Topic 3: Molecular Biology 3.2 Carbohydrates and Lipids Essen=al Understanding: Carbon, hydrogen and oxygen are used to supply and store energy.
Carbohydrates
CARBOHYDRATES CHO sugars Primarily consist of C, H, O Approximate Ratio of 1:2:1 Empirical or simplest formula for a carbohydrate is CH 2 O Energy Source Suffix - ose GLUCOSE, FRUCTOSE
Monosaccharides Simple sugars that comprise ALL CHO s All have the same chemical formula (C 6 H 12 O 6 ) Therefore called ISOMERS ( equal parts ) Isomers - having the same chemical composition but with different structural arrangement
Monosaccharides E.g. GLUCOSE (C 6 H 12 O 6 ) blood sugar A hexose sugar E.g. FRUCTOSE (C 6 H 12 O 6 ) Found in fruits, honey, some vegetables A pentose sugar Note: the molecular formula is the same but the shape of the ring and arrangement of the hydrogen and hydroxyl groups are different.
Disaccharides (di = two; saccharide = sugar) When 2 monosaccharides (monomers) combine chemically they form a disaccharide (dimer) 3 most common forms: 1. SUCROSE (table sugar) - glucose + fructose 2. MALTOSE (malt sugar; grain sugar) - glucose + glucose 3. LACTOSE (milk sugar) - glucose + galactose Like monosaccharides, they are soluble in water They cannot be stored in the body Glycosidic bond needs to be broken by hydrolysis to form simple sugars for energy release in cell respiration.
Polysaccharides (poly = many; saccharide = sugar) Long chains of many monosaccharides (monomers) joined together by glycosidic bonds to form a polysaccharide (polymer) 3 important polysaccharides (all are polymers of GLUCOSE) 1. STARCH - plant storage polysaccharide - a mixture of Amylose and Amylopectin 2. GLYCOGEN - animal storage polysaccharide - found in muscle and liver primarily - broken down very quickly to glucose for energy 3. CELLULOSE - in plants only - cannot be broken down by AMYLASE enzyme and thus cannot be digested in humans
- Straight chain - Few side branches - Plant source - Unbranched - Plant source - Highly branched - Many side branches - Animal Source
Main Functions of Carbohydrates Provide a quick, short term ENERGY source for all living organisms Structural role in plants (Cell Wall contains cellulose) Cell-Cell recognition by CHO on surface of cell membrane Storage compounds (starch and glycogen)
Lipids
LIPIDS Mixed group of HYDROPHOBIC compounds Insoluble in water Contains fats, oils, waxes, rubbers, sterols: Composed of C, H, and O (same as Carbs) Energy Storage (vs Carbs. - Energy Source ) C-H bond represents usable energy Lipids have double the C-H bonds of a Carbohydrate
1. Triglycerides (FATS and OILS) Commonly called FATS and OILS FATS - Solids at room temperature OILS - Liquid at room temperature Made up of glycerol and fatty acids Ra, Rb, Rc represent groups of carbon and hydrogen atoms in which the carbon atoms are amached to each other in an un-branched chain.
Glycerol Central component in fats and oils A three-carbon alcohol Contains three - OH hydroxyl groups Soluble in water (hydrophilic) Fatty Acids Have a Carboxyl group (-COOH), a methyl group (- CH 3 ) plus a chain of atoms (mostly C and H = hydrocarbons) Water insoluble (hydrophobic) Contain an even number of C-atoms (4-36)
2. Saturated Fatty Acids All bonds are single Number of atoms attached to each carbon is the maximum of 4 (thus is saturated ) Carboxyl group Methyl group
3. Unsaturated Fatty Acids One or more double bonds kinky! Methyl group MONOunsaturated Fatty Acid ONE double bond POLYunsaturated Fatty Acid TWO or more double bonds Carboxyl group
Hydrogena=on Heavily processed foods, many polyunsaturated fats are hydrogenated (fully or par=ally) as part of processing eliminates the kinks by removing the double bonds and filling spaces with hydrogen (hence hydrogena=on ) Hydrogenated (ouen par=ally) straightened famy acids Naturally curved famy acids
Naming FaMy Acids From Pearson Higher Level Biology Text
2. Phospholipids Major constituent of cell membranes ( lipid bilayer ) Precursor of prostaglandins Short-lived hormones that operate close to home ie. Uterine smooth muscle contraction associated with birthing ie. Found in seminal fluid; decreases female immune response to sperm
Structure Similar to triglycerides HOWEVER one of the three fatty acid is replaced by a phosphate functional group Hydrophillic Head Hydrophobic Tails Legend: Phosphate Group - ORANGE FaMy Acid Groups - BLUE Glycerol - RED
3. Steroids Cholesterol component on cell membranes in animals and functions to moderate membrane fluidity Bile Salts Help to emulsify dietary fats Hormones (estrogen and testosterone) Vitamine D Aids in calcium uptake by bones
Structure Based on a molecules with four fused carbon rings Each steroid differs by arrangements in the rings and by functional group attached to it
Low Density Lipoproteins (LDL) bad cholesterols LDL carries cholesterol from liver to cells Used as a structural component of cell membranes or converted to steroid hormones Too much LDL is associated with arteriosclerosis High Density Lipoproteins (HDL) good cholesterols Acts like a cholesterol scavenger so excess cholesterol can be removed and converted to bile acids and excreted through digestive tract
Function of Cholesterol Structural component of cell membranes Essential component of myelin sheath that insulates neurons Precursor for lipid soluble vitamins (ADEK) Precursor for steroid hormones