Cellular metabolism Flashcards
1
Q
What is metabolism?
A
Highly integrated network of chemical reactions with thousands of reactions taking place.
2
Q
What do linked chemical reactions form?
A
Interdependent metabolic pathways.
3
Q
Is pathway regulation common or uncommon?
A
Common.
4
Q
Why is metabolic regulation required?
A
Energy to function, no external supply, energy intake intermittent, expenditure continuous, need to store energy and release.
5
Q
How much can exercise increase metabolic rate?
A
Up to 20x resting level.
6
Q
Other than exercise what be give a sudden increase in metabolic rate?
A
Severe illness (infection).
7
Q
Metabolic regulation?
A
Covers distribution and storage of nutrients after meals, release from stores, delivery to and utilisation in tissues.
8
Q
What level does metabolic regulation work at?
A
Molecular level, mainly by modulation of enzyme activities.
9
Q
Three principle ways for regulation of metabolic pathways?
A
Levels and accessibility of substrates, amounts of metabolic enzymes, modulation of catalytic activities of enzymes.
10
Q
What is number of enzyme molecules a function of?
A
Rate of synthesis and degradation (both tightly controlled).
11
Q
Enzyme turnover determined by?
A
Alteration of transcription factors, stability of mRNA, rate of translation, rate of protein degradation.
12
Q
Are changes in amount of enzyme present in cell slow or fast?
A
Relatively slow, ranging from minutes to hours.
13
Q
What two processes control levels and accessibility of substrates?
A
Thermodynamics and compartmentation.
14
Q
What processes control metabolic enzymes?
A
Rate of transcription and degradation.
15
Q
Examples of catalytic activities that can be modulated?
A
Allosteric regulation, covalent modification, association with regulatory proteins.
16
Q
Are metabolic pathways interdependent?
A
Yes.
17
Q
What are the key enzymes that control flux of substrates through a pathway?
A
Rate limiting, commitment step.
18
Q
What is Allosteric derived from?
A
Greek word meaning ‘the other’ (the other site aside from active site).
19
Q
Characteristic of allosteric enzyme?
A
Has a site distinct from substrate binding site.
20
Q
What is the term for the ligands that bind to allosteric sites?
A
Allosteric effectors or modulators?
21
Q
What does ligand binding cause?
A
Conformational changes so affinity for substrate or other ligands changes.
22
Q
What are positive ligands called?
A
Activators.
23
Q
What are negative ligands called?
A
Inhibitors.
24
Q
End product/ feedback inhibition steps?
A
Binds covalently to allosteric site, binds depending on conc and affinity, induces conformational changes, affects active site.
25
Regulatory enzyme steps?
Several sites, each binds a ligand, conformation of active site reflects summation of signals.
26
What is needed for adenylate control?
ATP to ADP/AMP = ion transport, syntheses, work.
ADP/AMP to ATP = metabolic fuels, oxygen.
27
What does electron transport and oxidative phosphorylation maintian in adenylate control?
[ATP] > [ADP] >> [AMP]
28
What does adenylate kinase interconnect in adenylate control?
ATP + AMP (reversible reaction) to 2ADP.
29
Reciprocal relationship between what in adenylate control?
Increase [ATP] = decrease [AMP] and vice versa.
30
What does the energy status of a cell control?
Many metabolic reactions and pathways.
31
What is the energy charge range?
0 (all AMP) to 1 (all ATP).
32
What inhibits ATP generating pathways?
A high energy charge.
33
What stimulates ATP utilising pathways?
High energy charge.
34
Catabolic ATP-generating pathways?
Glycogenolysis, glycolysis, beta-oxidation.
35
Anabolic ATP-utilising pathways?
Glycogenesis, gluconeogenesis, lipogenesis, purine/ pyrimidine syntheses.
36
Why is modification of existing protein structure better than changing enzyme levels?
Much quicker process.
37
How have control of pathways evolved?
To maintain energy change within buffered narrow limits.
38
How does modification of protein structure happen?
Covalent modification.
39
What are the three types of covalent modification?
Adenylation, methylation, phosphorylation.
40
What is the most common type of covalent modification?
Phosphorylation.
41
Covalent modification?
Attachment of functional group covalently to an amino acid side chin, attachment selective and enzyme catalysed, induces conformational change.
42
In what ways does phosphorylation/dephosphorylation tend to alter conformation of a protein?
Changes Vmax and Km, sensitivity to substrates inhibitors and activators.
