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Biochemistry > Day 4 Electron Transport and Fatty Acid Metabolism > Flashcards

Day 4 Electron Transport and Fatty Acid Metabolism Flashcards

1
Q

Mitochondrial Matrix

A

Innermost space, site of TCA cycle

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2
Q

Mitochondrial inner membrane

A

Site of the electron transport chain and ATP synthase

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3
Q

Mitochondrial intermembrane space

A

Acidic space where the protons are pumped

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4
Q

Mitochondrial outer membrane

A

Permeable to most small membranes lined with porins and voltage dependent anion channels.

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5
Q

The process of oxidative phosphorylation

A

The electron transport chain pumps protons out of the matrix and into the intermembrane where ATP synthase releases protons from the intermembrane back into the matrix and phosphorylate ADP

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6
Q

Electron transport system

A
  • The TCA cycle generates NADH and FADH2 by oxidizing AcetylCoA
  • NADH and FADH2 are then oxidized and the electrons from are used to reduce O2 to H2O
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7
Q

Measurement of reduction potential

A

the electron transfer potential of NADH and FADH2(E0) is converted into the phosphoryl transfer potential of ATP (G0)

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8
Q

Redox couple

A

substance that can exist in both oxidized and reduced form

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9
Q

Electromotive force

A
  • measured by comparing the reduction potential of sample cell to the standard half cell.
  • a strong reducing agent (NADH) has a negative reduction potential and a strong oxidizing agent (O2)has a positive reduction potential.
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10
Q

Reduction Potential of the ETS

A

-Electron carriers are arranged into four protein complexes three of which are proton pumps. -Electron affinity increases as you move down the chain

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11
Q

Complex I

A
  • NADH CoQ reductase
  • Electrons are transferred from NADH to coQ via a seriess of intermediates
  • Proton transport is mediated by alternating between organic and inorganic electron carriers.
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12
Q

Coenzyme Q

A
  • Carrier of 2 electrons
  • Can exist in 3 states:
    1. fully oxidized quinone
    2. partially reduced semiquinone
    3. fully reduced quinol
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13
Q

Complex II and the Q pool

A
  • Transfer electrons from from succinate to CoQ
  • This is not a proton pump
  • FADH2 go through this pump which is why less ATP is formed from FADH2 than NADH
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14
Q

Complex III

A
  • This is the Q cycle, 1 of the 2 electrons from QH2 are transfered to cytochrome C
  • This reaction occurs again and so the pump spits out 2 protons for every 2 electrons given by QH2
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15
Q

Complex IV

A
  • Reduction of molecular O2 happen here and is coupled to the oxidation of Cyt C.
  • Oxygen radicals are generated here
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16
Q

Chemiosmotic hypothesis

A

Proposed by peter Mitchell. He said that the proton gradient formed between the matrix and the inner membrane drives ATP synthesis by ATP synthase.

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17
Q

ATP Synthase F1 unit

A
  • F1 stick has 5 subunits
  • alpha and beta are homologous and they bind ATP and form the active site.
  • gamma and epsilon forms a central stalk. gamma interacts with each beta subunits
  • delta is outside of the stick and interacts with the F0 unit
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18
Q

ATP synthase F0 unit

A
  • F0 has 3 subunits and it is hydrophobic and embedded into the membrane.
  • C forms the inner membrane ring
  • A binds outside of the ring and allow for protons to go through its halph channels
  • B2 connects A to delta
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19
Q

ATP synthesis

A

Rotation of the y stalk lead to conformational change in the beta subunits and that counter clockwise rotation of gamma drives the phosphorylation of ADP at the B subunits

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20
Q

Why does the gamma stalk rotate?

A

Well the flow of protrons through the 2 A subunit half chanels allow theprotons to enter the cytoplasm. The amount of protons required for the C ring to rotate depends on how many subunit that C-ring have. So the protonated C unit will rotate clockwise and that will make the gamma stalk rotate counterclockwise and that will induce a change in conformation by the beta subunit which will release 3 ATP.

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21
Q

Mitochondrial Cristae

A

The folds in the mitochondrial inner membrane allows for the arrangement of the ETC and ATP synthase on opposing faces of the membrane. This allow for efficient transfer of electron due to spacial localization of the two complexes.

