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Flashcards in MCM Mitochondrial Bioenergetics Deck (52):
1

What is the delta G prime knot of Acetyl CoA?

-7.5 kcal/mol

2

What are other pathways used to get to Acetyl CoA?

amino acid breakdown
lipids: beta oxidation

3

How does pyruvate get into the mitochondria?

Mitochondrial pyruvate shuttle

4

What is the clinical importance of PDC phosphatase deficiency?

PDC will always be phosphorylated (inactive) and will not carry out the reaction of pyruvate to acteyl coa. Instead, Lactate will build up and cause lactic acidosis.

5

What activates PDC?

Ca2+, Mg2+, (NAD+, ADP, coA - via inhibition of PDK) (low energy levels)

6

What inhibits PDC?

Acetyl-CoA, NADH, ATP (Activation of PDK to phosphorylate PDC and inactivate it (no acetyl-CoA is made).

7

What are the products of TCA?

3 NADH, 1 FADH, 1 GTP, 2 CO2

8

What are the energy differences from glucose vs. fatty acids?

Glucose going through TCA can produce about 36-38 ATP, while Beta oxidation of palmitic acid will produce 129 ATP.

9

Describe how Acetyl CoA is used in different pathways during conditions of fasting or diabetes.

A lot of Acetyl CoA is produced during this time due to fatty acid breakdown for energy, however, OAA is being used for gluconeogenesis, so it cannot be used in TCA, and is used to make ketone bodies.

10

CoA (coenzyme A) is synthesized from what?

Vitamin B5, ATP, and cysteine.

11

What is the rate limiting step in the TCA cycle?

IDH

12

Explain PDH deficiency in children.

Defect is in E1 of PDC. Affected infants show high serum pyruvate and lactate. Vitamin B1 is given to normalize lactate levels. Vitamin B1 serves as a cofactor of E1. A ketogenic diet to minimize pyruvate formation and generate acetyl CoA is also used.

13

What does arsenite do to lipolic acid?

It links the 2 SH groups together and essentially turns off PDC and other enzymes that use lipoc acid (alpha keto-glutarate)

14

What is Beriberi and Wenickie-Korsakoff Syndrome?

Caused by a thimaine deficiency (Vitamin B1). Symptoms include: weight loss, SOB, difficulty walking, confusion: peripheral neuropathy. Dry beriberi affects the CV system. Treatment is with thiamine (vit B1) supplements.

Wenickie-Korsakoff is found in chronic alcoholics because it inhibits thiamine absorption. It also impairs the function of PDC since, it contains thiamine.

15

How does citrate play a role in inhibition of glycolysis and activation of fatty acid synthesis?

Citrate is an allosteric inhibitor of PFK-1 in glycolysis and an activator of acetyl-Coa Carboxylase, which converts it to malonyl-CoA for fatty acid synthesis. That way, Citrate both inhbits glycolysis and activates Fatty acid production.

16

How does rat poison inhibit TCA/Glycolysis

Fluoroacetate reacts with Coa to form F-CoA, and then condenses with OAA to form fluorocitrate. Fluorocitrate is a competitive inhibitor of aconitase. Thus, aconitase is inhibited and citrate builds up and inhibits citrate synthase. Fluoroacetate also inhibits PFK-1 in glycolysis.

17

What happens in Pyruvate decarboxylase deficiency?

Pyruvate cannot be turned into OAA, so it turns into lactic acid, causing ketosis. Symptoms include, seizures, muscle weakness, and a taxia. Population affected is Algonkian Idian tribes in eastern Canada (REMEMBER THIS FACT IF YOU REMEMBER ANYTHING FROM THIS WEEK...jk).

18

2-Oxoglutaric aciduria is a TCA disease

Severe neurological problems in infants, Metabolic acidosis Severe microcephaly Mental retardation

19

Fumarase deficiency

Characterized by severe neurological impairment. Fatal outcome within the first 2 yrs. of life


Encephalomyopathy Dystonia
Increased urinary excretion of fumarate, succinate, a- ketoglutarate, and citrate
Autosomal recessive
disorder
Mutation in fumarase gene contains Q319E

20

Succinyl-CoA synthetase (SCS) deficiency

Associated with mutations two out of three subunits making up the enzyme
SUCLA2
SUCLG1
These genes encode the β-subunit of the ADP-forming SCS and α- subunit of SCS

21

What are other electron transport systems used, ex. CYP enzymes (Cytochrome P-450)

Found in the Rough ER: they are active in metabolizing many hydrophobic compounds, drugs, and toxins. They use NADPH.

22

Explain what the ubiquinone radical is and how it generates ROS?

The ubiquinone radical is an intermediate in the transfer of electrons from Complex I to Q. The Q-radical can then pass the electron to molecular oxygen, forming superoxide, which is an ROS. Superoxide dismutase converts it to peroxide, and then peroxide can be converted to water using glutathione reductase. These processes require NADPH (from the PPP).

23

What are the 3 things required for OX Phos to be successful?

1.To transfer electrons from
NADH and FADH2  O2

2.To establish a proton gradient across the inner
mitochondrial membrane

3.To synthesize ATP

24

2 Factors drive the PMF?

membrane potential and pH gradient. As electrons flow through the complexes, protons are pumped from the matrix to the intermembrane space.

25

What are the protein complexes involved in the ETC?

