An introduction to energy production in biological systems

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An introduction to energy production in
biological systems
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Text Book
Freeman, 3rd edition Chapter 9 Cellular
Respiration 171- 196 Any other plant/ animal
biology text will have details
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topics

• energy currency
• oxidation reduction reactions
• energy sources
• energy use
• energy supply

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1. Energy currency
H2O
hydrolysis
adenine
ribose
ATP
ADP
AMP
condensation
Biological currency -- energy derived from the
closely spaced -ve charges associated with P
groups. Hydrolysis results in ATP -gt ADP -gt AMP
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The perspective
ADP
RATE OF TURNOVER?
1020 molecules per second, equivalent to a
turnover rate of ATP of 65 kg per day.
humans turn over OWN WEIGHT in ATP each day !
ATP
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ATP synthase - the rotary engine in the cell
Masasuke Yoshida, Eiro Muneyuki and Toru
Hisabori Nature Reviews Molecular Cell Biology
Volume 2 September 2001 669
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• What are the requirements for respiration?
• Substrates e.g. glucose
• Enzymes
• temperature (Km)

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2. how is energy formed?
Biologically, the process of oxidizing food
molecules, like glucose, to carbon dioxide and
water (in respiration) forms energy.

• Oxidation is the loss of electrons or an increase
  in oxidation state by a molecule, atom, or ion.

Reduction is the gain of electrons or a
decrease in oxidation state by a molecule, atom,
or ion.

• The energy released is trapped in the form of ATP
  for use by all the energy-consuming activities of
  the cell.
• Synthesis of ATP from ADP requires energy (7.3
  kcal/mole)

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Do redox reactions cost a lot?

• Cellular respiration is the oxidation of glucose
  (C6H12O6) to CO2 and the reduction of oxygen to
  water. The summary equation for cell respiration
  is
• The process of cell respiration also depends
  heavily on the reduction of NAD to NADH and the
  reverse reaction (the oxidation of NADH to NAD).
  The Net yield of energy is about 38ATP.
• C6H12O6 6 O2 ? 6 CO2 6 H2O energy 38
  ATP
• PHOTOSYNTHESIS is essentially the reverse of the
  redox reaction in cell respiration, and the
  generalized equation is-
• 6 CO2 6 H2O light energy ? C6H12O6 6
  O2
• reduction of carbon dioxide into sugars and the
  oxidation of water into molecular oxygen.

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Something to remember.
Photosynthesis may produce molecules with a large
energy potentials, BUT they (glucose and sucrose)
are very expensive to produce at 54 mol ATP per
mol of glucose!
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3,4 5sources, uses and supply
??
glycolysis
TCA cycle (tricarboxylic, /citric acid cycle)
Calvin/Benson/Bassham cycle
electron transport chemiosmosis
Cyclic, non-cyclic photophosphorylation
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heterotrophs

• All other organisms, including ourselves, are
  heterotrophs.
• We secure all our energy from organic molecules
  taken in from our surroundings ("food").
• Although heterotrophs may feed partially (as most
  of us do) or exclusively on other heterotrophs,
  all the food molecules come ultimately from
  autotrophs.
• We may obtain food from animal or vegetable
  sources.

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heterotrophs

• Heterotrophs degrade some of the organic
  molecules they take in (catabolism) to make the
  ATP that they need to synthesize the others into
  the macromolecules of which they are made
  (anabolism).

Glycolysis, Krebs, ETS
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autotrophs

• Green plants, algae, and some bacteria are
  autotrophs ("self-feeders").

• Most of them use the energy of sunlight to
  assemble inorganic precursors, chiefly carbon
  dioxide and water, into the array of organic
  macromolecules of which they are made.

• The process is photosynthesis and photosynthesis
  generates the ATP needed for the anabolic
  reactions in the cell.
• 6 CO2 6 H2O light energy ? C6H12O6 6 O2

glycolysis, Krebs, ETS cyclic/ noncyclic
photophosphorylation
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Things to look up/study
Words anabolism, anabolic, catabolism,
catabolic, cyclic, chemiosmosis, carbon
reduction, dephosphorylation, oxidation, redox,,
noncyclic, phosphorylation.
Cycles glycolysis, TCA, Calvin, cyclic,
noncyclic photophosphorylation, ETS.
here. Tuesday 4 May
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Respiration
some slides reordered
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Key Concepts
In cells, the endergonic reactions needed for
life are paired with exergonic reactions require
ATP.
Cellular respiration produces ATP from molecules
with high potential energyoften glucose.

• Glucose processing has four components

(1) Glycolysis
(2) Pyruvate processing
(3) Krebs cycle
(4) Electron transport coupled with oxidative
phosphorylation
endergonic absorb energy exergonic, release
energy

