Learn: Biology: Chapter 3 - Cell Structure and Function

cell theory

theory that states that all organisms are made of cells, all cells are produced by other living cells, and the cell is the most basic unit of life.

cytoplasm

jellylike substance inside cells that contains molecules and in some cells organelles.

organelle

membrane-bound structure that is specialized to perform a distinct process within a cell.

prokaryotic cell

cell that does not have a nucleus or other membrane-bound organelles.

eukaryotic cell

cell that has a nucleus and other membrane-bound organelles.

cytoskeleton

network of proteins, such as microtubules and microfilaments, inside a eukaryotic cell that supports and shapes the cell.

nucleus

organelle composed of a double membrane that acts as the storehouse for most of a cell's DNA.

endoplasmic reticulum

interconnected network of thin, folded membranes that produce, process, and distribute proteins.

ribosome

organelle that links amino acids together to form proteins.

golgi apparatus

stack of flat, membrane-enclosed spaces containing enzymes that process, sort, and deliver proteins.

vesicle

small organelle that contains and transports materials within the cytoplasm.

mitochondrion

bean-shaped organelle that supplies energy to the cell and has its own ribosomes and DNA.

vacuole

organelle that is used to store materials, such as water, food, or enzymes, that are needed by the cell.

lysosome

organelle that contains enzymes.

centriole

small cylinder-shaped organelle made of protein tubes arranged in a circle; aids mitosis.

cell wall

rigid structure that gives protection, support, and shape to cells in plants, algae, fungi, and bacteria.

chloroplast

organelle composed of numerous membranes that are used to convert solar energy into chemical energy; contains chlorophyll.

cell membrane

double-layer of phospholipids that forms a boundary between a cell and the surrounding environment and controls the passage of materials into and out of a cell.

phospholipid

molecule that forms a double-layered cell membrane; consists of a glycerol, a phosphate group, and two fatty acids.

fluid mosaic model

model that describes the arrangement and movement of the molecules that make up a cell membrane.

selective permeability

condition or quality of allowing some, but not all, materials to cross a barrier or membrane.

receptor

protein that detects a signal molecule and performs an action in response.

passive transport

movement of molecules across the cell membrane without energy input from the cell.

diffusion

movement of dissolved molecules in a fluid or gas from a region of higher concentration to a region of lower concentration.

concentration gradient

difference in the concentration of a substance from one location to another.

osmosis

diffusion of water molecules across a semipermeable membrane from an area of high water concentration to an area of low water concentration.

isotonic

solution that has an equal concentration of dissolved particles compared with another solution.

hypertonic

solution that has a higher concentration of dissolved particles compared with another solution.

hypotonic

solution that has a lower concentration of dissolved particles compared with another solution.

facilitated diffusion

diffusion of molecules assisted by protein channels that pierce a cell membrane.

active transport

energy-requiring movement of molecules across a membrane from a region of lower concentration to a region of higher concentration.

endocytosis

uptake of liquids or large molecules into a cell by inward folding of the cell membrane.

phagocytosis

uptake of a solid particle into a cell by engulfing the particle; see endocytosis.

exocytosis

release of substances out a cell by the fusion of a vesicle with the membrane.