Nucleic Acids DNA & RNA

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

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

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”

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”

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

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

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

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

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.

Properties of Water

Polar covalent bond – unequal sharing of electrons 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?

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

Water is the solvent of Life! Properties of Water Universal Solvent 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

Cohesion, Adhesion and Surface Tension Properties of Water Cohesion, Adhesion and Surface Tension 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

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

Properties of Water High Heat Capacity 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

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

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

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-

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

Acids and Bases

Making Biological Molecules and H2O Condensation Reaction H2O Hydrolysis Reaction