OCR Biology A2 Unit 1 Notes-Respiration

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RESPIRATION: the process by which energy stored in complex organic molecules is used to make ATP.

ATP: phosphorylated nucleotide and is the universal energy currency.

Why do living organisms need to respire? To drive biological processes/metabolic reactions (building=anabolic, breaking=catabolic) e.g. active transport, secretion, endocytosis, synthesis of large molecules from smaller ones, replication of DNA, synthesis of organelles, movement, activation of chemicals.

ATP-high energy intermediate compound found in prokaryotic and eukaryotic cells, adenosine (adenine, ribose) 3-phosphate, continuously hydrolysed and resynthesised. ATP can be hydrolysed to ATP and Pi (inorganic phosphate) so energy is immediately available to cells in small manageable amount that won't damage the cell and won't be wasted.

4 stages: glycolysis, link reaction, Krebs cycle, oxidative phosphorylation.

OILRIG-oxidation is loss, reduction is gain.

Why are coenzymes needed? The dehydrogenase enzymes catalyse the removal of hydrogen atoms. Hydrogen atoms are combined with coenzymes such as NAD. Delivery of hydrogens to the cristae reoxidises the coenzymes so they can combine with more hydrogen atoms from the first three stages of respiration.

NAD-organic, non-protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions. Made of two linked nucleotides. When NAD has accepted 2 hydrogens, it is reduced. When it loses the electrons from the hydrogens it is oxidised. NAD operates in glycolysis, link reaction, Krebs, Coenzyme A (CoA)-made from pantothenic acid, adenosine, 3 phosphate groups and cyteine. Carries ethanoate (acetate) groups onto the Krebs cycle.

MITOCHONDRIA: organelles found in eukaryotic cells. Sites of link reaction, Krebs cycle and phosphorylation-the aerobic stages of respiration. Have inner and outer phospholipid membrane, inner membranes folded forming cristae, intermembrane  space between, matrix enclosed by inner membrane, gel like, rod shaped or thread like, 0.5-1um diameter, 2-5um long, mitochondria moved by microtubules.

How does their structure enable them to carry out their functions?

Matrix-where link reaction and Krebs cycle take place. It contains the enzymes that catalyse the stages of these reactions, NAD, oxaloacetate, DNA, ribosomes.

Outer membrane-contains channels/carriers to move molecules such as pyruvate.

Inner membrane-impermeable to most small ions, large SA, has e- carriers + ATP synthase enzymes, electron transport chains-enzymes (electron carriers) are associated with a cofactor-haem groups, oxidoreductase enzymes, pumps, large.

CHEMIOSMOSIS: flow of protons down a concentration gradient, through ATP synthase enzymes, into the matrix.

GLYCOLYSIS: metabolic pathway where each glucose molecule is broken down to two molecules of pyruvate. It occurs in the cytoplasm of all living cells, and occurs in both aerobic and anaerobic respiration.

Stage 1: phosphorylation-glucose phosphorylated by ATP…



Thanks, this really helped.

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