NUTR 600 - Preliminary Review

Oxidoreductase - enzyme in redox rxn

Dehydrogenase - transfers electrons and hydrogens from donor to another molecule (oxidizes donor)

Oxidase - transfers electrons and hydrogens from donor to oxygen (oxidizes donor)

Transferase - transfers part of one molecule to another X-Y + Z --> X + Y--Z

Hydrolase - cleavage of bonds w/ addition of water (cleaves C-O, C-C, C-N, etc) The donor group is transferred to water.

Lyase - cleaves C-O, C-C, C-N, leaving double bonds or adding groups to double bonds.

Isomerase - changes geometric/spatial configuration of a molecule

Epimerase, racemase, mutase

Ligase - uses the energy derived from hydrolysis of high energy bond (ATP) to join 2 molecules)

Synthetase

Kinase - adds PO3 (phosphate) group to a molecule, generally obtains PO3 from ATP.

Phosphatase - removes phosphate group from molecule.

Fatty acid (saturated)

Can also be unsaturated.

TAG

Phospholipid.

Sterol: ex. Cholesterol, bile acids, cortisol, estrogen, testosterone, vitamin D, purine, pyrimidine

Polar compounds are hydrophilic and water-soluble

Nonpolar compounds are hydrophobic and fat-soluble

Substrate and reactant are the same thing (both on left sides of equation), except called substrate when rxn is done by enzyme.

Binding affinity - strength of binding by noncovalent interactions between two molecules

• 1. Precursor - a substance from which another is formed
• 2. Product - something manufactured from substrate by enzyme

Km - roughly an inverse measure of binding affinity bt substrate and enzyme (lower Km, higher affinity)

Also, Km = the substrate concentration that produces a Vi that's half of Vmax

Km stands for Michaelis-Menten Constant

Vmax - maximum velocity of the rxn.

• 1. Cell Diff - normal process by which a less specialized cell develops/matures to possess a more distinct form and function.
• 2. Mitogen - substance that induces/stimulates mitosis
• 3. Mitogenesis - Induction of mitosis in cell

In Vivo - experimentation done in or on living tissue of a whole, living organism as opposed to a partial/dead organism.

In vitro - experimentation done in controlled environment outside of living organism, for example in petri dish or test tube.

• 1. Help reactions go faster by lowering activation energy
• 2. Are specific for their substrates
• 3. Active site mechanism is like lock and key

• 1. Substrate availability
• 2. Conformational change - allosteric binding sites (immediate) and covalent modification (second to minutes)

Mechanism: Effector molecule binds noncovalently to enzymes at a site other than active site, changing the shape of the active site.

Results: This binding causes change in affinity of enzyme for its substrate or alters its rxn rate (maximal activity) OR BOTH.

Effectors: substrates, products, or other small molecules

The effect takes place immediately.

Mech: Phosphate has negative charge and alters enzyme shape or conformation

Usually, phosphorylation or dephosphorylation

Catalyzed by protein kinases and phosphatases (ATP and ADP too)

seconds to min

• 1. Long term (gene expression) - SREBP
• 2. Permanent compartmentation - Enzymes are segregated into specific cells/compartments/organelles; transcription
• 3. Variable compartmentation - GLUT 4 recruitment for intracellular pool

Gene expression - can increase/decrease amount of enzyme present in cell.

By altering rate of transcription/translation to get new protein synthesis

Hours to days

• 1. Rate-limiting step
• 2. Committed step
• 3. Irreversible rxn (ATP consuming)
• 4. At a branch point in pathway

Active transport requires energy, requires movement of molecules against electrochemical gradient.

Passive transport does NOT require energy, molecules travel from higher concentration to lower concentration through concentration gradient.

Rate of enzyme synthesis and degradation

Enzyme deficiency (partial or total) OR drug

To control import!!

 To increase entry of molecule in short supply, in response to physiological condition (glucose entry into muscle),

increase/decrease entry of useful but pot toxic molecule (iron), in response to specific & changing cell requirements (cholesterol)

Maintain membrane polarization (Na+/K+), export molecules in a regulated way (HCl secretion), maintain intra/extracellular concentrations.

Diffusion

• Passive movement according to concentration gradient across membrane
• - molecules pass freely through the lipid bilayer
• - no need for protein transporter

Something to drag them out of the lipid on the other side of membrane

Requires molecule to specifically bind to a transporter, probably with a change in the transporters shape.

The molecule is moved to the opposite side of the membrane in the process.

The molecule then disassociates from the transporter which changes its shape back to its conformation.

Diffusion - movement of molecules increases in proportion to EC concentration, no binding site needed. When the concentrations inside and outside become equal, its in equilibrium.

Mediated transport - movement of molecules reaches max value when all available transport proteins are saturated. Any increase in EC concentration will not change rate of entry into cell.

• (1) Facilitated diffusion aka passive trasnport
• (2) Active transport

• - Binding resembles substrate-enzyme interaction:
• - Has specific binding site
• - Is saturable (so there's a max rate of transport - Vmax)
• - Has a binding constant/affinity for its solute (Km)
• - Can be inhibited by structurally similar competitive inhibitor

• 1. Concentration gradient across membrane
• 2. Amount of carrier - KEY CONTROL STEP!
• 3. Rate of solute-carrier interaction
• 4. Rate of conformational change for the loaded & unloaded carrier

1. Facilitated: high conc to low conc until both sides are equal, doesn't req energy, bidirectional

2. Active: against electrochemical gradient, usually unidirectional, requires energy

Maintenance of electrochemical gradient takes 30-40% of total energy

Primary active - DIRECTLY coupled to hydrolysis of ATP

Secondary active - uses ion concentration gradient (set in place by primary active transport) as energy source.

Transporter binds to ion, movement can be in same direction (co-transport) or opposite (counter-transport)

Na+ --> EC

K+--> IC

• (1) Requires effector molecule vs.  kinases or phosphatases
• (2) Binds noncovalently to site different from active site vs binds covalently to serine, threonine, or tyrosine residues.
• (3) Effector changes shape of substrate binding site vs phosphate group has negative charge changing enzyme shape/conformation
• (4) Immediate effect vs seconds to minutes