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Chapter 3 notes

by: Megan Smith

Chapter 3 notes Biol 1103k

Megan Smith
GPA 3.6

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this is chapter 3 notes from the book in biology
Introductory biology I
David blaustein
Class Notes
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This 11 page Class Notes was uploaded by Megan Smith on Monday February 1, 2016. The Class Notes belongs to Biol 1103k at Georgia State University taught by David blaustein in Summer 2015. Since its upload, it has received 39 views. For similar materials see Introductory biology I in Biology at Georgia State University.


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Date Created: 02/01/16
Date CHAPTER 3 – BIOLOGICAL MOLECULES 3.1 WHY IS CARBON SO IMPORTANT IN BIOLOGI CAL MOLECULES organic • Describes molecules that have a carbon backbone bonded to hydrogen Inorganic • Molecules lack carbon atoms (water and salt) or lack hydrogen atoms (carbon dioxide) • Far less diverse and generally much simpler than organic molecules A. The Unique Bonding Properties of Carbon are Key to the Complexity of Organic Molecules i. Atoms are unstable when their outermost electron shells are only partially filled ii. Depending on the number of vacancies in their shells, two atoms can share two, four, or six electrons o This can form a single, double, or triple covalent bond iii. A carbon atom can become stable by bonding with up to four other atoms or with fewer atoms by formi ng double or even triple bonds o Organic molecules can then assume complex shapes, including branched chains, rings, sheets, or helices. iv. Functional Groups o Commonly occurring combinations of atoms o Less stable than the carbon backbone and more likely to participate in chemical reactions o Table: Important Functional Groups in Biological Molecules 3.2 HOW ARE ORGANIC MOLE CULES SYNTHESIZED? Monomers • Small organic molecules that may bind chemically to other molecules to form polymers Polymers • When small organic molecules join to form longer molecules • Chains of monomers B. Biological Polymers are Formed by Removing Water and Split Apart by Adding Water i. Dehydration synthesis o “removing water put together” o The subunits of large biological molecules are usually joined by a chemical reaction called dehydration synthesis o A hydrogen ion (H+) is removed from one subunit and a hydroxyl ion (OH -) is removed from a second subunit o This leaves openings in the outer el ectron shells of atoms in the two subunits o These openings are filled when the subunits share electrons, creating a covalent bond that links them 2 o The hydrogen ion and the hydroxyl ion combine to form a molecule of water (H2O) ii. Hydrolysis o The reverse reaction of dehydration synthesis o “Water breaking apart” o breaks apart the molecule into its original subunits, with water donating a hydrogen ion to one subunit and a hydroxyl ion to the other iii. biological molecules fall into 4 general categories a. carbohydrates b. lipids c. proteins d. nucleotides/nucleic acids 3.3 WHAT ARE CARBOHYDRAT ES? Carbohydrates o Molecules are composed of carbon, hydrogen, and oxygen in the approximate ratio of 1:2:1 o All carbohydrates are a. Small b. Water-soluble sugars c. Polymers of sugars Monosaccharide o A carbohydrate consisting of just one sugar molecule o Also called “sugar” 3 Disaccharide o Two monosaccharides linked together o Also called “sugar” Polysaccharide o A polymer of many monosaccharides o Most do not dissolve in water at body temperature o Some serve as energy storage in molecules o Others strengthen the cell walls o Or form a supportive armor over bodies of insects, crabs, and their relatives A. There are Several Monosaccharides with slightly Different Structures i. Monosaccharides o Have a backbone of three to se ven carbon atoms o Most have both Hydrogen ( -H) and hydroxyl group ( -OH) attached to them ii. Sugar o When its dissolved in water it forms a ring usually o Common sugar is glucose iii. Glucose o Most common monosaccharide o Primary source of energy in cells iv. Many organisms s ynthesize other monosaccharides that have the same chemical formula s glucose but slightly different structures a. Fructose – plants b. Galactose – mammals v. Other monosaccharides o Ribose and deoxyribose § Have 5 carbons B. Disaccharides Consist of Two Monosaccharides Linked by Dehydration Synthesis i. Monosaccharides can be liked by dehydration synthesis to form disaccharides or polysaccharides ii. When energy required a. Disaccharides are broken apart by hydrolysis into their monosaccharide subunits b. Converted to glucose c. That is then broken down further to release energy stored in its