Download Recap: structure of ATP

2.8: Cell respiration
Recap: structure of ATP
P
P
P
ribose
guanine
inorganic
phosphate
deoxyribose
thymine
organic
phosphate
nicotinamide
cytosine
adenine
flavine
ATP is a source of energy
Energy is released when ATP spits and forms ADP.
The energy from this split is immediately available.
A lot of the energy produced by cells ends up as
heat (environment) therefore the body needs a
continual source of energy.
Cell respiration
ATP
ADP
Cell processes (active)
Redox Reactions
• Oxidation
– Loss of electrons
– Loss of hydrogen atoms
OIL RIG
• Reduction
– Gain of electrons
– Gain hydrogen atoms
• If one substrate becomes oxidised another
becomes reduced. Oxidation and reduction
always occur together.
Co-enzymes
• During respiration, hydrogen atoms are
removed from substrate molecules in
oxidation reactions.
• This is catalysed by dehydrogenase
enzymes
• Co-enzymes are required to activate the
oxidation reactions in respiration
– Hydrogen atoms becomes attached to co
enzymes e.g. NAD
NAD
• Nicotinamide adenine dinucleotide (NAD)
– Is reduced when it has accepted two
hydrogen atoms with their electrons
– Operates in glycolysis, link reaction, the Krebs
cycle and the anaerobic pathways.
Co-enzyme A
• Function
– To carry ethanoate (acetate) groups made in
the link reaction, onto the Krebs cycle
– To carry acetate groups made from fatty acids
or amino acids onto the Krebs cycle
Glycolysis
• Ancient biochemical pathway
• Glucose (6C) is broken down into two
molecules of pyruvate (3C), with a net gain
of 2 ATP molecules.
• Occurs in the cytoplasm
• Glycolysis does not require oxygen
Glycolysis
• Pathway has four stages:
– Phosphorylation (movement of phosphate)
– Splitting of hexose 1,6-bisphosphate
– Oxidation of triose phosphate
– Conversion of triose phosphate to pyruvate
Products of Glycolysis
• Net gain of two ATP molecules
• Two molecules of reduced NAD
• Two molecules of pyruvate
Glycolysis video – detailed.
• http://highered.mheducation.com/sites/007
2507470/student_view0/chapter25/animati
on__how_glycolysis_works.html
Recap: where in the cell?
1. Glycolysis
1. Phosphorylation
2. Oxidation
2. Link reaction
3. Krebs cycle
4. Oxidative
phosphorylation
Matrix
Enzymes for Krebs cycle &
Link reaction
Outer membrane
Creates cellular compartment
Ribosome DNA
Expression of
mitochondrial genes
Intermembrane space
Protons pumped into space
by ETC
Cristae
Increase SA for oxidative phosphorylation
Inner mitochondrial membrane
ETC and ATP synthase
The Link reaction
The Link Reaction
• Pyruvate is actively transported into the
matrix of the mitochondria.
• Pyruvate is dehydrogenated and
decarboxylated to acetate in a series of
enzyme controlled reactions.
• Enzymes (you do not need to name
these!)
– Pyruvate dehydrogenase
– Pyruvate decarboxylase
Main points of The Link reaction
1. NAD accepts the hydrogen ions
2. Co-enzyme A accepts acetate to form
Acetyl CoA, to carry onto the Krebs
cycle.
3. Carbon dioxide is released
Recap: Krebs cycle
Krebs Cycle
• Takes place in the mitochondrial matrix
• Main stages
– Decarboxylation
• Removal of Co2
– Dehydrogenation
• reduction of NAD
– Substrate-level phosphorylation
• Production of ATP
Krebs cycle
• For each original glucose molecule there
are two turns of the Krebs cycle.
• Products
– 6 reduced NAD
– 2 reduced FAD
– 4 carbon dioxide
– 2 ATP
– Although oxygen is not used up in these
stages, they can not take place if it is absent –
they are aerobic stages
Krebs cycle video – detailed
• http://highered.mheducation.com/sites/007
2507470/student_view0/chapter25/animati
on__how_the_krebs_cycle_works__quiz_
1_.html
Products of Aerobic respiration
Product per
molecule of
glucose
Reduced NAD
Reduced FAD
CO2
ATP
Glycolysis Link
reaction
Krebs
cycle
Products of Aerobic respiration
Product per
molecule of
glucose
Reduced NAD
Glycolysis Link
reaction
Krebs
cycle
2
2
6
Reduced FAD
0
0
2
CO2
0
2
4
ATP
2
0
2
The electron transport chain
The electron transport chain
1. Hydrogen atoms released from NADH and FADH as
they are oxidised
2. Hydrogen atoms split into protons and electrons
3. Electrons move along the electron transport chain,
losing energy at each carrier
4. Energy is used to pump protons into intermembrane
space forming an electrochemical gradient
5. Protons move down electrochemical gradient back to
matrix via ATP synthase
6. Movement of protons drives synthesis of ATP from ADP
and inorganic phosphate
7. Protons, electrons and oxygen combine to form water,
the final electron acceptor
ETC video - detail
• http://highered.mheducation.com/sites/007
2507470/student_view0/chapter25/animati
on__electron_transport_system_and_atp_
synthesis__quiz_1_.html
Evidence for chemiosmosis
1. pH of intermembrane space is lower than pH of
matrix
– Proton gradient exists between intermembrane space and
matrix
2. Artificial vesicles created with proton pump proteins
resulted in ↓ pH in vesicle
– Proton gradient can be used to synthesise ATP
3. Mitochondria in pH8 solution produced no ATP
– Proton gradient can be used by mitochondria to make ATP
4. Uncouplers destroyed proton gradient in
mitochondria
– Proton gradient is required by mitochondria to make ATP