Week 8 Flashcards
(177 cards)
1
Q
What is responsible for turning Pyruvate into coA and why is this important?
A
Pyruvate dehydrogenase complex.
Allows it to enter the citric acid cycle.
2
Q
What does the Pryruvate dehydrogenase complex need?
A
Co-factors
3
Q
What are the 2 types of cofactors?
A
Catalytic
Stoichiometric
4
Q
What are catalytic cofactors?
A
Cofactors which are used by a complex and are regenerated.
5
Q
What are stoichiometric cofactors?
A
Cofactors which are used but not regenerated.
6
Q
Give examples of catalytic cofactors.
A
Thiamine
Lipoic acid Riboflavin
7
Q
Give examples of Stoichiometric cofactors.
A
Pantothenic acid
Aniacin
8
Q
What is PDH inhibited by?
A
High energy:
ATP
NADH
Acetyl coA
9
Q
What is PDH stimulated by?
A
Low energy
coA
NAD+
AMP
10
Q
What is the purpose of pyruvate dehydrogenase kinase?
A
Phosphorylates phyruvate dehydrogenase E1, making it less active.
11
Q
How does ADP affect kinase activity?
A
Inhibits kinase activity
12
Q
How do Acetyl coA and NADH affect kinase acitivyt?
A
Stimulate kinase activity
13
Q
How does kinase activity affect the PDH complex?
A
kinase inhibits PDH
14
Q
What is the purpose of pyruvate dehydrogenase phosphatase?
A
Removes phosphate from PDH making it more active.
15
Q
Where does the citric acid cycle take place?
A
Mitochondrial matrix
16
Q
How is the citric acid cycle linked to the electron transport chain?
A
3 NADH and 1 FADH2 are made from the citric acid cycle that supply electrons for the electron transport chain.
17
Q
When is carbon dioxide released in the Citric acid cycle?
A
Steps 3 and 4
18
Q
What are the 2 regulated steps of the citric acid cycle?
A
Isocitrate dehydrogenase and ketogultarate dehydrogenase.
19
Q
How does ADP affect the citric acid cycle?
A
Stimulates it
20
Q
How does ATP affect the citric acid cycle?
A
Inhibits it
21
Q
How many steps are there in the citric acid cycle?
A
8
22
Q
Write the overall reaction showing the formation of acetyl coA from pyruvate.
A
Pyruvate + coA + NAD+ =
Acetyl-coA + CO2 + NADH
23
Q
How many enzymes are present in the Pyruvate dehydrogenase complex?
A
3
24
Q
Where is Pyruvate dehydrogenase complex fund in Eukaryotes?
A
Mitochondria
25
Where is Pyruvate dehydrogenase complex found in prokaryotes?
Cytosol
26
What are the 3 enzymes of the Pyruvate Dehydrogenase Complex.
1. Pyruvate Dehydrogenase
2. Drihydrolipoyl Transacetylase
3. Dihydrolopoyl dehydrogenase
27
How many prosthetic groups are needed in Pyruvate dehydrogenase complex?
5
28
What are the prosthetic groups in the pyruvate dehyrogenase complex used as?
Co-factors
29
What are the 5 co-factors/ prosthetic groups used by the pyruvate dehydrogenase complex and what type of co-factor are each of them?
Thiamin - Thiamin Pyrophosphate - catalytic co-factor.
Riboflavin - Flavi Adenine Dinucleotide - Catalytic co-factor
Pantothenate - Coenzyme A - Stoichiometric co-factor
Niacin - Nicotinamide adenine dinucleotide - Stoichiometric co-factr
Lipoic acid - Catalytic co-facto
30
Why can't animals synthesise Glucose from Acetyl coA?
The formation of Pyruvate Dehydrogenase complex is irreversible.
31
How is Pyruvate Dehydrogenase complex regulated?
Allosterically and by covalent phosphorylation.
32
What inhibits Pyruvate dehydrogenase complex?
Acetyl coA and NADH
33
How does phosphorylation affect the pyruvate dehydrogenase complex?
Turns off the activity of the complex.
34
How does dephosphorylation of the pyruvate dehydrogenase complex affect its activity?
Activates the complex
35
How does phosphatase deficiency in the body cause lactic acid build up in relation to the pyruvate dehydrogenase complex?
If phosphate levels are low, the pyruvate dehydrogenase complex will remain inactive. This will mean that pyruvate cannot enter the citric acid cycle and is therefore converted to lactic acid.
= Lactic acidosis.
36
What are used to relay electrons from the citric acid cycle to the electron transport chain?
NADH and FADH2
37
What enzyme is used in step 1 of the citric acid cycle?
Citrate synthase
38
What happens in step 1 of the citric acid cycle?
