LEC03 Flashcards
What is the definition for energy?
The capacity to do work.
What is Gibbs Free Energy (G)?
Amount of energy in a system that can be used to do work while at a constant temperature and pressure.
What is the formula for the change in Gibbs Free Energy?
∆G = G final state - G initial state
What is the significance of a negative or positive G value?
If the ∆G is negative, the biological system cannot proceed. Whereas it can proceed if the ∆G is positive.
Exergonic Reactions
- Catabolic reactions (Releases energy)
- ∆G is less than 0
- Spontaneous (not fully as some can be controlled)
Endergonic Reactions
- Anabolic reactions (requires energy)
- Not spontaneous
- ∆G is greater than 0
What does coupling do?
Coupling involves using an exergonic reaction which releases energy to power an endergonic reaction.
What is activation energy?
The minimum amount of energy needed for a reaction to occur (the threshold it needs to breach).
Do spontaneous reactions still require activation energy?
Yes!
What do enzymes do to the activation threshold?
As biological catalysts, they lower it, therefore reducing the amount of activation energy required.
What does ATP hydrolysis do?
Releases energy to drive endergonic reactions; and therefore is a source of energy for many cellular endergonic reactions. Must be regenerated constantly.
What is a way to generate ATP?
Cellular respiration.
What is NADH and why is it important and what is it used for?
- Electron carrier
- It carries electrons down the electron transport chain which plays a role in generating energy.
Name the four steps of cellular respiration.
- Glycolysis
- Pyruvate oxidation
- Kreb cycle
- Oxidative phosphorylation
Explain glycolysis.
- Produces two NADH and two ATP (net)
- Occurs in the cytosol
- One 6-carbon glucose is broken down into two 3-carbon pyruvates
- 10 enzymatic steps
Explain pyruvate oxidation.
- Produces Acetyl CoA, carbon dioxide, and one NADH per pyruvate (So as one glucose produces two pyruvate, one glucose will also produce two NADH)
- Occurs in the mitochondrion
- Pyruvate transported into the mitochondrion via a transport protein
- One pyruvate produces one Acetyl CoA, so one glucose produces two Acetyl CoA.
Explain the citric/kreb cycle.
- Produces carbon dioxide, FADH, NADH, and ATP (One Acetyl CoA produces two carbon dioxides, one FADH, three NADH, and one ATP; double everything when counting from one glucose molecule.
- Occurs in the mitochondrion
- 8 enzymatic steps
Explain oxidative phospholyration.
- Produces ATP by using FADH and NADH (approx. 26-28 ATP per glucose molecule)
- Two phases: electron transport chain, and chemiosmosis (go in depth later).
- Occurs in mitochondrion
Explain the electron transport chain from the oxidative phosphorylation step.
- Pumps protons along the membrane
- Four membrane proteins pass the electrons along
- Input: NADH, FADH, and oxygen
- Output: Proton gradient and water
Explain chemiosmosis from the oxidative phosphorylation step.
- The membrane is impermeable to protons (hydrogen ions) so they must flow back through ATP synthase
- ATP synthase is like a mill and rotates from the potential energy of protons
- Proton flow back, then ATP synthase uses potential energy to make one ATP for every four protons.
What is the reverse of respiration?
Photosynthesis
Explain photosynthesis in terms of electron transport and chemiosmosis.
- Opposite to respiration, water is the electron donor and it generates oxygen and NADP+
- ATP synthase is used to make ATP
- ATP and NADPH are used in the Calvin cycle to convert carbon dioxide into sugar.
