Energy, Enzymes, Photosynthesis, and Cellular Respiration

Vocabulary practice flashcards covering thermodynamics, enzyme kinetics and regulation, photosynthesis, cellular respiration, and fermentation based on the lecture study guide and worksheets.

Energy

The capacity to do work.

Kinetic Energy

Energy that involves movement, such as light, heat, and mechanical movement.

Potential Energy

Stored energy, such as the chemical energy held within the bonds of molecules.

First Law of Thermodynamics

The principle stating that within any isolated system, energy can neither be created nor destroyed, but can be converted from one form to another.

Second Law of Thermodynamics

The principle stating that any energy conversion causes the amount of useful energy to decrease and the amount of randomness and disorder in an isolated system to increase.

Entropy

The measure of the amount of randomness and disorder in a system.

Metabolism

The total sum of all chemical reactions occurring within a cell or organism.

Metabolic Pathway

A sequence of linked chemical reactions occurring within a cell.

Endergonic Reaction

A chemical reaction that requires an input of energy to proceed, resulting in products that possess more energy than the reactants.

Exergonic Reaction

A chemical reaction that liberates energy and increases entropy, resulting in products that possess less energy than the reactants.

Coupled Reaction

A linked pair of reactions in which an exergonic reaction provides the energy required to drive an endergonic reaction.

Adenosine Triphosphate (ATP)

The major short-term energy carrier molecule in cells, composed of adenine, a five-carbon ribose sugar, and three phosphate groups.

Catalyst

A substance that speeds up a chemical reaction without itself being permanently changed or consumed in the process.

Enzyme

A biological protein catalyst that increases the rate of a specific biological reaction by lowering the activation energy without being permanently altered.

Active Site

The specific region of an enzyme that binds substrates and changes shape during the reaction to facilitate catalysis.

Substrate

The reactant molecule that binds specifically to the active site of an enzyme to undergo a chemical reaction.

Activation Energy

The minimum energy input required to start a chemical reaction by destabilizing bonds in the reactant molecules.

Coenzyme

A non-protein organic molecule bound to an enzyme that is required for its proper catalytic activity, typically synthesized from water-soluble B vitamins.

Competitive Inhibition

A mode of enzyme regulation where an inhibitor directly competes with the substrate for binding at the active site.

Feedback Inhibition

A regulatory mechanism where the end product of a metabolic pathway binds to and inhibits an enzyme involved earlier in its own synthesis.

Oxidation

The loss of one or more electrons from a molecule or atom during a chemical reaction.

Reduction

The gain of one or more electrons by a molecule or atom during a chemical reaction.

Denaturation

The loss of an enzyme's three-dimensional shape and function, often caused by charged ions disrupting bonds or extremes of pH.

Photosynthetic Equation

$$\text{light} + 6\text{CO}_2 + 12\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{H}_2\text{O} + 6\text{O}_2$$

Mesophyll Cells

Specialized cells in leaves where chloroplasts are primarily concentrated and where photosynthesis takes place.

Thylakoid

A membrane-bound sac inside a chloroplast containing chlorophyll, accessory pigments, and electron transport proteins for the light-capturing reactions.

Grana (Granum)

Stacked columns of thylakoid membrane discs situated within the chloroplast.

Stroma

The fluid-filled space within a chloroplast surrounding the grana, where the synthesis reactions convert $\text{CO}_2$ into sugar.

Chlorophyll

The primary photosynthetic pigment in thylakoid membranes that absorbs blue and red wavelengths of light while reflecting green light.

Carotenoids

Accessory photosynthetic pigments (including xanthophyll and carotene) that reflect yellow and orange light while absorbing other wavelengths, such as green, to assist light capture.

Photon

A discrete particle of light energy that can be absorbed, reflected, or transmitted by a pigment molecule.

Photo Reactions

The initial reactions of photosynthesis in the thylakoid membranes requiring light, chlorophyll, $\text{ADP}$, $\text{NADP}^+$, and $\text{H}_2\text{O}$ to split water, release $\text{O}_2$, and produce $\text{ATP}$ and $\text{NADPH}$.

Synthesis Reactions

The light-independent reactions of photosynthesis occurring in the stroma that consume $\text{CO}_2$, $\text{ATP}$, and $\text{NADPH}$ to synthesize glucose, regenerating $\text{ADP}$ and $\text{NADP}^+$.

Glycolysis

An anaerobic metabolic pathway occurring in the cytoplasm of all cells that splits one glucose molecule into two pyruvate molecules, yielding a net of $2\,\text{ATP}$ and $2\,\text{NADH}$.

Glyceraldehyde 3-Phosphate (G3P)

A three-carbon intermediate molecule produced during glycolysis when fructose-1,6-bisphosphate is cleaved in two.

Transition Reaction

The mitochondrial matrix stage of aerobic respiration where a decarboxylase enzyme removes $\text{CO}_2$ from each pyruvate to form acetyl CoA and $\text{NADH}$.

Krebs Cycle

The cyclical reaction series in the mitochondrial matrix where a 2-carbon acetyl group binds to 4-carbon oxaloacetate to form 6-carbon citrate, yielding $\text{CO}_2$, $3\,\text{NADH}$, $1\,\text{FADH}_2$, and $1\,\text{ATP}$ per cycle.

Electron Transport System (ETS)

A chain of electron carrier proteins in the inner mitochondrial membrane that oxidizes $\text{NADH}$ and $\text{FADH}_2$, passing electrons to oxygen ($1/2\,\text{O}_2 + 2\text{H}^+ \rightarrow \text{H}_2\text{O}$) while translocating $\text{H}^+$ ions.

Chemiosmosis

The process where hydrogen ions ($\text{H}^+$) accumulated in the intermembrane compartment flow through ATP-synthase into the matrix, generating $32\text{ to }34\,\text{ATP}$.

ATP-Synthase

The membrane enzyme complex that utilizes the electrochemical gradient of $\text{H}^+$ flowing into the mitochondrial matrix to phosphorylate $\text{ADP}$ to $\text{ATP}$.

Fermentation

An anaerobic cytoplasmic pathway that follows glycolysis in the absence of oxygen to regenerate $\text{NAD}^+$ from $\text{NADH}$ without producing any additional $\text{ATP}$.

Lactic Acid Fermentation

An anaerobic pathway occurring in animal muscle cells and certain microbes where pyruvate is reduced to lactate, reoxidizing $\text{NADH}$ to $\text{NAD}^+$.

Alcoholic Fermentation

An anaerobic pathway occurring in yeast and certain microbes where pyruvate is converted to ethyl alcohol and $\text{CO}_2$, reoxidizing $\text{NADH}$ to $\text{NAD}^+$.

Catalase

An enzyme that catalyzes the decomposition of toxic hydrogen peroxide into water and oxygen gas ($2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2$).

Alcohol Dehydrogenase

The enzyme that oxidizes ethanol or breaks down methanol into toxic formaldehyde; administered ethanol acts as its competitive inhibitor to prevent methanol blindness.