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Molecular Biology of The Cell - POM > Glucose Metabolism > Flashcards

Glucose Metabolism Flashcards

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1
Q

What is the difference between catabolic and anabolic reactions and pathways

A

In catabolic reactions and pathways, substances are broken down to release energy needed for chemical and mechanical processes in the body. In anabolic reaction or pathways, larger molecules are synthesised from smaller substances, which requires energy, to build molecules needed for storage or structures in the cell and the body.

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2
Q

What are the three main stages of glucose metabolism and where do they occur

A

Glycolysis (cytoplasm), TCA/Krebs cycle (mitochondrial matrix), oxidative phosphorylation (mitochondrial inner membrane)

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3
Q

How is the activation energy in glucose breakdown overcome

A

The enzymes involved in the step-by-step breakdown of glucose can lower the activation energy required for each step to such extent that the body temperature suffices to provide this energy

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4
Q

How efficient is glucose metabolism and how can you calculate this

A

Roughly 40%, calculated by dividing the energy stored in 38 ATP molecules (38 x 31 kJ/mol) by energy in glucose (2872 kJ/mol)

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5
Q

How much energy is released in hydrolysis of ATP

A

31 kJ/mol

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6
Q

In what six types of reaction can all metabolic reaction be categorised

A

Redox reaction, litigation requiring ATP cleavage, isomerisation, group transferring, hydrolysation, group addition or removal

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7
Q

Where does glycolysis occur and how much net ATP and NADH does it produce

A

In the cytoplasm, produces net 2 ATP and 2 NADH

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8
Q

In what two stages can glycolysis be divided

A

Formation of high energy compound requiring ATP investment (step 1-5), breakdown/splitting of high energy compound resulting in ATP production (step 6-10)

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9
Q

What enzyme commits glucose to the cell metabolism

A

Hexokinase, converts glucose to glucose-6-phosphate unable to be transported across membrane

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10
Q

Why is glucose-6-phosphate isomerised

A

Fructose-6-phosphate can in glycolysis be split into more equal parts than glucose-6-phosphate

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11
Q

What enzyme is key in the control of the rate of glycolysis

A

Phosphofructokinase, converts fructose-6-phosphate into fructose-1,6-biphosphate, controls entry of sugars into glycolysis

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12
Q

What is the substrate of aldolase and what are the product

A

Aldolase splits fructose-1,6-biphosphate (substrate) into dihydroxyacetone phosphate and glyceraldehyde 3-phosphate

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13
Q

What enzyme is cause of the only fatal glycolytic enzymopathy and what does it catalyse

A

Triose phospate isomerase, converts dihydroxyacetone phosphate to glyceraldehyde 3-phosphate

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14
Q

What are the cofactors for glyceraldehyde-3-phosphate dehydrogenase and product

A

NADH and inorganic phosphate (cofactors), 1,3-biphosphoglycerate (product)

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15
Q

In what steps of glycolysis are ATP produced

A

In step 7 and step 10, conversion of 1,3-biphosphoglycerate to 3-phosphoglycerate and conversion of phosphoenolpyruvate to pyruvate

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16
Q

What enzyme isomerises 3-phosphoglycerate and what is the product

A

phosphoglycerate mutase, 2-phosphoglycerate (product)

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17
Q

What type of reaction does enolase catalyse and what is the product

A

Hydrolisation/group transfer, phosphoenolpyruvate

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18
Q

What is the enzyme involved in production of pyruvate in last step glycolysis

A

Pyruvate kinase

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19
Q

Which two enzymes are involved in alcohol fermentation of pyruvate

A

Pyruvate decarboxylase and alcohol dehydrogenase, pyruvated converted sequentially into acetaldehyde and ethanol

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20
Q

Which types of organisms is alcohol fermentation characteristic of

A

Yeasts

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21
Q

What enzyme is involved in lactate generation from pyruvate

A

Lactate dehydrogenase

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22
Q

Which types of organisms use lactate generation

A

Animals and certain bacteria

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23
Q

How is NAD+ replenished in hypoxic state of cell

A

By reducing pyruvate to lactate, oxidising NADH to NAD+ to allow glycolysis to continue

24
Q

What is creatine phosphate in cell used for

A

To provide an ATP buffer during strenuous exercise, storing high energy phosphate which can be converted to ATP by creatine kinase

25
Q

How is ATP generated and used during different stages of exercise

A

In first second, existing ATP concentration is used up. In first four seconds, creatine phosphate releases phosphate to ATP to buffer drop in ATP levels. Then anaerobic respiration (glycolysis) takes over ATP production while level of aerobic respiration slowly increases and takes over

26
Q

Why do athletes use creatine as dietary supplement

A

Because this can increase the amount of creatine phosphate in cells and thus provide more energy for the first few seconds of strenuous excercise in muscle cells

