Cell Transport

Learning Objectives

1. List at least 2 purposes of the cell membrane.

2. Name the 3 types of passive transport.

3. Name the 2 types of active transport.

4. Describe the difference between passive & active

transport in 2-3 well-written sentences.

5. Write a short paragraph on how osmosis plays a role

in the homeostasis of red blood cells using the words:

hypertonic, hypotonic, and isotonic.

Cell Membranes

• All cells have a cell membrane

• Functions:

a. Controls what enters and exits the cell (it is selectively permeable) to maintain an internal balance called homeostasis

b. Provides protection and support for the cell TEM picture of a real

cell membrane.

The “Fluid Mosaic Model”

https://youtu.be/Qqsf_UJcfBc and

http://www.stolaf.edu/people/giannini/flashanimat/lipids/mem

brane%20fluidity.swf

Passive & Active Transport

• Cell membrane = semipermeable (selectively permeable). Some substances pass through while others can’t

• Materials can enter/exit the cell via (1) passive transport or (2) active transport.

Types of Cellular Transport

• Passive Transport

Cell doesn’t use energy1. Diffusion

2. Facilitated Diffusion

3. Osmosis

• Active Transport

Cell does use energy1. Protein Pumps

2. Endocytosis

3. Exocytosis

High

concentration

Low concentration

Weeee!!!

High

concentration

Low concentration

This is

hard

work!!

Passive Transport: Diffusion

Cell Membrane

Inside Cell

Outside Cell

Solutes

Higher concentration of solute

on one side of the membrane

than the other

Diffusion causes net movement

of solute particles from the side

of the membrane with the higher

solute concentration to the side

with the lower solute

concentration.

At equilibrium, particles move

equally in both directions, so

there is no net change.

Diffusion: Example

Food coloring in hot/cold water.

https://www.youtube.com/watch?v=9ghYur0vqgE

Passive Transport: Facilitated Diffusion

Facilitated Diffusion Example

https://www.youtube.com/watch?v=vKGN_Zhz8AY

Passive Transport: Osmosis

aquaporin

water

cell membrane

sugar

Passive Transport

Osmosis – diffusion of water (high low concentration)

http://kids.britannica.com/comptons/art-53766/An-example-of-osmosis-occurs-when-a-sugar-solution-and

The sugar

(solute)

molecule is

too big to

move across

the

membrane.

POP QUIZ!!!

What is the

solvent?

Solute: what is being dissolvedSolvent: what dissolves the solute.

Osmosis

Effects of Osmosis on

Life

There are 3 types of

solutions that involve

water and how they

affect the cell.

1. Hypertonic Solution: the solution the cell is placed in

has less water than the cell (more solute; less water)

2. Hypotonic Solution: the solution the cell is placed in

has more water then the cell (less solute; more water)

3. Isotonic Solution: the solution the cell is placed in has

equal amount of water as the cell (equilibrium!)

Osmosis in Cells

Isotonic Hypertonic Hypotonic

In what type of solution are these cells?

A CB

Hypertonic Isotonic Hypotonic

Hypotonic Solution

Hypotonic: The solution has a lower concentration of

solutes and a higher concentration of water than inside the

cell. (Low solute; High water)

Result: Water moves from the solution to inside the cell): Cell

Swells and bursts open (lyse)!

• Osmosis Animations for isotonic,

hypertonic, and hypotonic solutions

Hypertonic Solution

Hypertonic: The solution has a higher concentration of

solutes and a lower concentration of water than inside the

cell. (High solute; Low water)

Result: Water moves out of the cell into the solution:

Cell shrivels!

• Osmosis Animations for isotonic,

hypertonic, and hypotonic solutions

shrinks

Isotonic Solution

Isotonic: The concentration of solutes in the solution is

equal to the concentration of solutes inside the cell.

Result: Water moves equally in both directions and the cell

remains same size! (Dynamic Equilibrium)

• Osmosis Animations for isotonic,

hypertonic, and hypotonic solutions

How Organisms Deal with Osmotic Pressure

• Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure.

• A protist like the paramecium has contractile vacuolesthat collect water flowing in and pump it out to prevent them from over-expanding.

• Salt water fish pump salt out of their specialized glands in gills so they do not dehydrate.

• Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.

• Paramecium (protist) removing excess water video

Active Transport

Protein pumps Endocytosis Exocytosis

Example: Sodium /

Potassium Pumps are

important in nerve

responses.

Example for endocytosis is the

leukocytes, neutrophils, and

monocytes can engulf foreign

substances like bacteria

Example secretion of enzymes

from pancreatic cells and

hormones from endocrine

glands

ACTIVE TRANSPORT

• Moves substances from lower concentration to higher concentration.

• Requires ENERGY.

– What is the source of energy?

Types of Active Transport

1. Protein Pumps -

transport proteins that

require energy to do work

• Example: Sodium /

Potassium Pumps are

important in nerve

responses.

Sodium Potassium

Pumps (Active

Transport using

proteins)

Protein changes

shape to move

molecules: this

requires energy!

Types of Active Transport

2. Endocytosis: taking bulky material into a cell by forming a vesicle

• Uses energy

• Cell membrane in-folds around food particle

• “cell eating”

• forms food vacuole & digests food

• This is how white blood cells eat bacteria!

Types of Active Transport

3. Exocytosis: Forces material out of cell in bulk

• Membrane surrounding the material fuses with cell membrane

• Cell changes shape –requires energy

• Ex: Hormones or wastesreleased from cell

Endocytosis &

Exocytosis

animations

Endocytosis

Active Transport vs. Diffusion

Compare and contrast active transport and diffusion.

More Vocab!!

Plasmolysis: shrinking of the cytoplasm away from the wall

of a living cell

Turgor pressure: the pressure exerted on a plant cell wall

by water passing into the cell by osmosis

Crenation: a process resulting from osmosis in which red

blood cells, in a hypertonic solution, shrink/shrivel

Lysis: cell rupture/bursting