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MC Biochem 2 > Chpt 15 > Flashcards

Chpt 15 Flashcards

1
Q

Metabolism

A

all reactions found in cells

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2
Q

2 types of metabolism

A

1) Catabolism-breakdown
- breakdown of large organic molecules (proteins, lipids, carbohydrates) into smaller molecules (CO2, H2O, lactate)
- Releases Energy which is captured in a usable form as ATP, NADH, NADPH, FADH2 or lost as heat or increase in entropy

2) Anabolism-synthesis
- assembly of smaller precursor molecules into larger more complex molecules (Lipids, polysaccharides, proteins, nucleic acids)
- requires energy

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3
Q

Catabolism

A

Breakdown and release of Energy
Stage 1:
-complex macromolecules broken down into smaller units. -No free energy trapped.
starch-> monosaccharides
protein-> amino acids
triacylglycerols-> glyercols and fatty acids

Stage 2:

  • simple molecules are catabolized to a few molecules that can be oxidized to CO2 and H2O.
  • some energy trapped as ATP

Stage 3:

  • contains: citric acid cycle, electron transport, and oxidative phosphorylation
  • oxidize acetyl CoA to CO2 and H2O
  • Majority of energy trapped as ATP
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4
Q

ATP

A

Adenosine Triphosphate
-principle donor of free energy in biological systems
“Energy Currency of the Cell”
-in vivo nucleotides usually exist in a complex with divalent cations (Mg2+ or Mn2+)

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5
Q

Hydrolysis of ATP

A

Addition of water to cleave peptide bonds

  • cleave of 2 phosphoanhydride (phosphodiester bonds) yields free energy (Exergonic)
  • forms orthophosphate (Pi) or pyrophosphate (PPi)
  • orthophosphate is stabilized by resonance
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6
Q

Phosphoryl-Transfer Potential

A

Measure of how readily an organic molecule will transfer a phosphate group
-determined by measuring delta G^o of hydrolysis of phosphate group

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7
Q

What molecules have a higher phosphoryl-transfer potential than ATP? And Why is this good?

A
  • Phosphoenolpyruvate
  • 1,3-bisphosphoglycerate
  • Creatine Phosphate

-These molecules can transfer a phosphate group to ADP to form ATP during metabolism (regenerates ATP)

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8
Q

Why does ATP have such a higher Phosphoryl-Transfer Potential?

A

1) Resonance Stabilization
- Pi (orthophosphate) and ADP are more stable than gamma phosphate of ATP
2) Electrostatic Repulsion
- at ph7, ATP carries about four negative charges which repel each other.
- Hydrolysis of ATP to ADP + Pi reduces this repulsion
3) Stabilization due to hydration
- water can bind to (solvate) ADP + Pi more efficiently than ATP

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9
Q

ATP-ADP Cycle

A

High turn over Adenylate Pool by motion, active transport, biosynthesis, signal amplification

  • Human adults have 100gATP/ADP/AMP
  • Adult values for rate of use:
    a) Resting= 40,000g/24 hours
    b) Strenuous exercise (running) = 500g/min or 60,000g/2hrs

Oxidation of organic molecules (glucose and fatty acids) is used to regenerate ATP from ADP and Pi

  • Glycolysis
  • pyruvate oxidation
  • Kreb’s cycle
  • electron transport chain
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10
Q

Source of ATP during exercise

A
  • Initially the pool of existing high energy phosphate molecules provide ATP or quick regeneration of ATP by creatine phosphate (SECONDS)
  • Then an increase in the rate of aerobic or anaerobic metabolism (oxidation of glucose and fatty acids) regenerate ATP from ADP and Pi
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11
Q

How is most ATP generated?

A

Most ATP is generated from ion gradients (usually H+) across a membrane

1) Oxidative phosphorylation to create ion gradient
- burning of organic molecules to create an ion gradient to synthesize ATP

1\2) chemiosmotic coupling t ouse proton gradient
-Use of proton gradient by ATP synthase (complex V) to synthesize ATP

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12
Q

NAD+

A

Nicotinamide Adenine Dinucleotide (oxidized form-NAD+)

  • coenzyme
  • Niacin is vitamin precursor to NAD+
  • deficiency-pellagra resulting in dermatitis, depression, diarrhea

Function-electron carrier

  • oxidation of fuel molecules in synthesis of ATP
  • H, 2e-, H+
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13
Q

NADP+

A

Nicotinamide adenine dinucleotide phosphate

  • coenzyme
  • Niacin is vitamin precursor to NADP+
  • Deficiency-pellegra resulting in dermatitis, depression, diarrhea

Function:

  • electron carrier
  • in reductive biosynthesis
  • hydride ion and proton (H + 2e-)
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14
Q

FAD

A

Flavin adenine dinucleotide (FAD/FADH2)

  • coenzyme
  • Vitamin-riboflavin (Vitamin B2)
  • deficiency-cheliosis and angular stomatitis (lesions of the mouth) dermatitis

Function: electron carrier
-oxidation of fuel molecules in synthesis of ATP

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15
Q

CoA

A
  • coenzyme
  • vitamin-pentothenate is a vitamin precursor
  • deficiency-hypertension

Function: carries acyl units (8-12 C’s) and linked to SH by thioester bond
-a=acetylation

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16
Q

Vitamins

A

organic molecules that are needed in small amounts in the diet of some higher animals

  • many (not all) vitamins are metabolized into coenzymes
  • vitamin deficiency leads to disease state
17
Q

