MCB 3020C Chapter Notes - Chapter 2: Hydrophile, Membrane Protein, Membrane Lipids

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26 Aug 2020

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A barrier that separates a cell from its external environment should be: Impermeable to much of the cell contents but: not completely impermeable. Insoluble in water to maintain the integrity of the barrier: permeable to water to allow flow of water in and out of the cell. The cellular membrane is a hydrophobic permeability barrier: consists of phospholipids, glycolipids, and membrane proteins, membranes of most organisms also contain sterols, e. g. cholesterol (animals) Membrane lipids are amphipathic: have both hydrophobic and hydrophilic regions. Amphipathic phospholipids have: a polar head, two nonpolar hydrocarbon tails. A membrane is a lipid bilayer with proteins embedded in it. Amphipathic molecules undergo hydrophobic interactions in water: the polar heads of membrane phospholipids face outward toward the aqueous environment, the hydrophobic tails are oriented inward. Lipid bilayer are: readily permeable to nonpolar molecules. Impermeable to most polar molecules: highly impermeable to all ions. Cellular constituents are mostly polar or charged: prevented from entering or leaving the cell.

Related Questions

Cholesterol is transported in the bloodstream in lipoproteinparticles. There are several classes of lipoprotein particles, butone of the most important classes is called Low-densitylipoproteins (LDL). LDL particles are composed of a single moleculeof a large protein called apolipoprotein, as well as thousands ofcholesterols molecules and phospholipids. Part of theapolipoprotein forms the surface of the particles and faces theaqueous phase, while other parts face the hydrophobic interior ofthe particle where they interact with cholesterol and thehydrophobic tails of the phospholipids. When cells need additionalcholesterol, they produce a receptor protein on the surface oftheir plasma membrane that binds to the apolipoprotein andinitiates the uptake of LDL particles into the cell via a processcalled endocytosis.

1. What is the likely reason that LDL particles are used totransport cholesterol in the blood stream?

a. Cholesterol in LDL particles easily inserts into lipidbilayers

b. Cholesterol id largely insoluble in aqueous solutions

c. Cholesterol is synthesized within LDL particles

d. LDL particles can form lipid rafts in the lipid bilayer

2. What is the most likely location of phospholipids in LDLparticles?

a. Bound to the hydrophilic domain of apolipoprotein

b. In the lipid bilayer that surrounds LDL particles

c. On the surface interacting with the aqueous environment aswell as interacting with the hydrophobic core of the particle

d. Within the hydrophobic core of the particle

3. What best describes the class of protein that apolipoproteinbelongs to?

a. Amphipathic proteins

b. Cell surface proteins

c. Membrane associated protein

d. Multipass membrane proteins

4. What kind of molecule on the surface of the cell would bemost likely to serve as a receptor for LDL particles?

a. a cholesterol binding protein

b. a glycolipid

c. a phospholipid

d. trans membrane protein

5. What conditions would be most likely to trigger increaseduptake of LDL particles by cells?

a. increased glycolipid synthesis

b. increased plasma membrane growth

c. increased protein secretion

d. increase protein synthesis

Which of the following Scientist(s) described the contemporaryâfluid- mosiacâmodel of the plasma Membrane
Davson and Nicholson
Nicholson and Danielle
Singer and Davson
Nicholson and Singer
Answer:_________________________________________________________________

________________________________________________________________________

The âfluid-mosaicâ model of the PM differ from the first proposedmodel in that:
The first model did not have cholesterol
The first model was devoid of some lipids
The first model was devoid of some proteins
The first mode was devoid of some carbohydrates
Answer:_________________________________________________________________

________________________________________________________________________

Which is most likely to be a membrane receptor protein?
A glycosylated protein containing three hydrophobic regions
A glycosylated protein devoid of hydrophobic regions
A protein containing hydrophobic regions but devoid of sugars
A glycosylated protein devoid of hydrophilic regions
Answer:_________________________________________________________________

