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Cells and their environment
Description of the different processes that happen inside a cell
14
Biology
9th Grade
01/05/2009

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Term
Semipermeable Membrane
Definition
An semipermeable membrane allows only certain molecules to pass through it.
Term
Diffusion
Definition
The movement of molecules from an area of high concentration to an area of low concentration.

Occurs as a result of the kinetic movement of the molecule,(WHY?)continue to spread out,from compressed when there close moving & bumping into each other, spreading each other out.

Ends with dynamic equilibrium in which molecules continue to move until their distribution is equal.

EX: Using smell good lotion, you first smell, then a few minutes behind you can smell, then another few minutes the whole class can smell.
Term
Concentration Gradient
Definition
A concentration gradient is the difference between the concentration of a particular molecule in one area and the concentration in an adjacent area.
Term
Osmosis
Definition
The diffusion of water across a semipermeable membrane from a high to low concentration.

Fluid around the cell is described as its tonicity (concentration of solutes & water) and there are three types 1) Isotonic 2) Hypotonic 3) Hypertonic.
Term
Isotonic
Definition
THe concentration of water and solutes outside and inside the cell is equal.

The normal shape of the cell is maintained.

EX: Normal saline solution
Term
Hypotonic
Definition
Low concentration of solute and high concentration of water outside the cell compared to inside the cell.

Water moves inside the cell faster than it moves outside the cell; cell may lyse(explode,burst)

The cell will continue to grow due to the overload of water due to the attraction of high concentration to low concentration.

EX: Distilled water (100% water no solutes)
Term
Hypertonic
Definition
High solutes, low water concentration outside the cell compared to inside the cell.

Water leaves the cell faster than it enters the cell; cell plasmolyzes(shrivels)

In animal cells the cell shrivels up while in the plant cell the cells cell wall contains it.

PLANT: To melted snow salt was was added, whole the salt water went down the road it killed the plants, taking their water.

ANIMAL: Diabetics blood is hypertonic, the cell loose water, making them thirsty.

EX: 10% NaCl solution
Term
Facilitated Diffusion
Definition
Process that moves molecules from a high to low concentration across a membrane with the use of carrier proteins(intergral)

Used especially with certain molecules such as GLUCOSE, amino acids, and ions.

GLucose is needed by all cells but is too large to go in so needs help by a carrier protein.

Molecules are usually too larger to move across without help.

NO ENERGY USED!!
Term
Active Processes
Definition
Movement with help from the cell in the form of energy from ATP.

Movement from a low to high concentration.

Known as moving AGAINST the gradient.(the way the molecules dont move)

ATP-aka-adenosine triphosphate

ATP-ADP-aka-adenosine phosphate

tPi+ENergy

t
Term
Active Transport
Definition
Movement of molecules from a low to high concentration across the cell membrane; known as solute pumps

Carrier proteins are used and the cell must use energy from ATP

ATP is broken down to form ADP and energy is released which the cell uses to move molecules against the gradient.
Term
Exocytosis
Definition
THE PROCESS OF RELEASING LARGE AMOUNTS OF MATERIAL FROM THE INSIDE OF HTE CELL TO THE OUTSIDE.

The membrane of the vacuole surrounding the membrane fuses with the cell membrane, forcing the contents out of the cell.

EX: Pumping of water out of the cell of a Paramecium using a contractile vacuole.
Term
Endocytosis
Definition
THE PROCESS OF TAKING MATERIALS INTO THE CELL BY MEANS OF INFOLDINGS OF THE CELL MEMBRANE.

Phagocytosis or "cell-eating" is bring in large, solid molecules.

Pinocytosis or "cell-drinking" is bringing in small, liquid molecules.
Term
Functions of Cell Membrane
Definition
*Holds the cells contents together

*Regulates what enters and leaves the cell

*Provides support, protection, shape to cell

*Communication with other cells and molecules

*A barrier between one cell and another cell and its environment

*Selective permeability- small in size, liquid solute, correct charge[ions(+or -)]
Term
Structure of the Cell Membrane
Definition
*Lipid bilayer- has two sides

*Mostly made of proteins and phospholipids

*Peripheral proteins- on the side or outside only

*Integral proteins- span the entire membrane

*Structure of phospholipids; one side hydrophobic(afraid of water) the other side is hydrophilic(loves water)
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