AP Biology unit 2

Cells

The basic structural and functional unit of all living organisms.

Surface area-to-volume ratio

A measure that affects the efficiency of material exchange; larger ratios improve diffusion and transport.

Light microscopes

Microscopes that use visible light to observe small objects; can magnify up to ~1000x.

Electron microscopes

Microscopes that use beams of electrons for higher resolution imaging of cellular structures.

Prokaryotic cells

Simple cells without membrane-bound organelles; DNA is in the nucleoid.

Eukaryotic cells

Complex cells with membrane-bound organelles, including a nucleus.

Cytoplasm

Jelly-like fluid inside the cell that surrounds organelles.

Nucleoid

Region in prokaryotic cells where DNA is located (not membrane-bound).

Cell wall

Rigid structure outside the plasma membrane that provides support and protection (found in plants, fungi, bacteria).

Plasma membrane

Semi-permeable phospholipid bilayer that regulates entry/exit of materials.

Flagella

Long whip-like structures used for cell movement.

Capsule

Protective outer layer in some prokaryotes, helps prevent desiccation and aids attachment.

Organelles

Specialized membrane-bound structures within eukaryotic cells.

Phospholipid bilayer

The fundamental structure of cell membranes; hydrophilic heads and hydrophobic tails.

Peripheral proteins

Proteins attached loosely to the membrane surface.

Integral proteins

Proteins embedded within the lipid bilayer.

Transmembrane proteins

Integral proteins that span the entire membrane.

Fluid mosaic model

Describes the plasma membrane as flexible, with proteins and lipids moving within the bilayer.

Adhesion proteins

Membrane proteins that help cells stick to each other and to surfaces.

Receptor proteins

Proteins that bind signaling molecules and trigger cellular responses.

Transport proteins

Proteins that help move substances across the plasma membrane.

Cell surface markers

Molecules on the cell membrane used for cell recognition (often glycoproteins).

Carbohydrate side chains

Chains attached to proteins or lipids on the cell surface for recognition and signaling.

Nucleus

Organelle that houses genetic material (DNA) in eukaryotic cells.

Chromosomes

Condensed DNA molecules carrying genetic information.

Nucleolus

Dense region within the nucleus where ribosomes are assembled.

Ribosomes

Structures that synthesize proteins, found free in cytoplasm or attached to ER.

Endoplasmic reticulum (ER)

Network of membranes for protein and lipid synthesis.

Rough ER

Studded with ribosomes; site of protein synthesis and modification.

Smooth ER

Lacks ribosomes; synthesizes lipids, detoxifies toxins.

Golgi bodies

Flattened sacs that modify, sort, and package proteins/lipids for transport.

Vesicles

Small membrane sacs that transport materials within the cell.

Mitochondria

Organelles that perform cellular respiration to produce ATP.

Adenosine triphosphate (ATP)

The main energy currency of the cell.

Cristae

Folded inner membrane of mitochondria that increases surface area for ATP production.

Lysosomes

Organelles containing digestive enzymes that break down waste.

Centrioles

Structures involved in organizing microtubules during cell division.

Microtubule organizing centers (MTOCs)

Structures where microtubules are nucleated.

Vacuoles

Membrane-bound sacs used for storage of water, nutrients, or waste.

Peroxisomes

Organelles that break down fatty acids and detoxify harmful substances.

Cytoskeleton

Network of fibers that provide structure, support, and aid in movement.

Microtubules

Hollow protein tubes that give shape and aid intracellular transport.

Microfilaments

Thin protein filaments involved in movement and shape.

Tubulin

Protein subunit that makes up microtubules.

Cilia

Short hairlike projections used for movement or moving substances.

Euglena

A unicellular organism with both plantlike and animal-like traits.

Paramecium

A unicellular ciliate protozoan often used in labs.

Cell wall (plants/fungi/algae)

Made of cellulose (plants), chitin (fungi), provides structural support.

Chitin

Structural polysaccharide found in fungal cell walls and exoskeletons.

Chloroplasts

Organelles that carry out photosynthesis in plant cells.

Central vacuole

Large vacuole in plants for water and nutrient storage.

Cell sap

Fluid inside the central vacuole.

Facilitated transport

Passive movement of molecules across membranes using proteins.

Aquaporins

Channel proteins that facilitate rapid water transport.

Simple diffusion

Movement of molecules from high to low concentration without energy.

Facilitated diffusion

Diffusion using transport proteins, no energy required.

Passive transport

General movement across membranes without energy.

Osmosis

Diffusion of water across a selectively permeable membrane.

Tonicity

Relative concentration of solutes that affects water movement.

Isotonic

Equal solute concentrations; no net water movement.

Hypertonic

Higher solute concentration outside cell; cell loses water.

Hypotonic

Lower solute concentration outside cell; cell gains water.

Water potential

Measure of the potential energy of water in a system.

Solute (osmotic) potential

Part of water potential determined by solute concentration.

Solutes

Substances dissolved in a solution.

Active transport

Movement of molecules against concentration gradient using energy.

Sodium-potassium pump

Active transport protein that moves Na⁺ out and K⁺ in.

Endocytosis

Process of bringing large materials into the cell.

Pinocytosis

Cell drinking; uptake of fluids and small molecules.

Phagocytosis

Cell eating; engulfing large particles or cells.

Receptor-mediated endocytosis

Uptake of specific molecules bound to receptors.

Clathrin

Protein that helps form coated vesicles in endocytosis.

Bulk flow

Movement of large amounts of fluid or molecules in one direction.

Dialysis

Separation of molecules by diffusion across a selectively permeable membrane.

Exocytosis

Process of expelling materials from the cell via vesicle fusion with the plasma membrane.