1. Chapter 16 Biochemistry and Biotechnology
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2. Brown Hair, Blue Eyes, and Big Mice (continued)
Modern techniques help us understand how a particular molecular sequence determines a particular trait
Molecular sequence can also be taken out of one organism and implanted into another organism, which may then exhibit the same trait
Four types of molecules are present in living organisms
Lipids
Carbohydrates
Proteins
Nucleic acids

3. Lipids
Cellular components that are insoluble in water but extractable with nonpolar solvents
Fats, oils, fatty acids, steroids, and some vitamins
Illustration located in the middle of page 406

4. Lipids (continued)
Form the structural components of biological membranes and serve as reservoirs for long-term energy storage
Contain more than twice as much energy per gram as any other class of biochemical compounds
Efficient way to store energy

5. Fatty Acid One type of lipid Organic acid with a long hydrocarbon tail
General formula is RCOOH, where R is a hydrocarbon containing between 7 and 21 carbon atoms
Illustration located in the middle of page 406

6. Triglycerides
Fats and oils are a chemical combination of glycerol and three fatty acids
Fats and oils are triglycerides
Triglyceride formed between the reaction of glycerol and stearic acid is tri-stearin
Illustration located on the bottom of page 407

7. Properties of Tristearin
Has three long hydrocarbon chains, making it nonpolar and immiscible with water
Energy is extracted via the oxidation of these long chains (as in gasoline)
Fat is conveniently stored in the body
Provides thermal insulation
R groups are composed of saturated hydrocarbons

8. Triolein Main component of olive oil
R groups of triolein each contain a double bond
Double bond interferes with efficient packing of neighboring molecules and makes triolein a liquid at room temperature
Illustration located at the bottom of page 408

9. Concept Check 16.1 Solution
Fatty acids are components of fats. Fats are triglycerides (glycerol triesters) of three fatty acids (long chain carboxylic acids with more than 12 carbons).

10. Carbohydrates Function in the body as short-term energy storage
Carbohydrates often have chemical formulas that are a multiple of CH2O, carbon, and water
Chemical structure is related to:
Carbohydrates are polyhydroxy aldehydes or ketones, or their derivatives
Illustration located at page 411

11. Carbohydrates (continued)
Undergo an intermolecular cyclization reaction in which one of the —OH groups reacts with the CO group to form a ring
Illustration located at page 411

12. Properties of Glucose
Large hydroxyl groups have strong hydrogen bonding with each other and with water
Glucose’s ability to be soluble in bodily fluids makes it a quick energy source
Oxidation of glucose evolves less energy per gram than the oxidation of octane or lipids
Structure of glucose can be viewed as a compromise between the need to store the energy efficiently and the need for it to be soluble in the aqueous media where it is used

13. Concept Check 16.3
Which of the following structures are carbohydrates?

14. Concept Check 16.3 Solution
Structures (a) and (c) are carbohydrates. They have formulas of the form Cx(H2O)y.

15. Saccharides
Monosaccharides that join together to form double-ringed structures
Disaccharides
Two monosaccharide rings connected to form a single structure

16. Saccharides (continued)
Monosaccharides join in long chains to form polysaccharides
Illustration is in the middle of page 419 to 413.

17. Polysaccharides (Complex Carbohydrates)
Most common are starch and cellulose
Starch: Oxygen atom joining the glucose units points down relative to the planes of the rings (alpha linkage)
Cellulose: Oxygen atoms are parallel to the planes of the rings (beta linkage)

18. Concept Check 16.4
Classify each of the following carbohydrates as a monosaccharide, disaccharide, or polysaccharide.

19. Concept Check 16.4 Solution
Compounds (a) and (d) are carbohydrates in their monocyclic form. Carbohydrate (b) has two linked monosaccharide rings. Carbohydrate (c) has many repeating monosaccharide rings.

20. Proteins
Protein molecules are composed of a long chain of repeating units known as amino acids
Amino acids are molecules that contain both an amine group and a carboxylic acid group
The simplest R group is the hydrogen atom; the amino acid is glycine
Differences among amino acids arise from different R groups
Varying the order of amino acids in a protein helps achieve an infinite number of properties

21. Proteins (continued)
Compose much of the physical structure of the body (muscle, hair, and skin)
Act as enzymes to control chemical reactions
Act as hormones to regulate metabolic processes
Transport oxygen from the lungs to cells
Act as antibodies to fight invading organisms

22. Table 16.2: Protein Functions

23. Proteins (continued 2)
Although the body can metabolize proteins for energy, it does so only as a last resort
Proteins have more important functions as the workhorse molecules in the body
Meats are good sources of protein.
Photo in the lower left-hand corner of page 416

24. Concept Check 16.5
Which of the following molecules are amino acids?

25. Concept Check 16.5 Solution
In the general structure of amino acids, the amino and carboxyl groups are attached to the same carbon

26. Concept Check 16.5 Solution (continued)
Compounds (b) and (d) are amino acids.

27. The Peptide Bond
Acidic end of one amino acid reacts with the amine side of another to form a peptide bond
Dipeptide: Two linked amino acids
Polypeptides: Chains of amino acids with 50 units or less
Proteins: Chains with over 50 amino acid units
Illustration near the bottom of page 427

28. Concept Check 16.6
Draw the tripeptide that results from an alanine attaching to each side of cysteine.

29. Concept Check 16.6 Solution
The tripeptide is built as follows:
The formation of the peptide bond is a condensation reaction (See Chapter 15).

