Biochemistry Unit 2

• A monomeric globular protein that carries a heme prosthetic group

  Myoglobin
• A fibrous protein with an unusual triple helical structure that is due to the repeated use of glycine and proline in its primary structure

  collagen
• Where is collagen found?

  All connective tissues: cartilage, bones, ligaments, tendons, skin, and membranes
• What are the functions of glycine and proline in collagen?

  Glycine: very flexible and allows the structure to be more flexible

  Proline: puts kinks in the structure
• A fibrous protein that is part of the cytoskeleton, has heptad repeats in its primary structure, and is responsible for the strength of hari, skin, nails, feathers, and turtle shells.

  Keratin
• Burning hair smells bad because the structure of hair is reinforced by what?

  Disulfide bonds
• What is cornification?


  A process where cells fill with keratin as they die and disulfide bonds form
• Scurvy is a connective tissue disease caused by a lack of ascorbic acid (Vitamin C) in the diet because vitamin C is a necessary cofactor for what?

  Proline hydroxylation. Without it the connective tissue will fall apart
• Failure to strengthen collagen fibers by crosslinking results in a number of connective tissue disorders. Crosslinking of collagen fibers occurs through what?

  Lysine oxidation. It occurs in addition to proline hydroxylation before collagen peptides are exported from the cell. The oxidized lysine residues become crosslinked.
• This protein is part of the cytoskeleton, binds ATP, and is responsible for cellular movement


  Myosin
• What are the four parts of one little movement done by myosin?

  1-myosin cross bridge attaches to the actin myofilament

  2-working stroke-the myosin head pivots and bends as it pulls on the actin filament, sliding it

  3-As new ATP attaches to the myosin head, the cross bridge detaches

  4-as ATP is split into ADP and phosphate, cocking of the myosin head occurs
• What is released from the sarcoplasmic reticulum in response to nerve signaling? (in relation to actin and myosin)

  Calcium
• What is the result of calcium release from the sarcoplasmic reticulum in response to nerve signaling?

  Troponin is removed from the myosin binding site on actin which allows muscle contraction to occur
• What causes myosin to release actin? And what does this do to the muscle fiber?

  Re-uptake of calcium into the sarcoplasmic reticulum and binding of ATP

  The muscle fiber resets
• What happens to ATP that allows the myosin head to rebind to actin?

  it is hydrolyzed and the head is cocked
• This protein is part of the cytoskeleton, binds GTP, and is necessary for mitosis and neuron signaling

  tubulin
• What happens if tubulin runs out of GTP?

  catastrophic depolymerization occurs at the + end
• This protein forms "thick fibers" and binds to actin filaments in muscle cells

  myosin
• What are the 3 basic kinds of mechanisms?

  Acid-base, covalent/nucleophilic catalysis, and metal ion catalysis
• Treadmilling of actin filaments includes what in regard to actin monomers


  actin monomers with bound ADP depolymerizing at the minus end of the filament
• Profilin increases the rate of actin polymerization to favor filament formation by 


  Increasing the rate at which actin monomers exchange ADP for ATP
• If the pool of available ATP in a cell runs low this will cause Actin filaments to


  become stuck in their current conformation
• If the pool of available GTP in a cell runs low this will cause microtubules to

  catastrophically depolymerize from the plus end
• Binding of ATP by Kinesin causes it to

  swing the rear "foot" forward
• Hydrolysis of ATP by kinesin causes it to 


  ATP unbinds the microtubule
• Why does hemoglobin binding have a lag?

  Binding of oxygen to hemoglobin is cooperative - when the first oxygen binds it increase the affinity of the other hemes for oxygen
• What is the basic difference between fibrous and globular proteins?


  Fibrous proteins are structural and globular proteins are functional
• What are two fibrous proteins?


  collagen and keratin
• What affects the catalytic activity of enzymes?

  -proximity and orientation

  -Transition state stabilization

  -->Induced fit-the enzyme binds the transition state better than the substrate or product

  -->Electrostatic catalysis: transition state is stabilized by ionic interactions
• What kind of reaction does an oxidoreductase catalyze? And what is a key characteristic of these reactions?

  Redox reactions and we can tell that an oxidoreductase is the catalyst because NAD+ is converted to NADH in the reaction
• What type of reaction do transferases catalyze?

  Transfer of functional groups
• What type of reaction do hydrolases catalyze?

  Hydrolysis reactions and we can tell because water is added to the reaction
• What type of reaction do lyases catalyze?

  Group elimination to form double bonds
• What type of reactions do isomerases catalyze?


  Isomerization reactions
• What type of reactions do ligases catalyze?

  Bond formation coupled with ATP hydrolysis