chapter 4 - the cell 🧫

What are the main structural features of a cell?

Plasma membrane, nucleus, and cytoplasm.

What is the plasma membrane?

A selectively permeable barrier that controls entry/exit of substances and provides structure to the cell.

Four consecutive phases that take place during mitosis are..

Prophase, metaphase, anaphase, telophase

What is the nucleus?

The control center of the cell; contains DNA and directs protein synthesis.

What is cytoplasm?

The material between the plasma membrane and the nucleus; includes cytosol, organelles, and inclusions.

What is cytosol?

The fluid portion of cytoplasm; contains dissolved ions, nutrients, and proteins.

How do cytoplasm and cytosol differ?

Cytoplasm includes organelles; cytosol is just the fluid part.

What are the general functions of cells?

Maintain integrity, obtain nutrients, eliminate waste, perform metabolism, and reproduce.

What are common cell shapes?

Spherical, cube-like, columnar, disc-shaped, and irregular.

What are the lipid components of the plasma membrane?

Phospholipids, cholesterol, and glycolipids.

What are integral and peripheral membrane proteins?

Integral: embedded in the membrane; Peripheral: attached to the inner/outer surface.

What are major roles of membrane proteins?

Transport, communication, anchoring, recognition, and enzymatic activity.

What are passive transport processes?

Diffusion and osmosis—no energy required.

What are active transport processes?

Require ATP; examples include pumps and vesicular transport.

What is diffusion?

Movement of molecules from high to low concentration.

What is osmosis?

Diffusion of water through a selectively permeable membrane.

What factors influence diffusion rate?

Molecule size, temperature, and concentration gradient steepness.

What is tonicity?

The ability of a solution to change a cell’s volume by osmosis.

Define isotonic.

Equal solute concentration inside and outside the cell; no net water movement.

Define hypotonic.

Lower solute concentration outside; water enters the cell → cell swells.

Define hypertonic.

Higher solute concentration outside; water leaves the cell → cell shrinks.

What is resting membrane potential (RMP)?

Electrical potential difference across the plasma membrane at rest.

What maintains RMP?

Sodium-potassium pumps and differential ion permeability.

Why is RMP important?

It enables muscle and nerve cell excitability.

How do cells communicate?

Through direct contact (cell junctions) or ligand-receptor signaling.

What are the main organelles and their functions?

Mitochondria: ATP; Ribosomes: protein synthesis; ER: transport; Golgi: packaging; Lysosomes: digestion; Cytoskeleton: structure.

What are external cellular features?

Cilia (movement), flagella (propulsion), microvilli (increase surface area).

What are membrane junctions?

Connections between cells: tight junctions, desmosomes, gap junctions.

Tight junctions: function?

Seal cells together to prevent leakage.

Desmosomes: function?

Provide strong adhesion between cells.

Gap junctions: function?

Allow direct communication and passage of small molecules.

Describe the nucleus, DNA, chromatin, and chromosomes.

Nucleus houses DNA; DNA organized as chromatin (loose) or chromosomes (condensed).

What are the steps of transcription?

Initiation, elongation, termination; produces mRNA.

What happens during mRNA modification?

Capping, poly-A tail addition, intron removal.

What are the steps of translation?

Initiation, elongation, termination; produces a polypeptide chain.

What are the phases of the cell cycle?

Interphase (G₁, S, G₂) and mitotic phase (mitosis + cytokinesis).

What are the stages of mitosis?

Prophase, metaphase, anaphase, telophase.

What is a somatic cell?

Any body cell other than a gamete.

What is apoptosis?

Programmed cell death.