Cell Structure and Transport

organelle

Functional units inside a cell that perform specific tasks required by the cell.

cytoplasm

Jelly-like fluid organelle inside the cell in which the organelles are suspended.

mitochondria

Organelle found in both plants and animals that converts the chemical energy stored in glucose into ATP.

nucleus

Semipermeable organelle that contains the genetic material of a cell, and is the site of DNA replication.

cell membrane

Semipermeable barrier surrounding the cytoplasm of a cell.

cell wall

Rigid structural organelle that surrounds the cell membrane and provides support to the plant cell.

phospholipid

Major component of the cell membrane that has a hydrophilic head and hydrophobic tails.

chloroplast

Organelle found only in plants, that is the site of photosynthesis.

vacuole

Fluid-filled organelle in both animal and plant cells that stores water and minerals.

semi-permeable

Ability of cell membranes to allow some substances to pass it but not others.

passive transport

Transport of a substance across a cell membrane by diffusion; Energy is not required.

active transport

Movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.

diffusion

Passive movement of molecules down a concentration gradient.

facilitated diffusion

Transport of substances across a membrane from an area of higher concentration to an area of lower concentration by means of a transmembrane protein.

osmosis

Movement of water molecules from an area of high concentration to an area of low concentration through a semipermeable membrane.

channel proteins

Transmembrane protein that is open to both ends.

carrier proteins

Transmembrane protein that is only open to one side of the membrane at a time, and changes shape to transport molecules through the cell membrane.

SA : V ratio

Ratio of the cell's surface area and its volume.

concentration gradient

When a solute is more concentrated in one area compared to another.

tonicity

Difference in relative concentration of solutes of two solutions, which determines the direction of osmosis.

hypotonic

Solution that has a lower concentration of solute than the cell.

isotonic

Solution that has an equal concentration of solute compared with the cell.

hypertonic

Solution that has a higher concentration of solute than the cell.

plasmolysis

Collapse of a plant cell's cytoplasm due to a lack of water.

turgidity

Pressure created by water pushing up against the cell wall