Krebs Cycle (GRADE 9 SCIENCE)

1. Krebs Cycle

2. Krebs Cycle
The second stage in cellular respiration, continues where glycolysis left off.
The two molecules of the three-carbon pyruvate produced in glycolysis leave the
cytoplasm and enter the mitochondria, where further chemical processes take
places to produce more ATPs. Because of this process, the mitochondria are
referred to as “powerhouse of the cell”

3. Before the three-carbon pyruvate enters the Krebs Cycle, it is first converted
into a two-carbon molecule called acetyl-CoA. The Krebs cycle or citric acid cycle
refers to a series of enzyme-catalyzed reactions that break down acetyl-CoA
completely into carbon dioxide and water. Exhalation is the body’s way of getting rid
of carbon dioxide produced in Krebs cycle. The process takes place in the inner
matrix of the mitochondria. For every molecule of acetyl-CoA that enters the Krebs
cycle, one molecule of ATP is generated, along with three molecules NADH
(Nicotanaminde adenine dinucleotide and one molecules of FADH² (FAD =
Flavin adenine dinucleotide).

4. NADH is a naturally occuring vital compound found in cells of living organisms. It is
a high-energy molecule used by cells to generate ATP. FADH2 is formed when FAD
is oxidized by gaining two hydrogen ions (H+). NADH and FADH2 are electron
carrier molecules, which are used to generate more ATPs through the electron
transport chain. The entire cycles repeats with the second acetyl-CoA molecule. As
the second round continues, more NADH, carbon dioxide, ATP, and FADH2
molecules are produced.

6. 1
4
2
3
Acetyl-CoA combines with a four-carbon compound to form a
six-carbon compound.
Another molecules of carbon dioxide is released from the
five-carbon compound to form a four-carbon compound.
The four-carbon compound is converted into a new four-
carbon compound.
5
The new four-carbon compound is converted into a four-
carbon compound similar to that of the four-carbon compound
at the start of the cycle. The four-carbon compound re-enter
the cycles.
Carbon dioxide is released from the six-carbon compound,
resulting a five-carbon compound.