Penn Foster Biology Chapter 4

Front 1

aerobic respiration

Back 1

Oxygen-dependent pathway of ATP formation in which glucose is broken down to carbon dioxide and water in several steps, including glycolysis, the Krebs cycle, and electron transfer phosphorylation. Typical net yield: 36 ATP.

Front 2

archaea

Back 2

Evolutionarily distinct domain of prokaryotic organisms.

Front 3

ATP

Back 3

Adenosine triphosphate. Nucleotide made of adenine, ribose, and three phosphate groups; main energy carrier in cells.

Front 4

bacteria

Back 4

The most widespread and diverse group of prokaryotic organisms.

Front 5

basal body

Back 5

An organelle that gives rise to cilia or flagella; resembles a centriole.

Front 6

cell

Back 6

Smallest living unit, with a capacity to survive and reproduce on its own.

Front 7

cell cortex

Back 7

Three-dimensional mesh of actin filaments and other proteins just under the plasma membrane.

Front 8

cell theory

Back 8

Idea that all organisms consist of similar units of organization called cells.

Front 9

cell wall

Back 9

A semirigid, permeable structure encloses the plasma membrane of many cells; helps cell retain its shape and resist rupturing.

Front 10

central vacuole

Back 10

Fluid-filled storage organelle of a plant cell.

Front 11

chloroplast

Back 11

Organelle of photosynthesis in plants and many protists.

Front 12

cytoplasm

Back 12

All cell parts, particles, and semifluid substances between the plasma membrane and the nucleus (or nucleoid).

Front 13

endoplasmic reticulum

Back 13

ER. Organelle that starts at the nuclear envelope and extends through cytoplasm. Smooth ER assembles membrane lipids, breaks down fatty acids, and inactivates some toxins; Rough ER (has ribosomes on its cytoplasmic side) modifies new polypeptide chains.

Front 14

fluid mosaic model

Back 14

A cell membrane is fluid because of the motions and interactions of its component lipids and proteins.

Front 15

Golgi body

Back 15

Organelle of endomembrane system; final modification of polypeptide chains into proteins, lipid assembly, and packaging of both in vesicles for secretion or for use inside cell.

Front 16

hydrostatic pressure

Back 16

Pressure exerted by a volume of fluid against a wall, membrane, or some other structure that encloses it.

Front 17

intermediate filament

Back 17

Cytoskeletal element; mechanically strengthens some animal cells.

Front 18

lipid bilayer

Back 18

Mainly phospholipids arranged tail-to-tail in two layers; structural basis of all cell membranes.

Front 19

microfilament

Back 19

Cytoskeletal element; consists of actin subunits. Involved in movement and structural integrity of cells.

Front 20

microtubule

Back 20

Cytoskeletal element; consists of tubulin subunits. Contributes to cell shape, growth, and motion; constituent of spindles.

Front 21

mitochondrion

Back 21

mitochondria; Organelle of ATP formation; site of aerobic respiration’s second and third stages.

Front 22

motor protein

Back 22

Protein that associates with microtubules or microfilaments and has a role in cell movement.

Front 23

nuclear envelope

Back 23

Lipid bilayer membrane enclosing the nucleus of eukaryotes.

Front 24

nucleoid

Back 24

Of bacterial cells, the region in which DNA is physically organized; not separated from the cytoplasm by a membrane.

Front 25

nucleus

Back 25

Organelle that physically separates DNA from the cytoplasm in a eukaryotic cell.

Front 26

organelle

Back 26

Membrane-bound compartment in the eukaryotic cytoplasm; has one or more specialized metabolic functions.

Front 27

osmotic pressure

Back 27

Hydrostatic pressure that counters inward diffusion of water through a selectively permeable membrane inside a cell or enclosed body region.

Front 28

phospholipid

Back 28

Lipid with a phosphate group. Major constituent of biological membranes.

Front 29

plasma membrane

Back 29

Outermost cell membrane; structural and functional boundary between the cytoplasm and fluid surrounding the cell.

Front 30

polypeptide chain

Back 30

Three or more amino acids linked by peptide bonds.

Front 31

ribosome

Back 31

Structure upon which polypeptide chains are built. An intact ribosome consists of two subunits of rRNA and proteins.

Front 32

surface-to-volume ratio

Back 32

Physical relationship in which volume increases with the cube of the diameter, but surface area increases with the square; constrains increases in cell size.

Front 33

wavelength

Back 33

A wavelike form of energy in motion. The horizontal distance between the crests of every two successive waves.