BIOL 189 Unit 3 Study Guide: Cell Transport, Metabolism, Respiration, and Cell Division

Comprehensive vocabulary flashcards covering membrane structure, cellular transport, enzyme kinetics, bioenergetics, cellular respiration, fermentation, and mitosis from BIOL 189 Unit 3.

Fluid Mosaic Model

A biological model describing the cell membrane as a dynamic mosaic of diverse protein molecules embedded in or attached to a fluid phospholipid bilayer.

Phospholipid Bilayer

The amphipathic double-layer lipid foundation of cellular membranes consisting of hydrophilic phosphate heads facing outward and hydrophobic fatty acid tails pointing inward.

Integral Proteins

Membrane proteins that penetrate the hydrophobic interior of the lipid bilayer, typically possessing hydrophobic regions of nonpolar amino acids.

Peripheral Proteins

Proteins loosely bound to the surface of the cell membrane or to integral proteins, without penetrating the hydrophobic core of the bilayer.

Transmembrane Proteins

A major class of integral proteins that completely span the entire biological membrane from the extracellular side to the cytoplasmic side.

Membrane Fluidity Regulation

The homeostatic regulation of cell membrane viscosity influenced by temperature and fatty acid composition, where unsaturated fatty acids increase fluidity and saturated fatty acids decrease fluidity.

Diffusion

The spontaneous physical movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.

Osmosis

The passive transport or diffusion of free water molecules across a selectively permeable membrane toward a region of higher solute concentration.

Isotonic Solution

An environment whose solute concentration is equal to that inside the cell, resulting in no net movement of water across the plasma membrane.

Hypotonic Solution

A surrounding solution with a lower solute concentration (and higher free water concentration) compared to the cell interior, causing water to flow into the cell.

Hypertonic Solution

A surrounding solution with a higher solute concentration (and lower free water concentration) compared to the cell interior, causing water to leave the cell.

Plasmolysis

The shrinking of cytoplasm away from the rigid cell wall in a plant cell exposed to a hypertonic environment due to water loss.

Osmoregulation

The active control and maintenance of internal solute concentrations and water balance within a cell or organism.

Osmotic Effects on Animal and Plant Cells

Animal cells lyse in hypotonic solutions, stay normal in isotonic solutions, and shrivel in hypertonic solutions; plant cells are turgid (normal) in hypotonic solutions, flaccid in isotonic solutions, and plasmolyzed in hypertonic solutions.

Passive Transport

The movement of substances across a cellular membrane down their concentration gradient without requiring expenditure of metabolic energy ($ATP$).

Active Transport

The energy-dependent transport of solute particles across a biological membrane against their concentration gradient via specialized transport proteins.

Facilitated Diffusion

The passive movement of molecules down their concentration gradient through the lipid membrane with the aid of transmembrane channel or carrier proteins.

Channel Proteins

Transport proteins with hydrophilic pores that allow specific polar molecules or ions to diffuse rapidly across the plasma membrane.

Carrier Proteins

Transport proteins that bind specific solutes and undergo alternating conformational shape changes to shuttle the solutes across the membrane.

Primary Active Transport

Active transport that directly utilizes energy derived from the hydrolysis of $ATP$ to pump solute molecules against their concentration gradient.

Secondary Active Transport

Active transport powered indirectly by an electrochemical or ion gradient previously established by primary active transport.

Endocytosis

The cellular mechanism for capturing extracellular material by engulfing it with invaginations of the plasma membrane that pinch off into internal vesicles.

Exocytosis

The cellular release of intracellular substances by the fusion of internal transport vesicles with the plasma membrane.

Phagocytosis

A form of endocytosis known as 'cellular eating' wherein a cell wraps pseudopodia around large particulate matter, debris, or whole cells to form a vacuole.

Pinocytosis

A form of endocytosis known as 'cellular drinking' wherein a cell non-specifically ingests extracellular fluid droplets and dissolved solutes via pinocytic vesicles.

Receptor-Mediated Endocytosis

A selective form of endocytosis where receptor proteins on the cell surface bind specific target ligands before vesicle formation occurs.

Kinetic Energy

The form of energy associated with the relative motion of particles or matter.

Potential Energy

The stored form of energy possessed by matter as a result of its spatial location, structural arrangement, or chemical bonds.