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1
eat and energize
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Complex carbohydrates O2 CO2 water
Energy
cytoplasm
mitochondrion
L2
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Intermediates in Carbohydrate Metabolism
Pathway for synthesis of RNA, DNA
Fats
Phospholipids
Fatty acids
Several intermediates used as substrates in amino
acid synthesis
Glycogen or starch
KREBS CYCLE
Glucose
Acetyl CoA
Pyruvate
GLYCOLYSIS
Lactate (from fermentation)
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Glycolysis and beyond..
the glycolytic pathway is, arguably one of the
most fundamental biochemical pathways and was
discovered quite by accident! Its elucidation
must rank as one of the great achievements in the
history of biochemistry.
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to other metabolic processes
1 x 6C
to mitochondria, via the malate - aspartate
shuttle
Use 2 x ATP
Synthesize 4 x ATP
Gain 2 x ATP
2 x 3C
feedback inhibition under HIGH ATP i.e. if the
cell does not need ATP, the process is slowed
down. A really neat response, prevents
overproduction of pyruvate! (see page 182).
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Krebbs
SUMMARY OF CELLULAR RESPIRATION
Oxidative phosphorylation
ETC
H
H
H
H
H
H
Electrons
H
H
H
H
H
H
H
H
6 NADH
2 NADH
2 NADH
2 FADH2
O2
H2O
GLYCOLYSIS
26 ADP
KREBS CYCLE
2 Pyruvate
Glucose
2 Acetyl CoA
4 CO2
2 CO2
2 ATP
2 ATP
26 ATP
Maximum yield of ATP per molecule of glucose
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Cytoplasm
Mitochondrion
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Krebs (Citric Acid) cycle -- Overview
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The Krebs Cycle Carbons, ATP and NADP energy
transfers
pyruvate (3-C) NAD Acetyl-CoA (2-C) CO2
NADH
CoA
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The Krebs Cycle Completes the Oxidation of Glucose
The two red carbons enter the cycle via acetyl CoA
THE KREBS CYCLE
ETC
Pyruvate
Acetyl CoA
Citrate
Isocitrate
In each turn of the cycle, the two blue carbons
are converted to CO2
All 8 reactions of the Krebs cycle occur in
the mitochondrial matrix, outside the cristae
?-Ketoglutarate
Oxaloacetate
ETC
ETC
In the next cycle, this red carbon becomes a blue
carbon
Succinyl CoA
Malate
here L2
Succinate
Fumarate
ETC
READ the summary on notes page!
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another view of the citric acid cycle
Sourcehttp//www.elmhurst.edu/chm/vchembook/612c
itricsum.html
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Electron Transport
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2e-
Electron Transfer
Inputs
1. NADH 3 ATP,
High energy
2. FADH2 2 ATP
reduced form
oxidized form
ROLE PLAYERS
FMN flavinemononucleotide CoQ coenzyme Q Cyt
b cytochrome b Cyt c cytochrome c Cyt a
cytochrome a Cyt a3 cytochrome a3
Low energy
molecular oxygen reduced to water
NAD Nicotine Adenine Dinucleotide FAD Flavine
Adenine Dinucleotide
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Redox reactions occur in ETC
The electron transport chain takes place in
the inner membrane and cristae of the
mitochondrion
FMN
Nucleotide with a flavin- containing group
Fe
S
Protein with an iron-sulfur group
?
Cyt
Protein with a heme group (a cytochrome)
Q
Ubiquinone
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Chemiosmosis

• The ETC pumps protons from the mitochondrial
  matrix to the intermembrane space.
• The proton-motive force from this electrochemical
  gradient can be used to make ATP in a process
  known as chemiosmosis.

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How does it Work?
molecular oxygen reduced to water
http//en.wikipedia.org/wiki/FileETC.PNG
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How Is the ETC Organized?
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The Structure of ATP Synthase
A vesicle formed from an inside-out mitochondria
l membrane
Membrane proteins with a lollipop-shaped stalk
and knob
The FO unit is the base the F1 unit is the knob.
THE STRUCTURE OF ATP SYNTHASE
H
H
H
Intermembrane space
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
FO unit
Stalk
Mitochondrial matrix
H
F1 unit
ADP Pi
ATP
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The Structure of ATP Synthase
A vesicle formed from an inside-out mitochondria
l membrane
Membrane proteins with a lollipop-shaped stalk
and knob
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THE STRUCTURE OF ATP SYNTHASE
H
H
H
Intermembrane space
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
FO unit
H
Stalk
Mitochondrial matrix
H
F1 unit
ADP Pi
ATP
The FO unit is the base the F1 unit is the knob.
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FROM ATP synthase - the rotary engine in the
cell Masasuke Yoshida, Eiro Muneyuki and Toru
Hisabori Nature Reviews Molecular Cell Biology
Volume 2 September 2001 669
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ATP synthase - the rotary engine in the cell
Masasuke Yoshida, Eiro Muneyuki and Toru
Hisabori Nature Reviews Molecular Cell Biology
Volume 2 September 2001 669
39
A Summary of Cellular Respiration
SUMMARY OF CELLULAR RESPIRATION
Oxidative phosphorylation
ETC
H
H
H
H
H
H
Electrons
H
H
H
H
H
H
H
H
6 NADH
2 NADH
2 NADH
2 FADH2
O2
H2O
GLYCOLYSIS
26 ADP
KREBS CYCLE
2 Pyruvate
Glucose
2 Acetyl CoA
4 CO2
2 CO2
2 ATP
2 ATP
26 ATP
Maximum yield of ATP per molecule of glucose
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Cytoplasm
Mitochondrion
NB!! remember other sources say up to 36-38
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Furnishing Substrates for Cellular Respiration
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Intermediates in Carbohydrate Metabolism
Pathway for synthesis of RNA, DNA
Fats
Phospholipids
Fatty acids
Several intermediates used as substrates in amino
acid synthesis
Glycogen or starch
KREBS CYCLE
Glucose
Acetyl CoA
Pyruvate
GLYCOLYSIS
Lactate (from fermentation)
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Glucose Is the Hub of Energy Processing in Cells
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The Krebs Cycle Carbons, ATP and NADP energy
transfers