Vocab Chapter 8

cell

cell

basic unit of all forms of life.

cell theory

fundamental concept of biology that states that all living things are composed of cells; that cells are the basic units of structure and function in living things; and that new cells are produced from existing cells.

cell membrane

thin, flexible barrier that surrounds all cells; regulates what enters and leaves the cell.

nucleus

in cells, structure that contains the cell’s genetic material in the form of DNA.

eukaryote

organism whose cells contain a nucleus.

prokaryote

unicellular organism that lacks a nucleus.

cytoplasm

fluid portion of the cell outside the nucleus.

organelle

specialized structure that preforms important cellular functions within a eukaryotic cell.

ribosome

cell organelle consisting of RNA and protein found throughout the cytoplasm in a cell; the site of protein synthesis.

endoplasmic reticulum

internal membrane system found in eukaryotic cells; place where lipid components of the cell membrane are assembled.

Golgi apparatus

organelle in cells that modifies, sorts and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or release outside the cell.

vacuole

cell organelle that stores materials such as water, salts, proteins, and carbohydrates.

lysosome

cell organelle that breaks down lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell.

chloroplast

organelle found in cells of plants and some other organisms that captures the energy from sunlight and converts it into chemical energy.

mitochondrion

cell organelle that converts the chemical energy stored in food into compounds that are more convenient for the cell to use.

cell wall

strong, supporting layer around the cell membrane in some cells.

lipid bilayer

flexible double-layered sheet that makes up the cell membrane and forms a barrier between the cell and its surroundings.

selective permeable

property of biological membranes that allows some substances to pass across it while others cannot; also called semipermeable membrane.

homeostasis

relatively constant internal physical and chemical conditions that organisms maintain.

diffusion

process by which particles tend to move from an area where they are more concentrated to an area where they are less concentrated.

facilitated diffusion

process of diffusion in which molecules pass across the membrane through cell membrane channels.

aquaporin

water channel protein in a cell.

osmosis

diffusion of water through a selectively permeable membrane.

isotonic

when the concentration of two solutions is the same.

hypertonic

when comparing two solutions, the solution with the greater concentration of solutes.

hypotonic

when comparing two solutions, the solution with the lesser concentration of solutes.

osmotic pressure

pressure that must be applied to prevent osmotic movement across a selectively permeable membrane.

tissue

group of similar cells that preforms a particular function.

organ

group of tissues that work other to perform closely related functions.

organ system

group of organs that work together to perform a specific function

receptor

on or in a cell, a specific protein to whose shape fits that of a specific molecular messenger, such as a hormone.

cytoskeleton

network of protein filaments in a eukaryotic cells that gives the cell its shape and internal organization and is involved in movement.