Lecture 5 Flashcards

1
Q

molecular motions are very _______

A

fast

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2
Q

What is diffusion

A
  • molecules wandering randomly in cytosol
  • large molecules diffuse slower than small ones
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3
Q

In terms of enzyme kinetics, what is velocity, Vmax, and Michaelis constant (Km)?

A
  • velocity: rate of reaction
  • Vmax: the maximum rate of reaction for an enzyme. How quickly it can catalyze a reaction when fully saturated with substrate
  • Km: concentration of substrate at which enzyme is at 1/2Vmax
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4
Q

Why is a double-reciprocal plot made?

A
  • because we can calculate Vmax more precisely
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5
Q

Give 2 reasons why enzyme inhibitors are important

A
  • important for pharmaceutical agents
  • major method used by cells to regulate gene expression (ex. feedback inhibition)
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6
Q

What is competitive inhibition? and what effect does it have on Km and Vmax? Why?

A
  • competitive inhibitors compete with the substrate to bind to the active site
  • This increase Km, but not Vmax because we can add more substrate until it outcompetes the inhibitor
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7
Q

What are activated carriers? Give some examples.

A
  • small organic molecules that store energy or chemical groups in an easily exchangeable form
  • ATP, NADH, NADPH
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8
Q

How is energy captured?

A
  • energy is captured by using coupled reactions:
  • energetically favoured reactions are used to drive energetically unfavoured reactions
  • cells have an elaborate system to capture energy from food (glycolysis, beta oxidation of fatty acids)
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9
Q

ATP

A
  • stands for adenosine 5’ triphosphate
  • most widely used activated carrier
  • is the energy currency of the cell
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10
Q

How is ATP synthesized?

A
  • synthesized in a phosphorylation reaction when a phosphate group is added to ADP
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11
Q

How is ATP used to do work?

A
  • ATP is used to generate a high energy intermediate by phosphorylating a reactant
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12
Q

Compare and contrast NADH and NADPH.

A
  • Both are carriers of 2 high energy electrons and proton H+ (forming a hydride ions, H-)
  • the differing phosphate group does no affect on the electron transfer properties of NADH vs. NADPH
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13
Q

Why is the distinction of differing phosphate group of NADH vs NADPH important

A
  • because it gives each a distinct shape and allows the binding of different sets of enzymes
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14
Q

What types of reactions are NADH and NADPH involved in?

A

NADH: primarily involved in catabolic reaction that generate ATP, ratio of NAD+ to NADH is high

NADPH: primarily involved in anabolic reaction, ratio of NAD+ to NADPH is low

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15
Q

Why do we divide the functions between NADH and NADPH

A
  • because anabolic and catabolic reactions need to be regulated independently
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16
Q

Give some examples of NADH function.

A
  • NAD+ is reduced to NADH during the citric acid cycle
  • electrons from NADH are passed down the electron transport chain to generate ATP
17
Q

Give some examples of NADPH function.

A
  • biosynthesis of fatty acids
  • biosynthesis of cholesterol
18
Q

When are activated carriers usually generated?

A
  • they are usually generated in reactions coupled to ATP hydrolysis
19
Q

What is required to syntheses biological polymer

A
  • an input of energy
20
Q

Describe an alternative route for ATP hydrolysis

A
  • in some reaction when ATP is hydrolyzed, AMP and pyrophosphate (PPi) is released
  • PPi is further hydrolyzed into two molecules of phosphate
  • this results in larger change in free energy