9/27/2015. Number of carbon atoms Monosaccharide Category. Ex: glyceraldehyde Important in cellular respiration. 3 triose

Transcription

1 Biomolecules Biology 102 Lecture 4: Biomolecules Molecules that make up living things Based on carbon-carbon bonds Contain other elements (H, O, N, P, S) Simplest organic molecules are the hydrocarbons Contain only C and H Non-polar Soluble in water?? Biomolecules are modified hydrocarbons Contain functional groups that change the chemical properties of the molecule Biomolecules Biomolecules 4 broad categories of biomolecules Biomolecules All biomolecules are built in the same fundamental way, regardless of complexity Carbohydrates Make up less than 3% of human body weight Much more prevalent in plants Made of exclusively C, H, O Ratio of 1:2:1 or CH 2 O (= carbo-hydrate) 1

2 Carbohydrates Monosaccharides Simple carbohydrates = sugars Monosaccharides In categories based on number of carbons Number of carbons determines beginning of category name Most sugar names end in -ose Number of carbon atoms Monosaccharide Category 3 triose 4 tetrose 5 pentose Biologically Relevant Ex: glyceraldehyde Important in cellular respiration Ex: D-erythrulose Used in some self-tanners Reacts with aa in skin and turns brown Ex: ribose Building block for RNA 6 hexose Ex: glucose Main source of cellular fuel 7 heptose Ex: sedoheptulose Intermediate in lipid A biosynthesis Question What is the chemical formula for a hexose sugar? Hexose Sugars Dozens of hexose sugars exist All have the same chemical formula Differ in the arrangement of atoms Therefore also shape, enzymes, absorbability Termed structural isomers Hexose Sugars Dozens of hexose sugars exist All have the same chemical formula Differ in the arrangement of atoms Therefore also shape, enzymes, absorbability Termed structural isomers Enzymes Hexose Sugars 2

3 Can also exist in ring form Atoms are reorganized, but formula stays the same Reversible Hexose Sugars Disaccharides Two monosaccharides bound together Disaccharides Disaccharides More efficient way to store energy Commonly encountered in our diets Require enzymatic digestion to be absorbed Disaccharide Monosaccharide Units Digested into Type Monomers of Bondby Enzyme Sucrose glucose and fructose 1-2 sucrase glycosidic Lactose galactose and glucose 1-4 lactase glycosidic Maltose glucose and glucose 1-4 maltase glycosidic Sucrose Lactose Maltose Polysaccharides Polysaccharides Dehydration synthesis can be repeated indefinitely Builds polysaccharides Can be very large! Polysaccharide Organism Function Starch plants Energy source for plant (and us when we eat it) Structure glucose monomers 1-4α linkage with some 1-6α for branching Digested into Monomers by Enzyme Amylase Example: glycogen Glycogen animals and fungi Very efficient glucose storage in liver and muscle glucose monomers 1-4α linkage with more 1-6α for more branching Glycogen phosphorylase Cellulose plants Structural component of cell walls Indigestible to humans (fiber) glucose monomers 1-4 β linkage with no branching N/A Chitin arthropods and fungi Structural component of cell walls and exoskeleton - analagous to keratin 3

4 Primary functions of carbohydrates 1. Storage/source of energy 2. Structural support 3. Component of co-enzymes 4. Part of RNA/DNA Carbohydrates 5. Biological recognition Glycocalyx Artificial grouping of biomolecules Not based on common structure Based on common insolubility in water Polarity? Lipids Need special transport mechanism Made up of C and H with very little oxygen Includes: Fats Waxes Sterols Fat-soluble vitamins Lipids Long, unbranched hydrocarbon chains Carboxyl group at one end Polarity?? Fatty Acids Saturated or unsaturated with what? Carbon Saturation Carbon Saturation Saturated or unsaturated with hydrogens Carbon needs 4 bonds to be stable Has 3 options to get them C C C In a fatty acid, almost all carbons are bound to 2 other carbons This builds the backbone of the fatty acid chain C C C 4

5 Carbon Saturation If all bonds between carbons are single, a greater number of hydrogens can bind This is said to be a saturated fatty acid one with the maximum number of hydrogens H H H C C C Saturated Fatty Acids Every carbon has 4 single bonds 2 with carbons 2 with hydrogens (except at the ends) H H H Saturated Fatty Acids Very stable not prone to rancidity Straight chains stack tightly Solid at room temperature Found in butter, animal fats, eggs, coconut oil, palm oil and in your body! Unsaturated Fatty Acids Carbons can also form double bonds Leaves less room for hydrogen Said to be unsaturated Unsaturated Fatty Acids Double bonds prone to rancidity Bent chains do not stack as tightly Liquid at room temperature Found in plant oils Unsaturated Fatty Acids One double bond = monounsaturated Olive, avocado > 1 double bond = polyunsaturated Corn, soy, peanut, Canola 5

6 An Unfortunate Discovery In the early 1900s, Proctor & Gamble cornered the market on cottonseed oil An Unfortunate Discovery Oil hydrogenation turns double bonds into single bonds Electricity meant people weren t using candles much anymore what to do with the oil? An Unintended Consequence Don t want to completely saturate oil Turns waxy and gross Instead only partially hydrogenate, which changes some of the double bonds from cis to trans An Unintended Consequence Changes shape to something not found in nature An Unintended Consequence Shortening Changes the shape Fat behaves more like it s saturated 6

