8 — metabolsim, cell respiration & photosynthesis Flashcards
describe how ATP is produced by photosystem II in the light dependent stage of photosynthesis (5)
- light energy absorbed by chlorophyll
- excited electrons passed to electron transport chain
- protons pumped into thylakoid space
- protein gradient generated
- protons pass via ATP synthase to the stroma
- ATP synthase phosphorylates ADP
- chemiosmosis
- ATP synthase are in the thylakoid membrane
compare and contrast photosynthesis and respiration
similarities
- both have membrane bound organelles adapted to their function
- both use excited electron transferred between carriers on membranes (ETC)
- both generate proton gradients on the membranes by transfer of electrons (chemiosmosis)
- both generate ATP
differences
- solar energy converted to chemical energy vs chemical energy converted to usable energy
- occurs in chloroplast vs occurs in mitochondrion
- reduce NADP vs NAD/ FAD
- fix CO2 vs produce CO2
- O2 is produced vs O2 is used
explain the role of the electron transport chain in the generation of ATP by cellular respiration (7)
- electron transport chain performs chemiosmosis
- receives energy/ electrons from oxidation reactions
- receives electrons from reduced NAD/ FAD or NADH/ FADH
- energy released as electrons pass from carrier to carrier in the chain
- release of energy from electron flow coupled to proton pumping
- protons pumped into intermembrane space
- creates proton gradient
- protons diffuse back
- protons pass through ATP synthase
- protons return to the matrix
- flow of protons provides energy for generating ATP
- electrons transferred to oxygen at end of electron transport chain
explain the role of hydrogen ions usd in photosynthesis (7)
- hydrogen ions and oxygen are obtained from photolysis of water
- excited electrons from photosystem II contribute to generate a hydrogen ion gradient
- ATP synthase generates ATP by chemiosmosis
- high energy electrons from photosystem II are passed through an electron transport chain
- NADP accepts H+ from the stroma to produce NADPH+
- ATP are used by light independent reactions (calvin cycle) in the stroma
- in calvin cycle, carbon fixation to RuBP produced G3P
- ATP is used to transport G3P to TP
- NADPH+ is used to transform G3P to TP
describe how the structure of chloroplast is adapted to its function in photosynthesis (4)
- thylakoids have a small internal volume to maximise hydrogen gradient
- many grana (thylakoid stacks) give large surface area
- granas contain photosynthetic pigments, electron carriers, ATP synthase enzymes
- photosynthetic pigments arranged into photosystems allowing maximum absorption of light energy
- stroma has suitable pH for enzymes of calvin cycle
outline how carbon compounds are produced in cells using light energy (5)
- occurs by the process of photosynthesis
- occurs in chloroplasts of plant cells
- chlorophyll absorbs red/ blue lights and reflects green light
- raw materials are carbon dioxide and water
- water is split by photolysis
- oxygen is produced as waste
- glucose formed
- glucose molecules combine to form starch for storage
- light energy transformed to chemical energy
describe the role of oxygen in aerobic cell respiration (5)
- final electron acceptor
- at the end of the electron transport chain
- also accepts protons
- water produced
- helps to maintain proton gradient across inner mitochondrial membrane by removal of protons from the stroma
- oxygen is highly electronegative
- avoids anaerobic respiration
- allows more electrons to the delivered to the ETC
- oxygen allows maximum yield of energy from glucose
explain the stages of aerobic respiration that occur in the mitochondria of eukaryotes (8)
- cell respiration is the controlled release of energy from organic compounds to produce ATP
- cell respiration involves the oxidation and reduction of electron carriers
- in link reaction pyruvate is converted into CoA, CO2 is released and NAD is reduced
- in the Krebs cycle, a 4C molecule combines with acetyl CoA
- decarboxylation releases 2 CO2 molecules for each pyruvate
- 3 NADH and 1 FADH produced
- ATP generated in the krebs cycle
- reduced molecules are carried to the cristae
- transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is coupled to proton pumping
- protons accumulate in the intermembrane space
- protons diffuse through ATP synthase to generate ATP
- chemiosmosis is the use of a proton gradient to generate ATP
- oxygen is the final electron acceptor
explain how chemical energy for use in the cell is generated by electron transport and chemiosmosis (8)
- NAD/ FAD carries H and electrons
- reduced NAD produced in glycolysis, link reaction and krebs cycle
- reduced FAD produced in krebs cycle
- reduced NAD/ FAD delivers electrons to ETC
- ETC is in mitochondrial inner membrane
- electrons release energy as they flow along the chain
- electrons from ETC accepted by oxygen
- proteins in the inner mitochondrial membrane acts as proton pumps
- protons pumped into intermembrane space
- energy from electrons used to pump protons into intermembrane space
- ATP synthase in inner mitochondrial membrane
- energy released as protons pass down the gradient
- ATP synthase phosphorylates ADP
- oxidative phosphorylation
distinguish between anabolism, catabolism and metabolism (3)
- metabolism is all enzyme catalysed reactions in a cell
- anabolism is synthesis of polymers
- catabolism is breaking down molecules
outline action of all enzymes (4)
- catalyse reactions
- substrate specific
- lower the activation energy
- substrate collides with active site
- enzyme substrate complex formed
explain how the light independent reactions of photosynthesis rely on the light dependent reactions (7)
- light dependent reactions produce ATP
- ATP generated by chemiosmosis
- reduced NADP produced by electrons from photosystem I
- RuBP + CO2 -> glycerate 3 phosphate in light independent reactions
- glycerate 3 phosphate reduced to triode phosphate
- ATP used in light independent reactions
- ATP provides energy for reduction of glycerate 3 phosphate
- ATP needed to regenerate RuBP
- ATP run out in darkness
- calvin cycle is indirectly dependent on light
