KNES 464 Lecture Notes - Lecture 8: Gibbs Free Energy, Calcium Atpase, Serca
5 Nov 2018
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Lecture 8
Proteins as Enzymes and Gibbs Free Energy
Spontaneous—release energy to surroundings from systems—exergonic
- Reactants have more energy than products (products have lower energy than reactants)
- Negative Gibbs free energy (- delta G)
Nonspontaneous—system absorbs energy from surroundings-- endergonic
- Energy input
- Products have higher energy than reactants
- Positives Gibbs free energy (+ delta G)
ATP hydrolysis-- ATP→ ADP + P + energy (exergonic)
3 main energy utilizers that uses energy→
- Actin Myosin ATPase (where the crosbridges are cycling)
o 75% of sketlal muscle energy
o actin and myosin proteins is the biggest contribution as well (sarcomeres)
- SERCA pump (SR calcium ATPase)—pumping this calcium back into the cell
o After contraction is over—we have to pump calcium back into SR—need energy
because it is against the concentration gradient
o Have to put it back in so we have the chemical gradient back
o Need to put in ATP energy to do that
o When we pull open the ryanodine receptor and calcium comes out, it is faster
than pumping it back in
o 10%-20%
o second largest thing that takes up space in the muscle--
▪ for type 2 muscle fibers-- compromise the mitochondria to have more
SERCA
- Sodium Potassium ATPase→ maintain cellular membrane potential
o Pump Na in one direction and potassium in another direction
o Ion pumps
o 2%-10%
What will affect the distribution of the ATPases?
- Muscle fiber types
o Myosin ATPase--
o Calcium cycling—have more in Type 2
▪ Type 2 fibers have more in SR
• Because they have more force and will need that extra calcium
and will try to fire them fast—have to be dumping and taking
calcium as weioakly as you can
• Will have more in Type 2
Document Summary
Reactants have more energy than products (products have lower energy than reactants) Negative gibbs free energy (- delta g) Positives gibbs free energy (+ delta g) Atp hydrolysis-- atp adp + p + energy (exergonic) Actin myosin atpase (where the crosbridges are cycling: 75% of sketlal muscle energy, actin and myosin proteins is the biggest contribution as well (sarcomeres) Sodium potassium atpase maintain cellular membrane potential: pump na in one direction and potassium in another direction. Enzyme puts reactants in an orientation that makes the reaction more likely to happen. Chemical reactions require activation energy to initiate the raction. Ensymes lower the activation energy, making it more leikly for the reaction to start. Without the enzyme, the reaction would depend on random collisioms between the reactants to bring them into proper alignment. Site of regulation if you can regular enzyme activity, can regulate the site of what is happening.
