Module 2: Energetics and Cellular Processes Vocabulary

Vocabulary flashcards covering key terms and concepts in protein structure, enzyme function, cellular energetics, photosynthesis, and cellular respiration.

Catabolic Enzymes

Enzymes that help digest food by breaking larger polymer molecules into smaller monomers.

Anabolic Enzymes

Enzymes that synthesize larger molecules from smaller constituent molecules.

Amino Acid

The monomer building block of proteins, consisting of a central alpha carbon atom attached to an amino group ($\text{NH}_2$), a carboxyl group ($\text{COOH}$), a hydrogen atom, and a variable side chain (R group).

R Group

The variable atom or chemical group attached to the central carbon of an amino acid that determines its unique identity and chemical properties.

Essential Amino Acids

Amino acids that an organism cannot synthesize on its own and must obtain directly through its diet.

Peptide Bond

The covalent bond formed between the carboxyl group of one amino acid and the amino group of another during protein synthesis.

Primary Structure

The unique linear sequence of amino acids in a polypeptide chain, encoded by genetic information in DNA.

Secondary Structure

The localized folding of a polypeptide chain into shapes such as $\alpha$-helices or $\beta$-sheets, stabilized by hydrogen bonds along the backbone.

Tertiary Structure

The overall three-dimensional folded shape of a single polypeptide, stabilized by chemical interactions between amino acid R groups.

Quaternary Structure

The structural arrangement formed when two or more individual polypeptide subunits assemble together to make a functional protein complex.

Activation Energy

The minimum amount of energy required for reactant molecules to reach a transition state and undergo a chemical reaction.

Enzyme

A biological catalyst (usually a protein) that increases the rate of specific chemical reactions by lowering their activation energy.

Substrate

The specific chemical reactant molecule to which a particular enzyme binds.

Active Site

The specific region within an enzyme where substrate molecules bind and catalysis takes place.

Denaturation

The process in which environmental factors break the weak bonds maintaining a protein's folded shape, causing a loss of functional 3D structure while preserving the primary amino acid sequence.

Buffer

A solution capable of absorbing excess $\text{H}^+$ or $\text{OH}^-$ ions to prevent drastic changes in pH and maintain homeostatic conditions.

First Law of Thermodynamics

The law stating that the total amount of energy in the universe is constant; energy can be transformed from one form to another, but cannot be created or destroyed.

Second Law of Thermodynamics

The principle stating that every energy transformation is inefficient, resulting in the loss of usable energy as heat and an increase in system entropy.

Entropy

A quantitative measure of randomness, disorder, or low energy within a physical or biological system.

Metabolism

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

Exergonic Reaction

A chemical reaction that net releases energy into its surroundings.

Endergonic Reaction

A chemical reaction that absorbs energy from its surroundings, requiring an input of energy to proceed.

ATP (Adenosine Triphosphate)

A nucleotide composed of adenine, ribose, and three phosphate groups that acts as the primary energy currency of the cell.

Diffusion

The passive net movement of a substance down its concentration gradient from an area of higher concentration to an area of lower concentration.

Osmosis

The diffusion of water molecules across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Tonicity

A measure of the relative solute and water concentrations of two solutions separated by a semi-permeable membrane, determining the net direction of osmosis.

Hypotonic Solution

A solution containing a lower concentration of solutes (and a higher concentration of water) relative to another solution.

Hypertonic Solution

A solution containing a higher concentration of solutes (and a lower concentration of water) relative to another solution.

Isotonic Solution

A solution having the same solute concentration as another solution, resulting in no net movement of water across a membrane.

Facilitated Diffusion

The passive transport of molecules or ions across a cell membrane down their concentration gradient using specialized channel or carrier proteins.

Active Transport

The transport of substances across a cell membrane against their concentration gradient, requiring an energy source such as ATP.

Photoautotroph

An organism, such as a plant or alga, that uses light energy to synthesize its own organic food molecules.

Heterotroph

An organism that cannot synthesize its own food and must acquire carbon and energy by consuming other organisms.

Chloroplast

The double-membrane-bound organelle in eukaryotic autotrophs where photosynthesis takes place.

Thylakoid

A disc-shaped membrane structure inside a chloroplast containing chlorophyll where light-dependent reactions occur.

Stroma

The fluid-filled space surrounding the granum inside a chloroplast where the Calvin cycle reactions occur.

Light-Dependent Reactions

The first stage of photosynthesis in which solar energy is captured by pigments on thylakoid membranes to generate ATP, NADPH, and oxygen gas.

Calvin Cycle

The second stage of photosynthesis occurring in the stroma, where chemical energy from ATP and NADPH drives the conversion of inorganic $\text{CO}_2$ into organic sugar.

Photosystem

A multiprotein complex embedded in thylakoid membranes consisting of light-harvesting antenna proteins and a reaction center that absorbs solar energy to excite electrons.

Chemiosmosis

The process of synthesizing ATP using energy derived from a proton ($\text{H}^+$) concentration gradient across a membrane.

Carbon Fixation

The initial conversion of inorganic carbon dioxide gas ($\text{CO}_2$) into organic biological molecules.

Rubisco

The enzyme that catalyzes the attachment of $\text{CO}_2$ to ribulose bisphosphate (RuBP) during the carbon fixation phase of the Calvin cycle.

Aerobic Cellular Respiration

The metabolic process that uses oxygen to break down glucose, converting chemical energy into ATP while releasing $\text{CO}_2$ and water.

Glycolysis

The cytoplasmic anaerobic pathway that breaks down one 6-carbon glucose molecule into two 3-carbon pyruvate molecules, yielding a net 2 ATP and 2 NADH.

Pyruvate Oxidation

The step in the mitochondrial matrix where pyruvate is converted into acetyl-CoA, producing NADH and releasing one $\text{CO}_2$ per pyruvate.

Krebs Cycle

A cyclical series of reactions in the mitochondrial matrix that oxidizes acetyl groups to $\text{CO}_2$, generating NADH, FADH2, and ATP.

Oxidative Phosphorylation

The cellular respiration process comprising the electron transport chain and chemiosmosis on the inner mitochondrial membrane, generating the majority of cellular ATP.

Fermentation

An anaerobic pathway consisting of glycolysis followed by electron transfer from NADH to an organic molecule to regenerate $\text{NAD}^+$ for continued glycolysis.