Chemical Bonding 1. Covalent Bond - strong bond, formed by sharing of 2 or more electrons  Example: C 6 H 12 O 6 & any organic molecules 2. Ionic Bond – formed by the transfer of 1 or more electrons  Example: NaCl & MgCl 2  Cation – positive  Anion - negative

… 3. Hydrogen Bonding – weak bond formed by hydrogen w/i a molecule being attracted by oxygen & nitrogen w/i a molecule  Important in DNA and proteins

Macromolecules of Life Abundance in a cell:  Proteins (55%)  Nucleic acids (24%)  Lipids (9%)  Carbohydrates (5%)  Lipopolysacharides (3%)  Other (4%) = inorganics

Question: How Are Macromolecules Formed?

Answer: Dehydration Synthesis “condensation reaction”  Also called “condensation reaction” polymers monomers“removing water”  Forms polymers by combining monomers by “removing water”. HOH HH H2OH2O

Question: How are Macromolecules separated or digested?

Answer: Hydrolysis monomers“adding water”  Separates monomers by “adding water” HO HH H H2OH2O

Lipids  Any biological molecule that has low solubility in water & high solubility in nonpolar organic solvents  Hydrophobic; thus they are good barriers for aqueous environments  6 major groups:  Fatty acids  Tricylglycerols  Phopholipids  Glycolipids  Steroids  Terpenes

Lipids … Fatty Acids  Building blocks for most complex lipids  Long chains with a carboxylic acid at 1 end  Can be saturated or unsaturated  Saturated only single C-C bonds  Unsaturated has one or more C=C (double bond)  Oxidation gives huge amounts of chemical energy for a cell

Lipids … Triacylglycerols  A.K.A. triglycerides, fats, or oils  Have a 3 Carbon backbone (glycerol) that’s attached to 3 fatty acids  Function is to store energy, thermal insulation, and padding to an organism  Adipocytes (fat cells) contain almost nothing but triglycerides

Lipids … Phospholipids  Glycerol backbone with one of the fatty acids replaced by a polar phosphate group  Major component of membranes  Amphipathic

Lipids … Glycolipids  Phospholipid with one or more carbohydrates attached to glycerol rather than phosphate  Also amphipathic  Found in the membranes of myelinated cells of the nervous system

Lipids … Steroids & Terpenes SteroidsTerpenes  4-ringed structure  Includes hormones, vitamin D, & cholesterol  Includes vitamin A (important for vision)

 Lipids are transported by lipoproteins in the blood  Classified by their density: (the greater the ratio of lipid to protein, the lower the density)  Very low density lipoproteins (VLDL)  Low density proteins (LDL) – ‘bad cholesterol’  High density lipoproteins (HDL) – ‘good cholesterol’

Proteins  Building block is amino acids linked together by a peptide bond  AKA polypeptides  Nearly all protein in all species are built from the same 20 amino acids  10 are essential (ingested rather than manufactured by body)  Side chains differ from amino acid to amino acid

Protein Structure Primary StructureSecondary Structure  Number and sequence of amino acids in a polypeptide  Single chain can twist into an α-helix or β-pleated sheets  Both are reinforced with H- bonds between amino acids

Protein Structure… Tertiary StructureQuaternary Structure  3-D shape formed when the peptide chain curls and folds  Created by 5 forces:  Covalent disulfide bonds b/w cysteine  Electrostatic ionic interactions (acidic & basic)  Hydrogen bond  Van der Waals forces  Hydrophobic side chains push away from water toward center

Protein Structure… Quaternary Structure  2 or more polypeptide chains bond together  Same 5 forces as tertiary

 A denatured protein has lost secondary, tertiary, and quaternary structure  Protein can sometimes form back when denaturing agent is removed  2 main functions of proteins:  Structural (cell wall)  Functional (enzymes)

 2 main types of proteins:  Globular (functional)  Enzymes  Hormones  Membrane pumps & channels  Membrane receptors  Intercellular and intracellular transport and storage  Osmotic regulators  Etc.  Structural – maintain and add strength to cells  Ex. Collagen

…  Central Dogma DNA → RNA → protein ↑ ↑ transcription translation Genotype Phenotype

Carbohydrates  AKA sugars or saccharides  Glucose accounts for 80% of carbs absorbed by humans  Liver converts most carbs to glucose  Glucose turned to ATP during cellular respiration  If cell has enough ATP, the glucose is turned to glycogen (only animals) or fat  Most cells absorb glucose via facilitated diffusion – insulin increases absorption rate  Plants form cellulose and starch from glucose

Carbohydrates …  Building blocks are simple sugars (monosaccharides)  glucose, ribose, etc  Cell wall constituents (peptidoglycan)  Cell recognition factors in membranes  lipopolysaccharides  Serves as high energy storage compounds (glycogen)  Serve as bacterial ‘food’ (chemoheterotrophs)

2 monosaccharides make a disaccharide

Monomer to disaccharide to polysaccharide

Nucleic Acids  Building blocks are nucleotides:  5-C Sugar, phosphate group, & nitrogen base  Nitogen bases: adenine, cytosine, guanine, thymine, uracil (a=t) & (c=g) & (a=u)  Nucleotides joined by phosphodiester bonds  Examples of nucleic acids include DNA, RNA, ATP, NADH, FADH 2  DNA is written 5’ to 3’

 Functions – information storage  RNA has multiple functions:  mRNA – RNA copy of DNA  rRNA – part of ribosome, helps to make proteins  tRNA – carries amino acids to ribosome

Pop Quiz 1. A molecule of DNA contains all of the following except: a) Deoxyribose sugars b) Polypeptide bonds c) Phophodiester bonds d) Nitrogenous bases 2. Which of the following is a carbohydrate polymer that is stored in plants and digestible by animals? a) Starch b) Glycogen c) Cellulose d) Glucose

…cont. 3. Excessive amounts of nitrogen are found in the urine of an individual who has experienced a period of extended fasting. This is most likely due to: a) Glycogenolysis of the liver b) The breakdown of body proteins c) Lipolysis in adipose tissue d) A tumor on the posterior pituitary causing excessive ADH secretion 4. Metabolism of carbohydrate and fat spare protein tissue. All of the following are true of fats except: a) Fats may be used in cell structure b) Fats may be used as hormones c) Fats are more efficient form of energy storage than proteins d) Fats are less efficient form of energy storage than proteins

… cont. 5. Which of the following is found in the RNA but not the DNA of a living cell? a) Thymine b) Double helix c) An additional hydroxyl group d) Hydrogen bonds

Answers 1. B 2. A 3. B 4. C 5. C