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BMS1011 > C and D lectures- Metabolism > Flashcards

C and D lectures- Metabolism Flashcards

1
Q

Where is FADH2 dervied from?

A

Raboflavin (vit B2)

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2
Q

What is Gibbs free energy and what does positive and negative delta G mean?

A

The potential energy of the system- amount of energy capable of doing work during reaction. + delta G- non spontaneous (endergonic), - delta G, spontaneous- exergonic.

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3
Q

What is delta G 0

A

Standard free energy change for reaction occuring under standard conditions

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4
Q

What is delta G 0’

A

Transformed standard free energy change at pH=7 and 55.5 M H20

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5
Q

When K’ equilibrium is above 1 and delta g is negative, what happens to the reaction?

A

It proceeds forward (favouringproducts)

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6
Q

When K0 is 1 and delta g is zero, what happens to reaction at 1M?

A

It is at equilibrium

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7
Q

When K’ equilibrium is less than 1 and delta g is positive what happens to reaction?

A

Proceeds in reverse (left,favours reactants)

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8
Q

What does the principle of bioenergetics expalin?

A

How a thermodynamically unfavourable (endergonic reaction can be driven in forward direction by coupling it to a highly exergonic reaction

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9
Q

Which two reactions in the first step of glycolysis are coupled to give an overall exergoinic reaction?

A
  1. Glucose–> glucose-6-phosphate
  2. ATP–> ADP
    ATP + Glucose–> ADP + Glucose-6-phosphate

13.8 +(-30.5)= -16.7 Kj/mol (so overall exergonic)

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10
Q

What is the main molecule that couples with the metabolite needing activation and why does this occur?

A

ATP ; because the ATP contains high energy phosphate bonds -1 is cleaved which releases a lot of energy to drive the reaction

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11
Q

What types of reactions are spontaneous?

A

Hydrolysis reactions and complete oxidation of reduced compounds (how chemotrophs obtain enrergy)

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12
Q

Does oxidation of glucose or palmitate (fat) produce more energy?

A

Palmitate (fat) 9 770 compared to glucose 2 840

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13
Q

Why does ATP have a high -ve delta G?

A

It has 4 closely spaced negative charges at pH=7,

H+ is a product of ATP hydrolysis which will shift equilibrium to the right, ADP and Pi are stabilised by resonance.

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14
Q

What is metabolism?

A

Sum of chemical reactions that allow us to maintain life (energy extraction,maintenance)

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15
Q

What enzymes help convert starch into glucose?

A

Pancreatic amylase and salivary amylase

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16
Q

What two subunits are produced from starch?

A

maltose and limit dextrins

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17
Q

Which enzyme converts limit dextrins to glucose?

A

Dextrinase

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18
Q

Which enzyme converts maltose into 2 glucose subunits?

A

Maltase

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19
Q

What is glucoamylase?

A

Takes any polysaccharide and turns it into glucose

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20
Q

What are examples of brushborder enzymes?

A

Maltase, sucrase, lactase, dextrinase, glucoamylase

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21
Q

What transport does glucose undergo into the epithelial cell from the lumen?

A

Sodium-glucose co transport (secondary active transport)

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22
Q

What type of transport does glucose undergo from epithelial cell to outside?

A

Facilitated diffusion

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23
Q

Is galactose absorption the same as glucose?

A

YES! It just is galactose molecule instead of glucose

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24
Q

How is fructose absorbed?

