Movement Through

the Cell Membrane

Cellular Movement

All living organisms rely on diffusion

– Get oxygen for respiration

– Removing waste products

– Transpiration in plants

Cellular Movement

The cell membrane helps to regulate

what moves into and out of the cell

The Cell Membrane

The cell membrane is like a soap

bubble.

– Flexible membrane

– Seals the inside of the cell from its

outside environment

The Cell Membrane

All cells have a cell membrane

Function:

a. Regulates what enters and exits the cell to maintain an internal balance called

b. Provides protection and support for the cell

c. Takes in food and water and eliminates wastes

homeostasis

The Cell Membrane

The cell membrane is made up of a

double layered sheet known as the

phospholipid bilayer

Phospholipid

Lipid Bilayer

The Cell Membrane

Structure

a. Phosphate head is

hydrophylic

b. Fatty acid tails

hydrophobic

The cell membrane Is a “mosaic” of many

different molecules

The Cell Membrane

And is

“fluid”

due to the

movement

of its

molecules

Cell membrane is selectively permeable

It has pores (holes) in it which allows some

molecules in and keeps other molecules out

This structure

helps it be

selective!

The Cell Membrane

Pore Carbohydrate

chains

Lipid bilayer

Proteins

Cell membrane

Protein

channel

Outside of cell

Inside of cell (cytoplasm)

Lipid Bilayer

Proteins

Transport Protein Phospholipids

Carbohydrate chains

The Cell Membrane Review

Passive Transport - doesn’t use energy

1. Diffusion

2. Osmosis

3. Facilitated Diffusion

Active Transport -uses energy

1. Protein Pumps

2. Exocytosis

3. Endocytosis high

low

This is

gonna

be hard

work!!

high

low

Weeee!!

!

Types of Cellular Transport

Molecules move randomly

Area of high concentration to an area

of low concentration.

Passive Transport

high

low

Weeee!!

!

Diffusion continues until all molecules

are evenly spaced (equilibrium is

reached)-Note: molecules will still

move around but stay

spread out.

1. Diffusion

Gas exchange at the alveoli and blood

Gas exchange for photosynthesis

through the stomata

Gas exchange for respiration

1. Diffusion

Diffusion of water through a selectively

permeable membrane

2. Osmosis

Absorption of water by plant roots

Re-absorption of water in the kidneys

Absorption of water by the alimentary canal

2. Osmosis

2. Osmosis

Water is so small and there is so much of it, the cell can’t control it’s movement through the cell membrane.

When there are more

water molecules

OUTSIDE the cell,

water moves INTO

the cell. The Cell

swells.

2. Osmosis at work

When there are

more water

molecules INSIDE

the cell, water

moves OUT OF

the cell the Cell

shrinks.

2. Osmosis at work

Effect of salt

– Salt makes water move out of the cell so

it dries the cell out

2. Osmosis at work

Different Solutions

HYPERTONIC: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell.

Water moves across the membrane out of the cell

2. Osmosis at work

(High solute; Low water)

Hypertonic Solution

Hypertonic:

Result: Water moves from inside the cell….out

into the solution:

shrinks

Cell shrinks (Plasmolysis)!

Different Solutions

HYPOTONIC: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell.

Water moves across the membrane into the cell

2. Osmosis at work

(Low solute; High water)

Hypotonic Solution

Hypotonic:

Result: Water moves from the solution to inside

the cell: Cell swells and bursts open (cytolysis)!

swells

Different Solutions

HYPOTONIC: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell.

Water moves across the membrane into the cell

2. Osmosis at work

(Equal solute; Equal water)

Isotonic Solution

Isotonic: (equal solute; equal water)

Result: Water moves equally in both directions

and the cell remains same size!

Osmosis Animations for

isotonic, hypertonic, and

hypotonic solutions

(Dynamic Equilibrium)

A C B

Hypertonic Isotonic Hypotonic

What type of solution are these cells in?

•In plants, the pressure exerted on the cell wall is

called tugor pressure.

How Organisms Deal

with Osmotic Pressure

Effect of

Osmosis on

Plant Cells

Certain molecules are

able to diffuse

directly across the

lipid bilayer

(simple diffusion)

while others diffuse

across the membrane

differently

(facilitated diffusion)

3. Facilitated Diffusion

Glucose

Amino acids

3. Facilitated Diffusion

Carrier Proteins- allow the diffusion of

molecules across the membrane if they are

unable to cross via the cell membrane.

3. Facilitated Diffusion

Much like the Shape-O toy,

protein channels are

specific to certain kinds

of molecules.

3. Facilitated Diffusion

Definition

Active Transport

The movement of material against the

concentration gradient, that is from an area of low

concentration to an area of high concentration

this type of

transport requires

_______

in the form of ATP.

energy

Active Transport

Active Transport

Re-absorption of products in the

kidney

Sodium and potassium in cell

membranes

•Actively moves molecules to where

they are needed

•Different types:

*Protein Pump

•Endocytosis

•Exocytosis

Active Transport

Transport Proteins

move ions against the

force of diffusion

•Example: sodium /

potassium pump

are important in

nerve responses. Protein changes

shape to move

molecules: this

requires energy!

1. Protein Pumps

Show video clip

Sodium

Potassium Pumps

(Active Transport

using proteins)

1. Protein Pumps

How Does This Happen?

– Solute binds to protein

– Mitochondria provides

energy that changes the

shape of the protein

– Change in shape allows solute to be

moved across membrane

– System resets

Key fact:

ALL forms of

active transport

require . . .

ENERGY!!!

Active Transport

•http://www.northland.cc.mn.us/biology/

Biology1111/animations/active1.swf

•Cellular Movement

This is a great review of all the

cellular transport processes

Types of Cellular Transport