Membranes, Transport & Communication

Demo

Macromolecules What are the 4 macromolecules?

Macromolecules-Review Carbohydrates: saccharides (sugars) and polymers-provides energy Proteins: polypeptide chain of amino acids

Lipids Lipids are made up of fatty acids containing long hydrocarbon chains attached to a hydrophilic head

Phospholipids Are Important Components of Cell Membranes A type of glyceride called a phospholipid is an important component in cell membranes Phospholipids are made up of two hydrophobic fatty acid tails bonded to a hydrophilic head consisting of a glycerol and a phosphate group

Plasma Membrane

Other Types of Lipids Lipids: diverse compounds that are insoluble in water Types of lipids: –Steroids: carbon skeleton in 4 rings –Fatty acids: organic acid and hydrocarbon tails-energy storage

Fluid Mosaic Model Described as fluid because the molecules are able to move Described as mosaic because it is made up of many different kinds of components. Roman villa and dates to the 2nd century A.D.

Fluidity of Plasma Membrane Cholesterol makes the plasma membrane more ridged and decreases its permeability to small water-soluble molecules. Without cholesterol a cell would need a cell wall (ex. Bacteria, plants are not an example of this)

Selective Permeability Selective about what crosses based on: – Size – Electrical charge – Other properties

Permeability

Types of Transport Passive Transport – Molecules transported along concentration gradient – Does not require energy Active Transport – Molecules transported against concentration gradient – Requires energy!

Concentration Gradient Difference in concentration of molecules in one area compared to another

Diffusion Small substances diffuse faster than larger substances Heat increases the rate of diffusion The greater the difference in concentration of two substances, the greater the rate of diffusion

Demo

Passive Transport Simple Diffusion – transport of small, neutral, hydrophobic molecules pass through membrane (H 2 O, CO 2, O 2 ) Facilitated Diffusion – passive transport of large, charged, hydrophilic molecules – Channel Proteins – Carrier Proteins

Passive Carrier Proteins Mediate Facilitated Diffusion Passive carrier proteins assist in the diffusion of molecules and ions from an area of higher concentration to an area of lower concentration

Osmosis Maintaining a proper water balance is vital for every cell Osmosis is a type of passive diffusion that moves water across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration Osmosis does not involve the movement of solutes

Osmoregulation Osmosis – diffusion of water across plasma membrane Osmolarity – total solute concentration Tonicity – measure of osmotic pressure caused by water movement across the plasma membrane

Tonicity

Practice: 1.If you put a cell that is 90% water into a solution that is 65% water what will happen to the cell? 1 st draw it Is the solution hypo-, hyper-, or isotonic? Remember only water is crossing the membrane. Why?

Practice: 2.If you put a cell that is 90% water into a solution that is 95% water what will happen to the cell? Is the solution hypo-, hyper-, or isotonic? 3.If you put a cell that is 90% water into a solution that is 90% water what will happen to the cell? Is the solution hypo-, hyper-, or isotonic?

Example

Quick Poll Which is hypo-, hyper-, and isotonic?

Example of Osmosis? Original Paper NO

Active Carrier Proteins Move Materials against a Concentration Gradient Active carrier proteins use ATP (cellular energy) to pump molecules across the plasma membrane against a concentration gradient

Bulk Transport Transport of large molecules – Exocytosis – Endocytosis Which direction do each go? Pinocytosis- small particles are brought into the cell Receptor-mediated Endocytosis- cells internalize molecules by the inward budding of plasma membrane. Begins by signaling from receptors specific to the molecules being internalized. Phagocytosis- internalizing solid particles (ex. Bacteria)

Cellular Connections Plasma membrane structures that interconnect adjacent cells are known as cell junctions Vertebrate animals have three types of cell junctions: – Anchoring junctions – Tight junctions – Gap junctions

Communication Exchange of information between cells – Cellular Junctions – Cells Signals

Cell Signaling Signaling Molecules- molecules that give the cell a message Target Cell- the cell receiving the message Receptors- protein of the target cell that receives the signal

Signal Transduction Pathways