Fuel Oxidation and ATP generation

Question 1

What’s the point of ATP

Answer 1

ATP contains “high energy” phosphate bonds we use that energy to: -muscle contraction -active ion transport -biosynthesis -detoxificaion -thermogenesis

Question 2

(ΔG) for a reaction

Answer 2

free energy change depends on temperature and on the concentration of the products and the substrates when the rxn is at equilibrium

Question 3

What does ΔG>0 mean?

Answer 3

at equilibrium the reactants are favored, so it needs external help to proceed

Question 4

ATP hydrolysis coupled to change in transporter conformation. Costs energy to move ions against electrochemical gradient.

Answer 4

Transport work: Na+/K+ -ATPase

Question 5

*ATP hydrolysis coupled to change in protein conformation.

Answer 5

Mechanical work: muscle contraction

Question 6

ATP hydrolysis coupled to change in enzyme conformation.

Answer 6

Synthesis (work): asparagine synthetase -ATP activating the enzyme

Question 7

only type that ATP physically participates in the reaction itself (adds a phosphate to the reactant.

Answer 7

Biochemical work: glucose to G6P (its phosphorylation, so the enzymes will be kinases)

Question 8

Molecules with phosphate or thioester linkage have high energy bonds, so?

Answer 8

We can cleave these to release a lot of energy (couple it to rxn we want to drive forward!)

Question 9

What fuels can we get the most energy from?

Answer 9

**FA least oxidizes relative to number of carbons. glucose is the worst- most oxidized

Question 10

Name 2 electron carriers that capture energy from oxidized fuels, and what is used to synthesize each?

Answer 10

NAD+ - made via niacin FAD+ - made via riboflavin *buzz word: dehydrogenase reactions

Question 11

name 2 metabolic byproducts of fuel oxidation and ATP generation

Answer 11

-H20 (formed when oxygen molecules - the final electron acceptors of cellular resp. - take up protons) -CO2 (TCA cycle)

Question 12

What is another term for glycolysis?

Answer 12

anaerobic metabolism -doesnt require oxygen or mitochondria -reducing pyruvate to lactic acid regenerates the electron carriers -takes place in cytosol -RBCs, WBCs, Kidney medulla, eye tissue -skeletal muscle (white fibers!)

Question 13

What is another term for oxidative phosphorylation?

Answer 13

aerobic metabolism -takes place in mitochondria -requires mitochondria and oxygen -skeletal muscle (red fibers), most tissues of the body

Question 14

Products of glycolysis

Answer 14

-2ATP -Lactic ACID -NAD+ -FAD+

Question 15

Products of oxidative phosphorylation

Answer 15

-28 ATP -o2 (final electron acceptor)

Question 16

Glycolysis investment phase

Answer 16

a

Question 17

What are the 2 regulated steps in the investment phase of glycolysis, and why are they regulated?

Answer 17

conversion of glucose to G6P (currency of cell!) -*hexokinase is the enzyme that accomplishes phosphorylation conversion of fructose 6 phosphate to fructose 1,6 bisphosphate -*phosphofructokinase enzyme -they are regulated because they require ATP (phosphorylation), dont want to run the step and waste energy if they are not needed.

Question 18

result of investment phase

Answer 18

Converted 1 glucose into 2 trioses Used 2 ATP ΔG′° = -51 kJ/mol – why is this negative? -Giving off energy because of ATP hydrolysis

Question 19

What are the 2 regulated steps in the payoff phase of glycolysis, and why are they regulated?

Answer 19

conversion of 1,3-Bisphospho-glycerate to 3-Phospho-glycerate is regulated (bc it requires ATP!) -enzyme: phosphoglycerokinase conversion of Phosphoenol-pyruvate (PEP) to Pyruvate is regulated (bc it requires ATP!) -enzym: *pyruvate kinase

Question 20

result of payoff phase

Answer 20

2 trioses into 2 pyruvate molecules Make 4 ATP, net of 2 ATP 2 NAD+ are reduced (NAD+ + H:- NADH) Oxidation of glucose!

Question 21

when you see a dehydrogenase enzyme, what does that tell you?

Answer 21

electron carrier are being reduced!

Question 22

So what is the point of glycolysis?

Answer 22

-for cells that cant do aerobic metabolism, the purpose is to generate the 4 ATP (Only net of 2 ATP tho) (and of course regenerate your electron carriers) *BUT for cells capable of aerobic metabolism, Glycolysis produces: PYRUVATE and NADH

Question 23

What does the Malate shuttle do?

Answer 23

delivers electrons to the mitochondria

Question 24

Regarding the enzymes involved in the steps of glycolysis that require energy, how do we regulate those enzymes?

