Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry > Day 3 Glycogen > Flashcards

Day 3 Glycogen Flashcards

1
Q

Glycogen

A
  • glucose storage molecule in animals
  • stored in liver to be distributed to other tissues
  • stored in SK muscle to be used in that cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Glycogen structure

A
  • Chain elongation occur at the non reducing end

- can be linearized to produced aldehydes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Glycogen synthesis

Step 1: Phosphoglucomuase

A

Inter-converts G-6-P so G-1-P to enter glycogen synthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Glycogen synthesis

Step 2: UDP glucose phosphorylase

A

-Activate G-6-P by attaching UTP to the phosphate. This is how we get UDP glucose which is the substrate of glycogen synthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Glycogen synthesis

Step 3: Gycogen synthase

A

adds glycosyl residue (UTP glucose) to the non-reducing end of pre-existing glycogen molecule. form an alpha 1-4 link

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Glycogen synthesis

Step 4: Branching enzyme

A

generates the alpha 1-6 linkages via the non reducing ends 4 residues upstream of the previous branch point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Phosphorolysis

A

Glycogen breakdown (glycogenolysis) using a phosphate to cleave the glycosidic linnks. You then end up with a phosphorylated glucose producr and the process conserves energy because it did not use ATP to break the bond.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Glycogen Phosphorylase

A

catalyzes phosphorolysis of the non reducing end of glycogen to produce G-1-P. This is the enzyme that helps the degradation of of glycogen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Phosphoglucomutase

A

converts G-1-P to G-6-P so it can enter glycolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Glucose-6-Phosphotase

A

dephosphoryates G-6-P to form free glucose. This is a liver specific enzyme that maintain blood sugar during fasting conditions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Debranching enzyme

A

cleaves the alpha 1-6 terminal residues at the branch site.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Glycogen Remodeling

A

due to steric factors the debranching enzyme cannot debranche the last 4 glucose residues so the 1-4-glucosyl transferase transfer them to the outer branch forming a longer branch then the debranching enzyme cleave the last molecule from the branch. then glycogen phosphorylase can come and cleave the main branch apart.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Regulation of glycogen metabolism

A
  • primarily regulated by phosphorylation and allosterism.
  • Also controled by insulin glucagon and epinephrine.
  • Glycogen synthase and phosphorylase are key regulatory points
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Phosphorylase regulation

A

Phosphorylation of phosphorylase by PKA converts phosphorylase B (inactive) to phosphorylase a (active. Both forms are subject to allosteric regulation and can exist in either the T form or the R form.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Controls of phosphorylase

A

inactive- low calcium and dephosphorylated
partially active- high calcium and dephosphorylated or low calcium and phosphorylated
fully active- Phosphorylated and high calcium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Allosteric control of phosphorylase in muscle

A 
Energy charge
-high ATP = low activity
-high AMP = high activity 
Product inhibition 
-high G-6-P = low activity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Allosteric control of phosphorylase in liver

A

high glucose = low activity

liver does not undergo large energy charge so energy charge effects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Glucagon effect

A

responds to low blood sugar at the liver

high glucagon = high gluconeogenesis and glycogenolysis but low glycolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Epinephrine effects

A

High levels in the liver
-high gluconeogenesis, high glycogenlysis, low glycolysis
High levels in the muscle
-high glycolysis, high glycogenolysis, low gluconeogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Synthase control

A
  • Phosphorylation by PKA converts synthase A (active) to synthase B (inactive)
  • high G-6-P concentration activates it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Insulin effect

A
  • insulin activates PKB which phosphorylates glycogen synthase kinase (GSK3)
  • the phosphorylation of GSK3 inactivates GSK3 which in turn prevent it from inactivating glycogen synthase
22
Q

PKA

A

PKA is activated by glucagon and epinephrine and both of them want to have glucose in the blood so PKA will

  • increase phosphorylase activity
  • decrease synthase activity
23
Q

Protein phosphatase 1 (PP1)

A

has 3 subunits

  1. catalytic subunit
  2. GM or GL glycogen binding subunit
  3. Inhibitor 1 regulatory subunit
24
Q

PP1 in the muscle

A

phosphorylation of the GM subunit by PKA release the catalytic subunit from glycogen and allow the I1 subunit to bind and inhibit the catalytic unit

25
Q

PP1 in the Liver

A

Glucose levels in the liver prevents the activation of synthase prior to the inactivation of phosphorylase.
1. when glucose levels are low phosphorylase A is in the R form and the PP1 bound to it is inactive.
2. When glucose levels increase phosphorylase A is allosterically converted to the T form
3. PP1 can only act on phosphorylase A when it is on the T form so it then dephosphorylate the A form forming the B form
4 PP1 disassociate from phosphorylase and then bind to synthase
5. PP1 dephosphorylate Synthase to activate it

26
Q

effects of PP1

A

PP1 is an enzyme that dephosphorylate all the activities of PKA so it:
-increase synthase activity
-decrease phosphorylase ctivity
PP1 is only available to activate synthase after it has inactivated phosphorylase

27
Q

The Citric Acid Cycle

A
  • Aerobic metabolism allowing for the complete oxidation of fuel molecules to CO2
  • Generate reduction potential to beapplied to ATP synthesis
  • Occurs in 3 stages
28
Q

Stage 1

A

Conversion of fuel molecules to acetyl CoA via independent pathways to generate reduction potential.

