Transcript triose phosphate

Respiration
To be able to explain
• The biochemistry of aerobic respiration
to show that glycolysis involves the
oxidation of glucose to pyruvate
• That pyruvate combines with coenzyme
A to produce acetylcoenzyme A
Aerobic Respiration
Define the following:
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Respiration
Breathing
Aerobic respiration
Anaerobic respiration
Aerobic Respiration
Respiration is the process that releases energy in organic
molecules such as sugars and lipids. Respiration takes place
in all cells all of the time
Breathing is the mechanical process that supplies oxygen to
the body for respiration and that removes carbon dioxide
produced. Breathing ventilates the gas exchange surfaces.
Aerobic Respiration is respiration with oxygen – most
organisms respire aerobically releasing a relatively large
amount of energy.
Anaerobic respiration is respiration without oxygen – some
organisms mainly bacteria can only respire anaerobically
others can switch to anaerobic when oxygen levels are low.
Aerobic Respiration
Aerobic respiration describes the cell
processes that require oxygen to release
energy from all organic molecules.
Respiration involves the breakdown of
many molecules from the food we eat.
Humans respire mainly sugars but also
some amino acids and fatty acids.
Aerobic Respiration
• For any chemical reaction to occur
energy is required to break bonds.
• The process of forming new bond can
either require energy or release energy
• For there to be a release of energy the
products of respiration must be at a
lower energy level than the reactants.
Aerobic Respiration
Energy in
molecules
Glucose and oxygen
CO2 +H2O
Time
Aerobic Respiration
• What is the basic equation for respiration?
• C6H12O6 + 6O2  6CO2 + 6H20 + ENERGY
• In reality cell respiration takes place in a
series of stages , these can produce a up to
36 molecules of ATP per molecule of
glucose
• The steps involved in respiration rely on a
series of redox reactions
• C6H12O6 + 6O2  6CO2 + 6H20 + 36 ATP
Aerobic Respiration
The process of aerobic respiration can
be divided into 4 distinct processes:
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Glycolysis
Pyruvate Oxidation
The Krebs cycle
The electron transport chain
Mitochondria
What are mitochondria?
Mitochondria are membrane-enclosed organelles
distributed through the cytosol of most eukaryotic
cells. Their main function is the conversion of the
potential energy of food molecules into ATP.
Mitochondria have:
•an outer membrane that encloses the entire
structure
•an inner membrane that encloses a fluid-filled matrix
•between the two is the intermembrane space
the inner membrane is elaborately folded with
shelflike cristae projecting into the matrix.
•a small number (some 5–10) circular molecules of
DNA
Mitochondria
Aerobic Respiration
Use the information on pages 11 and 12 to complete the
table
Stage
Site Within Cell
Overall process
Number of
ATP
molecules
produced
Aerobic Respiration
Stage
Site Within Cell
Overall process
Number of
ATP
molecules
produced
Glycolysis
Cytosol
Glucose is split into 2
molecules of pyruvate
2 per
glucose
molecule
Pyruvate
Oxidation
Matrix – inner
fluid of
mitochondria
Pyruvate is converted to none
acetyl co A
Krebs
Cycle
Electron
Transport
Chain
Acetyl co A drives a
cycle of reactions to
produce hydrogen
2 per turn
so 4 per
glucose
Inner membrane Hydrogen drives a
Up to 32
of mitochondria series of redox reactions per
to produce ATP
glucose
Four stages of aerobic
respiration
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Glycolysis
The link reaction
Krebs cycle
Electron transport chain
Glossary
• Phosphorylation
• the addition of phosphate
groups to a molecule.
• Glycolysis
• the ‘splitting’ of glucose.
• NAD
• nicotinamide adenine
dinucleotide
• coA
• coenzyme A
• acetyl coA
• acetylcoenzyme A
• TCA
• tricarboxylic acid
• FAD
• flavin adenine dinucleotide
Glycolysis
Glycolysis is a series of biochemical reactions by
which a molecule of glucose is oxidised to two
molecules of pyruvic acid.
