The Structure and Function of Macromolecules Chapter 5

Goals Explain how polymers are built from monomers and vice versa. Identify the names, properties, functions, and examples of the 4 major groups of macromolecules Discuss the 4 levels of protein structure.

Polymers and Monomers Polymers are long chain molecules made of repeating subunits called monomers. Example: Starch is a polymer composed of glucose monomers Proteins are polymers composed of amino acid monomers

Making and Breaking Polymers Dehydration Synthesis creates polymers from monomers. Two monomers are joined by removing one molecule of water (dehydration) Hydrolysis occurs when water is added to split large molecules A polymer is separated into its monomers by adding water

Types of Macromolecules Carbohydrates Lipids Proteins Nucleic Acids

1. Carbohydrates Carbohydrates include both simple sugars (glucose, fructose, galactose, etc.) and polymers such as starch made from these and other subunits. All carbohydrates exist in a ratio of 1 carbon: 2 hydrogen: 1 oxygen or CH2O Ex) C6H12O6

Monosaccharides are the monomers of carbohydrates. “Simple sugars” Examples include glucose C6H12O6 and ribose C5H10O5 Notice the 1:2:1 ratio above A disaccharide is formed when dehydration synthesis joins two monosaccharides This covalent bond is called a glycosidic linkage Sucrose (table sugar) = glucose + fructose Polysaccharides are long polymers of monosaccharides. Examples are starch and glycogen (both storage), and cellulose (structural)

Dehydration Synthesis of Carbs

Functions of Polysaccharides Source of energy for your cells Energy Storage Starch is a storage polysaccharide found in plants (potatoes, fruits) Glycogen is a storage polysaccharide found in animals, vertebrate muscle, and liver cells Structural Support Cellulose is a major component of plant cell walls Chitin is found in the exoskeleton of arthropods, such as lobsters and insects and the cell walls of fungi It gives bugs their “crunch” Used for surgical thread

2. Lipids Lipids are all hydrophobic They aren’t polymers, as they are assembled from a variety of components. Examples: waxes, oils, fats, and steroids

Lipids: Fats Fats (also called triglycerides) are made up of a glycerol molecule and three fatty acid molecules Fatty acids include hydrocarbon chains of variable lengths. These chains are nonpolar and therefore hydrophobic Fatty acids vary in length (number of carbons) and in the number and locations of double bonds

Dehydration Synthesis of Fats

Saturated vs. Unsaturated Have no double bonds between carbons Tend to pack solidly at room temperature Are linked to cardiovascular disease Are commonly produced by animals Examples: butter and lard Unsaturated Have some C=C (carbon double bonds); this results in kinks Tend to be liquid at room temperature Are commonly produced by plants Examples: corn oil and olive oil

Lipids: Phospholipids Phospholipids make up cell membranes Have a glycerol (head), which is hydrophilic Have two fatty acid tails, which are hydrophobic Are arranged in a bilayer in forming the cell membrane. With the hydrophilic heads pointing toward the watery cytosol or extra-cellular environment The hydrophobic tails are sandwiched in between

Lipids: Steroids Steroids are made up of 4 rings fused together Cholesterol is a steroid It is a common component of cell membranes Estrogen and testosterone are steroid hormones They control the female and male reproductive systems

Functions of Lipids Fats Phospholipids Steroids Energy storage Fats store twice as many calories/gram as carbohydrates! Protection of vital organs and insulation. In humans and other mammals fat is stored in adipose cells. Phospholipids Cell membrane structure Steroids Hormones Cholesterol helps keep cell membranes flexible

3. Proteins Proteins are polymers made up of amino acid monomers Amino acids contain a central carbon bonded to a carboxyl group, an amino group, a hydrogen atom, and an R group (variable group or side chain which determines function) Peptide bonds link amino acids They are formed by dehydration synthesis The function of a protein depends on the order and number of amino acids

Dehydration Synthesis of Proteins H2O Carboxyl Group Amino Group Peptide Bond

Four Levels of Protein Structure The primary structure of a protein is its unique sequence of amino acids (polypeptide chain) Secondary structure consists of coils and folds in the polypeptide chain due to hydrogen bonding Alpha helix and Beta pleated sheet Tertiary structure is determined by interactions among various side chains (R groups) Quaternary structure results when multiple polypeptide chains come together forming a protein

More on Proteins… Protein shape is crucial to protein function. When a protein does not fold properly, its function is compromised. This can be the result of a single amino acid substitution, such as that seen in the abnormal hemoglobin, typical of sickle-cell disease Chaperonins are protein molecules that assist in the proper folding of proteins within cells. Denaturation occurs when a protein loses shape and ability to function because of heat, change in pH, or some other disturbance. (Not due to a mutation)

(Occurs because of base substitution) Sickle Cell Anemia (Occurs because of base substitution) C T G A Val-His-Leu-Thr-Pro-Glu-Glu-Lys C A T G U Val-His-Leu-Thr-Pro-Val-Glu-Lys

Proteins: Enzymes Enzymes are a type of protein that act as a catalyst to lower the activation energy or a reaction and speed it up Enzymes can perform their functions repeatedly, functioning as workhorses that carry out the processes of life

Functions of Proteins Structure – hair, nails, etc. Carriers – transport molecules through body Enzymes – chemical reactions Protect against disease Receive signals from outside cell Cell movement Function typically depends on its ability to recognize and bind to some other molecule.

4. Nucleic Acids Nucleic acids store and transmit hereditary information DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the two nucleic acids Their monomers are nucleotides Nucleotides are made up of three parts Nitrogenous base (adenine, thymine, cytosine, guanine, and uracil) Pentose (5 carbon) sugar (deoxyribose in DNA or ribose in RNA) Phosphate group

Pyrimidines vs. Purines Purines Pyrimidines

DNA vs. RNA DNA is the molecule of heredity – contains the code for amino acid sequence of proteins It is a double-stranded helix Its nucleotides are adenine, thymine, guanine, and cytosine Adenine nucleotides will hydrogen bond to thymine nucleotides, and cytosine to guanine RNA makes proteins It is single stranded Its nucleotides are adenine, uracil, cytosine, and guanine Note that there is no thymine

Function of Nucleic Acids DNA molecule of heredity contains the code for amino acid sequence of proteins RNA makes proteins