ch 3 reduced

Cell

The basic unit responsible for all structural and functional properties of a living organism.

Common Cell Shapes

Squamous (flat), polygonal (angular), stellate (star-shaped), cuboidal (square), columnar (tall), spheroid/ovoid (round/oval), discoid (disc), fusiform (tapered), fibrous (threadlike).

Cytoplasm vs. Cytosol

Cytoplasm contains organelles, cytoskeleton, and cytosol; cytosol is the intracellular fluid.

Plasma Membrane

Defines the cell boundary, controls movement of substances, and governs interactions with other cells.

Phospholipid Bilayer

Phospholipids have hydrophilic heads facing water and hydrophobic tails facing inward.

Cholesterol

About 20% of membrane lipids; helps hold phospholipids in place and can stiffen the membrane.

Glycocalyx

Carbohydrate coating on the cell surface that includes glycolipids and cell-identity markers.

Transmembrane vs. Peripheral Proteins

Transmembrane proteins pass through the membrane; peripheral proteins attach to one membrane surface.

Membrane Protein Functions

Receptors, channels, carriers/pumps, enzymes, cell-identity markers, and cell-adhesion molecules.

Receptors and Second Messengers

Receptors bind chemical signals; second messengers are produced inside the cell after receptor activation.

Channels vs. Carriers

Channels form pores for ions/water; carriers bind substances and transfer them across the membrane.

Channel Gates

Ligand-regulated gates respond to chemicals; voltage-regulated gates respond to voltage; mechanical gates respond to stretch/pressure.

Microvilli, Cilia, and Flagella

Microvilli increase surface area; cilia move substances or sense conditions; the sperm tail is the only functional human flagellum.

Selective Permeability

A membrane allows some substances through while preventing others.

Passive vs. Active Transport

Passive transport requires no ATP; active transport requires energy and can move substances against their gradient.

Simple Diffusion

Movement of particles from high concentration to low concentration.

Filtration

Movement through a membrane caused by hydrostatic pressure.

Osmosis

Movement of water across a selectively permeable membrane toward the area with lower water concentration.

Aquaporins

Channel proteins specialized for transporting water.

Osmotic Pressure

The hydrostatic pressure required to stop osmosis.

Tonicity

The ability of a solution to affect cell volume and pressure.

Hypotonic vs. Hypertonic vs. Isotonic

Hypotonic cells swell; hypertonic cells shrink; isotonic solutions cause no change in cell volume.

Crenation vs. Lysis

Crenation is cell shrinking from water loss; lysis is cell bursting from excessive water entry.

Carrier-Mediated Transport

Uses membrane proteins to move substances; carriers are specific and can become saturated.

Uniport, Symport, Antiport

Uniport moves one solute; symport moves multiple solutes in the same direction; antiport moves them in opposite directions.

Facilitated Diffusion

Carrier-mediated movement down a concentration gradient without ATP.

Active Transport

Carrier-mediated movement against a concentration gradient using ATP.

Sodium-Potassium Pump

Uses ATP to keep K+ concentration higher inside cells and remove Na+ from cells.

Secondary Active Transport

Uses a concentration gradient to transport substances without directly using ATP.

SGLT

Cotransports sodium and glucose into the cell using the sodium gradient.

Vesicular Transport

Moves large particles, fluid droplets, or many molecules using membrane-bound vesicles.

Endocytosis vs. Exocytosis

Endocytosis brings material into the cell; exocytosis releases material from the cell.

Types of Endocytosis

Phagocytosis takes in large particles; pinocytosis takes in fluid; receptor-mediated endocytosis uses specific receptors.

Cytoskeleton

Provides cell shape and support, organizes cell contents, directs movement, and helps move substances.

Cytoskeletal Elements

Microfilaments provide support and are involved in movement; intermediate fibers provide strength; microtubules help with movement.

Organelles

Internal cell structures that perform specialized metabolic tasks.

Membranous vs. Nonmembranous Organelles

Membranous: nucleus, mitochondria, lysosomes, peroxisomes, ER, Golgi. Nonmembranous: ribosomes, centrosomes, centrioles, basal bodies.

Nucleus

Largest organelle; contains genetic material and regulates cellular activities.

Nuclear Envelope, Pores, and Lamina

The nuclear envelope surrounds the nucleus; pores regulate molecular traffic; the lamina supports the envelope and organizes chromatin.

Chromatin and Nucleoli

Chromatin is DNA and protein; nucleoli are regions where ribosomes are produced.

Rough vs. Smooth ER

Rough ER has ribosomes and synthesizes proteins; smooth ER makes lipids/steroids and detoxifies substances.

Ribosomes

Read mRNA and assemble amino acids into proteins.

Golgi Complex

Modifies, sorts, and packages proteins and glycoproteins.

Lysosomes and Autophagy

Lysosomes digest cellular materials; autophagy uses lysosomes to dispose of worn-out organelles.

Autolysis

Destruction of a cell after it completes its intended function.

Peroxisomes and Catalase

Peroxisomes oxidize molecules and detoxify substances; catalase breaks down hydrogen peroxide into water and oxygen.

Mitochondria

Organelles that synthesize ATP and are often called the powerhouses of the cell.

Mitochondrial Structure

Cristae are folds of the inner membrane; the matrix contains enzymes, ribosomes, and mitochondrial DNA.

Centrioles and Centrosomes

Centrioles are microtubule cylinders; the centrosome contains two perpendicular centrioles and helps with cell division and cilia/flagella formation.