitable environment as they germinate rapidly and are photosynthetic, this then forms moss from dead lichens leaving nutrients in the soil, rocks erode causing more nutrients to build up in soil, produce grass/shrubs and trees from nutrients as environment becomes more hospitable and also environment is changed so more adapted to others species than current one, reaches the climax community - AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS correct answer Describe the process of succession starting from pioneer species Where life is suddenly altered and climax is reached a lot quicker as less stages needed than primary succession because nutrients and organisms already available - correct answer What is secondary succession? Economic, personal, ethical, cultural, aesthetic and management of succession - correct answer What are the main reasons for conserving a habitat? Random, DNA rep, radiation and chemicals and mutagenic agents - correct answer What are the causes of mutation? Groups of bases detach and reattach at different places - correct answer What is inverse mutation? Bases separate from one strand and are inserted into a different one - correct answer What is translocation mutation? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS No one cell can provide best conditions from for everything so having a range of them can cover all different conditions = multicellular - correct answer What is the importance of cell differentiation? Cells that turn into any cells that only creates proteins for specific functions - correct answer What is totipotency? Undifferentiated dividing cells that occur in adult animal tissues + need to be constantly replaced - correct answer What are stem cells? Differentiate into single type of cell - correct answer What does unipotent? Specialised cells - correct answer What are pluripotent cells? A protein that controls the rate of transcription - correct answer What is a transcription factor? Diffuses through phospholipid bilayer, binds to the receptor of transcriptional factor, changes the shape of AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS Stimulate specific cells to divide when growth factors attach to CSM and receptor protein permanently activated - correct answer What do oncogenes do? Codes for proteins that cause apopstasis - correct answer What does P53 do? DNA cut into smaller sections and put through a computer to align overlapping segments to assemble the entire genome - correct answer What is the whole genome shotgun? Science of collecting and analysing complex biological data - correct answer What is bioinformatics? Proteins produced by the genome in a given cell - correct answer What is a proteome? DNA containing genes from 2 types of organisms - correct answer What is recombinant DNA? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS Desired gene cut from DNA using restriction endonuclease, plasmids are then cut with same enzyme to form sticky ends that are complimentary to the sticky ends of the desired gene and join by addition of ligase, they are then returned to the Cell in which they want to be placed within a concentration gradient - correct answer Describe the process of transferring one gene to another Add marker to plasmid, add it to cell to grow and then use replica plating to put the cell onto a medium where the particular marker can be identified and the ones that have the marker also have the desired gene - correct answer How are markers introduced into modified plasmids? Cut by restriction endonuclease at specific restriction point - correct answer How is a gene removed from DNA? 95 = separate polynucleotide strands, 50 = mixture cooled so primers may anneal to strand, 72 = heated so DNA polymerase can join complimentary bases - correct answer What temperatures are used in heat treatment and what do they do? AQA A LEVEL BIOLOGY PAPER 2 QUESTIONS AND ANSWERS DNA heated that breaks H+ bonds, add primers, add nucleotides, cool to allow annealing of primers and the heated against that DNA polymerase can join complimentary nucleotides to separate strands of DNA that can be rapped Multiple times as a cycle - correct answer Describe the polymerase chain reaction Fragments move towards anode as it is charged but they move at different speeds depending on their size and so they separate - correct answer How does electrophoresis separate DNA fragments? DNA cut using restriction endonuclease, electrophoresis separates fragments according to size, DNA made single stranded, transferred to membrane to apply probe with VNTR's under specific heat to create a pattern that is unique to every individual - correct answer How is DNA fingerprinting carries out? Short lengths of single stranded DNA - correct answer What are DNA primers? Thermophilic aquaticus and because it denatures at 95 degrees C so it does not denature - correct answer What and why do they use the specific DNA polymerase in the thermocycler?