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PoM > Cell metabolism I > Flashcards

Cell metabolism I Flashcards

1
Q

What 6 types of metabolic reactions are present?

A

Redox
Group transfer
Isomerisation
Hydrolytic
Ligation requiring ATP cleavage
Addition/removal of functional groups

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2
Q

What are oxidation-reduction reactions?

A

Transfer of electrons between molecules

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3
Q

What are ligation reactions?

A

Formation of covalent bonds

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4
Q

What are isomerisation reactions?

A

Rearrangement of atoms to form isomers

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5
Q

What are group transfer reactions?

A

Transfer of a functional group from one molecule to another

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6
Q

What are hydrolytic reactions?

A

Cleavage of bond via addition of water

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7
Q

What are the reduction reactions?

A

Addition of hydrogen
Addition of electrons
Removal of oxygen

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8
Q

What are oxidation reactions?

A

Addition of oxygen
Removal of hydrogen
Removal of electrons

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9
Q

What is NAD?

A

Nicotinamide adenine dinucleotide
Coenzyme hydrogen acceptor

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10
Q

What is FAD?

A

Flavin adenine dinucleotide

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11
Q

What is the first step of glycolysis?

A

Glucose is phosphorylated by ATP to glucose-6-phosphate via hexokinase-4
Proton released
Group transfer

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12
Q

Why is glucose phosphorylated?

A

Addition of high-energy phosphate makes glucose more reactive
Unable to bind to glucose transporter
Negatively charged
Trapped within cell (irreversible/ committed to glycolysis)

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13
Q

What is the second step of glycolysis?

A

Glucose-6-phosphate is converted into fructose-6-phosphate via phosphoglucoisomerase
Isomerisation

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14
Q

What is the third step of glycolysis?

A

Fructose-6-phosphate is phosphorylated into fructose-1,6-bisphosphate via phosphofructokinase
Group transfer

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15
Q

What is the fourth step of glycolysis?

A

Fructose-1,6-bisphosphate is hydrolysed into glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP) via aldose
Hydrolytic cleavage

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16
Q

What is the fifth step of glycolysis?

A

DHAP is converted into G3P via triosephosphate isomerase (TPI)
Isomerisation

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17
Q

What is the glycolytic enzymopathy that is fatal?

A

TPI deficiency

18
Q

What is the sixth step of glycolysis?

A

G3P is converted into 1,3-bisphosphoglycerate via glyeraldehyde-3-phosphate dehydrogenase
NADH is generated from NAD+
Redox and group transfer

19
Q

What is the seventh step of glycolysis?

A

1,3-bisphosphoglycerate is converted into 3-phosphoglycerate via phosphoglyceratekinase
ATP produced from ADP and Pi
Group transfer

20
Q

What is the eighth step of glycolysis?

A

3-phosphoglycerate is converted to 2-phosphoglycerate via phosphoglycerate mutase
Isomerisation

21
Q

What is the ninth step of glycolysis?

A

2-phosohoglycerate is converted into phosphoenolpyruvate via enolase
Dehydration

22
Q

What is the last step of glycolysis?

A

Phosphoenolpyruvate is converted into pyruvate via pyruvate kinase
ATP is produced
Group transfer

23
Q

Where does glycolysis occur?

A

In the cellular cytoplasm

24
Q

What is glycolysis?

A

Substrate level phosphorylation of respiratory substrate glucose to synthesize pyruvate, ATP, and reduced NAD to generate ATP

25
Q

How many gross ATP molecules are made?

A

Four
2 via 1,3bisphosphoglycerate –> 3-bisphosphoglycerate
2 via phosphoenolpyruvate –> pyruvate

26
Q

What is the destination of the 2 NADH molecules under aerobic conditions?

A

They pass through the outer mitochondrial membrane into the electron transport chain

27
Q

What are the three fates of the 2 molecules of pyruvate made?

A

Acetyl CoA formation
Alcohol fermentation (plants, microorganisms)
Lactate production (anaerobic conditions only)

28
Q

What property of acetyl CoA makes it useful to respiration?

A

It has a high-energy thioester bond that is readily hydrolysed
It is picks up and donates the acetate group to the TCA cycle

29
Q

How is acetyl CoA formed from pyruvate?

A

Actively transported to mitochondrial matrix
Link reaction
Pyruvate is decarboxylated and dehydrogenated to form acetate via pyruvate dehydrogenase complex (PDH)
Coupled with CoA to form acetyl CoA (and CO2)

30
Q

How is Beri Beri caused and what are the symptoms?

A

Thiamine deficiency (vitamin B1 derivative)
Thiamine pyrophosphate is a co-factor of the PDH complex
It is easily deprotonated and the resulting carbanion attacks pyruvate so that acetyl CoA can’t form
Results in damage to PNS, muscle weakness, decreased cardiac output
Brain is vulnerable as it is heavily reliant on glucose metabolism

31
Q

How is lactate formed from pyruvate?

A

Pyruvate is reduced to lactate via lactate dehydrogenase
NADH is re-oxidised to NAD+ to allow glycolysis to continue
Occurs in mammalian muscle when oxygen is unavailable to be the final hydrogen accept during oxidative phosphorylation

32
Q

What happens to the lactate that is formed?

A

Transported back to the liver and converted into pyruvate via LDH

33
Q

Where is LDH predominantly located?

A

Liver, kidneys, skeletal muscle, heart, blood and lungs

34
Q

What is the neural response to lactate production?

A

Release of hydrogen ions enter into the blood (from acid) subsequently dropping blood pH
Detected by chemoreceptors within the carotid sinus and aortic arch
Triggers CNS to reduce muscle contraction, muscle have time to recover and return to aerobic respiration.

35
Q

How is alcohol formed from pyruvate?

A

Pyruvate is decarboxylated to ethanal (acetaldehyde) via pyruvate decarboxylase
Ethanal is then reduced to ethanol via ethanal dehydrogenase
NAD+ is regenerated
Occurs under anaerobic conditions

36
Q

Why is the regeneration of NAD+ important?

A

NAD+ is required for step 6 of glycolysis (glyceraldehyde-3-phosphate is dehydrogenated into 1,3-bisphosphoglycerate)
This is the first step in glycolysis where ATP is made

37
Q

Why is creatine phosphate important in the body?

A

It acts as a buffer for ATP concentration in muscles
It is a reservoir of phosphate groups which are transferred to ADP to form ATP via creatine kinase when [ATP] falls too low

38
Q

What is the equation for creatine phosphate?

A

Creatine phosphate + ADP –> ATP + creatine

39
Q

What is produced by the link reaction per glucose molecule?

A

2 acetyl CoA
2 CO2
2 NADH

40
Q

What is the overall equation for the link reaction?

A

Pyruvate + NAD + CoA –> AcetylCoA + CO2 + NADH

PoM (14 decks)

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