Chapter 7.3Exchanging Materials with the Environment

http://learn.genetics.utah.edu/content/begin/cells/scale/

http://www.youtube.com/watch?v=Qqsf_UJcfBc

I. General Function

A. The structure of a cell (plasma) membrane determines its function.

B. Nutrients must go in: Water, Sugar, Amino acids, oxygen, CO2 in autotrophs, and Ions (such as Na+, K+, Mg+2, Ca+2, H+)

C. Wastes must go out: CO2 , nitrogengous wastes (from the digestions of proteins)

I. General Structure

A. Cell membrane = Layer of phospholipids, proteins, and cholesterol.

1. Fluid Mosaic Model: phospholipids, lipid rafts, proteins are in constant motion.

2. Membrane is selectively permeable = semipermeable.

I. General Structure

3. Phospholipids

a. Have hydrophilic heads that point outward and hydrophobic tails that point inwards

b. Molecules that go through phospholipids:

i. small, hydrophobic (O2, CO2, N2)

ii. small polar (glycerol)

4.Protein channels are embedded.

a. Some go all the way through to transport food and wastes.

i. Large uncharged or polar molecules (amino acids, glucose, nucleotides)

ii. Ions (Na+, K+, Mg +2, Ca+2, H+)

b. Some are on outside or inside only for signaling, anchoring, receiving, cell identification, cells adhering to other cells, attachment to cytoskeleton.

i. Glycolipids and

glycoproteins attached

to some outside

proteins receive

chemical messages

from other cells.

5. Water has its

own channels

(aquaporins)

6. Cholesterol helps

the membrane

be flexible.

http://www.youtube.com/watch?v=1Uw6u0fzNsE

http://www.youtube.com/watch?v=ERTkE91ICB8&feature=related

III. Passive TransportA. Diffusion

1. The NET movement of particles from an area of high concentration to an area of low concentration. (That is, the movement of particles along the concentration gradient).

Diffusion cont’a. Does not require a membrane (think

food coloring in water).

b. Can occur in solids, liquids, and gasses.

Diffusion cont’c. Particles are in random motion, bumping

each other and spreading out. (This causes entropy to increase = The 2nd Law of

Thermodynamics: Particles move from a state of order to a state of disorder).

d. Particles reach

equilibrium, but

equal numbers

are still going

both ways.

Diffusion cont’e. Rate depends on concentration, temperature, and mass of particles.

B. Osmosis

1.The diffusion of water across a semipermeable membrane.

http://www.explorelearning.com/index.cfm?method=cResource.dspDetail&ResourceID=418

2. Tonicity: The concentration of the solution COMPARED TO the cell.

Tonicitya. Isotonic Solution: Same concentration outside

the cell as inside. Result: The cell stays normal.

i. E.g., 5% dextrose in human.

ii. Kidneys and skin help maintain balance.

Tonicityb. Hypertonic Solution: The solution has

more particles compared to the cell = the cell has more water than the solution…SO… water moves out of the cell and the cell shrivels up.

What happens when you put salt on a slug?

http://www.youtube.com/watch?v=IRQLRO3dIp8&feature=fvsr

Tonicityc. Hypotonic Solution: Solutions have fewer

particles compared to the cell = solution has more water than the cell…SO…water moves into the cell and the cell swells.

i. Animal cells blow up• Freshwater protists have contractile vacuoles.

Tonicityii. Plant cells become turgid (very full of water).

C. Facilitated Diffusion

1. When proteins are too big or too charged to pass through membrane.

a. Just like diffusion, particles move with the concentration gradient; requires no energy.

b. Uses a protein channel that is specific. E.g., glucose channels.

Insulin Transport protein

Sugar

http://www.youtube.com/watch?v=s0p1ztrbXPY&NR=1

IV. Active TransportA. When cells needs to

keep particles in or out of cell in high concentration1. Takes energy (ATP) to

move them against the way they want to go…to move them against the concentration gradient.

a. 1/3 of all your energy goes to the Na+ / K+ pump of the nerves. Also important in muscles and absorption of food from gut.

b.Root cells take up nutrients from the soil by active transport…water is pulled in after them.

Active Transport Animation

Cell Membrane Videohttp://www.youtube.com/watch?v=vh5dhjXzbXc&playnext=1&list=PL441A7875C14F139D&index=20

V. Co-TransportA. The movement of one particle drives the

movement of another.

1. Example:

VI. Bulk TransportA. Endocytosis = food taken into a cell

1. Pinocytosis = “drinking” of particles2. Phagocytosis = “eating” of particles

B. Exocytosis = particles (wastes and products) taken out of a cell.

http://www.youtube.com/watch?v=4gLtk8Yc1Zc&NR=1

VII. Review of Transport• http://www.northland.cc.mn.us/biology/Biology1111/animations/active1.swf

CELL TYPES REVIEW

• http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm

VIII. When Transport Doesn’t Happen

• Potential energy is stored, like water behind

a dam)(imp in ATP production)

• Electrical potential can build up (imp in nerves)

IX. Cystic Fibrosis