Answer 24

Substrate availability [enzymes] *Allosteric regulation Covalent modification of enzyme

Question 25

examples of molecules that stimulate glycolysis?

Answer 25

-things in high concentration when energy is depleted will stimulate glycolysis ↑ [AMP]\* ↑ [fructose-2,6-bisP] ↑ [fructose-1,6-bisP]

Question 26

examples of molecules that inhibit glycolysis?

Answer 26

-a build up of the products of glycolysis would inhibit glycolysis ↑ [ATP]\* ↑ [citrate] ↑ [glucose-6-P]\*\* ↑ [NADH] ↑ [acetyl-coA] ↑ [alanine]

Question 27

Cells are responsive to small changes in [ATP]

Answer 27

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Question 28

Is glycolysis active or inactive in cancer cells

Answer 28

Very active. high rate of glycolysis. because these cells are rapidly dividing and initially cancer cells don’t have suffienct vasculature for their rate of cell growth (eventually they do stimulate growth of new vasculature) -you can detect this on a (PET) scan. After patient ingests florolabeled glucose, the tissues with cancer have a higher rate of glycolysis even when oxygen is plentiful (so glucose shows up as pink)

Question 29

Name the common defects in glycolytic enzymes

Answer 29

FALSE, BITCH. defects are not common because you'd be a dead mon

Question 30

how about diabetics, glycolysis high or not?

Answer 30

high! tissue think they are starving so they run glycolysis

Question 31

partial Pyruvate Kinase deficiency

Answer 31

affects RBC survival (type of anemia) | (complete deficency is lethal)

Question 32

Glucose is at the center of / can feed into how many pathways

Answer 32

glycogen path pentose phosphate path TCA cycle fructose/lactose lactate glycosaminoglycans

Question 33

examples of glycolysis intermediates used in other pathways

Answer 33

Used in protein synthesis, TG synthesis, AA synthesis

Question 34

What is the role of lactate dehydrogenase in the absence of oxygen

Answer 34

reduces pyruvate to lactate to regenerate the electron carriers so that glycolysis can continue

Question 35

What is the role of lactate dehydrogenase in the presence of oxygen

Answer 35

Lactate may also be converted back to pyruvate (by lactate dehydrogenase) when O2 levels return to normal in the cells.

Question 36

Explain the Cori cycle

Answer 36

![]() we can send the lactae from RBCs to the liver and use it to make glucose!

Question 37

Predict the effect of elevated levels of each of the following on ATP production by glycolysis: AMP acetyl-coA glucose-6-phosphate NADH fructose-1,6-bisphosphate

Answer 37

AMP: stimulate acetyl-coA: inhibit glucose-6-phosphate: inhibit NADH: inhibit fructose-1,6-bisphosphate: stimulates

Question 38

Toward the end of running the 1600m during a track meet, a 22 year-old athlete cramps up. In biochemical terms, what is causing the cramping and what will alleviate it?

Answer 38

Lactic acid build up (because of temporary hypoxia in skeletal muscles) must use only glycolysis Treatment: slow down and breath (more O2)

Question 39

SO, after glycolysis, how do we get to aerobic metabolism, what is the linker step?

Answer 39

-pyruvate molecules are converted to Acetyl CoA by: \*Pyruvate dehydrogenase complex (PDC) -Now Acetyl-coA can enter the TCA cycle in the mitochondrial matrix

Question 40

PDC converst pyruvate but also produces what?

Answer 40

2 NADH

Question 41

PDC stimulated by

Answer 41

Pyruvate NAD+

Question 42

Inhibits PDC

Answer 42

Acetyl CoA NADH

Question 43

Pyruvate is only one source of Acetyl CoA, what other fuels can be oxidized to generate Acetyl CoA?

Answer 43

FAs Ketone bodies Amino Acids Acetate

Question 44

Result of TCA cycle

Answer 44

Per glucose: 6 NADH\* 2 FADH2\* 2 GTP \*basically we are just oxidizing acetyl CoA to reduce electron carriers

Question 45

Regulation of the TCA cycle

Answer 45

obviously a build up of the products (the reduced electron carriers! - NADH FADH2) will inhibit the TCA cycle (ADP would stimulate TCA)

Question 46

What happens to the Carbon from Acetyl CoA during TCA cycle?

Answer 46

lost as CO2

Question 47

TCA cycle intermediates can be used in other pathways for?

Answer 47

AA synthesis (oxaloacetate, alph-ketoglutarate) FA synthesis (citrate) Gluconeogenesis (malate) Heme synthesis (succinyl CoA)

Question 48

Anaplerotic reactions

Answer 48

replenish TCA cycle intermediates (so the reverse of using intermediate to make other stuff when we have a bunch, is to synthesis intermediates)

Question 49

A 3 year-old male is brought to the pediatrician by his mother, who is concerned about what appears to be a regression in her son’s physical abilities involving movement and coordination. She reports that he seems to be weaker than he was 6 months ago, and that he occasionally has “jerky” movements of his limbs. Blood tests reveal moderate lactic acidemia. What deficiency could explain these findings?