Binding of oxaloacetate to Citrate synthase causes a conformational change which allows the next substrate to bind to Acetyl coA.
A second conformational change also forms Citrate.
39
What enzyme model does citrate synthase use in the citric acid cycle?
Induced fit model
40
Outline the reaction for step 1 of the citric acid cycle.
Acetyl coA + Oxaloacetate (+ Citrate synthatase) = Citrate
41
What enzyme is used in step 2 of the citric acid cycle?
Aconitase
42
What happens in step 2 of the citric acid cycle?
Aconitase catalyses the isomerization reaction by removing and then adding back water to cis-aconitate at different positions.
43
What type of reaction occurs in step 2 of the citric acid cycle?
Isomerization
44
What enzyme is used in step 3 of the citric acid cycle?
Isocitrate dehydrogenase
45
What happens in step 3 of the citric acid cycle?
Isocitrate is covered to A-Ketoglutarate.
46
How many isoforms of Isocitrate dehyrodgenase are there?
2
47
What are the two electron acceptors used by isocitrate dehydrogenase?
NAD+ and NADP+
48
What enzyme is used in step 4 of the citric acid cycle?
A-Ketoglutarate dehydrogenase
49
What happens in step 4 of the citric acid cycle?
A-ketoglutarate is converted to Succinyl CoA
50
What is used as an electron acceptor in step 4 of the citric acid cycle?
NAD+
51
What enzyme is used in step 5 of the citric acid cycle?
Succinyl coA synthetase
52
What happens in step 5 of the citric acid cycle?
Hydrolysis of the thirster bond leads to formation of a phosphodiester bond with an inorganic phosphate. This phosphate is then transferred to Histidine residue of the enzyme and the phosphate is transferred to GDP to form GTP.
53
What enzyme is used in step 6 of the citric acid cycle?
Succinate Dehydrogenase
54
Where is succinate dehydrogenase enzyme found?
Tightly bound to the inner mitochondrial membrane.
55
What happens in step 6 of the citric acid cycle?
Oxidation of succinate to fumarate.
56
What does the enzyme 'succinate dehydrogenase' depend on?
FAD
57
Which enzyme of the citric acid cycle is found bund to the inner mitochondrial membrane?
Succinate dehydrogenase
58
What enzyme is used in step 7 of the citric acid cycle?
Fumarase
59
Give a feature of fumarate enzyme which causes its function.
It is highly stereospecific so has the ability to discriminate between enantiomers of substrates or products.
60
What are stereospecific enzymes?
They can discriminate between enantiomers of substrates and products.
61
What happens during step 7 of the citric acid cycle?
Fumarate is converted to L-Malate via a hydrolysis reaction.
62
What type of reaction is occurring during step 7 of the citric acid cycle?
Hydrolysis
63
What enzyme is used in step 8 of the citric acid cycle?
L-Malate dehydrogenase
64
What happens in step 8 of the citric acid cycle?
Oxidation of Malate to Oxaloacetate
65
What does the enzyme L-Malate dehydrogenase depend on?
NAD+
66
What type of reaction is occurring in step 8 of the citric acid cycle?
Oxidation
67
What are used to regulate the citric acid cycle?
Concentrations of ATP, GTP and NADH
68
Where are the control points of the citric acid cycle?
PDH.
Isocitrate dehydrogenase.
A-Ketoglutarate dehydrogenase.
69
How many of the steps in the citric acid cycle are reversible ?
5
70
How many of the steps in the citric acid cycle are irreversible ?
3
71
What type of acid is citric acid?
Tricarboxylic acid
72
How many carbon are in Acetyl coA?
2
73
How are the carbon molecules of Acetyl coA eventually removed in the citric acid cycle and what enzymes does this require?
Removed as CO2 in separate reactions.
Decarboxylase enzymes.
74
How many carbon atoms does Oxaloacetate contain?
4
75
How many carbon atoms does citric acid contain?
6
76
What happens to the NAD+ molecules used in the citric acid cycle?
They are reduced to NADH + H+
77
How many NAD+ molecules are used in the citric acid cycle?
3
78
What happens to the FAD used in the citric acid cycle?
Reduced to FADH2
79
How many FAD molecules are used in the citric acid cycle?
1
80
How many ADP or GDP molecules are used in the citric acid cycle?
1
81
What is the overall purpose of the electron transport chain?
Synthesises ATP via oxidative phosphorylation
82
What is complex I of the electron transport chain?
NADH ubiquinone reductase
83
What is complex II of the electron transport chain?
Succinate Ubiquinone Reductase
84
What is complex III of the electron transport chain?
CoQ-cytochrome c reductase
85
What is complex IV of the electron transport chain?
Cytochrome C oxidase
86
What are the components of Complex I electron carrier and what happens to these?
