Holt McDougal Biology Chapter 3

Cell Theory

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

Cytoplasm

A jellylike substance that contains dissolved molecular building blocks - such as proteins, nucleic acids, minerals, and ions.

Organelles

Structures specialized to perform distinct processes within a cell.

Prokaryotic cells

Cells that do not have a nucleus or other membrane - bound organelles.

Eukaryotic cells

Cells that have a nucleus and other membrane - bound organelles.

Cytoskeleton

A network of proteins that is constantly changing to meet the needs of a cell.

Nucleus

The storehouse for most of the genetic information, or DNA (deoxyribonucleic acid), in your cells.

Endoplasmic Reticulum

(ER) An interconnected network of thin, folded membranes that produce, process, and distribute proteins.

Ribosomes

Tiny organelles that link amino acids together to form proteins.

Golgi apparatus

Consists of closely layered stacks of membrane - enclosed spaces that process, sort, and deliver proteins.

Vesicles

General name used to describe small membrane - bound sacs that divide some materials from the rest of the cytoplasm and transport these materials from place to place within the cell.

Mitochodria

Supply energy to the cell. These organelles have their own ribosomes and DNA. (They have two membranes)

Vacuole

A fluid - filled sac used for the storage of materials needed by a cell.

Lysosomes

Membrane - bound organelles that contain enzymes. They defend the cell from invading bacteria and viruses. They also break down damaged and unwanted cell parts.

Centrioles

Cylinder - shaped organelles made of short microtubules arranged in a circle.

Cell Wall

A rigid layer that gives protection, support, and shape to the cell.

Chloroplasts

Organelles that carry out photosynthesis, a series of complex chemical reactions that convert solar energy into energy - rich molecules the cell can use.

Cell membrane

(Plasma Membrane) Forms a boundary between a cell and the outside environment and controls the passage of materials into and out of a cell.

Phospholipid

A molecule composed of three basic parts:
a charged phosphate group, glycerol, and two fatty acid chains.

Fluid Mosaic Model

Describes the arrangement of the molecules that make up a cell membrane.

Selective Permeability

Means it allows some, but not all, materials to cross.

Receptor

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

Passive Transport

The movement of molecules across a cell membrane without energy input from the cell. (Also described as the diffusion of molecules across a membrane.)

Diffusion

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

Concentration Gradient

The 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 higher water concentration to an area of lower 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

The diffusion of molecules across a membrane through transport proteins.

Active Transport

Drives molecules across a membrane from a region of lower concentration to a region of higher concentration.

Endocytosis

The process of taking liquids or fairly large molecules into a cell by engulfing them in a membrane.

Phagocytosis

A type of endocytosis in which the cell membrane engulfs large particles.

Exocytosis

The opposite of endocytosis, is the release of substances out of a cell by the fusion of a vesicle with the membrane.

Microtubules

Long hollow tubes that give the cell its shape and act as "tracks" for the movement of organelles.

Intermediate Filaments

They are somewhat smaller than microtubules, and they give a cell its strength.

Microfilaments

The smallest of the three, are tiny threads that enable cells to move and divide.

Cytosol

The fluid portion of the cytoplasm; it consists mostly of water.

Nucleolus

A dense region inside of the nucleus where tiny organelles that are essential for making proteins are assembled.

Nuclear Envelope

The double membrane in which the nucleus and the DNA of the cell are enclosed in. It is pierced with holes (pores) that allow large molecules to pass through the nucleus and the cytoplasm.

Lumen

The interior of the Endoplasmic Reticulum.

Enzymes

They are proteins.

Centrosome

A small region of cytoplasm that produces microtubules.

Ligand

The molecule a receptor binds to.

Intracellular Receptor

A molecule may cross the cell membrane and bind with this. Intracellular means "within, or inside, a cell". (When the ligand and the receptor bind, they change shape)

Membrane Receptor

A molecule that cannot cross the membrane may bind to a receptor in the cell membrane.

Dynamic Equilibrium

When molecules are evenly spread throughout the solution. The concentration of molecules is the same throughout the solution (equilibrium), but the molecules continue to move (dynamic).