Krebs CycleBy: Group 5

What is a Krebs Cycle?● The citric acid cycle — also known as the tricarboxylic acid

cycle (TCA cycle), or the Krebs cycle is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidization ofacetate derived from carbohydrates, fats and proteins into carbon dioxide. In addition, the cycle provides precursors including certain amino acids as well as the reducing agent NADH that is used in numerous biochemical reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism and may have originated abiogenically. This cycle occur every 2 times.

● The name of this metabolic pathway is derived from citric acid (a type of tricarboxylic acid) that is first consumed and then regenerated by this sequence of reactions to complete the cycle. In addition, the cycle consumes acetate (in the form of acetyl-CoA) and water, reduces NAD+ to NADH, and produces carbon dioxide. The NADH generated by the TCA cycle is fed into the oxidative phosphorylation pathway. The net result of these two closely linked pathways is the oxidation of nutrients to produce usable energy in the form of ATP.

What is a Krebs Cycle?● In eukaryotic cells, the citric acid cycle occurs in the matrix

of the mitochondrion. Bacteria also use the TCA cycle to generate energy, but since they lack mitochondria, the reaction sequence is performed in the cytosol with the proton gradient for ATP production being across the plasma membrane rather than the inner membrane of the mitochondrion.

● Several of the components and reactions of the citric acid cycle were established in the 1930s by the research of the Nobel laureate Albert Szent-Györgyi, for which he received the Nobel Prize in 1937 for his discoveries pertaining to fumaric acid, a key component of the cycle.

What is a Krebs Cycle?● The citric acid cycle itself was finally identified in 1937

by Hans Adolf Krebs whilst at the University of Sheffield, for which he received the Nobel Prize for Physiology or Medicine in 1953.

Bonds● Linear bond ● Isometric bond

c c c c

c c cc

Howdoes the

Krebs Cyclework?

When Acetyl CoA and oxalate combines, they form a molecule called citrate.Acetyl CoA has 2 carbon molecules and a CoA (coenzyme).While oxalate has 4 carbon molecules. So when they combine, they will have 6 carbon molecules and a CoA.

Step 1

Step 2

NAD or Nicotinamide Adenine Dinucleotide which is a 1 hydrogen receiver.

Step 3

So they can ONLY carry 1 hydrogen.In this process, a molecule of CO2 is released creating alpha-ketoglutarate.This carbon molecule will release at the atmosphere or at the mitochondria.

So again, NADH is reduced again to form NADH and leaves with another hydrogen.

Step 4

Then a carbon molecule was released again.

GTP (Guanosine triphosphate) was produced.

Step 5

Which will lead to the production of ATP (Adhenosine triphospate).

What is the difference of ATP and GTP?● ATP can be produced thru different processes:

- in mitochondria thru oxidative phosphorylation - (in plants) iin chloroplasts thru photosynthesis

● ATP is responsible for providing energy to carry out many of the body's functions. It's reponsible for regulating biochemical pathways. We also feel pain when ATP is released from a damaged cell.

● GTP is produced in the Krebs Cycle but the molecule can be easily converted to ATP by the action of the Nucleoside Diphosphokinase.

● GTP is used as an energy source in protein synthesis. It's also responsible for enegy transfer within the cell.

A FAD (Flavin adenine dinucleotide) is a 2 hydrogen acceptor.

Step 6

They can ONLY accept 2 hydrogen molecules.In this process the 4 carbon molecules will be an isometric bond.

Step 7

The end product will be an oxalate and will repeat the cycle again.

Step 8

Summary● In this summary, three major events occur during the

Krebs cycle. One GTP (guanosine triphosphate) is produced which eventually donates a phosphate group to ADP to form one ATP; three molecules of NAD are reduced; and one molecule of FAD is reduced. Although one molecule of GTP leads to the production of one ATP, the production of the reduced NAD and FAD are far more significant in the cell's energy-generating process. This is because NADH and FADH2 donate their electrons to an electron transport system that generates large amounts of energy by forming many molecules of ATP.

Quiz Time....Please get a ¼ sheet of paper and write the ANSWERS only.

Question:● How many times does the Krebs Cycle

occur?

Question:● How many carbon molecule/s is oxalate?

Question: (letter only)● What does “NAD” stands for? A. Nitrogenic Asylosis Dyclosygloritide B. Nitrotinomide Asylosis Dynonucleode C. Nicotinomide Adenin Dinucleotide D. Nucleotide Adnin Dysaccharide

Question:● How many carbon molecule/s does NAD

and FAD accept/s? NDA: ? FAD: ?

Question:● What kind of bonds are these?

C C C C

CCCC

?

?

Question:● Where does the CO2 exits?

Question:● What is the process after “fumanic/

fumarate acid”?

Question: What process is this?

?

DONE!Please pass the paper.