43
Is the new conformation permanent?
Locked in new conformation.
44
What makes covalent modification processes useful?
Reversible reactions.
45
What generally triggers covalent modification?
An external signal leading to amplification of signal.
46
What is glycolysis?
Ancient pathway employed by wide range of organisms from simplest bacteria to humans, conversion of glucose to pyruvate.
47
Characteristics of glycolysis?
Anaerobic, located in cytosol of Euk cell.
48
Why is glucose important?
Common fuel in most cells, only fuel red blood cells use in mammals.
49
Summarise stage 1 of glycolysis.
Trapping and destabilising glucose to produce 2x 3C molecules, energy required.
50
How much ATP required per glucose molecule in stage 1 of glycolysis?
2x.
51
Summarise stage 2 of glycolysis.
Oxidation of 3C molecules to pyruvate, energy generated.
52
How much energy generated in stage 2 of glycolysis?
4x ATP and 2NADH per glucose molecule.
53
Summarise step 1 of stage 1 - trapping glucose.
Glucose in via facilitated diffusion through transport proteins, trapped by phosphorylation, glucose 6-phosphate is -ve so cannot diffuse out, addition of phosphate begins destabilisation, further metabolism.
54
What does HexoKinase do?
Can phosphorylate variety of hexose sugars via induced fit enzyme action.
55
Why does the HexoKinase reaction favour glucose 6-phosphate?
Equilibrium, irreversible reaction.
56
What inhibits regulatory enzyme of glycolysis?
Glucose 6-P (feedback inhibition).
57
Summarise step 2 stage 1 - formation of fructose 6-P.
Isomerisation of glucose 6-P to fructose 6-P, convert from one isomer to another by Tautomerisation.
58
What kind of reaction is isomerisation of glucose 6-P to fructose 6-P?
Completely reversible reaction, enzyme phosphoglucose isomerase.
59
Summarise step 3 stage 1 - second phosphorylation reaction.
Enzyme phosphofructokinase, allosteric enzyme sets pace of glycolysis, inhibited by ATP, citrate and H+ ions, stimulated by AMP, ADP, Fruc 2,6-bisP.
60
Summarise steps 4+5 stage 1 - trapping and destabilising.
Split fructose 1,6-bisP into 3C fragments, cleavage of this catalysed by Aldolase to yeild 2x TP, reversible under normal conditions.
61
What is and isn’t on direct pathway of glycolysis?
Glyceraldehyde 3-P is, DHAP is not.
61
What needs to happen to DHAP to avoid 3C fragment capable of generating ATP being lost?
Needs to be converted to G 3-P.
62
What enzyme catalyses reversible reaction of DHAP to G 3-P?
Triose Phosphate isomerase (TIM).
63
How much is in DHAP from at eqm?
96%.
64
Why is eqm pushed towards G 3-P formation?
Subsequent reaction of glycolysis and removal of G 3-P.
65
By what factor does TIM accelerate isomerisation?
Factor of 10^10.
66
What is triose phosphate isomerase?
Kinetically perfect enzyme.
67
What is the rate limiting step in regards to TIM?
Diffusion-controlled encounter of substrate and enzyme.
68
How many molecules of G 3-P from F 1,6-bisP?
2x.
69
Summarise step 6 stage 2 - energy generation glycolysis.
Formation of high energy bond, G 3-P oxidised and phosphorylated by enzyme G 3-P dehydrogenase, transfers high energy e- from NAD+ to form NADH.
70
What is the resulting intermediate 1,3-bisposphosphoglycerate?
An acyl phosphate.
71
What oxidises aldehyde to carboxylic acid?
NAD+.
72
What joins to carboxylic acid?
Orthophosphate.
73
Summarise step 7 stage 2 - energy generation glycolysis.
ATP generated from 1,3-bisPglycerate, substrate level phosphorylation.
74
What does glucose yeild?
2x 3C intermediates.
75
How many ATPs generated per glucose molecule?
2 ATPs.
76
Summarise steps 8-10 stage 2 glycolysis.
Generation of ATP and pyruvate formation (2 per glucose), phosphorylation group on 3-Pglycerate shifts followed by dehydration, formation of C=C, increases potential phosphorylation group transfer.
77
What does pyruvate kinase do?
Irreversible transfer of phosphorylation group to form ATP, substrate level phosphorylation, regulatory enzyme activated by F1,6bisP, inhibited by ATP and alanine.
