The Molecular Building Blocks of Life

1. The Molecular Building Blocks of Life

2. Objectives • 3.2.1 – Distinguish between organic and inorganic compounds. • 3.2.2 – Recognize the physical differences between the macromolecules that are the building blocks of life. • 3.2.3 – State the uses for carbohydrates, lipids, nucleic acids, and proteins

3. The Importance of carbon Cells are 70-95% water, the remainder is mostly carbon-based compounds. • Proteins, DNA, carbohydrates, & lipids distinguish living matter from inorganic material; all are composed of carbon atoms bonded to each other & to atoms of other elements, including H, O, N, S, & P (percentages are quite uniform in all life). • oxygen (65 percent); • carbon (18 percent); • hydrogen (10 percent); • nitrogen (3 percent); • phosphorus (1 percent); and • sulfur (0.2 percent).

4. Organic chemistry Organic chemistry is the study of carbon compounds. • Produced not only in biological processes, they can also be synthesized by non-living reactions. • Organic compounds range from simple CH4(below),to complex molecules, like proteins & DNA (at right).

5. Organic chemistry Organic compounds contain carbon & hydrogen together! • CH4 – methane, C8H18 – octane, C6H12O6 – glucose • If a carbon compound is not accompanied by hydrogen, it is considered inorganic. • CO2 – inorganic (no H) • CCl4 – inorganic (no H) • CoCl2 – inorganic (no C) • CaHPO4 – inorganic (no C) • HCl – inorganic (no C) • Don’t be fooled!

6. Atomic carbon Carbon atoms are the most versatile building blocks of molecules. • With a total of 6 e-, a C atom has 2 in the first shell and 4 in the second shell. • Only outer shell elec- trons are involved in chemical reactions, so C has 4 e- to share (itmakes 4 attachments).

7. Carbon is tetravalent Carbon shares 4 electrons. Note C makes 4 attachments, but H makes only 1.

8. Carbon is tetravalent Carbon can bond with itself; there are still always 4 attachments (4 bonds). • Ethylene (-ene signifies a double bond) • Isomers of butyne – (-yne signifies a triple bond); still a total of four bonds on each carbon atom.

9. Carbon is tetravalent The e- configuration of C lets it form covalent bonds with many different elements. • In carbon dioxide, one C atom forms 2 double bonds with 2 different O atoms. The structural formula, O = C = O, shows that each atom has completed its valence shells. CO2 is the source for all organic molecules in organisms via the process of photosynthesis.

10. Carbon is tetravalent Another example: • Urea, CO(NH2)2, is a simple organic molecule in which each atom has enough covalent bonds to complete its valence shell. • H needs 1 e- • O needs 2 e- • N needs 3 e-

11. Hydrocarbons Hydrocarbons: organic molecules that consist of only C & H. • Hydrocarbons are the major component of petroleum. • Petroleum is a fossil fuel because it consists of the partially decomposed remains of organisms that lived millions of years ago.

12. Carbon-based life forms Life on Earth is based on carbon. • Four types of carbon molecules are building blocks. • Carbohydrates • Lipids • Nucleic acids • Proteins

13. Carbohydrates Function: fuel and building material; made of equal amounts of C+H2O (carbon hydrates). #H = 2x #O. • Monosaccharides(simple sugars). • Ex: glucose • Disaccharides(double sugars). • Ex: sucrose • Polysaccharidesare long chains of monosaccharides. • Ex: starch (in flour)

14. Carbohydrates Monosaccharides have molecular formulas that are some multiple of CH2O. Ex: glucose - C6H12O6. (#H = 2x #O) • Most names for sugars end in –ose: glucose, ribose. Disaccharides form from monosaccharides by dehydration (an H and an OH are removed). Glucose + glucose produces maltose (and water)

15. Carbohydrates Polysaccharidesare polymers of hundreds to thousands of monosaccharides. • Function in energy storage (used as needed). Ex: starch (plants)&glycogen (in animals’ livers) • Function as strong building materials. Ex: cellulose

16. Lipids Lipids are hydrophobic – don’t mix with water. • In a triglyceride, three fatty acids (same or different) are joined to glycerol. Made of C, H, & O, but the H:O ratio is much greater than 2:1.

