AQA A LEVEL BIOLOGY PAPER 2, Exams of Biology

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AQA A LEVEL BIOLOGY PAPER 2 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 - Name three advantages of mesophyll in the leaf stroma in the fluid filled matrix - where does the LIR occur? 100 stacked discs of thylakoids - 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 - 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 - describe the electron transport chain 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 - 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 - describe the process of the LIR phosphorylated glucose is broken down in two 3 carbon molecules called pyruvate (happens in the matrix mitochondria - what is glycolysis and where does it happen? pyruvate is decarboxylated and dehydrogenated to acetate NAD is reduced - what happens in the link reaction after Glycolysis? acetyl coenzyme A combines with oxaloacetate to form citrate which is decarboxylated and dehydrogenated to form 5 carbon molecule which is then dehydrogenated and decarboxylated to form 4 carbon ATP made by substrate-level phosphorylation and FAD is reduced, oxalacetate is then regenerated to restart the cycle - what happens in the Krebs Cycle after the link reaction? H+ from oxidized reduced NAD and FAD, splits into p and e travels down electron transport chain via oxidation-reduction reactions losing energy each carrier used pump p from matrix into intermembrane space creating high concentration forming electrochemical gradient move down into matrix by ATP synthase drives synthesis ATP chemiosmosis, Matriz end transport chain p,e, and o combine form water. o final electron acceptor. - what is oxidative phosphorylation? hydrolysed to glycerol that is phosphorylated into into triose phosphate that becomes glucose and thus glycolysis can occur - how does the respiration of lipids occur? where no oxygen is available to accept the H+ ion and so reduced NAD builds up and cannot take anymore H+ from Glyolysis thus pyruvate is now reduced and produces lactate and oxdidised NAD and produces ethanol in plants - what is anaerobic respiration? the dry weight of the total mass of living material in a specific area at a given time - what is biomass? SAN = faster contraction of the heart to increase the heart rate, opposite = reduced impulse via parasympathetic - Describe the cardiac cycle with reference to increase heart rate Contraction within the muscle itself - What does myogenic mean? Pressure in PC is transfixed to chemical energy from mechanical pressure that causes the stretch mediated sodium channels to become distorted and change shape to allow sodium to diffuse down a concentration gradient that causes the opening of more sodium ion channels to open on a neurone that stimulates the depolarisation of an axon as a threshold has been met of the micro voltage - Describe the generating of a action potential via the pacinian corpuscle Receptors in eye that found at the periphery, Detect low intensity light, have low visual acuity, can't detect colour and have more than one linking to the same neurone - What are rods? Found in fovea, detects colour, only one connected to the same neurone so multiple colours can be detected, detects high intensity light to produce rhodopsin - What is a cone? Cell body, dendrons, axon, Schwann cell, myelin sheath and nodes of Ranvier - Name the six parts of a motor neurone? Transport of hormones via blood plasma to target cells that is more slower and general - What is the hormonal system? Transport of nervous impulses that is faster and in a more localised region - What is the nervous system? Has a cell body in the middle of the axon that is a dorsal root ganglian - What is the distinguishable feature of a sensory neurone? Long axon, cell body at the end, short den-trites - Distinguishable features of a motor neurone? No threshold has been reached by stimulus so sodium potassium pump occurring where 3 molecules of sodium go in and 1 potassium goes out via active transport - Describe what is happening in resting potential? Neurone begins to depolarise as a stimulus has reached the threshold so sodium voltage-gated channels open and an influx of sodium ions enters the neurone that further 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 - Describe the process of a nervous impulse The jumping of an action potential from node ranvier to node ranvier - 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) - 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 - What is temporal summation? Spatial summation is a mechanism of invoking an action potential in a neuron with input from multiple presynaptic cells - 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 - 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 - 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 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 - 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 - Describe how the contraction of skeletal muscles work? Sliding filament theory - What is the theory behind skeletal muscle contraction called? The distance between two Z lines - What is the sarcomere? Mechanism that returns a change in the internal environment back to its optimum state - What is negative feedback? Enhancing of an effect created by its own influence - 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 - What is pathway of the nephron? Inorganic ions, glucose, amino acids, vitamins nitrogenous waste and some hormones - What is in the filtrate? Vasodilation, vasoconstriction and easing blood pressure - 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 - 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) - 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 the ascending limb that where sodium diffuses out and so water potential increases, then there's a higher water potential gradient in the interstitial space between ascending and collecting duct so water moves out of collecting duct into blood vessels - How is the gradient of sodium maintained in the loop of henle? Always ensures there is a water potential gradient that rates out water from the tubule so water will move out of the filtrate - What does the countercurrent multiplier do? Glucose phosphorylated using a phosphate from ATP, the ATP is then used to add another phosphate forming heroes biphosphate that is then split into 2 triose phosphates that is oxidised forming Pyruvate molecules - What is phosphorylation? That anything above critical value is due to chance and so is significantly different and measures the difference between two means - Most important thing to remember about Chi-squared or T-test When one allele masks another - What is epistasis? Two characteristics determined by two different genes located on different chromosomes are inherited - What is dihybrid inheritance? Two genes on the same autosome - What is autosomal linkage? When there is a small population that is likely to express only one set of alleles and genes and so are also effect more easily by mutations - What is genetic drift? Study of interrelationship between organisms and their environment - What is ecology? Temperature and light - Name two abiotic factors Intra = same species and inter = different species - What is the difffenrce between intraspecific and interspecific competition? Predators eat prey, prey numbers decrease, less resources = predators decrease so prey can then repopulate, more food = more predators and so on - Cycle of predation Systematic sampling - What would you use a belt transact for? Gradual change along a shore/line - What Does systematic sampling measure? Estimated population size = total in first sample X total in second sample divided by number of marked recaptured - 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 - 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 - What is secondary succession? Occurs in specific region of tumor suppressor gene, suppressor gene becomes inactive so their is increased cell division of the silenced gene and no transcription of the gene - What does hyper methylation do? Benign is slow growth, non cancerous, localised effects on body + malignant = cancerous, fast growing, large, life threatening - What is the difference between maligant and benign Tumors? Stimulate specific cells to divide when growth factors attach to CSM and receptor protein permanently activated - What do oncogenes do? Codes for proteins that cause apopstasis - What does P53 do? DNA cut into smaller sections and put through a computer to align overlapping segments to assemble the entire genome - What is the whole genome shotgun? Science of collecting and analysing complex biological data - What is bioinformatics? Proteins produced by the genome in a given cell - What is a proteome? DNA containing genes from 2 types of organisms - What is recombinant DNA? 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 - 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 - How are markers introduced into modified plasmids? Cut by restriction endonuclease at specific restriction point - 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 - What temperatures are used in heat treatment and what do they do? 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 - 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 - 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 - How is DNA fingerprinting carries out? Short lengths of single stranded DNA - What are DNA primers? Thermophilic aquaticus and because it denatures at 95 degrees C so it does not denature - What and why do they use the specific DNA polymerase in the thermocycler?