I. HOW SUBSTANCES GET IN & OUT OF CELLS

A. TWO MAJOR CATEGORIES OF TRANSPORT:


1. Physical processes == non-living processes
passive transport- substances move ____________________ concentration gradient;
______________________________________


a. diffusion
b. ** facilitated diffusion
c. osmosis
d. bulk flow (filtration)


2. Physiological processes == living mechanisms;
___________________________________

a. ________________________________--cell mediated transport;

substances move _______________ the concentration gradient

needs _______________________________________________________;


1.) primary active transport
2.) secondary active transport (symport & antiport)



b. ________________________________
1.) pinocytosis
2.) phagocytosis
3.) receptor-mediated endocytosis

3. ___________________________________


B. ___________________________________ == physical processes == non-living processes


1. ___________________________ -- movement of substances from area of higher concentration to area of lower conc. until equilibrium is reached.

a. Driving force = Kinetic Energy --random molecular motion.

b. All matter in the Universe is in motion (vibration); anything in motion will move in a straight line forever until it is acted on by outside force like gravity or until it collides with something.

Example:
1 drop of perfume --- molecules will move away from center; some collide; some bounce out; finally the number in the center == the number bouncing out == EQUILIBRIUM

What will happen if you place 2 different kinds of molecules into a container divided by a semipermeable membrane?


2. ___________________________________________ -- molecules too large to go through pores & insoluble in fat will combine with protein to make a chemical that is soluble in fat & will diffuse to the other side of membrane from greater concentration to lesser concentration. (no energy needed)
a. Molecule combines with protein (a carrier molecule)
b. Now chemical is soluble in lipids, moves through & is released.

3. _________________________ -- diffusion of water molecules through semipermeable membrane from an area of higher concentration of water to an area of lower concentration of water.

Example 1:

                           5% NaCl                           7% NaCL (diffusion)
                          95% H₂O                          93% H₂O (osmosis)

H₂O movea from area of higher concentration to area of lower concentration of H₂O by osmosis.
NaCl will go in opposite direction by diffusion.
Example 2:
H₂O on 1 side of membrane; 50% glucose on other side; membrane NOT permeable to sugar





Water will move to side where water is less concentrated
A NONdiffusable solute particle is on one side --- this creates an osmotic pressure that acts to "pull" water in. The greater the concentration of solute, the greater the OSMOTIC PRESSURE.

Example 3:
red blood cells placed in 3 different solutions:

isotonic solution                         hypertonic solution                         hypotonic solution
cells stay the same                         crenation occurs                         hemolysis occurs


4. Bulk Flow == filtration-- small molecules forced through membranes by hydrostatic pressure or air pressure; large molecules left behind.


Example: occurs in kidneys, lungs and blood vessel walls

C. ___________________________________________--needs energy, enzymes, & a carrier


1. ___________________________________ -- goes _____________________ gradient;


a.) needs specific ________________________ ( protein) that binds with the molecule

b.) binding causes ___________________________________________ from ATP

c.) this ______________________ is used to change the shape of the carrier protein
d.) the protein acts as an enzyme. Cells use energy from ATP to change the shape of
the carrier protein. One of the most important primary active transport mechanisms
is the Na⁺ K⁺ Pump. Most pumps pumps 3 Na⁺ out of cell and 2 K⁺ into cell.


2. ___________________________________________

a.) __________________ (cotransport) -- 2 substances (1 of which is Na⁺) move

_______________ across a membrane. Both Na⁺ and the other substance are moving down the concentration gradient from an area of greater concentration to an area of lesser concentration.
b.) ______________________ (countertransport) -- Na⁺ moves down a concentration
gradient, while another substance moves in the opposite direction against
its concentration gradient.


D. __________________________________________ -- involves small pieces of plasma membrane pinching off to take substances into or out of cell.

1. ____________________________________ -- phag (to eat) cyt (cell) osis (process)
---- process of cell eating
cell sends out pseudopods (false feet) that surround bacteria, viruses, or old red blood cells and pull them into the cell to be destroyed by lysosomes. Reverse phagocytosis can occur ===> cell gets rid of bacteria, solids and hormones.

Example: Golgi body pinches off small vesicles which migrate to the membrane edge and are "spit" out of the cell.
draw:




2. ______________________________ -- pino (to drink) cyt (cell) osis (process of)
-- process of cell drinking:
a.) indentation forms because of changes in sol-gel state of membrane
b.) fluid pours in
c.) membranes touch & break off, forming vesicle

Draw an example of pinocytosis.







3. _____________________________________________

a.) protein molecules ________________________________ the membrane of the cell

b.) these proteins serve as _______________________________ sites
c.) only certain molecules can bind to the receptor
d.) this binding will stimulate the cell membrane to indent
e.) a vesicle forms & travels to the lysosome
f.) lysozyme enzymes digest the vesicle & release the molecule. Why is this receptor mediated endocytosis important? Allows the cell to injest specific substances, even if in low concentration (hormones).

E. FACTORS THAT SPEED UP OR SLOW DOWN DIFFUSION & OSMOSIS

1. The _________________________ the gradient, the ________________________ the rate of diffusion (how long it takes to reach equilibrium)

2. An ______ in temperature ===> an _____ in rate of diffusion

3. The _________________ the size (not wt) of the molecule, the faster the rate of diffusion. (the smaller the particle the faster its molecular motion)

4. An _____ in weight =====> a _______ in the rate of diffusion.
(The greater the wt., the slower the rate of diffusion .)

5. The larger the total surface area through which diffusion can occur, the faster the rate

Draw an example of each of these factors. Refer to lab experiments.

Consists of:       interphase            mitosis             cytoplasmic division            differentiation

A. Interphase:
1. Duplicates membranes, ribosomes, lysosomes, peroxisomes & mitochondria
2. Divided into:
G1 (structures duplicated)             S phase (DNA replicates)             G2 (structures duplicate)

B. Mitosis: 2 steps
1. Division of nuclear contents
2. Division of the cytoplasm (cytokinesis)

C. Study chart 3.4 on page 92.
D. Notice that in the 3^rd to 8^th week of development of the fertilized human egg, the cells begin to specialize. They develop different structures and begin to function in different ways. See p. 34

E. Why do cells stop dividing & die? See page 99.

a. Learn the parts of the cell & their functions.

b. Notice that lysosomes digest worn out cell parts; while peroxisomes help to break down hydrogen peroxide which is toxic to human cells.

c. What is the difference between cilia, flagella, microvilla, microfilaments & microtubules? Notice that flagella, cilia, & microvilla are extensions of the plasma membrane, while the microfilaments & microtubules are located inside the cell. The microfilaments will be covered again when we study muscle movement. Notice that they are quite small & do not propel the cell like the flagella.

Helpful Activities to do after you finish reading this chapter

1. Exercise 5 & 6 in your lab book
2. Check out the following web sites:
Web Sites on the Cell
Hole's Online Learning Center - try Test Yourself
Animal Cell Membrane Tutorial