Cell Membrane/cell transport

7.2/7.4 Textbook

Eukaryotic or Prokaryotic Cells

Prokaryote/EukaryoteWhich one is a plant cell?

Animal Cell?

• They can be easily distinguished by their membrane-bound nucleus.

Plant or Animal cell?

Let’s keep this simpleCell (plasma) membrane

• Remember anything about the cell membrane? What’s its job?

• Lets see if we remember what it looks like!

• http://www.colorado.edu/intphys/Class/IPHY3730/image/membrane.jpg

• http://telstar.ote.cmu.edu/biology/downloads/membranes/index.html

Cell membrane

• A complex barrier of lipid molecules separating the cell from its external environment.

• These molecules can move apart to allow larger particles to move in or out of the cell.

Cell membrane

• The "selectively permeable" cell membrane controls what passes into and out of the cell.

• This allows the cell to maintain a "balance" between what is inside the cell and outside. (Homeostasis)

Whoa…Fluid Mosaic Model…

Plasma aka cell membrane: 7.2

• It’s got stuff to help it out:

• Phospholipid bilayer: two fatty chains are linked “tail to tail” so it can live in a watery environment-ie your body. (POLAR)

• But why???? Well, it allows some things in but not all because the inside of the membrane doesn’t like water (nonpolar), so the cell says what goes in and out!

Cell membrane

• It also has other stuff to help with transport: proteins open/close depending on what it’s told to do.

7.4: Cell transport: How does the stuff get through, who cares

anyway?• Its pretty important, your cells want to keep

balance, meaning keeping concentrations of things (nutrients, ions,) same on both sides of membrane.

• One way is: Diffusion (passive transport) is movement of substance (i.e. water= OSMOSIS) from high concentration to lower. That’s why if you drink of water (hydration), your cells fill up (including your bladder) . Drink a lot of water become super hydrated. Did you know you can overdose (even DIE) by drinking too much H2O?

dehydration

• You can also “dehydrate by not drinking enough water (soda, sports drinks, juice, energy drinks DO NOT COUNT)-ask me why??You get a higher concentration of a solute outside your cells because there isn’t enough water to dilute it (so there is more sugar, salt, etc outside), so your poor cells want to even that out (equilibrium) so they diffuse water out (osmosis). Not good for your cells either.

Dynamic equilibrium: all things in nature MUST reach it. • That is nice , when there is continuous

movement both in/out of cell helping to keep balance on both sides.

• So bad when cells are hypertonic: concentration of stuff outside of cell is higher than in…what happens to cell?

• And bad when they are hypotonic: concentration of stuff is less than inside cell.. What happens?

• And “just right” when they are isotonic: stuff on both sides (in/out) of cell is at equilibrium.

Cells in a hypertonic, hyptonic and isotonic environment

Active transport

• Active transport is the movement of substances AGAINST the concentration gradient which requires energy in the form of ATP

• Uses carrier proteins

Transport of Large molecules

• If stuff is TOO BIG to move through by diffusion or through a carrier protein, the cell will surround it (engulf) the substance, which is called endocytosis

• When the cell wants to secrete a substance, it expels it through exocytosis