MCAT-Biochem

• pH > pI


  Protein loses protons and becomes negatively charged
• pH < pI


  protein gains protons and becomes positively charged
• Racemic mixture


  50% L- and 50% D-
• L- amino acids


  Isoform most enzymes can recognize
• D


  Aspartate (Asp)
• Protein folding


  Driven by hydrophobic effect
• Most soluble proteins have a

  hydrophilic surface and a hydrophobic core
• Hill coefficient


  Sigmoidal curve
• Glutamate (Glu) initial charge at pH 7


  -1
• Aspartate (Asp) initial charge at pH 7


  -1
• Lysine (Lys) initial charge at pH 7 


  +1
• Arginine (Arg) initial charge at pH 7


  +1
• Serine (Ser) initial charge at pH of 7


  0
• Alanine (Ala) initial charge at pH 7


  0
• Kinase


  transfer a phosphate group from a nucleoside triphosphate (ATP) to a target molecule
• TCA cycle occurs in the 


  mitochondria
• Gluconeogenesis occurs primarily in the


  cytosol
• Glycolysis is regulated through enzyme

  Phosphofructokinase-1 PFK-1
• Gluconeogenesis is regulated through enzyme

  Fructose-1, 6-biphosphate
• TCA cycle produces

  3 NADH and 1 FADH2
• Amino acid sequence

  N terminus to C terminus
• Primary protein structure can be altered by

  breaking peptide bonds
• Histidine (His) has an


  ionizable side chain
• Histidine (His) side chain charge at pH 7


  Slightly positively charged or neutral
• Glycolysis 


  consumes NAD+ to produce NADH
• Fermentation in higher eukaryotes converts pyruvate to lactate
• In bacteria and lower eukaryotes (like yeast) converts pyruvate to ethanol
• Fatty acid oxidation (beta oxidation)

  degrade long hydrocarbon chains (=total carbons/2)
• Isoleucine (Iso)


  hydrophobic amino acid
• hydrophobic a.a likely to be found on the surface of

  transmembrane regions (hydrophobic environment)
• Allosteric effectors


  bind to proteins at one site and cause a change in shape of the protein at another site
• Phosphorylation commonly occurs at

  serine, threonine and tyrosine (hydroxyl groups)
• Phosphorylation is a post-translational modification facilitated by

  protein kinase enzymes
• Amino acids with ionizable side chains


  R, K, Y, C, H, E and D
• Ionizable groups can exchange protons with water
• Proteins with large side chains (can cause steric constraints)


  F, I, L, K, M, R, W, and Y
• Beta oxidation = fatty acid oxidation


  Breakdown of fatty acids into Acetyl-CoA in the mitochondria
• Malonyl-CoA inhibits long chain fatty acid transport into the mitochondria
• Beta oxidation decreases in the presence of malonyl-CoA
• Primary structures


  a.a sequence linked by peptide bonds