1. Welcome to Honors Biology!!
**This Power Point Presentation can be found on my eBoard**

2. 2 Approaches to Studying Science
Reductionist Approach
Based on the idea that a whole can best be understood by studying its parts
Example: a scientist studies a tree’s leaves to better understand the way the tree functions
Holistic Approach
Studying the functioning whole, not the parts
Example: a scientist studies the entire tree to understand how it functions

3. Atoms & Molecules Matter – Anything that occupies space and has mass
Mass – How much space something takes up (measured in grams)
Weight – The measure of gravitational pull on an object (measured in Newtons)
People often confuse these two terms!

4. Atoms & Molecules
Where can you find atoms?

5. Atoms & Molecules
The Periodic Table of Elements

6. Atoms & Molecules

7. Atoms & Molecules
11 Naturally Occurring Elements in Humans (make up 96% of total)
Oxygen 8
Carbon 6
Hydrogen 1
Nitrogen 7
Calcium 20
Phosphorus 15
Potassium 19
Sulfur 6
Sodium 11
Chlorine 17
Magnesium 12

8. Atoms & Molecules Trace Elements in Humans (make up 4% of total)
Essential to at least some organisms but only in minute quantities
Examples: Boron, Chromium, Cobalt, Copper, Fluorine

9. Atoms & Molecules
Protons: Positively charged particles found in the nucleus of an atom
Neutrons: Neutrally charged particles found in the nucleus of an atom
Electrons: Negatively charged particles found on in regions away from the nucleus

10. Atoms & Molecules
Atomic Number: The number of protons in atoms of a certain element
Atomic Weight: The mass of an atom (usually given as a decimal number)
Mass Number: The sum of the protons and neutrons in an atom

11. Atoms & Molecules

12. Atoms & Molecules Outermost electrons = “Valence Electrons”
Most energetic electrons because they are far away from the “pull” of the nucleus
These are the electrons that will cause a reaction
Germanium has 4 valence electrons.

13. Atoms & Molecules
Isotope – A form of an element that has a different number of neutrons than usual.
Carbon -12 has 6 protons and 6 neutrons
Carbon-13 has 6 protons and 7 neutrons
Carbon -14 has 6 protons and 8 neutrons

14. Atoms & Molecules

15. Atoms & Molecules
Radioactive isotope – isotope in which the nucleus spontaneously will decay, giving off particles and energy
Can pose serious risks to living organisms
However, can be useful in biological research and medicine (See section 2.5 of text)

16. Atoms & Molecules Three types of chemical bonds
Covalent (Strongest) – Occurs when atoms come together and share electrons in the outer shells in order to satisfy the Octet Rule
Ionic (Second Strongest) – Occurs when 1 atom transfers valence electrons to another atom in order to satisfy the Octet Rule
Hydrogen Bond (Weakest) – Occurs when water molecules act like magnets and attract each other

17. Atoms & Molecules
The Octet Rule: A general rule of thumb that states that any atom wants to have 2 electrons in its first ring and 8 electrons in any subsequent rings.
One of these atoms satisfies Octet and one does not. Can you figure it out?

18. Atoms & Molecules
Molecules – must be atoms of the same or different elements covalently bonded together.

19. Atoms & Molecules
Compounds - must be atoms of different elements either covalently or ionically bonded together.

20. Atoms & Molecules
Hydrogen Bonding - Occurs mostly among water molecules

21. The Properties of Water
Water is polar
The atom of oxygen is slightly negative (δ-) and the atoms of hydrogen are slightly positive (δ+)

22. The Properties of Water
POLAR vs. NONPOLAR
Water and other charged molecules are POLAR
NONPOLAR = no positive or negative charges on the molecule
Example: oils and fats
This is why oil and water do not mix. POLAR likes POLAR and NONPOLAR like NONPOLAR

23. The Properties of Water
Water can hydrogen bond

24. The Properties of Water
Because of the hydrogen bonding, water is cohesive and has surface tension.

25. The Properties of Water
Water’s hydrogen bonds moderate temperature
Water can resist temperature change
Temperature is the average speed of the molecules in matter (such as water)

26. The Properties of Water
Water is a universal solvent
Solvent = The dissolving agent in a solution
Solution = Solvent + Solute
Solute = Substance being dissolved

27. The Properties of Water
Water has capillary action
It can rise in a small tube against gravity due to cohesion and adhesion

28. The Properties of Water
Water can break down into an acid or a base
H2O  H+ + OH-
H+ is hydronium ion = acid
OH- is hydroxide ion = base
Acids are solutions that have a pH below 7
Bases are solutions that have a pH above 7

29. The Properties of Water
List some well-known acids and bases (p.27 of text)

30. The Properties of Water
Buffers
Solutions that resist a change in pH by accepting H+ ions when they are in excess and donating H+ ions when they are depleted
Your own blood is buffered by carbonic acid

31. Rearrangement of Atoms
Chemical Reaction for Photosynthesis
Chemical Reaction for Cell Respiration