Chapter 2

Hydrophilic

"Water-loving"; attracted to water because it is polar or charged.

Hydrophobic

"Water-fearing"; repels water because it is nonpolar.

Phospholipid

A molecule with a hydrophilic phosphate head and two hydrophobic fatty acid tails that forms the plasma membrane.

Hydrophilic head

The phosphate-containing, polar part of a phospholipid that faces water.

Hydrophobic tails

The two nonpolar fatty acid chains of a phospholipid that face inward away from water.

Plasma membrane

A selectively permeable phospholipid bilayer that surrounds the cell and controls what enters and leaves.

Hydrophilic phosphate heads (plasma membrane)

Face the extracellular fluid and the intracellular fluid.

Hydrophobic fatty acid tails (plasma membrane)

Face each other in the center of the membrane, forming a barrier to water-soluble substances.

Intracellular space

The inside of the cell (cytoplasm).

Extracellular space

The fluid and environment outside the cell.

Cytoplasmic filaments

Protein fibers attached to the inside of the plasma membrane that provide support, maintain cell shape, and aid movement.

Diffusion

The movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.

Osmosis

The diffusion of water across a selectively permeable membrane from an area of lower solute concentration to higher solute concentration.

Diffusion vs. osmosis

Diffusion is the movement of any molecules; osmosis is specifically the movement of water across a selectively permeable membrane.

Eukaryotic cell

A cell with a nucleus and membrane-bound organelles.

Nucleus

Stores DNA and controls cell activities.

Nucleolus

Produces ribosomes.

Ribosomes

Synthesize proteins.

Rough endoplasmic reticulum (RER)

Modifies and transports proteins; covered with ribosomes.

Smooth endoplasmic reticulum (SER)

Synthesizes lipids, detoxifies chemicals, and stores calcium.

Golgi apparatus

Modifies, sorts, packages, and ships proteins and lipids.

Mitochondria

Produce ATP (energy) through cellular respiration; the "powerhouse" of the cell.

Lysosomes

Contain digestive enzymes that break down wastes, pathogens, and worn-out organelles.

Peroxisomes

Break down fatty acids and detoxify harmful substances using enzymes.

Centrosome

Organizes microtubules and forms the mitotic spindle during cell division.

Centrioles

Help organize spindle fibers during mitosis in animal cells.

Cytoplasm

Jelly-like material that contains organelles and is the site of many metabolic reactions.

Plasma membrane

Encloses the cell and regulates movement of substances into and out of the cell.

Cytoskeleton

A network of protein filaments that provides support, shape, movement, and intracellular transport.

Cell cycle

The series of events in which a cell grows, replicates its DNA, and divides.

Interphase

The longest phase of the cell cycle consisting of G1, S, and G2 phases.

G1 phase

The cell grows, performs normal functions, and synthesizes proteins and organelles.

S phase

DNA is replicated so each chromosome is copied before cell division.

G2 phase

The cell continues growing, checks for DNA errors, and prepares for mitosis.

Mitosis

The division of the nucleus into two genetically identical nuclei.

Cytokinesis

The division of the cytoplasm to form two identical daughter cells.

Prophase

Chromosomes condense, the nuclear envelope breaks down, centrosomes move to opposite poles, and spindle fibers form.

Metaphase

Chromosomes line up along the middle (metaphase plate) of the cell.

Anaphase

Sister chromatids separate and are pulled to opposite poles of the cell.

Telophase

Chromosomes reach opposite poles, nuclear envelopes reform, chromosomes uncoil, and spindle fibers disappear.

Cytokinesis (mitosis)

The cytoplasm divides, producing two genetically identical daughter cells.

Order of the cell cycle

G1 → S → G2 → Mitosis (Prophase → Metaphase → Anaphase → Telophase) → Cytokinesis.

Cancer

Cancer occurs when mutations cause cells to lose control of the cell cycle, resulting in uncontrolled mitosis and the formation of abnormal masses of cells called tumors.

How cancer occurs

Mutations damage genes that regulate the cell cycle. As a result, a cell continues through mitosis without proper control, causing uncontrolled cell division and tumor formation.

Purpose of mitosis

To produce two genetically identical daughter cells for growth, repair, and replacement of old or damaged cells.

Purpose of cytokinesis

To separate one parent cell into two individual daughter cells after mitosis.

Why is the S phase important?

The S phase ensures DNA is accurately copied so each daughter cell receives a complete set of chromosomes.

Why is the plasma membrane selectively permeable?

It allows certain substances to pass while blocking others, helping maintain homeostasis.