27
Q

Which enzyme is needed to enter TCA cycle and what substrates are needed

A

Pyruvate dehydrogenase complex, pyruvate and HS-coenzyme A are needed

28
Q

What origin does Coenzyme A have and why

A

The RNA basis of coenzyme A suggest that it originates from RNA

29
Q

How can acetyl-CoA donate acetate to oxaloacetate and what is the linkage called

A

The thioester bond between acetate and the sulphuratom in coenzyme A is easily hydrolysed, since it is a high energy bond

30
Q

Which cofactor is needed for pyruvate dehydrogenase complex and what is its mechanism

A

Thiamine, easily protonates and subsequently attacks the pyruvate molecule

31
Q

What is name of deficiency of thiamine and the symptoms

A

Beri-Beri, peripheral nerve damage, weakened muscles and decreased cardiac output

32
Q

How many steps are involved in the TCA cycle

A

8 steps

33
Q

What are the products of the reaction of the TCA cycle

A

3 NADH, 1 FADH2, 1 GTP/ATP, 2 CO2

34
Q

Where are the enzymes for Krebs cycle found and what is the exception

A

In the mitochondrial matrix, except succinate dehydrogenase (complex II ETC) that converts succinate to fumarate

35
Q

What can differ between certain cell types regarding the TCA cycle

A

Some cells first create GTP in substate-level phosphorylation step involving succinyl-coA, other cells ATP directly

36
Q

In what two categories can amino acids be divided when metabolism is concerned

A

Glucogenic and ketogenic

37
Q

In how many skeletons can the 20 amino acids be broken down

A

7 carbon skeletons

38
Q

What reactions and enzymes are needed for protein metabolism

A

Transaminations, carried out by transaminases

39
Q

What two substance groups are required for this reaction

A

A ketonic acid and an amino acid

40
Q

How is the amino group from amino acids removed from the body

A

By transferring the amino group to urea

41
Q

Which two shuttles are used to transport high energy electrons into mitochondrion

A

Glycerol phosphate shuttle and malate aspartate shuttle

42
Q

Where are the two different electron shuttles found in the body

A

Glycerol phosphate shuttle is predominantly found in brain cells (neurons) and skeletal muscles, malate aspartate shuttle predominantly in cardiac muscle, liver and kidney cells

43
Q

Which enzyme is required for glycerol phosphate shuttle

A

glycerol-3-phosphate dehydrogenase

44
Q

What are the two substrates involved in cytosolic reaction of glycerol shuttle

A

dihydroxyacetone and NADH

45
Q

What are the two substrates involved in mitochondrial reaction of glycerol shuttle

A

glycerol 3-phosphate and FAD

46
Q

What happens to the electrons after shuttling through glycerol shuttle

A

Electrons in FADH2 are directly passed on to coenzyme Q/ubiquinone

47
Q

Which substance is shuttled in and which out in malate aspartate shuttle and what is intermediate compound

A

Malate is shuttled in, aspartate is shuttled out, oxaloacetate is intermediate compound

48
Q

Which two enzymes are needed for malate aspartate shuttle

A

malate dehydrogenase and aspartate transaminase

49
Q

What are high energy electrons transported to in malate aspartate shuttle

A

To NADH

50
Q

What antiporters are involved in the malate aspartate shuttle

A

The malate antiporter also transports a-ketoglutarate, the aspartate antiporter also transports glutamate

51
Q

What is the Warburg effect in cancer and what causes this

A

Because of genetic mutations in TCA cycle enzymes rendering the enzymes ineffective, cancer cells often preferentially use glycolysis over oxidative phosphorylation

52
Q

How can cancer potentially be treated targeting the Warburg effect

A

By reinstating the TCA cycle by administering effective enzymes, maybe cancerous cells can become normal again

53
Q

Which amino residues are used by kinases to activate or deactivate proteins in cells

A

Serine, threonine, tyrosine by adding phosphate group to hydroxygroup

54
Q

What is the difference between substrate-level and oxidative phosphorylation

A

Substrate-level phosphorylation requires the transfer of phosphate groups by kinases, oxidative phosphorylation requires an electron transport chain

55
Q

How can LDH be used as a diagnostic tool

A

lactate dehydrogenase can be an indicator that cells have died and lysed, releasing the enzyme into the blood. By measuring LDH concentration in blood, cell damage can be estimated and monitored

56
Q

How can glucose metabolism in cancers be used as treatment target or as diagnostic tool

A

Because cancer cells often require more glucose for ATP synthesis by merely glycolysis, the transporter proteins can be inhibit to inhibit energy supply to these cells and labeled glucose can be used to locate tumours in the body

Molecular Biology of The Cell - POM (14 decks)

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