78
Glycolysis equation.
glucose + 2NAD+ + 2ADP + Pi ———> 2 pyruvate + 2NADH + 2ATP + 2H+ + 2H2O.
79
What would make glycolysis not proceed for as long?
If pyruvate was final metabolite as redox balance would not be maintained.
80
Why must NAD+ in cells be replaced?
Limited amounts in cells.
81
What is NAD+ converted to in glycolysis?
NADH.
82
What happens if [NAD+] decreases?
Glycolysis cannot continue.
83
What does the transferral of electron from NADH to oxygen produce?
H2O, ATP, NAD+.
84
Where are the electrons transferred to from NADH if no O2 present?
Pyruvate to form lactate or ethanol and NAD+.
85
Ethanol formation (yeast) summary.
Anaerobic, glucose + 2H+ + 2ADP + 2Pi ——-> 2 ethanol + 2CO2 + 2ATP + 2H2O.
86
Where does lactic acid formation occur?
Microorganisms and in higher organisms when oxygen limited (intense exercise).
87
What does lactic acid do?
Regenerates NAD+ for step 6 glycolysis.
88
What happens during aerobic conditions of glycolysis?
More energy extracted by TCA cycle and OX PHOS.
89
What is pyruvate oxidised to in mitochondria?
Acetyl CoA.
90
What happens do NADH generated at step 6 glycolysis?
Cannot enter mitochondria, NAD+ regenerated indirectly by OX PHOS.
91
Why do animals store energy as glycogen?
Controlled breakdown and synthesis maintains blood glucose levels, glucose only fuel for brain, glucose from glycogen readily mobilised, energy under anaerobic conditions.
92
What are the two major sites of glycogen storage?
Liver and muscle.
93
How is glycogen stored?
As insoluble granules in cytosol.
94
What are the pathways of glycogen metabolism like in Liver and Muscle?
The same pathways, differing regulation.
95
What is glucose uptake from the blood facilitated by?
Transport proteins.
96
What is GLUT2?
Present in liver and beta cells of pancreas, high capacity, low affinity transporter, takes up lots of glucose when lots is present.
97
What is GLUT4?
Present in muscle and fat cells, insulin leads to rapid increase so increasing uptake, amount of transporters in membranes increased.
98
What is the first step of glycogenesis?
Conversion of glucose to glucose 6-P, HexoKinase phosphorylates glucose to trap in cell, inhibits enzyme.
99
What is the isozyme that the Liver is rich in?
Glucokinase, not inhibited by glucose 6-P, high Km, provides glucose 6-P, gives first call of glucose but not wasted.
100
What is the second step of Glycogenesis?
Glucose 6-p converted to Glucose 1-P by phosphoglucomutase.
101
What does active mutase enzyme contain?
Phosphorylated serine residue.
102
What is the third step of glycogenesis?
Glucose 1-P is activated by an enzyme UDP-glucose pyrophosphorylase
103
What is tagging?
Breakdown of protein.
104
What is deamination of amino acids?
Removal of N.
105
What does the urea cycle do?
Produces urea.
106
What process does alanine metabolism include?
Gluconeogenesis.
107
Where does N fixation happen?
Amino acids synthesis.
108
What is Ubiquitin?
Attached to proteins, marks them for degradation, 3 steps, 3 enzymes, N terminal rule/ degron.
109
Name the three enzymes/ steps of Ubiquitin.
Activating enzyme (E1), conjugation enzyme (E2), protein ligase (E3).
110
What does the amino acid sequence impact?
Half life of protein.
111
What controls degradation of proteins?
Cyclin destruction boxes, PEST sequences.
112
What are the components of the 26S proteasome?
19S - recognition, 20S - protease.
113
What is the major site for amino group removal?
Liver.
114
What degrades the branched amino acid sequence?
Muscle.
115
What happens to the removed amino group?
Urea.
116
What happens to the remaining carbon skeleton?
TCA cycle.
117
What do aminotransferases/ transaminases do?
Transfer alpha amino group to alpha ketogluterate - producing glutamate.
118
What are two important example of transaminases?
Aspartate transaminases (oxaloacetate + glutamate) and alanine transaminase (pyruvate + glutamate).
119
What do all transaminases require?
Pyridoxal phosphate (prosthetic).
120
Describe pyridoxal phosphate.
Produced from B6 (pyridoxine), reversible (amino acid synthesis).
121
What is glutamate dehydrogenase used for?
Oxidative deamination (can use NAD+ or NADP+ in some species).