Answer 49

1. For some reason he's not getting enough oxygen and therefore using glycolysis and producing lactic acid 2. Could be some type of TCA deficiency (not getting enough of one of the enzymes) 3. PDC deficiency (so we aren’t converting pyruvate into acetyl CoA (pyruvate accumulates and we see an increase in lactate) \*3 is most likely - Increase in lactate is causing the symptoms (hes not getting enough Oxygen his muscles need to grow and function properly This is a lethal condition

Question 50

Compare ATP production in Glycolysis, PDC linker step, and TCA cycle

Answer 50

\*they contribute a lot of electron carriers, not much ATP ## Footnote Pathway ATP (net) NADH (FADH2) Glycolysis 2 2 PDC (linker step) 0 2 TCA cycle 2 6 (2) TOTAL: 4 10 (2)

Question 51

ATP production in Substrate-level phosphorylation vs. Oxidative phosphorylation

Answer 51

4 vs. 26 - 28

Question 52

oxidative phosphorylation = ? (2 components)

Answer 52

ETC + ATP synthase

Question 53

What is absolutely necessary for oxidative phosphorylation?

Answer 53

a pH gradient -ETC receives electrons from NADH/FADH2 and pumps protons from the matrix into intermembrane space We develop a proton gradient (the protons want to move back into the mitochondrial matix, but to cross into the matrix requires some transport (they do so by moving through the ATP synthase – despite being tiny they need this) remember (TCA cycle is in matrix)

Question 54

Components of the ELECTRON TRANSPORT CHAIN (ETC)

Answer 54

Complex I, III, IV ATP synthase O2

Question 55

What role do Iron (Fe) and copper (Cu) have in the ETC?

Answer 55

They are needed for the complexes to function properly

Question 56

What carries electrons between between complexes I and III

Answer 56

Ubiquinone (CoQ) it's a hydrophobic electron shuttle

Question 57

Two components to the Mitchell Hypothesis?

Answer 57

ATP synthase + H+ gradient = oxidative phosphorylation -experiment Vessicles in dark no ATP production (no gradient H+) Hit with light and got the ATP production

Question 58

Movement of H+ leads to conformational changes in ATP synthase

Answer 58

Rotation on the C1-C5 part will cause conformational change in (F1) head piece ![]() note: rotation of F0 has been proven experimentally

Question 59

what happens if the inner mitochondrial membrane becomes permeable to H+ as a result of using durgs or disease or whatever?

Answer 59

ET becomes uncoupled from ATP synthase it's called uncoupling the H+ gradient is destroyed! (BUT! that energy is not lost completely - can be dissipated as heat) actually the protein Thermogenin does this in the mitochondira of brown adipose tissue (animals that hibernate)

Question 60

Other than thermogenin, what is another way to chemical uncouple the membrane (in other words ruin the H+ gradient)?

Answer 60

drugs/agents that disturpt the function of the ETC (interfer with the ability of the complexes to transfer electrons) rotenome amytal Carbon monoxide CN (cyanide)

Question 61

–How does her iron deficiency contribute to her fatigue and weakness?

Answer 61

complexes of the ETC need Iron (and copper) to work also her blood O2 is low and we need O2 as the final electron acceptor \*both of these contribute to impairing oxidative phosphorylation

Question 62

A 55 year-old male presents to the emergency department with crushing chest pain, shortness of breath, and fatigue. An abnormal EKG and elevated cardiac enzymes confirm the suspected diagnosis. In this patient’s heart tissue, what would you predict to find in terms of: O2 level [ATP] [H+] [Na+]

Answer 62

O2 level -decreased because of blocked blood flow [ATP] -decresed because glycolysis is our only source of ATP [H+] -increased, due to the increase in lactate (from glycolysis) [Na+] -increased, Na+/K+ pump (requires ATP) so it isn’t pumping/functioning well

Question 63

A 63 year-old patient is brought to the ER with lightheadedness, dizziness, and a headache. He has shortness of breath and seems confused. The neighbor that brought him in said that the patient is a heavy smoker, and that when he found him he was smoking in a poorly ventilated room. In terms of aerobic metabolism, how is the suspected overexposure to cyanide causing the observed signs and symptoms?

Answer 63

CN (cyanide from cigarette smoke) affecting complex 4 -the result is: \*decreased H+ gradient, which causes decreased ATP synthesis\* (know this)