Plasma Membrane

Phospholipid

• Phospholipid Animations (3)

Phospho head – polar

Lipid tail - nonpolar

Phospholipid Bilayer

• Hydrophilic heads (water-loving)

Hydrophobic tails (water-hating)

Fluid Mosaic Model

• BBC Education - AS Guru - Biology - Cells - Pathways - Plasma Membranes

Proteins in Membrane

Cholesterol: add stability to membrane in higher temperatures

Carbohydrate Chain

Carbohydrate Chain: Used as Identification Markers

PROTEIN JOBS:

attaches to cytoskeleton

PROTEIN JOBS:

• Enzymes which are catalytic teams for molecular assembly lines

• A Biochemical Pathway (click on animation)

• Biochemical Pathway Animation II (CLICK-ALSO CLICK ON ARROWS)

PROTEIN JOBS-Receptors: enable cells to detect chemical

messages from other cells

PROTEIN JOB: Signal Transduction

• Receptor binds to trigger a chain reaction • EXAMPLE ANIMATION (CLICK ON

START AND NEXT) MAP Kinase Signal Transduction Animation by Dr. Vic Lemas at BioCreations

• Another Signal Transduction Animation Interactive Concepts in Biochemistry - Interactive Animations

Signal Transduction Diagram

Diffusion

• Movement of a substance from a region of higher concentration to a region of lower concentration

Diffusion

• Scientific Method (diffusion animation)

Facilitated Diffusion

• A protein helps the substance (like an ion) across the membrane

Facilitated Transport

• Facilitated diffusion involves the use of a protein to facilitate the movement of molecules across the membrane. 

• Cell Animations (scroll down to Carrier-mediated passive transport Facilitated transport)

Passive Transport

• Cell does not need to use energy

• Movement of molecules goes “down the gradient” (from high to low concentration)– Diffusion– osmosis– Facilitated diffusion

Active Transport

• During active transport, cell needs to use energy (ATP) as molecules against a concentration gradient (low concentration to high concentration).– endocytosis– Exocytosis– Pumps (USE ATP)

• Cell Animations (scroll down to active transport)

Comparing Active and Passive Transport

• Shockwave Click here

Endocytosis

• The process by which a cell engulfs material to bring it into the cell is called endocytosis. A vacuole is formed that contains the material that has been engulfed.

Exocytosis

• Vesicle fuses with plasma membrane to exit the material outside the cell

• (cell pooping)

Endocytosis Animation

• Endocytosis and Exocytosis Animation

• What is the difference between the two? Which brings material in and which brings materials out of the cell?

• Endocytosis is in

• Exocytosis is out

Diffusion: flow from high to low concentration

• Also facilitated diffusion (protein channel)

Diffusion

Things that can pass freely through the plasma membrane

• Hydrophobic molecules (oil soluble)• O2

• N2

• Nonpolar • Benzene• Small uncharged Polar  molecules • H2O• CO2

Molecules that don’t pass through the phospholipid bilayer

easily...• Large uncharged

• Glucose

• Polar molecules 

• Sucrose

• Ions (charged) H+ , Na+ , HCO3 , K+, Ca+2,Cl- , Mg+2

So what three characteristics of a molecule determine the

permeability of the membrane?

• Charge

• Size

• Polarity

• However: some molecules which we would think should (or should not) cross the plasma membrane do - (or don't) because of the presence of the membrane proteins.

Osmosis

• Osmosis is the movement of water from a region of high water concentration to a region of lower water concentration through a selectively permeable membrane.

• The Cell: Passive Transport Osmosis - Learning - click

Solution Vocabulary

Solute- what is being dissolved

EX: salt

Solvent –what is doing the dissolving

EX: water

Solution = solvent + solute

Osmosis

• Scientific Method (animation)

Hypotonic Solution

• Osmosis (click for animation)

• A hypotonic solution is one that has less solute (more water).

• Cells in hypotonic solution tend to gain water.

Isotonic Solution

• Osmosis (click for animation)• the concentration of solute is the same

on both sides of the membrane (inside the cell and outside).

• A cell placed in an isotonic solution neither gains or loses water. Most cells in the body are in an isotonic solution.

Drag the bag

• Osmosis (predict what will happen)

• LabBench (do a little experiment)

Hypertonic Solution

• Osmosis (click for animation)

• A hypertonic solution is one that has a high solute concentration.

• Cells in a hypertonic solution will lose water.

Plasmolysis

• Plant cells placed in a hypertonic solution will undergo plasmolysis, a condition where the plasma membrane pulls away from the cell wall as the cell shrinks.

• The cell wall is rigid and does not shrink. before

Osmosis Lab

• Use grams on the scale.

• Be very careful when carrying (use a spoon) and drying the egg (gently with a paper towel).

• Two set-ups per lab table. (If one side breaks, you have a back-up.)

• WHEN FINISHED: Clean beakers. Dry off scale and turn off.

• Plasmolysis of Elodea

• Also scroll down for rehydration of elodea

•Watch the chloroplasts

Plant Cell Plasmolysis

Stiff Cell wall

Plasmolysis: Flaccid: Turgid:

Sunken in Normal pressure Lots of pressure

Cell wall on cell wall on cell wall

Can you tell which is the plasmolyzed and which is normal

elodea?

Compare Plant Cells

• NORMAL CELLPlasmolysis

water moves toward the area with a higher solute concentration because it has a lower water

concentration.

water moves from hypotonic to hypertonic solution.

Red Blood Cells p. 83

Solutions

• If a cell is in a Hypotonic solution, the cell will…

• lose water

• If a cell is in a Hypertonic solution, the cell will…

• gain water

Turgor: pressure of water vacuole on the cell wall of a plant

Active Transport

• Active Transport Animation

• Cell needs energy to move particles “against the gradient” - from low to high concentration

Active Transport

Active Transport

• "pumps" materials across the membrane against the concentration gradient. i.e. ,from low concentration to high concentration (therefore it requires energy).

Endocytosis

• Endocytosis: Large materials transported into the cell.

• Endocytosis includes three slightly different processes:– Phagocytosis– Pinocytosis– Receptor-mediated

Endocytosis

• Endocytosis - "to enter the cell"• Phagocytosis - large particles - membrane

"reaches out" - phago = eat" • Pinocytosis - solutes in fluids - membrane folds

in to form a pouch known as a vesicle. - pino = drinking"

• Receptor mediated endocytosis - receptors on the membrane attach to large molecules like hormones and folds them inside.

Phagocytosis

• Animations:• Phagocytosis

• Phagocytosis | Flash simulation, Animation, Illustration, Picture, Diagram - eduMedia

Engulfing large particles

“Cell eating”

Pinocytosis

• “Cell drinking”

• Engulfing small liquid droplets

Receptor-Mediated Endocytosis

• Receptor Mediated Endocytosis

• Specialized receptor that just fits a specific substance

• EX: LDL• Hormones• insulin

Receptor Mediated Endocytosis

Exocytosis

• Material (wastes etc.) are

expelled from the cell

• Table 8.2: Five processes by which substances move across cell membranes. •   Particle Protein Energy Movement Carrier RequiredSimple High to low No NoDiffusion   FacilitatedDiffusion High to low Yes No

ActiveTransport   Low to high Yes Yes

Exocytosis Intracellularl to extracellular No, occurs by fusion     of vesicles with    cell membrane.

 Endocytosis Extracellular to intracellular No, occurs by involution of cell membrane.     

•

Exocytosis