Ch 13 Segway Lecture Flashcards Preview

BIOC 4331 > Ch 13 Segway Lecture > Flashcards

Flashcards in Ch 13 Segway Lecture Deck (55)
Loading flashcards...
1
Q

catabolism

A

breaks down food for energy and building blocks ex: glycolysis

2
Q

anabolism

A

used energy and building blocks to make the molecules used for catabolism ex: photosynthesis

3
Q

Where does the energy we consume come from and what is the general formula

A

Sun (Energy) + 6 CO2 + 6 H2O -> (C6H12O6)n + 6 O2

4
Q

What molecules do most chemoheterotrophs use for energy?

A

reduced carbon

5
Q

∆G°’

A

free energy change of reaction when all of its reactants and products are in their standard states: 25°C, 1 atm, and unit concentrations of 1M for reactants and products at a pH of 7. This never happens in biology, so a correction from ∆G°’ to actual ∆G must be made

6
Q

∆G = (in terms of ∆G°’)

A

∆G = ∆G°’ + RT ln Keq

To make ( RT ln Keq ) negative (for reaction spontenuity) increase the concentration of the reactants or remove product to drive the reaction towards Keq

7
Q

General charachteristics of metabolic pathways

A
  • Individual pathways are irreversable: don’t waste energy on reactions that will revert back
  • Catabolic and anabolic pathways must differ: for independent control of the two processes
  • Every pathway has an early committed step
  • All pathways are regualted
  • Metabolic pathways in eukaryotes occur in different areas: glycolysis in cytosol and citric acid cycle in mitochondria
8
Q

Why is the ATP to ADP conversion so energetically favourable?

A

Releif of charge repulsion between phosphate groups, resonance stabilisation of product (Pi), reionisation of ADP

9
Q

Three easy ways to oxidise

A

loss of electrons, loss of hydrogen, gain of oxygen

10
Q

Three easy ways to reduce

A

gain of electrions, gain of hydrogen, loss of oxygen

11
Q

Transfer of electrions to O2 is exergonic or endergonic and why?

A

exergonic, oxygen has a very high standard reduction potential (wants to be reduced)

12
Q

standard reduction potential

A

the affinity of a molecule to be reduced, greater is more likely to be reduced

13
Q

list the oxidation states of carbon in biomolecules and give examples of each in order from most reduced to most oxidised

A

alkane > alcohol > ketone/aldehyde > carboxcylic acid > CO2

14
Q

coenzyme

A

a low molecular weight organic compound which in cooperation with an enzyme, facilitates a reaction

coenzyme may appear to be a substrate and/or product. many coenzymes have a part of their structure that is derived from a vitamin

this is what makes vitamins a nutritional requirement, as the cell cannot biosynthesize an adequate amount for its own use

15
Q

What is the difference between the types of reactions NAD+ and NADP

A

NAD+ is reduced to NADH during many oxidative reaction of catabolism

NADPH is oxidised to NADP in anabolic pathways

16
Q

What happens to NAD+ during catabolism? What is the function of NAD+ in catabolism?

A

NAD+ is reduced to NADH during many oxidative reactions of catabolism.

NAD+ collects electrons released during catabolism.

NADH is a form of stored chemical energy: it can be oxidized in aerobic cells, this oxidation provides the energy for ADP + Pi –> ATP

17
Q

H and electrons in a cell

A

H = e- + H+
• A hydrogen ion is a proton
• Water dissociates to H+ + OH-, so there are always lots of protons around free in the cell.
• Protons can exist free in the cell (recall pH), but electrons can’t.
• To move electrons, the cell uses electron carriers like NADH and FADH2

18
Q

Where does reduced carbon factor into metabolism?

A

Reduced carbon (in carbohydrates, fats, or proteins) + O2 -> CO2 + H2O + Energy

19
Q

Where are polymers broken down?

A

Polymers are broken down in the intestine. Only monomers are absorbed.

20
Q

Where are monomers broken down?

A

Monomers are absorbed and broken down in the cells

21
Q

What happens to individual biomolecules during catabolism?

A

Individual biomolecules are broken down by unique pathways into universal molecules (like acetyl-CoA) that can “feed into” a common energy producing pathway called the TCA cycle

22
Q

exergonic reaction

A

Favorable reactions are exergonic and release free energy, represented by a negative ∆G

23
Q

endergonic reaction

A

Nonspontaneous reactions that absorb free energy and has a positive ∆G are called endergonic

24
Q

Favorable reactions are exergonic or endergonic? Is their ∆G positive or negative?

A

exergonic, -∆G

25
Q

Unfavorable reactions are exergonic or endergonic? Is their ∆G positive or negative?

A

endergonic, +∆G

26
Q

A reaction with +∆G is exergonic or endergonic? Spontaneous or nonspontaneous?

