Cell Structure and Function

Nature of Membranes (other notes) Peripheral proteins are on the outer surface of the phospholipid bilayer and serve the cell as receptors by interacting w/ environmental molecules (neurotransmitters or hormones) that impacts the cell Integral proteins (AKA transmembrane proteins) provide the mechanisms for lipid-insoluble materials to pass from one side of the membrane to the other Ie: peptides, proteins etc.

Cholesterol fills the spaces between the phospholipids and helps maintain the integrity of the membrane structure Glycolipids and glycoproteins function as markers for the identification of cell types The membrane is selectively permeable

Review of Eukaryotic Cells

Biology: Cell Structure https://www.youtube.com/watch?v=urujd5nexc8

2 min break!! Whoo hoo!

Molecule Movement & Cells Passive Transport Active Transport Endocytosis (phagocytosis & pinocytosis) Exocytosis

Passive Transport No energy required Move due to gradient differences in concentration, pressure, charge Move to equalize gradient High moves toward low

Types of Passive Transport 1. Diffusion 2. Osmosis 3. Facilitated diffusion

Diffusion Molecules move to equalize concentration

Osmosis Special form of diffusion Fluid flows from lower solute concentration involves movement of water Into cell Out of cell

How Osmosis Works https://www.youtube.com/watch?v=w3_8f Srqc-I

Solution Differences & Cells solvent + solute = solution Hypotonic Solutes in cell more than outside Outside solvent will flow into cell Isotonic Solutes equal inside & out of cell Hypertonic Solutes greater outside cell Fluid will flow out of cell ***Think about hypo/hyper/isotonic in the environment/solution perspective

Live Exercise of Diffusion

Facilitated Diffusion Differentially permeable membrane Channels (are specific) help molecule or ions enter or leave the cell Channels usually are transport proteins (aquaporins facilitate the movement of water) No energy is used

Process of Facilitated Transport Protein binds with molecule Shape of protein changes Molecule moves across membrane

GIF of Facilitated Transport http://www.mrdubuque.com/uploads/2/4/5/ 0/24509062/a546a20ce24cf690bbdad8b0 65e034ee_orig.gif

Active Transport Molecular movement Requires energy (against gradient) Against the law of diffusion Example is sodium-potassium pump

Active Transport The Thyroid gland accumulates iodine ions needed to manufacture the hormone thyroxin The iodine concentration can be as much as 25x greater in the tissues of the thyroid than in blood plasma

GIF of Active Transport https://media.giphy.com/media/suhcapse Jhib6/giphy.gif

Endocytosis Movement of large material Particles Organisms Large molecules Movement is into cells

Process of Endocytosis Plasma membrane surrounds material Edges of membrane meet Membranes fuse to form vesicle

Forms of Endocytosis Phagocytosis cell eating Pinocytosis cell drinking

Exocytosis Reverse of endocytosis Cell discharges material

Exocytosis Vesicle moves to cell surface Membrane of vesicle fuses Materials expelled

SA/V ratio extension What will happen if we put an animal cell in distilled water? Water will go in because inside the cell, it is more concentrated. Therefore the cell is in a hypotonic solution. The cell s volume will increase but its SA will remain the same because the amount of surface membrane is not altered The SA/V Ratio will decrease because the volume increases faster than SA As the cell swells, the SA becomes the limiting factor to survive

A swollen cell will produce more waste substance than it can get rid of effectively or quickly enough Or it can t obtain enough essential substance (ie: Oxygen, Glucose) to function properly at the increased size state The cell has 4 solutions Dye Alter shape Alter function Dividing

For specialized cells, they cannot do any of these For unspecialized cells, changing shape and function are not viable alternatives Cell shape and function are interrelated Cell division will increase the SA/V ratio to normal level Ie: Cells involved with the growth of organisms or cell replacement do this

End Chapter 5