7 Cheap Trans Fatty Acids Lend buttery quality to processed foods Used in crackers, cookies, pie crusts, French fries, fried chicken, even coffee creamer Less prone to rancidity than vegetable oil, lard, or butter Extend shelf life of products Trans Fatty Acids Shape doesn t occur in nature No enzymes that break it down in us, or in bacteria! Solid at room temperature and at body temperature! Body doesn t know how to deal with it Highly inflammatory = immune response You re probably eating more than you think Trans Fat Free?? Don t Buy It!! Cis Fatty Acids So Which Fat Is Healthiest? Shape does occur in nature Prone to oxidation But at least your body knows what to do with it! Cis fat 7

8 Form when fatty acids bind to glycerol Most common dietarily = triglycerides 3 fatty acids Glycerides + 3H 2 O Triglycerides in the Body Very efficient long-term energy storage Large molecules = high potential energy Gram for gram more than twice the energy of carbohydrates Fat deposits under skin and throughout body cut heat loss by 2/3 Protects and cushions organs Virtually non-polar allows for more efficient storage Problem: We have too much of it! Phospholipids Modified triglycerides One fatty acid replaced with a phosphorus and nitrogen-containing functional group Phospholipids Phosphorus group is polar = hydrophilic Fatty acids are non-polar = hydrophobic Allows non-polar molecules to associate with water Extremely important in cell membrane structure More about them later Synthesized by all living organisms Humans make in liver Cholesterol Dietary cholesterol esterified and poorly absorbed High cholesterol usually due to metabolic disregulation rather than dietary sources Exception: oxidized cholesterol 8

9 Important molecule! Component of cell membranes 50% dry weight Adds rigidity Cholesterol Needed for growth and development Breastmilk is extremely high in cholesterol Critical for myelin production Needed to make sterols Made in adrenals Functions Steroid Hormones Chemical communication Calcium homeostasis (calcitrol) Regulate sperm/egg development and sexual function Steroid Hormones Male hormones, including testosterone, are also called anabolic steroids Critical for calcium absorption Ongoing research implicates it in multiple biological processes We lack the enzyme to make it from cholesterol! Require sunlight Vitamin D 1. Structural components of cell membranes 2. Energy reserves 3. Insulation and protection 4. Vitamin D synthesis (calcium absorption) 5. Steroid hormones Functions of Lipids Proteins Most varied of the biomolecules Make up more than half the dry weight of cells Categorized by function Others we didn t talk about Bile salts (lipid digestion) Eicosanoids (signaling molecules) 9

10 Storage Protein Functions Energy for embryo, young, other organisms Structure Protein Functions Macroscopic examples: tendons, ligaments, hair, nails (collagen, keratin) Cellular level examples: actin, tubulin Transport Protein Functions Proteins that carry other molecules from one place to another Examples: hemoglobin, kinesins Catalysis Protein Functions Enzymes are proteins Defense Protein Functions Antibodies, interferons produced in response to infection Protein Functions Coordination and growth (signaling) Hormones (e.g. insulin, growth hormone) Communication (receptors) 10

11 Buffering Protein Functions Proteins are both acids and bases at the same time Protein building blocks= amino acids 20 amino acids Proteins Can be arranged to form an astounding variety of proteins Much the way only 26 letters make thousands of words Protein Structure Protein function depends on 4 up to levels of structure Primary number and order of amino acids Secondary local folding patterns Tertiary overall 3D folding Quaternary interaction of 2 or more fully assembled proteins Primary structure depends on peptide bonds Very strong and stable Require a chemical change to break All other levels of structure depend on interactions Hydrogen bonds Relatively weak Can be broken by changes in temperature, ph Disulfide bonds Protein Structure Example: Hemoglobin Example: Sickle Cell Anemia Normal RBC Sickle RBC 11

12 Sickle Cell Anemia Caused by defect in 1 structure Leads to defect in 4 structure Protein Structure Biological activity of a protein highly dependent on shape Changes in shape = denaturation Protein shape is maintained by hydrogen bonds Anything that alters hydrogen bonds can denature a protein Heat, pressure, ph, heavy metals, alcohol, UV light PRIMARY STRUCTURE IS UNAFFECTED BY DENATURATION Sometimes denaturation is reversible (sometimes not) Denatured protein May fold inappropriately Sickle cell anemia May not be functional Cystic fibrosis May disrupt other cellular functions Prions Denaturation Primary functions of proteins 1. Storage 2. Structure 3. Transport 4. Catalysis (enzymes) 5. Defense 6. Signaling 7. Buffering Proteins Two primary types Nucleic Acids Deoxyribonucleic acid (DNA) Determines inherited characteristics Contains information for protein building Regulates all areas of cellular metabolism Two primary types Ribonucleic acid (RNA) Nucleic Acids 3 types work together to make proteins based on information in DNA 12

13 Several functions in cell Energy transfer Nucleic Acids ATP, NADH/NAD+ Information storage DNA stores all genetic, protein synthesis information Information transfer RNA gets information from DNA, takes it to cytoplasm Several functions in cell Protein synthesis Coordinated activity of 3 RNA types Cellular metabolism and cell communication NADH/NAD+ camp Nucleic Acids Monomer = nucleotide More complex than other monomers Phosphate Pentose sugar (ribose or deoxyribose) Nitrogenous base (1 of 5) Polymer = nucleic acid Nucleotides DNA = A G C T RNA = A G C U Nucleotide Bases Adenine nucleotide Structure of RNA Single-stranded polynucleotide Phosphate and sugar alternate in a backbone Bases project out at right angle Structure of DNA Two anti-parallel polynucleotide strands Complimentary base-pairing with hydrogen bonds Twisted into a double helix A LOT more on this later 13

14 One More Use For Nucleotides Used to shuttle energy within the cell Energy stored in covalent bonds Most universal energy carrier is ATP Adenosine triphosphate ATP When bonds between the phosphates are broken, energy is released Not as universal NAD 7X more energy-rich rich than ATP Carries energy as electrons 14