Cell Structure and Function: Key Organelles and Processes

Nucleus

Brain of the cell; holds DNA and controls all activities.

Ribosome

Tiny factory that makes proteins.

Rough ER

Folds and modifies proteins made by ribosomes.

Smooth ER

Makes lipids (fats) and detoxifies harmful stuff.

Golgi Apparatus

Post office; packages, sorts, and ships proteins.

Lysosome

Breaks down old or damaged parts; the trash can of the cell.

Mitochondria

Powerhouse of the cell; makes ATP (energy).

Chloroplast

Found in plants; turns sunlight into sugar (photosynthesis).

Vacuole

Storage for water and food; helps plant cells stay firm.

Cytoskeleton

Cell's "bones"; gives shape and helps move things inside.

Plasma Membrane

The bouncer; controls what enters and leaves the cell.

Phospholipid Bilayer

Two-layer fat barrier with water-loving heads and water-hating tails.

Fluid Mosaic Model

Membrane is flexible and full of moving proteins — not stiff.

Simple Diffusion

Movement of small molecules (O₂, CO₂) through the membrane without energy.

Facilitated Diffusion

Movement through a protein channel — no energy needed.

Osmosis

Water moving toward the saltier side through a membrane.

Active Transport

Moves materials against concentration gradient using ATP.

Sodium

Potassium Pump - Uses energy to pump 3 Na⁺ out and 2 K⁺ in.

Endocytosis

Cell takes material in by wrapping around it.

Exocytosis

Cell pushes material out.

Hypotonic Solution

More water outside; cell swells.

Hypertonic Solution

Less water outside; cell shrinks.

Isotonic Solution

Equal water in and out; cell stays the same.

Surface Area to Volume Ratio

Small cells are more efficient for material exchange.

Prokaryotic Cell

Simple cell with no nucleus (like bacteria).

Eukaryotic Cell

Complex cell with nucleus and organelles (plants, animals, fungi).

Endosymbiotic Theory

Mitochondria and chloroplasts were once free-living bacteria.

Compartmentalization

Different organelles do different jobs to stay organized.

Cytoplasm

Jelly-like fluid that holds everything in place.

Cell Wall

Found in plants and bacteria; gives structure and protection.