Lesson 2. Biological Molecules. Introduction to Life Processes - SCI 102 1

Transcription

1 Lesson 2 Biological Molecules Introduction to Life Processes - SCI 102 1

2 Carbon in Biological Molecules Organic molecules contain carbon (C) and hydrogen (H) Example: glucose (C 6 H 12 O 6 ) Inorganic molecules do not contain carbon Examples: water (H 2 O), salt (NaCl), carbon dioxide (CO 2 ) The unique bonding properties of carbon are key to the complexity of organic molecules Carbon has four electrons in its outer shell and can bond with up to four different atoms Functional groups: commonly occurring groups of atoms attached to carbon backbones that determine the characteristics of different molecules Introduction to Life Processes - SCI 102 2

3 Synthesizing Organic Molecules Monomers Individual subunits of biological molecules Polymers Long chains of monomers Biological polymers are formed by removing water and are split apart by adding water Dehydration synthesis is a chemical reaction that links monomers Water is removed during the reaction Hydrolysis is a chemical reaction splitting molecules into subunits Water is needed to complete the reaction Introduction to Life Processes - SCI 102 3

4 Synthesizing Organic Molecules Most biological molecules fall into one of four general categories Carbohydrates Lipids Proteins Nucleotides and nucleic acids Introduction to Life Processes - SCI 102 4

5 Carbohydrates: Monosaccharides There are several monosaccharides with slightly different structures Monosaccharides have one sugar molecule Glucose is a subunit of most polysaccharides Fructose is found in corn syrup Galactose is milk sugar Ribose and deoxyribose sugars are found in DNA and RNA Monosaccharides are also known as simple sugars They cannot be broken down by hydrolysis Introduction to Life Processes - SCI 102 5

6 Carbohydrates: Disaccharides Disaccharides consist of two monosaccharides linked by dehydration synthesis Disaccharides contain two monosaccharides linked by dehydration synthesis Disaccharides are broken into monosaccharides by hydrolysis Three common disaccharides are sucrose, lactose, and maltose Sucrose is made up of glucose and fructose Lactose is made up of glucose and galactose Maltose is made up of two glucose molecules Introduction to Life Processes - SCI 102 6

7 Carbohydrates: Polysaccharides Polysaccharides are chains of monosaccharides Polysaccharides are polymers of many monosaccharides Starch is a chain of glucose monomers used for energy storage in plants Glycogen is a chain of glucose monomers used for energy storage in animals Cellulose is a structural polysaccharide found in plants Chitin is found in the exoskeletons of insects, crabs, and spiders In digestion, larger polysaccharides are broken down into monosaccharides Polysaccharides are able to be broken down Example: Excess glucose molecules in the blood are stored in the liver as the polysaccharide glycogen. The polysaccharide of glycogen is broken down into glucose monosaccharides when blood sugar levels fall. Introduction to Life Processes - SCI 102 7

8 Lipids Oils, fats, and waxes are lipids containing only carbon, hydrogen, and oxygen Fats are formed by dehydration synthesis They contain three fatty acids and a glycerol molecule They are also known as triglycerides Fats and oils are used primarily as energy-storage molecules Fats and oils store the same energy with less weight than carbohydrates Saturated and unsaturated fats are different forms of fats and oils Saturated fats contain no double bonds and are solid at room temperature Unsaturated fats contain double bonds and are liquid at room temperature Waxes are similar to fats and are highly saturated Introduction to Life Processes - SCI 102 8

9 Saturated and Unsaturated Fat Saturated Fat Structure: Three fatty acids that are saturated with hydrogens and the tails are able to be straight and packed closely together Unsaturated Fat Structure: The fats are not fully saturated with hydrogens and contain bonds that cause bends or kinks in the fatty acid chains, so they cannot pack tightly together Introduction to Life Processes - SCI 102 9

10 Saturated and Unsaturated Fat Notice that in the saturated fat, there is no double bond in the carbon chain Notice that in the unsaturated fat, there is a double bond in the carbon chain (making it unsaturated) and that there is a bend in the bonding, causing an inability for the fats to get packed closely together Introduction to Life Processes - SCI

11 Lipids: Phospholipids Phospholipids have water-soluble heads and water-insoluble tails Phospholipids contain two fatty acids, one glycerol, and one phosphate group Fatty acid tails are hydrophobic (water insoluble) The phosphate group head is polar and hydrophilic (water soluble) They are a central component of cell membranes Introduction to Life Processes - SCI

12 Lipids: Steroids Steroids contain four fused carbon rings Cholesterol is an important component of animal cell membranes It is also an important component of hormones Cholesterol is used to synthesize bile Introduction to Life Processes - SCI

13 Trans Fat Trans fat An unsaturated fat that is created artificially A trans fat is formed when food manufacturers turn liquid oils into solid fats by adding hydrogen to vegetable oils Hydrogenation The process for making trans fat A solid fat is produced because by adding hydrogen, fatty acid chains are able to pack themselves together more tightly Government regulations Foods containing trans fat must be labeled appropriately Introduction to Life Processes - SCI

14 Proteins Proteins are formed from chains of amino acids Amino acids contain a central carbon and four functional groups Nitrogen-containing amino group ( NH 2 ) Carboxyl group ( COOH) Hydrogen ( H) The R-group is a variable group and gives each amino acid its distinctive properties Amino acids are joined by dehydration synthesis A peptide bond forms when an amino group of one amino acid is joined to a carboxyl group of another amino acid A polypeptide chain or protein consists of a long chain of amino acids Introduction to Life Processes - SCI

15 Proteins A protein can have as many as four levels of structure 1) Primary structure is the sequence of amino acids that make up the protein Different proteins have different sequences of amino acids 2) Secondary structure is due to interactions between hydrogen bonds of amino acids Helix arrangement is a coiled structure Pleated sheet arrangement happens when chains fold back upon themselves Introduction to Life Processes - SCI

16 Proteins A protein can have as many as four levels of structure 3) Tertiary structure is the three-dimensional configuration of the amino acid chain This level of structure is influenced by surrounding environment 4) Quaternary structure occurs in certain proteins when individual polypeptides are linked together by hydrogen bonds Example: hemoglobin composed of four peptides Introduction to Life Processes - SCI

17 Proteins The functions of proteins are related to their threedimensional structures Denatured proteins have their secondary and tertiary structures altered Denatured proteins cannot perform their designated functions Introduction to Life Processes - SCI

18 Proteins Many things are made of proteins, including: Enzymes (which are found in cells and help with chemical reactions) Keratin (forms hair, nails, horns, scales, feathers) Hormones (examples: insulin, growth hormones, adrenaline) Antibodies (substance in the body that fights infection and disease) Toxins (venom in snakes) Protein is also a nutrient in food Introduction to Life Processes - SCI

19 Nucleotides and Nucleic Acids Nucleotides act as energy carriers and intracellular messengers Nucleotides consist of a phosphate, a sugar, and a base Adenosine triphosphate carries energy from place to place within a cell Electron carriers transport energy DNA and RNA, the molecules of heredity, are nucleic acids Nucleic acids are long chains of subunits known as nucleotides The components are a 5-C sugar, a phosphate group, and a nucleotide base DNA (deoxyribonucleic acid) contains deoxyribose nucleotides (AGTC) RNA (ribonucleic acid) contains ribose nucleotides Introduction to Life Processes - SCI