Chapter 5: Molecules of Life

Organic vs. Inorganic All compounds may be classified into two broad categories: organic compounds - carbon based molecules inorganic compounds - almost all are non-carbon based molecules

Carbon (C) Carbon has 4 electrons in outer shell. Carbon can form covalent bonds with as many as 4 other atoms (elements). Usually with C, H, O or N. Example: CH4(methane)

Carbon Bonding Carbon can also bond with other carbon atoms Forms three types of structures: Straight chains Branched chains Rings

Carbon bonding Carbon can share one, two or three electrons with another atom single bond - one electron shared double bond - two electrons shared triple bond - three electrons shared

Macromolecules Large organic molecules. Also called POLYMERS. Made up of smaller “building blocks” called MONOMERS.

How Are Macromolecules Formed?

Answer: Dehydration Synthesis Also called “condensation reaction” Forms polymers by combining monomers by “removing water”. HO H H2O HO H

How are Macromolecules separated or digested?

Answer: Hydrolysis Separates monomers by “adding water” HO H H2O HO H

Macromolecules FOUR MAIN CATEGORIES: 1) carbohydrates: fuel & building material 2) lipids: fats & oils 3) proteins: perform most cell functions 4) nucleic acids: information storage (Chap. 11) Made up of nucleotides DNA & RNA Forms the genetic code

Carbohydrates

Carbohydrates Carbohydrates are made of sugar molecules Sugars contain carbon, hydrogen, and oxygen in the following ratio: 1 carbon : 2 hydrogen : 1 oxygen

3 main types of carbohydrates: Monosaccharide: one sugar unit Ex: glucose, fructose, lactose Disaccharide: two sugar units Ex: Sucrose (glucose + fructose) Ex: Galactose (glucose + lactose) Polysaccharide: many sugar units; Ex: Starch: found in plants (bread, tomatoes) Ex: Glycogen: found in animal cells Ex: Cellulose: found in cell wall of plants

Carbohydrates Most carbohydrates are polar and hydrophilic Hydrophilic: attracted to water molecules Monosaccharides and disaccharides easily dissolve in water to form sugar solutions

Lipids

Lipids Lipids are not soluble in water. They are nonpolar and hydrophobic do not mix with water Lipids “store the most energy” Examples: Fats, oils Phospholipids Steroid hormones Triglycerides

Lipids Six functions of lipids: 1. Long term energy storage 2. Protection against heat loss (insulation) 3. Protection against physical shock 4. Protection against water loss 5. Chemical messengers (hormones) 6. Major component of membranes (phospholipids)

Simplest Fats Triglycerides: composed of 1 glycerol and 3 fatty acids. H H-C----O glycerol O C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3 = O C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3 = fatty acids O C-CH2-CH2-CH2-CH =CH-CH2-CH2-CH2-CH2-CH3 =

Fatty Acids There are two kinds of fatty acids: 1. Saturated fatty acids: no double bonds (bad) solid at room temperature, Ex: butter 2. Unsaturated fatty acids: at least 1 double bonds (good) liquid at room temperature, Ex: Fruits, olive oil O C-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH3 = saturated O C-CH2-CH2-CH2-CH =CH-CH2-CH2-CH2-CH2-CH3 = unsaturated

Steroids Classified as lipids  are hydrophobic Differ from fats in structure & function Some act as chemical signals or hormones  estrogen and testosterone

Proteins

Functions of Proteins Form structures—hair, fur, muscles Provide long-term nutrient storage Circulate and defend the body against microorganisms (antibodies) Act as chemical signals—hormones Help control chemical reactions in cells—enzymes

Protein Structure Proteins are polymers formed from monomers called amino acids. Amino acids bonded together by peptide bonds (polypeptides). There are 20 different kinds of amino acids. aa1 aa2 aa3 aa4 aa5 aa6 Peptide Bonds Amino Acids (aa)

Amino Acid Structure Three of central carbon’s partners are the same in all of the 20 different amino acids 1. hydrogen atom 2. carboxyl group 3. amino group

Amino Acid Structure Differences between one amino acid and another are due to the unique “R group” or side group that each one has Each “R group” is responsible for a different chemical property for each amino acid

Protein Shape Functional proteins consist of precisely twisted, coiled, and shaped polypeptides Proteins cannot function correctly if shape is altered Denaturation: loss of normal protein shape Unfavorable changes in temperature, pH, or other environmental conditions may cause proteins to become denatured

Enzymes are proteins that speed up specific reactions in cells

Activation Energy Activation energy: minimum energy required to start chemical reaction Catalysts: compounds that speed up chemical reactions Enzymes: proteins that act as catalysts for chemical reactions in organisms

How Enzymes Work ACTIVE SITE MODEL Substrate: specific reactant acted on by an enzyme Active site: specific region of the enzyme that the substrate fits into Substrate binds to enzyme’s active site where the substrate undergoes a change