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MCM BCHE > Cell Membranes > Flashcards

Cell Membranes Flashcards

1
Q

The phospholipid bilayer is considered _____________, meaning it has both hydrophobic and hydrophilic parts

A

Amphiphilic (amphipathic)

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2
Q

What are some examples of hydrophobic molecules that easily cross the lipid bilayer?

A

O2
CO2
N2
Steroids

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3
Q

What are some examples of small, uncharged polar molecules that are able to cross the lipid bilayer?

A

H2O
Glycerol
Urea
Ethanol

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4
Q

Describe the most abundant type of membrane lipid

A

Phospholipids = most abundant

Hydrophilic head with phosphate group

Hydrophobic tails with fatty acids

Backbone made up of glycerophospholipids or sphingolipids

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5
Q

What 3 membrane lipids are classified as being a part of the OUTER sheet? i.e., facing the EC environment

A

Phosphatidylcholine
Sphingomyelin
Glycolipids

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6
Q

What 3 membrane lipids are classified as being part of the INNER sheet? i.e., facing the IC environment

A

Phosphatidylinositol
Phosphatidylserine
Phosphatidylethanolamine

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7
Q

Which of the following is almost exclusively found in the inner sheet of a lipid bilayer, and its presence in the outer sheet is a marker for cellular apoptosis?

A. Phosphatidylserine
B. Phosphatidylcholine
C. Phosphatidylethanolamine
D. Phosphatidylinositol

A

A. Phosphatidylserine

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8
Q

What type of lipid found in the bilayer is considered similar to sphingolipids because it contains a sphingosine backbone, but contains a carb moiety rather than a phosphate group, and is only found in the OUTER sheet of the bilayer?

A

Glycolipids

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9
Q

Sphingomyelin consists of what 3 components?

A

LC fatty acid
Phosphocholine
Sphingosine

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10
Q

Niemann-Pick disease is characterized by a deficiency of what enzyme?

A

Sphingomyelinase

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11
Q

What type of lipid is classified as a steroid alcohol and is embedded within the bilayer with a hydroxyl head group and a sterol ring tail group?

A

Cholesterol

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12
Q

In Niemann-Pick disease, a deficiency in sphingomyelinase leads to accumulation of sphingomyelin in the ___________ of liver, spleen, CNS, and bone marrow leading to what characteristic symptoms?

A

Lysosomes;

Hepatosplenomegaly, mental retardation, seizures, ataxia, spasticity, “cherry red spot” in eye

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13
Q

____________ membrane proteins are embedded in the lipid bilayer and are stabilized by hydrophobic interactions. They are also likely to be _________, and act as transporters, ion channels, and receptors

A

Integral; polytopic

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14
Q

___________ membrane proteins are loosely bound via electrostatic interactions; one major example is cytochrome C

A

Peripheral

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15
Q

Lipid-anchored membrane proteins are tethered to the bilayer through a __________ bond

A

Covalent

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16
Q

____________ is a carbohydrate shell on the outer bilayer sheet that plays a multifunctional role

A

Glycocalyx

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17
Q

What are the 3 primary roles of the glycocalyx?

A
  1. Protection (from mech. injury)
  2. Adhesion (stabilizes cell-cell contact)
  3. Identification (i.e., blood typing via oligosaccharide composition)
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18
Q

What system in the body relies heavily on the glycocalyx for protection?

A

The vascular system relies on the glycocalyx as a physical barrier against leakage of fluid, proteins, and lipids across the vascular wall

It modulates adhesion of inflammatory cells and platelets to the endothelial surface

Damage is associated with increased cellular permeability and edema, resulting in increased adherance of leukocytes and platelets, which may be a risk factor for clotting/increased vascular vulnerability

19
Q

RBCs have type-specific ABO and Rh ________ on their surface. __________ are present in the plasma, but whole blood is rarely given in transfusions

A

Antigens

Antibodies

20
Q

Which blood type is considered the universal donor?

A

Type O [these individuals can only accept type O blood due to AB antibodies in their PLASMA]

21
Q

Which blood type is considered the universal recipient?

A

AB, because they lack antibodies to either A or B antigens

22
Q

If a mother gives birth to her second child and the child is diagnosed with hemolytic anemia, was her first child Rh+ or Rh-?