Complex 1: gives electrons to mobile Q carrier and pumps protons into intmbrne space.
Q (embedded in membrane): passes electrons to complex 3
Complex 2: (SDH): no pumping of electrons
Complex 3: pumps protons and passes electrons to Cyt-C (not embedded in membrane, so it can be taken out) which takes them to complex 4.
Complex 4 receives electrons and reduces oxygen to water.

26

What happens when transfer of electrons inhibited?

A decrease in the pumping protons

A decrease in the
protein gradient

Inhibition of ATP synthesis

27

Explain Cyt-C and apoptosis response

Cyt-C is an electron carrier protein in the ETC. During apoptosis caused by stress, ROS, the mitochondrial permeability transition pore complex causes release of Cyt-C, which activates caspases to start executing apoptosis and killing the cell.

28

Explain what mDNA is?

mDNA is mitochondrial DNA that encodes tRNAs, and 13 proteins that function in the ETC. It replicates independtly of chromosomal DNA.

29

What is Rotenone?

A pesticide and fish poison. It is a potent inhibitor of Complex 1 in the ETC. Treatment is Vitamin K3 to bypass blockade.

30

How does Cyanide poisoning work?

Cyanide inhibits complex 4 in the ETC and prevents O2 reduction. ATP production ceases.

31

What is the difference between CN and CO poisoning?

CO is a competitive inhibitor of Complex 4 (increase in Km), and CN nad H2S are noncompetitive inhibitors (decrease Vmax).

32

What happens in aspirin poisoning?

High doses cause hyperthermia because it uncouples oxidative PO4 to ATP synthesis by disrupting the proton gradient: causes dissipation of heat. Also causes hyperventilation: need gastric lavage and hemodyalisis to treat.

33

What are the inhibitors of complex 1 in the ETC?

amytal, Rotenone, Myxothiazol, Piericidin A

34

What are the inhibitors of complex 2 in the ETC?

Malonate

35

What are the inhibitors of complex 3 in the ETC?

Antimycin

36

What are the inhibitors of complex 4 in the ETC?

CO, CN, H2S

37

What inhibits ATP Synthase (complex 5)?

Oligomycin

38

What is the coupling of transfer of electrons to ATP synthesis using the PMF?

Chemiosmosis

39

What are the uncouplers of Ox Phos?

AraC, AZT (used for cancer treatment), Aspirin, DNP, Thermogenin

40

Explain the impacts that respiratory control (high ATP/Low ATP) has on the ETC, PMF, TCA, glycolysis?

If ATP/ADP ratio is high, ATP synthase will be inhibited, as a result, the H+ gradient increases, but ETC slows down pumping, which slows down everything else.

If ADP/ATP ratio is high, ATP synthase is activated, which decreases the proton gradient, causing the ETC to speed up and all the other upstream things to speed up as well.

41

What are the outcomes of uncouplers?

TCA cycle and electron transfer to O2 are accelerated (hyperventilation may result?)
ATP synthase is inhibited (No ATP Synthesis)
Heat generation

42

How much ATP is synthesized per day?

72.7 mols

43

What happens in hypoxic conditions? Someone has a heart attack/stroke?

a decrease in oxygen causes a decrease in the activity of ETC/PMF. O2 starvation causes glycolysis to be used more for energy, which produces lactate -> lactic acidosis,. Lowered pH in the mito matrix causes IF1 to inhibit ATP synthase, so ATP levels are preserved.

44

What is brown fat and how is it used for thermogenesis?

Brown adipose tissuse contains a lot of mitochondria and expresses UCP-1: an uncoupling protein that disrupts the proton gradient and causes heat to be dissipated.

45

Where does the malate-aspartate shuttle work (which organs) and what does it do?

Heart, liver, kidneys, and it takes NADH from the cytosol, converts it into malate, which can enter the mito, and then malate gets reduced, and forms NADH in the mito. The NADH then gets carried to complex 1. Carries out redox reactions.

46

Where does the glycerophosphate shuttle work (which organs) and what does it do?

Skeletal muscle and brain.

Carries out redox reactions

Generates FADH2 in the inner mito- membrane
FADH2 joins to ETC at CoQ (skips Complex 1 so less protons are pumped).


47

What is the Phosphate/OH exchange?

Antiporter that uses the PMF as energy. It transports phosphate into the matrix and OH- out

48

What is the phosphate/malate exchange?

Antiporter that uses the PMF as energy. It transports phosphate into the matrix and malate out

49

What is the ADP/ATP Exchange?

Antiporter that transports ATP out and ADP in to the matrix.

50

What is the Pyruvate/OH Exchange?

Transports pyruvate in and OH- out.

51

What was the first mitochondrial disease discovered and what is it?

Luft's Disease: Profuse perspiration
Marked fluid intake, but normal urine volume
Daily caloric intake was extremely high (~3,000 kcal)
Stable body weight of 38 kg and body height of 159 cm
She was asthenic (lack or loss of strength) with progressive weakness
Lab findings:
Abnormally increased BMR (+180%)
Thyroid functions were in normal range

Uncoupling of oxidative phosphorylation was found
High levels of Cytochrome-c oxidase
Relatively low levels of coenzyme Q10
High content of RNA in muscle homogenate (evidence of mito-protein synthesis)
Electron microscopy
Large accumulations of mitochondria with highly variable size
Paracrystalline inclusions

52

What are the primary causes of mitochondrial diseases?

Defect in nuclear DNA (nDNA) encoding the mitochondrial proteins
Defect in mitochondrial DNA (mDNA)

Secondary causes are basically environmental factors.