Session 2 Flashcards
Define Cell metabolism
Highly integrated network of chemical reactions that occur within cells
What do cells metabolise nutrients for?
Energy for cell function
Building block molecules
Organic precursor molecules
Biosynthetic reducing power
Define Catabolism
Breakdown of larger molecules into smaller ones
Define Anabolism
Smaller molecules are built up into larger ones
What are the properties of Catabolism?
Oxidative
Release large amount of energy
What are the properties of Anabolism?
Reductive
Uses ATP
Define Exergonic
Energy releasing
What is Creatinine Phosphatase
A reserve of high energy that can be used immediately. Catalysed by creatine kinase
What are the high energy signals?
ATP
NADH
NADPH
FAD2H
What are high energy signals?
Signals the cell has adequate energy levels for its immediate needs or reducing power is available for anabolism.
What are 2 important physico-chemical properties of carbohydrates?
Hydrophillic
Partially oxidised
What are the properties of Glycogen?
Polymer of glucose found in animals. The units join together in alpha-1,4 and alpha-1,6 glycosidic linkages.
Glycogen is highly branched
What are the properties of Cellulose?
Found in plants - structural role. Glucose monomers are joined by Beta-1,4 linkages to form long linear polymers.
Humans do not posses the required enzymes to digest Beta-1,4 linkages.
How are dietary Polysaccharides digested?
Hydrolysed by glycosidase enzymes. Releases glucose, maltose and leaves dextrins.
Begins in the mouth with salivary amylase and continues in the duodenum with pancreatic amylase.
How are dietary Disaccharides digested?
Occurs in the duodenum and jejunum
Glycosidase enzymes involved are attached to the brush border membrane of the epithelial cells lining these regions.
What are the major disaccharide giestion enzymes?
Lactase, glycoamylase and sucrase/isomaltase
What does a low activity of Lactase cause?
Reduced ability to digest the lactose present in milk products - lactose intolerance.
Define Glycolysis
Central pathway in the catabolism of all sugars. Has 10 enzyme-catalysed steps that occur in the cell cytoplasm
What is the function of Glycolysis?
Makes ATP Makes NADH Makes molecules for anabolism No loss of CO2 Glucose oxidised to Pyruvate Involves substrate level phosphorylation Exergonic NET ATP = 2
Which steps of Glycolysis are irreversible?
1 (Hexokinase, Glucokinase in the Liver), 3 (Phosphofructokinase-1) & 10 (Pyruvate Kinase)
How is Lactic acid/Lactate produced?
Pyruvate is reduced to lactate by the enzyme lactate dehydrogenase (LDH). In Anaerobic respiration.
LDH increases NAD+ concentrations under anaerobic conditions for Glycolysis to proceed
What happens to Lactate?
Released into the circulation where it is converted back to Pyruvate and oxidised to CO2 (heart muscle) or converted to glucose (liver)
How is Lactate controlled?
Usually amount used = amount made
Once >5mM exceeds renal threshold and effects buffering capacity of the plasma = Lactic acidosis
Define Galactosaemia
Individuals are unable to utilise galactose obtained from the diet because a lack of Galactokinase or Galactose 1-phosphate uridyl transferase
How can you tell which enzyme is absent in Galactosaemia?
Kinase enzyme - rare, characterised by accumulation of galactose in tissues.
Transferase - more common serious as galactose and Galactose 1-Phosphate (which is toxic to the liver) accumulate in tissues.
What does accumulation of Galactose cause?
Reduction to Galactitol (aldehyde group reduced to alcohol group) by the activity of the enzyme aldose reductase.
Depletion of NADPH
Cross-linking of lens proteins by S-S bond formation cannot be stopped - cataracts.
Glucomas can occur