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22
Q

Transport of cytoplasmic NADH into the mitochodria 1

A

this can happen via the glycerol-3-phosphate shuttle.
-this path transfer the electron reducing potential from NADH to FADH2 because it bypasses complex 1 and reduces the ATP synthesis capacoty

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23
Q

Transport of cytoplasmic NADH into the mitochodria II

A

Malate Aspartate shuttle

  • Found in the liver and heart
  • Feeds NADH into complex I and does not reduce ATP synthesis so it gives more energy than the glycerol-3-hosphate shuttle.
  • Only occurs when there are more NADH in the cytosol than in mitochondria.
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24
Q

ATP/ADP exchanger

A

-Antiporter coordinates the exchange of cytoplasmic ADP for mitochondrial ATP.

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25
Q

Regulation of oxidative phosphorylation

A

[ADP] determines the rate cellular respiration, the ETC does not occur unless ADP is available for phosphorylation.

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26
Q

Respiratory control

A

electrons does not flow from fuel molecules to O2 unles ATP synthesis is required.

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27
Q

Poison of Complex I

A

blocked by insecticide and barbiturates.

  • accumulate NADH
  • no ATP synthesis
  • lactic acidosis
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28
Q

Poison of Complex III

A

blocked by antifungal, and fish poison

  • accumulate NADH
  • no ATP synthesis
  • lactic acidosis
29
Q

Poison

A

blocked by carbon monoxide, cyanide and Azide.

  • accumulation NADH
  • no ATP synthesis
  • lactic acidosis
30
Q

Uncoupling agent DNP

A
  • Transport protons to matrix without going through ATP synthase so no ATP synthesized so the ETC keeps on running to make energy but no energy is made
  • Used as a weight loss agent
31
Q

Regulated uncoupling

A

Brown Fat uncouples ETC from ATP synthesis.

-use the ETC to generate heat.

32
Q

Fatty Acid Metabolism

A
  • Degradation releases acetyl group in the mitochondria
  • Synthesis requires malonyl group in the cytoplasm
  • Both pathways mirror each other
33
Q

Fatty acids

A

Hyodrocarbons with a terminal carboxyl group

  • usaturated has a double bond
  • saturated does not have a double bond
34
Q

Dietary Fats

A
  • triglycerides are the main dietary lipids
  • essential fatty acids are omega-3 and omega-6
  • most naturally occurring fatty acids have cis unsaturations
35
Q

Trans fats

A

produced by partial hydrogenenation of poly unsaturated fatty acid and they act as inhibitors of HDL production

36
Q

Biles salts

A

-emulsify fats globules allowing lipase access to triglycerides

37
Q

Pancreatic Lipases

A

hydrolyze ester bonds between fatty acids and glycerol backbone

38
Q

triglyceride lipase

A

removes one fatty acid from triglyceride

39
Q

diglyceride lipase

A

removes the second fatty acid to produce 2 fatty acids and a monoglycerol which can be transported across the intestine walls

40
Q

chylomicrons

A

once the fatty acids and monoglyceride get across the intestinal membrane they are reassembled into triglycerides and these lipoprotein complexes transport them via the lymph and the blood stream to the muscles and adipose tissues.

41
Q

Fat storage

A
  • highly reduced compounds with more energy potential from oxidation than sugars
  • most fats are stored in adipose tissues but can be in the muscle and liver too
42
Q

Hormone sensitive lipase

A

Glucagon and epinephrine activate PKA which activate hormone sensitive lipase which hydrolize free fatty acids and glycerol.
- this hydrolization must happen inorder to degrate triglycerides to FA and glycerols so that they can be released from adipose and be transported to energy requiring tissues.

