U2T1 - Respiration Flashcards
Respiration
What is the equation for aerobic respiration?
Glucose + oxygen -> carbon dioxide + water + energy
C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP
How does respiration occur?
Series of enzyme controlled steps so energy release controlled.
How is ATP synthesised?
From ADP + inorganic phosphate (Pi) during phosphorylation, making ATP energy rich with extra phosphate group. By substrate level or oxidative phosphorylation. Uses condensation (removes 1 molecule water). To convert back, use hydrolysis (use water, catalysed by ATPase)
Describe the conversion of ATP to ADP and ADP to AMP.
They yield same amount of energy as breakage of bond between single remaining phosphate + sugar yields very little energy. Done by ATPase. Reversible but requires energy.
How much ATP do cells store?
Very little. Max 5g in body at any time. Rapidly built from ADP + Pi so continual cycling in cells.
Why is ATP a suitable energy store?
Hydrolysis of ATP molecules releases small amount of energy compared to glucose so can be released in small, manageable steps. ATP hydrolysis is single reaction (1 bond broken) which releases energy immediately + provides cell fine control over energy. ATP small + soluble so can be transported around cell easily.
What are some uses of ATP?
Energy for metabolic processes, movement, active transport + activates molecules via phosphorylation (glycolysis).
Describe the structure of the mitochondria.
Surrounded by double membrane separated by inter-membrane space, outer membrane permeable to most small molecules, inner membrane highly folded forming cristae which increase SA for more ATP. Enzymes for ETC on cristae. Matrix contains chem compounds + some resp reactions occur there.
What are the stages of aerobic respiration?
Gycolysis, link reaction (pyruvate oxidation), kreb’s cycle + ETC (Electron transport chain)
Describe the process of glycolysis.
Activate glucose by phosphorylation, make more reactive + uses ATP as 2 phosphates come from hydrolysis of 2 ATP molecules, cerates fructose 1,6 biphosphate.
Splits into 2 3-carbon molecules of triose phosphate, oxidised by H2 loss using dehydrogenation by dehydrogenase to form pyruvate with production of 2 ATP molecules. H2 atoms collected by NAD which reduces them to NADH. At end, glucose - 2 pyruvate results in 4 ATP created + 2 NADH + H+. Uses 2 ATP so net gain ATP is 2.
What is the process of the link reaction?
Pyruvate decarboxylated by removal of 1 molecule of CO2. Dehydrogenation occurs with H2 removal, forming NADH. 2 carbon acetyl group combines with CoA, forming acetyl CoA. 2 carbon acetyl group enters Kreb’s cycle whilst CoA recycled to be combined with another acetyl group.
What are other names for the Krebs cycle?
Tricarboxylic acid cycle (TCA) + citric acid cycle.
Where does the Krebs cycle take place?
Mitochondrial matrix. Involves cyclical series of reactions.
Describe the process of the Krebs cycle.
2C Acetyl CoA combines with 4C oxaloacetate forming 6C citric acid/citrate which undergoes decarboxylation, forming 5C oxoglutarate, losing 1 molecule CO2. Dehydrogenation also occurs, H2 reduces NAD to NADH. Oxoglutarate decarboxylated, forming 4C oxaloacetate, losing CO2 + cycle continues. Converting 5C Oxo to 4C Oxa involve dehydrogenation so at 2 points occurs so 2 molecules NADH produced. At 1 point, hydrogen released + used by FAD, reducing it to FADH2.
What is produced by the Krebs cycle?
As 2 molecules Acetyl CoA for each glucose molecule, cycle turns twice for each molecule so for each molecule, cycle produced 2 molecules of ATP directly, 6 pairs H2 atoms for 6 molecules NADH + 2 pairs H2 atoms forming 2 molecules FADH2.
Where does the ETC occur?
Cristae of mitochondria.
Why is the ETC diagram drawn as sloping?
As throughout chain, electrons lose potential energy as it’s converted into chemical energy in form of ATP. NAD, FAD, coenzymes + carriers arranged into sequence of decreasing potential energy, each carrier downstream has stronger reducing power than one before so H2 + electrons can move along chains with carriers reduced + oxidised as H2/e+ pass along chain in redox reactions.
Describe the process of the ETC.
NAD + FAD feed in pairs of H2 from link, krebs + glyco. H atoms split into protons + electrons between CoA Q + Cyto B. NAD passes in H atoms earlier than FAD which feeds in between flavoprotein + cyto Q. H2 dissociates into electrons (2e-) + protons (2H+) so ETC functions as electron carrier. O2 acts as final acceptor of H atoms + combines with H2 (e- + h+ rejoin) to form water, catalysed by cytochrome oxidase. As H atoms released from carriers (FAD + NAD), carriers regenerated to return to glycolysis + so on.
What is interesting about the cytochromes involved in the ETC?
Contain iron, electrons go to cytochromes, hence why you can become breathless when anaemic.
At what stage is O2 needed for respiration? What is the only stage which can occur without it?
ETC (acts as final acceptor)
Glycolysis
What increases the amount of ATP produced from the ETC?
Higher surface area due to more deeply folded cristae as more space for electrons + coenzymes etc.
What is the total number of ATP formed at each stage of respiration? Which is highest?
Glyco - 2 (substrate)
Link - 0
Krebs - 2 (substrate)
ETC - 34 (oxidative)
