AP Biology Unit 2

Cytosol

the aqueous component of the cytoplasm in which organelles, proteins, and other cell structures are suspended.

eukaryotic cell

A type of cell characterized by a membrane-bound nucleus and organelles, including plants and animals.

prokaryotic cell

A type of cell that lacks a membrane-bound nucleus and organelles, typically found in bacteria and archaea.

Nucleoid

The irregularly shaped region within a prokaryotic cell where the genetic material, or DNA, is located.

Cytoplasm

The gel-like substance within a cell that contains organelles, where many metabolic processes occur. It is found between the cell membrane and the nucleus in eukaryotic cells.

plasma membrane

The semi-permeable barrier that surrounds the cell, regulating the movement of substances in and out.

Nucleus

The membrane-bound organelle in eukaryotic cells that contains the cell's genetic material, organizing DNA into chromosomes and coordinating cell activities.

Chromosomes

Threadlike structures made of DNA and proteins that carry genetic information.

Chromatin

Loosely packed DNA and protein found in the nucleus; condenses into chromosomes during cell division.

Nucleolus

Dense region in the nucleus where ribosomal RNA (rRNA) is synthesized.

Ribosomes

Molecular machines that synthesize proteins; found free in cytoplasm or bound to rough ER.

Endoplasmic Reticulum

Network of membranes involved in protein and lipid synthesis.

Smooth ER

ER without ribosomes; synthesizes lipids and detoxifies drugs.

Rough ER

ER with ribosomes; synthesizes and modifies proteins for secretion or membrane use.

Glycoproteins

Proteins with carbohydrate chains attached; important for cell recognition and signaling.

Golgi Apparatus

Modifies, sorts, and packages proteins and lipids for transport.

Lysosome

Organelle containing digestive enzymes to break down waste and cellular debris.

Phagocytosis

Type of endocytosis where a cell engulfs large particles or cells.

Mitochondria

Powerhouse of the cell; site of cellular respiration and ATP production.

Chloroplasts

Organelle in plant cells where photosynthesis occurs.

Cristae

Folds of the inner mitochondrial membrane; increase surface area for ATP production.

Mitochondrial Matrix

Innermost compartment of mitochondria; contains enzymes for Krebs cycle.

Cell Wall

Rigid outer layer in plant cells, fungi, and some bacteria; provides structure and protection.

Selective Permeability

Property of membranes that allows some substances to pass while blocking others.

Amphipathic

Molecule with both hydrophilic and hydrophobic regions (e.g., phospholipids).

Fluid Mosaic Model

Describes the cell membrane as a dynamic structure with proteins floating in a lipid bilayer.

Integral Proteins

Proteins embedded in the membrane; often span the bilayer and assist in transport.

Peripheral Proteins

Proteins attached to the surface of the membrane; involved in signaling and support.

Aquaporins

Channel proteins that facilitate water transport across membranes.

Diffusion

Movement of molecules from high to low concentration without energy input.

Concentration Gradient

Difference in concentration of a substance across a space or membrane.

Passive Transport

Movement of substances across membranes without energy (includes diffusion and osmosis).

Osmosis

Diffusion of water across a selectively permeable membrane.

Isotonic

Solution with equal solute concentration as the cell; no net water movement.

Hypertonic

Solution with higher solute concentration than the cell; water moves out, cell shrinks.

Hypotonic

Solution with lower solute concentration than the cell; water moves in, cell swells.

Turgid

Swollen and firm cell due to water uptake in a hypotonic solution (ideal for plant cells).

Flaccid

Limp cell due to water loss or lack of water uptake.

Plasmolysis

Shrinking of the cytoplasm away from the cell wall due to water loss in hypertonic solution.

Facilitated Diffusion

Passive transport of molecules via transport proteins.

Active Transport

Movement of substances against concentration gradient using energy (ATP).

Sodium-Potassium Pump

Active transport protein that moves Na⁺ out and K⁺ into the cell.

Cotransport

Coupled transport of two substances via a single protein; one moves down gradient, the other up.

Exocytosis

Process of vesicles fusing with the membrane to release contents outside the cell.

Phagocytosis

Cell engulfs large particles or cells (repeated for emphasis).

Pinocytosis

Cell engulfs extracellular fluid and dissolved solutes.

Receptor-Mediated Endocytosis

Specific uptake of molecules via receptors on the cell surface.

Ligands

Molecules that bind to receptors to initiate a cellular response.