Biochemical Reactions SBI4U1 Acids produces H+ ions in H2O
pH below 7 Sour taste, conducts electricity Increase [H+] or [H3O+] ions when dissolved in water HCl (aq) + H2O (l) H3O+ (aq) + Cl- (aq) Bases produces OH- ions in H2O (or accepts/ reacts with H+ ions) pH above 7
Bitter taste, conducts electricity Increase [OH-] when dissolved in water NaOH (s) Na+ (aq) + OH- (aq) Strong/Weak Acids and Bases Depends on the degree to which they dissolve into ions Strong acids/bases completely ionize in water (e.g. NaOH, HCl) 100%
HCl (aq) + H2O (l) H3O+ (aq) + Cl- (aq) 100% NaOH (s) Na+ (aq) + OH- (aq) 100% ionization Weak acids/bases only partially ionize in
water 1.3% CH3COOH (aq) + H2O (l) NH3 (aq) + H2O(l) 10% H3O+ (aq) + Cl - (aq) NH4 + (aq)
+ OH - (aq) Note: double arrow represents that reaction is reversible Acid-Base Buffers Cells are sensitive to pH levels Cell processes w/ proteins and enzymes (pH 7) Blood (pH 7.4, 0.4 increase can be fatal)
Acidosis: blood pH < 7.35 Alkalosis: blood pH >7.45 Blood pH can be affected by food Acidic fruits, wine, salad dressing Alkaline shrimp, tonic water Buffers Chemical systems with substances that
donate/remove H+ ions when pH changes Example: Carbonic acid-bicarbonate buffer H2O + CO2 H2CO3 HCO3- + H+ H2O + CO2
H2CO3 HCO3- + H+ If too acidic H + will react with HCO3- to produce H2CO3 Excess H+ are removed from the solution to avoid decrease in pH If too basic, H2CO3 will ionize to replace H+
H+ ions are added to avoid increase in pH Animation: http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/buffer12.swf Oxidation-Reduction Reactions Oxidation: loss of electrons (loses hydrogen or gains oxygen) Reduction: gain of electrons Redox Rxn: LEO the lion says GER LEO loss of electrons is oxidation
GER gain of electrons is reduction Examples: C3H8 LEO + 5O2 GER C6H12O6
LEO + 6O2 GER 3CO2 6CO2
+ H2O + 6H2O Sugars are oxidized to produce carbon dioxide and water in cellular respiration.
Condensation/Hydrolysis Rxns Condensation Rxn: formation of a covalent bond with the production of water Anabolic rxn (makes larger molecules) Hydrolysis Rxn: formation of a covalent bond with the addition of water Catabolic (breaks down into smaller molecules) Animation: http://www.uic.edu/classes/bios/bios100/lectures/polymer.htm
An H from one molecule combines with an OH from another. Water is released and the two molecules join. Water is
added. One H goes to one molecule and the OH to the other to break them apart. Carbohydrates Note: condensation rxn is also known as dehydration synthesis
Lipids Protein Nucleotide Purine: A and G Pyrimidine: C, T, U Enzymes
Activation Energy (EA): energy required for a rxn to take place Catalyst: speeds up the rate of a chemical rxn without being consumed Enzymes: protein catalysts that increase the rate of reaction by lowering the EA Enzymes typically end in ase Example: amylose
amylase + H2O maltose
There are many enzymes involved in digestion: peptase, lipase, maltase How Enzymes Work: Enzymes are made up of long chains of amino acids Enzymes attach to substrates in order to work Most enzymes have globular shapes with
active sites Where the substrate binds Enzyme-Substrate Complex: enzyme with a substrate that is bound to enzymes active site In this rxn, a dissacharide sucrose is broken down into glucose and fructose.
Since enzymes are protein, they can become denatured if the temperature or pH change Some enzymes require assistance from cofactors of coenzymes Coenzymes are organic molecules Cofactors are metal ions like iron or zinc Some substances can inhibit enzyme function:
Competitive Inhibitors: similar to substrate, bind to active site and block normal substrate Non-Competitive Inhibitors: do not compete with substrate, attach to different site, change the shape so substrate cannot bind Enzyme activity is controlled by:
1. Restricting the production of an enzyme 2. Inhibiting or stimulating enzymes activity by the use of allosteric sites Not the active site Other molecules can interact with/regulate enzyme activity If an activator binds = enzyme is functional If an inhibitor binds = enzyme is not functional Review Questions
Why are enzymes important in biological processes? Give an example. What is an enzyme-substrate complex? Differentiate b/t competitive and noncompetitive inhibition. Things You Should Know...
Redox rxns Acid/Base Buffers Condensation vs. Hydrolysis Rxn Role of enzymes Enzyme substrate complex Competitive vs. non-competitive inhibition
