Kreb Cycle Part 2

Question 1

What is the Kreb Cycle for ?

Answer 1

Used for synthesis of NADH
Production of amino acids
Used to generate energy through oxidation of Acetyl cOA .
Takes place in the mitochondria of Eukaryotes .

Question 2

What goes back to the pyruvate processing ?

Answer 2

The NADs and FADs produced in ETC go back to glycolysis, pyruvate processing or the Krebs Cycle for use as inputs.

Question 3

Why do I talk about pyruvate processing?

Answer 3

Because in Fermentation pyruvate is processed to either 2) lactate or 3) ethanol rather than 1) acetyl-CoA. So there are three types of Pyruvate Processing.

Because in Fermentation pyruvate is processed to either 2) lactate or 3) ethanol rather than 1) acetyl-CoA. So there are three types of Pyruvate Processing.

Question 4

Pyruvate vs Pyruvic acid?

Answer 4

Pyruvic acid has an one more hydrogen than pyruvate

Acids are H donors so
Pyruvic acid —> H+ + pyruvate

So pyruvic acid and pyruvate are not really the same thing.

Question 5

What are Cristae ?

Answer 5

Cristae are the ridges in the inner mitochondrial membrane, not THE inner mitochondrial membrane.

Cristae increase the total surface area of the inner
mitochondrial membrane which allows for more ETC systems per mitochondrion.

Inside the inner membrane are protein complexes used by the ETC to pump NADH/FADH2 protons into the intermembrane space between the inner and outer mitochondrial membranes.

Also in the inner membrane are the systems (ATP Synthase) used to put P on ADP to make ATP inside the inner membrane due to the passage of protons that were pumped out by the ETC.

Question 6

What happens at Isoleirate ?

Answer 6

Isocitrate is oxidized and decarboxylation occurs with a carbon dioxide molecule released. The coenzyme NAD­+ is reduced to form another dinucleotide, NADH. With the removal of the carbon molecule, the five-carbon molecule α-ketoglutarate is produced.

Question 7

What happens to the α-ketoglutarate molecule ?

Answer 7

The α-ketoglutarate molecule is oxidized, NAD­+ is reduced to form NADH and another carbon molecule is released. The four-carbon molecule produced combines with Coenzyme A, forming the unstable succinyl CoA compound.

Question 8

What does the Phosphate group do ?

Answer 8

A phosphate group replaces the Coenzyme A in succinyl CoA, which is then transferred to ADP (adenosine diphosphate) to form ATP. The transference of the phosphate groups occurs between GDP (guanosine diphosphate) to form GTP (guanosine triphosphate) in some cells. The four-carbon molecule that remains is called succinate.

Question 9

The remaining steps of the Krebs cycle regenerate oxaloacetic acid from succinate:

Answer 9

Succinate is oxidized to form the four-carbon molecule called fumerate. The electron carrier FAD (flavin adenine dinucleotide), is reduced to FADH2 by the transference of two hydrogen atoms.

Fumerate is converted into the four-carbon molecule called malate by the addition of a water molecule.
The original reactant oxaloacetic acid is regenerated by the oxidation of malate.

The coenzyme NAD (nicotinamide adenine dinucleotide) is reduced to NADH by the transference of one hydrogen atom.:

Question 10

What is the main production of the Kreb cycle ?

Answer 10

For one cycle, two molecules of carbon, three molecules of NADH, one molecule of FADH2 and one molecule of ATP or GTP are produced.

Each glucose molecule produces two molecules of acetyl CoA, enough for two cycles. These products can be multiplied by two to produce the per-glucose yield.

Though only one ATP (or GTP) is produced directly per cycle, the products NADH and FADH2, can produce ATP (or GTP) in a further process of cellular respiration called oxidative phosphorylation.

Question 11

What is the main function of the kerb cycle?

Answer 11

The main function of the Krebs cycle is to produce energy, stored and transported as ATP or GTP.

