Cellular Transport

A. Moving Materials Into and out of Cells Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells.

Cell Membrane Functions) 1)The cell membrane regulates what enters and leaves the cell. 2)The cell membrane provides protection and support for the cell. 3) Communicate with other cells. The cell membrane acts as a BARRIER, separating the cell’s inside from its outside

The cell membrane is made out of a structure called the phospholipid bilayer. Bilayer= double layer.

What is a phospholipid? A phospholipid is a lipid with a phosphate group attached. The heads of phospholipids love water. The tails of phospholipids hate water.

Proteins in the Plasma Membrane There are 3 key proteins embedded into the plasma membrane that are important for cell function. 1.Transport Proteins 2.Marker Proteins 3.Receptor Proteins

Transport proteins are responsible for moving materials in and out of the cell. Marker proteins are like nametags that identify the cell. Receptor proteins allow the cell to interact and communicate with other cells by picking up signals from other cells.

Cell Transport There are TWO types of cell transport: 1)Passive transport- NO ENERGY required. 2)Active transport- Energy required.

In passive transport, substances move across the cell membrane. Substances move from HIGH to LOW concentrations. High concentration of substances

This is ALSO known as DIFFUSION. Simple diffusion= The movement of solutes from high concentrations to low concentrations. Osmosis= the diffusion of WATER.

Diffusion, Osmosis, Facilitated Diffusion 3 types of Passive Transport: When the concentration of the molecules of a substance is the same throughout a space, a state of equilibrium exists.

Osmosis Osmosis is the movement of water across a membrane in the direction low solute concentration to high solute concentration.

3 Types of Solutions: Solute concentration in the environment is higher than that in the cell. Causes water to move out of the cell; cell will shrink. This is why it is dangerous to drink sea water - its a myth that drinking sea water will cause you to go insane, but people marooned at sea will speed up dehydration (and death) by drinking sea water.

Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

Solute concentration in the environment is lower than that in the cell. Causes water to move into the cell; cell will expand and possibly burst.

Solute concentration in the environment is equal to that in the cell. Equal amounts of water will move into or out of the cell; cell volume remains constant.

Facilitated Diffusion Facilitated Diffusion is the transport of particles through a membrane by a transport protein, called a channel or carrier protein. Channel Carrier

How it works? Facilitated diffusion can help substances move either into or out of a cell, depending on the concentration of particles. Channel

Active Transport Active Transport often involves carrier proteins. The carrier proteins act as pumps that use energy to move ions and molecules across the membrane. ATP supplies the energy needed by carrier proteins.

In plants, active transport enables roots to absorb nutrients from the soil Active transport in the root cell membrane enables the plant to absorb the nutrients.