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Molecules of Life
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  1. Cellphone addiction harming academic performance is 'an increasingly realistic possibility‘ August 28, 2014 Women college students spend an average of 10 hours a day on their cellphones and men college students spend nearly eight, with excessive use posing potential risks for academic performance, according to a Baylor University study on cellphone activity published in the Journal of Behavioral Addictions. "The study notes that approximately 60 percent of college students admit they may be addicted to their cell phone, and some indicated they get agitated when it is not in sight, said Roberts,." The study -- based on an online survey of 164 college students -- examined 24 cellphone activities and found that time spent on 11 of those activities differed significantly across the sexes. Some functions -- among them Pinterest and Instagram -- are associated significantly with cellphone addiction. But others that might logically seem to be addictive -- Internet use and gaming -- were not. General findings of the study showed that: • Of the top activities, respondents overall reported spending the most time texting (an average of 94.6 minutes a day), followed by sending emails (48.5 minutes), checking Facebook (38.6 minutes), surfing the Internet (34.4 minutes) and listening to their iPods. (26.9 minutes). • Women spend more time on their cellphones. While that finding runs somewhat contrary to the traditional view that men are more invested in technology, "women may be more inclined to use cellphones for social reasons such as texting or emails to build relationships and have deeper conversations." Excessive use of cellphones poses a number of possible risks for students, he said. "Cellphones may wind up being an escape mechanism from their classrooms. For some, cellphones in class may provide a way to cheat," Roberts said. Excessive or obsessive cellphone use also can cause conflict inside and outside the classroom: with professors, employers and families. And "some people use a cellphone to dodge an awkward situation. They may pretend to take a call, send a text or check their phones," Roberts said. Study participants were asked to respond to 11 statements such as "I get agitated when my cellphone is not in sight" and "I find that I am spending more and more time on my cellphone" to measure the intensity of their addiction. "We need to identify the activities that push cellphone use from being a helpful tool to one that undermines our well-being and that of others," Roberts said.

  2. Chapter 3 Molecules of Life

  3. What is an Organic Compound?What is a Hydrocarbon?Why is so great about Carbon?

  4. 3.1 What Are the Molecules of Life? • The molecules of life contain a high proportion of carbon atoms: • Complex carbohydrates • Lipids • Proteins • Nucleic acids

  5. The Stuff of Life: Carbon • The stuff of life: carbon • Molecules that have primarily hydrogen and carbon atoms are said to be organic • Carbon’s importance to life arises from its versatile bonding behavior • Carbon has four vacancies • Many organic molecules have a backbone: a chain of carbon atoms

  6. The Stuff of Life: Carbon A C B D

  7. From Structure to Function • Hydrocarbon: consists only of carbon and hydrogen atoms • Functional group: • An atom (other than hydrogen) or small molecular group bonded to a carbon of an organic compound • Imparts a specific chemical property

  8. From Structure to Function • All biological systems are based on the same organic molecules • The details of those molecules differ among organisms • Monomers: subunits of larger molecules • Simple sugars, fatty acids, amino acids, and nucleotides • Polymers: consist of multiple monomers

  9. From Structure to Function • Cells build polymers from monomers, and break down polymers to release monomers • These processes of molecular change are called chemical reactions

  10. From Structure to Function • Metabolism: all enzyme-mediated chemical reactions by which cells acquire and use energy • Enzyme:organic molecule that speeds up a reaction without being changed by it

  11. From Structure to Function • Condensation: chemical reaction in which an enzyme builds a large molecule from smaller subunits • Water is formed during condensation • Hydrolysis: chemical reaction in which an enzyme uses water to break a molecule into smaller subunits

  12. From Structure to Function A B

  13. 3.2 What Is a Carbohydrate? • Carbohydrate: organic compound that consist of carbon, hydrogen, and oxygen in a 1:2:1 ratio • Three main types of carbohydrates in living systems: • Monosaccharides • Oligosaccharides • Polysaccharides

  14. Simple Sugars • Monosaccharides (one sugar) are the simplest type of carbohydrates • Common monosaccharides have a backbone of five or six carbon atoms • Examples: • Glucose has six carbon atoms • Five-carbon monosaccharides are components of the nucleotide monomers of DNA and RNA

  15. Simple Sugars C6H12O6 glucose

  16. Simple Sugars • Cells use monosaccharides for cellular fuel • Breaking the bonds of sugars releases energy that can be harnessed to power other cellular processes • Monosaccharides are also used as: • Precursors for other molecules • Structural materials to build larger molecules

  17. Polymers of Simple Sugars • Oligosaccharides are short chains of covalently bonded monosaccharides • Disaccharides consist of two monosaccharide monomers • Examples: • Lactose: composed of glucose + galactose • Sucrose: composed of glucose + fructose

  18. Polymers of Simple Sugars • Polysaccharides: chains of hundreds or thousands of monosaccharide monomers • Most common polysaccharides: • Cellulose • Starch • Glycogen

  19. Polymers of Simple Sugars • Cellulose • Main structural component of plants • Tough and insoluble • Composed of chains of glucose monomers stretched side by side and hydrogen-bonded at many —OH groups

  20. Polymers of Simple Sugars • Starch • Main energy reserve in plants • Stored roots, stems, leaves, seeds, and fruits • Composed of a series of glucose monomers that form a chain that coils up

