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 Cell m_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=

These carbohydrate chains function as A body will attack cells with the wrong markers. Example Organ rejections in transplants.

Plasma Membrane Fluid Mosaic Model

Fluid Mosaic Model EmUQdkuI EmUQdkuI 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 molecules And some cannot: Charged molecules Macromolecules ature=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

Passive Transport Does not use chemical energy No 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 Transport There 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 carrier 2)Molecule combines with carrier 3)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.

Endocytosis The 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. 10R9lv7eQ

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.

Possible Test Questions – Describe what is meant by the fluid mosaic model of a cell membrane. – Describe the passage of materials across a membrane with no energy used. – Explain how osmosis plays a role in the maintenance of a cell. – Explain how an imbalance in water between the cell and its environment affects the cell. – Describe membrane proteins that facilitate transport of materials across the cell membrane without energy being used. – Discuss how energy requiring transport proteins move substances across the cell membrane. – Distinguish between exocytosis and endocytosis and list similarities between the two.