01:119:115 Lecture Notes - Lecture 7: Lipid Bilayer, Membrane Fluidity, Membrane Lipids

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rubysalmon273

15 Feb 2018

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Overview: life at the edge: the plasma membrane separates the living cell from its nonliving surroundings, this thin barrier, 8 nm thick, controls traffic into and out of the cell. Like all biological membranes, the plasma membrane is selectively permeable, allowing some substances to cross more easily than others. Membrane models have evolved to fit new data: models of membranes were developed long before membranes were first seen with electron microscopes in the 1950s. In 1915, membranes isolated from red blood cells were chemically analyzed and found to be composed of lipids and proteins. Membranes differ in thickness, appearance when stained, and percentage of proteins: membranes with different functions differ in chemical composition and structure. Second, measurements showed that membrane proteins are not very soluble in water: membrane proteins are amphipathic, with hydrophobic and hydrophilic regions. If membrane proteins were at the membrane surface, their hydrophobic regions would be in contact with water.

Related Questions

Explain the cell theory; know the three basic tenets of the theory.

All cells have to carry out certain functions, what do all cells have in common?

Compare/contrast an Eukaryotic vs a Prokaryotic cell type.

Understand the concept of selective toxicity. What do all effective targets of an antimicrobial agent have in common? What are some characteristics of Prokaryotic cells that can be targeted?

Explain the unity and diversity of prokaryotic cells in terms of evolutionary theories.

Describe the three basic shapes (morphologies) of bacteria.

What are the functions of the plasma membrane, how does the structure of the plasma membrane aid in carrying out these functions?

Describe the fluid mosaic model of the plasma membrane. Draw out the plasma membrane, include the phospholipid bilayer (indicating polar/hydrophilic and nonpolar/hydrophobic components) and peripheral and integral proteins. Also indicate the intracellular (cytoplasmic) and extracellular regions.

What are the functions of the components of the plasma membrane? Phospholipids, proteins?

Transport. Compare/contrast the following mechanisms of transport in terms of the types of molecules transported, with or against the concentration gradient, if any Energy input is required, if a transport molecule is involved, and if Euk and or Prok use this mechanism.

Osmosis (explain the role of aquaporins)

Diffusion

Facilitated Diffusion

Active transport (proton motive force / ATP binding cassette system)

Group translocation

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:_________________________________________________________________

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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:_________________________________________________________________

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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:_________________________________________________________________

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

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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:_________________________________________________________________

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

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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:_________________________________________________________________

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

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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:_________________________________________________________________

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

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

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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:_________________________________________________________________

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

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

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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:_________________________________________________________________

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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:_________________________________________________________________

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

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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:_________________________________________________________________

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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:_________________________________________________________________

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01:119:115 Lecture Notes - Lecture 7: Lipid Bilayer, Membrane Fluidity, Membrane Lipids

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