1. Journal Response
Based on what you already know answer the following questions:
What is an element?
What is an atom?
Write as much information down as you can think of.

2. Chapter 6: the Chemistry of Life

3. 6.1 Atoms and their Interactions
Elements
A substance that can’t be broken down into simpler chemical substances
Natural elements in living things
Of the 90 naturally occurring elements, only 25 are essential to living organisms
Carbon, hydrogen, oxygen, and nitrogen make up more than 96% of the mass of a human

4. Trace elements Some elements are present in very small amounts Iron
Magnesium

5. Atoms: the Building Blocks of Elements
Atom = the smallest particle of an element that has the characteristics of that element
The structure of an atom
All atoms have the same general arrangement
The center of an atom is called the nucleus
Protons: positive charge
Neutrons: no charge
Cloud around the nucleus
Electrons: negative charge

6. Electron energy levels
Electrons travel around the nucleus in certain regions known as energy levels
Each energy level has a limited capacity for electrons
Atoms contain equal numbers of electrons and protons
No net charge

7. Isotopes of an Element
Atoms of an element that have different number of neutrons in the nucleus
Scientists refer to isotopes by giving the combined total of protons and neutrons in the nucleus

8. Quiz Name one of the four elements that make up 96% of human mass.
What is the charge and location of an electron?
Why do atoms have no net charge?
Atoms of an element that have different number of neutrons are called ___?
What is an atom?

9. Compounds and Bonding
A compound is a substance that is composed of atoms of two or more different elements that are chemically combined

10. How covalent bonds form
Atoms combine to become stable
Are stable when the outermost electron energy level is full
When two atom share electrons the force that hold them together is called a covalent bond

11. Most compounds in organisms have covalent bonds
Sugars
Fats
Proteins
Water
A molecule is a group of atoms held together by covalent bonds and having no overall charge

12. How ionic bonds form
An atom that gains or loses electrons has an electrical charge and is called an ion
Ion = charged particle
The attractive force between two ions of opposite charge is known as an ionic bond

13. Chemical Reactions
When chemical reactions occur, bonds between atoms are formed or broken,
causing substances to combine and recombine as different molecules
All of the chemical reactions that occur within an organism are referred to as that organism’s metabolism
Reactions break down and build molecules that are important for the functioning of organisms

14. Writing chemical equations
Substances that undergo chemical reactions are called reactants
Substances formed by chemical reactions are called products
The number before each chemical formula indicates the number of molecules of each substance
The subscript number in a formula indicate the number of atoms of each element in a molecule of the substance
Atoms are neither created nor destroyed in chemical reactions

15. Mixtures and Solutions
When elements combine to form a compound, the elements no longer have their original properties
A mixture is a combination of substances in which the individual components retain their own properties
Do not combine chemically

16. A solution is a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent)
In organisms, many vital substances, such as sugars and mineral ions, are dissolved in water
The more solute that is dissolved in a given amount of solvent, the greater the solution’s concentration (strength)
Organisms can’t live unless the concentration of dissolved substances stays within a specific range

17. Acids and Bases
The pH is a measure of how acidic or basic a solution is
A scale with values ranging from 0 to 14 is used to measure pH

18. Substances with a pH below 7 are acidic
An acid is any substance that forms hydrogen ions (H+) in water
Ex: Hydrochloric acid, lemon

19. Substances with a pH above 7 are basic
A base is any substance that forms hydroxide ions (OH-) in water
Ex: ammonia, eggs, drain cleaner

20. 6.2 Water and Diffusion Water and Its Importance
Water is perhaps the most important compound in living organisms

21. Water is polar
Sometimes when atoms form covalent bonds, they do not share the electrons equally
In a water molecule, the shared electrons are attracted more strongly by the oxygen atom than by the hydrogen atoms
Polar molecule = a molecule with an unequal distribution of charge
Has a positive end and a negative end
Ex: water

22. Because of its polarity, water is able to creep up thin tubes
Hydrogen bond = attraction of opposite charges between hydrogen and oxygen that forms a bond
Because of its polarity, water is able to creep up thin tubes
Plants use this: capillary action

23. Water resists temperature changes
Water requires more heat to increase its temperature than do most other common substances
Water is like an insulator that helps maintain a steady environment when conditions may fluctuate

24. Water expands when it freezes
One of the few substances that expands when it freezes
Ice is less dense than liquid water

25. Diffusion All objects in motion have kinetic energy
Moving particles move in a straight line until it collides with another particle and both particles rebound.
Particles of matter are in constant motion, colliding with each other.

