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Cellular Transport Notes. Ch. 3.4. About Cell Membranes. All cells have a cell membrane Functions : Controls what enters and exits the cell to maintain an internal balance called homeostasis. Separate cytoplasm from the environment. TEM picture of a real cell membrane.

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about cell membranes
About Cell Membranes
  • All cells have a cell membrane
  • Functions:
    • Controls what enters and exits the cell to maintain an internal balance called homeostasis.
    • Separate cytoplasm from the environment

TEM picture of a real cell membrane.

about cell membranes continued
About Cell Membranes (continued)
  • Structure of cell membrane

Lipid Bilayer -2 layers of phospholipids

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

Phospholipid

Lipid Bilayer

slide4

Fluid Mosaic Model of the cell membrane

Polar heads love water & dissolve.

http://www.susanahalpine.com/anim/Life/memb.htm

Non-polar tails hide from water.

Carbohydrate cell markers

Proteins

about cell membranes continued1
About Cell Membranes (continued)
  • 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

slide6

Structure of the Cell Membrane

Outside of cell

Carbohydrate

chains

Proteins

Lipid

Bilayer

Transport

Protein

Phospholipids

Inside of cell

(cytoplasm)

Go to Section:

effects of osmosis on life
Effects of Osmosis on Life
  • A cell maintains homeostasis (maintaining a stable, internal environment) throughosmosis.

Osmosis- diffusion of waterthrough a selectively permeablemembrane.

Only water molecules move by themselves through the membrane.

osmosis
Osmosis

CONCENTRATED SOLUTION

DILUTE SOLUTION

Cell membrane partially permeable.

Sugar molecule

VERY Low concentrationof water molecules.

Outside cell

Inside cell

VERY High concentration of water molecules.

AS Biology, Cell membranes and Transport

osmosis1
Osmosis

Cell membrane partially permeable.

Low conc. of water molecules.

OSMOSIS

High conc. of water molecules.

Outside cell

Inside cell

AS Biology, Cell membranes and Transport

osmosis2
Osmosis

Cell membrane partially permeable.

OSMOSIS

Outside cell

Inside cell

EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water – water moves in and out of cell at the same rate.

AS Biology, Cell membranes and Transport

slide11

What is a solution?

  • 2 Parts:
  • Solvent – Usually a liquid like water
  • Solute – Usually a solid such as sugar, salt
hypotonic solution

Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

Hypotonic Solution

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

Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

hypertonic solution

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 (HYPER); Low water)

shrinks

Result:Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

isotonic solution

Osmosis Animations for isotonic, hypertonic, and hypotonic solutions

Isotonic Solution

Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell.

ISO = THE SAME

Result:Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

slide17

What type of solution are these cells in?

B

C

A

Hypertonic

Isotonic

Hypotonic

types of cellular transport
Types of Cellular Transport

Passive Transport

cell doesn’t useenergy

Diffusion

Facilitated Diffusion

Osmosis

Active Transport

cell does use energy

Protein Pumps

Endocytosis

Exocytosis

  • Animations of Active Transport & Passive Transport

Weeee!!!

high

low

This is gonna be hard work!!

high

low

passive transport
Passive Transport
  • cell uses no energy
  • molecules move randomly
  • Molecules spread out from an area of high concentration to an area of lowconcentration. (With the concentration gradient)
  • (HighLow)
  • Three types:
3 types of passive transport
3 Types of Passive Transport
  • Diffusion – Gases such as O2 and CO2.
  • Osmosis – diffusion of water
  • Facilitated Diffusion – diffusion with the help of transport proteins – transport of sugars, ions and amino acids.
passive transport 1 diffusion

Simple Diffusion Animation

Passive Transport:1. Diffusion
  • 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.

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

slide22

Passive Transport: 2. Facilitated Diffusion

A

B

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

  • Transport Proteins are specific – they “select” only certain molecules to cross the membrane
  • Transports larger or charged molecules

Facilitated diffusion(Channel Protein)

Diffusion (Lipid Bilayer)

Carrier Protein

  • http://bio.winona.edu/berg/Free.htm
slide23

Passive Transport: 2. Facilitated Diffusion

Glucose

molecules

Cellular Transport From a-

High

High Concentration

  • Channel Proteins animations

Cell Membrane

Protein

channel

Low Concentration

Low

Transport Protein

Through a 

Go to Section:

slide24

Facilitated Diffusion:Molecules will randomly move through the opening like pore, by diffusion. This requires no energy, it is a PASSIVE process. Molecules move from an area of high concentration to an area of low conc.

AS Biology, Cell membranes and Transport

active transport
Active Transport
  • cell uses energy
  • actively moves molecules to where they are needed
  • Movement from an area of low concentration to an area of high concentration (Against the concentration gradient)
  • (Low  High)
  • Three Types:
types of active transport
Types of Active Transport
  • 1. Protein Pumps -transport proteins that require energy to do work
    • Example:Sodium / Potassium Pumps are important in nerve responses.

Protein changes shape to move molecules: this requires energy!

types of active transport1
Types of Active Transport
  • 2.Endocytosis: taking bulky material into a cell
    • 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 transport2
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 wastes released from cell
how organisms deal with osmotic pressure
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 paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.
  • Salt water fish pump salt out of their specialized gills so they do not dehydrate.
  • Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.
slide30

Paramecium

Contractile vacuole full

Contractile vacuole empty

slide31

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