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Membranes Flashcards

1
Q

What is the primary function of the plasma membrane?

A

Regulates what can enter, leave and stimulate the cell.

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2
Q

What are the polymer components of the plasma membrane?

A
  • Glycolipids
  • Integral proteins
  • Peripheral proteins
  • Glycoproteins
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3
Q

What does the prefix ‘glyco’ indicate in biological molecules?

A

Carbohydrates are covalently added to a larger lipid or protein molecule.

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4
Q

What are the main properties of biological membranes?

A
  • Barrier between internal and external environment
  • Obstructive
  • Robust
  • Fluid and flexible
  • Permeable
  • Communicative
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5
Q

True or False: The lipid bilayer obstructs the movement of most molecules and ions.

A

True

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6
Q

What type of molecules can move through the lipid bilayer?

A

Non-polar molecules that are soluble in lipids.

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7
Q

What is the approximate thickness of the lipid bilayer?

A

About 5 nm, or 50 atoms deep.

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8
Q

What percentage of most cell membranes is constituted by lipids?

A

Approximately 50%

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9
Q

What is the fluid mosaic model?

A

A model describing the structure of the plasma membrane as a mosaic of various components.

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10
Q

What are the components of a phospholipid?

A
  • Glycerol backbone
  • Two fatty acid chains
  • Phosphate group
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11
Q

What are the hydrophilic and hydrophobic parts of phospholipids?

A
  • Hydrophilic: Phosphate heads
  • Hydrophobic: Fatty acid tails
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12
Q

Fill in the blank: Phospholipids and other _______ molecules spontaneously form a lipid bilayer in water.

A

amphiphilic

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13
Q

What happens when a small tear appears in the lipid bilayer?

A

The molecules move to reseal the bilayer.

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14
Q

What is the effect of cholesterol on membrane fluidity at moderate temperatures?

A

Reduces membrane fluidity.

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15
Q

What role do sterols play in membrane fluidity?

A

They can fill gaps between phospholipids, reducing fluidity.

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16
Q

What factors affect the fluidity of biological membranes?

A
  • Lipid composition
  • Shape and size of lipid molecules
  • Temperature
  • Presence of sterols
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17
Q

What is the significance of unsaturated hydrocarbon chains in membrane fluidity?

A

They prevent close packing of lipid molecules.

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18
Q

True or False: Cholesterol maintains membrane fluidity at low temperatures.

A

True

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19
Q

What are membrane microdomains (rafts)?

A

Regions within the membrane that contain cholesterol and sequester certain molecules.

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20
Q

What types of proteins are commonly found in the plasma membrane?

A
  • Enzymes
  • Receptors
  • Transporters
  • Cell attachment proteins
  • Cell signalling proteins
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21
Q

What is the glycocalyx?

A

The protective, slimy layer formed by carbohydrates on the lipids and proteins of the membrane.

22
Q

What is the role of transmembrane proteins?

A

They pass through the membrane as α helices or rolled up β sheets.

23
Q

How can cells restrict the movement of membrane proteins?

A
  • Tethering to the cytoskeletal cortex
  • Fixation to cell wall or ECM components
  • Fixation to neighboring cell components
  • Restriction by diffusion barriers
24
Q

What is the asymmetrical distribution of membrane components?

A

The uneven distribution of phospholipids and glycolipids in the membrane.

25
What is the primary composition of biological membranes?
Phospholipids, glycolipids, and proteins intermingled in a bilayer structure.
26
What is the primary characteristic of the lipid bilayer regarding molecule permeability?
The lipid bilayer is impermeable to most polar and charged molecules.
27
What type of molecules can pass through the lipid bilayer?
Small and non-polar molecules.
28
What mediates most transport across cell membranes?
Protein transporters in the cell membranes.
29
What is a membrane potential?
Local ion imbalances occurring very close to the membrane.
30
What charge is typically found on the cytosolic side of most cells?
Negative charge.
31
What creates a proton motive force in mitochondria?
Hydrogen ion transport during the electron transport chain.
32
What two factors affect solute movement across membranes?
Membrane potential and concentration gradient.
33
What is the definition of electrochemical gradient?
The combined effect of membrane potential and concentration gradient on solute movement.
34
How do positive ions move in relation to charge?
Positive ions are attracted to negative charge.
35
What creates an action potential in nerve cells?
Local changes in charge due to sodium ion influx.
36
What are the two types of membrane transport proteins?
Transporters and channels.
37
How do transporters facilitate molecule passage?
By binding molecules specifically and undergoing conformational changes.
38
What is the function of channel proteins?
They discriminate based on charge and size, often opening or closing in response to signals.
39
What is passive transport driven by?
Diffusion, influenced by a concentration gradient.
40
What is osmosis?
The movement of water from an area of high water molecule concentration to low concentration.
41
What is a hypertonic solution?
A solution with a higher concentration of solute outside the cell, causing cells to shrivel.
42
What is an isotonic solution?
A solution with equal concentrations of solute inside and outside the cell, maintaining cell shape.
43
What happens to cells in a hypotonic solution?
Cells swell and burst due to higher solute concentration inside.
44
What is the role of aquaporins?
Facilitating the passage of water across membranes.
45
What drives active transport?
Energy from ATP to move molecules against a concentration gradient.
46
What is an example of an active transporter in animal cells?
The sodium-potassium pump (Na+/K+ pump).
47
What is the approximate percentage of ATP energy used by Na+ pumps in a cell?
~30%.
48
What is cotransport?
When active transport of a solute indirectly drives transport of other substances.
49
What are the two types of coupled transport?
* Symport: solutes move in the same direction * Antiport: solutes move in opposite directions.
50
How does the sodium-potassium pump assist in glucose transport?
It creates an electrochemical gradient that drives glucose into the cell against its concentration gradient.
51
What distinguishes different types of glucose transporters in gut cells?
Different transporters are required on the apical and basal membrane domains.
52
What is the significance of the steep electrochemical gradient in coupled transport?
It drives other molecules in the opposite direction, sometimes against their gradients.

Biology (3 decks)

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