Chapter 03 Cellular Form and Function

Vocabulary flashcards covering key terms from Chapter 03 Cellular Form and Function.

Cell theory

Generalizations: All organisms are composed of cells and cell products; a cell is the simplest structural and functional unit of life; an organism’s structure and functions arise from activities of cells; cells come only from preexisting cells.

Cytology

The scientific study of cells.

Plasma membrane

Defines the boundaries of the cell; composed of lipids and proteins; phospholipid bilayer with hydrophilic heads and hydrophobic tails; contains cholesterol, glycolipids, and glycoproteins; forms the glycocalyx.

Cytoplasm

The internal cellular contents between the plasma membrane and the nucleus, including cytosol and organelles.

Cytosol

The clear, gel-like intracellular fluid within the cytoplasm.

Nucleus

The organelle that houses the cell’s genetic material (DNA) and acts as a control center.

Extracellular fluid (ECF)

Fluid located outside cells, including tissue fluid, blood plasma, lymph, and cerebrospinal fluid.

Glycocalyx

Carbohydrate moieties on glycoproteins and glycolipids on the extracellular face of the plasma membrane; contributes to protection, immunity, cell adhesion, and signaling.

Microvilli

Extensions of the plasma membrane (1–2 μm) that increase surface area; contain actin filaments and form a brush border in absorptive cells.

Cilia

Hair-like projections from the cell surface; can be nonmotile (antenna) or motile and beat in coordinated waves to move substances across the surface.

Axoneme

The core of a cilium or flagellum, typically a 9+2 arrangement of microtubules that powers movement.

Basal body

Structure that anchors a cilium or flagellum to the cell; derived from a centriole.

Dynein arms

Motor proteins that drive the bending motion of cilia and flagella by sliding microtubules.

Flagellum

Whip-like tail (as in sperm) used for locomotion; longer than cilia and moves in a wave-like manner.

Pseudopods

Temporary projections of a cell used for locomotion and for capturing particles (phagocytosis).

Cytoskeleton

Network of protein filaments (microfilaments, intermediate filaments, microtubules) that provides support and aids in movement.

Microfilaments

Thin actin filaments (~6 nm) that support the cell surface and enable movement and endocytosis/exocytosis.

Intermediate filaments

8–10 nm filaments (e.g., keratin) that provide tensile strength and structural support.

Microtubules

25 nm filaments made of tubulin; radiate from the centrosome; organize organelles, serve as tracks for motor proteins, form cilia/flagella scaffolds and the mitotic spindle.

Terminal web

Membrane skeleton basal network of microfilaments reinforcing the apical surface and supporting microvilli.

Nucleolus

A region within the nucleus where ribosomal RNA is synthesized and ribosome assembly begins.

Chromatin

DNA and protein complexes inside the nucleus; condenses to form chromosomes during division.

Nuclear envelope

Double membrane surrounding the nucleus; perforated by nuclear pores.

Nuclear pores

Channels formed by a ring of proteins that regulate molecular traffic through the nuclear envelope.

Nuclear lamina

A supportive network of protein filaments lining the inner surface of the nuclear envelope.

Endoplasmic reticulum (ER)

A network of membranous channels; rough ER is studded with ribosomes and synthesizes proteins; smooth ER lacks ribosomes and synthesizes lipids, detoxifies, and stores calcium.

Rough endoplasmic reticulum

ER with ribosomes; synthesizes proteins for membranes, lysosomes, or secretion.

Smooth endoplasmic reticulum

ER lacking ribosomes; synthesizes lipids, detoxifies drugs, and stores calcium.

Ribosomes

Ribonucleoprotein particles that synthesize proteins by translating mRNA; found free in cytosol and on rough ER.

Golgi complex

Stack of flattened membranes that modifies, sorts, and packages proteins into vesicles for secretion or delivery to organelles.

Lysosomes

Membrane-bound sacs containing enzymes that digest proteins, nucleic acids, and other substrates; enable autophagy and autolysis.

Peroxisomes

Organelles that oxidize organic molecules; contain catalase to break down hydrogen peroxide; detoxify harmful substances.

Mitochondria

Powerhouses of the cell; double-membrane organelles where ATP is produced; contain cristae and matrix and own mitochondrial DNA.

Centrioles

Cylindrical organelles composed of microtubules; play a key role in cell division and form basal bodies for cilia/flagella.

Centrosome

Region near the nucleus containing a pair of centrioles; organizes microtubules during cell division.

Inclusions

Storage products or foreign materials in the cytoplasm; not enclosed by a membrane and not essential for survival.

Phagocytosis

Endocytosis that engulfs large particles; forms a phagosome that fuses with a lysosome for digestion.

Pinocytosis

Endocytosis of liquid droplets containing molecules; cellular “drinking.”

Receptor-mediated endocytosis

Endocytosis triggered by binding of ligands to specific receptors; forms clathrin-coated vesicles.

Exocytosis

Process by which cells export material by vesicle fusion with the plasma membrane; also replenishes membrane.

Vesicular transport

Transport of materials via membrane-bound vesicles, including endocytosis, exocytosis, and transcytosis.

Facilitated diffusion

Carrier-mediated transport that moves solutes down their concentration gradient without using ATP.

Primary active transport

Movement of solutes against their gradient using energy from ATP; e.g., Na+/K+ ATPase and calcium pumps.

Secondary active transport

Indirect use of ATP: transport relies on the gradient created by primary active transport (e.g., SGLT).

Uniport

Carrier that moves a single type of solute across the membrane.

Symport

Carrier that moves two or more solutes in the same direction across the membrane.

Antiport

Carrier that moves two or more solutes in opposite directions across the membrane.

Filtration

Movement of particles through a membrane driven by physical pressure.

Simple diffusion

Net movement of solutes from high to low concentration; does not require a membrane or energy.

Osmosis

Net movement of water across a selectively permeable membrane toward higher solute concentration; often facilitated by aquaporins.

Aquaporin

Water-channel proteins that facilitate rapid water movement across the membrane.

Osmolarity

Total osmotic concentration of nonpermeating solutes per liter of solution; typically around 300 mOsm/L in body fluids.

Tonicity

Effect of surrounding solution on cell volume due to solute concentration and water movement.

Isotonic

Solution with equal solute concentration to which there is no net water movement; cells retain their volume.

Hypotonic

Solution with lower nonpermeating solute concentration than the cell; water enters cell, potentially causing lysis.

Hypertonic

Solution with higher nonpermeating solute concentration than the cell; water leaves the cell, causing crenation.

Na+/K+ ATPase

Sodium–potassium pump; a primary active transport protein that pumps 3 Na+ out and 2 K+ in per ATP hydrolyzed, maintaining gradients and membrane potential.