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Bioenergetic Processes

KIN 416 - Berry College - Dept. of Kinesiology
by

David Elmer

on 8 September 2016

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Transcript of Bioenergetic Processes

Anaerobic Energy
The rate of ATP replenishment can be easily met by aerobic energy production in cells that only have gradual increases in energy
But in muscles, the energy requirement can increase 100x almost instantly
This is a problem, because there's only about 4 mmol ATP stored in muscle (~3 sec worth)
So you must replenish ATP quickly.
ATP-PC (Phosphagen) System
In a nutshell:
ADP + PCr + H
ATP + Cr
Creatine Kinase
note that the reaction goes both ways - law of mass action
About 18-20 mmol of PCr stored in muscle
+
Creatine Kinase
highest enzyme activity in the entire skeletal muscle
located on the contractile proteins, sarcolemma, SR membrane, in the mitochondria, and free in the cytosol
Wherever ATP is needed, CK is there.
Due to extremely high activity of CK, ATP can be replenished during bursts of intense exercise -
at the expense of PCr
intensity PCr
recovery of PCr - half-time ~ 30 sec
- full recovery ~ 6 min
accomplished by aerobic ATP production
Adenylate Kinase (Myokinase)
ADP + ADP
ATP + AMP
Adenylate Kinase
Increase in Pi, ADP, AMP, pH
Glycolysis
Metabolic pathway beginning with glucose or glycogen
Net production of 2 ATP from glucose and 3 ATP from glycogen
2 classifications:
(based on end product)
Aerobic glycolysis -
pyruvate
Anaerobic glycolysis -
lactate
pyruvate + NADH + H
+
LDH
lactate + NAD
+
LDH
Lactate dehydrogenase
Most active enzyme in metabolic pathway
5 different isoforms:
H MH M H M H M
4
3
2
2
3
4
H =
Heart
M =
Muscle
*can be altered with training
Different fiber types have different isoforms, based on needs of the muscle cells...
Why convert pyruvate to lactate?
Glycolysis can produce pyruvate faster than it can be used for aerobic energy production
excess precursor for ATP production

Build-up of NADH in cytosol inhibits glycolysis
so...
Converting pyruvate to lactate regenerates NAD, then leaves the cell so it can be used as fuel elsewhere
+
PFK-1
*rate-limiting enzyme of glycolysis
F-6-P + ATP
F-1,6-BP + ADP
stimulated by:
inhibited by:
AMP
ADP
Pi
increased pH
ATP
PCr
citrate
decreased pH
glucose
glucose-6-phosphate
ATP
ADP
hexokinase
glycogen
glucose-1-phosphate
phosphoglucomutase
phosphorylase
Krebs Cycle
... aka TCA cycle
... aka Citric acid cycle
Lipolysis
Fatty acids cleaved from glycerol to form free fatty acid (FFA)
FFA enter mitochondria and begin beta-oxidation spiral
Stored in adipose tissue, liver, and muscle
Isocitrate Dehydrogenase
*rate limiting enzyme of Krebs cycle
isocitrate + NAD
IDH
a-ketoglutarate + NADH + CO
+
2
Stimulated by:
Inhibited by:
ADP
calcium
NAD
ATP
NADH
5 NADH from glycolysis and Krebs cycle
1 FADH from Krebs cycle
2
Electron Transport Chain
occurs across/along the inner membrane of the mitochondria
electrons from NADH and FADH are transferred along a series of pumps that move H ions into the intermembrane space
when H ions move back into the mito matrix, ATP is generated
chemiosmotic hypothesis
2
+
+
Complex I
4 H
+
NADH
NAD
+
2 e-
Complex II
FADH
FAD
+
Coenzyme Q
2 e-
Complex III
2 e-
4 H
+
Cytochrome C
*rate limiting step of ETC
stimulated by:
ADP
Pi
inhibited by:
ATP
2 e-
Complex IV
2 H
+
2 e-
Complex V
H
H
H
H
H
H
H
H
+
+
+
+
+
+
+
+
ADP
ATP
2 e-
H
+
O
2
H O
2
ADP
MITOCHONDRIA
CYTOSOL
Start
0 sec

30 sec
3 min
Mitochondrial CK
ATP
Cr
PCr
Cytosolic CK
"Fire brigade"
ATP
ADP
Contraction
Intermembrane space
Matrix
Cytosol
2
PCr
Cr
ADP
ATP
Cr
PCr
aka Ubiquitin
oxygen not required
metabolism
all the chemical reactions in the body
breakdown and synthesis of molecules
catabolism
anabolism
when food is broken down into usable energy
=
bioenergetics
Carbohydrates
1 g of carbs = 4 kcal of energy
monosaccharides
disaccharides
polysaccharides
"simple sugars"
Glucose
2 conjoined monosaccharides
Sucrose, Maltose
3 or more conjoined monosaccharides
Glycogen
used for anaerobic & aerobic energy production
Fats
1 g of fat = 9 kcal of energy
*not soluble in water, so must have a transporter in blood, etc.
Fatty acids
Triglycerides
Phospholipids
Steroids
primary type used for energy production
storage form of fatty acids
long carbon chain with carboxyl end group
3 fatty acids attached to a glycerol molecule
primary component of cell membranes and nerve insulation
not metabolized for energy production
Aid in synthesis of hormones and give structure to cellular components
not used for energy production
Proteins
1 g of protein = 4 kcal of energy
must be broken down into amino acids to contribute to energy production
* NOT A PRIMARY SOURCE OF ENERGY
energy released in the breakdown of one molecule is often used to synthesize another molecule
"exergonic" or "exothermic"
"endergonic" or "endothermic"
enzymes
regulate speed of reactions
do not cause reactions
(catalyze)
work by lowering the activation energy
factors affecting enzyme activity:
temperature
pH
Efficiency of system
32 moles ATP/mole glucose x 7.3 kcal/mole ATP
686 kcal/mole glucose
= 34%
66% lost as heat
(food)
(ATP)
metabolic pathway beginning with triglycerides (fats)
beta-oxidation spiral
1 NADH + 1 FADH per spin
2
acetyl-CoA
carnitine transferase
*rate-limiting step
*rate-limiting step
sources of
aerobic
energy
maybe around 2% of total energy production
up to 10% at the end of a long-duration, high-intensity exercise bout
anaerobic out here!
aerobic in here!
translocation
mobilization
circulation
uptake
activation
- breakdown of adipose
- from adipose to muscle
- into muscle from blood
- prep for catabolism
additional steps get rid of the AMP
protein...
turned into pyruvate, acetyl-CoA, Krebs cycle intermediates, or glucose
in extreme heat
this is why we breathe
*
*
*
*
*
*
Full transcript