A

Rh+

The mother is likely Rh-, but was sensitized to the Rh factor in her first pregnancy, thus developing Rh antibodies which attacked the blood cells in her subsequent pregnancy (her second child is also likely to be Rh+)

23
Q

A __________ is composed of a monolayer of amphipathic molecules, while a ___________ is a bilayer of amphipathic molecules.

A

Micelle; liposome

24
Q

Compare micelles to liposomes in terms of structure

A

Micelle = monolayer

Liposomes = bilayer

25
Q

Compare micelles to liposomes in terms of formation

A

Micelle = formed by surfactant molecules when dispersed in polar solvent

Liposome = formed by phospholipids; careful hydration of dry lipids with agitation

26
Q

Compare micelles with liposomes in terms of size

A

Micelles = small

Liposomes = large

27
Q

Compare micelles and liposomes in terms of what they transport

A

Micelles = transport hydrophobic molecules

Liposomes = transport hydrophobic molecules AND hydrophilic molecules

28
Q

Compare micelles to liposomes in terms of their source

A

Micelles = biological (used to digest lipids by increasing access to lipases)

Liposomes = artificial (used for drug delivery)

29
Q

What biological example of a micelle serves the main function of allowing digestion of dietary fats and oils?

A

Bile acids [these act as surfactants that emulsify fats + oils into micelles via colloidal suspension]

30
Q

Proteins and lipids require rotation and lateral movement for function; the nature and composition of the bilayer imparts an inherent fluidity. What 3 factors primarily affect membrane fluidity?

A

Temperature

Lipid composition (saturated fatty acids impart rigidity)

Cholesterol (intercalating molecules decrease fluidity)

31
Q

Unsaturated lipids and higher temperatures tend to __________ fluidity

A

Increase

32
Q

An increase in temperature tends to __________ unsaturated lipids

A

Decrease

[this is a compensatory mechanism to maintain a certain degree of fluidity]

33
Q

If a cell is in a stressful environment with a higher than normal temperature, would the cholesterol content of the lipid bilayer increase or decrease?

A

Increase - with the increase in temp, fluidity is increasing, so cholesterol will increase to fill any gaps being created and maintain a baseline fluidity

34
Q

At colder temperatures, cells will _________ the amount of unsaturated lipids in the cell membrane, thus lowering the _____ and preventing transition to a rigid semicrystalline state

A

Increase

Tm

35
Q

What 2 ways might a membrane become more fluid in terms of its fatty acid chains?

A
  1. Introduce points of unsaturation

2. Addition of methyl groups

36
Q

True or false: flip-flop (transbilayer translocations) between the two sheets of a lipid bilayer does not readily occur, however some lipids DO flip between layers

A

True

37
Q

___________ are protein translocators that are energy-dependent, unidirectional, and move lipids from OUTER to INNER sheet

A

Flippases

38
Q

The outer sheet of the lipid bilayer is called the __________ leaflet while the inner sheet is called the ____________ leaflet

A

Exoplasmic; cytoplasmic

39
Q

__________ are protein translocators that move lipids from INNER to OUTER sheet

A

Floppases

40
Q

One class of flippases is called _________, which are energy-independent and bidirectional - meaning they facilitate lateral diffusion in a single membrane sheet

A

Scramblase

41
Q

What clinical syndrome presents via defective platelet mechanism and blood coagulation due to prothrombin being cleaved to thrombin in the clotting cascade?

A

Scott Syndrome

42
Q

The mechanism of action involved in the vascular injury associated with Scott Syndrome is due to a defective _________ to translocate ____ from the inner leaflet to outer leaflet.

___________ acts as a catalyst to induce the coagulation cascade, and binding sites for plasma protein complexes that convert prothrombin to thrombin.

A

Floppase; phosphatidylserine

Phosphatidylserine

43
Q

What pathological condition is a type of hemolytic anemia that is associated with elevated cholesterol in erythrocyte membranes?

A

Spur cell anemia

44
Q

In Spur Cell Anemia, elevated cholesterol in erythrocyte membranes decreases their fluidity. This leads to rigidity which causes the RBCs to lyse in the capillaries of the _________. SCA is also associated with beta-lipoproteinemia and advanced alcoholic _________.

Chronic liver disease impairs the metabolism of cholesterol by the liver, resulting in excess free cholesterol. Cholesterol binds the cell membrane, increasing the surface area, creating rough thorny projections called ______________

A

Spleen; cirrhosis

Acanthocystes

MCM BCHE (13 decks)

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