Download Bettleheim Chapter 20

Biochemistry
Bioenergetics:
How the body converts
food to energy
Bioenergetics
 Metabolism:
The sum of all Chemical
Reactions involved in maintaining the
dynamic state of the cell
– Catabolism - breaking down of molecules to
supply energy
– Anabolism - synthesis of molecules
– Biochemical Pathway - a series of consecutive
chemical reactions
Common Catabolic Pathway
Conversion of FOOD to ATP:
 FOOD
 C4
produces C4 and C2 fragments
and C2 fragments enter Citric Acid Cycle
 CO2,
NADH, FADH2, are produced
 Electron
Transport produces ATP
inner
membrane
C2
C4
C2
C4
CO2
CO2
C2
CO2
Citric Acid
Cycle
outer
membrane
ATP
e- transport
FADH2
O2
e- transport
NADH
O2
ATP
ATP
ATP
H2O
ATP
Cells and Mitochondria
Components of a typical cell:
 nucleus
- replication of cell begins here
 lysosomes - remove damaged cellular components
 Golgi bodies - package and transport proteins
 organelles - specialized structures with specific function
 mitochondria - common catabolic pathway
Cells and Mitochondria
Cells and Mitochondria
Mitochondria
 Mitochondria
– Two membranes
– Common Catabolic Pathway
– Enzymes located in folds or “Crista”
– Transport thru the inner membrane occurs with
the help of Protein Gates
Mitochondrion
Common Catabolic Pathway
2 Parts:
 Citric Acid Cycle
– or Tricarboxylic Acid Cycle
– or TCA cycle
– or Kreb’s Cycle
 Oxidative
Phosphorylation
– or Electron Transport
– or Respiratory Chain
1
2
Compounds - ADP
 Adenosine
diphosphate (ADP)
NH2
N
O
O
- O P O P O CH
2
O-
O-
diphosphate
N
N
adenine
N
O
ribose
OH OH
adenosine
adenosine diphosphate
Compounds - ATP
 AMP,
ADP, ATP
High energy phosphate anhydride bonds
O
O
O
O P O P O P O CH2
OOOtriphosphate
NH2
N
N
N
O
OH OH
N
Compounds - ATP
 ATP
– We make about 88 lbs. of ATP a day!!!
– Used for:
» muscle contraction
» nerve signal conduction
» biosynthesis
NH2
N
O
O
O
O P O P O P O CH2
OOO-
N
N
O
OH OH
N
Fig. 26.6, p.651
Compounds - Redox
 NAD+
and FAD
– Oxidizing agents
– Actually coenzymes
– Contain an ADP core (part of R or R’)
O
C NH2
N+
R
NAD+
H3C
N
H3C
N
R'
FAD
O
C
NH
C
N
O
Compounds - Redox
 NAD+
is converted to NADH
O
C NH2
H O
C NH2
H
+ H+ + 2 e-
N+
R
Oxidized form
N
R
Reduced form
to ET
Compounds - Redox
 FAD
is converted to FADH2
O
H3C
H3C
N
N
R'
Oxidized form
C
N
NH
C
+ 2 H+ + 2 e-
O
H3C
H3C
H
N
N
R'
O
C
NH
C
N
O
H
Reduced form
to ET
Compounds
 The
Acetyl carrying group - Acetyl coenzyme A
 Carrying
handle is Pantothenic Acid and
Mercaptoethylamine
O
CH3 C S CoA
acetyl CoA
Coenzyme A
NH2

N
OH CH3
O
N
O
HS CH2 CH2 NH C CH2 CH2 NH C CH C CH2 O P O P O CH2
O
O
mercaptoethylamine
CH3
pantothenic acid
O
CH3 C S CoA
acetyl CoA
O-
N
O-
O
- O PO OH
3
ADP
N
Coenzyme A
NH2