2 redox proteins:
Flavin mononucleotide which is reduced by NADH to form FMNH2
1-5 iron-sulphur proteins which are reduced by NADH.
87
What is the overall function of carrier I of the electron transport chain?
Enzyme catalyses the oxidation of NADH proton pumping site.
88
What are the components of electron carrier II ?
Succinate dehydrogenase
FAD
1-3 iron-sulphur proteins
89
What is the purpose of complex II in the electron transport chain?
Catalyses the oxidation of FADH2 by CoQ.
90
What is the purpose of CoQ in the electron transport chain?
Shuttles electron between complexes I, II and III
91
What are the components of electron carrier III?
b cytochromes
Ubiquinol-cytochrome
c1 iron-sulphur proteins
92
What is the purpose of electron carrier III in the electron transport chain?
Catalyses oxidation of CoQ by cytochrome c proton pumping site
93
What is the purpose of cytochrome C in the electron transport chain?
shuttles electrons between complex III and IV.
94
What are the components of electron carrier IV?
Cytochromes a and a3
| Two copper atoms
95
What is the purpose of electron carrier IV in the electron transport chain?
Catalyse the four electron reduction of H2O proton pumping site.
96
Where is the electron transport chain?
Cristae of the mitochondria
97
How does the free energy of electrons alter along the electron transport chain?
Reduces
98
What type of mechanism is Chemiosmosis?
energy coupling mechanism
99
Outline the process of Chemiosmosis in the electron transport chain.
Electron transfer causes proteins to pump H+ from the mitochondria matrix into the inter membrane space.
H+ then moves back across the membrane passing through ATP synthase channels.
ATP uses the exergonic flow of H+ to drive phosphorylation of ATP.
100
What is the overall purpose of chemiosmosis?
The use of energy in a H+ gradient to drive cellular work.
101
What is exergonic flow?
Positive flow of energy from the surroundings.
102
What is the H+ gradient in the electron transport chain often called?
Proton motive force
103
How many ATP molecules are formed during oxidative phosphorylation per NADH and FADH2 molecules?
2. 5 per NADH
| 1. 5 per FADH2
104
How any ATP molecules are formed during glycolysis?
2
105
How many ATP molecules are formed during the citric acid cycle?
2
106
How many ATP molecules are produced in the election transport chain.
26
107
What type of phosphorylation occurs in Glycolysis?
Substrate level
108
What type of phosphorylation occurs in the citric acid cycle?
Substrate level
109
What type of phosphorylation occurs in the electron transport chain?
Oxidative
110
What are the general purpose of uncouplers?
Inhibit oxidative phosphorylation
111
How do uncouplers work to prevent ATP formation in the ETC?
They uncouple the electron transport chain from oxidative phosphorylation.
They carry protons across the mitochondrial membrane making it leaky for H+. This means the pH and electric gradient is not generated so ATP can't be synthesised.
112
What type of organisms use uncoupling methods and why?
Hybernating animals - to stay warm in winter since they don't need ATP for anabolic processes whilst they are resting.
113
Give examples of uncouplers.
Thermogenin
| 2,4,-dinitrophenol
114
Why do newborn mammals use uncoupling?
To generate heat
115
How do newborn mammals generate heat by using uncoupling?
Uncoupling protein one allows free H+ transport across the mitochondrial membrane. Thermogenin present in brown fat then provides energy from the proton motive force to dissipate as heat.
116
Why are NADH and FADH2 high energy molecules?
They both contain a pair of electrons with a high transfer potential.
117
What is oxidative phosphorylation?
The process in which ATP is formed as a result of he transfer of electrons from NADH or FADH2 to O2 by a series of electron carriers.
118
What type of organisms does oxidative phosphorylation occur in?
Aerobic organisms.
119
How many molecules of ATP are produced per molecule of glucose from all of the processes ?
30
120
What are the final products of oxidation of glucose?
Carbon dioxide and water
121
What type of motive force is present in the citric acid cycle?
Electron motive force
122
What type of motive force is present in the electron transport chain?
Proton motive force
123
Where does the citric acid cycle occur in Eukaryotes?
Mitochondria
124
What are the fuel molecules for the citric acid cycle?
Carbon compounds which are capable of being oxidised.
125
What electron carriers are used in the citric acid cycle?
FAD and NAD
126
How many molecules of ATP do the electron carriers (FAD and NAD) made during oxidative phosphorylation?
9
127
Approximately how many grams of ATP do humans have in their body at any given time?
250g
128
How many times is each ATP recycled in the body every day?
Around 300
129
By what process are the ATP molecules produced recycled in the body?
By oxidative phosphorylation
130
What regulatory enzymes control glycolysis
Phosphofructokinase
Hexokinase
Pyruvate
131
What type of reactions do Glycolytic regulatory enzymes catalyse?
