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Biochemistry 2 > Citric acid cycle and electron transport chain > Flashcards

Citric acid cycle and electron transport chain Flashcards

1
Q

Pathways that metabolize carbohydrates

A 
Glycolysis
Glucoenogenesis
Glycogenesis
Glycogenolysis
PPP
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2
Q

Pathways for protein metabolism

A 
Transamination
Urea cycle
AA catabolism
AA synthesis
Synthesis of AA derivatives
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3
Q

Pathways for synthesis of fat metabolism

A

Beta-oxidation
FA synthesis
TG synthesis
Cholesterol synthesis

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4
Q

Nucleic acids require precursors from what food groups

A

From carbohydrates and proteins

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5
Q

How can we get acetyl-CoA

A

Beta-oxidation
Some AA (leucine, threonine,etc.)
Pyruvate

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6
Q

Conversion of pyruvate to acetyl-CoA ( what enzymes , what products)

A

Pyruvate dehydrogenase complex(PDC) (3 enzymes) uses CoA-SH and NAD+ to convert pyruvate to acetyl-CoA

Products: CO2, NADH

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7
Q

What type of reaction is the conversion of pyruvate to Acetyl-CoA

A

Oxidative decarboxylation

Irreversible

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8
Q

Each cluster of PDC has how many copies of 3 enzyme clusters?

A

60 copies

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9
Q

What are three enzymes within PDC

A

Pyruvate dehydrogenase (E1)

Dihydrolipoyl transacetylase (E2)

Dihydrolipoyl dehydrogenase (E3)

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10
Q

Explain the mechanism of pyruvate conversion to acetyl-CoA

A

Pyruvate is taken by TPP arm, which is on enzyme 1 and the carboxylic group is removed in the form of CO2. The leftover is hydroxyethyl

Hydroxyethyl is then transferred to another prosthetic group: lipoate on enzyme 2, which becomes acyl lipoyllysine. This interacts with CoA-SH and converts to acetyl-CoA

Lipoyllysine is left in reduced form, that cannot accept incoming hydroxyethyl, so it is oxidized by third prosthetic group FAD , FAD->FADH2 and gives H2 to NAD+

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11
Q

TPP arm stands for

A

Thiamine PyroPhosphate

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12
Q

How many intermediates in TCA cycle

A

9

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13
Q

How many steps and enzymes are there in TCA cycle

A

8

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14
Q

What are enzymes of TCA cycle

A

So———-citrate Synthetase

At———-Aconitase

Another———-Aconitase

Dance———-isocitrate Dehydrogenase

Devon———-alpha-ketoglutarate Dehydrogenase

Sipped———-Succinyl-CoA Synthetase

Down———-Succinate Dehydrogenase

Five———-Fumarase

Drinks———-malate Dehydrogenase

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15
Q

What are 3 steps that are irreversible

A

Acetyl-CoA->citrate

Isocitrate ->alpha-ketogluterate

alpha-ketogluterate->succinyl-CoA

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16
Q

Why it is important that TCA cycle has only 3 irreversible reactions

A

So it has entering and exiting points for other cycles- amphybolic

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17
Q

How many carbons do acetyl-CoA donate

A

Acetyl-CoA donates 2 carbons to 4 carbon compound (oxaloacetate)

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18
Q

Two carbons of Acetyl-CoA do not contribute _____

A

Its carbons to CO2 in the first pass

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19
Q

Overall equation for TCA cycle

A

2 CO2+3NADH+1FADH2+1 ATP

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20
Q

What enzymes produce electron carriers in TCA cycle

A

NADH: isocitrate, alpha-ketogluterate
and malate dehydrogenases

FADH2:succinate dehydrogenase

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21
Q

At what steps we get CO2 in TCA cycle

A

Isocitrate ->alpha-ketogluterate

alpha-ketogluterate->succinyl-CoA

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22
Q

Why the step of conversion of succinyl-CoA to succinate to succinyl-CoA dehydrogenase is important

