Chapter nine
Plant Physiology
When some materials burn, produce heat energy
Daily, we need
energy for walk,
run, study or other
purposes. This
energy formed by a
special process
This energy produce in the mitochondria, hence its called mitochondrial respiration
Today`s Topic
2nd stage of respiration- Krebs cycle
 define the Krebs cycle;
describe the second stage of respiration;
 analysis the importance of this stage .
Krebs cycle
In respiration where the acetyl Co-A reaction with oxaloacetic acid and
formed citric acid is called Krebs cycle.
Discovery
In 1937 English Biochemist Sir Hans Krebs discovered this cycle.
Hence it is called Krebs cycle.
 The first product of this cycle is citric acid, so called citric acid cycle.
 Here take part 3 carboxyl group( COOH) , hence this cycle is called TCA
cycle
 This cycle take place in mitochondria
 This cycle discovered in chest meat of a pigeon.
 Sir Hans Krebs got Nobel in 1954 for this work
+acetyl-co-A
CO-A
Oxaloacetic acid
Citric acid
Synthase
NADH2
aconitase
dehydrogenase
NAD
Malic acid
Isocitric acid
NAD
Fumarase
Fumeric acid
Dehydrogenase
Krebs cycle
NADH2
CO2
α-keto-glutaric acid
dehydrogenase
NAD
Dehydrogenase
FADH2
CO-A
FAD
CO-A
Succinic acid
Synthetase
NADH2
CO2
Succinyl co-A
Total production
At the end of reaction , 2 acetyl Co-A, 4 molecules CO2, 6
molecules of NADH2, 2 molecules of FADH2, 2 molecules ATP/
GTP are produced.
Importance of Krebs cycle
1.
2.
3.
4.
5.
6.
7.
Who proposed the Krebs cycle & when?
Which is the first intermediate compound of Krbes cycle?
Why Krebs cycle known as TCA cycle?
In where all of the reaction occurs of Krbes cycle?
How many NADH2 formed in Krebs cycle?
How many FADH2 formed in Krebs cycle?
In where GTP formed instead of ATP in Krbes cycle?
Practice the Krbes cycle flowchart