Cell Structure and Function Flashcards

A complete set of vocabulary flashcards covering cell structure, organelles, membrane biology, transport mechanisms, tonicity, and body fluid electrolyte distribution based on lecture notes.

Plasma Membrane

The outer boundary of the cell that defines cell boundaries, controls interactions with other cells, and regulates the passage of materials into and out of the cell.

Cytoplasm

The intracellular fluid packed with organelles, microfilaments, microtubules, and stored inclusion products located between the plasma membrane and nucleus.

Cytosol

A jelly-like fluid composed mostly of water surrounding the nucleus, serving as the site for countles chemical reactions within the cell.

Nucleus

The largest organelle ($5\,\text{mm}$ in diameter) that controls cellular activities and contains the cell's primary complement of DNA.

Nuclear Envelope

A double-unit membrane surrounding the nucleus held together at nuclear pores.

Chromatin

Thread-like material within the nucleus containing DNA and protein that folds together to form chromosomes.

Nucleoli

Dark masses inside the nucleus where ribosomes are produced.

Rough Endoplasmic Reticulum

An extensive network of parallel unit membranes with cisternae covered in ribosomes, continuous with the nuclear envelope, that functions in protein synthesis and membrane production.

Smooth Endoplasmic Reticulum

A continuous network with rough ER lacking ribosomes, featuring tubular cisternae, that functions in lipid synthesis, detoxification, and calcium storage.

Golgi Complex

An organelle that synthesizes carbohydrates, processes proteins from the rough ER, and packages them into Golgi vesicles.

Golgi Vesicles

Irregular sacs near the Golgi complex that bud off cisternae to become lysosomes, fuse with the plasma membrane, or become secretory vesicles.

Secretory Vesicles

Vesicles that store a cell product for later release outside the cell.

Vacuole

An organelle that stores nutrients and degrades waste products.

Lysosomes

Single-membrane packages of enzymes that function in intracellular digestion, autophagy, autolysis, and glucose mobilization.

Autophagy

The lysosomal digestion of worn-out organelles and mitochondria.

Autolysis

Programmed cell death executed by lysosomal enzymes.

Peroxisomes

Organelles that neutralize free radicals, produce $\text{H}_2\text{O}_2$ during alcohol detoxification and bacterial killing, break down excess $\text{H}_2\text{O}_2$ with catalase, and break down fatty acids into acetyl groups.

Catalase

An enzyme present in peroxisomes that breaks down excess hydrogen peroxide ($\text{H}_2\text{O}_2$).

Ribosomes

Small dark granules of protein and RNA located free in the cytosol or on the rough ER surface that interpret genetic code and synthesize polypeptides.

Mitochondrion

A double-membrane powerhouse organelle that extracts energy from organic compounds to synthesize ATP; lives for $10\,\text{days}$ and reproduces independently.

Cristae

Inner membrane folds of the mitochondrion containing enzymes that synthesize ATP from energy extracted from organic compounds.

Matrix

The internal space between mitochondrial cristae containing ribosomes and small, circular mitochondrial DNA.

Cytoskeleton

A cellular network of microfilaments, intermediate filaments, and microtubules that provides internal structural support and movement.

Microfilaments

Cytoskeletal filaments ($7\,\text{nm}$ diameter) made of actin that form the membrane skeleton, support microvilli, and produce cell movement.

Intermediate Filaments

Cytoskeletal fibers ($10\,\text{nm}$ diameter) located in cell junctions that hold epithelial cells together, maintain cell shape, and resist physical stress.

Microtubules

Cylinders ($25\,\text{nm}$ diameter) composed of $13$ parallel protofilaments of tubulin that hold organelles in place, maintain cell shape, and guide vesicle transport.

Centrioles

Short cylindrical assemblies of nine groups of three microtubules that lie in the centrosome and play a key role in cell division and cilia formation.

Centrosome

An area near the nucleus containing two perpendicular centrioles involved in cell division.

Cilia

Hairlike processes ($7\text{--}10\,\text{mm}$ long) that move mucus or function in sensory perception in the inner ear, retina, and nasal cavity.

Axoneme

The structural core of cilia and flagella featuring a $9 + 2$ microtubule arrangement.

Flagellum

A long whiplike cell extension with an axoneme identical to cilia, found in humans exclusively as the tail of sperm cells.

