Unit 2

Cell

basic structural and functional unit of life

Biomolecule

molecules like nucleic acids, proteins, carbohydrates, and lipids that make up cells

Prokaryotic cell

simple cell lacking a nucleus and membrane-bound organelles

Eukaryotic cell

complex cell with a nucleus and membrane-bound organelles

Plasma membrane

phospholipid bilayer that regulates what enters and leaves the cell

Cytoplasm

fluid interior of the cell where many metabolic reactions occur

Capsule

sticky outer layer (in some prokaryotes) for protection and adhesion

Cell wall

rigid external layer that provides shape and support (plants/fungi/bacteria)

Pili

hairlike appendages for attachment and DNA exchange in prokaryotes

Flagella

long whip-like structures used for cell movement

Nucleoid

region containing the chromosome in prokaryotes

Plasmid

small circular DNA molecule that carries extra genes in prokaryotes

Ribosome

molecular machine that synthesizes proteins

Organelle

membrane-bound compartment in eukaryotic cells with a specific function

Nucleus

organelle that stores DNA and is the site of transcription

Rough ER

endoplasmic reticulum with ribosomes that synthesizes proteins for membranes and secretion

Smooth ER

endoplasmic reticulum that synthesizes lipids and detoxifies chemicals

Golgi apparatus

modifies

Vesicle

small membrane-bound sac that transports materials within or out of the cell

Lysosome

vesicle with hydrolytic enzymes that digests macromolecules (mainly in animal cells)

Peroxisome

organelle that breaks down fatty acids and detoxifies harmful substances

Mitochondrion

organelle that produces ATP by aerobic respiration and contains its own DNA

Chloroplast

plant/algae organelle that performs photosynthesis using chlorophyll

Endomembrane system

network of organelles that synthesize

Cytoskeleton

network of protein filaments giving shape

Microfilament

actin-based filament involved in cell shape and movement

Intermediate filament

stable cytoskeletal fiber that provides mechanical strength

Microtubule

tubulin-based filament for intracellular transport and chromosome movement

Cilia

short hair-like projections that move cells or move fluid across cell surfaces

Eukaryotic flagellum

long projection used for locomotion in some eukaryotic cells

Centrosome

microtubule-organizing center important during cell division (animal cells)

Extracellular matrix (ECM)

scaffold of proteins outside animal cells that provides support and signaling

Surface area to volume ratio

relationship that limits cell size and affects exchange efficiency

Microvillus

membrane projection that increases surface area for absorption

Phospholipid bilayer

two-layered arrangement of phospholipids forming the membrane core

Fluid mosaic model

describes membrane as a fluid layer with proteins embedded and moving

Integral protein

membrane protein that spans the bilayer to help transport or signal

Peripheral protein

membrane-associated protein that binds temporarily for signaling or support

Cholesterol

lipid in animal membranes that stabilizes membrane fluidity

Glycoprotein/glycolipid

carbohydrate-attached proteins or lipids used for cell recognition and communication

Selective permeability

membrane property that controls which substances cross and maintain internal conditions

Passive transport

movement of molecules down a concentration gradient without energy

Simple diffusion

passive movement of small uncharged molecules directly across the membrane

Facilitated diffusion

passive movement of large or charged molecules via membrane proteins

Osmosis

diffusion of water across a selectively permeable membrane toward higher solute concentration

Aquaporin

channel protein that facilitates rapid water movement across membranes

Tonicity

relative solute concentration of two solutions that determines water movement and cell volume

Isotonic

solution with equal solute concentration causing no net water movement

Hypotonic

solution with lower solute concentration causing water to enter and cells to swell

Hypertonic

solution with higher solute concentration causing water to leave and cells to shrink

Turgor pressure

internal pressure in plant cells from water in the central vacuole that keeps cells rigid

Active transport

movement of substances against their gradient using energy (ATP)

Protein pump

ATP-powered membrane protein that moves ions (example: Na+/K+ pump)

Bulk transport

vesicle-mediated movement of large particles or volumes (endocytosis/exocytosis)

Endocytosis

process where the cell takes in materials by engulfing them in vesicles

Phagocytosis

type of endocytosis where large particles or cells are engulfed ("cell eating")

Pinocytosis

type of endocytosis where fluids and dissolved substances are taken up ("cell drinking")

Receptor-mediated endocytosis

selective uptake using receptor proteins and coated vesicles

Exocytosis

fusion of vesicles with the membrane to release contents outside the cell

Homeostasis

maintenance of a stable internal environment by cellular processe