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Chapter 2

CHAPTER 2 THE MOLECULAR COMPOSITION OF PLANT CELLS. Chapter 2. menu. yes. enter. Setting your Response Device. Set response device to channel 26 1. Press menu button 2. Leave presentation mode – yes 3. Use “yes” button to scroll down, “no” to scroll up. Scroll to “change channel”

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Chapter 2

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  1. CHAPTER 2 THE MOLECULAR COMPOSITION OF PLANT CELLS Chapter 2

  2. menu yes enter Setting your Response Device Set response device to channel 26 1. Press menu button 2. Leave presentation mode – yes 3. Use “yes” button to scroll down, “no” to scroll up. Scroll to “change channel” 4. Press enter 5. type in 26, press “enter” menu

  3. OUTLINE Outline • I. THE ELEMENTS OF LIFE: Chemical elements and compounds • II. ORGANIC MOLECULES • Carbohydrates • Lipids • Proteins • Nucleic Acids • Secondary Metabolites

  4. ELEMENTS

  5. I. Elementsof life Elements • There are 92 naturally occurring elements- • Six are used in living organisms Limiting Limiting

  6. I. Elements of life Elements • Monomers and Polymers: • . Many biological compounds are composed of repeating units • A single unit is called a monomer • Monomers linked together = polymer • Examples of polymers • . Cellulose (polymers of sugars) • . Proteins (polymers of amino acids) • . DNA (polymer of nucleic acids) • . Fats

  7. CARBOHYDRATES

  8. Carbohydrates are composed of sugars Carbohydrates Sugars are named by the number of molecules that are linked together Monosaccharide = monomer of sugar Disaccharide = two sugars linked together Polysaccharide = many sugars linked together

  9. CH2OH O OH OH HO OH MONOSACCHARIDE - GLUCOSE Glucose-structure H SHORTHAND 6 H O C H C O 5 H H H C C 1 4 O H H O H O C C 2 3 H O H H Glucose (dextrose) = monomer C6H12O6 [Figure 2.2]

  10. MONOSACCHARIDE - FRUCTOSE Fructose C6H12O6 O CH2OH CH2OH Fructose = monomer Different structure (the ring has 4 carbons instead of 5)

  11. Isomers • Glucose and fructose sugars are isomers. • They contain the same number of carbon, hydrogen and oxygen atoms but structurally are different • The structural difference imparts different properties • Glucose is not very sweet but fructose is very sweet. The body metabolizes these two sugars differently. Glucose and fructose enter the cell in different ways

  12. MONOSACCHARIDE - RIBOSE Ribose O 5 1 4 3 2 • Ribose is also a 4 carbon ring • Ribose is a component of DNA and RNA

  13. The disaccharide sucrose (table sugar) is a transport form of sugar in plants Sucrose

  14. Polysaccharides are many sugar molecules linked together Sugar polymers • STARCH (AMYLOSE) • CELLULOSE • GLYCOGEN • AMYLOPECTIN • OTHER POLYSACCHARIDES

  15. Starches are storage polysaccharides Amylose • Amylose (starch) is a polymer of alpha-glucose = (polysacccharide) [Fig 2-4]

  16. Starch is used by plants to store sugars for later use • Starch is easily digested • enzymes for starch digestion are found in your ______ and are produced by your _________ • Another word for starch is amylose • Starch digesting enzymes are called amylases

  17. Germinating corn and starch Corn kernel with endosperm stained to show starch

  18. Cellulose is a polysaccharide Cellulose • Cellulose is a polymer of beta-glucose [Fig. 2-5]

  19. Cellulose

  20. Cellulose fibers provide different food consistencies Cellulose Cellulose fibers in apple cell wall Cellulose fibers in carrot cell wall Cellulose fibers in water chestnut cell wall

  21. Cellulose • Cellulose cannot be digested by mammals • Some bacteria and fungi can digest cellulose • Termites and ruminants can digest cellulose because they have cellulose-digesting microbes in their digestive tracts

  22. LIPIDS

  23. Pectins and hemicellulases are also structural polysaccharides and help bind together the plant cell wall They are used as food thickeners and adhesives [Figs. 2-6, 2-7]