First Law of Thermodynamics

The principle of conservation of energy stating that energy can be transformed or transferred, but it cannot be created or destroyed.

Second Law of Thermodynamics

The physical law stating that every energy transfer or transformation increases the total disorder or entropy of the universe.

Gibbs Free Energy ($\Delta G$)

The portion of a biological thermodynamic system's energy capable of performing cellular work when temperature and pressure remain uniform.

Activation Energy ($E_A$)

The minimum threshold quantity of initial energy required to strain chemical bonds and initiate a spontaneous or nonspontaneous chemical reaction.

Transition State

The unstable, high-energy molecular configuration achieved at the summit of the activation energy barrier during a chemical transformation.

Endergonic Reaction Curve

A thermodynamic graph representing a nonspontaneous, energy-absorbing reaction where the final products possess higher potential energy ($50$) than the reactants ($20$) after passing through an activation energy peak ($100$).

Exergonic Reaction

A spontaneous chemical reaction that proceeds with a net release of free energy ($\Delta G < 0$).

Endergonic Reaction

A nonspontaneous chemical reaction that requires a net absorption of free energy ($\Delta G > 0$) to occur.

Energy Coupling

The bioenergetic strategy in cells where an exergonic pathway (such as $ATP$ hydrolysis) directly powers an endergonic biological process.

Enzyme

A biological catalytic macromolecule (typically a protein) that accelerates biochemical reactions by lowering their activation energy ($E_A$).

Active Site

The specialized cleft or pocket on an enzyme where substrate molecules bind and where chemical catalysis occurs.

Substrate

The specific chemical reactant that is recognized, bound, and transformed by an enzyme at its active site.

Induced Fit

The conformational change in an enzyme's active site upon substrate binding that aligns catalytic groups and optimizes chemical catalysis.

Optimal Temperature and pH of an Enzyme

The specific environmental temperature (around $37^\text{o}C$) and pH (around $7$ to $8$) at which an enzyme demonstrates its peak catalytic velocity before denaturation begins.

Peptide Bond Formation

A condensation reaction between the carboxyl group of one amino acid and the amino group of an adjacent amino acid, releasing water to synthesize a peptide bond.

Cofactors

Non-protein chemical assistants, often inorganic ions such as zinc or iron, required for proper enzymatic catalytic function.

Coenzymes

Organic non-protein cofactors (frequently derived from vitamins) that transiently assist enzymes in carrying out biochemical reactions.

Metabolism

The collective sum of all biochemical reactions and energetic transformations occurring within a living organism.

Catabolism

Metabolic pathways that release free energy by breaking down complex macromolecules into simpler components (e.g., cellular respiration).

Anabolism

Energy-consuming metabolic pathways that synthesize complex biomolecules from simpler precursors (e.g., protein synthesis).

Adenosine Triphosphate (ATP)

The primary cellular energy currency consisting of ribose, adenine, and three phosphate groups, whose hydrolysis drives cellular work.

Phosphorylation

The chemical transfer of a phosphate group to a molecule or protein, frequently driven by kinase enzymes to alter shape, activity, or free energy.

Oxidation

The loss of electrons (or loss of hydrogen atoms) from a chemical substance during a reduction-oxidation (redox) reaction.

Reduction

The gain of electrons (or gain of hydrogen atoms) by a chemical substance during a reduction-oxidation (redox) reaction.

Oxidizing Agent

The reactant that accepts electrons in a redox reaction, thereby becoming reduced while causing another reactant to be oxidized.

Reducing Agent

The reactant that donates electrons in a redox reaction, thereby becoming oxidized while causing another reactant to be reduced.

$NAD^+$ / $NADH$

A fundamental cellular electron carrier; $NAD^+$ is the oxidized electron acceptor with less energy, whereas $NADH$ is the reduced electron carrier possessing stored high potential energy.

Substrate-Level Phosphorylation

The direct enzymatic synthesis of $ATP$ occurring when an enzyme transfers a phosphate group from an organic substrate intermediate to $ADP$.

Aerobic Cellular Respiration

A catabolic pathway requiring oxygen in which organic fuel (glucose) is oxidized to $CO_2$ and $H_2O$ to generate abundant $ATP$.

