The Chemical Basis of Animal Life. Chapter 2

Transcription

1 The Chemical Basis of Animal Life Chapter 2

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.

3 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.

4 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

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

6 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.

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

8 Structure of Atoms Atoms are composed of nucleus and electron cloud

9 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

10 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. 14 C release small particles and energy.

11 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 2 nd and 3 rd hold up to eight electrons.

12 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.

13 Compounds and Molecules Water is a compound

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

15 Molecules Compounds of atoms held together by covalent bonds Covalent Atoms share outer shell electrons with other atoms i.e. O 2

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

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

18 Acids, Bases, and Buffers Electrolytes conduct electricity in a solution Acid releases hydrogen (H+) ions in water Base releases hydroxyl ions (oh-) in water

19 Acids, Bases, and Buffers ph the measure of acidity or alkalinity of a substance Range from 0-14

20 Two types of compounds Those that contain carbon Those that do not contain carbon

21 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

22 Organic Compounds Organic compounds contain carbon

23 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

24 Carbon Atom Carbon has 4 electrons in outer shell

25 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 H H H H H H H

26 Compounds of Life The four groups of organic compounds found in living things are :

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