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Chapter 3

BIOL 1010 Chapter 3: Ch. 3 notes

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University of Memphis
BIOL 1010

CH.3 3.1 Carbon Provides the Framework of biological molecules • A chemical compound containing the element carbon is called an organic molecule o Molecules containing carbon can form straight chains, branches, rings, balls and coils o They can do this because they can form up to four covalent bonds • Molecules consisting only of carbon and hydrogen are called hydrocarbons. o Hydrocarbons make good fuels: gasoline and propane • Carbon and hydrogen atoms both have similar electro-negativities, therefore electrons in these bonds are evenly distributed. o Because they are evenly distributed, hydrocarbons are nonpolar. • Functional groups have a C-H core, they also have definite chemical properties that they retain no matter where they occur. o Functional groups that are polar: hydroxyl, carbonyl (C=O), acidic carboxyl (COOH), phosphate (PO4), and basic amino (NH2) o Many of these groups participate in hydrogen bonding • Isomers are organic molecules that have the same molecular or empirical formula that exist in different forms. o If the difference is in the actual structure of their carbon skeleton, they are called structural isomers o Steroisomer have the same carbon skeleton but differ in how the groups attached to this skeleton are arranged in space. Enzymes in biological systems usually recognize only a single, specific steroisomer. ▪ A subcategory of stereoisomers, called enantiomers, are actually mirror images of each other. This is also called a chiral molecule. ▪ Chiral compounds are characterized by their effect on polarized light • 4 classes of macromolecules: o Carbohydrates: ▪ Starch. Glycogen-glucose-energy storage-potatoes ▪ Cellulose-glucose-structural support in plan cell walls- paper ▪ Chitin-modified glucose-structural support-crab shells o Proteins ▪ Functional-amino acids-catalysis; transport- hemoglobin ▪ Structural-amino acids-support-Hair o Nucleic Acids ▪ DNA-nucleotides-encodes genes-chromosomes ▪ RNA-nucleotides-needed for gene expression- messenger RNA o Lipids ▪ Fats- glycerol and three fatty acids-energy storage-butter ▪ Phospholipids- glycerol, two fatty acids, phosphate and polar R groups- cell membranes-phosphatidylcholine ▪ Prostaglandins- 5 carbon rings with 2 nonpolar tails-chemical messengers-prostaglndin E (PGE) ▪ Steroids-4 fused carbon rings- membranes; hormones-cholesterol ▪ Terpenes-long carbon chains-pigments; structural support- rubber • A polymer is a large molecule built by linking together a large number of small, similar chemical subunits called monomers. Lipids are the only ones that has a chain of only three subunits that consists of a long chain of C-H functional groups (fatty acid) • These chains are all built in the same way, assembled via chemical reactions termed dehydration reactions are broken down by hydrolysis reactions. • Dehydration reaction: o To form a covalent bond between two monomers, an –OH group is removed from one monomer, and a hydrogen atom (H) is removed from the other. o This chemical reaction is called condensation or a dehydration reaction because the removal of –OH and –H is the same as the removal of a molecule of water. o For every subunit added to a macromolecule, one water molecule is removed. • Hydrolysis reaction: o Reverse dehydration, a molecule of water is added instead or removed o A hydrogen atom is attached to one subunit and a hydroxyl group to the other, breaking a specific covalent bond in the macromolecule 3.2 Carbohydrates form both structural and energy storing molecules • Carbohydrate are a loosely defined group of molecules that all contain, carbon, hydrocarbon, and oxygen in the molar ratio 1:2:1. (CH2O)n • The simplest of the carbohydrate sugars are the monosaccharides. They are simple sugars that contain as few as 3 carbon atoms • Five carbon sugars ribose and deoxyribose are components of nucleic acids • The most important of the six-carbon monosaccharides for energy storage is glucose. Glucose has a 7 energy-storing C-H bonds. Glucose can exist in the alpha and beta forms • Fructose is a structural isomer that differs in the position of the carbonyl carbon (C=O); galactose is a steroisomer that differs in the position of –OH and –H groups relative to the ring. • Transport forms of sugars are commonly made by linking two monosaccharides together to form a disaccharide. Disaccharides serve as effective reservoirs of glucose because of the enzymes that normal use glucose in the organism can’t break the bond linking the two monosaccharide subunits. • In plants glucose instead forms a disaccharide with its structural isomer fructose. The resulting disaccharide is sucrose, sucrose is the form most plants use to transport glucose and is the sugar most humans eat. • In mammals, glucose is linked to its steroisomer galactose, forming the disaccharide lactose, or milk sugar. Many mammals supply energy to their young in the form of lactose. • Polysaccharides are longer sugar polymers made up of monosaccharides that have been joined through dehydration reactions. • Organisms store the metabolic energy contained in monosaccharides by first converting them into disaccharides, such as maltose. These are then linked together into insoluble storage polysaccharides called starches. 3.3 proteins are the tools of the cell • Proteins are the most diverse group of biological macromolecules, both chemically and functionally. • 7 catergories of protein functions 1. Enzume catalysis: enycmes are biological catalyst that facilitate specific chemical reactions. Encymes are #D globular proteins that fit snugly around the molecules they act on. This fit facilitates chemical reactions by stressing particular chemical bonds. 2. Defense: other globular proteins use their shapes to recognize foreign microbes and cancer cells. White blood cells destroy forign cells, and others make antibody proteins that attach to invading cells. 3. Transport: a variety of globular proteins transport small molecules and ions. Red blood cells contain the transport protein hemoglobin, which transports oxygen in the blood. On the surfaces of individual cells, membranes transport proteins help move ions and molecules across the membrane. 4. Support: protein fibers play many important structural roles. In humans, these fibers include keratin, the fibrin in blood clots, and collagen. The last one, collagen, forms the matrix of skin, ligaments, tendons, cartilage and bones. 5. Motion: muscles contract through the sliding motion of two kinds of protein filaments: actin and myosin. Proteins also play key roles in the cells cytoskeleton and in moving materials within cells. 6. Regulation: small proteins called hormones serve as intercellular messengers in animals, proteins also play many regulatory roles within the cell-turning on and shutting off genes, for example. Proteins also act as receptors for extracellular signals. 7. Storage: calcium and iron are stored in the body by binding as ions to storage proteins found in cells • Proteins are long linear polymers of amino acids. The sequence of the a
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