energy transfer Flashcards
Energy is extracted from food
incrementally
4
* Photosynthesis: ……………………..
* Metabolism: ………
Energy is extracted from food
incrementally
4
* Photosynthesis: Chemical reactions in plants
convert light from the sun to stored chemical
energy
* Humans obtain energy by eating plants and
animals
* Energy substrates including carbohydrate,
protein, and fat are broken down in our body to
release energy
* Chemical pathways in animals and humans
convert substrates to energy through stepwise
metabolic reactions
* Metabolism: The chemical reactions in the body
collectively
* All energy eventually degrades to heat
What are the two forms of energy?
Total energy (of a system) = Kinetic + Potential
* Potential energy
* “Trapped” energy
* Energy of position or structure
* Kinetic energy
* Energy of motion
Human examples
of use of energy
Human examples
6
* The chemical bonds in macronutrients (carbs, lipids, proteins) in
our food are a form of potential energy
* But they are not usable in our body
* Bonds that hold these elements together are relatively weak
* Our body needs to convert these to high-energy compounds to be usable
Human bodyIntake output
Growth and
repair,
Cellular and nerve
functionspotential
energy Kinetic energy
(motion)
denosine triphosphate (ATP)
phosphorylation: .,…..
- Oxidative phosphorylation: ……
denosine triphosphate (ATP)
9
Breaking of the high energy bonds release
7.3 kcal free energy liberated + P i ATP hydrolysis
ATP –> ADP + P i
* Substrate-level phosphorylation: ATP generated
independently of oxygen
* Oxidative phosphorylation: ATP producing reactions with the
use of oxygen
* Unfortunately, the store of ATP is enough for only about 2-3
seconds of maximal effort
First law of
thermodynamics..
Potential energy is transferred to electricity
Potential energy is transferred to ATP
Second law of thermodynamics
Spontaneous transfer of potential energy decreases the
capacity to perform work
* Potential energy degrades to kinetic energy
* Entropy always increases (non-usable energy)
* As macronutrients are oxidized, the products of each
reaction have less potential energy than the reactants
Humans are inefficient
How much of the energy that we get is converted to
mechanical work?
* Phosphorylative coupling efficiency ~60%
* Proportion of energy released in catabolism of (potential) energy
substrates that is captured as ATP
* Mechanical coupling efficiency ~50%
* Proportion of total chemical energy stored in ATP that is converted to
mechanical work in the hydrolysis of ATP
* Overall efficiency ~30%
* ~70% is lost as heat!
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