  21. Polymers of Simple Sugars • Glycogen • Main energy reserve in animals • Very abundant in muscle and liver cells • Highly branched chains of glucose monomers

  22. Polymers of Simple Sugars A Cellulose B Starch C Glycogen

  23. 3.3 What Are Lipids? • Lipids: fatty, oily, or waxy organic compounds • Many lipids incorporate fatty acids: consist of a long hydrocarbon “tail” with a carboxyl group “head” • The tail is hydrophobic • The head is hydrophilic

  24. Fats • Fats: lipid that consists of a glycerol molecule with one, two, or three fatty acid tails • Triglyceride: a fat with three fatty acid tails • Saturated fats: triglycerides with saturated fatty acid tails; solid at room temperature • Unsaturated fats: triglycerides with unsaturated fatty acid tails; liquid at room temperature

  25. Fats A

  26. Steroids • Steroids: lipids with no tails • Contain a rigid backbone that consists of twenty carbon atoms arranged in a characteristic pattern of four rings • Functional groups attached to the rings define the type of steroid • Examples: estrogen and testosterone • Dictates many sex characteristics

  27. Steroids an estrogen testosterone female male

  28. 3.4 What Are Proteins? • Amino acid subunits • Cells can make thousands of different proteins from only twenty kinds of monomers called amino acids • An amino acid contains: • An amine group (—NH2) • A carboxyl group (—COOH, the acid) • A side chain called an “R group”; defines the kind of amino acid

  29. Amino Acid Subunits amine group carboxyl group R group

  30. Amino Acid Subunits • The covalent bond that links amino acids in a protein is called a peptide bond • A short chain of amino acids is called a peptide • As the chain lengthens, it becomes a polypeptide • Proteins consist of polypeptides that are hundreds or even thousands of amino acids long

  31. 15 5 1 10 30 35 20 25 45 40 50 55 65 60 70 85 80 75 Amino acid 95 90 100 110 115 105 125 120 129 Figure 3.18

  32. SEM 7. . . 146 6 5 1 2 3 4 Normal red blood cell Normal hemoglobin a Normal hemoglobin SEM 7. . . 146 6 1 5 2 3 4 Sickled red blood cell Sickle-cell hemoglobin b Sickle-cell hemoglobin Figure 3.19

  33. Structure Dictates Function • Proteins function in movement, defense, and cellular communication • Example: enzymes • Lipase, Lactase, Protease, Amylase, Cellulase • A protein’s biological activity arises from and depends on its structure

  34. Structure Dictates Function 1 2 3 4 5

  35. 3.5 Why Is Protein Structure Important? Heat, some salts, shifts in pH, or detergents can denature(unravel) a protein by breaking hydrogen bonds Denaturation causes a protein to lose its function

  36. 3.6 What Are Nucleic Acids? • Nucleotide: consists of a sugar with a five-carbon ring bonded to a nitrogen-containing base and one, two, or three phosphate groups • Example: ATP (adenosine triphosphate); an energy carrier in cells

  37. What Are Nucleic Acids? A ATP (a nucleotide) base (adenine) phosphate groups

  38. What Are Nucleic Acids? • Nucleic acids: chains of nucleotides in which the sugar of one nucleotide is bonded to the phosphate group of the next • RNA (ribonucleic acid): single-stranded chain of nucleotides; important for protein synthesis • DNA (deoxyribonucleic acid): consists of two chains of nucleotides twisted into a double helix; holds information to build a new cell

  39. What Are Nucleic Acids? B RNA (a nucleic acid)

  40. 3.7 Application: Fear of Frying Trans fats have unsaturated fatty acid tails with hydrogen atoms around the double bonds Small amounts of trans fats occur naturally Main source of trans fats is an artificial food product called partially hydrogenated vegetable oil Hydrogenation: adds hydrogen atoms to oils in order to change them into solid fats

  41. Application: Fear of Frying In 1908, Procter & Gamble Co. developed partially hydrogenated oil to make candles As electricity replaced candles, the company began marketing partially hydrogenated oils as a low cost alternative to lard For decades, hydrogenated oils were considered healthier than animal fats

  42. Application: Fear of Frying • Trans fats raise the level of cholesterol in our blood more than any other fat • Directly alters the function of our arteries and veins • Eating as little as two grams a day of hydrogenated vegetable oil increases a person’s risk of atherosclerosis, heart attack, and diabetes

  43. processed to extract Starch broken down into Glucose converted to sweeter Fructose added to foods as high-fructose corn syrup Ingredients: carbonated water, high-fructose corn syrup, caramel color, phosphoric acid, natural flavors Figure 3.8

  44. THG Figure 3.14

  45. Large biological molecules Functions Components Examples Monosaccharides: glucose, fructose Disaccharides: lactose, sucrose Polysaccharides: starch, cellulose Dietary energy; storage; plant structure Carbohydrates Monosaccharide Long-term energy storage fats; hormones steroids Fats triglycerides; Steroids testosterone, estrogen Fatty acid Lipids Glycerol Components of a triglyceride Amino group Carboxyl group Lactase an enzyme, hemoglobin a transport protein Enzymes, structure, storage, contraction, transport, and others Proteins Side group Amino acid Phosphate Base Information storage Nucleic acids DNA, RNA Sugar Nucleotide Figure UN3-2

  46. Friday:Read Chapter 4 & 5

  47. The Stuff of Life: Carbon A B

  48. From Structure to Function (cont’d.)