26. Early observations: Brownian motion
Robert Brown used a microscope to observe pollen grains suspended in water
Noticed that the grains moved constantly in little jerks
This motion is called Brownian motion
The random motion of molecules and the resulting collisions

27. The process of diffusion
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration
Results because of the random movement of particles
A slow process because it relies on the random molecular motion of atoms

28. Three key factors affect the rate of diffusion
Concentration = primary controlling factor
The more concentrated the substances, the more rapidly diffusion occurs
Temperature
Increase in temperature causes more rapid movement and therefore speeds up diffusion
Pressure
Increasing pressure will accelerate molecular movement and therefore diffusion as well

29. The results of diffusion
Diffusion will occur until the substance becomes equally distributed
After this point the atoms continue to move randomly and collide with one another, but no further change in concentration will occur
Dynamic equilibrium = condition of continuous movement but no overall concentration change

30. Diffusion in living systems
Most substances in and around a cell are in water solutions where ions and molecules of the solute are distributed evenly
The difference in concentration of a substance across space is called a concentration gradient
If no other processes interfere diffusion will continue until there is no concentration gradient and dynamic equilibrium occurs

31. 6.3 Life Substances Role of Carbon in Organisms
A carbon atom has four electrons available for bonding
Can form single, double, or triple bonds based on the number of electrons that are being shared
When carbon atoms bond to each other they can form straight chains, branched chains or rings
Compounds that have the same simple formula but different three-dimensional structures are called isomers

32. Molecular chains
Some carbon compounds contain just one or two carbon atoms, whereas others contain tends, hundreds, or even thousands of carbon atoms
Large molecules are called macromolecules
A polymer is a large molecule formed when many smaller molecules bond together
Condensation is the chemical reaction by which polymers are formed
A water molecule is removed
Hydrolysis is a method by which polymers can be broken apart
A water molecule is added

33. The structure of carbohydrates
A carbohydrate is an organic compound composed of carbon, hydrogen, and oxygen with a ratio of about two hydrogen atoms and one oxygen atom for every carbon atom
The simplest type of carbohydrate is a simple sugar called a monosaccharide
Ex: glucose, fructose

34. The largest carbohydrate molecules are polysaccharides
Starch consists of highly branched chains of glucose units
Used for food storage by plants
Cellulose is another glucose polymer
Forms the cell walls of plants

35. The structure of lipids
Lipids are organic compounds that have a large proportion of C-H bonds and less oxygen than carbohydrates
Commonly called fats and oils
They are insoluble in water
Molecules are nonpolar

36. The most common type of lipid consists of three fatty acids bound to a molecule of glycerol.
Saturated fatty acid: contains only single bonds
Cannot bond with any more hydrogen atoms
Unsaturated fatty acid: contains single, double, and possibly triple bonds
Can bind with more hydrogen atoms

37. The structure of proteins
Proteins are essential to all life
Provide structure for tissues and organs and carry out metabolism
A protein is a large, complex polymer compound of carbon, hydrogen, oxygen, nitrogen, and usually sulfur

38. The basic building blocks of proteins are called amino acids
20 common amino acids
The covalent bond formed between the amino acids is called a peptide bond
The number and order of amino acids in protein chains determine the kind of protein
An enzyme is a protein that changes the rate of a chemical reaction
Increase the speed of reactions

39. The structure of nucleic acids
A nucleic acid is a complex macromolecule that stores cellular information in the form of a code
Made of smaller subunits called nucleotides
Consist of carbon, hydrogen, oxygen, nitrogen, and phosphorus atoms arranged in three groups;
Base
Simple sugar
Phosphate group

40. RNA (ribonucleic acid) forms a copy of DNA
DNA (deoxyribnucleic acid) is the master copy of an organism’s information code
Determines how an organisms looks and acts
RNA (ribonucleic acid) forms a copy of DNA