please help bio questions?

Question

1.How are phospholipid molecules arranged within the lipid bilayer of the plasma membrane?
a.The hydrophobic lipid tails and the hydrophilic polar phosphate heads are arranged randomly.
b. The hydrophobic lipid tails are oriented toward the ECF and the ICF.
c. The hydrophobic phosphate heads are oriented toward the ECF and the ICF.
d. The hydrophilic lipid tails are oriented toward the ECF and the ICF.
e. The hydrophilic phosphate heads are oriented toward the ECF and the ICF.

2.The reason the lipid bilayer of a plasma membrane is asymmetric is that:
a.glycolipids appear only on the extracellular side of the membrane.
b. the phospholipids are randomly arranged.
c. cholesterol molecules line up on the inner surface of the membrane.
d. the phospholipids in the outer layer are larger molecules than those of the inner layer.
e. glycolipids make up the outer layer, while phospholipids make up the inner layer.

Answer 1

1. e. First things first. "Hydro" = Water. "Phillic" = love of. "Phobic" = hate or fear of. Ok, that being established, the answer is easy. Look for the statement that has a "phillic" term facing the extra and intra cellular matrice (water portion) or a "phobic" facing inward or away from the extra/intra fluid. The only one that agrees is "e"; the hydrophillic phosphate heads since they just love water, they will face the fluid of the extra and intra cellular areas.

2. a. "A" = not. Symmetric = well, symmetric (congruent,equally lined). So what makes the cell unevenly proportioned? It is the glycolipids that are ONLY on the "outside" extracellular side. They are strategically place for cellular function, but they are not alone. There are still phospholipids present to help hold the integrity of the cell.

Answer 2

The phospho heads are hydrophilic (water loving), In the outer layer of the bilayer these point out (towards the extracellular fluid (ECF). In the inner layer of the lipid bilayer these point towards the ICF, or into the cell.
The tails are hydrophobic (water hating), so the tails of the outer layer of the bilayer all point to the tails of the inner layer of the bilayer.

So the answer to the first question is:

e. The hydrophilic phosphate heads are oriented toward the ECF and the ICF.

The answer to the 2nd question is:

a.glycolipids appear only on the extracellular side of the membrane.

Answer 3

Hi....
For question number 1- The answer should be e). The fatty acid (lipid) tails are hydrophobic, meaning that they do not like to be near the intra- and extra- cellular fluid. It's like magnets with the same charge- they push away from each other, as the fatty acids do from the ICF and ECF. The phosphate heads, on the other hand, are hydrophilic, meaning that they are drawn to the fluid on the inside and outside of the cell. It looks something like this, plus whatever proteins, glycolipids, etc. you may find on the membrane:

For question number 2- The answer should be a). Glycolipids are used as markers on cells so that different chemicals and/or hormones know where to go, as well as a method of stabilizing the cell and aiding in connecting the cell to other cells in order to form tissues. Glycolipids are found on the outside of all eukaryotic cells (Eukaryotes are organisms with multiple cells and a membrane-enclosed nucleus).
Good luck!

Answer 4

ECF

oooooooooooooo <--- hydrophilic phosphate heads
|| || || || || || || || || || <---- hydrophobic lipid tails
|| || || || || || || || || ||
oooooooooooooo <----- hydrophilic phosphate heads

ICF

Therefore, hydrophilic heads are attracted to aqueous intracellular and extracellular environment, while hydrophobic lipid tails hide in the middle.

1. e
2. a

Answer 5

E/A