bio

Nucleus

Double-membrane organelle containing genetic material (DNA); site of transcription.

Nucleolus

Dense region within the nucleus; site of ribosomal RNA (rRNA) synthesis.

Mitochondria

Site of ATP production via aerobic respiration; replicates via binary fission; contains circular DNA.

Lysosomes

Membrane-bound structures containing hydrolytic enzymes that break down substrates.

Rough Endoplasmic Reticulum

Studded with ribosomes; permits translation of proteins destined for secretion.

Smooth Endoplasmic Reticulum

Used for lipid synthesis and detoxification of drugs/poisons.

Golgi Apparatus

Stacked membrane-bound sacs; modifies, sorts, and packages proteins into vesicles.

Peroxisomes

Contain hydrogen peroxide; break down long-chain fatty acids via \beta-oxidation.

Microfilaments

Made of actin; provide structural protection and cause muscle contraction (with myosin).

Microtubules

Hollow polymers of tubulin; create pathways for motor proteins (kinesin/dynein).

Cilia & Flagella

9+2 microtubule structure; used for movement of the cell or material along the surface.

Centrioles

Found in centrosomes; organize the mitotic spindle during cell division.

Epithelial Tissue

Covers the body and lines cavities; often constitutes the parenchyma (functional parts) of organs.

Connective Tissue

Supports the body and provides a framework; forms the stroma (supportive structure).

Prokaryotes

Single-celled organisms; no membrane-bound organelles; genetic material in a single circular molecule (nucleoid).

Archaea

Single-celled extremophiles; use alternative energy sources (chemosynthesis).

Gram-Positive Bacteria

Thick layer of peptidoglycan; contains lipoteichoic acid; stains purple.

Gram-Negative Bacteria

Thin peptidoglycan layer; outer membrane contains phospholipids and lipopolysaccharides; stains pink/red.

Binary Fission

Simple form of asexual reproduction seen in prokaryotes.

Prions

Infectious proteins that cause misfolding of other proteins (usually \alpha-helix to \beta-pleated sheet).