All organisms are made up of chemical compounds composed of atoms bonded together. Atoms consist of protons, neutrons, and electrons. Elements differ in the number of protons, while isotopes of the same element differ in the number of neutrons. Chemical bonds, including covalent, ionic, and hydrogen bonds, form when atoms interact and share or transfer electrons. Key biological molecules include water, carbohydrates like glucose, lipids, proteins, nucleic acids like DNA and RNA, and ATP. These molecules are essential for life processes and are made through various chemical reactions in living things.

1. Chapter 2

2. Organisms are chemical machines
 All organisms consist of atoms
– Subatomic particles
 Electron (e-) – located in electron cloud
 Proton (p+) – located in the nucleus
 Neutron (no) – located in the nucleus
Oxygen atom (O)
Nucleus:
8 protons (+)
8 neutrons
outermost energy
level:
6 electrons (-)
inner energy level:
2 electrons (-)

4. – Differ in the number of protons in the
nucleus.
– Number of protons = Number of
electrons
 Elements are neutral on the periodic table
– Atomic Number = Number of protons
– Atomic Mass = Number of protons + Number
of neutrons
http://www.privatehand.com/flash/elements.html

5. Name Symbol # p+ # e- #no
Tin
25
N
15
12

6. Differ in the number of neutrons they
contain in the nucleus
– Example:
 Carbon 12 – 6p+, 6e-, 6no
 Carbon 13 – 6p+, 6e-, 7no
 Carbon 14 – 6p+, 6e-, 8no

7.  Chemical Bonding – Compounds are
made of joined atoms of two or more
different elements.
 Valence shell – outermost electron shell
– Atoms with a full valence shell are inert
(unreactive)
– Atoms without a full valence shell can form bonds
(reactive).

8. Name Symbol # p+ # e- #no
Oxygen
6
K
53
- Why do all isotopes of an element have the same chemical
properties? (Use your book to help you answer this)

9.  The first electron shell of every atom can
hold a maximum of 2 electrons.
 Each additional shell can hold a maximum
of 8 electrons.

10. 1. Fluorine
2. Boron
3. Sodium

11.  Covalent bonds – atoms share
electrons
– Ex: H2, O2, CO2
covalent bonds
Oxygen atom (O) Carbon atom (C) Oxygen atom (O)
Carbon dioxide (CO2 )

12.  Ionic Bonds – atoms gain or loose
electrons
– Atoms form ions
 + charge – cation
 - charge – anion
 Ex: NaCl

13.  Hydrogen Bonds – weak chemical
attraction between polar molecules
– Water is a polar molecule because the electrons
of O and H are shared unequally.

15. • 70% of your body is made of water.
• The remaining 30% is made up mostly of
organic compounds (Carbon-based
molecules).
– Carbon is a unique element because it forms four
covalent bonds and can form a lot of different
structures.

16. Many carbon-based molecules are made of
many small subunits bonded together.
– Monomers are the individual subunits.
– Polymers are made of many monomers.

17.  Key source of energy found in
most foods
 Fruits, vegetables, and grains
 Made up of single sugars called
monosaccharides.
 Glucose, fructose
 Disaccharides - two
monosaccharides are joined
 Sucrose (table sugar)
 Polysaccharides – chains of three
or more monosaccharides
 Starch, cellulose, glycogen

18. Polymer (starch)
Starch is a polymer
of glucose monomers
that often has a
branched structure.
Polymer (cellulose)
Cellulose is a
polymer of glucose
monomers that has a
straight, rigid
structure
monomer

19.  Nonpolar molecules not soluble in water
 Fats, phospholipids (make up the cell membrane),
steroids (cholesterol), waxes
 Saturated fatty acids
 Solid at room temperature
 Butter, lard, grease
 Unsaturated fatty acids
 Liquid at room temperature
 Olive oil, fish oil

21.  Formed by chains of linked amino acids
 Many functions including:
 Enzymes
 Structural (imbedded in the cell membrane)
 Antibodies

22.  Formed by chains of nucleotides
 Two types :
 DNA (deoxyribonucleic acid)
 Double strand of nucleotides
 Stores hereditary information
 RNA (ribonucleic acid)
 Single strand of nucleotides
 Plays a key role in making proteins
Nucleotide

24. Another important biological molecule
 ATP (adenosine triphosphate)
– Consists of a single nucleotide with 2 extra
phosphate groups.
– ATP stores energy temporarily.
– All cells require ATP to function.

25. Chemistry allows life to function!
Everything living things do is possible due
to chemical reactions
The chemistry of
breathing

26. Activation energy is the amount of energy
that needs to be put in to start a chemical
reaction.

27. Exothermic reactions release more energy
than they absorb.
– Excess energy is released by the reaction as
heat.

28. Endothermic reactions absorb more energy
than they release.
– Energy is absorbed by the reaction.

29. – Proteins that increases the speed of a
chemical reactions in cells
– Act as a catalyst (reduces the activation energy
needed in a reaction)

30.  Any factor that changes the shape of an
enzyme can affect the enzyme’s activity.
– An enzyme’s function depends on its structure.
– Denaturing (changing the structure) the protein by
changes in temperature or pH
– Example: pepsin