122
What is the eqm in the liver?
Close to 1.
123
What is glutamate dehydrogenase specific to?
Liver mitochondria - compartmentalisation (sequesters NH4+).
124
What organisms do and don’t produce urea?
Ureotelic organisms do, ammoniotelic organisms dont.
125
How many ATP are required for each Urea?
4x
126
What is involved in Carbomoyl phosphate synthestase?
Joins NH3 to HCO3-, three steps, 2xATP, irreversible in vivo.
127
What is Ornithine Transcarbomoylase?
Anhydride bond in carbamoyl phosphate - high transfer potential, citruline transported out of Mt.
128
What is Argininosuccinate Synthetase?
Condensation, citruline, aspartate, ATP - AMP, breakdown of PPi.
129
What does Argininosuccinase do?
Fumerate produced, nitrogen remain bound to arginine.
130
What does Arginase do?
Urea produced via hydrolysis, ornithine regenerated, transported to mt, recombined with carbamoyl phosphate.
131
What process turns fumerate into malate?
Hydration.
132
What process turns malate into oxaloacetate?
Oxidation.
133
What process turns Oxaloacetate into glucose?
Gluconeogenesis.
134
What produces aspartate from fumerate?
Aspartate aminotransferase.
135
What is needed for nitrogen fixation?
8 high energy electrons, 16 ATP, nitrogenase complex (reductase + nitrogenase).
136
What is involved in assimilation of NH4+?
Glutamate dehydrogenase, some use NADH or NADPH, formation of Schiff base, stereochemistry of L-glutamate.
137
What is required for glutamine synthesis?
ATP, cumulative regulation.
138
What is glutamine synthetase a key step in?
Bacterial metabolism.
139
What defines a high quality protein?
Contains all essential amino acids, in proportions required, easily digestible form.
140
Where is the equilibrium shifted towards in the reversible reaction when producing UDP-glucose?
Towards UDP-glucose formation by hydrolysis of the pyrophosphate.
141
What happens to form an alpha-1,4 glycosidic bond during glycogenesis?
Glycosyl units added to the non-reducing end of glycogen molecule.
142
What enzyme catalyses the reaction to form an alpha-1,4 glycosidic bond?
Glycogen synthase.
143
Why is a primer required in the addition of glycosyl units in glycogenesis?
The enzyme can only add glycosyl units if polysaccharide chain is greater than 4 residues.
144
What is primer function carried out by?
Glycogenin.
145
What is glycogen synthase?
Regulatory enzyme of glycogen synthesis.
146
What is glycogen synthase regulated by?
Covalent modifications i.e. phosphorylated by the enzyme protein kinase A.
147
148
What does phosphorylation do for glycogen synthase?
Converts the active a form of the enzyme into a usually inactive b form.
149
What happens when insulin counteracts the phosphorylation of glycogen synthase?
Signals the body to synthesise glycogen (activates phosphatase enzyme).
150
What can happen to Glucose 6-P at high levels?
Can allosterically activate of the b form.
151
What catalyses the formation of alpha-1,6 glycosidic bonds?
Branching enzyme.
152
What do branching enzymes do?
Removes 7 glucose until from end of chain which is at least 11 residues long then re-attaches at more interior site, must be at least 4 residues away from a branch point.
153
What is glycogen synthesis called?
Glycogenolysis.
154
What does glycogen breakdown provide?
Glucose 6-P for further metabolism.
155
Summarise first steps of glycogenolysis.
Glycogen phosphorylase cleaves alpha-1,4 glycosidic bonds by addition of orthophosphate, releases glucose 1-P, fully reversible under conditions.
156
What can alpha-1,6 linkages not be cleaved by?
Glycogen phosphorylase.
157
What debranching enzyme is used in eukaryotes for glycogenolysis?
Single enzyme with two activities, transferase and alpha-1,6-glucosidase activity.
158
What does activity of debranching enzyme do?
Paves the way for further cleavage by glycogen phosphorylase.
159
What happens to glucose 1-P in glycogenolysis?
Converted to glucose 6-P by phosphoglucomutase.
160
Why can’t glucose 6-P escape the cell?
Is negatively charged.
161
Why does the liver have a glucose 6-P enzyme located in ER?
Its role in blood glucose homeostasis.
162
What does the glucose 6-P do in the liver?
Hydrolytically cleaves glucose 6-P to glucose which can enter blood.
163
What signals the energy state of the cell?
