acids

1. Nucleic Acids
DNA & RNA

2. What are they ?
The 4th type of biomolecule
The chemical link between
generations
The source of genetic
information in chromosomes

3. What do they do ?
Dictate amino-acid
sequence in proteins
Give information to
chromosomes, which is then
passed from parent to
offspring

4. What are they made of ?
 Simple units called nucleotides,
connected in long chains
 Nucleotides have 3 parts:
1- 5-Carbon sugar (pentose)
2- Nitrogen containing base
(made of C, H and N)
3- A phosphate group ( P )
 The P groups make the links that
unite the sugars (hence a “sugar-
phosphate backbone”

5. Two types of Nucleotides
(depending on the sugar they
contain)
1- Ribonucleic acids (RNA)
The pentose sugar is Ribose
(has a hydroxyl group in the 3rd
carbon---OH)
2- Deoxyribonucleic acids (DNA)
The pentose sugar is
Deoxyribose (has just an
hydrogen in the same place---
H) Deoxy = “minus oxygen”

6. DNA Nucleotides
Composition (3 parts):
1- Deoxyribose sugar (no O in 3rd
carbon)
2- Phosphate group
3- One of 4 types of bases (all
containing nitrogen):
- Adenine
- Thymine (Only in DNA)
- Cytosine
- Guanine

7. RNA Nucleotides
Composition ( 3 parts):
1- Ribose sugar (with O in 3rd
carbon)
2- Phosphate group
3- One of 4 types of bases (all
containing nitrogen):
- Adenine
- Uracyl (only in RNA)
- Cytosine
- Guanine

8. DNA vs RNA
 DNA
1- Deoxyribose sugar
2- Bases: Adenine, Thymine, Cytosine,
Guanine
3- Double-stranded helix arrangement
 RNA
1- Ribose sugar
2- Bases: Adenine, Uracyl, Cytosine,
Guanine
4- Single stranded

9. The Double Helix (DNA)
Structural model:
 Model proposed by Watson & Crick, 1953
 Two sugar-phosphate strands, next to each
other, but running in opposite directions.
 Specific Hydrogen bonds occur among bases
from one chain to the other:
A---T , C---G
Due to this specificity, a certain base on
one strand indicates a certain base in the
other.
 The 2 strands intertwine, forming a double-
helix that winds around a central axis

10. How DNA Works
1- DNA stores genetic information in
segments called genes
2- The DNA code is in Triplet Codons
(short sequences of 3 nucleotides
each)
3- Certain codons are translated by
the cell into certain Amino
acids.
4. Thus, the sequence of nucleotides in
DNA indicate a sequence of Amino
acids in a protein.

11. 11

12. Properties of Water
Covalent bonding
Polar covalent bond – unequal sharing of
electrons
A great example of a molecule with polar
covalent bonds is water. Why is water
considered polar?
What is a partial positive and partial
negative charge?

13. Properties of Water
Covalent bonding vs. Hydrogen bonding
Covalent Bond
Hydrogen Bond

14. Properties of Water
Water is the solvent of Life!
Solute – substance dissolved in a
solvent to form a solution
Solvent – fluid that dissolves solutes
Example: Ice Tea – water is the
solvent and tea and sugar the solutes
Universal Solvent

15. Properties of Water
cohesion = water attracted to other water
molecules because of polar properties
adhesion = water attracted to other materials
surface tension = water is pulled together creating
the smallest surface area possible
Cohesion, Adhesion and Surface Tension

16. Properties of Water
Capillary Action
Because water has both
adhesive and cohesive
properties, capillary action is
present.
Capillary Action = water’s adhesive property is the cause
of capillary action. Water is attracted to some other
material and then through cohesion, other water
molecules move too as a result of the original adhesion.
Ex: Think water in a straw
Ex: Water moves through trees this way

17. Properties of Water
In order to raise the temperature of
water, the average molecular speed
has to increase.
It takes much more energy to raise
the temperature of water compared to
other solvents because hydrogen
bonds hold the water molecules
together!
Water has a high heat capacity.
“The specific heat is the amount of
heat per unit mass required to raise
the temperature by one degree
Celsius.”
High Heat Capacity

18. Properties of Water
Density
Water is less dense as a solid! This is because the
hydrogen bonds are stable in ice – each molecule of
water is bound to four of its neighbors.
Solid – water molecules
are bonded together –
space between fixed
Liquid – water molecules
are constantly bonding
and rebonding – space is
always changing

19. Properties of Water
So, can you name all of the properties of water?
Adhesion
Cohesion
Capillary action
High surface tension
Holds heat to regulate temperature (High heat capacity)
Less dense as a solid than a liquid

20. Acids and Bases
Strength compared using pH scale
Ranges from 0 – 14
Logarithmic Scale (gets 10x bigger/smaller)
Acid – donates H+ when added to aqueous solutions
Ranges from pH 0-6.9
Base – breaks up into hydroxide (OH-) ions and
another compound when placed in an aqueous
solution
Ranges from pH 7.1 – 14
Distilled water is pH 7.0 or neutral. Why?
H2O H+ + OH-

22. Acids and Bases
Buffers – compounds used to maintain a
contant pH within a system
H2CO3 H+ + HCO3
-
Carbonic acid bicarbonate ion

23. Acids and Bases

24. Making Biological Molecules
Condensation Reaction
Hydrolysis Reaction
and H2O
H2O