2C
3C
4C
OH CH3
N
O
N
O
HS CH2 CH2 NH C CH2 CH2 NH C CH C CH2 O P O P O CH2
O
O
mercaptoethylamine
CH3
pantothenic acid
O
CH3 C S CoA
acetyl CoA
O-
N
O-
O
- O PO OH
3
ADP
N
Fig. 26.8, p.652
http://www.youtube.com/watch?v=iXmw3fR8fh0
http://www.youtube.com/watch?v=lvoZ21P4JK8
http://www.youtube.com/watch?v=A1DjTM1qnPM
http://www.youtube.com/watch?v=FgXnH087JIk
Citric Acid Cycle
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
 Acetyl
CoA contains a 2 carbon fragment that
is carried into the Citric Acid Cycle
 Also called the:
– Tricarboxylic Acid Cycle
– TCA Cycle
– Kreb’s Cycle
C2
C4
C6
CO2
 Acetyl
group is
split out as CO2
C5
C4
CO2
Citric Acid Cycle
 Step
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
1
– oxaloacetate will show up in last step
– acetyl CoA is the THIO ESTER of acetic acid
(CoA is Co Enzyme A)
O
COOO C
CH2
O
+
CH3 C S-CoA
COO-
citrate
synthetase
C S-CoA
CH2
HO C COOCH2
COO-
oxaloacetate
acetyl CoA
citryl CoA
Citric Acid Cycle
 Step
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
1B
– citrate or citric acid produced
– citrate has 6 C (How many acid groups?)
O
C S-CoA
CH2
HO C COOCH2
+H 2 O
C OOCH2
HO C COOCH2
COO-
COO-
citryl CoA
citrate
+ HS-CoA
Fig. 26.8, p.652
Citric Acid Cycle
 Step
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
2
– dehydration to cis-Aconitate
– hydration to isocitrate
– enzymes required for each Rx
C OOCH2
HO C COOCH2
COOcitrate
aconitase
-H2 O
C OOCH2
C COOCH
COOcis-aconitate
aconitase
+ H 2O
C OOCH2
H C COOHO CH
COOisocitrate
Fig. 26.8, p.652
Citric Acid Cycle
 Step
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
3
– oxidation and decarboxylation
– CO2 is from the
???
C OOCH2
H C COOHO CH
COOisocitrate
isocitrate
dehydrogenase
NAD+
C OOCH2
H C H
C O
NADH
COO-ketoglutarate
+ CO 2
Fig. 26.8, p.652
Citric Acid Cycle
 Step
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
4
– Where did the CO2 come from???
C OOCH2
H C H
+ SCoA
C O
COO-
-ketoglutarate
complex
enzyme
system
NAD +
NADH
O
C SCoA
CH2
+ CO 2
H C H
C OOsuccinyl CoA
Fig. 26.8, p.652
Citric Acid Cycle
 Step
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
5
– GTP is Guanosine triphosphate (as good as ATP!)
O
C SCoA
CH2
H C H + GDP
C OOsuccinyl CoA
complex
enzyme
system
C OOCH2
H C H
C OOsuccinate
+
GTP
+ SCoA
Fig. 26.8, p.652
Citric Acid Cycle
 Step
6
– Oxidation with FAD
– Fumaric Acid is trans-Fumaric Acid
– Barbiturate is an inhibitor of Succinate dehydrogenase
C OOCH2
succinate
dehydrogenase
H C H
C OOsuccinate
C OOCH
C H
FAD
FADH2
C OOfumarate
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Fig. 26.8, p.652
Citric Acid Cycle
 Step
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
7
– hydration reaction
– fumarase is enzyme
C OOCH
C H
+ H 2O
fumarase
C OOCH OH
CH 2
C OO-
C OO-
fumarate
malate
Citric Acid Cycle
 Step
8
– oxidation using NAD+
– product is oxaloacetate!
C OOCH OH
malate
dehydrogenase
CH2
CH2
C OOmalate
C OOC O
NAD+
NADH
C OOoxaloacetate
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Fig. 26.8, p.652
Electron (and H ) Transport
+
 End
products of the Citric Acid Cycle
Reduced (or spent) Coenzymes
– NADH
– FADH2
 Carry H+ and e- and yield energy when
combining with oxygen:
4 H+ + 4 e- + O2
2 H2O
Electron (and H ) Transport
+
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
 Many
Enzymes are involved in ET
 Enzymes are imbedded in inner membrane of
the mitochondria
 Enzymes are in a particular sequence
– each accepts electrons
– increasing affinity for electrons
 Final
acceptor of electrons is
molecular O2 to make water
O2
Fig. 26.10, p.656
Electron Transport chain - youtube
http://www.youtube.com/watch?v=xbJ0nbzt5Kw
http://www.youtube.com/watch?v=Idy2XAlZIVA
http://www.youtube.com/watch?v=A32CvcfA_K0&feature=PlayList&
p=F09BC040A0B953F8&playnext=1&playnext_from=PL&index=10
http://www.youtube.com/watch?v=1engJR_XWVU
Electron (and H ) Transport
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
+
 Many
Enzymes are involved in Oxidative Phosphorylation
Lipid bilayer
Flavoprotein
NADH
NAD+
overall 3 ATP
produced
2 H+
FeS
protein
FADH2
2 H+
Q
enzyme
FAD
b
b
2 H+
c1
c
a3
O2-
ATPase
cytochromes
overall 2 ATP
produced
2 H+ + 2 e- + 1/2 O2
a
O2
ATP
H2O
The Energy Yield from a C2
 Each
NADH produces
 Each FADH2 produces
3 ATP
Indirect
(from ET)
2 ATP
(Each pair of H+ produces
1 ATP)
 For each C2 unit (acetyl CoA) we produce...
– 1 GTP directly (same as
– 3 NADH in ET (3 x 3 =
– 1 FADH2 in ET (1 x 2 =
1 ATP) from step 5 TCA
9 ATP) Indirect
2 ATP) Indirect
For a total of .....................
12 ATP
(and some waste CO2)
$
Conversion of ATP
How does the body utilize this Chemical Energy?
 Conversion to Other Forms
– biosynthesis
 Electrical
Energy
– ion gradients (K+, Na+)
 Mechanical
Energy
– muscle contraction
 Heat
Energy
– maintain 37 oC or 98.6 oF
Muscle Contraction
Chemical Energy converted to Mechanical
Energy:
 Thick (myosin) and thin (actin) filaments
 Hydrolysis of ATP causes the interaction of the
filaments (muscle contraction)
contraction