29
Q

Stage 2

A

Oxidation of Acetyl groups and reduction of electron carriers. this stage is a transfer of electrons from Acetyl CoA to NAD+ and FAD

30
Q

Stage 3

A

Oxidation of electron carries NADH and FAD2 and the reduction of O2. Energy released in the electron transport is used to form a proton gradient that will phosphorylate ADP

31
Q

Transition reaction

A

catalyzed by pyruvate dehydrogenae forms acetyl CoA from pyruvate in three steps.

  1. decarboxylation
  2. oxidation
  3. transfer to CoA
32
Q

Pyruvate dehydrogenase structure

A

3 enzymatic subunits E1 E2 E3 that are linked to 3 cofactors which work together with 2 substrate coenzymes.

33
Q

E1

A

pyruvate dehydrogenase contains the co-factor thiamine pyrophosphate TPP. this subunit catalyzes two reactions
1. the decarboxylation of pyruvate
2. the reductive acetylation of the lipoyl group
(the rest of pyruvate is added to TPP and that attacks the lipoyl group(2S) forming an acyl sulfur bond and protonating the other sulfur)

34
Q

E2

A

(this reaction kills E2 because after the acetyl coA is form the disulfide bond of the lipoyl group remains broken)

35
Q

E3

A

dihydrolipoyl dehydrogenase with its FAD electron transfer cofactor catalyzes 2 reactions to regenerate E2

  1. Oxdation of lipoyl group to disulfide (this reeaction is coupled to the reduction of the FAD
  2. transfer of electron from FADH2 to NAD+ (electron acceptor substrate coenzyme) which generates NADH
36
Q

lipoyl

A

This cofactor is utilized by all three enzymatic activity it is located in the E core and have a flexible arm that allows access to all three active site.

37
Q

Regulation of pyruvate dehydrogenase (PDH)

A

PDH catalyzes an irreversible step in glycolysis converts pyruvate to acetyl coA can be regulated by phosphorylation or allosteric and hormonal control

38
Q

Acetyl CoA

A
  • This is the product of thereaction along with NADH

- Can be oxidized to O2 or can be incorparatd into lipids but it cannot be used to generate carbohydrates

39
Q

PDH kinase

A
  • Inactivates PDH by phosphorylating it
40
Q

PDH phosphatase

A

Activate PDH by dephosphorylating it

41
Q

Allosteric and Hormonal control

A
  • Calcium activates phosphatase

- Insulin activate phosphatase to get glucose to convert to fat

42
Q

Story Time

A
  • After glycolysis pyruvate is converted to Acetyl CoA so it can be oxidize and generate electrons. this reaction is catalyzed by pyruvate dehydrogenase PDH. The whole purpose of the conversion is to generate NADH which is a high electron carrier that can generate ATP.
  • The substrates are pyruvate and ADP and the products are NADH, Acetyl CoA and ATP.
43
Q

Subtrate product regulation

A

High ratios of the following stimulate PDH Kinase
1. NADH/NAD
2. Acetyl CoA/ CoASH
3. ATP/ADP
PDH will be inactivated when the charges are high because obviously if the cell have a lot of ATP, Acetyl CoA, and NADH then it does not need to be making them.

Low ratios will stimulate PDH phosphatase and activate PDH. So will pyruvate and high calcium in the cytoplasm.

44
Q

Summary of TCA cycle

A

8 reations:

  • 2 decarboxylation
  • 8 electrons removed trhouh oxidation
  • Generation of 2 NADH and 1 FADH2
  • 1 GTP generated through substrate level phosphorylation
  • Use Oxaloacetate catalytically (regenerated through each cycle)
45
Q

TCA Cycle uses

A

This cycle not only generate energy but it also produces carbon skeletons that are used as precursors of other biosynthetic reaction. Other products include amino acids, nucleotides etc.

46
Q

Anapleuretic Reactions

A

Replenish the TCA cycle intermediates. Pyruvate is the primary source of carbon to replenish the cycle

47
Q

Regulation of the TCA cycle

A

primarily at PDH but within the cylce it is regulated by energy charge and calcium

48
Q

Beriberi

A
  • Due to thiamine deficiency
  • Lack of TPP inhibit E1 of pyruvate dehydrogenase
  • Treatment add thiamine to the diet
49
Q

Mercury and Arsenic

A

Mercury and Arsenic have high affinity for Sulfhydryl groups and so they bind tightly to the reduced lipoyl group the cofactor of E2. Such action inactivates PDH

50
Q

2-3dimercaptopropanol (BAL)

A

Contains sulfhydryl groups and out-compete the lipoyl group for the arsenic

Biochemistry (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions