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Nutrition Science > Pathways linking Glycogen, Glucose & Pyruvate > Flashcards

Pathways linking Glycogen, Glucose & Pyruvate Flashcards

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1
Q

Glycogen to glucose

A

Glycogenolysis

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2
Q

Glucose to glycogen

A

Glycogenesis

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3
Q

Pyruvate to glucose

A

Gluconeogenesis

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4
Q

Glucose to pyruvate

A

Glycolysis

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5
Q

When does glycogenesis take place?

A

When blood glucose levels are sufficiently high to allow excess glucose to be stored in liver + muscle cells.

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6
Q

What is glycogenesis inhibited by?

A

Presence of G-6-P

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7
Q

What is glycogenesis stimulated by?

A

Insulin

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8
Q

What does insulin do for glycogenesis?

A

Facilitates the uptake of glucose into muscle cells but not req for liver cells.

But, in liver cells insulin does stimulate glycogenesis.

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9
Q

Why does the overall pathway of glycogenesis consume energy?

A

Due to 1 ATP + 1 UTP being consumed for each mol of glucose used.

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10
Q

Where is hexokinase found and where is glucokinase found?

A

Hexokinase = Muscle, brain + adipose tissue

Glucokinase = Liver + pancreas

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11
Q

Relationship of G-6-P with hexokinase + glucokinase

A

Hexokinase = Allosterically inhibited by G-6-P

Glucokinase = NOT inhibited by G-6-P

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12
Q

Which is induced by insulin in NORMAL individuals? - glucokinase or hexokinase?

A

Glucokinase

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13
Q

Glycogenesis

Overview of the change in glucose showing only the substrates

A

Glucose

G-6-P

G-1-P

Uracil-diphosphate glucose (UDP)

Glycogen

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14
Q

GLYCOGENESIS

Enzyme for

Glucose –> G-6-P

A

Glucokinase or hexokinase

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15
Q

GLYCOGENESIS

Enzyme for G-6-P to G-1-P

A

Phosphoglucomutase

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16
Q

GLYCOGENESIS

Enzyme for G-1-P to Uracil-diphosphate glucose (UDP)

A

UDP-glucose pyrophosphorylase

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17
Q

GLYCOGENESIS

Enzyme for

UDP glucose to Glycogen

A

Glycogenin

Glycogen synthase +/or glycogen branching enzyme

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18
Q

What does UDP-glucose consist of?

A

2 P groups + uracil (nucleic acid)

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19
Q

What -ively regulates glycogenesis by disrupting the proteins needed for the process?

A

Epinephrine/Adrenaline

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20
Q

What does epinephrine do to glycogenesis?

A

Stops it + starts glycogenolysis to convert glucose into energy,

Cells need much ATP to overcome the threat.

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21
Q

Where is potential energy found in glycogens?

A

W/in the glucose residues that make up its structure.

In response to the bodys demands, these reduces can be cleaves from the non-reducing ends of the glycogen branches + put through energy releasing pathways.

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22
Q

Where does glycogenolysis take place?

A

Muscle + liver cells

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23
Q

When does glycogenolysis take place?

A

When more energy is needed.

When ATP levels are low

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24
Q

How many units of glucose can 1 mol of glycogen contain?

A

30,000 units of glucose linked together with its centre structure as the protein glycogenin.

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25
Q

How is each glucose mol removed from the glycogen mol?

A

Phosphorolysis

= Breaking down of a molecular bond by adding phosphoric acid

26
Q

Step 1 in glycogenolysis

A

Glycogen phosphorylase breaks the bond linking glucose to glycogen by substituting a phosphoric group PO32-

Glucose that’s been detached is known as G-1-P.

27
Q

GLYCOGENOLYSIS

What happens once a glucose has been detached from glycogen + now known as G-1-P?

A

Phosphoglucomutase converts G-1-P to G-6-P so the cells can make ATP.

28
Q

What is glycogenolysis stimulated by?

A

Epinephrine/adrenaline

29
Q

Equation for glycolysis

A

1 glucose –> 2 pyruvate + 2H20 + 2ATP + 2NADH + 2H+

30
Q

Where does glycolysis occur?

A

Cytosol

31
Q

What does glycolysis require?

A

2 NAD+

2 Pi

2 ADP

32
Q

Oxidised vs reduced NAD

A

Oxidised = NAD+

Reduced = NADH

33
Q

Which steps of glycolysis are the energy requiring ones?

A

1–>5

34
Q

Which steps of glycolysis are the energy releasing ones?

A

6–> 10

35
Q

GLYCOLYSIS

Step 1

A

Phosphorylation: P group is transferred from ATP to glucose = G-6-P

Glucose + ATP –> ADP + G-6-P

By HEXOKINASE

36
Q

GLYCOLYSIS

STEP 2

What happens with the G-6-P?

A

G-6-P –> Fructose-6-phosphate (isomer of G-6-P)

By Phosphoglucomutase

37
Q

GLYCOLYSIS

STEP 3

What happens with fructose-6-phosphate

A

Fructose-6-phosphate –> Fructose-1,6-biphosphate

Through phosphorylation of a 2nd ATP mol.

