BIOL 2420 Lecture Notes - Lecture 3: Glycogen, Histology, Catabolism

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Unit 10 Lecture 3
Energy Is Stored in Fat and Glycogen
- Daily energy requirement (caloric intake) varies with the needs and activity of the body
- Examples:
o during 2008 Olympics, swimming champion Michael Phelps consumed more than
12,000 kcal per day
o woman engaged in normal activities may requires only 2000 kcal per day
if this requirement is met by only ingesting glucose
glucose has an energy content of 4 kcal/g
to meet the requirements the woman would have to consume 500g or
1.1 lbs of glucose each day
our bodies cannot absorb crystalline glucose, the 500 g of glucose would need
to be dissolved in water
glucose is not our primary fuel
glucose polymer glycogen is a more compact form of energy than an
equal number of individual glucose molecules
o requires less water for hydration
our cells convert glucose to glycogen for storage
we normally keep ~100 g of glycogen in the liver and 200 g in skeletal
muscles
300 g of glycogen can provide only enough energy for 10-15 hours
o the brain alone requires 150g of glucose per day
the body keeps most of its energy reserves in compact high-energy fat
molecules
1g of fat has 9 kcal (more than twice the energy content of an equal
amount of carbohydrate or protein)
each pound of body fat stores 3500 kcal of energy
high caloric content of fat and the histology of fat cells (minimal cytosol
and large central fat droplet) make adipose tissue very efficient at
storing large amounts of energy in minimal space
o metabolically -> energy in fat is harder to access
metabolism of fats is slower than that of carbohydrates
Metabolism
- metabolism sum of all chemical reactions in the body
o reactions making up these pathways
1. extract energy from nutrients
2. use energy for work
3. store excess energy for later use
o anabolic pathways - metabolic pathways that synthesize large molecules from smaller
ones
o catabolic pathways metabolic pathways that break large molecules into smaller ones
- classification of a pathway is a net result not what happens at any individual step of the
pathway
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