Fljr/srhs Biology Vocabulary Chapter 7

Front 1

active transport

Back 1

The movement of a substance across a biological membrane against its concentration or electrochemical gradient, with the help of energy input and specific transport proteins.

Front 2

cell

Back 2

A basic unit of living matter separated from its environment by a plasma membrane; the fundamental structural unit of life.

Front 3

cell membrane

Back 3

The outer membrane of the cell; the plasma membrane.

Front 4

cell theory

Back 4

All living things are composed of cells; cells arise only from other cells. No exception has been found to these two principles since they were first proposed well over a century ago.

Front 5

cell wall

Back 5

A protective layer external to the plasma membrane in plant cells, bacteria, fungi, and some protists. In the case of plant cells, the wall is formed of cellulose fibers embedded in a polysaccharide-protein matrix. The primary cell wall is thin and flexible, whereas the secondary cell wall is stronger and more rigid, and is the primary constituent of wood.

Front 6

chloroplast

Back 6

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

Front 7

chromatin

Back 7

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

Front 8

chromosome

Back 8

A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins. See chromatin.

Front 9

cytoplasm

Back 9

The entire contents of the cell, exclusive of the nucleus, and bounded by the plasma membrane.

Front 10

cytoskeleton

Back 10

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

Front 11

diffusion

Back 11

The spontaneous tendency of a substance to move down its concentration gradient from a more concentrated to a less concentrated area.

Front 12

endocytosis

Back 12

The cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch off to form an intracellular vesicle.

Front 13

eukaryote

Back 13

An organism whose cells contain membraine-bound organelles and whose DNA is enclosed in a cell nucleus and is associated with proteins.

Front 14

exocytosis

Back 14

The cellular secretion of macromolecules by the fusion of vesicles with the plasma membrane.

Front 15

facilitated diffusion

Back 15

The spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients.

Front 16

Golgi apparatus

Back 16

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

Front 17

lysosome

Back 17

A membrane-enclosed bag of hydrolytic enzymes found in the cytoplasm of eukaryotic cells.

Front 18

microfilament

Back 18

A solid rod of actin protein in the cytoplasm of almost all eukaryotic cells, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction.

Front 19

microtubule

Back 19

A hollow rod of tubulin protein in the cytoplasm of all eukaryotic cells and in cilia, flagella, and the cytoskeleton.

Front 20

mitochondrion pl. mitochondria

Back 20

An organelle in eukaryotic cells that serves as the site of cellular respiration.

Front 21

nuclear envelope

Back 21

The membrane in eukaryotes that encloses the nucleus, separating it from the cytoplasm.

Front 22

nucleolus

Back 22

A specialized structure in the nucleus, formed from various chromosomes and active in the synthesis of ribosomes.

Front 23

organ

Back 23

A specialized center of body function composed of several different types of tissues.

Front 24

organelle

Back 24

One of several formed bodies with a specialized function, suspended in the cytoplasm and found in eukaryotic cells.

Front 25

osmosis

Back 25

The diffusion of water across a selectively permeable membrane.

Front 26

phagocytosis

Back 26

A type of endocytosis involving large, particulate substances.

Front 27

ribosome

Back 27

A cell organelle constructed in the nucleolus, functioning as the site of protein synthesis in the cytoplasm. Consists of rRNA and protein molecules, which make up two subunits.

Front 28

selective permeability

Back 28

A property of biological membranes that allows some substances to cross more easily than others.

Front 29

tissue

Back 29

An integrated group of cells with a common structure and function.

Front 30

vacuole

Back 30

A membrane-enclosed sac taking up most of the interior of a mature plant cell and containing a variety of substances important in plant reproduction, growth, and development.