Introduction to Metabolism

Question 1

Define

Metabolism Pathways

Answer 1

a series of consecutive, enzyme-catalyzed reactions producing a specific product from a specific starting metabolite.

Question 2

What are the chemical intermediates in metabolism?

Answer 2

Metabolites or metabolic intermediates

Question 3

Define

Pathway intermediates

Answer 3

Created and used up in the metabolic pathway; they are not released in the end

Question 4

Why is ATP a “high energy” molecule?

Answer 4

It is relatively unstable; it has four charges which cause electrostatic repulsion

Question 5

How much energy does it take to convert ATP to ADP?

Answer 5

-30 kJ/mol; ADP to ATP would be +30

Question 6

What nucelotides are used as electron carriers?

Answer 6

NAD+, FAD

Question 7

Why is NAD+ written with a +?

Answer 7

In its most stable state, it is positively charged.

Question 8

What is the difference between FAD and NAD+?

Answer 8

While they are both cofactors, FAD is a prosthetic group (bound tightly, part of tertiary structure) while NAD+ is a co-substrate (loosely bound, not part of tertiary structure)

Question 9

What part of the dinucleotide electron carriers enables them to undergo a reversible reduction reaction?

Answer 9

Their nitrogen base portion (Nicotinamine and flavin)

Question 10

What is the difference between a proton, a hydrogen atom, and a hydride ion?

Answer 10

• Proton
  no electrons
• Hydrogen atom
  one electron, neutral charge
• Hydride ion
  two electrons, negative charge

Question 11

What is the charge of NAD+

Answer 11

-1

Question 12

Is the phosphonahydride bond broken for energy?

Answer 12

No, not in mammalian cells

Question 13

What is NAD+ reduced to NADP+ with?

Answer 13

A hydride ion; one proton, two electrons

Question 14

What is FAD reduced to FADH2 with?

Answer 14

Two hydrogen atoms (two electrons)

Question 15

What is the difference between dinucleotides linked together via a phosphodiester bond vs phosphoanhydride?

Answer 15

Phosphoanhydride will be higher energy and more difficult to break

Question 16

What is NADP+ reduced to NADPH with?

Answer 16

a Hydride ion

Question 17

What do the cofactors (NAD+, NADP+, and FAD) need to be reduced?

Answer 17

Two electrons

Question 18

Define

Catabolism

Answer 18

the breakdown of complex molecules in living organisms to form simpler ones, together with the release of energy

Question 19

Define

Anabolism

Answer 19

the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy

Question 20

Why is metabolism called oxidative overall?

Answer 20

While the electron carriers are being reduced, the fuel molecules (which is what the process “starts” with) are being oxidized.

Question 21

For catabolism, we describe the oxidation of _________

Answer 21

the fuel molecules, and not the reduction of the cofactors

Question 22

For anabolism, we describe the reduction of _________

Answer 22

the building blocks, and not the oxidation of the cofactor

Question 23

Dietary Macromolecules (4)

Answer 23

1. Nucelic acids (nucelotides)
2. Proteins (amino acids)
3. Polysaccharides (complex carbs) (monosaccharides, simple sugars)
4. Triacylglycerol (fatty acids)

Question 24

Why are the polysaccharides and triacylglycerol the most significant fuel sources and not proteins?

Answer 24

The pathways for proteins are so varied (due to their R groups) that they are less efficient to use for energy

Question 25

Why are the polysaccharides and triacylglycerol the most significant fuel sources and not nucelic acids?

Answer 25

Because living organisms have not evolved mechanisms for utilizing nucleic acids as energy sources.

Question 26

What are the forms of fuel stores?

Answer 26

Fat and glycogen

Question 27

What is the results of catabolism from fuel molecules?

Answer 27

Building blocks + electrons (CO2, H2O, ATP)

Question 28

What happens if fuel stores are mobilized to be used as fuel molecules for catabolism?

Answer 28

The same as what happens to fuel molecules; building blocks + electrons (CO2, H2O, ATP)

Question 29

Define

Hepatocytes

Answer 29

Liver cells

Question 30

Define

Myocytes

Answer 30

Skeletal muscle cells

Question 31

Define

Adipocytes

Answer 31

Fat storage cells

Question 32

How are fatty acids stored in apidocytes?

Answer 32

As fat (triacylclycerols)

Question 33

How is cholesterol modified for storage in apidocytes?

Answer 33

Adding a fatty acid on its sterol group

Question 34

How do the chemical standard state differ from the biochemical standard state?

Answer 34

pH is 7, not 0. Also [H2O] is 55M
Other standards are the same

The standards that remain the same between the two

Question 35

Define

Standard free energy

Answer 35

Term in thermodynamics that relates to how much energy is needed or released in a reaction; for the biochemical standard state

Question 36

When will a reaction proceed forward?

Answer 36

when the associated value
of ∆ G is negative (<0).

Question 37

Does ∆G give information about the speed of a reaction?

Answer 37

No, only the direction of the reaction

Question 38

How do enzymes lower energy needed for a reaction to occur?

Answer 38

It offers a new, lower energy, transition state

Question 39

If ∆G ~ 0, what does that mean?

Answer 39

The reaction can be considered reversible or near equillibrium

Question 40

If ∆G «< 0, what does that mean?

Answer 40

Reaction is considered “irreversible” under cellular conditions

the only way for the reaction to go in the other direction is if you largely increase B (ex. A to B). This can be done in a testube but not in a cell

Question 41

What is considered a spontaneous reaction?

Answer 41

∆G < 0

Question 42

Will a reaction occur if ∆G > 0?

Answer 42

Yes, but not in the forward direction; it is still possible

Question 43

Equation for Keq

Answer 43

Question 44

What does ∆G give information on?

Answer 44

The driving force to reach equillibrium; the number after the symbol tells us the distance from reaching equillibrium (-50 is farther than -30 for a spontaneous rxn)