Metabolic Processes: Unit Review

First: energy is not created or destroyed, only converted (e.g. chemical to kinetic and heat). Second: every energy conversion increases the entropy of the universe; some energy is always lost as heat, so cells need a constant energy input.

Exergonic (ΔG < 0), so it is spontaneous (though it may still be slow without an enzyme).

It lowers the activation energy (speeding the reaction) but does not change ΔG or the equilibrium.

Its three negatively charged phosphates repel each other; ADP + Pᵢ is more stable, so breaking the terminal bond and forming new bonds with water releases free energy (about −30 kJ/mol under standard conditions).

Using an exergonic reaction (ATP hydrolysis) to drive an endergonic one, often by transferring a phosphate to a reactant (phosphorylation).

Substrate-level phosphorylation (an enzyme transfers a phosphate from a substrate to ADP) and oxidative phosphorylation (ATP synthase powered by an H⁺ gradient).

Reduced: it gains electrons (carried with hydrogen).

NADP⁺/NADPH in photosynthesis; NAD⁺/NADH and FAD/FADH₂ in respiration.

Glucose is oxidized (to CO₂); oxygen is reduced (to H₂O).

In the cytoplasm; it does not need O₂.

2 pyruvate, 2 ATP (net) and 2 NADH.

It uses 2 ATP at the start to phosphorylate glucose, before making 4 ATP later (net 2).

Each pyruvate loses a CO₂, is oxidized (making NADH) and joins coenzyme A to form acetyl-CoA, in the mitochondrial matrix.

2 turns: 4 CO₂, 6 NADH, 2 FADH₂, 2 ATP (or GTP).

Oxaloacetate (4C), forming citrate (6C).

It is the final electron acceptor of the ETC, combining with electrons and H⁺ to form water.

In the intermembrane space (pumped there by the ETC).

Electrons can't pass to O₂, so the chain backs up, H⁺ pumping stops, the gradient disappears and ATP synthase makes almost no ATP; NAD⁺ isn't regenerated either.

Each NADH yields about 2.5 ATP and FADH₂ about 1.5 (not 3 and 2), and some energy is used to transport NADH electrons, pyruvate and phosphate into the mitochondrion.

Glycerol enters glycolysis; fatty acids are broken into acetyl-CoA by β-oxidation and enter the Krebs cycle.

ATP inhibits PFK (feedback inhibition), slowing glycolysis when the cell has enough energy.

To regenerate NAD⁺ so glycolysis can keep making 2 ATP per glucose without O₂.

Lactate: lactate only (no CO₂), e.g. muscle and yogurt bacteria. Alcohol: ethanol + CO₂, e.g. yeast.

Anaerobic respiration uses an electron transport chain with a final acceptor other than O₂ (such as nitrate or sulfate), so it makes more ATP; fermentation uses no ETC.

Blue → green → yellow (CO₂ forms carbonic acid).

KOH absorbs CO₂, so volume change measures O₂ used. Glass beads control for temperature and pressure changes not due to respiration.

Respiration is enzyme-controlled; higher temperature (below the optimum) increases enzyme activity, so the rate is higher.

Sprint: creatine phosphate and glycolysis (anaerobic). Marathon: aerobic respiration of carbohydrate and fat.

More mitochondria, more capillaries, more aerobic enzymes and myoglobin, so more ATP comes from aerobic respiration.

To restore creatine phosphate and ATP, convert lactate back to glucose (in the liver), replenish O₂ stores and cope with raised temperature and heart rate.

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Chlorophyll absorbs red and blue light most and reflects/transmits green.

Light-dependent reactions in the thylakoid membranes; Calvin cycle in the stroma.

From water, split by photolysis at photosystem II.

ATP and NADPH.

Cyclic uses only PS I; electrons return to the ETC, making ATP only (no NADPH, no O₂).

Rubisco, attaching CO₂ to RuBP.

3 CO₂, 9 ATP, 6 NADPH.

C₄: fix CO₂ in mesophyll cells and release it around rubisco in bundle-sheath cells (separated in space). CAM: open stomata at night and store CO₂ as acids, using it in the day (separated in time).

Photosynthesis produces O₂, which fills the air spaces and makes the disks buoyant.

Lower light intensity → slower photosynthesis → disks take longer to float (larger ET50).

To make sure any starch found was made during the experiment, not before.

Any two: double membrane; their own DNA and ribosomes; an ETC and chemiosmosis with ATP synthase; inner folded membranes (thylakoids and cristae).

The light intensity at which photosynthesis rate = respiration rate, so there is no net gas exchange.

Yes, all the time, day and night, in all living cells.

Nutrients → algal bloom → algae die → decomposers respire, using O₂ → hypoxia → organisms die.

Biogas (mainly methane and CO₂) and digestate (fertilizer).

Mainly burning fossil fuels (and deforestation), which releases stored carbon faster than photosynthesis and the oceans remove it.