Biochemistry

• Glycolysis


  The process of oxidizing a molecule called glucose
• Glucose


  A six carbon monosaccharide (sugar) obtained from the diet
• Cell membrane


  Glucose cannot passively diffuse through, it requires specialized transporters called GLUT transporters
• GLUT transporters


  • GLUT1
  • GLUT2
  • GLUT3
  • GLUT4
• GLUT1


  Found in red blood cells, fetus, and blood-brain barrier
• GLUT2


  Found in kidney, liver, and pancreas
• GLUT3


  Found in placenta, neurons, and kidney
• GLUT4


  Insulin-dependent, found in muscle and adipose tissue
• Glucose entry into cell

  1. Transported by GLUT transporter

  2. Phosphorylated by hexokinase or glucokinase to glucose-6-phosphate
• Hexokinase


  Enzyme that phosphorylates glucose in most tissues
• Glucokinase


  Enzyme that phosphorylates glucose, primarily found in the liver
• Conversion of glucose-6-phosphate to fructose-6-phosphate


  Catalysed by phosphohexose isomerase
• Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate

  Catalysed by phosphofructokinase-1 (PFK-1), an irreversible step
• Fructose-1,6-bisphosphate


  Six carbon sugar with two phosphate groups
• Cleavage of fructose-1,6-bisphosphate


  Catalysed by aldolase, forming dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P)
• Conversion of DHAP to G3P

  Catalysed by triose phosphate isomerase
• Glyceraldehyde-3-phosphate (G3P)


  Three carbon sugar with one phosphate group
• Conversion of G3P to 1,3-bisphosphoglycerate

  Catalysed by glyceraldehyde-3-phosphate dehydrogenase
• 1,3-bisphosphoglycerate


  Three carbon sugar with two phosphate groups
• Carbon


  The carbon atom that the phosphate is attached to
• 1,3-Bisphosphoglycerate


  A 3-carbon molecule with phosphates on the 1st and 3rd carbons
• Glyceraldehyde 3-phosphate dehydrogenase (GAPDH)


  • Enzyme that:
  • Adds NAD+ and an inorganic phosphate
  • Converts glyceraldehyde 3-phosphate into 1,3-bisphosphoglycerate
• Fructose 1,6-bisphosphate is converted into

  Dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GA3P)
• Two NADH molecules are produced from the conversion of two GA3P molecules
• 1. Phosphoglycerate


  A 3-carbon molecule with a phosphate on the 3rd carbon
• Phosphoglycerate kinase


  • Enzyme that transfers a phosphate from 1,3-bisphosphoglycerate to ADP, producing ATP
• 1. Phosphoglycerate


  A 3-carbon molecule with a phosphate on the 2nd carbon
• Enolase


  • Enzyme that converts 2-phosphoglycerate into phosphoenolpyruvate
• Phosphoenolpyruvate (PEP)


  A 3-carbon molecule with a phosphate in an enol form
• Pyruvate kinase


  • Enzyme that transfers a phosphate from PEP to ADP, producing ATP
• Glycolysis produces a net of 2 ATP, 2 NADH, and 2 pyruvate molecules
• In anaerobic conditions


  NADH transfers its hydride to pyruvate, converting it to lactic acid
• Lactate dehydrogenase


  • Enzyme that catalyzes the reversible conversion of pyruvate to lactic acid
• High lactate dehydrogenase levels can indicate conditions with limited oxygen supply, such as myocardial infarction or ischemia
• Biochemistry


  Science that uses the principles of chemistry to understand the molecules of life
• Molecules of life


  • From small molecules to large ones like proteins and assemblies of proteins
  • Used to understand how chemistry or metabolism happens in the cell
  • Used to understand how and why the different components of the cell function as they do
• All the functions of the cell are ultimately governed by the functions of its organelles and supramolecular complexes like the plasma membrane, then the molecules and macromolecules in them, and ultimately their building blocks or monomers units like amino acids
• Chemical elements relevant in biology

  • Metals important in catalyzing the chemistry in the cell
  • Iodine in the thyroid hormone
  • Sodium, potassium and chlorine for ionic balance and signaling in nerve cells
• Main elements of life

  • Hydrogen
  • Carbon
  • Nitrogen
  • Oxygen
  • Phosphorus
  • Sulfur
• Ability of an element to form chemical bonds

  Depends on unpaired electrons in the outer or valence shell of the atoms