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Biochemistry > Quiz Six > Flashcards

Quiz Six Flashcards

1
Q

What is passive diffusion?

A

Lipophilic molecules can pass through cell membranes because they can dissolve in the lipid bilayer
Going down a concentration gradient

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2
Q

What is facilitated diffusion?

A

Proteins assist in transport of chemical species across the membrane with the concentration gradient
Solute flows only in the thermodynamically favored direction

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3
Q

What are the two conformations that the glucose transporter has?

A

T1 state

T2 state

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4
Q

What is the T1 state of glucose transporters?

A

Glucose-binding site is exposed to the outside

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5
Q

What is the T2 state of glucose transporters?

A

Binding site is exposed to the inside

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6
Q

How many times does the glucose transporter cross the membrane in erythrocytes?

A

Crosses the membrane with 12 helical trans membrane segments (many are a-helicies)

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7
Q

What are ionophores?

A

Organic molecules that increase the permeability of membranes to ions

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8
Q

What are the two types of ionophores?

A

Carrier ionophore

Channel-forming ionophore

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9
Q

What are carrier ionophores?

A

Selectively binds ion, moves through membrane and releases ion out onto other side

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10
Q

What are channel-forming ionophores?

A

Selectively transports ions through channels or pores that transverse the bilayer

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11
Q

What is a nerve impulse?

A

Electrical signal produced by the flow of ions across the plasma membrane of a neuron along the concentration gradient

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12
Q

How are ion concentration gradients maintained?

A

Active transport

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13
Q

Where is sodium concentration higher? Inside or outside the cell?

A

Outside

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14
Q

Where is potassium concentration higher?

Inside or outside the cell?

A

Inside

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15
Q

What is resting membrane potential?

A
  • 60 mV
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16
Q

What does membrane potential reach during action potential?

A

+ 30 mV

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17
Q

What is the process of an action potential?

A
  1. Initial depolarization causes Na+ channels to open
  2. Na+ moves with its concentration gradient (outside to inside)
  3. Membrane potential reaches +30mV
  4. K+ channels open and K+ moves with concentration gradient (Inside to outside)
  5. Na+ channels close and hyperpolarization occurs (membrane potential = -60mV)
  6. K+ channels close
  7. Active transport moves Na+ and K+ against concentration gradient to restore resting membrane potential
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18
Q

What is membrane potential?

A

The charge difference between the two sides of the membrane

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19
Q

What are the key features of a voltage-gated ion channel?

A

Selectivity
Gates
Voltage sensor

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20
Q

What is the mechanism for rapid transport of the K+ channel?

A

Has four binding sites
Hydrated K+ can enter these sites, one at a time
When 2 ions occupy adjacent sites, electrostatic repulsion pushes them through the channel

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21
Q

What is the structure of voltage-gated channels?

A

Has six helices that cross the membrane
P loop is formed between S5 and S6
S4 has a positively charged side which will control if the channel is open or closed

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22
Q

What amino acids does the P-loop include?

A

TVGYG

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23
Q

What amino acids is the S4 comprised of?

A

Histidine

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24
Q

How is flow through the channel stopped?

A

Charge changes and S4 moves toward the cytoplasmic side when closed
Inactivation ball will move up and bind to the newly uncovered site
Hyperpolarization occurs to break the binding

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25
Q

What are neurons carried by in ligand gated ion channels?

A

Neurotransmitters

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26
Q

Where are aquaporins located?

A

Kidneys

Salivary and lacrimal glands

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27
Q

What are aquaporins?

A

Only allow transport of water

One subunit at a time

28
Q

How do aquaporins ensure proper transportation?

A

Uses R and H to repel ions from coming through the pore

Asparganine is present further along, prevents hydrogen jumping

29
Q

What are gap junctions?

A

Channels that function in intercellular communication

Allow small molecules and ions to pass through

30
Q

What do gap junctions use to transport ions from cell to cell?

A

Connexons

31
Q

What do gap junctions respond to?