A

It uses ATP usually, but as it is a reverse reaction it produces one ATP

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23
Q

What are anaplerotic reaction

A

Replenishing reactions that feed TCA cycle

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24
Q

Citrate can be taken out of TCA for

A

FAs

Sterols

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25
alpha-ketogluterate can be taken out of TCA for
Transamination->glutamate
26
Succinyl-CoA can be used out of TCA cycle for
Porphyrins | Heme
27
Oxaloacetate can be used outside of TCA
Glucoenogenic pathway Used in AAs synthesize
28
Anaplerotic reactions for replenishing oxaloacetate with enzyme and in what tissues
Pyruvate->oxaloacetate (pyruvate carboxylase)->liver and kidney Phosphoenolpyruvate->oxaloacetate with PEP carboxykinase in heart and and with PEP carboxylase
29
Malate can be regenerated from
Pyruvate with malic enzyme
30
Classical regulations of TCA cycle
By regulation of irreversible reactions. Activated by substrates, inhibited by products
31
an additional Pyruvate conversion regulation
by phosphorylation on enzyme 1-> inactivation
32
Succinyl-CoA regulates which two enzymes and for what
It inhibits citrate synthase and KDH ( alpha-ketogluterate complex) to regulate alpha-ketogluterate for AA metabolism
33
What ion activates TCA cycle
Ca
34
Do FAs contribute to gluconeogenesis
Odd number FA lead to succinate-> imbalance Succinate enter TCA cycle->oxaloacetate->gluconeogenesis Also acetyl-CoA can be converted to ketone bodies Acetone can be converted to methylglyoxal or 1,2-Propanediol
35
Energy from ___ is used to synthesize ATP
Reduced fuels
36
What are reduced fuels
CHO Lipids AA
37
What happens in oxidative phosphorylation
Energy from NADH and FADH2 is used for ATP synthesis
38
3 types of electron carriers
Coenzyme Q Cytochrome C Iron-sulfur complex
39
What is the most important feature of coenzyme Q
It is a mobile electron carrier
40
Other names for coenzyme Q
(ubiquinone-oxidized or ubiquinol-reduced)
41
What does Coenzyme Q do
Transfers electrons from complex 1/2 to Complex 3
42
What happens first at electron transport chain
NADH along with another H+ donates 2 protons to iron-sulfur complex ultimately converting ubiquinine to ubiquinol
43
Sources of NADH
Beta-oxidation -1 NADH per cycle Glycolysis- 2NADH Pyruvate to Acetyl-CoA 1 NADH AA oxidation to pyruvate, etc.
44
Another name of complex II in electron transport chain (ETC)
succinate dehydrogenase
45
What does succinate dehydrogenase do
Takes protons from FADH2 to put it ubiquinone
46
Acetyl-CoA dehydrogenase is present in
First enzyme for beta-oxidation Electron transport chain (takes electrons form FADH2 and ultimately donates it to ubiquinone)
47
Complex I is ____ of the four complexes
The largest : 43 subunits encoded by nuclear and mitochondrial genes
48
How many hydrogens does complex I throw in intermembrane space
4
49
How many hydrogens is actually used by complex I
NADH+Q+5H+=NAD+QH2+4H So it is actually working with 6 hydrogens
50
What is a cofactor for complex II
FAD
51
Is there a movement of hydrogens in complex II
No
52
What happens at complex III of electron transport chain
Ubiquinol transfers its 2 electrons to cytochrome C and oxidized coenzyme Q is thrown into the membrane. 2 hydrogens from 2 electrons are thrown out By cytochrome C cannot accept two electrons at a time. So for now oxidized coenzyme Q get one electron and becomes an intermediate called ubisemiquinone. At stage 2, ubisemiquinone accepts one more electron from upcoming ubiquinone and one more cycle from cytochrome C and takes 2 hydrogens form the matrix and becomes a fully reduced ubiquinol
53
So what is a net equation at complex III
2 cytochrome C get reduced 4 H+ get thrown out One QH2 comes in and one Q is thrown out in the membrane
54
What happens at complex IV
