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Chpt. 12:
Respiration
Two types of respiration
External Respiration
-is the process by which
organisms exchange gases
with their environment,
e.g. occurs in lungs of
mammals, gills of fish.
Internal respiration
- is the controlled
release of energy
from food.
Internal Respiration
• controlled by enzymes.
• normally involves the breakdown of glucose.
• Energy that is released is trapped in the form of
ATP:
Enzymes
Glucose
Energy
(ATP)
•Two types of internal respiration:
1 Aerobic respiration.
2 Anaerobic respiration.
Internal Respiration
Aerobic Respiration: is the release of energy
from food within cells using oxygen.
Aerobes – living organisms which get their energy
from aerobic respiration.
Brief explanation of aerobic respiration:
• Energy stored in bonds of glucose molecule
released and used to make ATP.
•When ATP breaks down it supplies energy for all
metabolic reactions in the cell, e.g. growth,
production of new cells etc.
Internal Respiration
Process of aerobic respiration can be represented
by the balanced equation:
Enzyme
Glucose + Oxygen
Carbon Dioxide + Water + Energy
C6H12O6 + 6O2 = 6CO2 + 6H2O + Energy
Internal Respiration
Detailed explanation of aerobic respiration (O.L.):
Aerobic respiration is a two stage process:
Stage 1:
 A process called glycolysis occurs in the cytosol
(liquid in cell that surrounds the cell organelles) of
the cell.
Glycolysis does not use oxygen – anaerobic
process.
This process releases very little energy!!!
Glycolysis involves the splitting of glucose with 6
carbon molecules (C6) into two 3 carbon molecules
(C ).
Internal Respiration
Stage 1:
 At the same time a small number of ATP
molecules are released.
Glycolysis:
Glucose
two 3 carbon + small amount
molecules
of energy
Note: stage 1 does not require oxygen and releases a
small amount of energy!!!
Internal Respiration
Stage 2:
 takes place in the mitochondria.
 requires oxygen – aerobic respiration.
 releases a lot of energy – it produces many ATP
molecules.
This stage involves the complete breakdown of
the two C3 molecules releasing a large amount of
energy which is used to form a large amount of
ATP molecules.
Carbon dioxide and water (contain very little
energy) are the end products of stage 2 and
subsequently aerobic respiration.
Internal Respiration
Aerobic Respiration (O.L)
Glucose (6 carbons)
Small energy release
Stage 1
Anaerobic
Two 3 – carbon molecules
Large energy release
Carbon Dioxide and Water
Stage 2
Aerobic
Internal Respiration
Anaerobic Respiration: is the release of energy
from food without using oxygen.
Anaerobes: living organisms which get their energy
from anaerobic respiration.
Brief explanation of anaerobic respiration:
 occurs in the cytoplasm of the cell.
 Glycolysis occurs breaking glucose (C6) into two
3 – carbon molecules (C3)
 This process releases very little energy!!! As a
result this process is far less efficient process than
aerobic respiration as glucose only partially broken
down.
Internal Respiration
Anaerobic respiration also known as fermentation
Two types of fermentation
Lactic Acid Fermentation
Alcohol Fermentation
Internal Respiration
Lactic Acid Fermentation (Anaerobic Respiration):
 occurs in some bacteria and fungi and in
mammal muscle (humans) when it is short of
oxygen.
 This process can be represented by the
equation:
Glucose
2 Lactic Acid + Small amount
of energy
Internal Respiration
Alcohol Fermentation:
occurs in some bacteria, fungi (such as yeast)
and in plants when they are deprived of
oxygen.
This process can be represented by the
equation:
Glucose
2 ethanol + 2 carbon dioxide
+
small amount of
energy
Micro Organisms in Industrial Fermentation
• Biotechnology (bioprocessing): is the production
of useful products using living cells or their parts
(cells, enzymes).
• Biotechnology: involves the use of plants,
animals and (mainly) micro-organisms.
• Fermentation: in industry means the production
of useful products by micro-organisms with or
without the use of oxygen.
Industrial Fermentation – Production Method
Note: Bioreactor – vessel in which the biological
reactions take place (pg. 117).
• Micro – organisms – placed in bioreactor with
suitable substrate.
•Mixture – stirred or agitated to ensure contact
between micro –organisms and substrate.
• Foam – ,which is produced as a result of mixing,
removed by foam breaker.
•Culture Medium – liquid in which micro-organisms
grow.
Industrial Fermentation – Production Method
• Air is pumped into bioreactor to ensure adequate
amount of oxygen dissolved in culture medium.
• Sparger – forms small air bubbles which dissolve
more readily into culture medium.
• Other important factors during production:
1. correct nutrients and micro – organisms.
2. suitable temperature and pH.
3. sterile environment.
Micro – Organisms used in Bio processing
Wide range of micro – organisms used to produce
a huge range of useful chemicals and materials:
• Fungi (yeast) - used in beer and wine
production.
- used to supply carbon dioxide to
cause dough to rise.
• Bacteria and yeasts – manufacturing yoghurt,
cheese, vinegar, antibiotics.
