2. Cellular respiration as a a) Glycolysis
process of obtaining energy It takes place in the cytosol of the cell.
(This because all enzymes that catalyze reactions of the
glycolysis are found in the cytosol of the cell)
Cellular respiration is the process by which chemical
This process does not depend on O2.
energy in organic molecules such as carbohydrates
During the above process a six carbon (6C) glucose
is released by stepwise oxidative process, catalyzed
molecule is broken down step by step into two three-
by enzymes, and made available in living cells in the
carbon (3C) pyruvate molecules.
form of ATP.
Two ATP molecules are used up to initiate the process.
Cellular respiration is divided as At the end of glycolysis there will be four ATP molecules
a) aerobic respiration produced.
b) anaerobic respiration The net yield will be two ATP molecules.
Four Hydrogen ions and electrons are released from
one molecule of glucose breakdown
The hydrogen ions and electrons will reduce two NAD+
and produce two NADH.
Only when O2 is present, the pyruvate molecules will
enter the mitochondria and further steps will take place.
b) Oxidation of Pyruvate and Citric acid
cycle
Oxidation of Pyruvate/ Link reaction
The two pyruvate molecules enter mitochondrion by
active transport through the membrane.
In the matrix of mitochondria, Pyruvate is converted to
acetyl group by releasing two CO2 molecules.
Then this acetyl group combines with co-enzyme A to
produce Acetyl Co-A.
In this reaction two NAD+ is converted to two NADH
1.) AEROBIC RESPIRATION molecules. Therefore, this step can be represented as
follows.
The process of synthesizing ATP from the respiratory
substrates such as glucose in the presence of Oxidation of pyruvate is the linking reaction between
molecular oxygen (O2) known as aerobic respiration. glycolysis and citric acid cycle
Acetyl Co-A will feed its acetyl group to the citric acid
Glucose is found to be the major respiratory substrate in
cycle
living cells.
The aerobic respiration of glucose molecules can be
represented by the following balanced chemical Citric acid cycle
equation.
This takes place in the matrix of mitochondria using
specific enzymes.
This process consists of three main steps.
This cycle has several names,
a) Glycolysis - Cytosol
i. Citric acid cycle - As the first product of this
b) Pyruvate oxidation and citric acid cycle (Krebs
cyclic pathway is citric acid.
cycle) – Mitochondrial matrix
ii. Krebs cycle - The pathway was discovered by a
c) Oxidative phosphorylation (Electron transport
German-British scientist Hans Krebs.
chain) – Cristae of mitochondria
iii. Tricarboxylic Acid cycle or TCA cycle – as citric
acid contains three carboxylic acid groups.
process of obtaining energy It takes place in the cytosol of the cell.
(This because all enzymes that catalyze reactions of the
glycolysis are found in the cytosol of the cell)
Cellular respiration is the process by which chemical
This process does not depend on O2.
energy in organic molecules such as carbohydrates
During the above process a six carbon (6C) glucose
is released by stepwise oxidative process, catalyzed
molecule is broken down step by step into two three-
by enzymes, and made available in living cells in the
carbon (3C) pyruvate molecules.
form of ATP.
Two ATP molecules are used up to initiate the process.
Cellular respiration is divided as At the end of glycolysis there will be four ATP molecules
a) aerobic respiration produced.
b) anaerobic respiration The net yield will be two ATP molecules.
Four Hydrogen ions and electrons are released from
one molecule of glucose breakdown
The hydrogen ions and electrons will reduce two NAD+
and produce two NADH.
Only when O2 is present, the pyruvate molecules will
enter the mitochondria and further steps will take place.
b) Oxidation of Pyruvate and Citric acid
cycle
Oxidation of Pyruvate/ Link reaction
The two pyruvate molecules enter mitochondrion by
active transport through the membrane.
In the matrix of mitochondria, Pyruvate is converted to
acetyl group by releasing two CO2 molecules.
Then this acetyl group combines with co-enzyme A to
produce Acetyl Co-A.
In this reaction two NAD+ is converted to two NADH
1.) AEROBIC RESPIRATION molecules. Therefore, this step can be represented as
follows.
The process of synthesizing ATP from the respiratory
substrates such as glucose in the presence of Oxidation of pyruvate is the linking reaction between
molecular oxygen (O2) known as aerobic respiration. glycolysis and citric acid cycle
Acetyl Co-A will feed its acetyl group to the citric acid
Glucose is found to be the major respiratory substrate in
cycle
living cells.
The aerobic respiration of glucose molecules can be
represented by the following balanced chemical Citric acid cycle
equation.
This takes place in the matrix of mitochondria using
specific enzymes.
This process consists of three main steps.
This cycle has several names,
a) Glycolysis - Cytosol
i. Citric acid cycle - As the first product of this
b) Pyruvate oxidation and citric acid cycle (Krebs
cyclic pathway is citric acid.
cycle) – Mitochondrial matrix
ii. Krebs cycle - The pathway was discovered by a
c) Oxidative phosphorylation (Electron transport
German-British scientist Hans Krebs.
chain) – Cristae of mitochondria
iii. Tricarboxylic Acid cycle or TCA cycle – as citric
acid contains three carboxylic acid groups.
