Cell Biology, Metabolism, and Biological Macromolecules

Comprehensive vocabulary flashcards covering cell structure, membrane transport, biochemical pathways of cellular respiration and photosynthesis, atomic bonding, and biological macromolecules.

Metabolism

The chemical reactions in cells that break down and build up nutrients.

Anabolic reactions

Metabolic reactions that combine smaller molecules into more complex compounds, consuming more energy than the energy produced.

Catabolic reactions

Metabolic reactions that break large molecules down into smaller ones, producing more energy than the energy consumed.

Redox reactions

Chemical reactions where electrons are transferred from one molecule to another.

Reducing agent

A molecule that donates electron(s) in a chemical oxidation-reduction reaction and becomes oxidized.

Oxidizing agent

A molecule that accepts electron(s) in a chemical oxidation-reduction reaction and becomes reduced.

Chemiosmosis

The process that produces approximately $90\%$ of cellular $ATP$ using the kinetic energy of protons falling down an electrochemical gradient via the enzyme $ATP$ synthase.

Glycolysis

The initial $10$-step metabolic pathway of glucose catabolism occurring in the cytoplasm that converts one glucose molecule into two pyruvate molecules, yielding a net gain of $2\,ATP$ and $2\,NADH$.

Citric acid cycle

A cyclic metabolic pathway in the mitochondrial matrix where the acetyl group of acetyl CoA combines with oxaloacetate to form citrate, generating $NADH$, $FADH_2$, $CO_2$, and $ATP$ or $GTP$.

Electron transport chain (ETC)

A series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from $NADH$ and $FADH_2$ to $O_2$, pumping protons into the intermembrane space.

Glycogenesis

The metabolic process of producing glycogen from glucose molecules, stimulated by the hormone insulin.

Glycogenolysis

The metabolic process of glycogen catabolism into glucose molecules, stimulated by the hormone glucagon.

Active site

The specific region of an enzyme composed of catalytic and binding sites where substrate molecules bind and undergo chemical transformation.

Competitive inhibitor

An inhibitor molecule possessing a shape similar to the substrate that competes directly with the substrate for the enzyme's active site.

Noncompetitive inhibitor

An inhibitor that binds to an enzyme at an allosteric location other than the active site, inducing a conformational change that slows the reaction rate.

Photoautotrophs

Organisms such as plants, algae, and cyanobacteria that use sunlight to manufacture organic food compounds from carbon dioxide and water.

RuBisCO

Ribulose bisphosphate carboxylase oxygenase; an enzyme that catalyzes carbon fixation in the Calvin cycle by adding $CO_2$ to RuBP, but can also catalyze photorespiration when functioning as an oxygenase.

Cytology

The scientific study of cells.

Cell theory

The foundational biological principle stating that all living things are composed of cells, all cells arise from preexisting cells, cells contain hereditary material passed during division, cell chemical composition is similar, and life's metabolic processes occur within cells.

Fluid mosaic model

A model of the plasma membrane proposed in 1972 by S.J. Singer and G.L. Nicolson, describing it as a dynamic fluid structure composed of phospholipids, cholesterol, proteins, and carbohydrates.

Integral proteins

Membrane proteins that are integrated completely into the phospholipid bilayer, possessing hydrophobic regions that span the membrane.

Peripheral proteins

Membrane proteins located exclusively on the exterior or interior surfaces of the phospholipid bilayer.

Diffusion

The passive movement of a substance from an area of higher concentration down toward an area of lower concentration until equilibrium is reached.

Facilitated diffusion

A form of passive transport that moves polar molecules and ions down their concentration gradient using transmembrane channel or carrier proteins without cellular energy expenditure.

Osmosis

The diffusion of water across a semipermeable membrane from an area of higher water concentration (lower solute osmolarity) to lower water concentration (higher solute osmolarity).

Hypertonic solution

An extracellular solution with a higher solute concentration and lower water concentration than the cell's cytosol, causing water to leave the cell.

Hypotonic solution

An extracellular solution with a lower solute concentration and higher water concentration than the cell's cytosol, causing water to enter the cell.

Turgor pressure

The outward pressure exerted by the plasma membrane against the rigid cell wall in walled cells, critical for structural support and growth.

Active transport

The energy-requiring transport of molecules or ions across a membrane against their concentration or electrochemical gradient.

Sodium-potassium pump

An intra-membrane active transport pump ($Na^+/K^+$ ATPase) that hydrolyzes $ATP$ to pump two $K^+$ ions into the cell while expelling three $Na^+$ ions out of the cell.

Nuclear envelope

A double membrane punctuated by nuclear pores that surrounds the cell nucleus, segregating genetic material from the cytoplasm and regulating molecular traffic.

Nucleolus

A distinct, condensed region inside the nucleus dedicated to the production of ribosomal RNA ($rRNA$) and the assembly of ribosomes.

Rough endoplasmic reticulum (RER)

A network of membranous sacs studded with ribosomes that processes, sorts, and modifies proteins synthesized for membranes or secretion.

Smooth endoplasmic reticulum (SER)

A tubular membranous organelle devoid of ribosomes that synthesizes carbohydrates, lipids, and steroid hormones, detoxifies poisons, and stores calcium ions ($Ca^{2+}$).

