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DEMS unit 2 > carbs > Flashcards

carbs Flashcards

1
Q

Glucose transporters

A
  • insulin sensitive – Glut 4 – increases glucose transport in cell following insulin exposure (sk muscle/adipose)
  • insulin independent- Glut 2 - in liver–
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2
Q

where does glycolysis occur

A

cytoplasm

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3
Q

3 types of chemical reactions in glycolysis

A
  • degrade glucose –> pyruvate
  • phosphorylate ADP –> ATP
  • generation of NADH
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4
Q

substrate level phosphorylation

A

phosphorylate ADP-> ATP during glycolysis

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5
Q

oxidative phosphorylation

A

in mitochondria

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6
Q

First reaciton in glycolysis

A

glucose –> G6P

  • hexokinase or glucokinase mediated
  • irreversible
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7
Q

what does glucose phosphorylation accomplish

A
  • give intermediate net charge to trap it in cell
  • conserves energy
  • binding of G6P phosphate to active site of next enzyme lowers activation energy
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8
Q

Hexokinase I

A
  • not selective
  • in all cells
  • low Km for sugars
  • Inhibited by G6P
  • more active at lower glucose concentrations(i.e. during fasting)
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9
Q

Glucokinase

A
  • selective for glucose
  • liver, pancreatic Beta-cells
  • High Km for glucose
  • inhibited by F-6-P
  • more active at higher glucose concentrations
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10
Q

PFK1

A

catalyzes reaction of F6P -> F 1, 6 bisphosphate

  • 2nd ATP investment
  • rate-limiting and committed step of glycolysis
  • irreversible
  • allosteric enzyme
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11
Q

what inhibits PFK 1

A

ATP/citrate

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12
Q

what stimulates PFK 1

A

AMP

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13
Q

PFK2

A

can convert F6P to F 2,6, BP

F2,6BP most potent activator of PFK1

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14
Q

5 parts of cab metabolism

A

Glycolysis, TCA cycle, Gluconeogenesis, Glycogen synthesis/breakdown, Pentose Phosphate Pathway

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15
Q

Km

A

concentration at which reaction is half maximal
- Low Km = substrates have strong affinity for enzyme and reaction will go at low substrate concentrations
-

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16
Q

Vmax

A

maximal rate an enzyme-catalyzed reaction

- High Vmax = produce a lot of product in small period of time

17
Q

3 types of key steps

A

1- molecule changes location in cell (moves across membrane)
2 - body invests energy (often P from ATP)
3- rate-limiting step

18
Q

Key steps in glycolysis

A
  • Glucose enters cell
  • Glucose –> G6P
  • F6P –> F1,6,BP
  • PEP –> pyruvate
19
Q

significance of G6P

A

phosphorylating glucose traps it within cell due to charge

20
Q

Rate-limiting step of glycolysis

A

F6P–> F1,6BP via phosphofructokinase (PFK)

21
Q

Fate of pyruvate

A
  • with O2 –> TCA cycle
  • No O2 – convert to lactate and exported from cell; regenerates NAD from NADH to allow continuation of glycolysis
  • pyruvate from lactate or amino acid metabolism can also enter TCA as oxaloacetate during gluconeogenesis
22
Q

where does glycolysis happen

A

cytosol of cell

23
Q

Where is the electron transport chain

A

inner mitochondrial membrane

24
Q

Key regulated steps in gluconeogenesis

A

1) Pyruvate –> PEP through oxaloacetate and malate; pyruvate carboxylase and PEP carboxykinase
2) F1,6BP –> F6F via Fructose1,6bisphosphatase
3) G6P –> Glucose: allows it to leave cell and only happens in liver/kidney (NOT muscle/adipose)

25
Q

Sources of carbon for gluconeogenesis

A

(these substrates transported to liver)

  • lactate from glycolysis in muscle or RBC
  • amino acids from protein breakdown in muscle
  • glycerol from triglyceride breakdown in adipose tissue
26
Q

Glycogen

A
  • when excess glucose
  • G6P -> G1P -> UDP-glucose : key step for synthesis/breakdown
  • 2nd key step adds UDP-glucose to glycogen molecules with glycogen synthase (removes with Glycogen phosphorylase)
27
Q

Glycogen phosphorylase

A

removes glucose from glycogen when needing glucose

28
Q

how is glucose added to glycogen

A
  • add individual glucose in 1,4 orientation

- for breakdown, glycogen broken from terminal ends until branch point – enzyme takes apart branch point

29
Q

Functions of pentose phosphate pathway

A
  • Generate NADPH for fatty acid biosynthesis, cholesterol biosynthesis, defense against oxidative stress and white cell function
  • generate 5 carbon sugars for nucleotide synthesis
30
Q

key regulated step in pentose phosphate pathway

A

Glucose-6-Phosphate dehydrogenase (G6P –> 6 phosphogluconolactone)

31
Q

Regulation through pathway depends on

A
  • amount of substrate
  • levels/amount of key enzymes
  • allosteric regulation– can change Km or Vmax
  • Covalent modification (phosphorylation)–common with hormones (insulin/glucagon)–can also change Km or Vmax
32
Q

How can the body change Km or V max of a reaction

A

allosteric regulation or covalent modification of key enzyme

33
Q

Counter-regulatory hormones

A

glucagon, catecholamines, growth hormone, cortisol

34
Q

What happens in fed state

A

Insulin high, counter regulatory hormones low,

  • glycolysis/glycogen synthesis active and glucose assimilated by peripheral tissues
  • gluconeogenesis/glycogen breakdown reduced
35
Q

fasting state

A
  • Insulin low, counter-regulatory hormones high

- Gluconeogenesis/glycogen breakdown increased

DEMS unit 2 (4 decks)

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