Chemistry of Cells

Objectives Describe the distinguishing characteristics of carbohydrates Describe the important biological functions of polysaccharides Explain what distinguishes lipids from other classes of biological macromolecules Describe the unique properties, building blocks and biological roles of fats, phospholipids and steroids Distinguish proteins from the other classes of macromolecules

Objectives Cont. List the biological functions which proteins perform Explain what determines protein conformation and why it is important Define denaturation and explain how proteins may be denatured Describe the characteristics that distinguish nucleic acids from the other classes of macromolecules Summarize the functions of nucleic acids

Objectives Cont. Briefly describe the three-dimensional structure of DNA Evaluate the importance of energy to living things Relate energy and chemical reactions Describe the role of enzymes in chemical reactions Identify the effect of enzymes on food molecules

MacroMolecules Macro = large Molecules = 2 or more atoms covalently bonded Usually referred to as polymers Like a chain Made from several repeating subunits The repeated subunits are called monomers Like links in a chain 3 of the 4 macromolecules are polymers of monomers

Making or Breaking Polymers The chemical mechanisms that cells use to make and break polymers are similar for all classes of macromolecules.

Making Polymers Monomers are connected by covalent bonds via a condensation reaction or dehydration reaction. One monomer provides a hydroxyl group and the other provides a hydrogen and together these form water. This process requires energy and is aided by enzymes.

Breaking Down Polymers The covalent bonds connecting monomers in a polymer are disassembled by hydrolysis. In hydrolysis as the covalent bond is broken a hydrogen atom and hydroxyl group from a split water molecule attaches where the covalent bond used to be. Hydrolysis reactions dominate the digestive process, guided by specific enzymes.

There are four of them. Carbohydrates Lipids Proteins Nucleic acids ☺ For each of these you will be expected to identify, describe, and differentiate between all four macromolecules. ☺You will also be expected to describe the biological importance of each macromolecule

Function of Carbohydrates Sugars, the smallest carbohydrates, serve as fuel and carbon sources Polysaccharides, the polymers of sugars, have storage and structural roles

Structure of Carbohydrates Monosaccharides generally have molecular formulas containing C,H and O in a 1:2:1 ratio. For example, glucose has the formula C6H12O6. Most names for sugars end in -ose. Monosaccharides are also classified by the number of carbons in the backbone.

Monosaccharides, particularly glucose, are a major fuel for cellular work. They are also building blocks for of other monomers, including those of amino acids (protein) and fatty acids (lipids). While often drawn as a linear skeleton, in aqueous solutions monosaccharides form rings.

2. Polysaccharides, the polymers of sugars, have storage and structural roles Polysaccharides are polymers of hundreds to thousands of monosaccharides joined together (What is a polymer?) One function of polysaccharides is energy storage it is hydrolyzed as needed. Other polysaccharides serve as building materials for the cell or whole organism.

Starch is a storage polysaccharide composed entirely of glucose monomers Great big chain of glucose molecules What would this look like? (Draw it.)

Biological Uses of Polysaccharides Plants store starch within plastids, including chloroplasts. Plants can store surplus glucose in starch and withdraw it when needed for energy or carbon. Animals that feed on plants, especially parts rich in starch, can also access this starch to support their own metabolism. Hey, this sounds like an objective!