________________________________________________________________________

Which secondary structures of proteins are formed within thePM?
Alpha-pleated sheets
Beta-pleated sheets
Alpha-helicies
Beta-helicies
Answer:_________________________________________________________________

________________________________________________________________________

Intergal proteins project
entirely outside of the bilayer on the extracellular surface
entirely through the membrane having N- and C- terminusexposed.
entirely outside of the bilayer on the cytoplasmic surface
outside bilayer but covalently linked to lipids withinmembrane
Answer:_________________________________________________________________

________________________________________________________________________

Which is the driving force which maintains the lipid bilayer?
Van der waals forces
Hydrophobic interactions
Hydrophilic interactions
Ionic interactions
Answer:_________________________________________________________________

________________________________________________________________________

What affect do lipids with double bonds in their nonpolar tailshave on the integrity of the PM?
They increase the fluidity of the PM
They decrease the fluidity of the PM
They allow more lipids to pack tighter in the membrane
They cause the membrane to become less stable
Answer:_________________________________________________________________

________________________________________________________________________

As the fluidity of the PM increases, what happens to theentropy?
increases
decreases
stays the same
none of the above
Answer:_________________________________________________________________

________________________________________________________________________

The consistency of membranes at various temperatures can beunderstood using the Margarine and Butter analogy. Butter containslonger saturated chains of fat derived from animals while Margarinecontains short polyunsaturated fats derived from corn oil. Whentaken directly from the refrigerator, Margarine can be spread withease while the Butter does not. What conclusion should you drawregarding how the composition of membrane lipid regulate thefluidity of the PM?
Longer chains exhibit more double bonds and increases contact oflipids
Longer chain exhibit fewer double bonds and increases contact oflipids
Shorter chains exhibit more double bonds and increases contact oflipids
Shorter chains exhibit more double bonds and increases contact oflipids
Answer:_________________________________________________________________

_____________________________________________________________________
Which PM lipid covalently anchors proteins?
Phosphoglycerides
Sphingolipids
Cholesterol
Triglycerides
Answer:_________________________________________________________________

________________________________________________________________________

Which PM lipid is the least amphipathic?
Phosphoglycerides
Sphingolipids
Cholesterol
Triglycerides
Answer:_________________________________________________________________

________________________________________________________________________

Which of the following is not a function of the PM?
Signal Transduction
Energy Transduction
Regulates which molecules enters and exits cell
Site of Biochemical events such as production ofmacromolecules
Answer:_________________________________________________________________

________________________________________________________________________

Which two PM phospholipids have negative charges?
Phosphatidylcholine and Phosphatidylethanolamine
Phosphatidylethanolamine and Phosphatidylserine
Phosphatidylinositol and Phosphatidylserine
Phosphatidylserine and Phosphatidylcholine
Answer:_________________________________________________________________

________________________________________________________________________

Which PM lipid is the only true glycolipid?
Phosphatidylcholine
Phosphatidylethanolamine
Sphingolipid
d. Cholesterol
Answer:_________________________________________________________________

________________________________________________________________________

Which is NOT a function of the Plasma Membrane
It serves as a barrier allowing all molecules to enter cell
It serves as a site for energy and signal transductions
It is composed of lipids, proteins, and carbohydrates
It compartmentalizes the cells
Answer:_________________________________________________________________

________________________________________________________________________

Cholesterol, which is not present in bacteria, controls the PMfluidity of animal cells. Which is the CORRECT orientation of thehydroxyl group of the four-member ring of cholesterol in thePM.
The hydroxyl group is oriented inside the membrane
The hydroxyl group is oriented toward the cytoplasm
The hydroxyl group is oriented toward other cholesterolmolecules
The hydroxyl group is oriented toward the membrane surface
Answer:_________________________________________________________________

_____________________________________________________________________
PM carbohydrates are oriented:
Inside the membrane
Toward the cytoplasm
Toward other carbohydrate molecules
Away from the cytoplasm and inside organelles
Answer:_________________________________________________________________