Dimeric protein regulated by several allosteric effectors.
164
What is glycogen phosphorylase?
Dimeric protein, reversible covalent modification, responsive to hormones such as insulin adrenaline and glucagon, regulation differs.
165
In what way does glycogen phosphorylase differ?
Depending on tissues function, muscle uses glucose itself as source of energy, liver maintains glucose homeostatic of whole organisms.
166
In what way are glycogenesis and glycogenolysis are reciprocally regulated?
Synthesis and breakdown are regulated by hormone triggered cAMP cascade acting through protein kinase A.
167
What is the role of protein phosphatase 1?
Activated by signal cascade brought about by high insulin levels, reverses effect of protein kinase A, inactivates phosphorylase kinase and phosphorylase a by removing covalent P group, activates glycogen synthase by removing covalent P group.
168
What are glycogen storage diseases?
Inherited genetic defects which mean enzymes needed to degrade stored glycogen aren’t working properly.
169
What is Von Gierke’s disease?
Most common form (type 1), autosomal recessive, 1 person in 200000, glucose-6-P missing.
170
What does Von Gierke’s disease caused?
Hypoglycemia due to lack of liver gluconeogenesis and glycogenolysis, need regular supply of glucose even when asleep.
171
What is Cori’s disease?
Type 3, deficiency of glycogen debranching enzyme, glycogen accumulates with short side branches as these cant be utilised, much less severe symptoms than von Gierke’s.
172
What is McArlde’s disease?
Type 5, muscle phosphorylase missing, muscle cramps, no increase in lactate in muscle upon exercise.
173
What is gluconeogenesis?
Glucose formation from non-carbohydrate precursors.
174
What does synthesis of carbohydrate containing biological molecules rely on?
A source of activated monosaccharides
175
What can activated molecules be derived from?
Non carbohydrate precursors like seedlings, bacteria, starving mammals.
176
Characteristics of glucose?
Primary fuel for brain, only fuel for RBCs, daily requirement 160g.
177
What readily available glucose per day do humans have?
20g body fluids, 190g glycogen.
178
What are major sites of gluconeogenesis?
Liver but kidneys during extreme starvation.
179
What does gluconeogensis do?
Convert pyruvate into glucose.
180
What are major precursors for gluconeogenesis?
Lactate, amino acids, glycerol.
181
When is lactate a precursor?
Skeletal muscle when glycolysis exceeds oxidative metabolism - RBC.
182
When are amino acids precursors?
Diet or during starvation - not leucine or lysine.
183
When is glycerol a precursor?
Hydrolysis of TAG yields glycerol and fatty acids.
184
Why is gluconeogensis not the reverse of glycolysis?
Glucose — pyruvate releases 2ATP and 2NADH whereas pyruvate — glucose uses 6ATP and 2NADH.
185
Where does the eqm of glycolysis lie?
In direction of pyruvate production.
186
What reactions must be bypassed during Gluconeogenesis?
HexoKinase, PFK, Pyruvate kinase.
187
What is step 1 of bypass 1, pyruvate to PEP (gluconeogensis)?
Carboxylation of pyruvate to oxaloacetate by pyruvate carboxylase (anaplerotic reaction).
188
What is step 2 of bypass 1, pyruvate to PEP (gluconeogensis)?
Decarboxylation and phosphorylation of oxaloacetate by phosphoenolpyruvate carboxykinase.
189
What are some characteristics of step 2 of bypass 1?
GTP required, enzyme in cytosol and mitochondria, mitochondrial enzyme used if lactate is precursor, cytosol is if pyruvate is.
190
What is the NADH generated in the cytosol used for?
Conversion of 1,3 bisPglycerate to glyceraldehyde 3 phosphate by enzyme Glyceraldehyde 3-P dehydrogenase.
191
What is the oxaloacetate shuttle?
When cytosolic enzyme used, oxaloacetate cannot directly diffuse out, converted to malate which leaves via transporter, converted back with concomitant production of NADH.
192
Summarise bypass 2 in gluconeogenesis - fructose 1,6-bison to fructose 6-P.
PEP metabolised until fructose 1,6-bisP formed, reactions near eqm, PFK catalyses irreversible step.
193
What enzyme is responsible for bypass 2?
Fructose 1,6-bisP- allosteric enzyme catalyses hydrolysis of C1 phosphate group.
194
What tissues need to convert glucose 6-P to glucose at the end of gluconeogenesis?
