(1) Mcat Biochemistry I Notes 3u2v5m

BIOLOGY 1 January 25, 2017 Biochemistry I o Four Macromolecules: Protein, Carbohydrates, Lipids, & Nucleic Acids o Condensation reaction= loses water to form polymers o Hydrolysis reaction = adds water to break down polymers into monomers  Biological Macromolecules, Protein o Proteins are synthesized from the N terminus to C terminus o Primary structure: amino acid sequence o Secondary structure: interactions between backbone atoms o Tertiary structure: folding due to side chain interactions o Quaternary structure: side chain interactions with two or more different peptides o Proteins function: enzymes, receptors, channels, porters, intra/extra cellular transport, cell structure, antibodies, hormones, etc.  Biological Macromolecules, Carbohydrates o Monomer = monosaccharides (glucose, fructose, galactose) Also know: ribose & deoxyribose o CxH2xOx o Polymer= Disaccharide  Maltose  glucose + glucose  Sucrose  glucose + fructose  Lactose  glucose + galactose o Polymer = Polysaccharides  Glycogen: animal glucose storage  Starch: plant glucose structure  Cellulose: plant structure (humans cant digest) o Carbohydrate function: cellular energy, cell surface markers, adhesion (unicellular organisms)  Biological Macromolecules, Lipids o Monomer = hydrocarbon o Saturated: containing the greatest possible number of hydrogen atoms (stacks nicely, normally solid) o Unsaturated: having carbon–carbon double or triple bonds and therefore not containing the greatest possible number of hydrogen atoms for the number of carbons. o Lipids have 4 forms in the body:  Triglyceride: glycerol with three fatty acid molecules (energy storage)

BIOLOGY 1   

Phospholipid: amphipathic molecule with a hydrophobic and a hydrophilic component. (cell membrane) Terpenes: built from multiple isoprene units (precursor for cholesterol, steroids) Cholesterol: 3 six carbon rings and 1 five carbon ring (cell membranes, steroid precursor)

 Thermodynamics and Reaction Coupling o Gibb’s Free Energy  ∆𝐺 = ∆𝐻 − 𝑇∆𝑆 o ∆G < 0 = spontaneous (exergonic gives energy); ∆G > 0 = nonspontaneous (endergonic requires energy) o ∆H = enthalpy (potential stored energy) o T∆S = temp x entropy ( kinetic motion energy)  Kinetics and Reaction Coordinate Graph o Transition state= high energy; unstable o If activation energy is low  reaction proceeds faster (inverse relationship)  Catalysts and Enzymes o Catalysts increase reaction rate by stabilizing the transition state and reduces activation energy o ENZYMES DO NOT AFFECT THERMODYNAMICS o Enzymes have 3 characteristics:  Must increase rate of reaction  Must not be used up in the reaction  Specific for a particular reaction  Enzyme Structure and Regulation o Reactants = substrate o Reaction occurs in the active site o Enzyme activity is regulated by phosphorylation and allosteric regulation (alternative binding site) o Negative / inhibition= ending product forms and inhibits the enzyme to stop the reaction. o Positive = ending product forms and enhances reaction to create more product. (must have external regulator)  V vs. [S] Graph o 3 different conditions:

BIOLOGY 1 

[S] < [E]: At low concentration of substrate, there is a steep increase in the rate of reaction with increasing substrate concentration. The catalytic site of the enzyme is empty, waiting for substrate to bind, for much of the time, and the rate at which product can be formed is limited by the concentration of substrate which is available.  [S] = [E]: product formation “levels off” and as the concentration of substrate increases, the enzyme becomes saturated with substrate. As soon as the catalytic site is empty, more substrate is available to bind and undergo reaction. The rate of formation of product now depends on the activity of the enzyme itself, and adding more substrate will not affect the rate of the reaction to any significant effect.  [S] > [E]: Vmax reached o Vmax= The rate of reaction when the enzyme is saturated with substrate is the maximum rate of reaction. o Km= the concentration of substrate which permits the enzyme to achieve half Vmax. (high affinity  low Km (not much substrate needed bc good bonding)  Enzyme Inhibition o Types of Inhibition:  Competitive= binds at active site; Vmax constant; Km increases  Noncompetitive= binds at allosteric site; Vmax decreases; Km constant  Uncompetitive= binds at allosteric site and ES complex; Vmax decreases; Km decreases  Mixed= binds at allosteric site; Vmax decreases; Km varies

 Lineweaver – Burk Plots o Inverse plot: 1/V vs. 1/S