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AEROBIC AND ANAEROBIC
PATHWAY

By: Suooda Fathimath
Plant Physiology

WHAT IS RESPIRATION?
It is a cellular catabolic process, in which the organic food
substances (Glucose ﴿ are oxidized completely or partially
with or without using oxygen, resulting in the formation of
ATP molecules
...


TYPES OF RESPIRATION
There are two types of respiration
...
Aerobic respiration - takes place in the cells of higher
plants and animals, using oxygen for the oxidation of
glucose
...
Anaerobic respiration - takes place, in microorganisms
without using oxygen for the oxidation of glucose
...


• Only photosynthetic organisms like plants or blue-green alga can
transform light energy into chemical energy
...


CELL RESPIRATION IS SEPARATED INTO 4 STAGES

• Energy/electrons are transferred from glucose to convert
NAD+ to NADH, which is used in the ETC to make ATP

HYDROGEN CARRIERS IN RESPIRATION
•The Hydrogen carriers in respiration are NAD
(Nicotinamide Adenine Di nucleotide) and FAD (Flavin
Adenine Di Nucleotide
...

• Their role is to transport the hydrogen atoms of glucose to
the ETS
...

• It takes place in the cytoplasm of the cell
...

•Glucose(6C)+2ATP+ 4ADP+2NAD→ 2PyruvicAcid(3C)
+2ADP+4ATP+ 2NADH

3 FATES OF PYRUVATE
1
...

2
...
Anaerobic conditions
(microorganisms and yeast):
Conversion to ethanol

KREB’S CYCLE OR CITRIC ACID CYCLE
•It operates in the mitochondrial matrix
...

•Initially, the pyruvic acid formed at the end of glycolysis
undergo oxidative decarboxylation to form acetyl CoA
...

Pyruvic acid + CoA+ NAD →Acetyl CoA + CO2 + NADH

OVERALL REACTION OF KREB’S CYCLE
•OAA is regenerated during this cycle
...
Each pyruvic acid molecule gives three molecules
o f CO2, 4 NADH, 2 FADH and one ATP
...


ELECTRON TRANSPORT SYSTEM (ETS/ETC)
•It is the third step in aerobic respiration , in which oxygen is used
...


•In this step NADH and FADH formed during glycolysis and Kreb’s
cycle get oxidized
...
(Oxidative Phosphorylation)

TERMINAL OXIDATION
•Oxidation of one NADH yields 3ATP and one FADH gives
2 ATP molecules
...
Hence it is called terminal
oxidation
...


ATP ACCOUNT DURING AEROBIC RESPIRATION
Pathway

Substrate-Level
Phosphorylation

Oxidative
Phosphorylation

Total ATP

Glycolysis

2 ATP

2 NADH = 6 A T P

8

2 NADH = 6 ATP

6

Preparatory step
Citric cycle

2 ATP

6 NADH = 18 ATP
2 FADH2 = 4 ATP

24

Total

4 ATP

34 ATP

38

SUMMARY‐ AEROBIC RESPIRATION
Glucose (C6 H12 O6 ) + 6O2→6CO2 + 6H2 O +38ATP

1
...

2
...
Takes place in the cytoplasm and mitochondria of the
cell, in three steps
...
Products are 6CO2 + 6H2 O +38ATP

ANAEROBIC RESPIRATION
•It is the partial oxidation o f glucose molecule without
using oxygen
...

•There are two types of fermentation depending upon the
end products
...
Ethyl alcohol fermentation
2
...

Reactions include,
1
...
Pyruvic acid →Acetaldehyde +
CO2
...
Acetaldehyde + NADH+H
→Ethyl alcohol+ NAD

LACTIC ACID FERMENTATION
•It takes place in some bacteria and animal tissue when
oxygen is absent
...

•1
...
Pyruvic acid +NADH + H →Lactic acid + NAD

•Fermentation process has wide industrial application

RATE OF RESPIRATION AND FACTORS AFFECTING IT
•The rate of respiration can be measured by the amount of
CO2 released
...

•In general the factors which affect respiration include
internal factors such as the activity of the respiratory
enzymes the type of substrate; and external factors such
as oxygen, water, temperature etc
...

The kind of substrate being oxidized is obtained by measuring the
respiratory quotient
...
Q?

b) Temperature - The temperature between 30-35°C is most
suitable for respiration
...

d) Carbon dioxide–rate of respiration decreases if CO2 is
allowed to accumulate
...
Dormant seeds show
very low rate of respiration
...


Takes place normally in some higher
plants and animals

Takes place normally in some bacteria,
and fungi

Glucose is completely oxidized
...

The end products are carbondioxide
and either ethyl alcohol or lactic acid
Partial oxidation of one molecule of
glucose yields only 2 ATP molecules
Takes place only in cytoplasm of the cell

Process takes place in both cytoplasm
and mitochondria of the cell

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