AP Biology - Unit 3: Cellular Energetics

Flashcards on cellular energetics, enzymes, free energy, cellular respiration, and photosynthesis.

Gibbs Free Energy

The energy available to do work in a reaction.

Endergonic Reaction

A reaction that requires energy input; it is non-spontaneous and results in products with more energy than reactants.

Delta G in Endergonic reactions

Positive change in free energy.

Exergonic Reaction

A reaction that releases energy; it occurs spontaneously and results in products with less energy than reactants.

Delta G in Exergonic reactions

Negative change in free energy.

Enzymes

Biological catalysts that speed up chemical reactions by reducing activation energy.

Catalyst

Speeds up a chemical reaction.

Activation Energy

The amount of energy required to start a reaction.

Competitive Inhibitor

Inhibitor that binds to the active site of an enzyme, competing with the substrate.

Non-Competitive Inhibitor

Inhibitor that binds to an allosteric site on an enzyme, changing its shape and preventing substrate binding.

Denaturation

Process in which a protein loses its native shape due to factors like high temperature, pH changes, or salinity.

Glycolysis

First step of cellular respiration, taking place in the cytosol, where glucose is broken down into pyruvate, producing NADH and ATP.

Krebs Cycle

Second step of cellular respiration, occurring in the mitochondrial matrix, where acetyl CoA is further oxidized, producing carbon dioxide, NADH, FADH2, and ATP.

Oxidative Phosphorylation

Final step of cellular respiration, taking place in the mitochondrial cristae, involving the electron transport chain and chemiosmosis to produce a large amount of ATP.

Electron Transport Chain

A series of protein complexes that transfer electrons from electron donors to electron acceptors via redox reactions, and couples this electron transfer with the transfer of protons (H+) across a membrane.

Chemiosmosis

The movement of ions across a selectively permeable membrane, down their electrochemical gradient. More specifically, it relates to the movement of protons down their concentration gradient.

Light Reactions

First stage of photosynthesis, occurring in the thylakoid membrane, where light energy is used to split water, producing oxygen, ATP, and NADPH.

Calvin Cycle

Second stage of photosynthesis, taking place in the stroma, where carbon dioxide is fixed and reduced using ATP and NADPH to produce G3P (glyceraldehyde-3-phosphate).

Thylakoid

Internal membrane-bound compartments within chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis.

Stroma

The fluid-filled space surrounding the grana inside a chloroplast, where the Calvin cycle occurs.

C4 Plants

Plants that have adapted to hot conditions by using a four-carbon compound to initially fix carbon dioxide, minimizing photorespiration.

CAM Plants

Plants adapted to arid conditions that open their stomata at night to fix carbon dioxide into organic acids, which are then used during the day for photosynthesis.

Cyclic Electron Flow

In photosynthesis, when electrons cycle back from photosystem I, leading to ATP production without NADPH.

Non-Cyclic Electron Flow

In photosynthesis, electrons pass from photosystem II to photosystem I to NADP+, producing NADPH and ATP with input of water and release of oxygen.