topic 8 chapter review

(8.1) define metabolism and explain how metabolic pathways are controlled

(8.1) define metabolism and explain how metabolic pathways are controlled

metabolism - all biochemical reactions occuring within a living organism. enzymes catalyse each step of a metabolic pathway by regulating their amount. they lower the activation energy by binding with substrates at the active site, which slightly changes their shape (induced fit model). competitive inhibitors are chemicals which bind at the active site, while non-competitive bind to other areas to deactivate it. end product inhibition means the end product works as an inhibitor of an enzyme early on in the pathway.

(8.2) summarise the stages of cell respiration and production of ATP

the energy in glucose (6C) is transferred to ATP. through glycolysis in the cytoplasm, glucose is broken down into two pyruvate (3C) molecules. one pyruvate gets oxyidised (link reaction) in the mitochondrial matrix. CO2 is removed to form Acetyl CoA (2C). it enters the Krebs cycle and joins with Oxaloacetic acid (4C) to form citric acid (6C). each step of the cycle removes carbon as CO2 and generates ATP, NADH, and FADH2. other molecules than glucose may provide respiratory substrates. hydrogen and electron carriers use energy from electrons (that have been donated from the Krebs cycle) to pass hydrogen through the cristae membrane. through chemiosmosis, hydrogen travels through ATP synthase to generate ATP and H binds with O to form H2O.

(8.3) what are the two parts of photosynthesis and where do they take place?

light dependent reactions occur in the grana. light energy elevates electrons in photosystem II to higher energy and water splits into O and H. as electrons are passed, they activate hydrogen pumps. photosystem I absorbs light to elevate electrons again and NADP+ reductase reduces NADP+ to NADPH. H+ flow back into the membrane through ATP synthase to generate ATP (chemiosmosis). this is non-cyclic phosphorylation. cyclin phosphorylation uses only photosystem I and NADPH is not produced. light independent reactions occur in the stroma. RuBisCo joins CO2 with RuBP. ATP and NADPH driven reactions form TP. some of it leaves the cholorplast to form sugars, while the rest continue the cycle until they form RuBP again.

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