Biology Unit 4: Respiration and Photosynthesis

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AQA A2 Biology Photosythesis, Respiration and ATP (chapter 2, 3 and 4)

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Angela Yianni
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Question Answer
Define energy: The ability to do work
Why are the units of energy? Joules, J
What does the body need energy for? Metabolism Movement Active transport Maintenance, repair, division Production of substances (enzymes etc.) Maintainance of body themperature
How does energy flow through living systems? Light energy converted by plants to chemical energy (glucose) by photosynthesis Chemical energy is converted into ATP during respiration ATP used to do work
Word equation for then hydrolysis of ATP Adenine triphosphate + water = Andenine disphosphate + inorganic phosphate (+ energy)
Decribe how ATP is converted into ADP and ADP is converted into ATP ATP is hydrolysed into ADP and inorganic phosphate, the ADP is then condensened (phosphorylated) into ATP
Name the three types of phosphorylation Photophosphorylation Oxidative phosphorylation Substrate level phosphorylation
How are leaves adapted for photosynthesis Large surface area Thin (short diffusion pathway) Transparent cuticle Long upper mesophyll with lots of chloroplasts Stomta (gas exchange) Xylem (transport water to leaf)
General equation for photosynthesis 6carbon dioxide + 6water = Glucose + 6oxygen
How are the chloroplasts structured? Grana = stacks of discs called thylakoids, connecting tubular extensions = lamellae. Stroma = fluid filled matrix, contain starch grains
What occurs wen chlorophyll absorb light? Elections are excited to higher energy level,vthese electrons leave the molecule and are taken up by an electron carrier
When the chlorophyll loses electrons is it oxidised or reduced? Oxidised
How does the excitation of chlorophyll lead to ATP production? Electrons pass along a number of electron carriers, in a series or redox reactions, each carrier is at a lower energy level so the electrons lose energy at each stage this energy is used to synthesis ATP
How is reduced NADP produced in the light dependent reaction? The photolysis of water produces the electrons needed to replace those lost in the chlorophyll, this also produces hydrogen ions which reduce NADP
Equation for the photolysis of water: 2Water (+light) = 4Hydrogen ions + 4Electrons + Oxygen
Why is the photolysis of water needed during the light dependant reaction? To produce the electrons needed to replace those lost by the chlorophyll, also produces hydrogen ions to reduce NADP and oxygen
Where does the light dependant reaction take place? Grana/Thylakoids of the chloroplasts
How are the thylakoids adapted for their function (light dependant reaction)? Large surface area - for the attachment of chlorophyll, electron carriers and enzymes. Network of proteins, to hold chlorophyll in a way to maximise light absorption. Granal membranes contain enzymes for ATP synthesis. DNA and ribosomes - so chloroplasts can manufacture proteins needed
How does carbon dioxide enter the chloroplast? Through the stomata of the leaf then into the stroma the chloroplast
How is carbon dioxide used to produce organic molecules (glucose) and regereratec RuBP in the calvin cycle carbon dioxide combines with a 5 carbon compound called RuBP producing 2 3 carbon molecules ATP and reduced NADP are used to produce GP and TP, NADP isreformed and returns to the light dependent reaction whilst some TP is converted to organic substances most is regenerated RuBP using atp
where does the light independent reaction take place? in the stroma of the chloroplast
why does the light independent reaction not take place in the absence of light the light independent reaction uses the products of the light dependent reaction
what is the law of limiting factors at any given moment the rate of a physiological process is limited by the factor that is at its least favourable value
what are two ways of measuring the rate of photosynthesis measuring the volume of oxygen released by the plant or the volume of carbon dioxide taken up by the plant
if light intensity is the limiting factor how is it related to the rate of photosynthesis rate of photosynthesis is directly proportional to intensity of light
what is the compensation point the point where the volume of oxygen produced and volume of carbon dioxide used by the plant is exactly balanced no net production or loss of gas