Glycolysis

The initial cytosolic metabolic stage of cellular respiration that splits one $6$-carbon glucose into two $3$-carbon pyruvate molecules, yielding a net of $2$ $ATP$ and $2$ $NADH$ without requiring oxygen.

Pyruvate Oxidation

The transition step in the mitochondrial matrix that converts each pyruvate into acetyl-CoA, generating $1$ $CO_2$ and $1$ $NADH$ per pyruvate.

Citric Acid Cycle (Krebs Cycle)

The cyclic mitochondrial matrix pathway that oxidizes acetyl groups to $CO_2$, yielding $NADH$, $FADH_2$, and $ATP$ via substrate-level phosphorylation.

Oxidative Phosphorylation

The final stage of aerobic cellular respiration occurring across the inner mitochondrial membrane, combining electron transport and chemiosmosis to produce the vast majority of $ATP$.

Electron Transport Chain (ETC)

A collection of multi-protein complexes (I, II, III, IV) and mobile electron carriers located in the inner mitochondrial membrane that transfer electrons from $NADH$ and $FADH_2$ to $O_2$ while pumping $H^+$ into the intermembrane space.

Proton-Motive Force

The potential energy stored in the transmembrane electrochemical proton ($H^+$) gradient established by electron transport across the inner mitochondrial membrane.

Chemiosmosis

An energy-coupling mechanism that harnesses the flow of protons ($H^+$) down their electrochemical gradient to drive the mechanical synthesis of $ATP$.

ATP Synthase

A complex multi-subunit molecular turbine embedded in the inner mitochondrial membrane that synthesizes $ATP$ from $ADP$ and inorganic phosphate using the energy of flowing protons.

Fermentation

An anaerobic metabolic pathway that produces $ATP$ strictly through glycolysis by transferring electrons from $NADH$ to an organic acceptor to regenerate $NAD^+$.

Lactic Acid Fermentation Reaction

The anaerobic process where pyruvate ($C_3H_4O_3$) is reduced by $NADH$ to form lactate ($C_3H_6O_3$) and regenerate $NAD^+$ for glycolysis.

Alcohol Fermentation

An anaerobic pathway that converts pyruvate into ethanol and carbon dioxide, oxidizing $NADH$ back to $NAD^+$ to sustain continuous glycolysis.

Mitosis

The division of the eukaryotic cell nucleus producing two genetically identical daughter nuclei with conserved chromosome numbers.

Somatic Cells

All diploid body cells in a multicellular organism, excluding reproductive haploid gametes (sperm and egg cells).

Interphase

The prolonged preparatory stage of the eukaryotic cell cycle between mitotic divisions, comprising $G_1$ (growth), S (DNA synthesis), and $G_2$ (final preparation) phases.

Cytokinesis

The physical division of the cytoplasm that separates the parent cell into two distinct daughter cells immediately following mitosis.

Centrosome

The primary microtubule-organizing center located near the nucleus in animal cells that coordinates mitotic spindle formation during cell division.

Centromere

The specialized narrow chromosomal region where two identical sister chromatids are held together most tightly.

Kinetochore

A specialized protein disc assembled on the centromere of each sister chromatid that anchors the spindle microtubules during mitosis.

Prophase

The first phase of mitosis characterized by the condensation of chromatin into visible chromosomes and the initiation of mitotic spindle assembly.

Prometaphase

The mitotic stage during which the nuclear envelope breaks down and spindle microtubules invade the nuclear region to bind chromosomal kinetochores.

Metaphase

The mitotic stage during which duplicated chromosomes align symmetrically along the equator or metaphase plate of the cell.

Anaphase

The mitotic stage during which centromeric cohesion is broken and sister chromatids separate into individual daughter chromosomes moving toward opposite poles.

Telophase

The concluding mitotic stage wherein nuclear envelopes reform around two sets of daughter chromosomes, nucleoli reappear, and chromatin decondenses.

Cell Cycle Checkpoint

A regulatory control stop-point in the cell cycle ($G_1$, $G_2$, and M checkpoints) where internal and external cues assess whether division should proceed.

Metastasis

The pathological process whereby cancerous cells break free from a malignant primary tumor and spread through blood or lymph vessels to establish secondary tumors in distant tissues.