Samenvatting Class notes - Medical Biochemistry

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- Medical Biochemistry
- Sandra van Vliet
- 2019 - 2020
- Vrije Universiteit Amsterdam
- Biomedische Wetenschappen
479 Flashcards en notities
1 Studenten
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Samenvatting - Class notes - Medical Biochemistry

  • 1567375200 Overview of human metabolism

  • What are the three stages of catabolism?
    1. Breakdown of complex molecules to their component building blocks
    2. Conversion of building blocks to acetyl CoA
    3. Metabolism of acetyl CoA to CO2 and formation of ATP
  • What are free energy carriers?
    • ATP
    • GTP
    • NAD(P)H
    • FADH
  • What metabolites can be converted to acetyl CoA?
    • Fatty acids
    • Ketone bodies
    • Sugar (via pyruvate)
    • Pyruvate
    • Amino Acids (via pyruvate)
    • Ethanol
  • What is homeostasis when speaking of ATP?
    You produce as much ATP as needed.
  • What do you know if the efficiency of a reaction is less than 100%?
    Then heat is generated.
  • What happens when ATP synthase (ATPase) stops?
    When ATPase stops the proton gradient builds up and oxidative phosphorylation comes to a complete stop.
  • How is ATPase regulated?
    ATPase uses energy from the proton gradient to produce ATP. When all ADP is converted to ATP, ATPase stops.
  • What happens with excess acetyl CoA when there is sufficient ATP?
    Excess acetyl CoA is converted to fatty acids and then triglycerides
  • What is produced in the TCA cycle?
    NADH
  • How is the TCA cycle regulated?
    Without NAD+ isocitrate cannot be converted into alpha-ketoglutarate.
    When OXPHOS stops recycling NADH, the TCA cycle will also stop.
    Conversion of pyruvate is the most important regulator of entry in the TCA cycle. The pyruvatedehydrogenase complex (PDH) is controlled by NAD+.
  • Pyruvate acts as a metabolic hub, what can pyruvate be converted into?
    • Alanine
    • Ethanol (fermentation in micro organisms)
    • Acetyl CoA
    • Oxaloacetate
    • Lactate
  • 1567461600 Carbohydrate and glucose metabolism

  • How many glucose is used each day?
    160-200 gram
  • How many glucose does the brain use each day?
    120-150 gram
  • Why do brain/neuronal cells not have beta-oxidation?
    Because they cannot absorb long chain fatty acids (myelin).
  • Why can we not make glucose from FA?
    FA can be broken down to C2, this is a 'passenger' in the TCA cycle. To make glucose we need a 'car', which is a C4 molecule.
  • What stimulates glucagon production?
    Nerves and AA (not low glucose in pancreas).
  • On what does insulin production by beta cells depend?
    [Glucose]
  • Where do you find glucokinase and where do you find hexokinase? What is the difference between these two regarding Km and Vmax?
    Glucokinase: liver and pancreas (high Km, high Vmax)
    Hexokinase: other cells (low Km, low Vmax)
  • Why is glucokinase only present in the liver and pancreas?
    Glucokinase is sensitive to changes in [glucose], this is needed in the liver since the liver only uses excessive amounts of glucose. So when [glucose] is high, glucokinase will be used in the liver.
  • Where do you find GLUT1?
    All mammalian tissues
  • Where do you find GLUT2?
    Liver and pancreatic beta-cells
  • Where do you find GLUT3?
    Neuronal cells
  • Where do you find GLUT4?
    Muscle and fat cells --> insulin sensitive
  • Where do you find GLUT5?
    Small intestine
  • What is the difference in the liver compared to other cells?
    Other cells do not have G6Pase and therefore cannot release glucose back into the bloodstream.
  • What is important about GLUT4?
    GLUT4 is insulin sensitive. It is located on muscle and adipose tissue and can only take up glucose after a meal (when insulin is high).
  • What is fructosemia?
    Fruit intolerance. GLUT5 doesn't work and you get accumulation of fructose in the small intestines.
  • What happens when a patient is lactose intolerant?
    The osmotic pressure in the intestines is raised, causing water to move into the lumen of the intestines.
    Lactose = glucose + galactose. Lactase cuts these two.
  • Where does aerobic glycolysis occur, what about anaerobic glycolysis?
    Aerobic glycolysis: mitochondrium
    Anaerobic glycolysis: cytoplasm
  • What are substrates for gluconeogenesis?
    • Lactate
    • Alanine
    • Glycerol
  • What happens if you eat a high-carbohydrate meal?
    Induction of insulin production.
  • What happens if you eat a high protein meal?
    Induction of glucagon production, leading to gluconeogenesis.
  • When is pyruvate used for the TCA cycle?
    When there is an excess of glucose.
  • How is the TCA controlled via hormones?
    Insulin activates PDH (pyruvate dehydrogenase complex): glucose to acetyl CoA
    Glucagon inactivates PDH: glucose to gluconeogenesis
  • What is the pentose phosphate pathway (PPP)?
    The PPP is a shunt for glycolysis, this produces 2 NADPH that can synthesise FA, reduce glutathione, and help with other reactions.
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