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Overview: The Molecules of Life

This overview explains the different classes of macromolecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids. It highlights the synthesis and breakdown of polymers, the structure and function of carbohydrates, and the composition and properties of fats.

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Overview: The Molecules of Life

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  1. Overview: The Molecules of Life • Within cells, small organic molecules are joined together to form larger molecules • Macromolecules are large molecules composed of thousands of covalently connected atoms. • The four classes of macromolecules that are important to life are: • Carbohydrates • Lipids • Proteins • Nucleic acids

  2. Most macromolecules are polymers, built from monomers • A polymer is a long molecule consisting of many similar or identical building blocks called monomers (monomers) Glycogen (a polymer) is made of glucose monomers A polypeptide (a polymer)

  3. Most macromolecules are polymers, built from monomers • Three of the four classes of life’s organic molecules are polymers: • Carbohydrates • Proteins • Nucleic acids

  4. The Synthesis of Polymers by DEHYDRATION REACTIONS • Monomers form larger molecules called polymers by condensation reactions called dehydration reactions. • Adehydration reaction occurs when two monomers bond together through the loss of a water molecule http://www.youtube.com/watch?v=UyDnnD3fMaU

  5. HO H HO H 1 2 3 Short polymer Unlinked monomer Dehydration removes a water molecule, forming a new bond H2O H HO 1 4 2 3 Longer polymer (a) Dehydration reaction in the synthesis of a polymer

  6. The Breakdown of Polymers by HYDOLYSIS REACTIONS • Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction. • In hydrolysis, bonds are broken by the addition of water molecules. • http://www.youtube.com/watch?v=7e2IkQHxszM

  7. Fig. 5-2b HO H 4 1 2 3 Hydrolysis adds a water molecule, breaking a bond H2O HO H H HO 2 1 3 (b) Hydrolysis of a polymer

  8. Carbohydrates serve as fuel and building material • Carbohydrates include single (simple) sugars and their polymers • Carbohydrates may be classified as: • Monosaccharides (the simplest) • Disaccharides • Oligosaccharide (3-9) • Polysaccharides

  9. Monosaccharides • Monosaccharides have molecular formulas that are usually multiples of CH2O (CH2O)nwhere n ranges from 3-7 • Glucose (C6H12O6) is the most common monosaccharide.

  10. LE 5-3 Triose sugars (C3H6O3) Pentosesugars (C5H10O5) Hexose sugars (C6H12O6) Aldoses Glyceraldehyde Ribose Galactose Glucose Ketoses Dihydroxyacetone Ribulose Fructose

  11. Monosaccharides • Functions of monosaccharides: • major fuel (source of energy) for cells and • raw material for building other molecules such as fatty acids and amino acids.

  12. Disaccharides • A disaccharide is formed when a dehydration reaction joins two monosaccharides • The covalent bond joining two monosaccharides is called aglycosidic linkage Dehydration reaction in the synthesis of maltose 1–4 glycosidic linkage Glucose Glucose Maltose Dehydration reaction in the synthesis of sucrose 1–2 glycosidic linkage Sucrose Fructose Glucose

  13. Polysaccharides • Polymers of monosaccharides • Based on their function, there are two types of polysaccharides: • Storage polysaccharides. • Structural polysaccharides.

  14. Concept 2.3 Carbohydrates Consist of Sugar Molecules

  15. Concept 2.3 Carbohydrates Consist of Sugar Molecules

  16. Cellulose (AStructural Polysaccharides) • Cellulose is a major component of the tough wall of plant cells • Cellulose is a polymer of -glucose. http://www.youtube.com/watch?v=UE85oMrKcKQ&feature=PlayList&p=D962AE54DF078C61&index=11&playnext=2&playnext_from=PL

  17. LE 5-8 Cellulose microfibrils in a plant cell wall Cell walls Microfibril 0.5 µm Plant cells Cellulose molecules b Glucose monomer

  18. Fats • Fats are constructed from one glycerol and three fatty acid molecules • Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon • A fatty acid consists of a carboxyl group attached to a long hydrocarbon skeleton

  19. Fatty Acids • Fatty acids vary in length (number of carbons) and in the number and locations of double bonds • Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds • Unsaturated fatty acids have one or more double bonds Alpha linolenic acid (ALA) An Omega-3 f.a. and the parent of other omega-3 f.as

  20. Fats • Three fatty acids are joined to a glycerol molecule by three dehydration reactions creating a fat, triglyceride, ORtriacylglycerol molecule. • The bond between each fatty acid and glycerol is called an ester linkage.

  21. Fats (Saturated fats) • Fats made from saturated fatty acids are called saturated fats • Most animal fats are saturated • Saturated fats are solid at room temperature • A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits

  22. Fats (Unsaturated fats) • Fats made from unsaturated fatty acids are called unsaturated fats • Plant fats and fish fats are usually unsaturated • Plant fats and fish fats are liquid at room temperature and are called oils

  23. Fats • Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats because they are hydrophobic

  24. Major Functions of Fats • 1- Good source of energy. One gram of fat stores more than twice as much energy as one gram of a polysaccharide, such as starch. • 2- Adipose tissue (the tissue that stores fats in the body) also functions to: • cushion vital organs such as the kidneys. • insulate the body (a layer of fat beneath the skin). The subcutaneous layer is especially thick in whales, seals, and most other marine mammals.

  25. Phospholipids • In a phospholipid, two fatty acids and a phosphate group are attached to glycerol • The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head hydrophilic head Hydrophobic tails

  26. Phospholipids in water (a micelle formation)

  27. Phospholipids in water (a bilayer formation) The structure of phospholipids in water results also in a bilayer arrangement found in cell membranes Hydrophilic head WATER WATER Hydrophobic tails Phospholipids are the major component of all cell membranes

  28. Steroids • Steroids are lipids characterized by a carbon skeleton consisting of four fused rings • Different steroids are created by varying functional groups attached to the rings. Estradiol Female lion Male lion Testosterone

  29. Cholerterol (A Steroid) • Cholesterol, an important steroid, is a component in animal cell membranes • Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease

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