Tissues responsible for maintaining blood glucose homeostasis - muscles cannot directly increase glucose, takes place in ER.
195
What is the Cori cycle?
Lactate formed by active muscle is converted to glucose by liver.
196
What kind of organisms are vertebrates mainly?
Aerobic.
197
What happens during extreme muscular activity?
Oxygen delivery to muscle is lower than oxygen requirements for oxidation of NADH.
198
How is NADH oxidised?
By transfer of electrons to pyruvate to form lactate.
199
What does lactate acid dissociate into?
Lactate and H+.
200
What happens during lactic acid production during anaerobic activity?
pH decreases, muscle pain and failure to contract, activity decreases, oxygen debt reduced in 30 mins by conversion of lactic acid to glucose by gluconeogenesis.
201
Difference between vertebrate size and anaerobic metabolism?
Smaller vertebrate rely on anaerobic metabolism, larger vertebrates often slow moving and rarely undertake intense muscular activity.
202
Summarise the Cori cycle.
Lactate produce by active muscle and RBC, lactate dead end product, well oxygenated cells convert to pyruvate, enters TCA cycle, XS lactate enters liver, converted to glucose, maintains blood glucose.
203
What is the glyoxylate cycle?
Pathway by which plants and microorganisms can convert fatty acids into glucose, acetylene coA generated by beta-oxidation is converted to glucose via glyoxylate cycle and gluconeogenesis.
204
Steps of Glyoxylate cycle?
Decarboxylation reactions of TCA cycle bypassed so carbon of acetyl coA assimilated, isocitrate cleaved to glyoxylate and succinate, glyoxylate condenses with another acetly coA to generate malate which is oxidised to generate OA for another round.
205
How is TAG used for energy?
Mobilisation of TAG from adipose, glucagon, epinephrine, cortisol, HSL — 3x FFA, 1x glycerol.
206
What is fatty acids activation linked to?
CoA prior to oxidation in cytoplasm, coupled to ATP — AMP.
207
How does fatty acid activation occur?
Made irreversible in vivo by rapid hydrolysis of pyrophosphate, thioester bond formed, increased by [S].
208
What processes mirror each other in fatty acid metabolism?
Oxidation and synthesis - reaction type/ order, different pathways, enzymes, compartmentalisation.
209
What are four key enzymes?
Acyl CoA dehydrogenase, enoyl CoA hydratase, L-3-hydroxyacyl CoA dehydrogenase, beta-ketothiolase.
210
How many additional reactions are required for unsaturated fatty acids?
2
211
What can animals not do?
Produce glucose from FFA - link reaction is irreversible.
212
What can Ketones be used for?
As fuel in preference to glucose, during fasting other tissues utilise, BBB, prolonged starvation (75%).
213
Overview of beta-hydroxybutyrate dehydrogenase?
Reduction of acetoacetate, ratio acetate:butyrate, dependent upon NADH+H+ and NAD+ in mitochondria, not spontaneous.
214
Where does fatty acid synthesis take place?
Cytoplasm.
215
What does carnitine do only?
Transport long chain fatty acids.
216
What does transport of acetly CoA from mitochondria require?
Another shuttle, uses ATP and NADH, produced NADPH.
217
What are the first few steps of fatty acid synthesis?
Acetyl CoA carboxylated to form malonyl CoA, committed step, coupled to ATP — ADP.
218
Characteristics of fatty acid synthase?
Complex of several enzymes, long chain, involves carrier protein.
219
Characteristics of acyl carrier proteins?
Intermediates linked to ACP, covalent, structural similarities with CoA.
220
What is the acyl-malonyl ACP condensing enzyme?
Condensation reaction, increases chain length, malonyl (3C) - ACP, powered by decarboxyaltion of malonyl ACP.
221
What is beta-ketoacyl ACP reductase?
Reduction, reducing agent NADPH, D isomer formed, NADH generated in energy yielding reactions, NADPH used in biosynthesis.
222
What is 3-hydroxyacyl ACP dehydratase?
Dehydration reaction, substrate preparation, aiming for saturated FA.
223
What is enoyl ACP reductase?
Reduction, NAPH agent, inhibited by triclosan, next round butyryl ACP condenses, stops at 16C Palmitate.
224
What are fatty acids from adipose bound to to be transported to tissues?
Serum Albumin.
225
What are triglycerides transported as?
Chylomicrons, VLDL, LDL, HDL.
226
Is the Link reaction reversible or irreversible?
Irreversible.