Glycolysis serves two principal functions: generation of
high-energy molecules (ATP and NADH), and
production of a variety of six- or three-carbon
intermediate metabolites.
Glycolysis is one of the most universal metabolic
processes known, and occurs (with variations) in many
types of cells in nearly all types of organisms.
glucose
Glycolysis
phosphorylation
2ATP
2P
2ADP
Glucose phosphate
(6C)
glucose
Glycolysis
phosphorylation
2ATP
2P
2ADP
Glucose phosphate
(6C)
triose phosphate
(3C)
triose phosphate
(3C)
glycerate-3phosphate
glycerate-3phosphate
glucose
Glycolysis
phosphorylation
2ATP
2P
2ADP
Glucose phosphate
triose phosphate
glycerate-3-phosphate
2NAD+
H
2NADH
+ H+
pyruvate
triose phosphate
glycerate-3-phosphate
2ADP
+ 2Pi
2NAD+
2ATP
2NADH
+ H+
H
2ADP
+ 2Pi
2ATP
pyruvate
2 triose phosphate
2 glycerate-3-phosphate
2NAD+
H
2NADH
+ H+
2ADP
+ 2Pi
2ATP
2 pyruvate
•The triose phosphate is oxidised (loses an electron)
•Coenzyme NAD+ collects hydrogen ions forming 2
reduced NAD (NADH +H+ )
•4 ATP are produced, but 2 were used up at the
beginning, therefore there is net gain of 2 ATP
Overview of Glycolysis
Glucose
Glycolysis
in
2 ATP
2 NADH
cytoplasm
2 NADH
2 Pyruvate
4 ATP
To mitochondria
2 Pyruvate
ATP
For use in the cell for work
The Link reaction
• Literally ‘links’ glycolysis to the Krebs
cycle
• Sometimes treated as part of the Krebs
cycle
• Pyruvate enters the matrix of the
mitochondria
Pyruvate (3C)
Link Reaction
2NAD+
H
2NADH
+ H+
The pyruvate is
dehydrogenated (hydrogen
is removed) and the
hydrogen is transferred to
the hydrogen acceptor
NAD+ to form NADH + H+
CO2
The pyruvate is
decarboxylated (a molecule
of carbon is removed)
Pyruvate (3C)
Link Reaction
2NAD+
H
2NADH
+ H+
As 2 pyruvate
molecules are
formed from
glucose there
will be 2
molecules of
acetyl CoA
CO2
acetate (2C)
+
coenzyme A (CoA)
acetyl coenzyme A
(acetyl CoA)
NO ATP is produced
The Link reaction
pyruvate + CoA + NAD+ 
Acetyl CoA + CO2 + NADH + H+
Acetyl coenzyme A now enters the
Krebs cycle
The Link Reaction
• Make notes on mitochondria, glycolysis and
the link reaction on pages 11 – 13
• Break it down into chunks and make sure
you can remember how it starts and what the
products are
1. Describe how oxidation takes place in
glycolysis
2. What do the terms glycolysis and
phosphorylation mean?
3. Why is there only a net gain of 2ATP during
glycolysis?
4. How many molecules of ATP are produced in
the link reaction?
5. Where is acetyl coenzyme formed?
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Describe how oxidation takes place in glycolysis
removal of hydrogen/dehydrogenation;
by enzymes/dehydrogenases;
H accepted by NAD/reduced NAD formed;
What do the terms glycolysis and phosphorylation
mean?
glycolysis – splitting of glucose
Phosphorylation - addition of phosphate
Why is there only a net gain of 2ATP during
glycolysis?
4 produced but 2 used at beginning so net gain of 2
How many molecules of ATP are produced in the link
reaction?
none
Where is acetyl coenzyme formed?
Matrix of the mitochondria