A

endergonic, nonspontaneous

27
Q

A reaction with a -∆G is exergonic or endergonic? Spontaneous or nonspontaneous?

A

exergonic, spontaneous

28
Q

What is true about a reverse reaction’s ∆G compared with the forward reaction?

A

It has the same magnitude but inverses the sign

29
Q

NAD+ structure

A

Nicotinamide adenine dinucleotide, like all dinucleotides, consists of two nucleotides joined by a pair of bridging phosphate groups. The nucleotides consist of ribose rings, one with adenine attached to the first carbon atom (the 1’ position) and the other with nicotinamide at this position. The nicotinamide moiety can be attached in two orientations to this anomeric carbon atom. Because of these two possible structures, the compound exists as two diastereomers. It is the β-nicotinamide diastereomer of NAD+ that is found in organisms. These nucleotides are joined together by a bridge of two phosphate groups through the 5’ carbons

30
Q

ln (natural log) of anything <1 is negative or positive

A

negative

31
Q

What is one way biological systems can make a reaction with positive ∆G°’ spontaneous?

A

When products are quickly removed from the reaction by rapidly using them in a sequential reaction, making the second term in the equation for actual ∆G negative (products lower than reactants)

32
Q

What is the structure of adenosine?

A
33
Q

What is the structure of adenosine, and how does it relate to ATP?

A
34
Q

What type of bond forms upon the conversion of adenosine to AMP?

A

phosphoester bond

35
Q

What type of bond forms upon the conversion of AMP to ADP?

A

phosphoanhydride bond

36
Q

what bond forms on upon the conversion of ADP to ATP?

A

phosphoanhydride bond

37
Q

phosphoanhydride bond vs phosphoester bond vs phosphodiester bond and an example of where they are found

A

phosphoanhydride bond:

P-O-P, found linking the last two Pi groups in ATP

phosphoester bond:

C-O-P, found linking the first Pi group with adenosine in ATP

phosphodiester bond:

C-O-P-O-C, found along the DNA backbone linking nucleotides

38
Q

NAD+: anabolism or catabolism energy carrier?

A

NAD+ collects electrons released during catabolism

39
Q

How do coupled reactions work?

A

Using shared intermediates to take advantage of the free energy from an exergonic reaction to drive an endergonic reaction

40
Q

NADPH: anabolism or catabolism?

A

NADPH is a stored form of reducing power, it is used to drive the reductive biosynthetic reaction of anabolic pathways

41
Q

What is responsible (either directly or indirectly) for all work performed by a cell?

A

the flow of electrons in redox reactions

42
Q

What is the general path of electrons through the cell?

A

Electrons move from electron rich molecules (food) to metabolic intermediates to electron carriers to oxygen

43
Q

loss of hydrogen:

oxidation or reduction?

A

oxidation

44
Q

loss of electrons:

oxidation or reduction?

A

oxidation

45
Q

gain of oxygen:

oxidation or reduction?

A

oxidation

46
Q

Can a reaction be either an oxidation reaction or a reduction rection?

A

No, they occur together, one species is being oxidised while another is reduced

47
Q

gain of hydrogen:

oxidation or reduction?

A

reduction

48
Q

gain of electrons:

oxidation or reduction?

A

reduction

49
Q

loss of oxygen:

oxidation or reduction?

A

reduction

50
Q

When NAD+ is converted to NADH, how many electrons are transferred? How many protons? Oxidation or reduction? Give an example of a reaction that would compliment this.

A

2 electrons (both stay with NADH), 2 protons (only one stays with NADH), reduction

51
Q

what is the general rule for oxidation of carbon in an organic compound?

A

more C-O bonds means more oxidised

52
Q

What is being reduced while carbon is being oxidised (the forward reaction shown)?

A

NAD+ + 2e- + 2H+ -> NADH + H+

53
Q

explain the NAD+ to NADH conversion

A

RH2 + NAD+ -> NADH + H+ + R;

From the hydride electron pair, one electron is transferred to the positively charged nitrogen of the nicotinamide ring of NAD+, and the second hydrogen atom transferred to the C4 carbon atom opposite this nitrogen. The midpoint potential of the NAD+/NADH redox pair is −0.32 volts, which makes NADH a strong reducing agent. The reaction is easily reversible, when NADH reduces another molecule and is re-oxidized to NAD+. This means the coenzyme can continuously cycle between the NAD+ and NADH forms without being consumed.

54
Q

what does NAD+ stand for?

A

Nicotinamide Adenine Dinucleotide

55
Q

Why do molecules like NADH or FADH2 exist in cells the first place?

A

H = e- + H+

  • A hydrogen ion is a proton, a hydrogen molecule is a proton+electron
  • Water dissociates to H+ + OH-, so there are always lots of protons around free in the cell.
  • Protons can exist free in the cell (recall pH), but electrons can’t.
  • To move electrons, the cell uses electron carriers like NADH and FADH2