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Biology > Membranes Structure > Flashcards

Membranes Structure Flashcards

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1
Q

What is a cell membrane?

A

A lipid bilayer in which protein are embedded found in all cells that separates the interior of the cells from the outside environment.

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2
Q

What does it mean for a membrane to be selective?

A

A membrane that allows specific, small molecules and ions to be imported and exported.

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3
Q

What is the role of the cellular membrane?

A
  1. Receiving information from the environment.
  2. Import and export of small molecules
  3. Capacity for movement and expansion
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4
Q

How does the membrane receive information from the environment?

A

The cellular membrane have receptor proteins in the plasma membrane that enable the cells to receive signals from the environment.

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5
Q

What does the cellular membrane have that enable the importing and exporting of small molecules?

A

Channels and Transporter

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6
Q

Why is it important that the cellular membrane have the capacity for movement?

A

It allow the cell to grow, change shape, and move.

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7
Q

What are the main components that make up the cell membrane?

A

Protein and Lipids

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8
Q

What components of lipids make up the cellular membrane?

A

Phospholipid, Glycolipids (lipid with a carb), sterol

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9
Q

What components of protein makes up the cellular membrane

A

Integral and Peripheral proteins

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10
Q

How does the lipid bilayer being amphipathic important if the bilayer were to be in an aqueous environment?

A

It helps the bilayer assemble in water. The hydrophilic heads face water on both surfaces of the bilayer, while the hydrophobic tails are shielded from the water within the bilayer interior. This is also the most energetically favorable way to assemble.

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11
Q

Why would a phospholipid bilayer want to eliminate its free edge, forming into a spherical vesicle?

A

The bilayer wants to eliminate its free edge to minimize water contact. This is more energetically favorable because it minimizes bonding with the water.

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12
Q

What is a liposome?

A

A liposome is a closed, spherical lipid bilayer, which forms an internal cavity capable of carrying aqueous solutions.

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13
Q

How can a phospholipid move within a lipid bilayer?

A

The phospholipid may flex, rotate, or laterally diffuse (move to another location laterally). However, phospholipids do not spontaneously from one monolayer to the other.

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14
Q

What is membrane fluidity?

A

Freedom of movement of protein and lipids within the cell membrane.

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15
Q

Why is membrane fluidity important?

A
  1. Enables protein to diffuse rapidly in the plane of the bilayer to interact with one another.
  2. Enable lipids and protein to diffuse from place of insertion to cite of function
  3. It ensures that membrane molecules are distributed evenly between daughter cells when a cell divides. (lipids are distributed equally)
  4. Adaptation to temperature change
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16
Q

What are the factors that affect membrane fluidity?

A
  1. Phospholipid composition
    - inverse relationship between chain length and fluidity
    - inverse relationship between saturation and fluidity
  2. Sterol
    - inverse relationship between the concentration of cholesterol and fluidity
    cholesterol can increase fluidity if most fatty acids are saturated.
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17
Q

How does cholesterol make the bilayer more rigid?

A

With its short and rigid steroid ring structure, cholesterol can fill the spaces between neighboring phospholipid molecules left by the kinks in their unsaturated hydrocarbon tails. This makes the bilayer more rigid and less permeable.

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18
Q

Where does membrane synthesis begin?

A

Endoplasmic reticulum.

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19
Q

How does the newly made membrane get transported to the bilayer?

A

There are enzymes that deposit the newly made phospholipids exclusively in the cytosolic half of the bilayer.

20
Q

If the newly made phospholipids are added only to the cytosolic side of the bilayer, would that make the bilayer unbalance? How do the bilayer deal with the unbalance?

A

Scramblase is a protein that removes randomly selected phospholipids from one half of the bilayer and insert them in the other.

21
Q

Most cell membranes are asymmetric. But if membranes emerge from the ER with an evenly assorted set of phospholipids, where does this asymmetry arise?

A

It begins in the golgi apparatus. The golgi apparatus contains a protein called flippase. Flippase remove specific phospholipids from the side of the bilayer facing the exterior space and flip them into the monolayer that face the cytosol.

22
Q

What does it mean for a cell membrane to be asymmetric?

A

One side of bilayer can be different from the other bilayer

23
Q

How does the endoplasmic reticulum and the golgi apparatus work together?

