Chapter 7.3 Exchanging Materials with the Environment 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, CO 2 in autotrophs, and Ions (such as Na +, K +, Mg +2, Ca +2, H + ) C. Wastes must go out: CO 2, 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.Fluid 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 (O 2, CO 2, N 2 ) 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.flexible ch?v=1Uw6u0fzNsE ERTkE91ICB8&feature=related

III.Passive Transport A.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 2 nd 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 Tonicity: The concentration of the solution COMPARED TO the cell.

Tonicity a.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.

Tonicity b.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? IRQLRO3dIp8&feature=fvsr

Tonicity c.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.contractile vacuoles

Tonicity ii.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 s0p1ztrbXPY&NR=1

IV. Active Transport A. When cells needs to keep particles in or out of cell in high concentration 1. 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 Video vh5dhjXzbXc&playnext=1&list=P L441A7875C14F139D&index=20

V. Co-Transport A.The movement of one particle drives the movement of another. 1.Example:

VI.Bulk Transport A.Endocytosis = food taken into a cell 1. Pinocytosis = “drinking” of particles 2. Phagocytosis = “eating” of particles B.Exocytosis = particles (wastes and products) taken out of a cell. watch?v=4gLtk8Yc1Zc& NR=1

VII. Review of Transport

CELL TYPES REVIEW / /animations/cell_structure/cell _structure.htmhttp:// / /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