1. Chapter 2 Chemical Basis of Life Atoms and molecules
Types of molecular bonds
Acids/bases
Macromolecules

2. Levels of Organization
1-5

3. Atoms Atoms - composed of subatomic particles:
Proton – carries a single positive charge
Neutron – carries no electrical charge
Electron – carries a single negative charge
Neutron
(n0)
Proton
(p+)
Electron
(e–)
Nucleus
Central part of atom
Composed of protons and neutrons
Electrons move around the nucleus
Nucleus

4. Atoms Electrically neutral, positive protons equals negative electrons
Neutron
(n0)
Electrically neutral, positive protons equals negative electrons
Proton
(p+)
Electron
(e–)
Nucleus

5. Atoms Isotopes- vary in the number of neutrons
May be stable or unstable
Unstable isotopes emit atomic radiation (energy or pieces of themselves)

6. Clinical Applications Radioactive Isotopes
commonly used
iodine-131 for thyroid function
thallium-201 for heart function
gallium-67 and cobalt-60 for cancer
others assess kidney functions, measure hormone levels and bone density changes

7. Molecules Two or more atoms combine
Molecular formula tells you what’s in it
Ex: H2O, two hydrogen atoms and one oxygen atom

8. How do the two (or more) atoms bond together?
Based on the number of electrons in regions of space called electron shells
First shell= 2
Second = 8
Third = 8
Can have many more shells

9. Electron shells Lower shells are filled first
If the outermost shell is full, the atom is stable - - - + + + + - + + - -
Hydrogen (H)
Helium (He)
Lithium (Li)

10. Types of bonds
Ionic bonds: form when atom or molecules lose or gain electrons and form ions. Ions of opposite charges attract.
Covalent bonds: electrons are shared, these are strong bonds
Hydrogen Bonds: Hydrogen bonds form between molecules or portions of large molecules.

11. Ionic bonds
Formed when electrons are transferred from one atom to another
Ions
Cation
Anion

12. Covalent bond Formed when atoms share electrons H H H2 - - - + + + + -
Hydrogen atom +
Hydrogen atom
Hydrogen molecule

13. Covalent bond Electrons can spend more time in one atom than others
Creates a polar molecule
Slightly negative ends
Slightly positive ends

14. Hydrogen bonds
Weak attraction between positive end of one polar molecule and negative end of another polar molecule
Ex: water H O
Hydrogen bonds

15. Chemical reactions NaCl ’ Na+ + Cl- Reactant Products
Occur when chemical bonds form or break among atoms or molecules
NaCl ’ Na+ + Cl-
Reactant
Products

16. Acids and Bases Acids- dissociate to release hydrogen ions in water
Bases- release ions that can combine with hydrogen ions
HCl  H+ + Cl-
NaOH  Na+ + OH-

17. pH scale
How many hydrogen ions are in solution

18. Changes in pH and Buffers
Blood pH
Normal blood pH is 7.35 – 7.45
Alkalosis occurs when blood pH rises to 7.5 – 7.8
Acidosis occurs when blood pH drops to 7.0 – 7.3
Homeostatic mechanisms help regulate pH
Buffers are chemicals which act to resist pH changes
Human body has several buffer systems

19. Macromolecules Large molecules
Every living thing on Earth has the following macromolecules: Carbohydrates, Lipids, Proteins, Nucleic Acids

20. Carbohydrates Major source of energy
Simple sugars link to form large sugars
Glucose (monosaccharide)
Glucose
Fructose
Sucrose (disaccharide)
Cellulose (polysaccharide)

21. Lipids Fats, hormones, cell membrane
Store energy, hormone precursors, cellular membrane component

22. Proteins Involved in virtually all cell functions
Proteins have very complex shapes, which allows them to carry out specific functions
Our DNA codes for proteins in the flow of genetic information

23. Nucleic Acids Genetic information molecule (mainly DNA)
- encodes, transmits genetic information
Made up of nucleotides = phosphate, sugar, base
- bases = adenine (A), thymine (T), guanine (G), cytosine (C)