chapter 3 & 10 quiz

Cytoskeleton

The internal network of protein filaments that provides structural support and enables movement of substances within the cell; composed of microfilaments, intermediate filaments, and microtubules.

Microfilament

The thinnest cytoskeletal filament, made of actin monomers arranged in a double helix; located just beneath the plasma membrane and involved in shape, movement, cytokinesis, and vesicle transport.

Actin monomer

The protein subunit that polymerizes to form microfilaments.

Intermediate filament

A strong fibrous filament made of various proteins; cell-type specific (e.g., keratins, vimentin, neurofilaments, lamins) that provides mechanical strength.

Keratin

An intermediate filament protein found in epithelial cells.

Vimentin

An intermediate filament protein found in fibroblasts.

Neurofilament

An intermediate filament protein found in neurons.

Lamin

An intermediate filament protein located in the nucleus.

Microtubule

A hollow tube formed from tubulin dimers (alpha and beta) that radiates from the centrosome to help maintain cell shape and organelle organization and serve as tracks for movement.

Tubulin dimer

The building block of microtubules, consisting of one alpha-tubulin and one beta-tubulin subunit.

Centrosome

The microtubule organizing center from which microtubules emanate; helps maintain cell shape and organize organelles.

Dynamic instability

The rapid switching between growth (polymerization) and shrinkage (depolymerization) of microtubules.

Polymerization

The process of tubulin dimers adding to a microtubule to grow.

Depolymerization

The shortening of microtubules by loss of tubulin subunits.

Kinesin

A motor protein that moves cargo toward the plus (+) end of microtubules, usually away from the cell center.

Dynein

A motor protein that moves cargo toward the minus (−) end of microtubules, generally toward the cell center.

Cilia

Short, numerous microtubule-based projections that beat to move fluid across cell surfaces (e.g., airway epithelia).

Flagellum

A longer cilium used for locomotion, as in sperm cells.

Chlamydomonas

A green alga that moves using two long cilia.

Paramecium

A protist covered with short cilia that beat in a coordinated fashion to propel the organism.

Epidermolysis bullosa

A skin fragility disorder caused by mutations in intermediate filament proteins, leading to fragile epidermis and blisters.

Vesicle transport

Movement of vesicles along cytoskeletal tracks, powered by motor proteins like kinesin and dynein (e.g., Golgi to plasma membrane).

Cell Theory

All organisms are made up of cells; the cell is the fundamental unit of life; cells come from preexisting cells.

Prokaryote

Organism with no nucleus and no membrane bound organelles; DNA located in a nucleoid.

Eukaryote

Organism with a nucleus and membrane bound organelles; generally larger and more complex cells.

Nucleoid

Region in prokaryotic cells where DNA is located, not enclosed by a membrane.

Nucleus

Double-membrane bound organelle containing genetic material; site of RNA synthesis.

Nuclear envelope

Double membrane surrounding the nucleus; contains nuclear pores for selective transport.

Nuclear pores

Protein channels in the nuclear envelope allowing regulated exchange of materials between nucleus and cytoplasm.

Endomembrane system

Interconnected membranes including the ER, Golgi apparatus, lysosomes, and more, coordinating protein and lipid synthesis, modification, and transport.

Endoplasmic reticulum

Rough ER synthesizes proteins; Smooth ER synthesizes lipids.

Golgi apparatus

Modifies, sorts, and packages proteins and lipids for transport to final destinations.

Lysosome

Vesicles containing enzymes that digest macromolecules.

Mitochondria

Double-membrane organelles that generate most ATP for the cell.

Chloroplast

Plant organelle that captures light energy to fix carbon and synthesize sugars.

Plasma membrane

Phospholipid bilayer that defines the cell boundary and regulates material passage; selectively permeable.

Phospholipid

Amphipathic molecule with hydrophilic head and hydrophobic tails; builds membranes.

Hydrophilic

Water-loving polar head group of a phospholipid.

Hydrophobic

Water-fearing nonpolar tails of a phospholipid.

Micelle

Spherical arrangement of phospholipids in water with heads facing outward.

Bilayer

Phospholipid bilayer forming the core structure of cell membranes.

Liposome

Spherical vesicle formed from a phospholipid bilayer used to model or deliver molecules.

Fluid mosaic model

Membrane structure of a dynamic mix of lipids and proteins that move laterally within the layer.

Cholesterol

Sterol in animal membranes that modulates fluidity and packing of phospholipids.

Unsaturated fatty acids

Fatty acids with one or more double bonds causing kinks; reduce packing and increase membrane fluidity.

Saturated fatty acids

Fatty acids with no double bonds; straight chains that pack tightly and decrease fluidity.

Integral membrane proteins

Proteins that span the membrane, often functioning as channels or transporters.

Peripheral membrane proteins

Proteins associated with the membrane surface; not embedded in the bilayer.

Diffusion

Movement of solutes from high to low concentration; passive and energy-free.

Osmosis

Movement of water across a semipermeable membrane toward higher solute concentration.

Facilitated diffusion

Diffusion that requires a transport protein for ions or polar molecules.

Primary active transport

Energy-driven transport moving substances against their gradient, using ATP.

Na+/K+ pump

Sodium-potassium ATPase; pumps 3 Na+ out and 2 K+ in to establish gradients.

Secondary active transport

Uses the energy from an established ion gradient to move another substance; includes symport and antiport.

Exocytosis

Bulk transport where vesicles fuse with the plasma membrane and release contents outside the cell.

Endocytosis

Bulk transport where the cell membrane forms vesicles to bring in material.

Phagocytosis

Cellular eating; engulfing large particles via pseudopodia to form a food vacuole.

Pinocytosis

Cellular drinking; uptake of extracellular fluid and solutes via coated vesicles.

Receptor-mediated endocytosis

Selective endocytosis triggered by binding of specific solutes to cell-surface receptors.

Plasmodesmata

Cytoplasmic channels that connect adjacent plant cells.

Turgor pressure

Internal pressure in plant cells from water uptake, contributing to rigidity.

Cell wall

Rigid layer outside the plasma membrane in plants and some organisms that provides structure and protection.

Vacuole

Vesicle or organelle that stores water; central vacuole in plants contributes to turgor.

Cytoskeleton

Network of protein filaments providing structural support and shape to the cell.