________________________________________________________________________

Sugars constituents various on red blood cells depending on bloodtype, why would giving someone the wrong blood type be fatal?
Blood groups differ in the levels of hemoglobin they carry
The body would view the sugars as antigens and form antibodiesagainst them.
Because of the incompatible sugar arrangement, the blood would notflow to the heart properly.
The foreign sugar sequences will attack to the sugar sequences onnormal cells.
Answer:_________________________________________________________________

________________________________________________________________________

NaCl most likely get into cells by which of the followingmethods?
Diffusion
Facilitated Transport
Osmosis
Active Transport
Answer:_________________________________________________________________

________________________________________________________________________

Sufferers of type II diabetes (adult onset) have normal insulinlevels but no target cell response due to deficiency in receptorsfor insulin. Which type of transport is missing?
Diffusion
Facilitated Transport
Osmosis
Active Transport
Answer:_________________________________________________________________

________________________________________________________________________

The movement of molecules against a gradient refers to which typeof transport?
Diffusion
Facilitated Transport
Osmosis
Active Transport
Answer:_________________________________________________________________

________________________________________________________________________

Which is the correct exchange of sodium and potassium in the Na/Kpump of cells?
three sodium for three potassium
two sodium for three potassium
three sodium for two potassium
two sodium for one potassium
Answer:_________________________________________________________________

________________________________________________________________________

This type of transport is important to cells because they receivetheir oxygen and rid themselves of carbon dioxide by thismethod:
Diffusion
Facilitated Transport
Osmosis
Active Transport
Answer:_________________________________________________________________

________________________________________________________________________

Maintaining membrane fluidity is important to cells because?
Cells are able to maintain proper function at differenttemperatures
Cells can break down membranes lipids very quickly when energy isneeded
Larger molecules can pass through the membrane when fluidity isincreased
The membrane fluidity helps to maintain the positions ofglycoproteins and glycolipids
Answer:_________________________________________________________________

________________________________________________________________________

Scientists agreed that the plasma membrane was the site ofbiochemical events when peroxide was broken to produce bubblescontaining?
water
hydrogen
oxygen
carbon dioxide

Answer:_________________________________________________________________

________________________________________________________________________

A set of erythrocytes is placed in a beaker of 0.9% NaCl.Nothing appears to happen to the cells. Why?

0.9% NaCl is hypertonic to the cells.

Sodium blocks the movement of water.

0.9% NaCl is hypotonic to the cells.

0.9% NaCl is iostonic to the cells.

water has not moved at all.

Question 2

Select one answer.

Which substance would be mostlikely to pass through a lipid bilayer/plasma membrane withoutembedded proteins?

water

a steroid hormone

a large fatty acid

a large peptide hormone

a sodium ion

Question 3

Select all that apply.

Which of the following can cross the cellâs plasmamembrane without the assistance of protein transporters?Select all that apply.

large polar molecules

positively charged ions

small hydrophobic molecules

gasses

Question 4

Select one answer.

Biological Membranesare:

symmetrical.

impermeable.

static.

dynamic.

Question 5

Select one answer.

How does the selectivepermeability of the membrane help the cell.

This allows the cell to maintain the proper shape.

This allows the cell to regulate what enters and exits

This allows the cell to maintain a constant temperature.

All of these

Question 6

Select one answer.

What is the role of carbohydratesin the plasma membrane?

cellular identification

adhesion

transport materials across the membrane

help maintain fluidity

Question 7

Select one answer.

Which component of the plasmamembrane has the widest variety of functions?

sterols

carbohydrates

phospholipids

proteins

Question 8

Select one answer.

All of the following have aneffect on the fluidity of a membrane except:

interactions among fatty acids in the core of the bilayer

the cholesterol content

the ratio of saturated to unsaturated fatty acids

the presence of integral proteins in the membrane

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MCB 3020C Chapter Notes - Chapter 2: Hydrophile, Membrane Protein, Membrane Lipids

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