Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Bio II > Lecture 8: The Plasma Membrane > Flashcards

Lecture 8: The Plasma Membrane Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

What are characteristics of the plasma membrane?

A
  • Boundary of the cell.
  • 10 nm width.
  • Flexible, repairable, and expandable. (but will break if expended too much)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are functions of the plasma membrane?

A

A. Provides compartment different from outside
B. Regulation of internal environment
C. Cell communication
D. Cell joining

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How are these two arrangement of phospholipids called?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is important that phospholipid bilayers can form?

A

water-filled compartments in water.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q
A
  • The phospholipid bilayer can be punctured (separated) by a small needle and will reform.
  • This is microinjection, a technique to inject a substance (e.g., DNA) into a single cell.
    Injection micropipette
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the other component as much present as phospholipids in plasma membrane?

A

membrane proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the classes of membrane proteins?

A

1) integral proteins: have domains embedded in the membrane
2) Peripheral proteins: associated with one surface of the membrane. Often interact with integral proteins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a Transmembrane protein?

A

Specific type of integral protein that completely span a membrane, with segments facing out into both its interior and exterior surfaces.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

True or false: proteins can be amphipathic. How come?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the four functions Types) of membrane proteins?

A
  1. Transport Proteins
  2. Cell Communication Proteins
  3. Enzymes
  4. Attachment proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What do transport proteins do?

A

Transport chemicals across the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What do cell communication proteins do?

A

A. Act as cell identity markers.
B. Receive a signal and relay the message.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What do enzymes do?

A

Catalyze chemical reactions of a metabolic pathway.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do attachment proteins do?

A

Attach cells to other cells or to the extracellular matrix (ECM) in tissues.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does the fluid-mosaic model suggest?

A

that components of the membrane are free to move within the membrane and that some proteins are inserted into the phospholipid bilayer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does it mean when we say that the phospholipid bilayer is “fluid”?

A
  • Individual phospholipids can rotate, move laterally throughout the lipid bilayer, and flip between layers.
  • How quickly phospholipid molecules move within and across the bilayer is a measure of its fluidity.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

The ________ of the phospholipid bilayer is directly proportional to its fluidity.

A

permeability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

By tagging individual phospholipids and following their movement, researchers have clocked average speeds of how much?

A

2 μm / second.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the other model suggesting how membrane proteins are associated with the lipid layer other than fluid-mosaic model?

A

Sandwich model

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How did we discover that the fluid-mosaic model is correct? (that proteins are embedded in the membrane). What would we have expect if the sandwich model was correct?

A

Freeze-fracture studies of the plasma membrane support the fluid mosaic model.

The “interior part” of the bilayer would be smooth rather than have complementary bumps and holes (proteins)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Do membrane proteins also move within the lipid bilayer?

if two cells with different membrane proteins are fused:
A. What would you expect if membrane proteins move?
B. Don’t move?

A

yes

A. hybrid with mixed proteins
B. Proteins would be locked in their domains and hybrid would look like half-half f the two types of proteins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is permeability of a structure?

A

its tendency to allow a given substance to pass across it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What type of permeability do membranes have?

A

selective permeability.
* Allows a cell (or internal compartment) to have an internal environment different from the external environment.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What two components determine the permeability of a membrane?

A

membrane proteins and the lipid bilayer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How does membrane proteins play a role in permeability of the membrane? For which type of molecules is it the most important?

A

they can specifically transport substances in and out of the cell

Important for larger, polar
molecules and ions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How does the lipid bilayer play a role in permeability of the membrane?

A
27
Q

What two characteristics of the molecule will determine its ability to cross a phospholipid bilayer?

A

size and polarity

28
Q

Predict whether amino acids and nucleotides will cross a phospholipid bilayer readily.

A

Generally polar and charged, so they don’t cross

29
Q

How does glucose cross the cell’s plasma membrane?

A

Through facilitated diffusion, a type of passive transport with the help of transport proteins

30
Q

Which uncharged polar molecule is the baseline to know if another one goes through the bilayer?

A

*if built in the same format

ex: steroids are bigger but pass through

31
Q

What factors influence the fluidity of the lipid bilayer?

A
  1. Temperature
  2. Type of fatty acids in the phospholipids
    A. chain length
    B. degree of saturation
  3. Cholesterol
32
Q

What are two structural properties in fatty acids that give rise to different types of fatty acids?

A

A. chain length
B. degree of saturation

33
Q

A membrane’s ____________ (directly through the phospholipid bilayer) is directly proportional to its fluidity.

A

permeability

34
Q

What is the trend between the membrane temperature and fluidity?

A
35
Q

What is the trend between the fatty acids saturation and fluidity? How come?

