Chapter Three (PART TWO)

Vocabulary flashcards covering key cell biology concepts from the notes.

Cell

The smallest unit of life; carries out metabolic activities and forms tissues/organs.

Nucleus

Contains DNA and directs cell activities; enclosed by a double-layer nuclear envelope with pores; contains nucleoplasm and nucleolus.

Nucleolus

Dense region inside the nucleus; site of ribosome production (RNA and proteins).

Nuclear envelope

Double membrane surrounding the nucleus; contains nuclear pores for material passage between nucleus and cytoplasm.

Nuclear pores

Openings in the nuclear envelope that regulate movement of substances between nucleus and cytoplasm.

Chromatin

Loosely coiled DNA-protein fibers in the nucleus; condenses into chromosomes during cell division.

Chromosome

Condensed DNA during cell division.

Nucleoplasm

Fluid inside the nucleus.

Cytoplasm

Everything inside the cell except the nucleus; includes cytosol, organelles, and cytoskeleton.

Cytosol

The clear liquid portion of the cytoplasm in which organelles are suspended.

Organelles

Specialized, membrane-bound (or nonmembranous) structures within the cytoplasm that perform specific cell functions.

Endoplasmic Reticulum

Membrane-bound network that transports materials; two types: rough (with ribosomes) and smooth (lipid synthesis, drug metabolism).

Rough Endoplasmic Reticulum (Rough ER)

ER studded with ribosomes; synthesizes and processes proteins.

Smooth Endoplasmic Reticulum (Smooth ER)

ER lacking ribosomes; synthesizes lipids, absorbs fats, and metabolizes drugs.

Ribosomes

Tiny RNA-protein particles that synthesize proteins; not membranous; may be free or attached to rough ER.

Golgi apparatus

Flattened membranous sacs that refine, package, and transport proteins from the rough ER; vesicles bud off for secretion.

Vesicles

Membranous sacs that store and transport substances within or between cells.

Mitochondria

Energy-producing organelles; produce ATP via cellular respiration; contain cristae and own DNA; multiply by division.

Cristae

Folds of the inner mitochondrial membrane that increase surface area for energy production.

Lysosomes

Membranous sacs with enzymes that digest nutrients, debris, and worn-out cell parts; abundant in macrophages and liver.

Peroxisomes

Membranous sacs with enzymes that break down fatty acids and detoxify substances like hydrogen peroxide; abundant in liver and kidney cells.

Cytoskeleton

Network of microfilaments, intermediate filaments, and microtubules that support the cell and organize its interior.

Microfilaments

Thin actin filaments; enable movement and help form muscle cell myofibrils.

Microtubules

Tubulin filaments; form the cytoskeleton and spindle apparatus during cell division.

Intermediate fibers

Cytoskeletal elements with varying proteins; provide mechanical support; abundant in skin cells and neurons.

Centrosome

Nonmembranous structure with two centrioles; organizes spindle fibers during cell division.

Cilia

Short, motile projections from the cell surface that move fluids across surfaces (e.g., respiratory epithelium).

Flagella

Long, single motile projection; sperm tail enables movement.

Cell membrane (plasma membrane)

Boundary that encloses the cell and regulates entry/exit; participates in signal transduction and cell adhesion; extremely thin and selectively permeable.

Phospholipid bilayer

Basic framework of the membrane with hydrophilic heads outward and hydrophobic tails inward; forms a fluid, semi-permeable barrier.

Cholesterol (membrane)

Sterol molecules embedded in the bilayer that stabilize membrane and reduce permeability to water-soluble substances.

Membrane proteins

Proteins in the membrane that perform functions such as transport, receptors, and signaling; include integral, transmembrane, and peripheral varieties.

Glycoproteins

Proteins with carbohydrate groups attached; used for cell identification and recognition by the immune system.

CAMs (cell adhesion molecules)

Membrane proteins that mediate interactions between cells and other cells or the extracellular matrix.

Receptors

Proteins on the cell surface that bind ligands to initiate cellular responses (signal transduction).

Diffusion

Passive movement of molecules from high to low concentration due to random motion; down the concentration gradient.

Osmosis

Diffusion of water across a selectively permeable membrane toward higher solute concentration (higher osmotic pressure).

Facilitated diffusion

Transport of substances across the membrane via membrane proteins (ion channels or carrier proteins); rate limited by carrier availability.

Ion channels

Proteins that form pores allowing specific ions to cross the cell membrane.

Active transport

Movement of substances against their concentration gradient using cellular energy (ATP) and carrier proteins.

Na+/K+ ATPase pump

Pumps Na+ out and K+ into the cell using ATP; can account for up to ~40% of a cell’s energy use.

Endocytosis

Process of moving substances into the cell via vesicles formed from the plasma membrane.

Exocytosis

Process of releasing materials from the cell when a vesicle fuses with the membrane.

Pinocytosis

“Cell drinking”; nonspecific uptake of extracellular fluid and dissolved solutes via vesicles.

Phagocytosis

“Cell eating”; uptake of solid particles (e.g., bacteria) by phagocytes, vesicle fusion with lysosomes for digestion.

Receptor-mediated endocytosis

Selective vesicle formation triggered by binding of ligands to specific receptors on the membrane.

Interphase

Cell cycle phase before division; cell grows and synthesizes DNA, membranes, and organelles; includes G1, S, and G2.

G1 phase

First growth phase; cell grows and carries out normal functions.

S phase

DNA synthesis phase; genetic material is replicated.

G2 phase

Second growth phase; cell prepares for mitosis.

Mitosis

Nuclear division that results in two daughter nuclei; followed by cytokinesis.

Prophase

Mitosis phase where chromosomes condense, centrioles move to poles, spindle forms, and nuclear envelope breaks down.

Metaphase

Chromosomes align at the cell equator; spindle fibers attach to centromeres.

Anaphase

Sister chromatids separate and are pulled toward opposite poles.

Telophase

Nuclear envelopes reform around two sets of chromosomes; chromosomes decondense.

Cytokinesis

Division of the cytoplasm; cleavage furrow forms and two separate daughter cells result.

Meiosis

Cell division for production of gametes; reduces chromosome number by half.

Differentiation

Process by which cells become specialized in form and function; humans have many cell types; gene expression changes drive this.

Stem cells

Undifferentiated cells capable of self-renewal and giving rise to specialized cells.

Progenitor cells

Daughter cells of stem cells that are partially specialized and can differentiate further.

Telomeres

Protective chromosome end sequences that shorten with each cell division; contribute to the limit on cell division.

Apoptosis

Programmed cell death; a normal developmental process with orderly steps.

Isotonic

Solution with the same osmotic pressure as body fluids; no net water movement across cell membranes.

Hypertonic

Solution with higher osmotic pressure than body fluids; cells lose water and shrink.

Hypotonic

Solution with lower osmotic pressure than body fluids; cells take in water and swell.

Osmotic pressure

Pressure required to raise a volume of water; greater impermeable solutes increase osmotic pressure.