227
What enzyme is used in the link reaction?
Pyruvate dehydrogenase - a large complex.
228
Characteristics of pyruvate dehydrogenase?
Mass 4 mil to 10 mil daltons, groups travel from one subunit to another connected to core by tethers.
229
What are two catalytic cofactors?
Thiamine pyrophosphate (TPP) and lipoic acid.
230
What are two stoichiometric cofactors?
CoA and NAD+.
231
What is the first step of the Link reaction?
Decarboxylation.
232
What happens during Decarboxylation?
Pyruvate combines with TPP before Decarboxylation, TPP is the prosthetic group of the enzyme.
233
What is the second step of the link reaction?
Oxidation.
234
What happens during oxidation?
Hydroxethyl group is oxidised and transferred to lipoamide, forms energy rich thioester bond.
235
What is the third step of the Link reaction?
Group transfer - acetylation.
236
What happens during acetylation?
Acetyl group transferred, Acetyl CoA, fuel for TCA.
237
What is the enzyme used in steps 1 and 2 of the link reaction?
Pyruvate Dehydrogenase Component (E1).
238
What is the enzyme used for steps 3 of the link reaction?
Dihydrolipoyl Transacetylase (E2).
239
What is step four of the link reaction?
Oxidation of dihydrolipoamide back to lipoamide.
240
What happens during step four of link reaction?
Oxidation of dihydrolipoamide to lipoamide, must occur before further acetylCoA to pyruvate happens, e- to FAD then NAD+.
241
What enzyme is used in steps four of the link reaction?
Dihydrolipoyl dehydrogenase (E3).
242
What is the regulatory point of the link reaction?
Committed irreversible step - ATP/lipid/aa/formation.
243
Characteristics of the regulatory point of the link reaction?
Pyruvate dehydrogenase, selected mechanisms, adenylate control.
244
What happens during the regulatory point of the link reaction?
Upregulated ADP, pyruvate, PDP, deregulated ATP, PDK, deregulated NADH, Acetyl CoA, Upregulated Ca2+.
245
What is Mercury poisoning?
Binds to E3, inhibits, hatters used mercury nitrite, sulfhydryl treatment.
246
What is Beriberi poisoning (alcoholics)?
B1 deficiency, neuro and cardio symptoms, raised pyruvate in blood, need glucose for energy (nervous system).
247
What is the citric acid cycle?
Final common pathway for fuel oxidation - carbs, fats, aas.
248
Where and as what do most molecules enter the citric acid cycle?
At Acetyl CoA, as componentes of TCA.
249
What is the first step of the citric acid cycle?
Aldol condensation followed by hydrolysis.
250
What is the enzyme used for aldol condensation followed by hydrolysis in citric acid cycle?
Citrate synthase.
251
What happens during the first step of the citric acid cycle?
4C + 2C = 6C, entry point for Acetyl CoA.
252
What is the second step for the citric acid cycle?
Isomerisation (dehydration-hydration).
253
What enzyme is used in the second step of the citric acid cycle?
Aconitase.
254
What happens during the second step of the citric acid cycle?
Rearranges hydroxyl, necessary for oxidation step, aconitate intermediate.
255
What is the third step of the citric acid cycle and what enzyme is used?
Oxidation - reduction and Decarboxylation, isocitrate dehydrogenase.
256
What happens during the third step of the citric cycle?
NAD+ — NADH + H+, CO2, oxalosuccinate intermediate.
257
What is the regulatory point 1 of citric acid cycle?
First enzyme to generate high energy e-.
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What can isocitrate dehydrogenase do?
Upregulated ADP (allosteric), deregulated ATP (allosteric), deregulated NADH (competitive product).
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What may XS citrate do?
Inhibit PFK.
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What is step four of the citric acid cycle and what enzyme is used?
Decarboxylation, oxidation, group transfer, alpha-ketogluterate dehydrogenase used.
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Characteristics of step four of citric acid cycle?
An enzyme complex, homologous to pyruvate dehydrogenase.
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What is the regulatory point 2 of the citric acid cycle?
2nd enzyme to generate high energy e-.
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What does the enzyme do in regulatory point 2?
Deregulated Succiyl CoA (competitive product), NADH (competitive product) and ATP.
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What can XS substrate be used for?
To make AAs.
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What does succinyl CoA have?
A high energy thioester bond.
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What is step five of the citric cycle?
Conversion to succinate coupled GTP forming, nucleoside diphosphokinase, GTP + ADP — GPD + ATP, group transfer.
