1. Unit 3: Biochemistry Intro
Review QUESTIONS!!

2. The Basics
Atom: smallest unit of matter that maintains ALL of the properties of an element
Proton, Neutron, Electron: (+), (0), (-)
Element: substance that cannot chemically be broken down any further. Consisting entirely of one type of atom (ex. Carbon, hydrogen, oxygen)
Compound: two or more elements combined
Matter: has mass and takes up space

3. The Specifics
Protons and Neutrons are located in the atomic nucleus together.
Electrons are found in the outer valence shells of the atom.
Atomic mass: the sum of the protons and neutrons in an atom.
Electrons are not counted as part of the atomic mass b/c they are 1/2000 of 1 amu.

4. In the HUMAN BODY 96% of the body is made up of 4 elements:
Oxygen, Carbon, Hydrogen, & Nitrogen
(Outerspace Cowboys Hide in Narnia)
The remaining 4 percent is composed of several important elements:
P, Ca, K, S, Na, Cl, Mg
Several trace elements
Can use the regular symbols on periodic table….see? This is why you make sure to review EVERY homework assignment!!

5. Elements in the Human Body
Oxygen – 65%
Carbon – 18.5%
Hydrogen – 9.5%
Nitrogen – 3.3%
All of these equal 96.3%. The other 4% are trace elements: Calcium (1.5), Phosphorous (1.0), Potassium (0.4), & others.
Water
Most abundant element in our body
Click for animation
Most abundant compound in our body

7. Reading the Periodic Table
Atomic number 25
Tells number of protons in the nucleus Mn
Atomic Weight
Mass in the nucleus

8. Subscript
A subscript is a small lowered number after a symbol for an element.
H2O– the 2 is lowered and considered
a subscript.
The 2 indicates how many atoms of the element are present in that compound.

9. Chemical Compounds
Compound: A substance formed by the chemical combination of 2 or more elements in definite proportions.
Examples: H2O (water)
NaCl (Salt)
C6 H12 O6 (Sugar)

10. Chemical Formula States how many atoms are in each molecule.
How many carbon atoms are in C6 H12 O6?
How many hydrogen atoms?
How many oxygen atoms?
Click for answers 6 12 6

11. Chemical Equations CO2 + H2O -------- C6 H12 O6 + O2 REACTANTS
Let’s say I give you a chemical equation like—
CO2 + H2O C6 H12 O6 + O2
What are the names of these compounds?
Could you tell me which side are the reactants and which side are the products?
REACTANTS
PRODUCTS
Carbon
dioxide
Water
Sugar/glucose
Oxygen
Click for answers
Click for answers

12. Which of the following is an element?
ReviewQuestion #1
Which of the following is an element?
Carbon dioxide
Methane
Oxygen
Water

13. How many atoms are in: NH3
ReviewQuestion #2
How many atoms are in: NH3 1 2 3 4

14. Which of the following are the reactants?
ReviewQuestion #3
Which of the following are the reactants?
CH4 + 2 O CO2 + 2 H2O
CH4 + 2 O2
CO2 + 2 H2O
CH4 + 2 H2O
None of the above

15. Isotopes
All atoms of the same element contain the same number of protons
**Some atoms have a greater number of neutrons and therefore have a greater atomic weight– these are isotopes**
Most common isotope = carbon
Carbon 12, Carbon 13, and Carbon 14
All have 6 protons, but different number of neutrons

16. Covalent Bonds
Occurs when electrons are shared between two or more elements
When 1 electron is shared, a single covalent bond is formed
When 2 electrons are shared between elements, a double covalent bond is formed.
Make up abbreviations or use well-known ones such as “e-” for electrons, or “p+” for protons, etc

17. Compounds and Molecules
Molecules are formed between 2 atoms of the same element
O2 or H2
Compounds are formed between two or more elements
H2O

18. Electronegativity Defined as the attraction for a covalent bond
Non-polar covalent bonds are formed between elements that have the same electronegativity
Polar covalent bonds are formed when one atom in the bond has a higher electronegativity.
In other words when they have different electronegativities.

19. Ionic bonds
Typically form when an electron is pulled away from an element by another element
Cation- positive charged atom
Anion- negative charged atom
Ionic bonds are very dependent on the environment to form and stay together
Temperature, humidity, exposure to other elements

20. Weaker Interactions Other bonds exist in chemical interactions H bonds
All very influential in biological chemistry
Influences shape, structure, and formation of specific molecules (proteins)
All very influential not necessary to write down!!

21. Special Properties of H2O

22. Special Properties of Water
1) Cohesion: The H’s in water create H bonds
Creating relatively strong bonds between H2O molecules
2) High Specific Heat: takes a lot of energy to heat 1 gram of water 1 degree Celsius.
3) Expands when frozen
4) Excellent solvent (it is often referred to as the “Solvent of life.”)
Notice the title on notes and handout….what is different? Water is abbrev as h2o!! Notice the same for item 2!

23. Acids, Bases and the pH scale
The pH scale measures the concentration of H+ ions (how acidic something is)
Ranges from 0-14
At 7: H+ ions and OH- ions are equal so it is neutral
0-7: acidic, has more H+ ions
7-14: basic, has more OH- ions

24. ACIDS: release H+ when mixed with water
Sour, corrosive
Ex: HCl, H2SO4
Always have H at front of formula
BASES: release OH- when mixed with water
Bitter, slippery, usually in cleaners
NaOH, CaOH
Always have OH at end of formula

25. What is a buffer?
Buffers are weak acids or bases that react with strong acids and bases to prevent sharp changes in pH
Helps to neutralize
Help to control pH in blood, digestive tract, etc. to maintain homeostasis