AP Bio Ch. 6 Vocab

Cell Wall

A protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists. Polysaccharides such as cellulose (in plants and some protists), chitin (in fungi), and peptidoglycan (in bacteria) are important structural components of cell walls.

Centriole

A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a “9 + 0” pattern. A centrosome has a pair of centrioles.

Centrosome

A structure present in the cytoplasm of animal cells that functions as a microtubule

Chloroplast

An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes. When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.

Chromosome

A cellular structure consisting of one DNA molecule and associated protein molecules. A duplicated chromosome has two DNA molecules. (In some contexts, such as genome sequencing, the term may refer to the DNA alone.) A eukaryotic cell typically has multiple, linear chromosomes, which are located in the nucleus. A prokaryotic cell often has a single, circular chromosome, which is found in the nucleoid, a region that is not enclosed by a membrane. See also chromatin.

Cytoplasm

The contents of the cell bounded by the plasma membrane; in eukaryotes, the portion exclusive of the nucleus.

Cytoskeleton

A network of microtubules, microfilaments, and intermediate filaments that extend throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions.

Cytosol

The semifluid portion of the cytoplasm.

Electron Microscope

A microscope that uses magnets to focus an electron beam on or through a specimen, resulting in a practical resolution that is 100

Endomembrane System

The collection of membranes inside and surrounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles; includes the plasma membrane, the nuclear envelope, the smooth and rough endoplasmic reticulum, the Golgi apparatus, lysosomes, vesicles, and vacuoles.

Endosymbiont Theory

The theory that mitochondria and plastids originated as prokaryotic cells engulfed by a host cell. The engulfed cell and its host cell then evolved into a single organism. See also endosymbiosis.

Extracellular Matrix

The meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides, and proteoglycans synthesized and secreted by cells.

Glycoprotein

A protein with one or more covalently attached carbohydrates.

Golgi Apparatus

An organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates.

Light Microscope

An optical instrument with lenses that refract (bend) visible light to magnify images of specimens.

Lysosome

A membrane-enclosed sac of hydrolytic enzymes found in the cytoplasm of animal cells and some protists.

Microfilament

A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction; also called an actin filament.

Mitochondrion

An organelle in eukaryotic cells that serves as the site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP.

Nuclear Envelope

In a eukaryotic cell, the double membrane that surrounds the nucleus, perforated with pores that regulate traffic with the cytoplasm. The outer membrane is continuous with the endoplasmic reticulum.

Nucleolus

A specialized structure in the nucleus, consisting of chromosomal regions containing ribosomal RNA (rRNA) genes along with ribosomal proteins imported from the cytoplasm; site of rRNA synthesis and ribosomal subunit assembly. Seealso ribosome.

Nucleus

(1) An atom's central core, containing protons and neutrons. (2) The organelle of a eukaryotic cell that contains the genetic material in the form of chromosomes, made up of chromatin. (3) A cluster of neurons.

Peroxisome

An organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen (O2), producing and then degrading hydrogen peroxide (H2O2).

Phagocytosis

A type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells).

Plasma Membrane

The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition.

Plastid

One of a family of closely related organelles that includes chloroplasts, chromoplasts, and amyloplasts.

Ribosome

A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large and a small subunit. In eukaryotic cells, each subunit is assembled in the nucleolus. See also nucleolus.

Rough endoplasmic reticulum

That portion of the endoplasmic reticulum with ribosomes attached

Smooth endoplasmic reticulum

That portion of the endoplasmic reticulum that is free of ribosomes.

Vacuole

A membrane-bounded vesicle whose specialized function varies in different kinds of cells.

Vesicle

A membrane-bound sac in or outside a cell.