Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb PowerPoint ® Lecture Slides prepared by Vince Austin, University of Kentucky 2 Chemistry Comes Alive Part B

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Biochemistry  Organic compounds  Contain carbon, are covalently bonded, and are often large  Inorganic compounds  Do not contain carbon  Water, salts, and many acids and bases

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Properties of Water  High heat capacity – absorbs and releases large amounts of heat before changing temperature  High heat of vaporization – changing from a liquid to a gas requires large amounts of heat  Polar solvent properties – dissolves ionic substances, forms hydration layers around large charged molecules, and serves as the body’s major transport medium

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Properties of Water  Reactivity – is an important part of hydrolysis and dehydration synthesis reactions  Cushioning – resilient cushion around certain body organs

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Acids and Bases  Acids release H + and are therefore proton donors HCl  H + + Cl –  Bases release OH – and are proton acceptors NaOH  Na + + OH –

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Acid-Base Concentration (pH)  Acidic solutions have higher H + concentration and therefore a lower pH  Alkaline solutions have lower H + concentration and therefore a higher pH  Neutral solutions have equal H + and OH – concentrations

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Acid-Base Concentration (pH)  Acidic: pH 0–6.99  Basic: pH 7.01–14  Neutral: pH 7.00 Figure 2.12

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Buffers  Systems that resist abrupt and large swings in the pH of body fluids  Carbonic acid-bicarbonate system  Carbonic acid dissociates, reversibly releasing bicarbonate ions and protons  The chemical equilibrium between carbonic acid and bicarbonate resists pH changes in the blood

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Organic Compounds  Molecules unique to living systems contain carbon and hence are organic compounds  They include:  Carbohydrates  Lipids  Proteins  Nucleic Acids

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Carbohydrates Figure 2.13a  Contain carbon, hydrogen, and oxygen  Their major function is to supply a source of cellular food  Examples:  Monosaccharides or simple sugars

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Carbohydrates Figure 2.13b  Disaccharides or double sugars

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Carbohydrates Figure 2.13c  Polysaccharides or polymers of simple sugars

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Lipids  Contain C, H, and O, but the proportion of oxygen in lipids is less than in carbohydrates  Examples:  Neutral fats or triglycerides  Phospholipids  Steroids

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Neutral Fats (Triglycerides) Figure 2.14a  Composed of three fatty acids bonded to a glycerol molecule

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Other Lipids Figure 2.14b  Phospholipids – modified triglycerides with two fatty acid groups and a phosphorus group

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

Other Lipids Figure 2.14c  Steroids – flat molecules with four interlocking hydrocarbon rings

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Representative Lipids Found in the Body  Neutral fats – found in subcutaneous tissue and around organs  Phospholipids – chief component of cell membranes  Steroids – cholesterol, sex hormones, and adrenal cortical hormones  Fat-soluble vitamins – vitamins A,D, E, and K  Lipoproteins – transport fatty acids and cholesterol in the bloodstream

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Amino Acids  Building blocks of protein, containing an amino group and a carboxyl group  Amino acid structure

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Amino Acids Figure 2.15a-c

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Protein Figure 2.16  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Structural Levels of Proteins  Primary – amino acid sequence  Secondary – alpha helices or beta pleated sheets  Tertiary – superimposed folding of secondary structures  Quaternary – polypeptide chains linked together in a specific manner

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Structural Levels of Proteins Figure 2.17a-c

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Structural Levels of Proteins Figure 2.17d, e

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fibrous and Globular Proteins  Fibrous proteins  Extended and strandlike proteins  Examples: keratin, elastin, collagen, and certain contractile fibers  Globular proteins  Compact, spherical proteins with tertiary and quaternary structures  Examples: antibodies, hormones, and enzymes

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Protein Denuaturation Figure 2.18a  Reversible unfolding of proteins due to drops in pH and/or increased temperature

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Protein Denuaturation Figure 2.18b  Irreversibly denatured proteins cannot refold and are formed by extreme pH or temperature changes

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Enzymes  Most are globular proteins that act as biological catalysts  Holoenzymes consist of an apoenzyme (protein) and a cofactor (usually an ion)  Enzymes are chemically specific  Frequently named for the type of reaction they catalyze  Enzyme names usually end in -ase  Lower activation energy

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Characteristics of Enzymes Figure 2.19

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Enzyme Action  Enzyme binds with substrate  Product is formed at a lower activation energy  Product is released

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Enzyme- substrate complex (E–S) Internal rearrangements leading to catalysis Free enzyme (E) Active site Enzyme (E) Substrates (s) Amino acids H20H20 Peptide bond Dipeptide product (P) Mechanism of Enzyme Action Figure 2.20

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nucleic Acids  Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus  Their structural unit, the nucleotide, is composed of N-containing base, a pentose sugar, and a phosphate group  Five nitrogen bases contribute to nucleotide structure – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U)  Two major classes – DNA and RNA

