Transcript Slide 1
RNA World Hypothesis • The RNA world hypothesis proposes that selfreplicating ribonucleic acid (RNA) molecules were precursors to current life, which is based on deoxyribonucleic acid (DNA), RNA and proteins. It is generally accepted that current life on Earth descends from an RNA world, although RNA-based life may not have been the first life to exist. Assignment: • Take 10 minutes and write out in a paragraph what the basic idea of the RNA World Hypothesis is. Use your own words in an original way. Read the previous paragraph again, roll it around in your head, then write your own fresh version. Objectives: 1. Summarize the characteristics of organic components 2. Distinguish between carbohydrates, lipids, and proteins 3. Describe the structure and function of nucleic acids and ATP. Organic Compounds • Organic compounds contain carbon atoms that are covalently bonded to other elements, typically Hydrogen, oxygen, and other carbon atoms. There are four principal classes of organic molecules found in living things • • • • Carbohydrates Lipids Proteins Nucleic acids Without these cells couldn’t function. Carbohydrates • Carbohydrates are organic compounds made of carbon, hydrogen, and oxygen, and are found in the proportion 1:2:1 Carbohydrates are a key source of Energy • They are found in large quantities in fruits, vegetables, and grains. Monosaccharide • Monosaccharides are the simplest of sugars. • Larger sugar molecules are built up by adding monosaccharides together to form longer chains. Disaccharides • Disaccharides are double sugars formed when two monosaccharides are attached together. • Such as sucrose and glucose, or common table sugar. Polysaccharides • Polysaccharides are chains of 3 or more monosaccharides such as starch, which is an example of a macromolecule (a large molecule made up of smaller molecules). • In organisms, polysaccharides function as store houses of energy. Glycogen and Starch • Glycogen is the polysaccharide that animals use to store energy • Starch is the polysaccharide that plants use to store energy • Lipids are also molecules composed of Carbon, hydrogen, and oxygen. • These include molecules such as fats, phospholipids, steroids, and waxes. Phospholipids • Phospholipids are important in the function of cell membranes, and create a lipid bilayer. Steroids • Steroids such as cholesterol are also found in cell membranes. • The plant pigment chlorophyll is also a lipid. FATS • Fats are lipids that store energy • A typical fat contains 3 fatty acids bonded to a glycerol molecule. Saturated Fats • Saturated fats, are saturated with hydrogen atoms. • Each carbon is bound to 2 hydrogens, the end carbons have 3 hydrogens attached. Saturated Fats • Most animal fats such as butter, lard, and the fatty part of steaks are saturated fats. • They are typically solid at room temperature. Unsaturated fats • Unsaturated fats some of the carbon atoms form double bonds, each with only one hydrogen atom, producing kinks in the molecule Unsaturated fats • Unsaturated fats mainly come from plants, and are usually liquid at room temperature. Proteins • Proteins are long chain molecules. • They are made up of chains of amino acids strung like pearls on a necklace. • The amino acids are connected by peptide bonds. Amino Acids • Amino acids are the building blocks of proteins. • There are 20 different amino acids found in proteins, each with a different chemical structure. Primary, Secondary, and Tertiary Structure of Proteins Proteins have a variety of functions in living organisms Enzymes • Enzymes promote chemical reactions, such as amylase which breaks down starches, and DNA synthase which builds DNA molecules. Nucleic acids • Nucleic acid is a long chain of smaller molecules called nucleotides. Nucleotides • Nucleotides have three parts: a sugar, a base, and a phosphate group. RNA • RNA- ribonucleic acid, consists of a single strand of nucleotides, and plays several roles in cell function, including the manufacture of proteins. DNA • DNA- Deoxyribonucleic acids- consists of two strands of nucleotides that spiral around each other forming a double helix. • This molecule stores hereditary information that can be used to make proteins.