Question

54 Wed Chapter 5 pages 1000114 and 1410144 Homework-2 5.U Insert Draw Design Layout Carrol.10.A- A Review View Reference A A Mailings E.E . . be ABCD Aabbl e Student's Signature Date 1. What are the names of the structures labeled A-E, in the diagram. Be sure to indicate which letter is which structure. ED 2. What are the 4 types of cellular transport across the plasma membrane. Define each 3. Fill in the following table.

Answer 1

1. A) Collagen Fibre

B) Glycolipid

C) Cytoskeletal Filament

D) Integral Protein

E) Cholesterol

2. Passive Transport

Simple Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration. A couple of common examples will help to illustrate this concept. Whenever a substance exists in greater concentration on one side of a semipermeable membrane, such as the plasma membrane, any substance that can move down its concentration gradient across the membrane will do so. Consider substances that can easily diffuse through the lipid bilayer of the cell membrane, such as the gases oxygen (O₂) and CO₂. O₂ generally diffuses into cells because it is more concentrated outside of them, and CO₂ typically diffuses out of cells because it is more concentrated inside of them. Neither of these examples requires any energy on the part of the cell, and therefore they use passive transport to move across the membrane.

Osmosis is the diffusion of water through a semipermeable membrane. Water can move freely across the cell membrane of all cells, either through protein channels or by slipping between the lipid tails of the membrane itself.Osmosis is the diffusion of water through a semipermeable membrane down its concentration gradient. If a membrane is permeable to water, though not to a solute, water will equalize its own concentration by diffusing to the side of lower water concentration (and thus the side of higher solute concentration).

Osmosis occurs when there is an imbalance of solutes outside of a cell versus inside the cell. The more solute a solution contains, the greater the osmotic pressure that solution will have. A solution that has a higher concentration of solutes than another solution is said to be hypertonic. Water molecules tend to diffuse into a hypertonic solution because the higher osmotic pressure pulls water. If a cell is placed in a hypertonic solution, the cells will shrivel or crenate as water leaves the cell via osmosis. In contrast, a solution that has a lower concentration of solutes than another solution is said to be hypotonic.

Facilitated diffusion is the diffusion process used for those substances that cannot cross the lipid bilayer due to their size and/or polarity. A common example of facilitated diffusion is the movement of glucose into the cell, where it is used to make ATP. Although glucose can be more concentrated outside of a cell, it cannot cross the lipid bilayer via simple diffusion because it is both large and polar. To resolve this, a specialized carrier protein called the glucose transporter will transfer glucose molecules into the cell to facilitate its inward diffusion. There are many other solutes that must undergo facilitated diffusion to move into a cell, such as amino acids, or to move out of a cell, such as wastes. Because facilitated diffusion is a passive process, it does not require energy expenditure by the cell.

Active Transport- Membrane proteins that aid in the passive transport of substances do so without the use of ATP. During active transport, ATP is required to move a substance across a membrane, often with the help of protein carriers, and usually against its concentration gradient. One of the most common types of active transport involves proteins that serve as pumps.