A

The endoplasmic reticulum gives the golgi apparatus lipids and protein. The golgi apparatus used the lipids and protein to form vesicle to transport the membrane it also receives from the endoplasmic reticulum.

24
Q

How does the membrane retain its orientation when transported to the cellular membrane?

A

It is transported in vesicles produced by the golgi apparatus.

25
Q

What are the four main functions of plasma membrane protein?

A
  1. Transport molecules and ions through transporter and channels
  2. Act as anchors
  3. Detect signals with receptors
  4. Catalyze reactions with enzymes
26
Q

What are the two membrane protein that associate with a lipid bilayers?

A

Integral Protein and Peripheral Protein

27
Q

What are integral proteins?

A

Amphipathic membrane proteins that are permanently attached to the lipid bilayer. They completely penetrate the lipid bilayer, embedded in the whole membrane.

28
Q

What are peripheral proteins?

A

Proteins that are temporarily attached to the plasma membrane. They are usually attached to the integral protein or into a small portion of the lipid bilayer.

29
Q

How can integral protein be removed from the lipid bilayer?

A

Destroying membrane structure with detergent

30
Q

How can peripheral protein be removed from the lipid bilayer?

A

gentle extraction procedures that interfere with protein–protein interactions but leave the
lipid bilayer intact.

31
Q

How can a integral protein span across the lipid bilayer if there are hydrophilic side chains?

A

The hydrophilic polypeptide backbone is shielded from the hydrophobic lipid hydrocarbons by the hydrophobic region helical folding.

The interior of the helix are hydrophilic, stabilized by Hydrogen bond, and the exterior of the helix are hydrophobic.

32
Q

What can multiple amphipathic alpha helix do to span a lipid bilayer?

A

They can associate, forming a water filled pore across the lipid bilayer.

33
Q

How can multiple beta sheet work together to span a lipid bilayer?

A

The multiple beta sheets can assemble a beta barrel that spans the membrane.

34
Q

How are the amino acid side chains arranged in the beta barrel?

A

The side chain alternates between hydrophilic and hydrophobic to create a water filled interior and a hydrophobic exterior that face the bilayer core.

35
Q

What are detergents?

A

Disruptive agents that destroy the lipid bilayer by disrupting the hydrophobic associations

36
Q

How does detergent disrupt hydrophobic association?

A

Detergent molecule interact with the membrane spanning hydrophobic region of the protein and the hydrophobic tail of the phospholipids, disrupting the lipid bilayer by separating the protein from the phospholipid. The hydrophilic region of the detergent will draw the protein into the aqueous solution as protein-detergent complex. At the same time, the detergent also solubilize with the phospholipid.

37
Q

What are the properties of detergent?

A
  1. amphipathic
  2. single hydrophobic chain
  3. form micelles; spherical cluster of hydrocarbons molecules
38
Q

What does the hybrid of mouse-human cell tell us?

A

Plasma membrane protein can move laterally in the lipid bilayer.

39
Q

Why are some protein restricted to movement while others can move freely?

A

The restricted protein are restricted to membrane domain.

40
Q

What are membrane domain?

A

Regions that confine protein to localized area within the bilayer/

41
Q

What is the purpose of membrane domain?

A

Protein in the domain can become specialized.

42
Q

What is a cell cortex?

A

Framework of protein that attaches to membrane protein, restricting it, to stabilize the plasma membrane.

43
Q

What does the carbohydrate outside the plasma membrane form?

A

Glycocalyx: carbohydrate layer

44
Q

Why are cell surface coated with carbohydrate?

A
  1. Protect the cell from mechanical damage.
  2. Lubricate the cell for white blood cell to squeeze through narrow space.
  3. Cell to Cell recognition
45
Q

What is the carbohydrate layer composed of?

A

Glycoprotein- protein attached to a oligosaccharide
Proteoglycan - subunit of glycoprotein - protein with one or more long oligosaccharide
Glycolipid- lipid with attached oligosaccharide

46
Q

What are lectins?

A

Transmembrane protein that bind to a oligosaccharide side chains.

47
Q

What is lectin responsible for?

A

Lectin binding is responsible for recruitment of white blood cells to sites of infection.

Biology (20 decks)

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