Cytochrome donates its electrons and gets oxidized and oxygen ( as a terminal acceptor) receives electrons
55
Per one molecule of water how many cytochromes you need, hydrogens and oxygen you need
2 2 hydrogens 1/2 oxygen
56
how many electrons are pumped at complex IV
2
57
How many electrons do NADH and FADH2 pumps
NADH- 10H+ | FADH2-6 H+
58
What is the equation for 1 NADH and 1 FADH2 in the electron transport chain
1NADH+11H(matrix)+1/2O2--->NAD+10H+(inter)+H2O FADH2+6H(m)+1/2O2---->FAD+6H(inter)+H2O
59
What is respirosome
This word shows that electron transport chain functions as one unit
60
ATP synthase needs___ for synthesize of ATP
Electrochemical gradient
61
What systems contribute to electrochemical gradient of H+
Active transport Complex I and IV Release of protons into intermembrane space ->oxidation of QH2 (complex III) Chemical removal of protons from the matrix -> reduction of Q (complex I,II,III) and oxygen (complex IV)
62
Two subunits of ATP synthase
F0-> in the membrane-> transports protons dwon the gradient; transfers energy to F1 F1-> in the matrix-> enzymatic capacity in both directions
63
How many dimensions are there in ATP synthase
3 parts that are the same form alpha and beta
64
How three alpha and beta parts are connected
with gamma-shaft
65
How many hydrogens do you need for synthesis of ATP
To turn the ATP synthase itself , you need three hydrogens from intermembrane space to matrix + 1 hydrogen in the matrix for the transfer of P to ADP
66
How many ATP NADH and FADH2 yield
NADH: 10/4=2.5 FADH2: 6/4=1.5 ATP
67
How many subunits ATP synthase do ATP
ALL of them, when the shaft turns in their direction, ATP is thrown out
68
How do we get NADH from the cytoplasm to matrix if the inner membrane is impermeable to NADH?
Malate-Aspartate shuttle Oxaloacetate is converted to malate with NADH and malate dehydrogenase Now there is malate-alpgaketogluterate trasnporter and malate is in matrix. Malate-> oxaloacetate-> yield NADH To balance it out, oxaloacetate is converted to aspartate with aspartate aminotrasnferase and converting glutamate to alpha-ketogluterate Aspartate is thrown out through glutamate-aspartate shuttle
69
Malate-aspartate shuttle is used by
Most cells( brain and muscles as well)
70
What shuttle is used for NADH transport in skeletal muscle and brain
G3P shuttle
71
Explain G3P shuttle
NADH is used for conversion of dihydroxyacetone phosphate to G3P with cytosolic glycerol 3-phosphate dehydrogenase G3P comes to intermembrane space, where there is mitochondrial glycerol 3-phosphate dehydrogenase bound to the inner membrane. This enzyme converts G3P back to dihydroxyacetone and puts two hydrogens on FAD->coenzyme Q->complex 3
72
What shuttle yields more energy? and what is strange about it
Malate-aspartate shuttle gives more ATP because it uses NADH, but G3P shuttle uses FADH2, which is strange because G3P shuttle is in muscles that need more energy, but his shuttle is more quick, because it goes directly to respirosome
73
So how many ATP from complete oxidation of glucose
30 or 32 | Depends on which shuttle to take NADH from cytoplasm from glycolysis to the matrix ( 2NADH->3 ATP or 5 ATP)
74
one palmitoyl-CoA yield how many ATPs
108
75
Regulation of oxidative phosphorylation
- Any substrate acts positively on the reaction, when any product inhibits - Acceptor control of respiration (ADP). It depends on how much ADP is available , not oxygen. As soon as it gets available, respiration starts
76
Acceptor control is measured with
Mass action ratio ATP/ADP*P
77
ATP is synthesized when
It is utilized, it is synthesized as fast as it is utilized
78
Mitochondrial respiration in brown adipose tissue
There is uncoupling protein (UCP1). It provides an additional route for the flow of protons to the matrix. These hydrogens lead to heat synthesize
79
UCP1 another name is
Thermogenin

Biochemistry 2 (17 decks)

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