Agenda• Attendance• Review membrane proteins• What the heck is the Cell membrane for

anyway?• Cell Membrane PowerPoint• Video• Build the Cell membrane• Color The FMM

Cell Transport/Fluid Mosaic Model

The Inner life of the Cellhttp://multimedia.mcb.harvard.edu/anim_innerlife_hi.html

Biovisions, Harvard University

True or False

Cell membranes are rigid and don’t move.

False

True or False

Cells can bring food into the cell by engulfing it.

True

True or False

Structures that help to move things in and out of the cell are

called cholesterol.

False

Due Homework

• Membrane Protein Diversity Worksheet• Page 69

Channel Protein

Carrier Protein

Cell Recognition Protein

Receptor Protein

Enzymatic Protein

Cell Membrane Cell membrane structure:• Earlier theory: Proteins are sandwiched

between two layers of phospholipid molecules.

• Problem: Since the phospholipid tails are hydrophobic this could not explain how water could travel freely through the membrane.

Earlier Theory

Fluid Mosaic Model

• Accepted theory:

• Water travels through the pores in the proteins.

• The proteins have

which accounts for their placement among the phospholipid bilayer.

• Some of the proteins and phospholipids have

attached to them. +carbohydrate chain= +carbohydrate chain=

• These carbohydrate chains function as

• A body will attack cells with the wrong markers. Example Organ rejections in transplants.

Plasma MembraneFluid Mosaic Model

Fluid Mosaic Model

• http://www.youtube.com/watch?NR=1&v=Rl5EmUQdkuI

• Fluid mosaic model of the cell membrane

Cell Membrane• Impermeable-

• Permeable-

• Semi-permeable-

Selectively Permeable

Some substances can move across the plasma membrane :

• Water• Non-charged moleculesAnd some cannot:• Charged molecules• Macromoleculeshttp://

www.youtube.com/watch?v=JBFvH2jyVvw&feature=relmfu

Or The plasma membrane

• Protein molecules are too large to fit through pores, but they can be transported

Cholesterol- a lipid which regulates fluidity because it stiffens and strengthens the membrane.

Protein- a macromolecule made up of amino acids. Has many jobs within a cell.

Phospholipid- Make up the bilayer of the plasma membrane. They have hydrophobic (water hating) tails and hydrophilic (water loving) heads. This is why the membrane is selectively permeable.

Carbohydrate chains- Sugar molecules that act as cell recognition molecules so that your body knows that cell is suppose to be there other words called a Glycocalyx.

Glycoprotein- A protein in the cell membrane with a Carbohydrate molecule attached to it.

Glycolipid- A phospholipid molecule with a Carbohydrate attached to it.

Integrin- Protein embedded in the membrane

Peripheral Protein- Protein on the inside surface of the membrane held there by the cytoskeleton.

Cell membrane

Transport

Passive TransportDoes not use chemical energyNo ATP is involved in this transport

Types of Passive Transport:•Diffusion •Osmosis•Facilitated transport

Diffusion• There is a concentration gradient• Movement is from a high concentration to

a low concentration• Molecules want to be in equilibrium and

distribution of these molecules are equally spread out.

Examples: A fart will spread out throughout the room

until equally distributed around.Or When you add blue dye to water it will move

throughout the container until all the water looks blue.

Osmosis•Diffusion of water has a special name = Osmosis.

•Pressure develops when water wants to diffuse to a lower concentration called “Osmotic Pressure”.

•Just like diffusion water moves from a high concentration to a lower concentration.

Facilitated TransportThere is still a concentration gradient of molecules

moving from a high concentration to lower concentration with the help of a carrier protein:

1) Molecule enter carrier2) Molecule combines with carrier3) Carrier undergoes shape change and releases the molecule on the other side of the membrane.

Active Transport• This is how we move molecules from a low

concentration to a higher concentration.• To do this ATP is needed.1) Molecule enters carrier.2) ATP is used to change the carriers shape.3) Molecules moves across the membrane.

Exocytosis • process by which a cell directs the contents of secretory vesicles out of the cell membrane.

• This is also the way you build the plasma membrane with the right proteins. Proteins are embedded into the membrane of the ER. The membrane buds off and heads to the Golgi where it is then sent to the PM. Here the vesicle merges with the PM and becomes part of it. The proteins are also kept.

EndocytosisThe process by which cells absorb

molecules (such as proteins) by engulfing them and bringing them in the cell.

• Pinocytosis- invagination of the cell membrane to form a pocket, which then pinches off into the cell to form a vesicle filled with a large volume of extracellular fluid and molecules within it.

• Phagocytosis- cells bind and internalize matter. For example an Ameoba uses psedopods to capture food.

http://www.youtube.com/watch?v=1w10R9lv7eQ

Review:• Vocabulary to remember: active transport, carbohydrates, carrier protein,

cell membrane, channel protein, cholesterol, concentration gradient, diffusion, endocytosis, exocytosis, facilitated transport, fluid-mosaic membrane model, glycolipid, glycoprotein, hydrophilic, hydrophobic, osmosis, passive transport processes, phagocytosis, phospholipid, phospholipid bilayer, pinocytosis, protein, selectively permeable.