A

It undergoes facilitated fiddusion both atthe apical and basolateral membranes

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25
What does glycogen exist as?
An amylopectin
26
Which organ produces the enzyme necessary to digest most of the carbohydrates we injest and what is it?
Te pancreas and it is pancreatic amylase
27
Which carbon bond does alpha amylase digest?
Alpha 1-4
28
What is the key enzyme in the digestion of polysacharides?
Alpha amylase
29
What is the most common digestible homopolysaccharide existing as both amylose and amylopectin?
Starch
30
Which homopolysaccaride contributes the most to our energy?
Amylopectin (80%)
31
How much energy does glucose yield?
-2840 kJ/mol
32
Where does glycolysis occur and does it require oxygen?
In the cytosol; no it doesnt require oxygen
33
What allows NADH to be converted into ATP?
The reducing potential
34
What must happen for glycolysis to continue?
The 2 NADH must be reoxidised to NAD+ to allow for the next cycle of glycolysis.
35
In glycolysis as a whole, how many ATP are used and how many produced, thus how many are made?
2ATP used and 4 ATP made to bring net total of ATP to 2 ATP for glycolysis.
36
Which reactions in glycolysis are exergonic?
1 (glucose --> glucose-6-phosphate 3. Fructose-6-phosphate--> fructose1,6 bisphosphate 10. PEP---> pyruvate
37
What is the difference between starch and glycogen?
Glycogen is more branched
38
What can glycogen be made from?
Excess blood glucose or recycling of glucogenic metabolites (lactate or amino acids)
39
What is the difference between digestion (hydrolysis) and mobilisation?
Digestion is HYDORLYSIS of polysaccharides (sugars efficiently absorbed across cell membranes - Mobilisation is the phosphorolysis (sugar phosphates will not cross the membrane due to CHARGE but once removed from molecule it can cross membrane)
40
What is good about mobilisation with ATP?
Having the phosphate group saves the investment of additional ATP
41
What is a reducing end in glycogen?
Usually on left side of molecule where all glucose additions or removals occur
42
In glycogenolysis (mobilisation of glycogen) what does glycogen phosphorylase do and when does it stop activity?
Breaks down alpha 1-4 glycosidic bond (straight chain) from NON reducing end (left) until it is 4 residues before an alpha 1-6 bone (branching point)
43
What does the enzyme glycogen debranching enzyme do (which two functions does it have)?
Gets rid of the branches. 1. TRANSFERS 3 glucose residues (from branching chain) to the non reducing end of glycogen (straight chain part) 2. alpha 1-6 glycosidase activity; hydrolyses a single glucose residue (left over from branching part) to release a single glucose molecule. Glycogen phosphorylase then continues to break down the straight part of the chain again unitl coming u to another branching point.
44
What does the enzyme phosphogutomutase do?
Converts G-1-P to G-6-P
45
What are the fates of G-6-P?
In the muscles it can enter glycolysis straight away for aiding in muscle contraction In the liver and kidneys glucose-6-phosphatase converts glucose-6-phosphate into glucose when blood glucose levels drop to release it into the bloodstream
46
Where is glucose 6-phosphatase present in the liver and kidney cells?
In the lumen of the E.R
47
What is the G-6-P transporter?
T1
48
What is the glucose transporter out of the ER lumen?
T2
49
What is the glucose transporter out of the cell?
T3
50
What occurs in von Gierkes disease?
Enzyme glucose-6-phosphatASE is faulty (so hypoglycemia-low blood sugar is likely to result) Pyruvate is still formed from glycolysis but glucose-6-phosphate cant be transported out of cell (cant be converted to glucose in ER)
51
Is a lot of energy from glucose captured in glycolysis?
NO only a small amount (glycolysis: -146 kg/mol) | (full oxidation: -2840kj/mol) -due to energy being in carriers NADH
52
What can pyruvate go on to form?
In anaerobic conditions; either ethanol in yeast or lactate contracting muscle, RBCs, or in normal glycolysis of course!
53
In which two processes is energy extracted from the pyruvate?
CA cycle and oxidative phosphorlyation
54
How is pyruvate converted into acetyl CoA and WHERE ?
Via pyruvate dehydrogenase complex and 5 coenymes TPP, lipollysine, FAD NAD+ and CoS-SH (exergonic reaction) ; MITOCHONDRIA
55
