R. Mitchell

Vocabulary

• Cell Membrane
• Cellular Transport
• Equillibrium
• Selective Permeability
• Active Transport
• Passive Transport
• Osmosis
• Diffusion
• Facilitated Diffusion
• Endocytosis
• Exocytosis
• Protein Pump
• Homeostasis

• All cells have a cell membrane

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• Functions:
• Controls what enters and exits the cell to maintain an internal balance called homeostasis
• ​
• Provides protection and support for the cell

TEM picture of a real cell membrane.

• regulation of body temperature
• control of blood glucose levels
• the regulation of salt and water balance

• Structure of cell membrane

Lipid Bilayer -2 layers of phospholipids

• Phosphate head is polar (water loving)
• Fatty acid tails non-polar (water fearing)
• Proteins embedded in membrane

Phospholipid

Lipid Bilayer

Proteins

Membrane movement animation

Polar heads love water & dissolve.

Non-polar tails hide from water.

Carbohydrate cell markers

Fluid Mosaic Model of the cell membrane

• 4. Cell membranes have pores (holes) in it
• Selectively permeable: Allows some molecules in and keeps other molecules out
• ​
• The structure helps it be selective!

Pores

Outside of cell

Inside of cell

(cytoplasm)

Lipid

Bilayer

Proteins

Transport

Protein

Phospholipids

Carbohydrate

chains

Go to Section:

Animations

of membrane structure

• Passive Transport

cell doesn’t use energy

• Diffusion
• Facilitated Diffusion
• Osmosis
• ​
• Active Transport

cell does use energy

• Protein Pumps
• Endocytosis
• Exocytosis

high

low

This is gonna be hard work!!

high

low

Weeee!!!

• Animations of Active Transport & Passive Transport

• cell uses no energy
• molecules move randomly
• Molecules spread out from an area of high concentration to an area of low concentration.
• (HighLow)

• Diffusion
• Facilitative Diffusion – diffusion with the help of transport proteins
• Osmosis – diffusion of water

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• Diffusion: random movement of particles from an area of high concentration to an area of low concentration.

(High to Low)

• Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out.

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http://bio.winona.edu/berg/Free.htm

Simple Diffusion Animation

2. Facilitated diffusion: diffusion of large specific particles through transport proteins found in the membrane

HighLow

Facilitated diffusion (Channel Protein)

Diffusion (Lipid Bilayer)

Carrier Protein

A

B

• http://bio.winona.edu/berg/Free.htm

Glucose

molecules

Protein

channel

Go to Section:

Transport Protein

High

Low

• Channel Proteins animations

• 3.Osmosis: diffusion of water through a selectively permeable membrane

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• Water moves from high to low concentrations
• ​
• ​

• Water moves freely through pores.
• Solute (green) to large to move across.

Osmosis animation

• cell uses energy
• Movement from an area of low concentration to an area of high concentration
• (Low  High)

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• Protein Pumps
• Endocytosis
• Exocytosis

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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!

• 2. Endocytosis: taking bulky material into a cell
• ​
• Uses energy
• ​
• Cell membrane in-folds around food particle

Amoeba Eating Paramecium

3. Exocytosis: Forces material out of cell in bulk

• ​
• membrane surrounding the material fuses with cell membrane
• ​
• requires energy
• ​
• EX: Hormones or wastes released from cell

Endocytosis & Exocytosis animations

• Osmosis- diffusion of water through a selectively permeable membrane

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

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Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water)

Effect:

• Water moves inside the cell
• Cell Swells and bursts

• Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water)

Effect:

• Water moves out of the cell
• Cell shrinks

• Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

shrinks

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
• The cell remains same size

• Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

What type of solution are these cells in?

A

C

B

Hypertonic

Isotonic

Hypotonic