Cell Biology, Membrane Structure, and the Chemical Basis of Life

Vocabulary flashcards covering biological membrane structure, cell organelles, transport mechanisms, cell theory, and chemical bases of life.

Cell Theory

The foundational biological principles stating that all living organisms are composed of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

Homeostasis

The process by which organisms maintain a stable internal environment despite changes in external conditions.

Fluid Mosaic Model

A model proposed by J. Singer and G. Nicolson in 1972 describing the cell membrane as a two-dimensional fluid of phospholipid molecules wherein embedded proteins loosely associate in an ever-changing configuration.

Phospholipid

An amphipathic membrane lipid consisting of a hydrophilic head (glycerol and phosphate) and two hydrophobic fatty acid tails.

Glycolipid

A lipid with an attached carbohydrate located on the external face of the cell membrane that functions in cell signaling and recognition.

Integral Membrane Protein

An amphipathic membrane protein that is firmly bound to the lipid bilayer.

Transmembrane Protein

A specific type of integral protein that extends completely through the biological membrane.

Peripheral Membrane Protein

A protein located on the inner or outer surface of the plasma membrane, bound to exposed regions of other membrane components.

Cryofracture

A laboratory method used to freeze and fracture cell membranes to study their structure, composition, and asymmetry.

Simple Diffusion

The spontaneous movement of particles down their concentration gradient (from high to low concentration) directly across the lipid bilayer without requiring transport proteins or energy.

Facilitated Diffusion

Passive transport of solutes across a membrane down their concentration gradient facilitated by specific channel or carrier proteins.

Osmosis

The passive diffusion of water molecules across a selectively permeable membrane from a region of higher water concentration to lower water concentration.

Aquaporin

A channel protein that facilitates the rapid movement of water molecules across cell membranes.

Isotonic Solution

A solution with the same solute concentration as the cell cytosol, resulting in no net water movement across the cell membrane.

Hypertonic Solution

A solution with a higher solute concentration than the cytosol, causing animal cells to lose water and shrink.

Hypotonic Solution

A solution with a lower solute concentration than the cytosol, causing animal cells to gain water, swell, and potentially burst.

Active Transport

The movement of substances across a membrane against their concentration gradient, requiring metabolic energy in the form of $\text{ATP}$.

Sodium-Potassium Pump

An active transport antiporter system that uses $\text{ATP}$ to export sodium ions ($\text{Na}^+$) out of the cell and import potassium ions ($\text{K}^+$) into the cell.

Uniporter

A carrier protein that transports a single type of solute in one direction across the membrane.

Symporter

A secondary active transporter protein that moves two different substances in the same direction across the membrane.

Antiporter

A secondary active transporter protein that moves two different substances in opposite directions across the membrane.

Cotransport

An indirect active transport mechanism in which the diffusion of one substance down its concentration gradient drives the transport of another substance against its gradient.

Exocytosis

An active transport process where intracellular vesicles export large molecules by fusing with the plasma membrane.

Endocytosis

An active transport process where cells import extracellular materials via phagocytosis, pinocytosis, or receptor-mediated endocytosis.

Transmission Electron Microscope (TEM)

A microscope that passes an electron beam through a specimen to provide detailed two-dimensional views of internal cellular structures.

Scanning Electron Microscope (SEM)

A microscope that scans specimen surfaces with an electron beam to generate three-dimensional images of cellular surface features.

Nucleus

The eukaryotic organelle bounded by a double membrane that stores DNA, controls metabolic activities, and directs protein synthesis.

Nucleolus

A dense region inside the cell nucleus where rRNA synthesis and ribosomal subunit assembly occur.

Rough Endoplasmic Reticulum

A network of internal membranes studded with ribosomes that synthesizes and processes proteins.

Smooth Endoplasmic Reticulum

A ribosome-free membrane network involved in lipid synthesis, carbohydrate metabolism, chemical detoxification, and calcium ion storage.

Golgi Apparatus

An organelle composed of flattened membranous sacs (cisternae) that modifies, sorts, and packages proteins and lipids for secretion or delivery to organelles.

Lysosome

A membrane-bound sac containing hydrolytic enzymes operating at an acidic pH of $\text{pH} \thickapprox 5$ used for intracellular digestion.

Peroxisome

An organelle containing enzymes that metabolize fatty acids, detoxify harmful compounds, and produce hydrogen peroxide as a byproduct.

Mitochondria

Double-membrane eukaryotic organelles that generate metabolic energy in the form of $\text{ATP}$ through cellular respiration.

Chloroplast

A chlorophyll-containing plant organelle that converts light energy into chemical energy through photosynthesis.

Microtubules

Hollow cytoskeletal tubes composed of tubulin that maintain cell shape, move chromosomes during division, and form tracks for organelle movement.

Microfilaments

Cytoskeletal fibers made of actin filaments involved in cell movement, muscle contraction, and structural support.

Intermediate Filaments

Fibrous cytoskeletal elements that provide mechanical strength and stabilize overall cell shape.

Extracellular Matrix (ECM)

A network of carbohydrates and fibrous proteins, particularly collagen, surrounding animal cells to provide structural support and cell attachment.

Valence Electrons

Electrons located in the outermost shell of an atom that determine its chemical reactivity and bonding behavior.

Mole (mol)

A unit of measurement representing $6.022 \times 10^{23}$ particles (Avogadro's number) of a substance.

Covalent Bond

A strong chemical bond formed when two atoms share one or more pairs of valence electrons.

Ionic Bond

A chemical bond resulting from the electrostatic attraction between oppositely charged ions created by electron transfer.

Hydrogen Bond

A weak electrostatic attraction between a hydrogen atom covalently bonded to an electronegative atom ($\text{O}$, $\text{N}$, or $\text{F}$) and another electronegative atom.

Acid

A proton donor that releases hydrogen ions ($\text{H}^+$) in solution, resulting in a pH value below $7$.

Base

A proton acceptor that binds hydrogen ions ($\text{H}^+$) or releases hydroxide ions ($\text{OH}^-$) in solution, resulting in a pH value above $7$.

Buffer

A chemical compound or mixture that resists changes in solution pH by accepting or releasing hydrogen ions ($\text{H}^+$).

Isomers

Molecules that possess identical chemical formulas but distinct structural arrangements and biological properties.

Monosaccharide

The simplest monomeric carbohydrate consisting of a single sugar molecule, such as glucose.

Peptide Bond

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

Denaturation

The loss of a protein's secondary, tertiary, or quaternary structure and biological activity caused by heat, pH extremes, or chemical exposure.

Nucleotide

The monomer of nucleic acids composed of a five-carbon sugar, a phosphate group, and a nitrogenous base.