• Genetically altered bacteria, yeasts, fungi –
solvents, amino acids, vitamins, drugs, food
additives, enzymes.
Differences between Aerobic and
Anaerobic Respiration
Location
Oxygen Requirements
End Products
Aerobic
Anaerobic
Cytoplasm and Lumen
and Cristae of
mitochondria
Cytoplasm
Uses O2
Does not use O2
CO2 + H2O
Ethanol +CO2
or
Lactic acid
Energy Produced
Lots of energy
(38 ATP)
Little energy
(2 ATP)
Detailed Study of Aerobic
Respiration
Higher Level
Stage 1: Glycolysis (small amount of energy produced)
- occurs in cytosol of cell.
- enzymes speed up the process.
- glucose which is a 6-carbon (C6) sugar is converted to
two 3-carbon (C3) sugars called pyruvic acid.
-This is neutral molecule which may be found as the
negatively charged ion pyruvate.
- No oxygen is required some of the energy released
forms 2 ATP molecules more of the energy is used to
form NADH.
Stage 1:
Starch in plants
Glycogen in animals
Glucose (C6)
ADP + P
ATP
NAD+
NADH
PYRUVIC ACID
C3
NAD+
NADH
ADP + P
ATP
PYRUVIC ACID
C3
Stage 1:
Glucose (C6)
2 Pyruvic + 2ATP
Acids (C3)
Stage 2:
In stage 2 a complex series of reactions take place
• If oxygen is present the 2 pyruvic acids enter the
lumen(matrix) of the mitochondria and the following processes take
place:
A) Formation of acetyl coenzyme A
• Pyruvic acid (3C) is converted to acetyl coenzyme A (2C) by the
removal of CO2 and 2 e•
NAD+ is an electron acceptor and it will combine with the 2eand a H+ proton to produce NADH:
NAD+ + 2e- + H+
NADH
Note: this NADH enters an electron transport system (ETC)
to produce H2O and ATP – discuss later
Stage 2:
B) Krebs Cycle
• Acetyl coenzyme A now enters a series of reactions
called Krebs Cycle
• Acetyl coenzyme A is broken down to CO2, H+ protons
and 2e- by a series of reactions.
• 2e- and H+ combine with NAD+ to form NADH (goes
to ETC)
• One ATP (phosphorylation) is made in each cycle.
Stage 2:
B) Krebs Cycle
Please be familiar with diagram representing this cycle
Pyruvic Acid (3C)
CO2
NAD+
2e-
NADH
Electron
Transport System
Acetyl coenzyme A (2C)
NADH
2e-
CO2
3NAD+
NAD+
6e-
CO2
3NADH
ATP + water
ADP + P
Electron Transport
System
Stage 2:
C) Electron Transport Chain (ETC)
• Electron transport chains are located on the inner
membrane (cristae –folds) of the mitochondria.
• Each electron transport chain consists of electron
carrier proteins in an orderly sequence in the cristae
of the mitochondria.
• High energy electrons are passed from NADH to the
first of these protein molecules.
• As electrons pass from molecule to molecule within
each chain they lose some of their energy.
Stage 2:
C) Electron Transport Chain (ETC):
• Some of the energy released by the electrons is
used to form ATP (oxidative phosphorylation) and
the rest is lost as heat.
• At the end of each chain , low energy electrons are
removed by combining with oxygen and hydrogen
to form water.
Stage 2:
Electron Transport Chain (Oxidative Phosphorylation)
H+ and NAD+
NADH
(From Krebs Cycle)
High energy
electrons
2eADP + P
Carrier Enzyme 1
ATP
2e-
ADP + P
Carrier Enzyme 2
ATP
2e-
ADP + P
Carrier Enzyme 3
ATP
2eLow energy
electrons
2e- + 2H+ + ½ O2
H2O
Summary of Aerobic Respiration
Stage 1:
• Glycolysis - anaerobic respiration
- releases very little energy
- occurs in cytosol
Stage 2:
• Krebs Cycle rxns and Electron Transport Chains
• aerobic respiration
• release large amount of energy
• occurs in lumen and cristae of mitochondria
Anaerobic Respiration
Glycolysis (small amount of energy produced)
- occurs in cytosol of cell.
- glucose which is a 6-carbon (C6) sugar is converted to
two 3-carbon (C3) sugars called pyruvic acid.
-This is neutral molecule which may be found as the
negatively charged ion pyruvate.
- No oxygen is required some of the energy released
forms 2 ATP molecules more of the energy is used to
form 2 NADH molecules.
Anaerobic Respiration
• In the absence of oxygen the two NADH molecules
break down to release 2e- and a proton.
• The 2e- and the proton are then added to pyruvic
acid forming either:
- lactic acid (lactic acid fermentation)
- ethanol and CO2 (alcohol fermentation)
This addition of electrons is a process called Reduction
Krebs Cycle Diagram
Krebs Cycle Theory
Glycolysis Diagram
Glycolysis Theory
ETC Diagram
ETC Theory