chemical bonds C. Polysaccharides Are chains of monosaccharides 4 i. Starch o A polysaccharide o Plants use as an energy -storage molecule ii. Glycogen o Animals store this o Polymer of glucose molecules o Also a chain of glucose subunits, but more highly branched than starch iii. Cellulose o One of the most important structural polysaccharides o Makes up most of the walls of he living cells of plants o Makes up half the bulk of tree trunks iv. Chitin o Supportive outer coverings (exos keletons) of insects, crabs, and spiders o A polysaccharide in which the glucose subunits bear a nitrogen -containing functional group 3.4 WHAT ARE LIPIDS? Lipids o A diverse group of molecules that contain regions composed almost entirely of hydrogen and carbon o With non-polar carbon-carbon and cabon-hydrogen bonds o Some are used to store energy o Some form waterproof coverings o Some serve as the primary component of cellular membranes o Some are hormones o Three major groups a. Oils, fats, and waxes b. Phospholipids c. Steroids A. Oils, Fats, and Waxes a re Lipids Containing only Carbon, Hydrogen, and Oxygen i. Oils, fats, and waxes are built from only three types of atoms a. Carbon b. Hydrogen c. Oxygen o Each contain one or more fatty acid subunit ii. Fatty acid subunits 5 o Are long chains of carbon and hydrogen with a carbocyclic acid group ( - COOH) at one end iii. Fats and oils are formed by dehydration synthesis linking three fatty acid subunits to one molecule of *glycerol* • A three-carbon molecule iv. Triglycerides o Fats and oils chemical name v. Fats and oils o Used primarily as energy -storage molecules o Fats § are produced primarily by animals § the carbon of fatty acids are joined by single bonds, with hydrogen bonds at all other bonding sites o Oils are found primarily in the seeds of plants vi. Saturated o Fatty acids that contain as many hydrogen atoms as possible o Saturated fatty acid chains are straight and can pack closely together o Form a solid at room temperature vii. Unsaturated o Fatty acids with double bonds between some of the carbon atoms (fewer hydrogens) o Double bonds produce kinks in the fatty acid chains viii. Hydrogenation o Breaks some of the double bonds and adds hydrogens to the carbons o The process hydrogenation can convert liquid oils to solid ix. Waxes o Chemically similar to fats o Humans and most other mammals do not have th e appropriate enzymes to break them down o Highly saturated o Solid at normal outdoor temperatures B. Phospholipids Have Water -Soluble “Heads” and Water - Insoluble “Tails” i. Phospholipids o Plasma membrane that surround each cell contains several types of phospholipids o Similar to an oil, except one of the three fatty acids is replaced by a phosphate group attached to any of several polar functional groups that typically contain nitrogen 6 o Two dissimilar ends a. One end - two nonpolar fatty acid “tails” that are insoluble in water b. Other end – phosphate -nitrogen “head” that is polar and water soluble C. Steroids Contain Four Fused Carbon Rings i. Steroids o Composed of four rings of carbon atoms o All have similar, nonpolar, molecular structure with four fused carbon rings ii. Cholesterol o A steroid o A vital component of the membranes of animal cells o 2% of the human brain o used by cells to synthesize other steroids a. female sex hormone - estrogen b. male sec hormone – testosterone 3.5 WHAT ARE PROTEINS Proteins o Molecules composed of chains of amino acids o Estimated about 100,000 different types of proteins in human body Enzymes o Most cells contain hundreds of different enzymes o Proteins that promote specific chemical reactions Other Proteins o Keratin § Forms hair, horns, nails, scales, and feathers o Silk § Are secreted by silk moths and spiders to make cocoons and webs o Albumin § Found in egg white o Casein § Found in milk o Actin and Myosin § Contractile proteins that allow animal bodies to move A. Proteins are Formed from chains of Amino Acids i. Amino acids 7 o Proteins are polymers of amino acids o Joined by peptide bonds o All have the same fundamental structure a. Central carbon atom bonded to a hydrogen atom b. Nitrogen -containing amino group ( -NH2) c. Carbocyclic acid group ( -COOH) d. An “R” group that varies among differe nt amino acids ii. “R” group o gives each amino acid distinctive properties iii. Some amino acids are hydrophilic and water soluble because their “R” groups are polar iv. Others are hydrophobic, with nonpolar R groups that are insoluble in water v. The amino acid cysteine h as a sulfur-containing R group that can form covalent disulfide bonds o Disulfide bonds - play important roles in proteins C. Amino Acids Are joined by Dehydration Synthesis