Catalysed by phosphofructokinase

38
Q

GLYCOLYSIS

STEP 4

What happens with Fructose-1,6-biphosphate

A

Split by aldolase –> Dihydroxyacetone phosphate + Gylceraldehyde-3-phosphate

(isomers of each other)

39
Q

GLYCOLYSIS

STEP 5

What happens to dihydroxyactetone-P

A

Converted into glyceraldehyde-3-phosphate by triose-phosphate isomerase

40
Q

GLYCOLYSIS

STEP 6

What happens to Glyceraldehyde-3-phosphate

A

Oxidised by G-3-P dehydrogenase

Enzyme also catalyses NAD+ –> NADH + H+

== Overall reaction releases energy used to phosphorylate G-3-P to create 2 x 1,3-bisphosphoglycerate mol.

41
Q

GLYCOLYSIS

STEP 7

What happens to each 1,3-biphosphoglycerate mol?

A

Donates a P group to an ADP mol –> 2x ATP + 2x 3-phosphoglcyerate.

By phosphoglycerate kinase

42
Q

GLYCOLYSIS

STEP 8

What happens to each 3-phosphoglycerate mol?

A

Phosphoglyceromutase converts them into 1 x 2-phosphoglycerate mol.

43
Q

GLYCOLYSIS

STEP 9

What happens to the 2-phosphoglycerate mol?

A

Enolase removes 1 H20 mol from it to create 2 mol of phosphoenolpyruvate

44
Q

Net prod of glycolysis

A

2 mol of ATP

2 mol of pyruvate

2 mol of NADH

45
Q

GLYCOLYSIS

STEP 10

What happens to the mol of phosphoenolpyruvate?

A

Phosphoenolpyruvate + ADP –> 2 ATP + 2 Pyruvate

Catalysed by pyruvate kinase.

46
Q

What can happen after glycolysis if O2 is NOT present?

A

Pyruvate is used in anaerobic respiration

47
Q

What can happen after glycolysis if O2 is present?

A

Pyruvate prod can be used in aerobic respiration

48
Q

In gluconeogenesis, Pyruvate can be converted into glucose.

What other substrates can be converted into glucose through this pathway?

A

aa

Lactate

Glycerol

49
Q

Where does gluconeogenesis take place?

A

Mostly in liver

Can happen in small amounts in kidney + small intestine

50
Q

Where does the TCA cycle take place?

A

Mitochondrial matrix

51
Q

When does gluconeogenesis occur?

A

When blood sugar levels become low

52
Q

Steps to gluconeogenesis when using pyruvate as the substrate

A

2 pyruvate mol + ATP –> oxaloacetate (by carboxylation)

Oxaloacetate –> Malate = Red by NADH (can now leave mit)

Once out of mit = Malate –> oxaloacetate (by oxidation)

Oxaloacetate –> phosphoenolpyruvate by PEPCK

Phosphoenolpyruvate –> Fructose-1,6-biphosphate –> Fructose-6-P (Req. ATP)

Fructose-6-P –> G-6-P by phosphoglucoisomerase

G-6-P + ADP–> glucose + ATP by G-6-phosphatase

53
Q

Where does gluconeogenesis begin?

A

Mitochondria or cytoplasm

54
Q

What is the only waste product produced by the TCA cycle?

A

CO2

Must be removed from the cell.

55
Q

What happens after glycolysis breaks glucose into 2 small 3C mol (pyruvate)?

A

TCA cycle transfers their energy to e- carriers for use in the ETC to prod ATP

56
Q

For every 1 pyruvate mol added to the TCA cycle, what is produced?

A

2 mol of CO2

3 mol of NADH

1 mol of FADH2

1 mol of GTP

(X2 due to EVERY glucose mol prod 2 pyruvate mol when broken down).

57
Q

Transformation of pyruvate –> Acetyl-CoA (ready to enter TCA cycle)

A

Pyruvate diff. from cytoplasm into mitochondrial matrix.

Pyruvate is dehydrogenated + decarboxylated to form an (2C) acetyl group each.

Both are picked up by CoA to then become AcCoA (2C)

58
Q

What equation can be used to summarise the link reaction? (Transformation of pyruvate into Acetyl-CoA)

A

Pyruvate + NAD + CoA —- AcCoA + red. NAD + CO2.

59
Q

List the 8 intermediates of the TCA Cycle

A

Oxaloacetate

Citrate

Isocitrate

a-ketoglutarate

Succinyl-CoA

Succinate

Fumarate

Malate

60
Q

How many protein complexes does the ETC have/.

A

4

61
Q

What happens at the start of the ETC?

A

NADH is oxidised at 1st P pump: NADH –> NAD+ + 2H+

High energy e- fuel the 1st P pump to pump these 2H+ from MATRIX –> IM space.

2 e- then passed to mobile e- carrier in membrane to take e-‘s to 2nd pump.

Energy is used to pump 2P across membrane into IM space.

– Repeats at 3rd pump.

2e-‘s passed to 1/2 of an O2 mol (final e- acceptor) to combine w/ 2H+ –> H20.

== P pumps create a P gradient between IM space + matrix == P diff ⬇️ conc grad through ATPsynthase. Energy released is used for ADP + Pi –> ATP.

Nutrition Science (17 decks)

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