The Chemistry of Life Chapter 2

Periodic Table of the Elements

Water  Water is polar = uneven distribution of charge Oxygen “pulls” on hydrogens’ electrons Oxygen “pulls” on hydrogens’ electrons Oxygen is more negative, hydrogens are more positive Oxygen is more negative, hydrogens are more positive

Hydrogen Bonding of Water  Polarity of water leads to hydrogen bonding between water molecules  Negative oxygens are attracted to positive hydrogens

Mixtures  Solution – a substance is evenly dissolved in a liquid Ex – salt water: salt is the solute, water is the solvent Ex – salt water: salt is the solute, water is the solvent Water is the strongest solvent known because it is polar Water is the strongest solvent known because it is polar Blood is a solution Blood is a solution solution/dissolve.jnlp solution/dissolve.jnlp

Mixtures  Suspension – a substance is distributed, not dissolved, in water Ex – blood contains cells which are suspended in plasma Ex – blood contains cells which are suspended in plasma

pH Scale (0-14)  Measures concentration of H + in solution H 2 O ↔ H + + OH - water ↔ hydrogen ion + hydroxide ion  More H + = lower pH = more acidic  More OH - = higher pH = more basic  When [H + ] = [OH - ], solution is neutral, pH = 7

pH Scale ↑ H+↑ H+ ↑ OH -

pH Scale  Acids produce H + when dissolved in water HCl (hydrochloric acid) stomach acid HCl (hydrochloric acid) stomach acid  Bases produce OH - when dissolved in water NaOH (sodium hydroxide) found in bleach NaOH (sodium hydroxide) found in bleach

Carbon  Carbon (C) can make four covalent bonds  Provides a variety of structurally different molecules  C forms the backbone of all biological molecules  Molecules that contain C called organic

Biological Molecules  All biological molecules are large molecules (macromolecules or polymers) composed of smaller molecules (monomers)  Four classes: Carbohydrates Carbohydrates Lipids Lipids Proteins Proteins Nucleic Acids Nucleic Acids

Carbohydrates  Carbo-: carbon-hydrate: water, H 2 O  Major energy source  Monosaccharides Single sugar Single sugar Ex – glucose, fructose Ex – glucose, fructose Monomers for larger carbohydrates Monomers for larger carbohydrates

Carbohydrates  Disaccharides Two sugars Two sugars Ex – Sucrose (table sugar), lactose (milk) Ex – Sucrose (table sugar), lactose (milk)

Polysaccharides  Many sugars chained together  Examples Animals store sugar as glycogen Plants store sugar as starch Plant cell walls made of cellulose

Lipids  Fats, oils, waxes and steroids  Stored energy reserves  Saturated fats – solid at room temp.  Unsaturated fats – liquid at room temp.

Proteins  Important in growth, repair and chemical reactions  Made of amino acids (monomers) 20 different aa in humans 20 different aa in humans aa joined by peptide bonds aa joined by peptide bonds  AKA – polypeptides (many amino acids) Amino acids Peptide bond

Proteins Amino acids

Nucleic Acids  DNA – deoxyribonucleic acid  RNA – ribonucleic acid  Most complex biological molecule  Control heredity  Polymer of nucleotides 5 nucleotides in humans 5 nucleotides in humans DNA

Chemical Reactions  A reaction occurs when chemical bonds are broken or formed  If the reaction releases energy, it will occur spontaneously  If the reaction requires energy, it needs an input of energy to occur Heat, stirring Heat, stirring Activation energy is the energy needed to start reaction Activation energy is the energy needed to start reaction

Cellular Reactions  Heat necessary to start reactions in cells would kill cells  Cells must lower activation energy

Enzymes  Proteins that lower the activation energy of reactions  Act as a catalyst  Are not changed or consumed by the reaction  Specific to each substrate (substance enzyme “helps” to react)

Enzymes  Lock and key hypothesis Active site on enzyme and substrate fit together like a lock and key Active site on enzyme and substrate fit together like a lock and key  Temperature and pH affect enzyme activity