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Biochem 2 > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Why is glucose stored as glycogen and not as monomers?

A

-if stored as a larger molecule, there are less moles of it = helps regulate amount in the body

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2
Q

What type of links do the branches of glycogen have?

A

-a-1,4 and a-1,6

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3
Q

What is at the core of glycogen?

A

-glycogenin

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4
Q

What is the reducing end also known as?

A

-the anomeric end

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5
Q

What are the four components of glycogenesis?

A

-glycogenin (core protein/enzyme)
-glycogen synthase
-branching enzyme
-starts with UDP-glucose (sugar nucleotide)

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6
Q

What is glycogenesis?

A

-synth of glycogen

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7
Q

What does UTP do to glucose?

A

-activates glucose for further met
UTP+glucose = UDP-glucose+Pi

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8
Q

What are the three steps of the branching enzyme?

A
  1. a few glucose residues are added to the chain by glycogenin
  2. glycogen synthase continues chain, branching enzyme cuts the chain
  3. the cut part is reattached using a-1,6 link to create a branch
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9
Q

What is glycogenolysis?

A

-the breakdown of glycogen

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10
Q

What are two crucial components to glycogenolysis?

A

-glycogen phosphorylase + Pi
-Glycogen debranching enzyme

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11
Q

What are the three steps to glycogen breakdown?

A
  1. glycogen phosphorylase removes terminal glucose residues until is four units away from a branch
  2. debranching enzyme moves three of the glucose units found at a branch to another chain
  3. debranching enzyme removes remaining glucose residue found at branch point
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12
Q

What is the main regulator of both glycogen phosphorylase and glycogen synthase?

A

-PKA

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13
Q

What type of regulation is shown by glycogen phosphorylase and glycogen synthase?

A

reciprocal regulation of processes

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14
Q

what activates the conversion of glucose to glycogen and deactivates the conversion of glycogen to G1P?

A

dephosphorylation

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15
Q

What deactivates the conversion of glucose to glycogen and activates the conversion of glycogen to G1P?

A

phosphorylation

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16
Q

What two molecules are allosteric regulators?

A

-ATP and G6P

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17
Q

What does A and B refer to in enzyme naming convention?

A

A = active
B = less active

18
Q

What is glycogen phosphorylated/inactivated by?

A

-GSK-1
-PKA

19
Q

What is glycogen synthase regulated by?

A

-PKB
-PP1
-G6P

20
Q

What phosphorylates/activates glycogen phosphorylase?

21
Q

What is glycogen phosphorylase dephosphorylated by?

22
Q

What is glycogen metabolism dependant on?

23
Q

What is PKA dependant on?

24
Q

What are two ligands that commonly use GPCR?

A

-glucagon
-epinephrine

25
Q

What are the steps to a GPCR cascase?

A
  1. ligand binds to receptor
  2. alpha subunit exchanges GDP for GTP
  3. Ga subunit dissociates, leaves complex, and activates adenylyl cyclase
  4. adenylyl cyclase produces cAMP from ATP
  5. cAMP binds to reg subunits of PKA = activates it
  6. catalytic subunits on PKA dissociate
  7. PKA phosphorylates glycogen synthase, glycogen phosphorylase, and PP1
26
Q

What does insulin cascade stimulate?

A

-glycogenesis
-PP1 (= blocks glycogenolysis)

27
Q

What are the steps to insulin signalling?

A
  1. insulin binds to receptor -> dimerization of receptor -> recruit IRS-1
  2. IRS-1 activates PI3K -> converts PIP2 to PIP3
  3. PIP3 activates PDK1
  4. PDK 1 phosphorylates Akt
  5. Akt phosphorylates GSK-3 -> inactive
  6. GSK-3 phosphorylates glycogen synthase -> inactive
28
Q

What is the relationship between GSK-3, Akt, and glycogen synthase?

A

-if Akt phosphorylates GSK-3 into GSK-3-P, then GSK is inactive -> glycogen synthase is active

-is Akt does not phosphorylate GSK-3 -> GSK is active -> it phosphorylates glycogen synthase -> glycogen synthase becomes inactive

29
Q

What does insulin in the muscle and liver signal to glycogenesis?

A

-increase it

30
Q

What does insulin in the muscle and liver do to glycogenolysis?

A

decrease it

31
Q

What does glucagon or epinephrine signal do to glycogenesis?

A

decrease it

32
Q

What does glucagon and epinephrine signals do to glycogenolysis?

A

increase it

33
Q

What are the products of the pentose phosphate pathway?

A

-monosaccharides
-NADPH
-antioxidants

34
Q

What are the two phases of PPP?

A

-oxidative
-non-oxidative

35
Q

What are the products of the oxidative phase of PPP?

A

-pentoses
-NADPH
-CO2

36
Q

What are the products of the non-oxidative phase of PPP?

A

-glycolysis intermediates (F6P, GAP)
-R5P which can make nucleotides

37
Q

What is the first step in PPP?

A

G6P -> CO2 + Ru5P + NADPH

-this is the oxidative phase

38
Q

What is the first step of PPP regulated by?

A

-levels of NADPH

39
Q

How can monosaccharides be altered for entry into glycolysis?

A

PPP can convert them into hexoses

40
Q

What is glutathione?

A

-electron carrier
-can be reduced by NADPH
-helps with removing O2 radicals

Biochem 2 (7 decks)

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