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Deoxyribonucleic Acid (DNA)  Double-stranded helical molecule found in the nucleus of the cell  Replicates itself before the cell divides, ensuring genetic continuity  Provides instructions for protein synthesis

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Structure of DNA Figure 2.21a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Structure of DNA Figure 2.21b

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Ribonucleic Acid (RNA)  Single-stranded molecule found in both the nucleus and the cytoplasm of a cell  Uses the nitrogenous base uracil instead of thymine  Three varieties of RNA: messenger RNA, transfer RNA, and ribosomal RNA

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.40 Information transfer from DNA to RNA to polypeptide. DNA: DNA base sequence (triplets) of the gene codes for synthesis of a Particular polypeptide chain DNA molecule Gene 1 Gene 2 Codons Triplets Anticodon tRNA Stop; detach Start translation mRNA: Base sequence (codons) of the transcribed mRNA tRNA: Consecutive base sequences of tRNA anticodons recognize the mRNA codons calling for the amino acids they transport Polypeptide: Amino acid sequence of the polypeptide chain Gene

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.37 Translation is the process in which genetic information carried by an mRNA is decoded in the ribosome to form a particular polypeptide. Slide 1 Elongation. Amino acids are added one at a time to the growing peptide chain via a process that has three repeating steps. 2 Amino acid corresponding to anticodon Template strand of DNA Pre-mRNA mRNA Nucleus (site of transcription) Amino acid corresponding to anticodon Met tRNA The correct amino acid is attached to each species of tRNA by a synthetase enzyme. Ile Pro Leu tRNA anticodon Polypeptide Ile Pro Complementary mRNA codon Leu New peptide bond Released tRNA Pro Leu Ile A P E A P E Peptide bond formation. The growing polypeptide bound to the tRNA at the P site is transferred to the amino acid carried by the tRNA in the A site, and a new peptide bond is formed. 2b 2c Translocation. As the entire ribosome translocates, it shifts by one codon along the mRNA: The unloaded tRNA in the P site is moved to the E site and then released. The tRNA in the A site moves to the P site. The next codon to be translated is now in the empty A site ready for step 2a again. Direction of ribosome movement Polypeptide Release factor Stop codon P E Termination. When a stop codon (UGA, UAA, or UAG) arrives at the A site, elongation ends. Release of the newly made polypeptide is triggered by a release factor and the ribosomal subunits separate, releasing the mRNA. 3 Codon recognition. The anticodon of an incoming tRNA binds with the complementary mRNA codon (A to U and C to G) in the A site of the ribosome. 2a Small ribosomal subunit Start codon A site P site E site Initiation. Initiation occurs when four components combine: A small ribosomal subunit An initiator tRNA that carries the amino acid methionine The mRNA A large ribosomal subunit Once this is accomplished, the next phase, elongation, begins. 1 Initiator tRNA bearing anticodon Aminoacyl-tRNA synthetase Met Cytosol (site of translation) Met Newly made (and edited) mRNA leaves nucleus and travels to a free or attached ribosome for decoding. Methionine (amino acid) Large ribosomal subunit U A C U A C C C C U A U U U A A G G A P E GGC GGC GAU GAU G A U ACCCU A ACCGCUCUC ACUGGGU G A CC U GAUACCCUA G A U G G C G A C

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Adenosine Triphosphate (ATP)  Source of immediately usable energy for the cell  Adenine-containing RNA nucleotide with three phosphate groups

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Adenosine Triphosphate (ATP) Figure 2.22

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings How ATP Drives Cellular Work Figure 2.23

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings A substance that is very acidic may have a pH of 1 or 2. This means that the acidic substance __________.  has a high concentration of OH – ions  has an equal concentration of OH – and H + ions  has a low concentration of H + ions  has a high concentration of H + ions

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings A buffer resist a change in pH  True  False

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The four major organic compounds that comprise our bodies are __________.  water, salt, carbon, oxygen  proteins, carbohydrates, lipids, nucleic acids  amino acids, fats, sugars, DNA  carbon, hydrogen, oxygen, nitrogen

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The major building blocks of carbohydrates are __________.  amino acids  fats  nucleotides  monosaccharides

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The three subclasses of lipids include phospholipids, steroids, and __________.  fatty acids  glycerols  triglycerides  oils

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The major building block for proteins is __________.  amino acids  monosaccharides  triglycerides  nucleotides

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings An enzyme’s ____________ is the molecule upon which an enzyme acts.  active site  substrate  inhibitor  catalyst

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Increasing the concentration of an enzyme’s substrate (up to a point) would ___________ the reaction.  slow down  speed up  inhibit  destroy

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The major building blocks of nucleic acids are __________.  amino acids  DNA and RNA  nucleotides  sugars

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings The four DNA nucleotides are __________.  carbon, hydrogen, nitrogen, oxygen  protein, lipid, nucleic acid, carbohydrate  primary, secondary, tertiary, quaternary  adenine, thymine, cytosine, guanine