Chapter 4: Cell Structure & Function

A comprehensive vocabulary review of Chapter 4: Cell Structure & Function, including cell theory, bacterial features, organelles, endomembrane system, and cytoskeleton components.

Cell Theory

The foundational biological principle stating that all living organisms are composed of one or more cells, cells are the fundamental structural and functional units of life, and all cells arise only from preexisting cells.

Surface-Area-to-Volume Ratio

A ratio that limits maximum cell size because as a cell grows, its volume increases much faster than its surface area, requiring a high ratio for efficient material exchange of nutrients and wastes across the membrane.

Cell Envelope

The outer structure of a bacterial cell comprising the plasma membrane, cell wall, and an optional glycocalyx or capsule.

Cytoplasm (Bacterial)

The semifluid interior of a bacterial cell holding water, enzymes, a nucleoid with circular DNA, and ribosomes. It is also the goop within the cell.

Flagella

Bacterial cell appendages responsible for motility.

Fimbriae

Bacterial cell appendages responsible for adherence.

Conjugation Pili

Bacterial cell appendages responsible for DNA transfer.

Coccus

A spherical or round bacterial cell shape.

Bacillus

A rod-shaped bacterial cell shape.

Spirillum / Spirochete

A spiral or curved bacterial cell shape.

Endosymbiotic Theory

Theory proposing that eukaryotic cells evolved when a prokaryotic host engulfed aerobic or photosynthetic bacteria; supported by evidence that mitochondria and chloroplasts have double membranes, circular DNA, and prokaryotic-sized (70S) ribosomes.

Nucleus

Eukaryotic organelle enclosed by a double-membrane nuclear envelope with nuclear pores that stores DNA and the genetic blueprint, containing chromatin and the nucleolus.

Nucleolus

A nuclear structure that serves as the site of ribosomal RNA synthesis and ribosome assembly. It is the dark spot of the nucleus

Ribosomes

Cellular structures that carry out protein synthesis by translating mRNA sequences; found free in the cytoplasm or bound to the rough ER in eukaryotes. Nickname: the protein-making factory.

Rough ER

Endoplasmic reticulum studded with ribosomes that folds and modifies proteins.

Smooth ER

Endoplasmic reticulum lacking ribosomes that functions in lipid synthesis and detoxification.

Golgi Apparatus

An organelle that modifies, sorts, and packages molecules into vesicles. It is also looks like a stack of pancakes in the cell

Lysosomes

Membrane-bound organelles containing acidic hydrolytic enzymes for intracellular digestion and recycling.

Vacuoles

Organelles that function in the storage of water, nutrients, and waste, such as the plant central vacuole for turgor pressure.

Chloroplasts

Plant cell organelles that perform photosynthesis, converting solar energy into glucose.

Mitochondria

Organelles that perform cellular respiration, breaking down glucose to produce ATP.

Cytoskeleton

A network of protein structures responsible for cell shape, support, and internal transport.

Endomembrane System

A system of interrelated organelles including the nuclear envelope, rough/smooth ER, Golgi, vesicles, and plasma membrane that produces and transports molecules.

Endocytosis

Vesicular transport moving materials into the cell.

Exocytosis

Vesicular transport releasing materials out of the cell.

Transport Vesicles

Membrane-bound sacs that move molecules between internal organelles.

Secretory Vesicles

Vesicles that fuse with the plasma membrane to release contents outside the cell.

Incoming Vesicles

Vesicles formed by endocytosis to bring external material into the cell.

Actin Filaments

Thin, flexible helical chains of actin protein that support cell shape, muscle contraction, and movement.

Microtubules

Hollow tubes made of tubulin dimers that maintain cell shape, act as tracks for vesicle motor proteins, and form the spindle apparatus during cell division.

MTOC

Microtubule-Organizing Center.

Centrosome

The main MTOC (microtubule-organizing center) in animal cells is located near the nucleus, containing two centrioles oriented at right angles.

Centrioles

Structures inside the centrosome oriented at right angles to each other, each composed of microtubule triplets.

Universal Cell Components

All Cells have: DNA (genetic material), cell Membrane (phospholipid bilayer barrier),

Cytoplasm/Cytosol (semifluid interior), and Ribosomes (protein synthesis machinery).