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Respiration
Energy





Can’t be created or destroyed but can be converted from one form to another
Chemical energy contained within food sources
Green plants convert light energy to chemical energy by the process of photosynthesis
All organisms are able to convert chemical energy to other forms

ATP- Adenosine Triphosphate
 Adenine, a nitrogenous base (as in DNA)
 Ribose, 5C sugar
 3 Phosphate, groups joined together

-Energy is required to combine ADP (Adenosine diphosphate) and P to form an ATP molecule which
is an endergonic reaction
-Energy is released when the ATP molecule is broken into ADP and P which is an exergonic reaction
-Processes which require energy- Active Transport, Muscle Contraction, Synthesis of Organic
Reactions
-ATP is an energy carrier in cells so may be called the universal energy carrier in living organisms
-ATP is actually produced on internal membranes of chloroplast and mitochondria
...

1
...
Link Reaction
3
...
Electron Transport Chain

Glycolysis



Occurs in cytoplasm, does not require oxygen
6C glucose is converted into two molecules of 3C Pyruvate;
-Conversion of glucose into a phosphorylated sugar
...
H’s are removed in this
process (REDOX) and picked up by the H acceptor NAD to form NADH2
(NAD is Nicotinamide adenine dinucleotide and is a coenzyme- works closely with an enzyme)

Energy is required to convert glucose into a
phosphorylated sugar i
...
2ATP is required

Therefore there is a net gain of 2 ATP form
glycolysis of one glucose molecule
...

Oxidised- Lost H2
Substrate level phosphorylation

Link Reaction
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

Occurs within the matrix of the mitochondria
Pyruvate still contains a lot of chemical energy
Pyruvate reacts with co-enzyme A to produce acetyl co enzyme A
Acetyl coenzyme A contains 2C from pyruvate molecule which reacts with 4C molecule to
form 6C product (Citric acid) which enters the Krebs Cycle
...


6C

4C
Co A

Oxidative Decarboxylation- Reactions in which the carboxylate group is removed and reduced
forming carbon dioxide
...

H is accepted by the acceptors NAD and
FAD
...

Small amount of ATP generated directly
via Krebs Cycle but the main product is
the reducing power of NADH2 and
FADH2
...

In the first two stages of the Krebs Cycle oxidative decarboxylation occurs when carbon
dioxide and hydrogens are removed and so the acetate fragment of the glucose molecule is
completely broken down and the 4C molecule is regenerated
...
But there are
two turns per glucose molecule as there are 2 acetyl co A molecules
So only a small amount of ATP is generated directly via Krebs Cycle but the main product is
the reducing power of the reduced coenzymes
...
(NADH2 produces 3ATP, FADH2 produces 1 ATP)

Oxygens role in respiration is at end of electron transport chain
Electrons coming off the electron transport chain are accepted by oxygen and joined by H +
to make water
 Without oxygen to accept electron all of the respiratory stages would soon became stuck in
their reduced state and ATP production in the mitochondrion would stop i
...
No link
reaction or Krebs Cycle- death by suffocation, cyanide which inhibits last enzyme in the
electron carrier chain
Some of energy is lost as heat as not all energy is captured in ATP molecules

Chemiosomosis
1
...
Respiratory chain activity results in protons being drawn into the electron transport chain
from internal matrix and then removed to the space between the inner and outer
membranes of mitochondrion
...

3
...
Thought that this occurs because electron
carriers involved are located in the inner membrane in such a position to allow only uptake
from the inside and loss to the outside
4
...
Therefore energy is required to maintain the pH gradient
...

5
...
This gradient can be used to work; referred to as protonmotive force PMF
...
Protons move back across the membrane, down their concentration gradients, though
specific sites where enzyme ATP Synthesise
...

PMF can power certain processes other than ATP synthesis- transport of small molecules across
mitochondria and rotation of bacteria flagella
...
Explains why the membrane needs to be impermeable to protons from
outside to inside to form pH gradient
...
The energy yield is small so cannot be maintained, 2 ATP compared to 38
...
Pyruvate becomes the acceptor and espending
on the metabolic pathways within the cells the end products of anaerobic respiration will be ethanol
and carbon dioxide or lactic acid
...
Lactate has to be removed from muscle cells by the blood to
prevent fatigue
...

Anaerobic
Aerobic
Substrate
Glucose
Glucose
Degree of Breakdown
Partial
Full
Products
Carbon dioxide + Ethanol
Carbon Dioxide + Water
Lactate
Site of reactions
Cytoplasm
Cytoplasm and Mitochondrion
matrix and inner cristae
Energy Produced
Low
High
Number ATP molecules 2
38
Stages involved
-Glycolysis
-Glycolysis
-Reduction of Pyruvate
-Link Reaction
-Krebs Cycle
-Electron Transport Chain
Oxygen required?
No
Yes- 6O2
Equation
Glucose >>>> Lactate + 2ATP
Glucose + Oxygen >>>> Carbon
Glucose >>>> Ethanol + Carbon
Dioxide + Water + 38ATP
dioxide +2ATP

Respiratory Substances
Cell respiration involves oxidation of a substrate to yield chemical energy ATP
...

Carbohydrates;
 First choice for most cells- brain cells of mammals cannot use anything else
 Polysaccharides are hydrolysed to monosaccharide’s before they enter the respiratory
pathway
...
Glycogen in animals >>>> Glucose

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