i. Proteins are formed by dehydration synthesis a. In proteins, the nitrogen in the amoino gr oup (-NH2) of one amino acid is joined to the carbon in the carboxylic acid group ( -COOH) of another amino acid by a single covalent bond b. Water is liberated ii. This bond is called a peptide bond iii. The resulting chain of two amino acids is called a peptide o A term used to relatively short chains of amino acids o Additionally, amino acids are added, one by one, until a polypeptide chain is complete iv. A protein consists of one or more polypeptide bonds D. A Protein can have as many as four levels of structure i. Interactions among amino acid R groups can cause twists, folds, and interconnections that give proteins their three dimensional structure ii. For organized levels of protein structure are possible: a. Primary b. Secondary c. Tertiary d. Quaternary iii. Primary structure o The sequence of amino acids in a protein 8 iv. The specific amino acids sequences cause polypeptides to assume simple, repeating secondary structures: a. A helix b. A pleated sheet o These are maintained by hydrogen bonds between the polar portions of amino acids v. Helix o The coiled, springlike secondary structure vi. Holding the turns of the coils together a. Hydrogen bonds that form between the oxygen atoms of the cardinal functional groups (with slightly negative charges) b. The hydrogens of the amino functional groups (with slightly p ositive charges) vii. Other proteins, such as silk o Contain polypeptide chains that repeatedly fullback upon themselves, with hydrogen bonds holding adjacent segments of the polypeptide together and a secondary pleated sheet arrangement. viii. Tertiary structures o Many proteins are contorted into these structures o They’re origami folds are determined by: a. the proteins the secondary structure b. its environment ix. quaternary structure o occurs in certain proteins that contain: a. individual polypeptides linked by hydrogen bonds b. disulfide bonds c. by attractions between oppositely charged portions of different amino acids o Each of the four polypeptides holds an iron containing organic molecule called a heme group, which can bind one molecule of oxygen E. The functions of proteins are related to their three-dimensional structures i. within a protein, the exact position in number of amino acids very specific R groups determined both: a. the structure of the protein b. its biological function ii. Denatured o a proteins normal three dimensional str ucture is altered while leaving the primary structure intact 9 o a denatured protein have different properties and will no longer performance its function 3.6 WHAT ARE NUCLEOTIDES AND NUCLEIC ACIDS Nucleotide o A molecule with a three part structure a. a five carbon sugar b. a phosphate functional group c. a nitrogen containing base Bases o I’ll have carbon and nitrogen items linked in rings, with functional groups attached to some of the carbon atoms Nucleotides o Fall into two general classes a. Deoxyribose nucleotides b. ribose nucleotides o this depends on which type of sugar they contain The bases in deoxyribose nucleotides: a. adenine b. guanine c. cytosine d. thymine The bases in ribose nucleotides a. adenine b. guanine c. cytosine d. uracil Nucleotide may function as: a. energy carrier molecules b. subunits of polymers called nucleic acids A. nucleotides act as energy carriers intracellular messengers i. Adenosine triphosphate (ATP) o A ribose nucleotide with three phosphate functional groups o ATP stores energy and bonds between its phosphate g roups o then releases energy when the bond linking the last phosphate to the ATP molecule is broken 10 o this energy is then available to drive energy demanding reactions such as linking amino acids to form proteins ii. the ribose nucleotide cyclic adenosine mono phosphate (cAMP) o ask as a messenger molecule himself iii. other nucleotides (NAD+ and FAD) are known as electron carriers because they transfer energy in the form of higher -energy electrons A. DNA and RNA, The Molecules of heredity, Are nucleic acids i. Nucleic acids o Single nucleotide (monomers) maybe strung together and long chains by dehydration synthesis, forming polymers called nucleic acids o an oxygen Adam in the phosphate functional group of one nucleotide is covalently bonded to the sugar of the next ii. deoxyribonucleic acid (DNA) o can contain millions of nucleotides o a DNA molecule consists of two strands of nucleotides entwined in the form of a double helix and linked by hydrogen bonds iii. ribonucleic acid (RNA) o Single stranded chains of ribose nucleotides o copied from the DNA o Direct the synthesis of proteins 11


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