BIOL 2420 Lecture Notes - Lecture 2: Waste Heat, Skeletal Muscle, Food Energy

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Unit 10 Lecture 2
Energy Balance
- Oe food is digested ad asored, the od’s etaolis deteries what happes to the
nutrients in the food
o Used to burn off heat, become muscle, turn into extra pounds
Energy Input Equals Energy Output
- First law of thermodynamics
o The total amount of energy in the universe is constant
o All energy that goes into a biological system can be accounted for
- In the body most stored energy is contained in chemical bonds of molecules
- Can apply the concept of mass balance to energy balance
o Chages to the od’s eerg stores result fro the differee etwee eerg put ito
the body and energy used
o Total body energy = energy stored + energy intake energy output
o Energy intake in humans
Energy in the nutrients we eat, digest, and absorb
o Energy output
Combination of work performed and energy returned to the environment as
heat
o Energy output = work + heat
In the human body, at least half the energy released in chemical reactions is lost
to the environment as unregulated waste heat
work takes o oe of three fors
1. transport work
moves molecules from one side of a membrane to the other
transport processes bring materials into and out of the body and
transfer them between compartments
2. mechanical work
uses intracellular fibers and filaments to create movement
includes
o external work
movement created by skeletal muscle contraction
o internal work
movement of cytoplasmic vesicles and the pumping of
the heart
3. chemical work
used for growth, maintenance, storage of information and energy
subdivided into synthesis and storage in the human body
o storage
short-term energy storage in high-energy phosphate
compounds (ATP)
long-term energy storage in chemical bonds of glycogen
and fat
most energy consuming work in the body is not under conscious control
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Document Summary

O(cid:374)(cid:272)e food is digested a(cid:374)d a(cid:271)sor(cid:271)ed, the (cid:271)od(cid:455)"s (cid:373)eta(cid:271)olis(cid:373) deter(cid:373)i(cid:374)es what happe(cid:374)s to the nutrients in the food: used to burn off heat, become muscle, turn into extra pounds. First law of thermodynamics: the total amount of energy in the universe is constant, all energy that goes into a biological system can be accounted for. In the body most stored energy is contained in chemical bonds of molecules. Behaviour modifications (eating less and exercising more) are among the most frequent instructions healthcare professionals give to patients: are also the most difficult for people to follow patient compliance is low. (cid:373)ost (cid:272)o(cid:373)(cid:373)o(cid:374) (cid:373)ethod for esti(cid:373)ati(cid:374)g (cid:373)eta(cid:271)oli(cid:272) rate is to (cid:373)easure a perso(cid:374)"s o(cid:454)(cid:455)ge(cid:374) consumption: oxygen consumption the rate at which the body consumes oxygen at it metabolizes nutrients. Rq varies from a high of 1 for a pure carbohydrate diet to 0. 8 for pure protein and 0. 7 for pure fat: average american diet has an rq of about 0. 82.

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