Download Energy Production - University of Massachusetts Amherst

Energy Production
Energy Production
• The body extracts energy from stored
reserves to accomplish tasks requiring
energy:
1.
2.
3.
basic maintenance and repair, e.g.
circulation, respiration, ion gradients,
synthesis, etc.
digestion/absorption
physical activity
Adenosine Triphosphate
• All energy must eventually be in the form
of ATP in order for it to be used for cell
metabolism. ATP is the energy "currency"
of the cell.
• Why?
ATP is the only source of energy that the
body can use.
Stored energy (e.g. fat, glycogen, creatine
phosphate) must first be converted to ATP
before the body can actually use it.
Laundromat Analogy:
The work that must be done (the laundry) can only be paid for
(fueled by) quarters. So, you go to the laundromat with 5,000
loads of laundry. In your pocket you have a roll of quarters.
You realize that this will not be enough money, but since the
quarters are heavy you only bring one roll. You also bring a
handful of $1 bills and a $100 bill because your wallet was so
full of singles you couldn’t fit it in your back pocket. Just in
case you don’t have enough cash, you also bring your Visa
Checkcard with you. However, there is an overdraft penalty
on your Visa Checkcard, so if the money is not replaced very
quickly you must pay for your overdraft.
Laundromat
Human Systems
Quarters
Creatine Phosphate, ATP
$1
Glycogen, Blood Glucose
$100
Stored Fat
Visa Checkcard
Protein
Quarters = ATP
•
•
•
•
Immediate energy source (ATP/CP)
Hydrolysis reaction takes place without oxygen.
The amount of ATP/CP stored is very limited.
Provides energy for 8-12 seconds of intense
exercise.
• Body pool of ATP "turns over" 5000 times/day!
ATP ADP + Pi + energy
PCr + ADP  ATP + creatine
$1 = glycogen/glucose
• Glycogen/glucose is like having dollar bills
that can be broken down to quarters in a
change machine.
• Much greater capacity ($1) than carrying
quarters.
• The human body stores ~350 g of
glycogen, not enough to sustain long
duration of exercise or a period of time
without food.
• Non-oxidative metabolism: requires no
O2 and results in lactate accumulation (like
dimes and nickels that the liver can turn
lactate back into glucose).
• Oxidative metabolism: requires O2 .The
amount of ATP produced from the
breakdown of a molecule of glucose is ~30
- 36 ATP.
$100 = Stored Fat
• Fat stores are the energy sources for rest
and prolonged activity at lower levels of
exertion.
• Breaking down fat is a SLOW process. Just
as getting change for the $100 bill may be
take a while, mobilizing fat stores to be
used to meet cellular energy demands also
takes longer than using glucose, ATP, or
PCr.
• The amount of ATP generated from a
single molecule of palmitate (a common
fatty acid) is ~108 - 129 ATP.
• Fat can only be oxidized in the presence
of oxygen.
VISA = Protein
• When either carbohydrate intake or overall
energy intake is low; proteolysis (the
breakdown of protein – mostly from lean
muscle) provides energy for biologic work.
• VISA: using protein as energy supplements
the ATP/PCr, glycogen and fatty acids that
provide the majoroty of the ATP.
Amino acids, which combine to form proteins,
consist of a carbon backbone and an amine
group. If the amine group is removed
(deamination) the resulting molecule may
enter into the energy producing pathways
Additionally, amino acids can be converted
IN THE LIVER to alanine and then to glucose
in a process called gluconeogenesis.
CHO has ~4kcal/g
Glycogen is stored with 2.7- 3.0 grams of
water per gram of glycogen so it is only about
30% useable energy
So the stored CHO actually only has about 1.4
kcal per gram or about 600 kcal/pound
Fat is about 90% triglyceride and 10% water.
TG contains 9 kcal/g * 90% = about 8 kcal/g
for stored fat or about 3500 kcal/pound
So energy stored as CHO (glycogen) is 6
times as heavy as energy stored as FAT.
If humans were to store energy as glycogen
instead of fat we would be forced to carry at
least 100 extra pounds just to have the same
amount of energy available.
Protein
Fat
CHO
ATP
produced
Amino
Acids
Pyruvate
Fatty Acids
Acetyl-CoA
Krebs Cycle
and ETC
ATP
produced