Bio 122 chapter 4

Identify Structure D.

phospholipid bilayer of membrane Explanation: Phospholipids can be recognized by the presence of a head and two tails.

Identify Structure A

glycoprotein Explanation: Structure is composed of both a carbohydrate and a protein.

Reviewing phospholipid structure

1. A phospholipid has a "head" made up of a glycerol molecule attached to a single phosphate group, which is attached to another small molecule. 2. Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a choline group attached to phosphate. 3. Because the phosphate group and its attachments are either charged or polar, the phospholipid head is hydrophilic, which means it has an affinity for water. 4. A phospholipid also has two "tails" made up of two fatty acid molecules, which consist of a carboxyl group with a long hydrocarbon chain attached. Explanation: Phospholipids have a hydrophilic head and a hydrophobic tail. -The hydrophilic head includes a glycerol molecule attached to a single phosphate group, which is then attached to another small molecule. The phosphate group and its attachments are either polar or charged. Water molecules are polar and therefore are attracted to these charged regions of the phospholipid head. -The hydrophobic tails are two fatty acids attached to the glycerol molecule of the head. Water molecules are not attracted to the tails because C-H bonds are relatively nonpolar and therefore do not result in charged regions in the tails.

What is the function of Structure 3?

stabilization of the phospholipids Explanation: Cholesterol helps to stabilize the structure of the plasma membrane.

Three types of solutions

Explanation: For a cell in an isotonic solution, water flows into the cell to the same extent that it flows out of the cell. If a cell is in a hypotonic solution, water flows into the cell, which causes it to swell and potentially burst. For a cell in a hypertonic solution, water flows out of the cell, which causes it to shrink.

How does phospholipid structure relate to the selective permeability of the plasma membrane?

a) hydrophobic b) can cross easily c) no transport protein required d) hydrophilic e) have difficulty crossing the hydrophobic part f) transport protein required to cross efficiently g) hydrophilic h) have difficulty crossing the hydrophobic part i) transport protein required to cross efficiently Explanation: The structure of the plasma membrane makes it selectively permeable, enabling it to regulate the transport of substances into and out of the cell. -Small, nonpolar molecules are hydrophobic, so they can easily cross the phospholipid bilayer of the plasma membrane. -Polar molecules and ions are hydrophilic, so they cannot very easily cross the hydrophobic portion of the plasma membrane (formed by the phospholipid tails). Water is an unusual molecule because, despite the fact that it is polar, it is small enough to pass directly through the hydrophobic interior of the lipid bilayer, albeit slowly. -Polar molecules and ions generally cross the plasma membrane with the help of transport proteins. For example, water crosses the bilayer rapidly via transport proteins called aquaporins.

Determining water movement in osmosis Which solution will decrease in volume?

Solution A Explanation: The water molecules actually move in both directions, but they move to a greater extent toward Solution B because it has a higher solute concentration than Solution A. The net movement of water molecules causes Solution A to decrease in volume and Solution B to increase in volume.

Further exploration of the movement of water in osmosis Which solution will increase in volume?

Solution D Explanation: The water molecules actually move in both directions, but they move to a greater extent toward Solution D because it has a higher solute concentration that Solution C. This net movement of water molecules causes Solution D to increase in volume and Solution C to decrease in volume.

The plasma membrane

a) hydrophilic b) hydrophilic c) gray up d) gray down e) hydrophilic f) hydrophobic g) hydrophilic Explanation: Phospholipids make up the main fabric of the plasma membrane. In the plasma membrane, the phospholipids are found in a bilayer. The hydrophilic heads are exposed to the aqueous environments of the cytoplasm and extracellular fluid, and the hydrophobic tails are sandwiched within, sheltered from these aqueous environments. Other elements of the plasma membrane conform to the hydrophilic and hydrophobic regions established by the phospholipids. For example, membrane proteins have hydrophilic and hydrophobic regions that are found among the hydrophilic and hydrophobic portions of the plasma membrane, respectively. Cholesterol is a hydrophobic molecule and is found among the hydrophobic tails.

Red blood cells: Crenation and hemolysis

crenation: E, D, A hemolysis: C, B Explanation: This activity shows why it is very important to use solutions that are isotonic to body fluids in intravenous solutions (IVs). If an IV solution were hypertonic to the body fluids, cells in the body would shrink. If a IV solution were hypotonic to the body fluids, cells in the body would swell.