Enzyme Classes

A

OTH LiL-T; 2-CNP, 4-CNS; 6CONS

EC1-oxidoreductase-catalyzes oxidation/reduction reactions
EC2- transferase-catalyzes the transfer of C, N, or P containing groups
EC3- Hydrolase- catalyzes the cleavage of bonds by addition of water
EC4- Lyase- catalyzes the cleavage of C-C, C-S, and some C-S bonds
EC5-Isomerase- catalyzes the racemization of optical and geometric isomers
EC6-Ligase-catalyzes the formation of C, O, N, or S bonds coupled to Hydrolysis of high energy Phosphate
EC7-Translocase- catalyzes the transfer of a molecule from one side of membrane to the other side of membrane

18
Q

Common Enzyme Names

A

Kim-DA; tii-o_
Kinase (transferase)-transfer of a phosphate group from one molecule(Gamma phosphate of ATP) to another molecule
Isomerase (isomerase)- converts molecule to another isomer. Rearranges atoms in the molecule without gain or lose of atoms
Mutase (isomerase)- shift of phosphate from one carbon to another carbon in the same molecule
Dehydrogenase-require NAD+ and FAD+; oxidation/reduction reaction
Aldolase (lyase)- cleaves c-c bonds (Reverse Aldol condensation reaction)

19
Q

Metabolic States

A

1) Fed
- occurs during and just after (3-4 hours) a meal
2) Fasting
- occurs HOURS (6-8 hours) after eating
3) Starvation
- occurs after extended fasting (DAYS)

20
Q

Regulation of Metabolic Pathways

A
  • compartmentalization
  • hormonal control
  • non-hormonal control
  • Flux of key metabolic intermediates
  • specialized roles of organs/tissues
21
Q

Comparmentation

A

REGULATION OF METABOLIC PATHWAYS

1) Cytosol
- Glycolysis
- Pentose phosphate pathway
- Fatty acid synthesis
2) Mitochondrial Matrix
- Citric acid cycle
- Oxidative phosphorylation
- Oxidation of fatty acids
- Ketone bodies formed
3) BOTH
- Gluconeogenesis
- Urea cycle

22
Q

Hormone Control

A

1) Insulin
- signals the fed state, the availability of glucose in the blood
2) Glucagon and Epinephrine
- When there is low levels of glucose in the blood signals the fasting state
3) Epinephrine
- signals stressful states when mobilization of fuel is required

23
Q

Non-hormonal Control

A

1) Allosteric control
- activity of key enzymes is modulated by the levels of metabolites which act as activators or inhibitors
- key enzyme=rate-limiting; committed step in pathway
a) Glycolysis
b) Gluconeogenesis
c) Fatty acid synthesis

2) Respiratory Control
- flux of the pathway matches the need of the cell for ATP
a) citric acid cycle
b) Fatty acid synthesis
c) oxidative phosphorylation

3) Substrate Availability
- pentose phosphate pathway
- urea cycle

4) covalent moderation.
- hormone triggered reaction cascades result in covalent modification
a) glycogenesis
b) glycogenolysis

24
Q

Flux of Key Metabolic Intermediates

A
  • Glucose 6-phosphate
  • Pyruvate
  • Acetyl CoA
25
Q

Glucose 6-phosphate

A

KEY METABOLIC INTERMEDIATES

  • Glucose from Gluconeogenesis
  • Glucose 1-phosphate used in glycogen synthesis
  • Pyruvate via glycolysis
  • Ribose 5 phosphate for nucleotide synthesis via pentose phosphate pathway
26
Q

Pyruvate

A
  • Oxaloacetate metabolized via citric acid cycle
  • Actyl CoA via oxidative, decarboxylation (pyruvate dehydrogenase)
  • Alanine via transamination
  • Lactate in muscle tissue
27
Q

Acetyl CoA

A

1) Oxidized to carbon dioxide in citric acid cycle
- decarboxylation of pyruvate
- degradation of fatty acid
2) Fatty acids synthesis
3) 3-hydroxy-3-methylglutaryl CoA
- ketone bodies
- cholesterol

28
Q

Specialized roles of Organs/ Tissues

A

Tissue dependent metabolism

  • All metabolic pathways are not present in all cells and tissue
  • Metabolic profiles of the major tissues vary depending upon the metabolic state of the body
    a) Liver
    b) skeletal muscle
    c) Heart muscle
    d) Adipose
    e) Brain
29
Q

Liver

A

SPECIALIZED ROLES

1) maintenance of Blood glucose levels
- Fed State- takes up excess glucose and stores it as glycogen or converts it to fatty acids
- Fasting state- exports glucose derived from glycogen AND gluconeogenesis
2) Fatty acid synthesis
3) Ketone body synthesis- during fasting state
4) Synthesis of plasma lipoprotein

30
Q

Skeletal Muscle

A
  • maintains stores of glycogen=source of glucose for energy during exertion
  • resting muscles prefer fatty acids as fuel
  • Muscle protein may also be used as fuel
31
Q

Heart Muscle

A

contains NO fuel reserves

-must be continuously supplied with fuel from blood

32
Q

Adipose Tissue

A

Primary function is storage of metabolic fuel in the form of triacylglycerol

  • Fed State-synthesizes triacylglycerols from glycerol and fatty acids
  • Fasting State- triacylglycerols are converted to glycerol and fatty acids
33
Q

Brain

A

Uses Glucose as exclusive fuel source

  • Fed State- glucose
  • Fasting State- adapts to use of ketone bodies

Contains essentially no fuel reserves and must be continuously supplied with fuel from blood

MC Biochem 2 (31 decks)

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