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BIO130 Final > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What are some animal cell-specific architectures?

A
  • extracellular matrix: specialized material outside the cell
  • Lysosome: Degradation of cellular components that are no longer needed
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2
Q

What are some plant cell-specific architectures?

A
  • Cell wall: cell shape, protection against mechanical stress
  • Vacuoles (2 types):
    Degradation (like animal lysosome)
    Storage (small molecules and proteins)
  • Chloroplast: Site of photosynthesis
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3
Q

What is the cytoplasm?

A

contents of the cell outside the nucleus

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4
Q

What is the cytosol?

A

aqueous part of cytoplasm

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5
Q

What is the lumen?

A

Inside of organelles

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6
Q

What kind of cellular function occurs at the membrane?

A
  1. compartmentalization
  2. scaffold for biochemical activites
  3. selectively permeable barrier
  4. transport solutes
  5. response to external signals
  6. interaction between cells
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7
Q

What is a membrane bilayer made up of?

A
  • two layers of lipid
  • protein molecules
  • lipid molecules
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8
Q

What is the primary structural component of cellular membranes?

A

phospholipid bilayers, which consist of two layers of phospholipids with hydrophilic head groups facing outward and hydrophobic tails facing inward

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9
Q

How can proteins be restricted to specific regions in the plasma membrane?

A

tethering to the cytoskeleton, attachment to extracellular molecules, or by being confined within membrane domains like lipid rafts

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10
Q

What movements do phospholipid molecules in a lipid bilayer typically undergo?

A

Phospholipid molecules in a lipid bilayer typically undergo lateral diffusion (movement within their own monolayer), rotation around their long axis, and flexion. Flip-flop between layers is rare without assistance from enzymes like flippases

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11
Q

What would happen if all hydrocarbon tails in phospholipids were saturated? Unsaturated?

A

Saturated: the plasma membrane would be less fluid due to tighter packing.
Unsaturated: there would be more kinks in the tails leading to increased fluidity due to looser packing.

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12
Q

What would be the consequence if phospholipids had only one hydrocarbon tail instead of two?

A

the structure would be less stable and might not form a bilayer; instead, they could form micelles or other structures.

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13
Q

What kind of lipids are membranes composed of?

A

phospholipid, sterols, glycolipids

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14
Q

What are the two main parts that make up a phospholipid molecule?

A

the hydrophilic head, which includes choline, phosphate, and glycerol; and the hydrophobic tails made up of fatty acid chains

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15
Q

Why do phospholipids form bilayers when added to water?

A

due to their amphipathic nature; the hydrophilic heads interact with water while the hydrophobic tails avoid it, resulting in a double-layered structure that shields the tails from water

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16
Q

What is a liposome?

A

a closed spherical vesicle formed by phospholipids in an aqueous environment

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17
Q

Why is flip-flop movement rare without proteins?

A

it involves moving from one half of the lipid bilayer to another which is energetically unfavorable without assistance from specific proteins known as flippases or scramblases

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18
Q

How long are hydrocarbon tails?

A

14-24 carbon atoms

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19
Q

What factors influence the fluidity of the plasma membrane?

A

temperature, cholesterol content, and the types and lengths of fatty acids in phospholipids

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20
Q

How do saturated and unsaturated fatty acids affect the plasma membrane’s fluid nature?

A

Unsaturated fatty acids: create kinks in their hydrocarbon chains, preventing tight packing and enhancing fluidity.

Saturated fatty acids: lack double bonds, allowing tighter packing which reduces fluidity.

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21
Q

What is the effect of temperature on the cell membrane’s lipid bilayer?

A

High temperature: increase in lipid bilayer permeability because molecules move faster and more freely

Lower temperature: reduces movement leading to decrease in permeability

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22
Q

Can proteins move within a cell’s plasma membrane?

A

yes through interactions with cytoskeletal elements or other proteins forming specialized domains, and attachment to extracellular matrix molecules or other cells.

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23
Q

What does amphipathic mean?

A

having both hydrophilic and hydrophobic part

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24
Q

What is meant by the term “two-dimensional fluid”?

A

lateral diffusion occurring in a plane.

individual molecules can move freely within the plane but not out into three dimensions due to being part of a thin layer that constitutes cellular membranes

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25
Q

How does cholesterol affect membrane fluidity?

A

acts as a buffer for membrane fluidity

increases fluidity at low temperatures by preventing tight packing of lipids and decreases it at high temperatures by restraining phospholipid movement

Makes plasma membrane less permeable to polar molecules

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26
Q

What is cholesterol?

A

a waxy, fat-like substance that’s found in all cells of the body

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27
Q

Why is cholesterol important for cellular membranes?

A

helps maintain the integrity and fluidity of cell membranes

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28
Q

What is the primary function of scramblases?

A

to facilitate the bidirectional transfer of phospholipids between leaflets in a cell membrane

rapid flip-flop of random phospholipids from one leaflet to the other

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29
Q

How does scramblase activity differ from flippases?

A

scramblases do not require ATP and move lipids bidirectionally without specificity

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30
Q

Which lipids does scramblase flip?

A

lipids in the ER membrane

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31
Q

Where are phospholipids synthesized?

A

in the cytosolic leaflet of the ER

32
Q

What is a flippase?

A

an enzyme that plays a crucial role in maintaining the asymmetry of lipid bilayers by selectively flipping specific phospholipids from one leaflet of the membrane to the other

33
Q

How do flippases contribute to membrane asymmetry?

A

remove phosphatidylserine and phosphatidylethanolamine from the noncytosolic monolayer and flip them to the cytosolic side, resulting in a higher concentration of phosphatidylcholine and sphingomyelin in the noncytosolic monolayer, thus creating membrane asymmetry

34
Q

What is the mechanism of action for flippases?

A

utilize ATP hydrolysis as an energy source to transport lipids across membranes against their concentration gradient, ensuring selective flipping of specific phospholipids

35
Q

Why is it important for certain lipids like phosphatidylserine and phosphatidylethanolamine to be concentrated on the cytosolic side?

A

essential for various cellular processes such as cell signaling, apoptosis, blood clotting, and vesicle trafficking

36
Q

How are flippase activities regulated within cells?

A

through post-translational modifications or interactions with regulatory proteins that modulate their localization or enzymatic activity

37
Q

What diseases are associated with defects in flipping activity?

A

neurodegenerative disorders, liver diseases, blood clotting disorders, and cancer

38
Q

What kind of lipids does flippase flip?

A

Lipids in the Golgi

39
Q

What are glycolipids and where are they found?

A
  • molecules composed of a lipid and a carbohydrate (sugars)
  • found in the plasma membrane of cells, where their sugar side chains face the extracellular space
40
Q

What role do glycoproteins play in the cell membrane?

A

cell protection, adhesion, and forming blood group antigens. They have oligosaccharide chains covalently attached to them which extend out from the cell surface.

41
Q

How do glycolipids contribute to cell recognition?

A

carbohydrate portion of glycolipids can participate in cell recognition processes by interacting with specific molecules on other cells or pathogens, aiding in immune responses and cellular communication

42
Q

How do glycoproteins and glycolipids contribute to the cell?

A

they protect the membrane from harsh environments

43
Q

What are the main types of membrane proteins?

A

Integral and peripheral membrane proteins

44
Q

What are the different types of integral membrane proteins?

A
  • transmembrane
  • monolayer-associated
  • lipid-linked
45
Q

What are integral membrane proteins?

A

proteins directly attached to lipid bilayer

46
Q

What are the different types of peripheral membrane proteins?

A

protein attached

47
Q

How can you extract an integral membrane protein?

A

methods using detergent to destroy the lipid bilayer

48
Q

How do integral membrane proteins insert into the membrane?

A

through transmembrane domains, which span across the entire thickness of the membrane

49
Q

Can you provide an example of an integral membrane protein?

A

glycosylphosphatidylinositol (GPI)-anchored protein, which anchors to a preformed GPI in the cell’s plasma or organelle membranes

50
Q

What is the function of integral membrane proteins?

A

transport of molecules across membranes, cell signaling, and structural support

51
Q

What are peripheral membrane proteins?

A

proteins that do not insert into the membrane
(on either face of the membrane)
- bound to other proteins
- bound to other lipids

52
Q

how are peripheral membrane proteins bound?

A

by non-covalent interactions

53
Q

How are extraction on peripheral membrane proteins done?

A

by gentle extraction methods due to non-covalent interactions, keeping the bilayer intact

54
Q

Can peripheral membrane proteins function as enzymes?

A

Yes, some can function as enzymes that catalyze reactions at the cell’s surface or within close proximity to the plasma membrane.

55
Q

What are the different types of transmembrane proteins?

A
  • single alpha-helix (single pass)
  • multiple alpha-helices (multipass)
  • beta-barrel (rolled beta-sheet)
56
Q

How are transmembrane proteins anchored to the lipid bilayer?

A

hydrophobic regions or domains that interact with the hydrophobic core of the lipid bilayer. These hydrophobic regions can be alpha helices or beta sheets

57
Q

What is an example of a beta-barrel transmembrane protein?

A

porin protein in bacteria
- ridged channel, doesn’t undergo conformational changes

58
Q

What is the primary function of transmembrane proteins?

A

They can act as transporters and channels, anchors, receptors, and enzymes

59
Q

What is an example of a transporter and channel transmembrane protein?

A

Na-K pump
- multiple alpha helices

60
Q

What is an example of an anchor transmembrane protein?

A

Integrins
- single alpha helix

61
Q

What is an example of a receptor transmembrane protein?

A

receptor kinases
- single alpha helix

62
Q

What is an example of an enzyme transmembrane protein?

A

adenylyl cyclase
- multiple alpha helices

63
Q

How are transmembrane proteins identified?

A
  • X-ray crystallography: determines 3D structure
  • Hydrophobicity plots: segments. of 20-30 hydrophobic amino acids can span the lipid bilayer as an alpha helix
64
Q

What are mono-layer membrane proteins?

A

embedded within or associated with a single layer of the lipid bilayer in a cell membrane

65
Q

What is the structure of mono-layer membrane proteins?

A

have hydrophobic regions that interact with the hydrophobic core of the lipid bilayer, while their hydrophilic regions face either the extracellular or intracellular environment

66
Q

What are lipid-link membrane proteins?

A
  • proteins located on the surface of the cell membrane that are covalently attached to lipids embedded within the cell membrane
67
Q

How are lipid-link membrane proteins attached?

A

covalent bonds

68
Q

Where are proteins with GPI anchor synthesized?

A

in the ER lumen and end up on the cell surface (non-cytosolic face)

69
Q

How do proteins with another lipid anchor form?

A

cytosolic enzymes add anchor
directs proteins to cytosolic face

70
Q

How can lateral diffusion of membrane proteins be studied?

A

Fluorescence Recovery After Photobleaching

71
Q

How does FRAP work?

A
  • proteins are fused with green fluorescence proteins or labeled with fluorescence antibodies
  • an area is bleached with a laser beam
  • fluorescence recovery = movement in the cell
72
Q

What is Single-Particle Tracking?

A

Attaching a visible marker such as a quantum dot or gold particle to individual membrane proteins and to track their movement over time in living cells

73
Q

What is purification and Reconstitution?

A
  • study-specific properties of membrane proteins in isolation from other cellular components
  • solubilized using mild detergents that form micelles around individual protein molecules or complexes thereof
    The solubilized protein can then be purified through various biochemical methods
74
Q

What is Patch-Clamp Recording?

A
  • Used for ion channels specifically
  • Analyzing their activity under different conditions by monitoring ion flow through channels in real-time at high resolution
75
Q

What is the importance of membrane asymmetry?

A

Functional specificity, membrane curvature and vesicle formation, cell signaling and interaction, maintenance of intracellular environment, and apoptosis

BIO130 Final (7 decks)

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