MBIO 2730 BIOENERGETICS

To live organisms must obtain _ from their environment and use it to do the of building and organizing cell components such as proteins enzymes nucleic acids membranes organelles.

energy // work

What are photosynthetic autotrophs?

uses the energy of sunlight to convert low G CO2 and H2O into energy rich complex sugar molecules

What delta G and S does the photosynthesis reaction have?

large positive delta H; large negative delta S

The products of photosynthesis have more _ and are more ordered than the reactants.

enthalpy

How do heterotrophs gain energy?

extract the chemical potential energy stored in sugars and other organic compounds and release CO2 and H2O

What is the size of delta H and G for cellular respiration?

large negative delta H and large positive delta S; products have lost energy and are less ordered

Delta G not prime refers to what kind of standardized conditions?

' refers to pH = 7; not refers to 25 degrees celsius

What is the equation for delta G not prime?

-RTln(Keq)

If K'eq > 1 delta G and direction are?

negative
forward

If K'eq < 1 delta G and direction are?

positive
reverse

If K'eq = 1 delta G and direction are?

0
no direction

When deltaGnotprime is negative the products contain less _ than the reactants.

G

When deltaGnotprime is positive the products contain more _ than the reactants.

G

For a chemical reaction at equilibrium

the rates of forward and reverse reactions are _.

What is delta G at equilibrium?

0

What is the equation for the actual G under non-standard conditions?

delta G = delta G not prime + RT ln[C][D]/[A][B]

Both delta G and delta G not prime are theoretical maxima. What does this mean?

some G is always lost as heat

Even if deltaGnotprime is positive the reaction can go forward if delta G is negative. Why?

the second term is negative and bigger than deltaGnotprime

Are delta G's of sequential reactions additive? Why?

yes; delta G is path independent

The G released in one reaction can be used to drive a second reaction if what condition is met?

as long as the two share a common intermediate

Nearly all of the G stored in carbohydrates, lipids, AA, etc transits through what?

adenosine triphosphate (ATP)

ATP is the cell's energy currency. What is it used for?

building cell constituents; muscle contraction; active transport

What is the common intermediate between catabolism and anabolism?

ATP

The synthesis of ATP: ender or exergonic?

highly endergonic

The hydrolysis of ATP: end or exergonic?

highly exergonic

What is the delta G not prime of ATP hydrolysis?

-30 kJ/mole

How does ATP store chemical potential energy?

relief of charge repulsion; entropy increase; stabilization of products

How does ATP relieve charge repulsion?

one molecule with four negative charges becomes two molecules with two negative charges each

There are more resonance forms of ADP + Pi than of ATP so there is an entropy increase due to __.

hydrolysis

Other compounds with large negative delta G of hydrolysis similar to ATP are:

1, 3 bisphosphoglycerate

phosphoenolpyruvate

What is substrate level phosphorylation?

cells use high G compounds to make ATP

What is photophosphorylation?

ATP synthesis using chemiosmosis and a proton gradient generated in photosynthesis

What is oxidative phosphorylation?

uses energy released by electron transport chain to power ATP synthesis

The phosphate from ATP is transferred to an enzyme or substrate which becomes _.

activated

The reaction is complete by displacement of Pi, which is a downhill, G-_____________________ reaction.

releasing

Are other nucleoside triphosphates as good as ATP?

yes; energetically equivalent

How are nucleoside triphosphates usually made?

by nucleoside diphosphate kinases

What are thioester bonds?

bonds using sulfur to form covalent linkages

Thioester bonds provide energy storage. Why?

less stable than oxygen esters; oxygen esters are resonance stabilized and store less G

Drop occurs when going from thioester to ester because…?

thioester is less stable than ester

Electron can also do work.

flow

Cu2+ has a higher electron affinity than Zn2+

so when Zn is placed in a copper sulfate solution

What does it mean when something is oxidized?

losing electrons

What does it mean when something is reduced?

gaining electrons

O2 has higher electron affinity than glucose so electrons flow from _ to __.

glucose to O2, releasing G

What is NAD+?

a water-soluble

What does NAD+ stand for?

Nicotinamide Adenine Dinucleotide

Nicotinamide is also known as

niacin; vitamin B6

How are electrons transferred on NAD+?

as H− (hydride ion)

What does the enzyme malate dehydrogenase do?

removes electrons from L-malate to form oxaloacetate; reduces NAD+ to NADH

Over _ dehydrogenase enzymes are known that use NAD+

200

Other examples of water soluble covalently bound electron carriers are:

FMN and FAD

What does FMN stand for?

flavin mononucleotide

What does FAD stand for?

flavin adenine dinucleotide

The relative affinity of an atom or molecule for electrons can be measured. How?

using a reference solution containing H2 at 101 kPa and 1 M H+

When measuring the relative affinity of an atom or molecule for electrons what is the reaction?

1/2 H2 → H+ + e-

If the electrons move to hydrogen does the unknown want them?

No

If electrons move to the unknown…

it wants electrons more than hydrogen

What is the electron motive force of Fe3+ when being tested?

+0.77 V

What is the net reaction when testing Fe3+?

1/2 H2 + Fe3+ → H+ + Fe2+

If testing the electron motive force of NADH where will the electrons flow?

H+ will draw e- from NADH

What is the standard reduction potential of NADH?

-0.32 V

The more positive the standard reduction potential the stronger the _ agent.

Oxidizing 

When calculating summed standard reduction potentials which sign gets flipped?

the sign of the species that wants electrons more