Unit 3 Vocabulary - Cells and Cell Membrane

Cell

The basic unit of structure and function in living things

Organelle

A tiny cell structure that carries out a specific function within the cell

Prokaryote

A unicellular organism that lacks a nucleus and membrane bound organelles

Eukaryote

A cell that contains a nucleus and membrane bound organelles

Unicellular

Made of a single cell

Multicellular

Made up of more than one cell.

Nucleus

Organelle that contains DNA and directs all of the cell's activities. it is also known as the control center of the cell.

DNA

Contains the genetic information of a living organism, found inside the nucleus in eukaryotes and inside the cytoplasm in prokaryotes

Cytoplasm

A gel-like fluid between the cell membrane and nucleus that suspends (holds) the organelles in place.

Vacuole

An organelle that stores cell materials such as food, water, or waste.

Mitochondria

Organelles that produce most of the cell's energy

Chloroplast

The site of photosynthesis; These organelles capture sunlight and convert the light energy into food for the cell.

Ribosomes

Tiny, round organelles that make proteins; they may be attached to the endoplasmic reticulum or float in the cytoplasm.

Surface Area

total area of the cell membrane, or the total area of the cell surface that is exposed to its environment

Cell membrane

Encloses and separates the internal parts of the cell from the outside environment; is semi-permeable and controls what enters/exits a cell

Phospholipid

A molecule that is makes up the majority of the cell membrane; has a polar, hydrophilic head and a nonpolar, hydrophobic tail.

Bilayer

a layer that is two molecules thick

Hydrophobic

water fearing (non polar)

Hydrophilic

water loving (polar)

Protein channel

A molecule embedded in the cell membrane that allows polar items to pass through the memberane

Cholesterol

A molecule in the cell membrane that provides support in animal cell membranes and ensures that the phospholipid bilayer is not "too fluid"

Selectively permeable

a property of cell membranes that allows some substances to pass through, while others cannot

Cell wall

A rigid outer layer of a plant cell that helps protect, support, and give shape to the cell

Diffusion

A type of passive transport by which gasses and hydrophobic (water fearing/nonpolar) molecules move from high concentration to low concentration directly through the membrane - sometimes "simple" is included with this term

Concentration

A measurement of how much solute exists within a certain volume of solvent

Concentration gradient

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

Molarity

A common measure of solute concentration, referring to the number of moles of solute per liter of solution.

Equilibrium

an equal concentration of molecules on both sides of the membrane

Osmosis

A type of passive transport by which water diffuses from an area of more water to an area of less water (towards where there is greater amount of solute)

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

Isotonic

Having the same solute concentration as another solution.

Homeostasis

relatively constant internal physical and chemical conditions that organisms maintain

Passive transport

A general term for the movement of substances across a cell membrane without the use of energy by the cell; there are three types

Facilitated diffusion

A type of passive transport by which hydrophilic (water loving/polar) molecules like ions or glucose can cross the cell membrane from high to low concentration by going through a protein channel

Active transport

Energy-requiring process that moves material across a cell membrane against a concentration gradient (low to high)

Protein pump

The term applied to a protein channel/transport protein that is working to move substances against the concentration gradient with the help of cell energy (ATP).

Polar

describes a molecule in which the positive and negative charges are separated; synonymous with water-loving or hydrophilic

Nonpolar

a molecule with equal sharing of electrons; synonymous with water-fearing or hydrophobic

Endocytosis

A type of active transport process by which a cell takes material into the cell by infolding of the cell membrane (high to low OR low to high)

Exocytosis

The active transport process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.