The Krebs cycle is found in all cells that use oxygen. Combined with the process of oxidative phosphorylation, the Krebs cycle produces the majority of energy used by aerobic cells with the percentage energy provided for humans being greater than 95%.

The cycle is also central to other biosynthetic reactions where the intermediates produced are required to make other molecules, such as amino acids, nucleotide bases and cholesterol.

Question 12

What does citratate do ? In the process

Answer 12

Citrate is then converted into isocitrate, a six-carbon isomer of citrate by dehydrating and then hydrating the molecule to reshuffle its structure.

Question 13

What does citrate do ? In the process

Answer 13

Citrate is then converted into isocitrate, a six-carbon isomer of citrate by dehydrating and then hydrating the molecule to reshuffle its structure.

Question 14

What is the Products in the Electron Transport Chain ?

Answer 14

10 NAD+
2 FAD
12 H20

Question 15

What are the electrons after pyruvate during glycolysis ?

Answer 15

6C02
4 ATP
10 NADH
2 FADH2

Question 16

What is Integrated Metabolism ?

Answer 16

Anabolic and Catabolic pathways for biosynthesis and enegy maintanence ATP are connected

Metabolic pathways will become 
 predominant in in an organisms depending
on:
	- genetic background
	- changes in the environment
	E. g: abundance of nutrients

Connection between metabolic
pathways allows for different
forms of life (carnivores, herbivores,
omnivores)

Question 17

Tolerance to lactorse is the result of a genectic adaptation ?

Answer 17

Genetic background: Digestive and
metabolic enzymes
determine the use of preferred
metabolic routes for homeostasis

Humans: low levels of lactose after termination of maternal milk feeding
(unable to digest lactose in adulthood)

Mutations in lactase

Persistance of lactase activity after termination of maternal milk feeding
(able to digest lactose in adulthood)

Evolutionary advantage: feeding from animal milk

Question 18

Atkins Diet ?

Answer 18

Low carbohydrate intake

Question 19

Other Metabolic routes

Answer 19

The majority of compounds that are ingested get metabolised by hepatocytes
in the liver but also by other cells in the body

• Enzyme repertoires determine the capacity of metabolism of ingested substances

Chocolate: Toxic for dogs
Slow metabolism

Question 20

The products of pyruvate oxidation include :

Answer 20

2 CO2

• 2 NADH
• 2 acetyl-CoA which consists of 2 carbons from pyruvate attached to coenzyme A

Acetyl-CoA proceeds to the Krebs cycle.

Question 21

Redox Reaction

Answer 21

Oxidation or an increase in oxidation state by a molecule, atom, or ion is the loss of electrons.

Reduction or a decrease in oxidation state by a molecule, atom, or ion is the gain of electrons.

Question 22

Energy From ATP

Answer 22

In most cases the energy is supplied by the hydrolysis of one of the high energy bonds - phosphoanhydride bond in ATP.

Question 23

What happens with the present /absents of oxygen ?

Answer 23

The fate of pyruvate depends on oxygen availability.

When oxygen is present, pyruvate is oxidized to acetyl-CoA which enters the Krebs cycle

Without oxygen, pyruvate is reduced in order to oxidize NADH back to NAD+

Question 24

With the presents and absents of oxgen part two

Answer 24

In the presence of oxygen, pyruvate is oxidized.

• occurs in the mitochondria in eukaryotes
• occurs at the plasma membrane in prokaryotes
• in mitochondria, a multienzyme complex called pyruvate dehydrogenase catalyses the reaction

Question 25

What happens during aerobic respiration , anaerobic respiration and fermentation ?

Answer 25

During respiration, electrons are shuttled through electron carriers to a final electron acceptor.

aerobic respiration: final electron receptor is oxygen (O2)

anaerobic respiration: final electron acceptor is an inorganic molecule (not O2)

fermentation: final electron acceptor is an organic molecule