how does carbon dioxide concentration affect the rate of photosynthesis carbon dioxide concentration affects the enzyme activity thus increasing rate of photosynthesis
how does temperature affect the rate of photosynthesis plants have an optimum temperature above this rate will decrease as the enzymes will become denatured
how and why is glucose phosphorylated glucose is phosphorylated to make it more reactive the phosphate comes from the hydrolysis of ATP
how does phosphorylated glucose two molecules of pyruvate phosphorylated glucose is split into two 3 carbon molecules of triose phosphate. The 2 triose phosphate molecules are oxidised hydrogen ions are removed and transferred to a hydrogen ion carrier, NAD.enzymes convert triose phosphate pyruvate producing 2 atp molecules
how are two molecules of reduced NAD produced two molecules of triose phosphate are oxidised producing to hydrogen ions which can reduce two molecules NAD
why is the overall ATP yield only 2 two molecules of atp are required to phosphorylate glucose, and only for molecules of atp are produced when two molecules of triose phosphate are converted into two molecules of pyruvate
where does glycolysis take place in the cytoplasm of the cell
why is glycolysis the only source of atp in the absence of oxygen (anaerobic conditions) glycolysis does not require oxygen to occur whilst all the other stages of respiration do require oxygen
give the equation for the link reaction Pyruvate + NAD + coenzyme A = acetyl coenzyme A + reduced NAD + carbon dioxide
explain how the link reaction produces 2 molecules of carbon dioxide first pyruvate is oxidised, hydrogen ion is accepted by NAD, the resulting acetyl group combines with coenzyme a to produce acetyl coenzyme a and one carbon dioxidedioxide molecule
how does the krebs cycle produce to reduced hydron carriers and atp acetyl coenzyme a combines with a full carbon molecule to produce a 6 carbon molecule this 6 carbon molecule losses carbon dioxide and hydrogen to give the 4 carbon molecule these hydrogen ions are used to produce reduced hydrogen carriers, ATP is formed by substrate level phosphorylation
what is the overall yield for the link reaction and krebs cycle for one molecule of glucose two reduced NAD molecules, two reduced FAD molecules, two ATP molecules and 6 carbon dioxide molecules
explain the significance of the krebs cycle breaks down macromolecules into smaller ones produces hydrogen ions letter carried to the electron transport chain by oxidative phosphorylation leading to ATP production regenerate the 4 carbon molecule that combines with acetyl coenzyme a and isa source of intermediate compounds used by cells in the manufacture of other substances
why are hydrogen acceptors oxidised where do the protons and electrons hydrogen atoms are released from the hydrogen carriers the atom split in two protons and electrons the electrons move along the electron transport chain
how is the energy lost at each electron acceptor used To pump electrons from the matrix intuothe inter membrane space
how is an electrochemical gradient established the concentration of protons in the intermembrane space is higher in the matrix
how does protons moving back into the matrix produce atp protons move down at the electrochemical gradient back into the matrix via atp synthase this drive theory synthesis of atp from adp and inorganic phosphate
what is the name of the process which generates atp chemo osmosis
how is water produced in the electron transport chain in a matrix at the end of the electron transport chain the protons and electrons and oxygen combine to form water
why is oxygen described as the final proton accepter in the electron transport chain oxygen combines with the protons to form water
what process can occur in anaerobic conditions glycolysis
what is the equation for anaerobic respiration in plants and some microbe? Pyruvate + reduced NAD = ethanol + carbon dioxide + NAD
how is ethanol produced from pyruvate in plants and some microbes Pyruvate loses carbon dioxide and accepts hydrogen from reduced NAD to produce ethanol
What is the equation for anaerobic respiration in animals? Pyruvate + reduced NAD = lactate + NAD
How is lactate produced from pyruvate in animals? Pyruvate takes up two hydrogen atoms from the reduced NAD forming lactate
Why is lactate build up bad in humans? Lactate is harmful,causes muscle cramps and fatigue
What is the energy yield from aerobic respiration? Two molecules of ATP from every one molecule of glucose