AP Biology Unit 2 Study Guide: Cell Structure and Function

Nucleus

Contains DNA and controls cell activities through gene expression.

Ribosomes

Sites of protein synthesis, either free in cytosol or bound to rough ER.

Endoplasmic Reticulum (Rough ER)

Has ribosomes and synthesizes and folds proteins.

Endoplasmic Reticulum (Smooth ER)

Synthesizes lipids, detoxifies chemicals, and stores calcium.

Golgi Apparatus

Modifies, sorts, and packages proteins and lipids for secretion or internal use.

Lysosomes

Contain digestive enzymes to break down waste and macromolecules.

Mitochondria

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

Chloroplasts

Site of photosynthesis in plant cells.

Vacuoles

Storage organelles; large central vacuole in plant cells for water and nutrient storage.

Cytoskeleton

Network of fibers providing structure, transport, and support.

Surface Area-to-Volume Ratio

As a cell grows, this ratio decreases, reducing efficiency in exchanging materials.

Microvilli

Increase surface area for nutrient absorption in intestinal cells.

Root Hairs

Maximize water and nutrient uptake in plants.

Gills

Increase gas exchange surface area in aquatic animals.

Alveoli

Increase gas exchange surface area in mammals.

Phospholipids

Form a bilayer providing a semi-permeable barrier in cell membranes.

Membrane Proteins

Act as transport channels, receptors, and enzymes embedded in the membrane.

Cholesterol

Maintains membrane fluidity at different temperatures.

Membrane Carbohydrates

Attached to proteins and lipids for cell recognition and signaling.

Fluid Mosaic Model

Describes the dynamic and flexible structure of cell membranes with proteins and lipids.

Selective Permeability

Phospholipid bilayer allows small, nonpolar molecules to diffuse and blocks larger or polar molecules.

Cell Wall

Provides support, protection, and regulates water balance in plant cells.

Osmoregulation

Control of water balance in organisms.

Active Transport

Uses ATP to move substances against their concentration gradient.

Exocytosis

Vesicles fuse with the membrane to release large molecules out of the cell.

Endocytosis

Membrane engulfs large molecules to bring them into the cell.

Phagocytosis

Engulfing large particles.

Pinocytosis

Engulfing liquids.

Facilitated Diffusion

Polar or large molecules require protein channels to cross the membrane.

Diffusion

Molecules move from high to low concentration.

Osmosis

Water moves across membranes toward higher solute concentration.

Water Potential

Water moves from high to low water potential; calculated as Ψ = Ψs + Ψp.

Channel Proteins

Allow ions like Na⁺ and K⁺ to pass through the membrane.

Carrier Proteins

Undergo shape change to transport molecules like glucose.

Compartmentalization

Organelles are surrounded by membranes isolating them for specific functions.

Endosymbiotic Theory

Mitochondria and chloroplasts originated from free-living bacteria that were engulfed by a larger cell.