BIOL 1000 Chapter 3 The Molecules of Cells PDF

Chapter 3 The Molecules of Cells January 15, 2025 3:39 PM 3.1 Life's molecular diversity is based on the properties of carbon Carbon is the most commonly bonded atom, can form large and complex atoms Organic molecules carbon-based molecules, usually contain hydroge...

Chapter 3 The Molecules of Cells January 15, 2025 3:39 PM 3.1 Life's molecular diversity is based on the properties of carbon Carbon is the most commonly bonded atom, can form large and complex atoms Organic molecules carbon-based molecules, usually contain hydrogen ○ Carbon only has 4 valence electrons, allowing it to make four covalent bonds Methane - CH4 one of the simplest organic molecules Different shapes of molecules occur with double bonds, the shape of a molecule indicates its function ○ Carbon chains form the backbone of most organic molecules Isomer compounds with the molecular formula but different arrangements Hydrocarbons molecules consisting of ONLY carbon and hydrogen ○ A major component of petroleum - energy producer 3.2 A few chemical groups are key to the functioning of biological molecules Functional groups 5 specific configurations of atoms attached to the carbon backbone of organic molecules ○ Effects a molecule's function by participating in chemical reactions ○ Functional groups are polar, making them hydrophilic ○ Hydrophilic water loving and soluble in water ○ Hydroxyl group OH, called alcohol ○ Carbonyl group C=O ○ Carboxyl group C=O bonded to a hydroxyl group, carboxylic acids ○ Amino group N-2H, amines ▪ Amino acids contain and amino and carboxyl group ○ Phosphate group P-4O, called organic phosphates ▪ Involved in energy transfers of ATP ○ Methyl group CH3, a component of DNA that effects gene expression 3.3 Cells make large molecules from a limited set of small molecules Macromolecule a large molecule formed by joining smaller molecules ○ Carbohydrates, proteins, nucleic acids Monomer the subunit "building block" of a polymer Polymer a chain of monomers joined by covalent bonds after a dehydration reaction ○ Dehydration reaction a reaction that removes a molecule of water ▪ Ex: one monomer loses OH and another monomer loses H to remove a water molecule and form a covalent bond ○ Hydrolysis adding a water molecule to break down a polymer for cellular use ○ ** both hydrolysis and dehydration reactions require enzymes to make and break bonds** ○ Enzyme specialized macromolecules that speed up chemical reactions in cells ○ **the key to the great diversity of polymers is arrangement** 3.4 Monosaccharides are the simplest carbohydrates Carbohydrate a macromolecule consisting of monosaccharides, disaccharides, and polysaccharides ○ Monosaccharide a simple, single-monomer sugar - main fuel for cellular work ▪ Glucose C6H12O6 , a common monosaccharide, contains several hydroxyl and carbonyl groups ▪ Fructose C6H12O6, identical molecular formula as glucose but different arrangements, making them isomers □ ** isomers have different properties (fructose is sweeter than glucose) which affects how they react with other molecules ▪ 5- and 6-carbon sugars like glucose form ring shapes in aqueous solutions □ Simplified drawings may omit the carbon atoms at the ring's corners and show varying thickness to indicate the ring's flat structure with atoms extending above and below  BIOL - 1000 Page 1  3.5 Two monosaccharides are linked to form a disaccharide Disaccharide a sugar molecule consisting of two monosaccharides linked by a dehydration reaction ○ Ex: maltose - made of two glucose monomers, one monomer gives up a hydroxyl group and one monomer gives up a hydrogen atom. As H2O is released, the monomers are linked together ○ Most common disaccharide: sucrose (made of one glucose monomer and one fructose monomer) ▪ A source of energy 3.7 Polysaccharides are long chains of sugar units Polysaccharides a carbohydrate polymer of thousands of monosaccharides (simple sugars) linked together by dehydration reactions ○ Functions: storage molecules or structural compounds Starch a storage polysaccharide in plants, consisting of longs chains of glucose monomers ○ Coiled into a helical shape, may be branched or unbranched ○ Cells can withdraw glucose for energy from these macromolecules ○ Humans and animals have enzymes to hydrolyse starch to glucose Glycogen an extensively branched polysaccharide found in liver and muscle cells, used for glucose storage and energy (the animal version of starch) Cellulose a structural polysaccharide in plant cell walls, made of glucose monomers and linked by hydrogen bonds into cable-like fibrils ○ The most abundant organic compound on Earth ○ ** animals do not have enzymes to hydrolyze cellulose, therefore this is only found in plants** ▪ After being consumed by animals, cellulose is considered an "insoluble fiber" Chitin a structural polysaccharide in exoskeletons and the cell wall of fungi ** almost all carbohydrates are hydrophilic, making cotton towels very absorbent 3.8 Fats are lipids that are mostly energy-storage molecules Lipids an organic compound of carbon and hydrogen atoms linked together by non-polar covalent bonds, making this molecule hydrophobic ○ Fats, phospholipids, steroids - insoluble in water/hydrophobic ** differ from carbohydrates because they are smaller and made from different monomers** Fat a large lipid made from glycerol and fatty acids, with a main function of energy storage ( a gram of fat stores twice as much energy as a gram of polysaccharide) ○ ** the downside of energy-storage in the form of fat is amount of effort that is takes for an animal to "burn it off" ○ Glycerol made from three carbons, each with a hydroxyl group ○ Fatty acid made from a carboxyl group and a hydrocarbon chain (16-18 carbons in length) ▪ ** the non-polar C-H bonds in the hydrocarbon chain is why this molecule is hydrophobic ▪ Unsaturated fatty acid contains a hydrocarbon chain with one or more double covalent bonds □ Double bonds cause bends in the chain □ Most plant and fish fats are liquid at room temperature (referred to as oils) due to the hydrocarbon chains bending, so they can't pack closely together ▪ Saturated fatty acid a fatty acid without any double bonds in the hydrocarbon chain, has the max number of hydrogen atoms attached to its carbon atom (the carbons are "saturated") □ Most animal fats are solid at room temperature due to the hydrocarbon chains lacking double bonds, thus being able to pack closely together ▪ "partially hydrogenated oils" on a food label means that unsaturated fats have been converted into saturated fats be adding hydrogen □ ** the process of hydrogenation also created trans fats, a form of fat that is associated with health risks** ○ A synonym for fat is triglyceride in the medical field