What happens if you dont have thiamine? (TPP)
Pyruvate dehydrogenase complex blocked
56
Where does lactic acid fermentation occur?
Active skeletal muscles, erythrocytes, microorganisms (lactobacillus- yogurt and cheese)- all via different forms of the LDH (lactate dehydrogenase complex)
57
What does pyruvate require to be converted into lactate?
NADH
58
What is a toxic intermediate produced by pyruvate to ehtanol?
Acetaldehyde
59
What type of reaction is pyruvate to Acetyl CoA?
Oxidative decarboxylation
60
Where are glycogen levels highest in?
Muscle
61
Activation of a fatty acid...
utilises one molecule of ATP which is hydrolysed first to produces AMP and PPi with the further hydrolysis of PPi to drive the reaction to completion
62
Conversion of pyruvate to Acetyl CoA requires?
Lipoic acid
63
What are the three lipases?
Gastric lipase, lingual lipase, and pancreatic lipase (most important one)
64
Where does most of lipid digestion occur?
The duodenum
65
What does it mean when I say bile salts are amphipathic?
They have a dipole and thehydrophobic part interacts with the triacylglycerols.
66
Where are bile salts formed?
In the liver from chlseterol and then get secreted in duodenum -can later be reccled via hepatic portal vein back to liver for use again
67
What are the 6 steps of storage of dietary fatty acids?
1. Lipase dissassembles triglyceride (2FAs and 1MG) 2. Diffuses into epithelial cell and smooth ER reassembles them into Triacylglycerides 3. Enters the golgi apparatus to be packaged and sent out as CHYLOMICRON 4. AS CHYLOMICRON undergoes exocytosis 5. too large to enter blood, so enters lymphatics 6. Then enters blood and stored in adipose tissue
68
Why are fats better than polysaccharides?
Carry more energy per carbon (due to being more reduced), non polar, good storage, slow delivery
69
How are dietary fats transported in blood?
Via the chylomicron structure
70
What is the fate of glycerol after it has been broken off fatty acids in mobilisastion?
It phosphorylated and isomerised to form G-3-P (enters pay off phase) - represents 5% of overall energy of TGAs
71
Where does beta oxidation need to occur?
In the matrix of mitochondria
72
How many Acetyl CoA molecules and NaDH/FADH molecules will be formed from the beta oxidation of 18 carbon saturated fatty acid?
9 acetyl CoA, 8 NADH and FADH
73
How many acetyl CoA produced from oxidation of 18 carbon MONOunsaturated?
6 acetyl CoA
74
What does enoyl Co-A isomerase do with monounsaturated fatty acids?
It converts the trans bond to cis
75
What are the three types of ketone bodies?
Acetone, Acetoacetate, d-beta-hydroxybutyrate
76
What happens when oxaloacetate concentration is low?
Acetyl CoA channelled towards ketone body production rather than CAC
77
When are ketone bodies overproduced?
During starvation and diabetes
78
What occurs in the CA cycle?
Acetyl CoA is broken up into two molecules of CO2 and 3NADH, 1FADH and 1GTP
79
Is Co enzymeA used up?
NO it is not it is a cofactor for acetyl coA and associates then dissociates without being used up- accepts and carries acyl groups into the CAC
80
What is the advantage of a thioester bond?
High standard free energy of hydrolysis. -acyl group is linked to thiol group via thioester bond
81
Is the CAC both oxidative and reductive?
YES because of gluconeogenesis can also syntheise molecules
82
What does the CA produce a lot of?
NADH compared to other pathways (causes oxidation of Acetyl-CoA
83
Where does the CAC occur in eukarotes and prokaryotes respectively and which energy do they use?
matrix of mitochondira NAD+; cytosol NADP+
84
Which step of CAC is regulated by ATP an irreversible?
Isocitrate to alphaketoglutarate (decarboxylation)
85
What drives the malate reaction forward despite it having high positvie dleta G?
The very low concnetration of oxaloacetate
86
How come the oxaloacetate concentration is very low?
because of the exergoinc citrate synthase (very engative delta G)
87
Are the two carbons oxidised by the CAC the same as acetyl CoA?
They are EQUIVALENT to two AcetylCoA carbons but not necessarily from the same place .
88
Is the CAC overall exergonic or endergonic?
It is exergonic; -50.3kJ/mol
89
what allows for an endergonic reaction to take place?
Coupling it with exergonic reaction.

BMS1011 (5 decks)

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