Golgi complex

An organelle consisting of stacked, flattened saccules that receives vesicles from the ER at its cis face, modifies and sorts lipids and proteins, and dispatches them from its trans face.

Lysosomes

Organelles found in animal cells containing acidic digestive enzymes that break down large biomolecules, ingested food particles, and worn-out cellular organelles.

Peroxisomes

Small, single-membrane organelles that carry out oxidation reactions to degrade fatty acids and amino acids and detoxify bodily poisons.

Cytoskeleton

A dynamic intracellular protein network composed of microfilaments, intermediate filaments, and microtubules that maintains cell shape, anchors organelles, and enables cellular locomotion.

Microfilaments

The narrowest cytoskeletal filaments, constructed from actin protein subunits, responsible for cellular motility, contraction, and structural stabilization.

Microtubules

Hollow cytoskeletal cylinders made of tubulin subunits that guide chromosome movement during cell division, act as tracks for organelle movement, and form cilia and flagella.

Centrosome

The microtubule-organizing center of animal cells, containing two centrioles oriented at right angles, each formed from nine triplets of microtubules.

Plasmodesmata

Channels that penetrate plant cell walls to directly connect adjacent cytoplasms and facilitate intercellular transport of water and nutrients.

Tight junctions

Watertight protein seals formed between adjacent animal epithelial cells that prevent extracellular fluid and substances from leaking across the tissue sheet.

Desmosomes

Intercellular adhesion junctions in animal cells formed by cadherin proteins that act as spot welds to link cells in tissues subjected to stretching.

Gap junctions

Intercellular channels between animal cells formed by six connexin proteins (connexons) that allow water, ions, and small molecules to pass directly between cells.

Atomic number

The fundamental identifier of a chemical element, defined by the specific number of protons located in its atomic nucleus.

Atomic mass

The calculated mass of an atom measured in atomic mass units ($\text{amu}$), approximately equal to the combined total of its protons and neutrons.

Isotopes

Different forms of the same chemical element that contain identical numbers of protons but different numbers of neutrons, resulting in different mass numbers.

Octet rule

The chemical guideline stating that atoms achieve their most stable configuration when their outermost valence shell contains eight electrons (or two for the innermost shell).

Covalent bond

A strong chemical bond formed when two or more atoms share pairs of valence electrons to fill their outer electron shells.

Ionic bond

A chemical bond formed through the electrostatic attraction between oppositely charged ions following the donation or acceptance of electrons.

Polar covalent bond

A covalent bond wherein electrons are shared unequally between atoms due to differences in electronegativity, generating partial positive and negative charges.

Hydrogen bond

A weak intermolecular electrostatic attraction between the slightly positive ($\delta^+$) hydrogen atom of a polar covalent bond and a slightly negative ($\delta^-$) atom of an adjacent polar molecule.

Van der Waals forces

Weak, intermittent attractions between molecules in close proximity caused by transient, asymmetric fluctuations in electron density.

Specific heat

The quantity of heat energy required to raise the temperature of one gram of a substance by $1^\circ\text{C}$; for water, this equals $1\,\text{calorie}$.

Heat of vaporization

The quantity of heat energy required to convert one gram of a liquid substance into vapor; for water, this equals $540\,\text{calories}$.

Cohesion

The intermolecular attraction that causes molecules of the same substance to stick together, as seen with water molecules forming hydrogen bonds at a liquid-gas interface.

Surface tension

The capacity of a liquid's surface to resist rupture when subjected to external tension or stress, driven by cohesive hydrogen bonding.

Monosaccharide

A simple single sugar molecule containing $3$ to $7$ carbon atoms and a carbonyl group, acting as a primary monomer unit for carbohydrates.

Disaccharide

A carbohydrate molecule composed of two monosaccharide units linked together, such as sucrose (glucose and fructose) or lactose (glucose and galactose).

Polysaccharide

A long chain polymer consisting of multiple monosaccharide monomers linked together, such as glycogen, starch, and cellulose.

Saturated fatty acid

A long hydrocarbon chain containing no carbon-carbon double bonds, fully saturated with hydrogen atoms, that remains solid at room temperature.

Unsaturated fatty acid

A long hydrocarbon chain containing one or more carbon-carbon double bonds that introduce structural kinks, causing the substance to remain liquid at room temperature.

Triglycerides

The most abundant energy-storing fats in the body, consisting of three fatty acid chains bonded to a single glycerol backbone and containing $9\,\text{kcal}/g$.

Steroids

Lipids characterized by a core structure of four fused carbon rings, functioning in membrane stability (cholesterol), reproduction (testosterone and estrogen), and stress regulation (cortisol).

Peptide bond

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

Denaturation

The structural unfolding or disruption of a protein's functional three-dimensional conformation caused by extreme variations in temperature or pH.

Enantiomers

Molecules that share the same chemical formula and covalent bonding connectivity but differ in three-dimensional spatial orientation as non-superimposable mirror images.

Nucleotide

The monomer subunit of nucleic acids, consisting of a pentose sugar, a nitrogenous base (A, T, C, G, or U), and a phosphate group.