  24. Carrageenan Carrageenan fibers (polysaccharide) Carrageenan is used as a food thickener

  25. Types of Lipids Lipids-types 1. Oils and Fats (oils are fats that are liquid at room temperature) 2. Phospholipids 3. Waxes: Waxes are mixtures of fatty acids linked to long chain alcohols

  26. Fats and Oils are triglycerides that store energy Lipids-fats and oils • Fats and oils are composed of a molecule of glycerol with three long chain organic molecules called fatty acids linked to it (thus triglycerides) unsaturated

  27. Fats and Oils Lipids-fats and oils • Fats with no carbon-carbon double bonds (C=C) are called saturatedfats • Saturated fats raise cholesterol levels in the blood • Foods with large amounts of saturated fatty acids include animal fat and tropical oils (coconut oil, palm seed oil)

  28. Phospholipids Phospholipids • Phospholipids: Membranes contain lipids in which a phosphate group is substituted for one of the three fatty acids. These are called phospholipids.

  29. Phospholipids [Fig. 2-10]

  30. The phosphate end of the molecule is hydrophyllic (water loving) • The fatty acid end is hydrophobic (water repellent) • These properties give membranes their specific properties Phospholipids [Fig. 2-11]

  31. Phospholipids

  32. Cutin, Suberin and Waxes are lipids that prevent water loss Lipids-waxes Waxes: Waxes are mixtures of fatty acids linked to long chain alcohols Waxes form a hard water repellent coating on many leaves that protects them. They are embedded in the top layer of leaves (the cuticle) and form a waxy surface on top of the cuticle

  33. Waxes Lipids-waxes • Commercial uses of waxes • Jojoba (southwestern desert plant) oil similar to sperm whale oil and is used in cosmetics • Candellila (Euphorbia antisyphilitica) wax was used as a non-melting way to coat M & Ms. Now seriously endangered. • Carnauba wax is from the carnauba palm • Bayberry wax for candles and scents

  34. Steroids are lipids. They are distinguished from other lipids by the presence of four interconnecting rings. They are important in stabilizing membranes Cholesterol and the hormone estrogen are steroids [Fig. 2-14]

  35. PROTEINS

  36. Amino Acids Amino Acids O H H N C C OH R AMINE GROUP NH2 CARBOXYL GROUP COOH Proteins are polymers of amino acids linked by peptide bonds.

  37. Amino Acids Amino Acids There are 20 “normal” amino acids in living organisms Some are neutral but polar, that is, the electrons tend to concentrate towards one end of the molecule. Others are neutral and non-polar. Still others have positive or negative electrical charges making them acidic and basic respectively. [Fig 2-15]

  38. Amino Acids

  39. Amino Acids

  40. Amino Acids

  41. Peptide Bonds Peptide bonds O O H H2N C C OH H N C C OH R R To form a peptide bond, water is removed [Fig. 2-16]

  42. Proteins O H2N C C R Peptide bonds H O O N C C OH H2N C C R R Peptide Bond Proteins are polymers of amino acids linked by peptide bonds.

  43. Proteins Proteins and amino acids Proteins are polymers of amino acids linked by peptide bonds. Proteins are structural components of cells, serve as food storage reservoirs and act as biological catalysts (enzymes).

  44. Proteins are the direct products of genes

  45. Proteins have additional structure Protein structure • Protein structure and terminology • Primary structure = the amino acid sequence. • Secondary structure = Interactions between different amino acids in a chain can form a helix or pleated sheet. • Tertiary structure = Interactions between cysteines (one of the amino acids with a sulfur side group) and hydrogen bonds fold the chain into larger structures consisting of regions that are helices or pleated sheets. • Quaternary structure = Different polypeptides unite to form a functional protein.

  46. [Fig. 2-17] Secondary structure – an alpha helix

  47. Protein structure [Figs 2-18, 2-19]

  48. Proteins can be denatured Protein structure Proteins can be denatured by heat. They loose their two and three-dimensional structure When you boil an egg, you are denaturing the proteins

  49. Proteins control chemical reactions within the body Protein function • Enzymes: Catalysts for biological reactions (Note that -ase on the end of the name denotes that this molecule is an enzyme) • Usually contain active sites which attract and hold other molecules. • Enzymes usually break molecules down into smaller groups or build larger groups • Alpha-amylase digests starch (where would it be found?) • Proteases digest proteins • DNA polymerase (polymerizes DNA molecules)

  50. Protein function-Enzymes

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