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Chapter 16 Biochemistry and Biotechnology

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1 Chapter 16 Biochemistry and Biotechnology
Copyright ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

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


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