A

Calcium concentration

pH

32
Q

What is active transport?

A

Energy input is required to drive transport

Goes against concentration gradient

33
Q

What are uniporters?

A

Transports a single molecule at a time

34
Q

What are symporters?

A

Transports two different molecules simultaneously in the same direction

35
Q

What are antiporters?

A

Transports two different molecules simultaneously in opposite directions

36
Q

What is secondary active transport?

A

Movement of a solute against its concentration gradient by coupling it to a movement of a solute with its concentration gradient

37
Q

What are the different kinds of secondary active transport?

A

Uniporter
Symporter
Antiporter

38
Q

How doe intestinal epithelium cells take up glucose?

A

Na+ drives the transport of glucose against its concentration gradient
Done using a symport

39
Q

What do inhibitors of the Na+, K+-ATPase do?

A

Inhibits the dephosphorylation of E2
Increases the intensity of heart muscle contraction
Results in an increase in intracellular Na+ concentration

40
Q

What are ABCs?

A

ATP Binding Cassette Proteins

41
Q

What is the function of ABCs?

A

Bind to different drugs once they enter the cell and then expel them from the cell
Inhibit the drugs actions

42
Q

What is the active transport that doesn’t use ATP?

A

Lactose permease

Uses H+ concentration

43
Q

What is recognition and specificity mediated by?

A

Weak chemical interactions

44
Q

What causes the stereospecificity of enzymes?

A

The chirality of L-amino acid residues

45
Q

What are cofactors?

A

Small organic molecule or metal ion that is required for the catalytic activity of an enzyme

46
Q

What are coenzymes?

A

A small organic molecule that is required for the catalytic activity of an enzyme

47
Q

What is a prosthetic group?

A

A cofactor that is premanently associated with an enzyme

48
Q

What are apoenzymes?

A

An enzyme that is inactive due to the absence of a cofactor

49
Q

What are holoenzymes?

A

A catalytically active enzyme-cofactor complex

50
Q

What are the different classifications of enzymes?

A 
Oxidoreductases
Transferases
Hydrolases
Lyases
Isomerases
Ligases
51
Q

What type of reaction is catalyzed by oxidoreductases?

A

Oxidation-reduction reactions

52
Q

What type of reaction is catalyzed by transferases?

A

Transfer of functional groups

53
Q

What type of reaction is catalyzed by hydrolases?

A

Hydrolysis reactions

54
Q

What type of reaction is catalyzed by lyases?

A

Group elimination to form double bonds

55
Q

What type of reaction is catalyzed by isomerases?

A

Isomerization

56
Q

What type of reaction is catalyzed by ligases?

A

Bond formation coupled with ATP hydrolysis

57
Q

Why is energy lower when the enzyme and substrate are bound together but entropy decreases?

A

Stronger interactions with active site compared to when surrounded with water
Solvation shell which is normally ordered gets desolvated and those molecules lose their orderedness, increasing entropy

58
Q

What are the different mechanisms of catalysis?

A

Acid-Base catalysis
Covalent catalysis
Metal ion catalysis
Proximity and orientation

59
Q

What are the two types of acid-base catalysis?

A

Specific acid-base catalysis

General acid-base catalysis

60
Q

What is specific acid-base catalysis?

A

Involves H+ or OH- that diffuses

Dependent only on pH

61
Q

What is general acid-base catalysis?

A

Involves acids and bases other than H+ or OH-
One used by enzymes
Dependent on buffer concentration and pH

62
Q

What are the ways that metal ion cofactors act as catalysts?

A

Binding to substrates to orient them properly for reaction
Mediating oxidation-reduction reactions
Electrically stabilizing or shielding negative ions

63
Q

What do transition state analogs do?

A

Resemble transition states and bind to enzyme rather than substrate

64
Q

What do proteases do?

A

Cut peptide bonds

65
Q

What are the two kinds of proteases?

A

Endoproteases - within a protein

Exoproteases - on terminal end

Biochemistry (4 decks)

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