Unit II - Chapter 6 - Bioenergetics And Oxidative Phosphorylation

Question 1

Kinetics measures __________________

Answer 1

How fast the reaction occurs

Question 2

What determines the direction and extent to which a chemical reaction proceed is?

Answer 2

The degree to which two factors change during the reaction

Question 3

Enthalpy (🔺H):

Answer 3

A measure of the change in heat content of reactants and products

Question 4

Entropy (🔺S):

Answer 4

A measure of the change in randomness or disorder of reactants and products

Question 5

Free energy (G):

Answer 5

Predicts the direction in which a reaction will spontaneously proceed.

Question 6

Change in free energy:

Answer 6

• energy available to work
• approaches zero as reaction proceeds to eqilibrium
• predicts whether a reaction is favorable

Question 7

Change in entalpy:

Answer 7

• heat released or absorbed during a reaction

- does not predics whether a reaction is favorable

Question 8

Change in entropy:

Answer 8

• measure of randomness

- does not predict whether a reaction is favorable

Question 9

T= ?

Answer 9

T is the absolute temperature in Kelvin (K): K=celsius + 273

Question 10

🔺G:

Answer 10

Represents the change in free energy and, thus, the direction of a reaction at any specified concentration of products and reactants. 🔺G, then, is a variable.

Question 11

🔺G^0:

Answer 11

• Is the energy change when reactants and products are at concentration of 1mol/L.
• Can be determined from measurment of equilibrium constant

Question 12

What can 🔺G be used for:

Answer 12

It can be used ro predict the direction of a reaction at constant temperature and pressure. A ↔️ B

Question 13

Negative 🔺G:

Answer 13

If 🔺G is negative, tjere is a nett loss of energy, and the reaction goes spontaneously. The reaction is said to be EXERGONIC.

Question 14

Positive 🔺G:

Answer 14

If 🔺G is positive, there is a net gain of energy, and the reaction do not go spontanously from A to B. Energy must be added to the system to make the reaction go from A to B. The reaction is said to be ENDERGONIC.

Question 15

🔺G is zero:

Answer 15

If 🔺G = 0, the reactants are in equilibrium. When a reaction is preoceeding spontaneously (that is free energy being lost) then the reaction continous until 🔺G reaches zero and equilibrium is established.

Question 16

Bioenergetics predicts _______________

Answer 16

If a process is possible

Question 17

Oxidative phosphorylation;

Answer 17

The coupling of electron transport with ATP synthesis.

Often denoted as OXPHOS

Question 18

Where is the electron transport chain of the mitochondrion located?

Answer 18

In the inner mitochondrial membrane

Question 19

What is between the inner and outer membrane in the mitochondrion?

Answer 19

Intermembrane space

Question 20

What are the channels on the outer membrane of the mitochondrion formed by?

Answer 20

Protein porin

Question 21

Which membrane of the mitochondrion is permeable?

Answer 21

The outer membrane

Question 22

Which membrane of the mitochondrion is impermeable?

Answer 22

The inner membrane

Question 23

Cristae

Answer 23

Increases the surface of the inner membrane of mitochondrion.

Question 24

What is inside the matrix of the mitochondrion?

Answer 24

• rich in protein
• enzymes responsible for the oxidation of the pyruvate.
• amino acids
• fatty acids (by beta-oxidation) as well as those of the tricarboxylic acid (TCA) cycle
• NAD+, FAD, ADP, Pi, ATP
• mitochondrial DNA (mtDNA) and RNA (mtRNA)
• mitochondrial ribosomes

Question 25

What processes occurs in the matrix of mitochondrion?

Answer 25

Synthesis of:

• glycose
• urea
• heme

Question 26

How many protein complexes does the inner membrane of the mitochondrion contain?

Answer 26

Five: I-V

Question 27

Complexes of the inner mitochondrial membrane;

Answer 27

• I-V
• they contain part of the ETC
• accept or donate electrons to the relatively mobile electron carriers, coenzyme Q and cytochrome c

Question 28

Are all members of the ETC proteins?

Answer 28

No, coenzyme Q is an exeption

Question 29

Formation of NADH:

Answer 29

• NAD+ is reduced ot NADH by dehydrogenases that remove two hydrogen atoms from their substrate.
• Both electrons but only one proton are transferred to the NAD+ foming NADH plus a free electron.

Question 30

NADH dehydrogenase;

Answer 30

The free proton plus the hydride ion carried by NADH are next transferred to NADH dehydrogenase, a protein complex (Complex I) embedded in the inner mitochondrial membrane.
Complex I has a tightly bound molecule of flavin mononucleotide (FMN, a coenzyme structurally related to FAD) that accepts the two hydrogen atoms (2e– + 2H+), becoming FMNH2. NADH dehydrogenase also contains iron atoms paired with sulfur atoms to make iron–sulfur centers.
These are necessary for the transfer of the hydrogen atoms to the next member of the chain, coenzyme Q (ubiquinone).

Question 31

Coenzyme Q (CoQ):

Answer 31

• is a quinone derivative with a long, hydrophobic isoprenoid tail.
• also called ubiquinone because it is ubiquitous in biologic systems.
• is a mobile carrier and can accept hydrogen atoms both from FMNH2, produced on NADH dehydrogenase (Complex I), and from FADH2, produced on succinate dehydrogenase (Complex II), glycerophosphate dehydrogenase, and acyl CoA dehydrogenase.
• transfers electrons to Complex III. CoQ, then, links the flavoproteins to the cytochromes.

Question 32

Cytochromes:

Answer 32

• The remaining members of the electron transport chain.
• Each contains a heme group (a porphyrin ring plus iron). Unlike the heme groups of hemoglobin, the cytochrome iron is reversibly converted from its ferric (Fe3+) to its ferrous (Fe2+) form as a normal part of its function as a reversible carrier of electrons.
• Electrons are passed along the chain from CoQ to cytochromes bc1 (Complex III), c, and a + a3 (Complex IV).
• Note: Cytochrome c is associated with the outer face of the inner membrane and, like CoQ, is a mobile carrier of electrons.

Question 33

Cytochrome a + a3:

Answer 33

They are the only electron carrier in which the heme iron has an available coordination site that can react directly with O2, and so also is called cytochrome oxidase. At this site, the transported electrons, O2, and free protons are brought together, and O2 is reduced to water. Cytochrome oxidase contains copper atoms that are required for this complex reaction to occur.

Question 34

Site-specific inhibitors:

Answer 34

• They prevent the passage of electrons by binding to a component of the chain, blocking the oxidation/reduction reaction. Therefore, all electron carriers before the block are fully reduced, whereas those located after the block are oxidized.
• Note: Inhibition of electron transport inhibits ATP synthesis because these processes are tightly coupled.

Question 35

Succinate dehydrogenase:

Answer 35

At complex II, electrons from the succinate dehydrogenase-catalyzed oxidation of succinate to fumarate move from the coenzyme, FADH2, to an iron-sulfur protein, and then to coenzyme Q.
- Note: no energy is lost in this process, and, therefore, no protons are pumped at Complex II.