30. Sickle Cell Anemia
Hemoglobin (Hb), which transports oxygen in the blood, consists of four amino acid chains, called subunits
Each subunit consists of 146 amino acid units for a total of 584 amino acids
C2952H4664O832N812S8Fe4
Replacing polar glutamate with nonpolar valine at one position on two subunits lowers the solubility of Hb, resulting in red blood cell deformation
Deformed blood cells block the flow of blood to capillaries

31. Protein Structure
Structure of a protein is finely tuned to achieve a specific function
Protein structure is characterized in four categories
Primary
Secondary
Tertiary
Quaternary

32. Primary Structure of a Protein
Held together by peptide bonds between the acid side of one amino acid and the amine side of its neighbor
Gly-Val-Ala-Asp is the abbreviation used to describe a short polypeptide
Denotes glycine, valine, alanine, and aspartic acid

33. Secondary Structure
The way the amino acid chain orients itself along its axis
Common secondary structures
Alpha-helix
Pleated sheet
Figure 16-3; page 429

34. Alpha-Helix
Helical shape is maintained by hydrogen bonds between different amino acids along the protein chain
α-keratin is an alpha-helix and is responsible for the elasticity of hair and wool
It works like a spring
Figure 16.3; page 423

35. Pleated Sheet Protein forms zigzag chains that stack neatly together
Silk is a pleated sheet
Inelasticity of silk is related to full extension of protein chains
Softness of silk is related to the ease with which neighboring sheets slide past each other
Figure 16.4; page 430

36. Tertiary and Quaternary Structures
Tertiary structure of a protein is the bending and folding due to interactions between amino acids on the chain
Completely extended
Globular or ball-like
Many proteins consist of two or more subunits that are themselves held together by interactions between the chains
Arrangement of the subunits of the protein chain in space is the quaternary structure

37. Interactions Responsible for Protein Tertiary and Quaternary Structure
Tertiary and quaternary structures of proteins are maintained by four kinds of interactions between R groups on different parts of a protein strand:
Hydrogen bonding
Hydrophobic interactions
Salt bridges
Disulfide linkages
Figure 16.6; page 424

38. Common Proteins: Hemoglobin (Hb)
Entire structure was not known until late 1950s
Hb folds to hold four flat molecules called heme groups
Heme groups act as molecular oxygen carriers
Pick up oxygen at lungs
Release it at cells undergoing glucose oxidation

39. Common Proteins: Hemoglobin (Hb) (continued)
Interior of Hb molecule is highly nonpolar
Repels water
Allows oxygen to get in and out
Exterior is polar
Hemoglobin is soluble in water
Figure 16.7; page 425

40. α-Keratin: Component of Hair and Wool
Wool: The α-helix structure is maintained by hydrogen bonding that can be broken and reformed by washing in hot water, which is the cause of shrinking
Hair: Three α-helices in a coil held together by hydrogen bonds and sulfur bridges, which upon chemical treatment can easily break and reform
Picture of shirts is located at the bottom of page 426.

41. Lysozyme Acts as an enzyme
Dissolves certain bacteria by promoting bond cleavage of polysaccharide units within their cell walls
Found in nasal mucus and tears
Discovered by Alexander Fleming in 1922

42. Insulin Acts as a hormone Synthesized in the pancreas
Small (51 amino acids)
Promotes entry of glucose into muscle and fat cells, lowering blood glucose level
Diabetics may have to inject insulin
Figure 16.9; page 426

43. Nucleic Acids
Nature’s blueprints for making proteins are found in nucleic acids
Types
DNA (deoxyribonucleic acid)
Occurs primarily in the cell information center (nucleus)
RNA (ribonucleic acid)
Occurs throughout the interior of cells

44. Nucleotides
Nucleic acids that are long, chainlike molecules composed of thousands of repeating units
Phosphate and sugar groups are identical in every nucleotide, but there are four different bases
A, adenine
T, thymine
C, cytosine
G, guanine
Figure 16.10; page 427

45. Nucleotides (continued)
Codon
A group of three bases that codes for one amino acid
With minor exceptions, the code is universal; it is identical in all organisms from bacteria to humans

46. DNA
Occurs in biological structures called chromosomes, 46 in humans, found in the nucleus of a cell
Figure 16.11; page 429

47. DNA Replication
Mechanism elucidated by James Watson and Francis Crick in 1953
DNA consists of two complementary strands of nucleic acid wrapped around each other in the now-famous double helix
When a cell is about to divide, the DNA within its nucleus unzips across the hydrogen bonds that run along its length, forming two complementary daughter strands
Daughter DNA molecules are identical in every way to the parent

