Download Metabolism

Metabolism
The sum of all chemical reactions
within the living cells
• Anabolism
• Catabolism
• Building new
structures
• Requires energy
• Smaller molecules 
larger molecules
• Breakdown of
substances
• release of energy
• Larger molecule 
smaller molecules
Nutrient Pool
• Source of substrates : amino acids, lipids,
sugars, vitamins, minerals
Stored in the liver,
and delivered to all
tissues/cells via
blood
Cells produce energy in the
mitochondria
Adenosine Triphosphate [ATP]
Carbohydrate Metabolism
• Glycolysis breaking sugar into pyruvic acid
occurs in cytoplasm of cell. O2
nondependent
• TCA or Krebs Cycle O2 dependant. Occurs in
mitochondria
• Electron transport system [respiratory chain]
occurs in mitochondria
• Anaerobic metabolism  lactate production
Activation Energy
• Need to ‘spend’ energy to make energy
• To begin the process of Glycolysis – the
cell uses 2 ATP. The process of glycolysis
yields 4 ATP – net gain 2 ATP
+4
-2
+2
ATP
ATP
ATP
from phosphorylation
activation energy
net gain to cell
Glycolysis: the Lysis or breaking apart of glucose
occurs in the cytoplasm of all cells. This process
does not require oxygen. It is therefore referred to as
an anaerobic process.
The net yield of energy in
glycolysis is 2 ATPs & 2 NADH
NADH = Nicotinamide adenine dinucleotide
The production of lactate is a common fate of pyruvate in skeletal muscles,
which have been working very hard and have used up all their oxygen but are
still producing pyruvate. As the lactate (lactic acid) builds up in the muscles
they will feel sore
Intermediate Step
• The First Step in the Krebs Cycle is to
convert pyruvate into a two-carbon
fragment, then attach it to another
coenzyme known as coenzyme A or COA. The enzyme that accomplishes thus is
a large enzyme known as the pryruvate
dehydrogeneses complex
• Gives off 1 NADH for each acetyl CoA
produced [ 2 NADH total/glucose]
Krebs Cycle
• Cycle goes thru a
revolution for each
Acetyl CoA that
enters [ 2 Acetyl CoA
are formed from each
glucose molecule]
• Will give off ATP,
NADH & FADH as
well as CO2
Energy Yield of TCA Cycle
1 ATP produced by each turn of cycle
Each turn of cycle also produces 3 NADH
& 1 FADH2
FADH2 = flavin adenine dinucleotide
NADH and FADH2 will then go into the
electron transport system to yield ATP
2 turns of cycle are completed for each
glucose molecule
2 ATP + 6 NADH +2 FADH2
Electron Transport System
• Imbedded in the inner
mitochondria membrane are
a series of electron
carriers. These electron
carriers pass electrons from
NADH and FADH to one
another down a red-ox
stairway. The net result of
this series of step-wise
electron exchanges is to
pump H+ (protons) out of
the matrix into the outer
compartment between the
outer and inner membrane
of the mitochondria.
Energy Generated in ETS
NADH –2 from intermediate step + 6 from
TCA cycle = 8 NADH [ each NADH will
yield 3 ATP] The 2 NADH from glycolysis is
said to only yield 4 ATP in the ETS
FADH2 – 2 from TCA cycle [ each FADH2 will
yield 2 ATP]
Total ATP generated in ETS = 24 + 4 = 28 +
4 ATP = 32 ATP [+ 4 ATP = 36 total ATP]
Metabolic Rate
• Total amount of energy produced and
used by the body per unit of time
• Daily input of energy should be equivalent
to the metabolic expenditure
• If too low will cause weight loss
[ negative energy balance]
• If too high will cause weight gain
[positive energy balance]
Metabolic Energy Use
• Basal Metabolic Energy [BMR] – energy
needed to maintain resting body functions
• Thermic Effect of Food [TEF]– energy
needed to digest and ingest nutrients –
accounts for ~10% of daily energy needs
• Muscular Activity – energy needed to
perform all functions above BMR –
accounts for ~30% of daily energy needs
Basal Metabolic Rate
•
Roughly 1 kcal/kgBW/hr for men and 0.9
kcal/kgBW/hr for women
• Example: 130 lb woman
1. Convert lb to kg 130 / 2.2 = 59 kg
2. Multiply 59 kg x 0.9 kcal/hr x 24 hrs =
1274 kcals/day
Example: 170 lb man – 170/2.2 =77.2 kg
77.2 kg x 1.0 kcal/hr x 24 hrs = 1852.8
kcals/day
Basal Metabolic Rate
of selected Organs
• When at rest, the percent of total body
energy that is used by various organs:
LIVER = 27%
BRAIN = 19%
SKELETAL MUSCLE = 18%
KIDNEYS = 10%
HEART = 7%