6. Draw, label and discuss the floating mosaic theory of a cell membrane.

Fluid Mosaic Model

The cell membrane is a fluid mosaic of proteins floating in a phospholipid bilayer.

The cell membrane is constantly being formed and broken down in living cells

FLUID MOSAIC MODEL OF CELL MEMBRANES

1. Membranes are fluid and are rather viscous , like vegetable oil.

2. The molecules of the cell membrane are always in motion, so the phospholipids are able to drift across the membrane, changing places with their neighbor.

3. Proteins, both in and on the membrane, form a mosaic, floating in amongst the phospholipids.

4. Because of this, scientists call the modern view of membrane structure the "Fluid Mosaic Model".

6. The mosaic of proteins in the cell membrane is constantly changing.

7. Define a Micelle

Micelle?

A micelle (rarely micella, plural micellae) is an aggregate of surfactant molecules dispersed in a liquid colloid.

I don't remember him talking about this but I know he did because there is a  display of a micelle in the power point.

Anyhow the only reference to it in regards to human physiology is in regard to the absorption of fat soluble vitamins and lipids in the duodenum and transporting them to the surface of the intestinal absorptive cells. See page 986 under lipids. "Micelles consist of 20 to 40 bile acid molecules aggregated with their hydrophilic side groups facing outward and their hydrophobic steroid rings facing inward."

I think the only thing he would be interested in us knowing is that it is a single layer of phospholipids in a spherical shape with the hydrophilic phosphates on the outside and the hydrophobic fatty acids facing to the center, useful in the transportation of hydrophobic matter in a hydrophillic enviorment.

8. Give 4 examples how the channels governing the movement of materials in and out of the cell are controlled.

Page 111 Table 3.3 lists the "Methods of Membranes Transport" but I think what he will be looking for are the examples of control, specifically four of them mentioned in the power points.

So on page 96 under channel proteins it lists three of these.

1. Ligand regulated gates. (A)

2. Voltage regulated gates. (C)

3. Mechanically regulated gates. (D)

4. Would appear to be Phosphorylation (B)

The process in which a phosphate ion acts

as a switch to either open or close a channel.

9. List the reasons the water content of a person decreases with age.

On power point 16?

Total body water decreases with age because             a) Decreased muscle mass.             b) Increase in body fat.

Normally water composes 75-80% of a cell.

Adipose tissue (fat) is only 10% water. (hydrophobic)

c)Kidney becomes less efficient in concentrating urine, because of

sluggish sodium conservation thus increased water loss.

10. Describe the reasons and amounts of water loss from a person each day.

Average loss a day is about 2300 mL (80 oz.)

Urine 1400 mL

Feces 100mL

Sweat 100mL

Insensible

Skin 350mL

Lungs 350mL

27. Discuss diffusion including in this discussion; concentration gradient, net diffusion, equilibrium, and type of membrane.

In simple diffusion the net movement of solute from an area of high concentration to an area of low concentration is facilitated by the innate kinetic energy of the particle. The relationship between areas of high concentration to low concentration is referred to as the concentration gradient. The steeper the gradient the more rapid the diffusion will occur and as the two areas of concentration approaches an equilibrium the rate will decline until it will stop when the concentration between the two areas reach equilibrium, except for net diffusion in which there is always some activity occurring in which solutes will transfer back and forth. A net diffusion in which there is a two-way movement will always occur even when there is a steep concentration gradient albeit a small net movement. The rate of diffusion is also influenced by other factors such as temperature, or the activity rate of the particulate. The higher the temperature the faster the activity the faster the diffusion. Molecular weight also will determine rate of diffusion with the heavier particles requiring more energy to move.

Diffusion through a membrane will also be influenced by other considerations such as the amount of membrane surface area available and its permeability.

Short answers.

3. Draw and label a golgi body.

4. Discuss endocytosis.

Endocytosis is a vesicular transport process in which matter is brought into the cell. This is accomplished in three different forms.

Phagocytosis is where the cell engulfs matter entirely. This is comparatively rare and is typified by specialized cells.

Pinocytosis is the process of all human cells in which ECF is brought into the cytoplasm when the plasma membrane concaves at the exterior surface sinking in and eventually pinching off forming a pinocytotic vesicle in the cytoplasim containing whatever ECF that was available.

Receptor-mediated endocytosis is similar to Pinocytosis but it is a process that starts with specific receptors at the cell surface that collects specific matter. As it sinks in to the membrane it is coated with a protein clathrin ( which may serve as an adressing mechinism) and is pinched off and enters the cytoplasm.