48. Figure 16.12: DNA Replication
A pairs with T
C pairs with G
Figure 16.12; page 430

49. Concept Check 16.7
Draw the complementary strand for the DNA shown.

50. Concept Check 16.7 Solution
In the complementary strand, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G).

51. Protein Synthesis
Genes are sections of DNA thousands of base pairs long
When a cell needs the protein specified by a particular gene, that portion of the DNA unwinds
Figure 16.13; page 431

52. Protein Synthesis (continued)
A messenger RNA (mRNA) is formed, which is a complement to the unwound section
mRNA goes to a ribosome, where protein synthesis occurs
When the ribosome reaches the end of the mRNA strand, the protein is complete and moves off to carry out its function

53. Viruses Definition lies somewhere between life and nonlife
Difficult to kill and do not respond to antibiotics
Require the machinery of a host cell to reproduce
Virus takes over a host cell and inserts its own DNA into the chromosomes of the host
Host then expresses viral DNA
Cause diseases such as common cold, flu, measles, polio, smallpox, and ebola

54. Acquired Immune Deficiency Syndrome (AIDS)
Human immunodeficiency virus (HIV) causes AIDS
HIV attacks immune system cells, releasing its RNA
Reverse transcriptase forms viral DNA from the RNA
An enzyme inserts the DNA into the chromosomes of the host cell
Immune system cells die, releasing daughter HIVs, and the cycle repeats destroying the cells of the immune system

55. Recombinant DNA Technology
Employs restriction enzymes that cut DNA in specific places
DNA pieces can be separated by gel electrophoresis
Even single genes can be isolated
Figure 16.14; page 432

56. Recombinant DNA Technology (continued)
A DNA strand obtained from one organism (a human) can be introduced into another (a bacterium)
Bacterium is cultured, replicating DNA
Source for the protein coded for by that DNA

57. Pharmaceuticals Insulin Human growth hormone (HGH)
Animal insulin is not tolerated by all diabetics
The gene that codes for the production of human insulin was copied and expressed by a bacterium
These bacteria become a human insulin factory
Most diabetics take genetically engineered insulin today
Human growth hormone (HGH)
Developed with recombinant DNA technology
Some children make insufficient amounts of this protein and fail to grow to normal adult size

58. Agriculture
Impact of genetically modified (GM) crops on agriculture has been swift and significant
These crops are more resistant to attack by pests and less susceptible to spoilage, resulting in higher food quality

59. Agriculture (continued)
Genetic engineering has helped create agricultural products such as the rot-resistant tomato
These tomatoes have a longer shelf life than ordinary tomatoes

60. Genetic Screening and Disease Therapy
Screening can be done for genes that may indicate predisposition to any disease
Should insurance companies have access to this information?
Genetic engineering techniques might one day be used to treat genetic diseases directly
Cystic fibrosis (CF)
Huntington’s disease
Muscular dystrophy (MD)

61. Cloning When an egg DNA is modified, whole new organisms can develop
Science fiction becomes possible in reality
Embryonic cloning has been achieved in animals
By nuclear transfer, the cloning of adult organisms has been achieved in mammals
Picture: This lamb, Dolly, was cloned from the DNA of a 6-year-old adult ewe; page 442

62. Figure 16:16: Cloning
Page 436

63. Therapeutic Cloning and Stem Cells
Reproductive cloning is viewed as unethical
Therapeutic cloning is regarded as acceptable
Goal is to produce embryonic stem cells that are genetically identical to the adult donor
Embryonic stem cells are the master cells normally present in embryos days after the fertilization of an egg

64. Therapeutic Cloning and Stem Cells (continued)
Therapeutic cloning offers the potential to make embryonic stem cells that are a perfect genetic match to the donor of the DNA from whom the stem cells are cloned
Stem cells are the master cells that can become any cell
No rejection by the immune system
Fraught with controversy

65. Concept Check 16.8
What might be some of the ethical issues associated with embryonic stem cells?

66. Concept Check 16.8 Ideas Pros:
Embryonic stem cells can become any cell in the human body such as the liver, the brain, and heart cells, making organ tissue regeneration possible.
No chance of tissue and organ rejection because the new cells will have an exact DNA match
Cure degenerative diseases such as Parkinson’s disease

67. Concept Check 16.8 Ideas (continued)
Cons:
Religious and ethical objections to ending potential life to harvest embryonic stem cells
Current laws and ethical guidelines have not caught up with rapidly evolving science and technology.

68. Chapter Summary Molecular Concept Societal Impact
Biochemical Compounds
Chemical study of the molecules that compose life has led to incredible advances in medicine, agriculture, and other related technologies
Triesters
Description of living things on the molecular level has also had an impact on how humans view themselves
Proteins
When humans lack the gene to make a particular protein, or when the gene to make a particular protein is faulty, disease results
Nucleic acids
Scientists have also modified the DNA in fertilized eggs to produce genetically engineered organisms