1. All living things are made of cells.
2. Cells are the basic unit of structure and function in organisms.
3. All cells come from pre-existing cells.

Because it is supported by extensive evidence and experiments, not just a single idea.

They cannot reproduce or carry out metabolism independently; they require a host cell.

Cell membrane: protective barrier controlling entry/exit.
Cytoplasm: fluid where organelles float.
Organelles: specialized structures performing functions inside the cell.

Geometrically: Surface area-to-volume ratio limits diffusion.
Physiologically: Small size allows efficient transport of nutrients/wastes.

1. Nucleus: absent in prokaryotes, present in eukaryotes.
2. DNA shape: circular in prokaryotes, linear in eukaryotes.
3. Organelles: none in prokaryotes, many in eukaryotes.
4. Transcription & translation: occur simultaneously in prokaryotes, separated in eukaryotes.

Nuclear envelope: outer boundary of nucleus.
Nucleolus: dense region inside nucleus.
Nuclear pore: openings in envelope for transport.
Chromatin: DNA + proteins inside nucleus.

Synthesizes rRNA and assembles ribosomal subunits.

Scattered throughout the nucleus when not condensed.

A DNA segment coding for a specific protein or trait.

DNA → gene → mRNA → nuclear pore → Rough ER → ribosome → protein → transport vesicle → cis-face Golgi → trans-face Golgi → lysosome.

Synthesizes proteins for secretion or membrane insertion.

Synthesizes lipids, detoxifies chemicals, stores calcium.

Liver (detoxification) or steroid-producing cells.

Modifies, sorts, packages proteins and lipids for transport.

Cis-face: receives vesicles; Trans-face: ships vesicles out.

Small, spherical vesicle containing digestive enzymes.

Digestion, recycling cell materials, apoptosis.

Lysosome (breaks down tissue between digits during development).

Formed from the endoplasmic reticulum and Golgi apparatus vesicles.

Plant: stores water, nutrients, pigments, waste; maintains turgor.
Animal: stores nutrients, waste, helps in endocytosis/exocytosis.

Plastids (chromoplasts).

Double membrane; inner for ATP production, outer protective.

They can produce some proteins/enzymes independently of the nucleus.

ATP production, metabolism, apoptosis signaling.

Microtubules, microfilaments, and intermediate filaments.

Cell shape, intracellular transport, and cell movement/division.

Double membrane; inner membrane encloses stroma and thylakoids for photosynthesis.

Stroma: fluid inside inner membrane.
Grana: stacked thylakoids.
Thylakoid: membrane disks containing chlorophyll.
Inner membrane: surrounds stroma.
Outer membrane: outer boundary.

Thylakoid membranes.

Site of photosynthesis (converts light energy to chemical energy).

1. Cell wall (plant) vs none (animal).
2. Chloroplasts in plants.
3. Large central vacuole in plants.
4. Shape: plant cells rigid/rectangular, animal cells round/flexible.