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What are the next three steps of citric cycle after step five?
Oxidation hydration oxidation, reforms oxaloacetate, common series of reactions.
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What is the hydrogen acceptor in citric acid cycle?
FAD, FAD — FADH2, does not dissociate, passed directly to coenzyme, direct link with ETC.
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What does fumerase do?
Additional of H+ and OH-, removal of double bond.
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What does malate dehydrogenase do?
Positive deltaG, driven by product use in ETC and TCA cycle.
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How many membranes do mitochondria have and what is the name for this?
2 membranes - endosymbiosis.
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What is the outer membrane of the mitochondria?
Permeable - mitochondrial porin.
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What is the inner mitochondrial membrane?
Impermeable to polar molecules, integrity requires for oxidative ATP production, 14000m2 per person, highly folded, transport.
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What is the name for the highly folded regions of mitochondria?
Cristae.
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How does NADH movement work?
Glycerol 3-phosphate shuttle, predominates in muscle, FADH2, less ATP.
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What are the two mechanisms for NADH movement?
Malate and aspartate shuttle.
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How does the ATP-ADP translocase work?
ATP more -ve than ADP, saps electrical gradient produced by ETC, ~25%.
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What does OILRIG explain and stand for?
Redox reactions, oxidation is loss, reduction is gain (of e-).
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What is the standard reduction potential (E^o)?
A measure of a compounds affinity for e-, oxidising potential, potential to become reduced.
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What E^o oxidise less positive E^o?
More positive.
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What do less +ve E^o do to more +ve E^o?
Reduce.
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How is deltaE^o calculated?
E^o (acceptor) - E^o (donor) in volts.
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What does more +ve deltaE^o mean?
Easier reaction.
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How can the reduction potential be related to Gibbs free energy by?
deltaG^o = -nFdeltaE^o (n = electrons transferred, F = faraday constant 96.5kj/volt).
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What are the proteins in the ETC like?
Four potatoes and a mushroom - three proton pumps and one link with citric cycle.
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What does protein complex 1 do in oxphos?
NADH-co Q oxidoreductase, NADH dehydrogenase, e- from NADH to CoQ, two bound cofactors.
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What are the two bound cofactors used for complex 1 in oxphos?
1x Flavin mononucleotide similar to FAD but only 1 e- at time, 6-7 iron-sulfur centres.
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What is the Coq/ ubiquinone?
Lipid based, moves freely within mitochondrial inner membrane, electron carrier.
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What is the complex 3 in oxphos?
CoQ-Cytochrome c oxidoreductase, passes e- from CoQ to Cytc, via FE-S then either 2x Cytb or CytC1, contains 2x b type, 1x c, 1x Fe-S.
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What is Cytochrome c?
Mobile Cytochrome, loosely bound to inner membrane, water soluble, contains heam proteins, complexed metal ion is Fe, carries e- to complex 4.
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What is complex 4 in oxphos?
CytoC oxidase, cytochrome an and a3 contain Cu, e- from/to CytC, CUa, Cyta, CUB, Cyt a3, haeme HCN, oxygen.
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What is complex 2 in oxphos?
Succinate-CoQ oxidoreductase, contains succinate dehydrogenase, FAD, 3x iron sulfur, 1x Cytochrome, mutation causes disorders.
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What is the efficiency of oxphos?
~40%, ~220kj/mole from NADH oxidation, ATP produced, ~deltaG^o +30.5, ~2.5 ATP per NADH.
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What is a ROS?
Reactive oxygen species.
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What does ROS do?
Partial reduction of O2 — H2O, harmful reactive chemicals, potentially destructive.
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What can be used as defence against ROS?
Superoxide dismutase and catalase.
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What can inhibit NADH-CoQ oxidoreductase?
Rotenone (insecticide) and Amytal (amobarbital).
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What inhibits cytochrome c oxidase?
Cyanide, azide, carbon monoxide.
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What is produced from oxidative phosphorylation?
A proton gradient is generated across the inner mitochondrial membrane.
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What has been found from OxPhos?
Drives ATP synthesis, chemiosmotic theory, proton motive force.
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How is OxPhos controlled?
Determined by ATP demand, ETC and ATP synthase coupled, controlled by ADP, regulatory effects.
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In what way is ETC coupled to ATP production in OxPhos?
Mitochondria coupled, no e- flow without phosphorylation, no phos without e- flow, no ADP or O2, no ATP made.
