Section G: Cell Processes and Applications (Transport Across Cell Membrane)

Section G: Cell processes and applications (Transport across cell membrane)

G1.) Apply knowledge of organic molecules to explain the structure and function of the fluid-mosaic membrane model.

Fluid mosaic model of cell membrane: - the membrane is fluid-like - it has proteins throughout it - pores/channels - enzymes - cell markers - it also has cholesterol throughout it - cell membrane is mostly comprised of phospholipids - gives fluidity to cell membrane.

G2.) Explain why the cell membrane is described as “selectively permeable”

Selectively permeable: cell membrane can choose (select) what goes in or out of cells.  example of selection 1.) Non-polar = lipid can “slip” through the cell membrane as the cell membrane is made of lipids. 2.) Polar = glucose being polar needs to go through a protein channel. 3.) By size = very small particles can easily go through a protein channel. Membrane  oxygen and carbon dioxide Large molecules are kept out  bacteria and starch.

** Protein channels are specific for certain substance. ** 4.) By charge = small charged ions need to go through a channel.  Na+, Cl-

Side-note: How does water get across membrane?  Because water is polar, it needs to go through a protein channel, and because of the high amount of the protein channels for water, it can easily go back and forth across the membrane.

G3.) Compare and contrast the following: diffusion, facilitated transport, osmosis, and active transport.

4 ways to transport across the cell membrane: a.) Diffusion b.) Osmosis c.) Facilitated transport d.) Active transport

Diffusion: movement of a substance from an area of high concentration to an area of low concentration.  Carbon dioxide and oxygen can travel across cell membrane by diffusion.

Osmosis: (refers to the diffusion of water) the movement of water from an area of high concentration of water to an area of low concentration of water.

Facilitated transport: diffusion using a carrier protein in the cell membrane.  glucose ** you will need a protein carrier and it is with concentration gradient.

Concentration gradient: from high concentration to low concentration

Active transport: transport of molecules against the concentration gradient  movement of a substance from an area of low concentration to an area of high concentration using a protein channel and ENERGY!!  You need protein carrier, energy and against [ ] gradient for active transport.

G4.) Explain factors that affect the rate of diffusion across a cell membrane.

Rate of diffusion: 1.) temperature speeds up rate 2.) [ ] speeds up rate 3.) Size of molecule 4.) Viscosity of the medium  “thickness” of the solution

G5.) Describe endocytosis, including phagocytosis and pinocytosis, and contrast it with exocytosis.

Endocytosis v.s. Exocytosis - Other ways material can get in and out of cell

Endocytosis: cell eating or drinking 1.) The cell invaginates making a hollow/cove 2.) The molecules to be taken in fill the cove 3.) The cell membrane pinches off a vesicle. 4.) The vesicle can then fuse with a lysosome to be digested.

2 types: Phagocytosis Pinocytosis Cell eating Cell drinking Large molecules Small molecules.

Exocytosis: (“exo” means to leave or exit) opposite of endocytosis  golgi bodies making and releasing insulin. G6.) Predict the effects of hypertonic, isotonic, and hypotonic environments on animal cells.

[ ] of solutes are equal, so it is isotonic 20% salt solution 20%

Hypertonic = ↑ solute [ ] The solution is hypertonic to the cell. 20% salt solution 10% Hypotonic = ↓ solue [ ] Water The cell is hypotonic to the solution.

 Water will move via osmosis to the salt solution from the cell. This is called crenation shrivel, plasmolysis, shrink, wilt).

- The solution is hypotonic to cell. - The cell is hypertonic to the solution

10% salt solution 20%

 Water will move into the cell causing cell to swell (burst, lyse) or become turgid.

Osmotic pressure: the pressure of water rushing out “leaving.”

G7.) Demonstrate an understanding of the relationship and significance of surface area to volume, with reference to cell size. Less efficient More efficient -Energy may not - require less nutrient get to the nucleus - greater SA:V ratio, more nutrient availability.