Cell Biology Essentials

Nucleus

Mitochondrion

Golgi apparatus

Cell membrane

That is why they are called the powerhouse of the cell.

They read the mRNA three bases (one codon) at a time.

Eukaryotic cells have a membrane-bound nucleus and organelles; prokaryotic cells do not.

Chloroplast

Lysosome

Cell membrane

All living things are made of one or more cells The cell is the basic unit of life All cells come from pre-existing cells

Dense region inside the nucleus where ribosomal RNA is made and ribosome subunits are assembled.

Membrane network studded with ribosomes that makes and folds proteins destined for secretion or membranes.

ER without ribosomes that makes lipids and steroids, detoxifies drugs and stores calcium.

Proteins travel rough ER → Golgi → vesicles → cell membrane or lysosomes.

Small organelle that breaks down fatty acids and toxins, producing hydrogen peroxide that its enzyme catalase then breaks down.

Network of microfilaments (actin), intermediate filaments and microtubules that gives the cell its shape, anchors organelles and moves things around.

Microtubule-organizing center of animal cells; organizes the spindle fibers during cell division.

Large water-filled sac in plant cells that stores water and ions and keeps the cell firm (turgor pressure).

Rigid layer outside the cell membrane: cellulose in plants, chitin in fungi, peptidoglycan in bacteria. Gives support and shape.

Cell wall, chloroplasts and a large central vacuole.

Centrioles and lysosomes (plants mostly use their central vacuole instead).

Like bacteria, they have their own circular DNA, 70S ribosomes and a double membrane, and they divide by a process like binary fission.

Prokaryotes: 70S. Eukaryotes: 80S in the cytoplasm.

Cholesterol in animal membranes keeps fluidity steady as temperature changes.

The phosphate heads are hydrophilic and face the water; the fatty acid tails are hydrophobic and hide in the middle.

Small nonpolar molecules such as O₂ and CO₂. Ions and large polar molecules (like glucose) need transport proteins.

Net movement of particles from an area of high concentration to low concentration, with no energy input.

Diffusion of water across a selectively permeable membrane toward the side with more dissolved solute.

Passive movement down a concentration gradient through channel or carrier proteins (glucose transporters, aquaporins).

Moving substances against their concentration gradient using energy (ATP), e.g. the sodium–potassium pump.

Hypertonic: water leaves and the cell shrivels (crenates). Hypotonic: water enters and the cell swells and may burst (lyses). Isotonic: no net change.

Hypotonic: it becomes turgid (firm); the cell wall stops it from bursting. Hypertonic: the membrane pulls away from the wall (plasmolysis).

Endocytosis: the membrane engulfs material to bring it in (phagocytosis, pinocytosis). Exocytosis: a vesicle fuses with the membrane to release its contents.

As a cell grows, its volume increases faster than its surface area, so the membrane cannot move materials in and out fast enough.

Interphase: G1 (growth), S (DNA replication), G2 (preparation). M phase: mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis.