Agenda 9/29  Cell Organelle QUIZ  Pass back biomolecule quiz –Discuss corrections and retakes for those who failed to get to a 70 possibly.  Notes: The Cell Membrane and Transport.  Homework over the cell membrane due next class.

The Cell Membrane and Transport

Objective  Identify, investigate and explain cellular processes –Transport of molecules across the cell membrane

Three names  Phospholipid bi-layer  Cell membrane  Plasma membrane

What does the cell membrane do?  Regulates what enters & leaves the cell  Provides protection  Provides support  GOAL: HOMEOSTASIS

What does the cell membrane look like?

How does the cell membrane regulate what enters and leaves the cell?  Semi-permeable – Lets some things in and out of the cell, but not all things  Passive Transport – does NOT require energy  Active Transport – does require energy (ATP)

Passive Transport - Diffusion  Movement of particles (food) from HIGH concentration to LOW  Goal = equilibrium or balance of molecules both inside & outside the cell (HOMEOSTASIS)  Molecules flow through the lipid bi layer

What does diffusion look like?

Passive Transport – Facilitated Diffusion  For molecules that are too big to diffuse directly through the cell membrane

What is Facilitated Diffusion?  Membrane proteins will allow some molecules (like sugar) in or out of the cell that are too big to easily diffuse through the cell membrane.  Still moving from a high concentration to a low concentration…  NO ENERGY REQUIRED!

Every time a cell’s environment changes… Water is moving from a higher concentration to a lower concentration.

The name of this process is… Osmosis  The diffusion of water.  Just like the iodine diffused across the dialysis membrane, water moved across the egg’s membrane.

Objective  Identify, investigate and explain cellular processes –Transport of molecules across the cell membrane

Active Transport  Movement across the cell membrane from a LOW concentration to a HIGH concentration.  Requires energy (ATP)  One type uses membrane proteins to push large molecules across the semi – permeable cell membrane.

What does Active Transport look like? Image from “The Virtual Cell Textbook”

Endocytosis, Exocytosis endo: inside Exo: outside Cyto: cell  Help for the large: Both designed to move a large substance or a large amount of substance.  The cell membrane is flexible and can change shape to form a pocket.  Both require energy (ATP) Cell Transport: Moving Across the Cell Membrane

Endocytosis  The membrane folds inward, surrounds the material, and then fuses together.  The bubble created with materials is called a vesicle.  Materials are usually transported to the lysosome. Exocytosis  Vesicle transported to cytoplasm, vesicle fuses with cell membrane, and then releases its contents outside the cell Cell Transport: Moving Across the Cell Membrane

Objective  Identify, investigate and explain cellular processes –Transport of molecules across the cell membrane

Osmosis and Tonicity  Tonicity refers to the total solute concentration of the solution outside the cell.

What are the three types of tonicity? 1) Isotonic - equal 2) Hypotonic – lower; under 3) Hypertonic – higher, over

Isotonic  concentration of water (solvent) outside the cell is the same as the concentration inside the cell.

What will happen to a cell placed in an Isotonic solution?  The cell will have no net movement of water and will stay the same size.  Ex. Blood plasma has high concentration of albumin molecules to make it isotonic to tissues.

Hypotonic  concentration of water (solvent) outside the cell is higher than the concentration inside the cell.

What will happen to a cell placed in a Hypotonic solution?  The cell will gain water and swell.  If the cell bursts, then we call this lysis. (Red blood cells = hemolysis)  In plant cells with rigid cell walls, this creates turgor pressure.

Hypertonic  concentration of water (solvent) outside the cell is lower than the concentration inside the cell.

What will happen to a cell placed in a Hypertonic solution?  The cell will lose water and shrink.  In plant cells, the central vacuole will shrink and the plasma membrane will pull away from the cell wall causing the cytoplasm to shrink called plasmolysis.

Review Tonicity  What will happen to a red blood cell in a hypertonic solution?  What will happen to a red blood cell in an isotonic solution?  What will happen to a red blood cell in a hypotonic solution?

Eggs-periment  The egg without its shell is a cell with a semi-permeable membrane

Cell in Distilled Water  What will happen and WHY????

Cell in Corn Syrup  What will happen and WHY????

Objective  Identify, investigate and explain cellular processes –Transport of molecules across the cell membrane