Biology Chapter 2: Chemistry of Life

Matter Anything that takes up space and has mass Made up of particles called atoms

Atom Smallest unit of matter that cannot be broken down by chemical means Made up of protons (positive charge), neutrons (no charge), electrons (negative charge) Equal number of protons and electrons (balance each other out) Combine by sharing electrons Electrons can be anywhere in cloud but are usually hang out near nucleus

Element Substance made up of only 1 kind of atom Periodic table made up of elements Each element represented by a symbol Example: copper wire (made up of only copper therefore it is an element)

Compound Substance made of 2 or more different elements bonded together. Represented by a chemical formula such as HCl, NaOH, CO 2 Chemical formula does not change Example: water ( made up of hydrogen and oxygen)

Atomic Number Tells how many electrons that atom has # electrons = # protons

Atomic Mass/Weight equals the # protons + # neutrons # neutrons = atom weight – atomic number

Bonds Covalent Hydrogen Ionic

Covalent 2 atoms share electrons between them Molecule is a group of atoms held together by covalent bonds; no electrical charge Examples: H 2 O, CO, H 2, O 2

Hydrogen Special bond that holds H more strongly to another atom Can be polar (unequal distribution of electrical charge) or nonpolar (equal distribution of electrical charge) Example: bond between 2 water molecules Weak bond

Ionic Atom that gains (-) or loses (+) an electron (e- ) called an ion Atoms like to have stable outer electron level thus some ions will accept or give up an electron to become more stable Ions of opposite charge are attracted to each other and form ionic bonds. Ionic compound Na+ + Cl-  NaCl

Water 70% of body made up of H 2 O 2/3 of molecules in body are H 2 O molecules Cells are made of H 2 O and surrounded by H 2 O

Properties of Water Stores heat – heats more slowly & retains heat longer than many other substances Bonds to itself & other substances –Attraction between H 2 O molecules forms thin film at surface of water to prevent it from stretching or breaking (known as surface tension) –H 2 O drops form on plants because of cohesion (attraction between Substances of same kind) –Adhesion is attraction between different substances

Water Dissolves Many Substances Solution is mixture when 1 or more substances are evenly distributed in another substance (usually H 2 O) Solute = what is dissolved Solvent = does the dissolving (liquid) Sugars & salt need to “dissolve” or break up before they can be distributed to your cells

Acids & Bases H 2 O molecules break forming hydrogen ion (H+ ) and a hydroxide ion (OH- ) H 2 O  H+ + OH- Acids are compounds that form H+ when dissolved in water Bases are compounds that reduces the amount H+ in a solution pH scale measures concentration of hydrogen ions in a solution (range from 0 to 14) Pure water has pH value of 7.0 (neutral) Acidic solutions have pH below 7.0 Basic solutions have pH above 7.0

Organic vs. Inorganic Organic contain CARBON atoms (typically bonded to hydrogen, oxygen and other carbon atoms) Inorganic compounds contain elements other than carbon

4 Types of Organic Compounds Carbohydrates Lipids Proteins Nucleic Acids

Carbohydrates –Made of C, H, O (proportion 1:2:1) –Source of energy – found in most food monosaccharides or simple sugars (glucose, fructose) disaccharides (sucrose = glucose + fructose) polysaccharides (starch, cellulose) –Polysaccharides act as warehouse for energy contained in sugars –Chains of molecules put together

Lipids –Nonpolar, not soluble (dissolve) in water –Includes fats, waxes, steroids (cholesterol), and phospholipids (cell membrane) –Fats store energy (more than carbs) –Saturated fats – butter, lard, grease from meat; room temp. –Unsaturated fats – olive oil, some fish oils; room temp. –Trans fatty – –Cholesterol – not all is bad, body needs some to make lipid based molecules like steroid hormones

Proteins –Chain of amino acids linked together –20 diff. amino acids make up all proteins in your body –Large molecules that fold up into diff. shapes –Some proteins called enzymes promote chemical reactions –Collagen – most abundant protein in body; found in skin, ligaments, tendons –Other proteins like antibiotics – fight infection –Protein called hemoglobin carries O2 from lungs to body tissues

Nucleic Acids –Long chain of smaller molecules called nucleotides (three parts: sugar, base, phosphate group) –2 kinds of nucleic acids – DNA and RNA –DNA – deoxyribonucleic acid; two strands spiraled around each other (double helix); stores heredity info. –RNA – ribonucleic acid; single strand; makes proteins

ATP –Adenosine triphosphate –Main energy currency of cells –Food gets broken down and energy gets stored as ATP –Cells use ATP (energy) to function

Energy All organisms need it Has ability to move or change matter Can be stored or released by chemical reactions Cells consume fuel (food) because they need energy to function Help organisms maintain homeostasis

Chemical Reactions Enzymes increase speed of a reaction (most are proteins & end in “ase”) Need a certain amount of energy to get a reaction going this is called activation energy (ex. Riding a bike uphill) Think of activation energy as the chemical “push” to start it Catalyst speeds up reactions by lowering the amount of energy needed to get the reaction going (NOT ALL catalysts are enzymes)

Why Do We Need Enzymes? Reactions in body body temp – most would proceed too slowly to maintain life Examples include amylase in saliva (starch), pepsin in stomach (protein), tripson in small intestine

How Enzymes Work Enzymes bring key molecules together Enzymes act only on specific substrates Substrate – substance the enzyme is going to act upon An enzyme’s shape determines what it does Active Site – folds in enzyme where the substrate will fit in Enzyme & substrate interact to reduce activation energy When reaction complete, substrate is released (products), & enzyme can be reused since it is not changed during the process

Factors that Affect Enzyme Activity Fever response to infection – kill bacteria High fever is dangerous it inactivates critical enzymes at high temps. Fever above 105 degrees F can be fatal Change in pH can cause enzyme to break - denatured