17. Lipids • Asaturated fathas nocarbon-carbon double bonds, and it is straight. They pack together – solid at room temperature. • Unsaturated fats haveone or more carbon-carbon double bonds, and they bend. They can’t get close to each other, so they are liquid at room temperature.

18. Lipids Saturated fats come from animal products. • Ex: butter, lard • A diet rich in saturated fats may contribute to cardiovascular disease (heart attack, stroke) through plaque deposits in arteries; obesity, diabetes.

19. Lipids Unsaturated fats come from plant & fish products. • Ex: olive oil, corn oil, safflower oil, fish oils. • Generally considered healthier for the heart.

20. Lipids Functions of lipids • Nutrition: 1g of fat contains twice as much energy as 1g of carbohydrate. • Protection: cushions vital organs & insulates them. • This subcutaneous layer is especially thick in whales, seals, and most other marine mammals.

21. Lipids Functions of lipids • Phospholipids: major components of cell membranes. • Have two fatty acids attached to glycerol and a phosphate group at the third position.

22. Lipids Functions of lipids • Waxes reduce water loss by plants. • Carnauba wax • Steroids • Cholesterol is a component in animal cell membrane. • Many steroids are hormones.

23. Nucleic acids All molecules of the body are programmed by a genetic code in the organism’s DNA, a polymer of nucleic acids. • Nucleic acids store and transmit hereditary in- formation. • Made of C, H, O, N, & P. A nucleic acid

24. Nucleic acids There are two types of nucleic acid polymers: • Ribonucleic acid (RNA) • Single-stranded. • Contains adenine, guanine, cytosine, and uracil. • Sugar is ribose. • Deoxyribonucleic acid (DNA) • Double stranded. • Contains adenine, guanine, cytosine, and thymine. • Sugar is deoxyribose.

25. Proteins Humans have at least 30,000 different proteins, each with a unique structure and function. • Functions include structural support, storage, transport of materials, intercellular signaling, movement, and defense. • Enzymesare one class of proteins that regulate metabolism by moderating chemical reactions. • All proteins are 3 dimensional. • All are constructed from the same set of 20 monomers, called amino acids. • All are made of C, H, O, and N (2 also contain S).

26. Proteins Amino acids are joined by dehydration; the resulting covalent bond is called a peptide bond. • Polymers of amino acids are called polypeptides.

27. Proteins A protein’s function depends on its precise twisting, folding, and coiling into a unique shape. • The order of amino acids determines what the three- dimensional shape will be. • Folding of a protein occurs spontaneously: an emergent property resulting from its specific molecular order.

28. Proteins In individuals with sickle cell disease, abnormal hemoglobins develop because of a single amino acid substitution.

29. Proteins Fibrous proteins are long, insoluble molecules . • For movement (muscle fibers); • For structure and support.   • Collagen in skin. • Cartilage connects tissues. Keratin is found in hair, horns, wool, nails, and feathers.

30. Proteins Globular proteins are soluble and form compact spheroidal molecules in water.   • Antibodies for immunity. • Enzymesare involved in chemical reactions - metabolism (enzymes generally end in –ase). • Transportproteins and receptor proteins in the cell membrane. Hemoglobin – transport of oxygen

31. Proteins Transport proteins and receptor proteins in the cell membrane capture chemicals in the blood and may move them into the cell.

32. Proteins Enzymes catalyze chemical reactions (metabolism). • One enzyme is specific for each chemical reaction. • Enzymes convert one substrate (the raw material) into some product. • Ex: sucrase: binds to sucrose and breaks this disac- charide into fruc- tose and glucose. Enzymes end in –ase.

33. Proteins A protein’s shape can change in response to changes in pH, salt concentration, temperature. These forces disrupt the bonds that maintain the protein’s shape. This is called denaturation. Then the protein won’t work right!