1. Biology 102 Lecture 4: Biological Molecules

2. Lecture outline 1. Organic molecules: Overview 2. Carbohydrates Functions Functions Structure Structure 3. Lipids

3. 1. Living organisms are composed of organic molecules Organic: Have a carbon “skeleton” Organic: Have a carbon “skeleton”  Carbon-carbon bonds  Each C atom can form as many as 4 bonds with other atoms  What other molecule is similar? Functional groups Functional groups  Specific arrangements of atoms that give each type of organic molecule their unique characteristics

4. All organisms are composed of similar organic molecules All organisms are composed of similar organic molecules  Carbohydrates  Lipids  Proteins  Nucleic acids Complex biological molecules (polymers) are synthesized from more simple molecules (monomers) Complex biological molecules (polymers) are synthesized from more simple molecules (monomers)  So, monomers are basically subunits of polymers.

5. Biological molecules are joined together by removing water: Dehydration synthesis Biological molecules are joined together by removing water: Dehydration synthesis Biological molecules are split apart by adding water: Hydrolysis Biological molecules are split apart by adding water: Hydrolysis  “hydro”=water, “lysis”=to cut Audesirk, p. 39

6. 2. Carbohydrates Key functions: Key functions:  Serve as a source of energy  Energy is “stored” within the bonds of all organic molecules, but carbohydrates are the most easily broken down to release energy  Starch, glycogen and glucose are all examples of carbohydrates that provide energy  Provide structure  Cellulose forms the cell walls of plants  Chitin forms the cell walls of fungi and the exoskeleton of arthropods (insects, crabs, etc…)

7. Structure of carbohydrate monomers Composition Composition  Contain Carbon, Hydrogen and Oxygen at ratios of 1:2:1  So, literally is Carbon plus water! Monosaccharides: sugar monomer, or “single sugar” Monosaccharides: sugar monomer, or “single sugar” When dissolved in water, usually forms a ring When dissolved in water, usually forms a ring  Here, ring is 5 carbons and one o the oxgyens Carbohydrates are polar Carbohydrates are polar  Where are the negative and positive charges? C 6 H 12 O 6

8. Several other monosaccharides with slightly different structures from glucose Fructose: sugar found in corn syrup and orange juice Fructose: sugar found in corn syrup and orange juice Galactose: sugar found in milk Galactose: sugar found in milk Ribose: sugar that forms part of RNA backbone Ribose: sugar that forms part of RNA backbone Deoxyribose: sugar that forms part of DNA backbone Deoxyribose: sugar that forms part of DNA backbone

9. Carbohydrate polymers Disaccharides: “di” means “two” Disaccharides: “di” means “two”  Two monosaccharides linked by dehydration synthesis  Note how an “H” of one monosaccharide combines with the “OH” of the other. Audesirk, Fig. 3-1

10. Polysaccharides are chains of monosaccharides Starch: energy storage Starch: energy storage  Enzyme in our saliva breaks down starch into sugar monomers Cellulose: structure Cellulose: structure  Forms plant cell walls  We cannot break down cellulose, so it passes undigested through us Chitin: structure Chitin: structure  Cell walls of fungi  Contains nitrogen atoms!

11. 3. Lipids Key functions Key functions  Energy storage molecules (i.e. fat); long-term  Fats and oils have over 2X the amount of energy for a given unit of weight compared to carbohydrates: 9.3 Calories/g compared to 4.1 Calories/g 9.3 Calories/g compared to 4.1 Calories/g  Waterproof coverings on plants and animals  Essential components of cell membranes  Hormones (i.e. testosterone and estrogen) Contain large non-polar regions Contain large non-polar regions  Specifically, the long hydrocarbon chains are non- polar

12. Oils and fats (triglycerides) Contain only Carbon, Hydrogen and Oxygen (just like carbohydrates!) Contain only Carbon, Hydrogen and Oxygen (just like carbohydrates!) Formed when three fatty acid subunits join to a single glycerol molecule Formed when three fatty acid subunits join to a single glycerol molecule  Synthesized with a dehydration synthesis reaction

13. The difference between oils and fats Fats: solid at room temperature Fats: solid at room temperature  They are “saturated” with Hydrogens: NO DOUBLE BONDS BETWEEN CARBONS  Resulting hydrocarbon chain is straight  Allows chains to fit together in solid clumps -C-C-C-C-C-C-H H H H

14. The difference between oils and fats (cont.) Oils: liquid at room temperature Oils: liquid at room temperature  They are “unsaturated” : HAVE SOME BONDS BETWEEN CARBONS  Resulting hydrocarbon chain is kinked  Do not fit together as well, and so remain fluid -C-C=C-C-C-C-H H H H H H Note the double bond and lower number of Hydrogens: “unsaturated”

15. Phospholipids Key component of membranes, including the plasma (cell) membrane Key component of membranes, including the plasma (cell) membrane  Phosphate-containing head region (polar!)  Note where the charges would be…  Two fatty acid tails (non-polar)  Why not polar?

16. Steroids Composed of four rings of carbon Composed of four rings of carbon Various functional groups protrude from the rings Various functional groups protrude from the rings Cholesterol : Key component of membranes Used to synthesize other steroids Testosterone and estradiol Sex hormones Note similarity in structure