CHEM26/28 Exam 3 Study Guide

Page 1

Simple Sugars (Monosaccharides)

  • Empirical formula: CH2O

  • Aldose: sugars with an aldehyde group at one end of the molecule

  • Ketose: sugars with a ketone group located at one end of the molecule

  • Enantiomers/stereoisomers: non-superimposable mirror images.

  • Fischer Projection:

    1. all carbons in a vertical line

    2. Most oxidized carbon is at the top (carbonyl carbon)

Page 2

Monosaccharide Chirality

  • Chiral Carbon:

    1. all single bonds

    2. that are attached to four different groups

  • The Chiral carbon: furthest from the most oxidized end in a Fischer Projection.

  • D-stereoisomer: OH points right

  • L-stereoisomer: OH points left

  • Haworth Projection: 5-carbon and 6-carbon Fischer projections can cyclize

  • what does Hemiacetal linkage (C-O-C-O-H) do: allows ring to reopen/close between cyclic and linear form

  • Anomers: Alpha (hydroxyl down) and Beta (hydroxyl up) forms

  • cyclic monosaccharides: 6-carbon ring; nutritional (glucose, galactose, fructose) and 5-carbon ring; structural (ribose, deoxyribose

Page 3

Complex Sugars (Disaccharides)

  • Glycosidic Bond (oxygen bridge): Converts hemiacetal/hemiketal to acetal/ketal, locking linkage.

  • Maltose: D-Glucose + D-Glucose via alpha(1-4) bond.

  • Lactose: D-Galactose + D-Glucose via Beta(1-4) bond.

  • Sucrose: D-Glucose + D-Fructose via alpha(1)-Beta(2) bond.

Page 4

Polysaccharides

  • Dietary Starch: Amylose (liner) and Amylopectin (minimal branching)

  • The body's method of glucose storage: glycogen (highly branched)

  • Structural polysaccharide in plants: Cellulose; Beta (1-4) bonding

Page 5

Chapter 17: Lipids and Functions

  • Roles of lipids: Energy source, cell-membrane structure, steroid hormones.

  • Saturated fatty acids: max amount of hydrogens

  • unsaturated fatty acids: double bond (C=C’s always cis).

  • Melting Point: Lower for unsaturated due to disruptive packing; more double bonds lower the melting point

  • Omega-3 (ω-3): first double bond appears on 3 carbon in on the methyl end

  • Omega-6 (ω-6): first double bond appears on 6 carbon in on the methyl end

Page 6

Derivatives of Unsaturated Fatty Acids

  • Types of Eicosanoids from Arachidonic Acid: Prostaglandins, Thromboxanes, Leukotrienes

  • Waxes: Long fatty acid traditional esters; examples include Beeswax and Carnauba Wax.

  • Glycerides: non-traditional esters formed form glycerol and fatty acids (mono-, di-, tri-); Neutral glycerides; used for energy storage and stored in adipose fat cells

Page 7

Charged Glycerides

  • charged glycerides: phosphoglycerides; structural precursor for building blocks of the cell membrane

  • Examples of charged glycerides: Phosphatidate, Phosphatidylethanolamine, Phosphatidylcholine, Phosphatidylserine.

  • Cell membrane fluidity controlled by:

    1. Ratio of unsaturated to saturated fatty acids.

    2. Cholesterol content.

Page 8

Sphingolipids

  • Sphingolipids: formed from sphingosine; component for nerve cell membranes.

  • Difference between other glycerides: Direct connection to 3-carbon and amide linkage instead of ester.

  • Steroids nucleus: 4 carbon rings connected together

  • squalene derived steriods: Cholesterol (found in cell membrane), Bile salts (helps form dietary fats in digestive tract, made in liver stored in galbladder), estrogen+testosterone (sex hormones)

Page 9

Chapter 18: Protein Structure and Function

  • D/L determination in amino acids: based on NH3+ orientation, Only L-amino acids are naturally occurring.

Page 10

Peptide Bonds and Protein Structure

  • Peptide bond: Amide linkage between amino acids, n-terminus to c-terminus

  • Primary Structure: Linear sequence of amino acids.

Page 11

Secondary and Tertiary Structures

  • Secondary Structures: alpha-helix and Beta-sheet, stabilized by hydrogen bonds between amide backbone

  • Tertiary Structure: globular proteins, only between sidechains Stabilized by:

    1. Hydrophobic interactions

    2. Hydrogen bonds

    3. Salt bridges

    4. Disulfide bonds.

Page 12

Quaternary Structure

  • Quaternary structure of protein: stabilized by same 4 forces as tertiary; multiple tertiary structure grouped together

Page 19: Enzymes

Enzyme Functions

  • Enzymes: biological catalysts, lowers activation energy to make reaction run quicker; doesn’t affect equillibrium

  • Oxidoreductases: (redox reactions)

  • Transferases: (functional group transfers)

  • Hydrolases: (hydrolysis: splits with water)

  • Lyases: (addition of water over C=C)

  • Isomerases: (functional group rearrangement creating constitutional isomer)

  • Ligases: (addition of substiuent).

  • Proteolytic enzymes: enzymes that split peptide (amide) bonds on the carbonyl side (right side) into small amino acids sections

  • Chymotrypsin: splits at aromatic amino acids (phe, tyr, trp)

  • Trypsin: Basic sidechains (arg, lys)

  • Elastase: small sidechains (gly, ala)

Page 14

Enzyme-Substrate Complex

  • Enzyme-Substrate complex: E+S, ES transition state: ES*; enzyme-product complex: EP, E+P

  • Transition state 1: substrate in active site can put stress on bond; leading to breakage

  • Transition state 2: two substrates in active sites can lead to bonding of substrate and enzyme

  • Transition state 3: Create a different catalytic pH "microenvironment" within the active site

  • Active Site: Area binding substrate.

  • Key and Lock model: enzyme=lock, substrate=key; they perfectly fit together naturally

  • Induced fit model: enzymes active site is flexible and changes it’s shape to fit substrate

  • Cofactors: used to help maintain the correct shape of enzyme active site active sites

  • examples of cofactors: metal ions and small organic molecules

  • Thiamine: cofactor for decarboxylation reactions

  • Niacin: cofactor carrier of hydrogen atoms

  • Riboflavin: cofactor carrier of hydride ions