Irreversible
132
What are the main roles of glycolysis?
To degraded Glucose to generate ATP.
| To provide building blocks to synthesise cellular components.
133
What happens to the Pyruvate produced by anaerobic Glycolysis
The pyruvate is reduced to Lactate.
134
By what type of reaction is lactate produced from Pyruvate?
Reduction
135
What is regenerated during the metabolism of Pyruvate to Lactate during Anaerobic Glycolysis?
NAD+
136
When is NAD+ regenerated during anaerobic Glycolysis?
When Pyruvate is metabolised to Lactate.
137
Outline what occurs during alcoholic fermentation of Pyruvate
Pyruvate is cleaved into acetaldehyde and carbon dioxide and then reduced to ethanol by alcohol dehydrogenase.
138
What is a fermentation reaction?
An energy yielding pathway with no net change to the oxidation states of products compared with substrates.
139
What are Galactose and Fructose converted to during Glycolysis?
Glycolytic intermediates.
140
What are the pre-cursor molecule for Gluconeogenesis?
Non-carbohydrate molecules
141
Where does Gluconeogenesis occur?
Mainly in the liver but also in the kidneys.
142
Where is Oxaloacetate used for Gluconeogenesis produced?
In the mitochondrial matrix
143
What must occur to pyrutavte to produce Oxaloacetate?
Carboxylation
144
Where is Oxaloacetate used for Gluconeogenesis?
In the cytoplasm of the mitochondria.
145
What is required for Oxaloacetate to leave the mitochondria?
Specific transported protein systems
146
What does Oxaloacetate leave the mitochondria in the form of?
Malate
147
How is Malate converted back into Oxaloacetate and where does this occur?
Deoxidised in the cytoplasm
148
In most tissues, when does Gluconeogensis end?
When fructose-6-phosphate is converted to Glucose-6-phosphate
149
What happens to Glucose-6-phosphate to produce free glucose by gluconeogeneie?
Glucose-6-phosphate is transported to the lumen of the ER where it can be hydrated to Glucose by Glucose-6-phosphatase.
150
Where is the enzyme Glucose-6-phosphatase found?
Bound to the ER membrane
151
What are Glucose transporters used for?
To mediate downhill movement of Glucose across the plasma membrane.
152
Describe the structure of glucose transporters.
12 trans membrane helix structure
153
What type of reaction is the metabolism of Glucose?
Redox
154
During the metabolism of Glucose, what is oxidised and what is reduced?
Glucose is oxidised and oxygen is reduced.
155
What are redox couples?
Have one or two electron donors and acceptors.
156
What are the features of strong reducing agents?
They donate electrons easily
157
What are the features of strong oxidising agents?
They gain electrons easily
158
What is oxidation?
Loss of electrons
159
What is reduction?
Gain of electrons
160
What is the terminal electron acceptor of the electron transport chain.
Oxygen
161
How many electrons can oxygen accept at the end of the electron transport chain?
One at a time
162
How many electrons must oxygen accept as the terminal electron acceptor to b converted into water?
4
163
How can the energy levels of electrons be raised after they have passed through the electron transport chain?
By photosynthesis
164
What does NAD+ accept during Glycolysis to yield NADH?
2 electrons and a proton.
165
How are the electrons transferred from NAD+ to NADH in glycolysis?
They are transferred as part of a hydride ion.
166
Where are NAD+/NADH redox couples found within the cell?
Bound to proteins or found freely in the cytosol.
167
What is the purpose of alcohol dehydrogenase?
Protects the liver from the toxic effects of ethanol.
| Couples oxidation of alcohol with reduction of NAD+.
168
What is NAD+ reduced into?
NADH
169
How is NAD+ regenerated from NADH?
By the reduction of pyruvate to lactic acid:
Pyruvate accepts 2 electrons from NADH and is reduced into lactate.
NADH is oxidised to NAD+.
170
Where does the conversion of NADH to NAD+ couples with Pyruvate reduction frequently occur?
In the muscles during strenuous activity.
171
How many electrons can FAD accept at a time?
1 or 2
172
Where can FAD be found in cells?
Bound to proteins
173
Where is Coenzyme Q found in the cells and how is it able to reach this area?
Freely associated with the membranes. IT is able to dissolve freely in the lipid bilayer due to its unsaturated fatty acid side chain which is attache to its sixth-member ring.
174
What are Cofactors?
A non-amino acid entity which associates reversible with the enzyme active site.
175
What are prosthetic groups?
A non-amino acid entity which binds irreversibly to the active site of enzymes.
176
Give an example of a cofactor
NAD+
| NADH
177
Give an example of a prosthetic group
FAD