43
Q

Lipolysis

A
  • induced by glucagon and epinephrine
  • FFA are transported to muscle, heart and other tissues for oxidation
  • Glycerols are transported to the liver for glycolysis or gluconeogenesis
44
Q

Degradation (Fatty acid activation)

A

upon arrival at the target cell saturated FFA is activated in two steps
1. Acyl adenylation with AMP
2. thioester formation to form acyl CoA
this must happen in the cytoplasm before transport to the mitochodria

45
Q

Degradation (Transport to the mitochondria)

A

FA must transported into the mitochondria as cartinine derivatives so the cytoplasm Acyl CoA is removed then the Acyl group carried by cartinine is reattached to a mitochondrial Acyl coA

46
Q

Beta oxidation

A

Once inside of the mitocchondria Acyl CoA go through 4 repeating reactions to get them converted to acetyl CoA so that it can go into the TCA cycle

  1. Oxidation
  2. Hydration
  3. Oxidation
  4. Thiolysis of beta keto group
47
Q

Step 1

A

Acyl CoA C-C bond oxidized and reduces FAD to FADH2

48
Q

Step 2

A

Water is added to get an alcohol group on carbon 3

49
Q

Step 3

A

Oxidation of the C-O bond reducing NAD+ to NADH

50
Q

Step 4

A

Thiolysis by beta ketothiolase enzyme(neucleophillic attack) to form Acyl CoA and Acetyl CoA

51
Q

Summary of FA degradation

A

each round of Betta oxidation shorten FA chain by 2 carbons and produces 1 NADH 2 FADH2 and 1 acetyl coA

52
Q

Unsaturated Fats degradation

A

the double bond require modifications prior to going through Beta oxidation which only synthesize even numbered saturated fats

53
Q

Ketone bodies

A

water soluble means of transporting acetyl groups from the liver via the blood stream to peripheral tissues like the heart and kidneys for oxidation in the TCA cycle.

54
Q

Ketone body formation

A

accumulation of acetyl coA from beta oxidation in the liver forming 3 hydroxybutyrate

55
Q

Depletion of TCA cycle

A

depletion of the TCA cycle due t diabetes or dietary imbalance leads to accumulation of ketone bodies as the concentration of Acetyl CoA rises

56
Q

Fatty acid synthesis

A
  • Carried out by fatty acid synthase in the cytoplasm only when energy needs have been met.
  • Uses acyl carrier protein instead of CoASH as an activator.
  • Starting material is malonyl ACP
57
Q

Transport to the cytoplasm

A

acetyl group transportedfrom the mitochondria matrix through the membrane and to the cytoplasm as citrate then it is converted again to cytoplasmic acetyl coA and OAA which can be oxidized to pyruvate in a biosynthesis reaction providing NADHP

58
Q

Acetyl carboxylase

A

carboxylation of Acetyl CoA to malonyl ACP provides energy for the rest of the synthetic reactions and is the committed step.

59
Q

FA synthesis

A

four reactions that mirrors degradation

  1. condensation of malonyl ACP and Acetyl ACP
  2. Reduction of ketone to alcohol converts NADPH to NADP+
  3. Dehydration of alcohol to an alkene
  4. Reduction of Alkene to alkane converting NADPH to NADP+
60
Q

Regulation of Lipid metabolism

A

-Energy charge is the primary regulator and ACC carboxylase is the main regulation point. When it is phosphorylated by AMP kinase it is inactive due to low energy

61
Q

Citrate allosteric effect

A

high levels of citrate will activate ACC to convert Acetyl CoA to malonyl ACP because we have a lot of energy and acetyl CoA

62
Q

Insulin Regulation

A

dephosphorylate ACC thereby activating. insulin is released when blood glucose is high a ay to get rid of it if we are already abundant in energy is to convert it to fat.

63
Q

Glucagon and Epinephrine

A

phosphorylate ACC because the body need to convert the fat to glucose or Energy

64
Q

Ketone bodies

A

produced by an accumulation of Acetyl CoA after degradation of FA decreases lipolysis and increase FA synthesis unless your diabetic then this signl is override by the low energy charge

65
Q

Eicosanoid Synthesis

A

produce a variety of signaling molecules duch as prostaglandin

66
Q

Prostaglandins

A

type of eicosanoid which areparacrine signals that induce inflammation

67
Q

Leukotrienes

A

type of eicosanoid associated with asthma and allergic responses

68
Q

Thromboxanes

A

vasoconstrictors that function in blood clotting.

Biochemistry (7 decks)

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