CELL MEMBRANE OBJ: Describe the structure and function of the cell membrane according to the fluid mosaic model

CELL MEMBRANE- STRUCTURE

Plasma Membrane/ Cell membrane A double-layered sheet called a “Lipid Bilayer” Made up of a phosphate head attached to two fatty acid tails ◦ The head interacts with water (hydrophilic) ◦ The tails do not interact with water (hydrophobic)

Plasma Membrane/ Cell membrane A double-layered sheet called a “Lipid Bilayer” Flexible, fluid-like structure Made up of a phosphate head attached to two fatty acid tails ◦ The head interacts with water (hydrophilic) ◦ The tails do not interact with water (hydrophobic)

Fluid-Mosaic Model Flexible, fluid-like structure Embedded proteins

CELL MEMBRANE- FUNCTION

Plasma Membrane/ Cell membrane Regulates what enters and leaves the cell Provides protection and support Maintains “homeostasis” for the cell through “selective permeability” ◦ Only certain things are allowed in and out of the cell

Plasma Membrane/ Cell membrane Regulates what enters and leaves the cell Provides protection and support Maintains “homeostasis” for the cell through “selective permeability” ◦ Only certain things are allowed in and out of the cell

Plasma Membrane/ Cell membrane Regulates what enters and leaves the cell Provides protection and support Maintains “homeostasis” for the cell through “selective permeability” ◦ Only certain things are allowed in and out of the cell

Plasma Membrane/ Cell membrane Regulates what enters and leaves the cell Provides protection and support Maintains “homeostasis” for the cell through “selective permeability” ◦ Only certain things are allowed in and out of the cell

Plasma Membrane

Review Gradient

Concentration Gradient High concentration (many of a substance) Low Concentration (few particles of a substance) Difference from one place to another # of sugar molecules Over space

MEMBRANE TRANSPORT OBJ: List and explain the main types of membrane transport: Passive, Active, Bulk

Background Cells live in an environment of liquid in order to survive The cell membrane must regulate the movement of dissolved substances into and out of the cell in order for the cell to continue to survive

Membrane Transport Passive No energy required Active Energy required Bulk Energy required

Membrane Transport Passive Diffusion ActiveBulk

Diffusion In a solution, the particles are constantly moving The particles move from an area of high concentration to an area of low concentration (that is diffusion)

Diffusion Once the concentration is the same throughout, the system is in equilibrium No energy required Diffusion Example

Diffusion

Why Diffuse?  Cells use diffusion in order to maintain homeostasis  Cells must regulate the movement of particles to control:  temperature  pH  blood glucose levels  water balance

Diffusion in Cells ◦ Oxygen ◦ Carbon Dioxide

Diffusion

Diffusion

OBJ: Define solution, solvent, solute, and be able to determine if a solution is hypertonic, hypotonic,, or isotonic OBJ: Calculate net diffusion or net osmosis

Why can’t we drink ocean water??

Solution, Solvent, Solute

Membrane Transport Passive Diffusion Osmosis ActiveBulk

Osmosis Diffusion of water Water is able to pass across the cell membrane very easily

Osmosis: Hypertonic ◦ If too much water moves out of a cell, it will shrivel and die

Osmosis: Isotonic If water is allowed to move in and out of the cell regularly, it is in equilibrium

Osmosis: Hypotonic  If too much water moves into a cell, it will swell and burst

Osmosis is Plant Cells

Osmosis in Action

Membrane Transport Passive Diffusion Osmosis Facilitated Diffusion ActiveBulk

Phospholipid Bilayer: Embedded Proteins There are different types of proteins in the bilayer that are responsible for letting things in and out of the cell ◦ Carrier proteins have a carbohydrate arm that pulls stuff in and out of the cell ◦ Channel proteins open a channel in the membrane for stuff to pass through as needed and then close

Phospholipid Bilayer: Embedded Proteins There are different types of proteins in the bilayer that are responsible for letting things in and out of the cell ◦ Carrier proteins have a carbohydrate arm that pulls stuff in and out of the cell ◦ Channel proteins open a channel in the membrane for stuff to pass through as needed and then close

Phospholipid Bilayer: Embedded Proteins There are different types of proteins in the bilayer that are responsible for letting things in and out of the cell ◦ Carrier proteins have a carbohydrate arm that pulls stuff in and out of the cell ◦ Channel proteins open a channel in the membrane for stuff to pass through as needed and then close

Facilitated Diffusion  This process happens when proteins in the membrane allow substances to pass through them constantly (i.e. glucose)  Passive Transport= Cell doesn’t need to use energy

Membrane Transport Passive Diffusion Osmosis Facilitated Diffusion ActiveBulk

Active Transport  This process is diffusion in reverse  movement of particles from low concentration to high concentration

Active Transport  the cell must use its own energy in order to move a substance into it  this usually requires the cell membrane to change shape in some way

Membrane Transport Passive Diffusion Osmosis Facilitated Diffusion ActiveBulk

Bulk Transport Larger molecules, solid clumps of material Requires energy Requires membrane structures

Membrane Transport Passive Diffusion Osmosis Facilitated Diffusion ActiveBulk Endocytosis

Endocytosis Taking material into the cell Types of endocytosis ◦ Phagocytosis (eating) ◦ Pinocytosis (drinking)

Phagocytosis vs. Pinocytosis

Membrane Transport Passive Diffusion Osmosis Facilitated Diffusion ActiveBulk Endocytosis Exocytosis

Exocytosis The membrane of the vesicle surrounding substance fuses with cell membrane