Lecture #2 Flashcards
Briefly describe the “Equilibrium Law” and “Enzymatic catalysis”
- Chemical Equilibrium Law: when a system is in equilibrium and is subjected to a change, the system re-adjusts itself to counteract the effect and reach a new equilibrium
- Enzymatic Catalysis: enzymes can decrease the activation energy, thus greatly accelerating the reaction rate; they bind to the substrate then catalyze the reaction, giving enzyme and product separately
Why is ATP essential for life?
-can drive energetically unfavorable reactions
Where in ATP is the high energy stored, and how it is released?
- the bond connecting the third phosphorous is the high energy bond
- released by breaking this bond and converting ATP to ADP
What are the three sources of ATP in cells?
- phosphagen mobilization
- fermentation
- oxidative phosphorylation
What are their advantages and disadvantages?
- phosphagen mobilization: very high rate of ATP production but very low capacity to create ATP (makes very little very fast, doesn’t need oxygen), essential to the first few seconds of high exertion
- fermentation: high rate of ATP production but low capacity to create ATP (only makes little but fast, doesn’t require oxygen)
- oxidative phosphorylation: low rate of ATP production but very high capacity to create ATP (makes a lot very slowly, needs oxygen)
What are the enzymes that reversibly transfer the high energy phosphate bond of ATP to a phosphagen?
- phosphokinases
- EX: Creatine Phosphokinase (CPK) in vertebrate tissues
Creatine+ ATP Phosphocreatine+ ADP + Pi
What happens during core glycolysis?
- glucose is oxidized and NAD+ is reduced into NADH
- ATP is produced by substrate level phosphorylation, invests 2 ATP and produces 4 ATP, net gain of 2
- 6 carbon sugar is split into 2 3-carbon molecules
Why and when are the “alternative endpoints” essential?
- if oxygen is present, the NADH created can be used in oxidative phosphorylation
- if it isn’t, the NAD+ needs to be regenerated some other way to continue doing core glycolysis
- converting pyruvate into an alternative endpoint (like lactate) oxidizes the NADH into NAD+ again
After core glycolysis, what happens to pyruvate when there is O2 present?
pyruvate is imported into the mitochondria for further oxidation and energy production
What are some of the advantages of aerobic metabolism, and how did the emergence of Photosynthesis changed life on Earth?
- the step-wise, complete oxidation of substrates in mitochondria allows the efficient storage of released free energy in ATP
- complete degradation of carbon skeletons into CO2 rather than partial, gleaning ~41% of the total energy from glucose as opposed to ~4% (remaining 59% released as heat)
- as amount of oxygen increased, so did biodiversity as more complex organisms were able to survive since they had access to more energy
What are the two processes that take place in mitochondria to enable aerobic metabolism?
- Citric Acid Cycle AKA Krebs Cycle AKA Tricarboxylic Acid Cycle (further oxidation of carbon skeletons)
- Oxidative Phosphorylation (electron transport chain + chemiosmosis, produces ATP)
What is the main function of the citric acid cycle? What are other two names for this cycle?
- Krebs Cycle and Tricarboxylic Acid Cycle
- carbon containing molecules get further oxidized
What is the main function of oxidative phosphorylation?
-transforms the energy from NADH to ATP
- Electrons are donated by NADH at different enzyme Complexes
- As electrons pass along Complex I-V, they release energy that is used to pump H+ across the mitochondrial inner membrane and into the intermembrane space
- At Complex IV electrons are finally donated to O2 and form H2O
- The H+ that had accumulated in the mitochondrial intermembrane space flows back into the mitochondrial matrix through the ATP synthase, and that energy is used to generate ATP (from ADP and Pi)
What is the main function of chemiosmosis? What is the name of the enzyme involved in this process?
- If a reaction doesn’t release enough energy to generate 1 ATP, it can be repeated endlessly until it has pumped enough protons to generate 1 ATP
- each NADH would yield 2.5 ATP, so it saves the H+ until there are enough to produce a full ATP
- energy release is disconnected from ATP synthesis
- enzyme used is ATP synthase
