The Chemical Basis of Animal Life Chapter 2

Chemistry The branch of science dealing with composition of substances and reactions among these substances. A knowledge of chemistry is essential for understanding the structure and function of animals because body functions involve chemical changes.

Matter Matter: is anything that occupies space and has mass. Solids – Liquids – Gases Matter has many properties. PHYSICAL different densities, melting points, boiling points, freezing points, color or smells. CHEMICAL what elements combine with each other in reactions. Matter has many properties. It can have PHYSICAL properties like different densities, melting points, boiling points, freezing points, color or smells. There are also CHEMICAL properties that define matter. Like what elements combine with each other in reactions. Matter can combine in the same ways, physically and chemically.

Matter Matter includes all solids, liquids and gases Matter is composed of elements which make up mass Currently, 92 naturally occurring elements ~ 15 found in most animals and 4 (C,H,O,N) account for ~ 97% of animal’s body weight A remaining ~ 3% are Ca, P, and K

Matter is composed of elements Elements: chemical substances that ordinary chemical reactions cannot break down into simpler units.

ATOMS Atoms atoms everywhere. Don't laugh, it's true. There are always atoms around unless you are inside of a vacuum. There are different types of atoms, one for each element. There are even different kinds of atoms for each element called IONS. You'll understand what we mean in a second. We also introduce you to what happens when atoms combine. There are millions of ways atoms bond and make billions of COMPOUNDS. Don't know where to start? Start with atomic STRUCTURE and learn what is inside of an atom.

Atoms Atoms are the smallest parts of an element that can enter into a chemical reaction.

Structure of Atoms Nucleus contains (+)protons and neutral neutrons Atoms are composed of nucleus and electron cloud Nucleus contains (+)protons and neutral neutrons Electron cloud contains (-) electrons

Atomic Number The atomic number is equal to the # of protons in an atom Oxygen At# = 8 Carbon At# = 6 Hydrogen At# = 1 Nitrogen At#= 7 Calcium At # = 20

Atomic Mass Atomic Mass = # of protons + # of neutrons Oxygen = At. Mass of 16 Carbon = 12 Hydrogen = 1 (has no neutrons) Nitrogen = 14 ISOTOPES: Same atom but has different atomic weight due to + or – neutrons Carbon 13 has 7 neutrons instead of 6 (stable does not break down RADIOISOTOPES Unstable isotopes. 14C release small particles and energy.

Electron Shells Electrons are arranged in energy shells Seven possible shells Each shell can only hold a certain # of electrons The nearest to the nucleus never has more than two. The 2nd and 3rd hold up to eight electrons.

Chemical Compounds in Living Things In varying combinations, the elements carbon, hydrogen, oxygen, and nitrogen make up practically all the chemical compounds in living things.

Compounds and Molecules Water is a compound H O 2

Compounds Compounds are composed of 2 or more elements chemically united in fixed portions. ie. Water has 2 Hydrogen atoms and 1 Oxygen atom

Molecules Compounds of atoms held together by covalent bonds Covalent Atoms share outer shell electrons with other atoms i.e. O2

Hydrogen Bonds Hydrogen gains a slightly positive charge as it is drawn toward another atom and leaves a proton behind. Hydrogen bond is weak

Ionic bonds Atoms gain or lose electrons in outer most shell creating a charge A charged atoms is called an ion

Acids, Bases, and Buffers Electrolytes conduct electricity in a solution Acid –releases hydrogen (H+) ions in water Base – releases hydroxide ions (OH-) in water

Acids, Bases, and Buffers pH – the measure of acidity or alkalinity of a substance Range from 0-14 0 = Strong ACID 14= Strong BASE 7 = neutral

The pH scale and pH values of various aqueous solutions Increasingly Acidic [H+] > [OH–] Increasingly Basic [H+] < [OH–] Neutral [H+] = [OH–] Oven cleaner 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH Scale Battery acid Digestive (stomach) juice, lemon juice Vinegar, beer, wine, cola Tomato juice Black coffee Rainwater Urine Pure water Human blood Seawater Milk of magnesia Household ammonia Household bleach Figure 3.8

Two types of compounds ORGANIC INORGANIC Those that contain carbon Those that do not contain carbon INORGANIC

Inorganic Compounds Primarily those that do not contain carbon. Exception is carbon dioxide Water and minerals are both inorganic Living things contain a great many inorganic compounds The compounds that make up bones and form salts are inorganic

Organic Compounds Organic compounds contain carbon

Why is carbon so special? Carbon is a unique element because of its remarkable ability to form covalent bonds that are strong and stable. Carbon has 4 electrons in its outer shell; thus, it must share 4 electrons by covalent bonding – either with single or double bonds. This allows carbon to form chains and rings

Carbon Atom Carbon has 4 electrons in outer shell - - - - - -

Hydrocarbons Are organic molecules that contain only carbon and hydrogen (most are in a linear arrangement) Form the framework of all organic molecules H H H H H H H H-C-C-C-C-C-C-C-H

Compounds of Life carbohydrates lipids proteins nucleic acids The four groups of organic compounds found in living things are : carbohydrates lipids proteins nucleic acids

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