Phospholipid Bilayer

The primary fluid matrix of the plasma membrane, consisting of $75\%$ phospholipids with hydrophilic phosphate heads on the surfaces and hydrophobic oily tails in the center.

Glycocalyx

A carbohydrate coating on the cell surface formed by glycolipids and glycoproteins.

Integral Proteins

Transmembrane proteins that pass completely through the lipid bilayer, having hydrophobic regions embedded inside and hydrophilic regions extending outwards.

Peripheral Proteins

Proteins that adhere to the intracellular surface of the membrane and anchor integral proteins to the cytoskeleton.

Ligand-Regulated Gates

Gated channel proteins that open or close in response to binding specific chemical messengers.

Voltage-Regulated Gates

Gated channel proteins that open or close in response to electrical potential changes across the plasma membrane.

Mechanically Regulated Gates

Gated channel proteins that open or close in response to physical stress like stretch or pressure.

Passive Transport

Movement of particles down their concentration gradient across a membrane without requiring ATP.

Active Transport

Carrier-mediated or vesicular movement of particles against their concentration gradient across a membrane requiring ATP input.

Filtration

The movement of particles through a selectively permeable membrane driven by hydrostatic pressure.

Hydrostatic Pressure

The force exerted on a membrane by water or blood.

Simple Diffusion

The net movement of particles from an area of high concentration to an area of low concentration as a result of random thermal motion.

Facilitated Diffusion

Carrier-mediated, passive transport of solutes across a membrane down their concentration gradient without energy consumption.

Osmosis

The net movement of water across a selectively permeable membrane from a lower solute concentration to a higher solute concentration.

Aquaporins

Channel proteins in the plasma membrane that increase the rate of osmosis.

Osmotic Pressure

The amount of hydrostatic pressure required to completely halt osmosis.

Sodium-Potassium Pump

An active transport carrier that hydrolyzes ATP to export $3\,\text{Na}^+$ and import $2\,\text{K}^+$ against their concentration gradients.

Exocytosis

Vesicular transport that expels large particles or fluids out of the cell.

Endocytosis

Vesicular transport that brings large particles, fluid droplets, or specific molecules into the cell.

Phagocytosis

A form of endocytosis in which a cell engulfs large particles or debris using pseudopods.

Pinocytosis

A form of endocytosis in which the cell takes in small droplets of extracellular fluid.

Receptor-Mediated Endocytosis

A selective form of endocytosis where specific molecules bind to cell-surface receptors and accumulate in clathrin-coated pits to form vesicles inside the cell.

Semipermeable Membrane

A membrane that allows certain compounds to pass through freely while blocking others.

Solvent

The liquid (primarily water) in which solute particles are dissolved.

Solute

A chemical substance (such as salt) dissolved inside a solvent.

Hypertonic Solution

A surrounding solution with a higher solute concentration than the cytoplasm, causing water to leave the cell.

Hypotonic Solution

A surrounding solution with a lower solute concentration than the cytoplasm, causing water to enter the cell.

Isotonic Solution

A surrounding solution whose solute concentration is equal to that of the cytoplasm, producing no net water movement.

Crenation

The shrinking or shriveling of cells resulting from water loss in a hypertonic solution.

Hemolysis

The rupture or bursting of red blood cells caused by water uptake in a hypotonic solution.

Normal Saline

A physiological saline solution composed of $9\,\text{g of NaCl per Liter of Water}$ that is isotonic to body fluids.

Ringer's Solution

A physiological fluid containing $\text{NaCl (6.5 g)}$, $\text{KCl (0.42 g)}$, $\text{CaCl}_2\text{ (0.25 g)}$, and $\text{NaHCO}_3\text{ (0.84 g) per Liter of Water}$.

Intracellular Fluid

Fluid residing inside cells, characterized by higher concentrations of potassium ($\text{K}^+$), phosphate ($\text{PO}_3^-$), and bicarbonate ($\text{HCO}_3^-$).

Extracellular Fluid

Fluid residing outside cells (including plasma and interstitial fluid), characterized by higher concentrations of sodium ($\text{Na}^+$), calcium ($\text{Ca}^{2+}$), magnesium ($\text{Mg}^{2+}$), and chloride ($\text{Cl}^-$).