Biology 91156 — Photosynthesis, Respiration, and Enzymes

Vocabulary flashcards defining key biological concepts, enzymes, and cellular processes from the provided Biology 91156 review sheets.

Light-Dependent Stage

The first stage of photosynthesis occurring in the thylakoid membrane, where chlorophyll absorbs light to split water molecules (photolysis), producing oxygen as a waste product along with ATP and NADPH for the Calvin cycle.

Light-Independent Stage (Calvin Cycle)

The second stage of photosynthesis occurring in the stroma of the chloroplast, where $\text{CO}_2$ is fixed by RuBisCO onto RuBP and converted into G3P using ATP and NADPH, forming glucose and recycling G3P to remake RuBP.

Photolysis

The splitting of water molecules by light energy absorbed by chlorophyll in the thylakoid membrane during the light-dependent stage, producing oxygen as a waste product alongside ATP and NADPH.

RuBisCO

The enzyme in the light-independent stage that catches $\text{CO}_2$ floating into the leaf and sticks it onto RuBP.

G3P

The molecule converted from RuBP using ATP and NADPH delivered from the light-dependent stage, resulting in glucose production with some recycled to remake RuBP.

Osmosis (in Plants)

The passive process by which water enters root hair cells across a partially permeable membrane down a water potential gradient from higher water potential in the soil to lower water potential in the cell, requiring no energy.

Active Transport of Nitrate Ions

The process by which nitrate ions ($\text{NO}_3^-$) are absorbed by plant roots against their concentration gradient from lower concentration in soil using ATP energy and carrier proteins.

Aerobic Respiration

A metabolic process occurring in the mitochondria requiring a constant supply of oxygen, represented by Glucose + oxygen -> carbon dioxide + water + ATP, producing $36\text{--}38\text{ ATP}$ per glucose molecule.

Anaerobic Respiration

A rapid metabolic process occurring in the cytoplasm without oxygen, represented by Glucose -> lactic acid + ATP, producing $2\text{ ATP}$ per glucose molecule.

Oxygen Debt

The additional oxygen taken in by heavy breathing post-exercise to convert accumulated lactic acid back into glucose in the liver, causing lactic acid levels to gradually fall.

Enzyme

A biological catalyst made of protein that speeds up chemical reactions in the body without being used up itself, using an active site with a specific shape that fits its substrate.

Active Site

The specific region of an enzyme where the substrate binds, which must be complementary in shape to the substrate for the enzyme to function.

Cofactor

A molecule (such as Vitamin C) required by certain enzymes to bind and complete or maintain the correct 3D shape of the active site so substrates can bind properly.

Apoenzyme and Holoenzyme

An inactive enzyme lacking its required cofactor is an apoenzyme; once the cofactor binds to complete the active site, the active enzyme is called a holoenzyme.

Denaturation

An irreversible structural change in an enzyme caused by temperatures above optimum or extreme pH breaking hydrogen bonds, permanently changing the active site shape so the substrate can no longer fit.

Pepsin

An enzyme that works best at an optimum pH of $2$, above or below which hydrogen bonds break and cause denaturation.

Saturation Point

The point during an enzyme-catalyzed reaction where increasing substrate concentration no longer increases reaction rate because all active sites are fully occupied, causing the rate to plateau.