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BIOL 1020 > Membranes > Flashcards

Membranes Flashcards

1
Q

What are 2 characteristics of the selectively permeable membrane?

A

Allows nutrient uptake and waste removal.
Allows hydrophilic molecules to pass through the membrane with ease

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2
Q

Phospholipid membranes are described as what?

A

Fluid mosaic

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3
Q

What does the ‘mosaic’ portion of the membrane refer to?

A

To the proteins floating within

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4
Q

What does the ‘fluid’ portion refer to?

A

To the proteins being able to move about in the membrane

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5
Q

Are fatty acids amphipathic?

A

Yes

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6
Q

What do the double bonds between the polar + nonpolar components do to the membrane?

A

Keeps the membrane fluid
Prevent the fatty acids from packing closely together

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7
Q

How is membrane fluidity maintained?

A

With decreasing temp.
As temp continues to decrease, the phospholipids continue to solidfy slowly.

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8
Q

In a plasma membrane, what dictates the freezing temp.

A

Phospholipids.
Saturated vs. Unsaturated fatty acids
Long chain vs. Short chain fatty acids

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9
Q

What behaves as a temp buffer in the plasma membrane allowing it to be semi-fluid at environmental conditions?

A

Cholesterol

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10
Q

What are the 2 major classes of proteins in the membrane?

A

Integral and peripheral

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11
Q

What are characteristics of integral membrane proteins?

A

Penetrate membrane interior
Involved with transporting larger and polar molecules

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12
Q

What are characteristics of peripheral membrane proteins?

A

Do not go through the membrane, they’re loosely attached

Act as enzymes

Attachment to cytoplasmic side: cytoskeleton

Attachment to the extracelkular side: extracellular matrix

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13
Q

What are the 6 primary functions of membrane proteins?

A
  1. Providing a stronger membrane network.
  2. For cell to cell recognition
  3. To form tight membrane junctions between different cells
  4. Function as enzymes
  5. Function as receptors
  6. Important for transportation
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14
Q

What are membrane carbs involved in?

A

Cellular recognition

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15
Q

What do membrane carbs do?

A

Remove foreign cells from the body

Covalently attach to lipids, membrane proteins

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16
Q

How can the attached carbs vary?

A

They vary from cell to cell

Vary from species to species

Vary from different individuals of the same species

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17
Q

Why is the bidirectional movement (in and out) of the plasma membrane important?

A

Nutrients enter and wastes exit

Important for ion regulation

Maintains selective permeability of the cell

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18
Q

What are the 2 types of transport proteins?

A

Channel and carrier proteins

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19
Q

How does the diffusion rate across the plasma membrane vary?

A

Due go size, shape and chemical nature of the material, the diffusion rate vary

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20
Q

How do channel proteins transport molecules?

A

They form a hydrophilic channel through the membrane.

Only open in response to certain stimuli: Usually electrical, chemical, mechanical

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21
Q

How do carrier proteins transport molecules?

A

Physically grab and escort the molecules through

They show a high degree of substrate specifity

Interior changes shape to allow movement of materials

22
Q

Does a passive process requires work or no?
Does this process happen spontaneously or non-spontaneously?

A

Passive process requires no work, hence it is a spontaneous process

23
Q

What’s osmosis? Is this a passive or active process?

A

It’s the movement of water across a semi-permeable membrane?
It’s a passive process

24
Q

How does the water move in osmosis?

A

From low to high concentration regions.
Always occurs regardless of the solute identity

25
Q

What’s tonicity?

A

Describes the ability of solution to cause a cell to gain or loose water.

Mainly dependent on the concentrations of solute that are unable to cross a membrane

26
Q

Match the following. (For organisms with a cell wall)

Isotonic, hypotic, hypertonic, plasmolyzed, turgid, flaccid

A

Isotonic: flaccid
Hypertonic: plasmolyzed
Hypotonic: turgid

27
Q

What’s osmoregulation?

A

Plant and animal cells gain/lose water to survive.

28
Q

Why do organisms that lack a cell wall live in isotonic environments?

A

To maintain constant internal environment which will prevent cell lysis or shriveling.

29
Q

What are contractile vacuoles?

A

Have pumps to force water out of the cell to prevent cell lysis in hypotonic environments

30
Q

What does a cell wall provide in hypotonic environments?

A

Cell wall swells in hypotonic environments but it will ONLY swell so much before it exerts a counter force called turgor pressure.

31
Q

What effect does turgor pressure have on the cell?

A

It will be more firm (turgor)

Allows mechanical support for small plants

32
Q

What’s facilitated diffusion? Is this passive or active?

A

Transport proteins facilitate the movement of polar molecules and ions across membrane

It’s passive

33
Q

What do transport proteins do to the speed of the polar molecules that move across the membrane?

A

It speeds up the movement substantially.

Transport protein: Always very specific to certain materials

34
Q

How does the shape of the carrier proteins change?

A

A molecule binds triggering rhe shape change.

Allows materials to pass down the concentration gradient

35
Q

What’s the name of the protein channel that water uses to pass through the membrane?

A

Aquaporins

36
Q

What’s active transport?

A

Uses energy to move molecules against its concentration gradient

37
Q

What’s primary and secondary active transport?

A

Primary: ATP utilization to move materials against concentration gradient

Secondary: Using another form of energy to move materials

38
Q

Are all proteins involved in active transport carrier proteins?

A

Yes

39
Q

What’s the process of active transport?

A
  1. Solute to be transported binds to a specific site on the transport protein
  2. ATP molecule transfers one of its phosphates to the transport protein
  3. The protein changes shape once ATP binds to it so the solute can be released on the other side of the membrane
  4. Phosphate detaches and the transport protein changes back to its original shape
40
Q

What are the 2 forces that drive the movement of the solute?

A

Concentration difference + charge difference

41
Q

Is the inside of the cell more positive or negative?

A

More negative

42
Q

What creates the charge separation of the cell?

A

Eletrogenic pumps
Ex: Proton pumps

43
Q

What are co-transporters?

A

They couple the movement of one material down it’s concentration gradient to the movement of another material UP its concentration gradient

44
Q

What’s bulk transport?

A

When larger molecules require entry into the cell using vesicles

45
Q

What does bulk transport include,

A

Exocytosis and endocytosis

46
Q

How does exocytosis take place?

A
  1. Transport vesicle full of the molecule to be exported buds from the golgi apparatus and move towards plasma membrane
  2. The vesicle fuses with the plasma membrane, expelling the it’s contents with it. (Larger molecules: proteins + sugars)
47
Q

What are the 3 types of endocytosis?

A

Phagocytosis, pinocytosis, receptor-mediated endocytosis

48
Q

What’s phagocytosis?

A

Cellular eating

Cell engulfs a particle by wrapping it with pseudopods.

  1. Particle is packages into a vacuole
  2. Vacuole fuses with lysosome
  3. Digestive enzymes break down vacuole contents
49
Q

What’s pinocytosis?

A

Cellular drinking
Non-specific
Droplets of fluid are taken up by tiny vesicles

50
Q

What’s receptor-mediated endocytosis?

A

Highly specific

Receptor proteins are specific for a certain molecule

Receptor proteins pick up the specific molecule and plasma membrane pinches inward forming a coated pit.

BIOL 1020 (4 decks)

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