A
  • Double bonds in the unsaturated fatty acids cause a “kink” (bend) in the chain.
  • The kinks prevent the close packing of hydrocarbon tail and reducing hydrophobic interactions between phospholipids.
  • The lipid bilayer is more fluid when these unsaturated fatty acids are present.
36
Q

What is the trend between the fatty acids hydrocarbons tail length and fluidity?

A
37
Q

Why is cholesterol considered as a fluidity buffer when it comes to rigidity?

A
  • Overall, as cholesterol concentration in the membrane increases, membrane fluidity decreases.
    Cholesterol increases hydrophobic interactions within the membrane and favors a more rigid structure.
38
Q

Why is cholesterol considered as a fluidity buffer when it comes to changes in temperature?

A

keeps fluidity in range to support the structure and activities of the cell.

  • Behaves differently at each temperature extreme:
    A. Warmer -> Decreases fluidity and prevents membranes from
    falling apart.
    B. Colder -> Increases fluidity to prevent membranes from solidifying.
39
Q

Which organisms contain cholesterol in their cell membranes?

A

eukaryotes, especially animals

40
Q

What is ECM?

A

Extra cellular matrix

41
Q

What does the amount and composition of the ECM depend on?

A

the cell and tissue type

42
Q

What are the functions of the ECM?

A

A. Support and protection of
cells.
B. Makes strong structures for the body (e.g., bones)
C. Joins cells and organizes cells into tissues.
D. Communication between cells.

43
Q

ECM connects to cells via ___________ and so connects indirectly to the cell’s ___________ .

A

membrane proteins

cytoskeleton

44
Q

What are the components of the ECM structure?

A

In green: sugars
In purple: proteins

45
Q

What are the most common components of ECM?

Fibers:

Gel:

A
46
Q

How is this extracellular structure similar to the cell wall of a plant cell?

A
47
Q

How do cells connect to make certain tissues in multicellular organisms?

A
  • Neighboring cells can directly connect to each other to form certain tissues

*Specific connections made between specific membrane proteins (and the cytoskeleton).

48
Q

What are the two specific types of junctions that form epithelial tissues?

A

A. Tight junctions (Occlusion junctions)
B. Desmosomes (Anchoring junctions)

49
Q

What are epithelial tissues? What are the functions?

A

Epithelial tissues are characterized by tightly packed cells that form continuous sheets, covering the body surfaces, lining internal organs, and composing glands.

These tissues serve various functions, including protection, absorption, secretion, and sensation.

50
Q

What is the difference between tight junctions and desmosomes?

A
51
Q

In what type of tissues desmosomes the most important?

A

epithelia and muscle tissues

52
Q

How do plant cells attach to each other?

A

via their cell walls

53
Q

What are the three layers deposited by plants cells to attach together?

A

A. Primary cell wall
B. Secondary cell wall
C. Middle lamella
* Secondary cell wall mature in specialized cells and varies in composition.
Øe.g., lignin in wood

54
Q

What are gap junctions versus plasmodesmata?

A

both are: junctions connecting the cytoplasms of cells and allow them to exchange substances and to communicate and coordinate processes in organs.

  • Gap junctions: are channels (formed by proteins) that connect animal cells.
  • Plasmodesmata: are channels (formed by breaks in the cell wall) that connect
    plant cells.
55
Q
A
56
Q

What are leaflets?

A

the inside and outside faces of membranes

57
Q

What are the inside leaflets of membranes called?

A

cytoplasmic leaflets

58
Q

What are the outside leaflets of membranes called?

A

extracellular leaflets

59
Q

By what is the plasma membrane built in eukaryotic cells?

A

endomembrane system

60
Q

When is the asymmetrical distribution of lipids and proteins (and associated carbohydrates) in the plasma membrane determined?

A

when the membrane is built by the ER and Golgi apparatus.

61
Q

How can membranes of many species adapt to specific environmental conditions?

A

*Variations in the lipid composition of the cell membranes

*Ability to change (acclimation) the lipid composition of the cell membranes in response to temperature changes has evolved as adaptations in organisms that live where temperatures vary in their habitat.

62
Q

What does acclimation mean?

A

ability to change depending on climat

63
Q

What membrane characteristics might you expect to see in the in the cells of fish that live in very cold water? In terms of: fatty acid saturation and fatty acid tail length?

A

Since unsaturated fats are more fluid but colder temperature decrease fluidity, they tend to have more unsaturated fatty acids

Shorter fatty acid tails are also more fluid and prevent the membranes to become overly rigid in cold temperatures (and stay functional and flexible)

64
Q

Complete this table

A

Bio II (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions