Concept 5.1 Macromolecules are polymers, built from monomers

What is a polymer? What is a monomer?

A polymer is a long chain-like molecule, consisting of many similar or identical building blocks linked by covalent bonds. A monomer is a smaller molecule that serves as the building blocks of polymers.

Most monosaccharides are some multiple of (CH2O). For example, ribose is a 5-carbon sugar with the formula C5H10O5. It is a pentose sugar. (From the root penta-, meaning five.) What is the formula of a hexose sugar?

C6H12O6

Here are the three hexose sugars. Label each of them. Notice that all sugars have the same two functional groups. Name them:

C=O carbonyl group —OH hydroxyl group

The large molecules of all living things fall into just four main classes. Name them.

Carbohydrates, Lipids, Proteins, Nucleic Acids

Circle the three classes that are called macromolecules. Define macromolecule.

Carbohydrates, Proteins, Nucleic Acids Macromolecules are extremely large on the molecular scale, sometimes consisting of thousands of atoms.

Example

G protein-coupled receptors; tyrosine kinase receptors

Example

Globular transthyretin protein, collagen, hemoglobin

fructose

Glucose + fructose form sucrose

starch

Has 1-4 B glucose linkages

Why can you not digest cellulose? What organisms can?

Humans cannot digest cellulose because they lack the enzyme that can hydrolyze its beta linkages. Humans do posses enzymes that digest starch by hydrolyzing its alpha linkages; however, these enzymes cannot hydrolyze the beta linkages of cellulose because of the distinctly different shapes of these two molecules.

Example

Protein of hair Protein of spider web

Example

Proteins embedded in the plasma membranes; aquaporins; hemoglobin

What is represented by R? How many are there?

R refers to the side chains of amino acids. There are 20.

Function

Response of cell to chemical stimuli

Here is a figure that shows the structure of a phospholipid. Label the sketch to show the phosphate group, the glycerol, and the fatty acid chains. Also indicate the region that is hydrophobic and the region that is hydrophilic.

See page 76 in your text for the labeled figure

Some people refer to this structure as three hexagons and a doghouse. What is it?

See page 77 in your text for the labeled figure. Cholesterol, a steroid

To summarize, a phospholipid has a glycerol attached to a phosphate group and two fatty acid chains. The head is hydrophilic, and the tail is hydrophobic. Now, sketch the phospholipid bilayer structure of a plasma membrane. Label the hydrophilc heads, hydrophobic tails, and location of water.

See page 77 of your text for the labeled figure.

The monomers of proteins are amino acids. Sketch an amino acid here. Label the alpha or central carbon, amino group, carboxyl group, and R group.

See page 78 in your text for the labeled figure.

Study the figure. See if you can understand why some R groups are nonpolar, some polar, and others electrically charged (acidic or basic). If you were given an R group, could you place it in the correct group? Work on the R groups until you can see common elements in each category.

See page 79 in your text for the labeled figure.

Enzymes are globular proteins that exhibit at least tertiary structure. As you study Figure 5.20 in your text, use this figure to identify and explain each interaction that folds this protein fragment.

See page 83 in your text for the labeled figure. Hydrophobic interaction: amino acids with hydrophobic R groups end up in clusters at the core of the protein, out of contact with water. Van der Waals interaction: transient interactions between R groups Hydrogen Bond: weak bonds between the hydrogen of one R group and the oxygen or nitrogen of another R group Disulfide Bridge: links between the sulfhydryl groups of two cysteine amino acids, sulfur to sulfur Ionic Bond: bonds between an R group that is positively charged and an R group that is negatively charged These interactions tend to fold an amino acid chain into a distinctive three-dimensional form

Do you remember when, in Chapter 4, we said, "To change the structure, change the function"? Explain how this principle applies to sickle-cell disease. Why is the structure changed?

See page 84 of your text for the labeled figure. Sickle-cell disease is an inherited blood disorder caused by the substitution of one amino acid (valine) for the normal one (glutamic acid) at a particular position in the primary structure of hemoglobin, the protein that carried oxygen in red blood cells. This changes the typical three-dimensional shape of hemoglobin. Normal red blood cells are disk-shaped, but in sickle-cell disease, the abnormal hemoglobin molecules tend to crystallize, deforming some of the cells into sickle shapes.

Chaperone proteins or chaperonins assist in the proper folding of proteins. Annotate this figure to explain the process.

See page 85 of your text for the labeled figure. From Left to Right: 1. An unfolded polypeptide enters the cylinder from one end. 2. The cap attaches, causing the cylinder to change shape in such a way that it creates a hydrophilic environment for the folding of the polypeptide. 3. The cap comes off, and the properly folded protein is released.

Concept 5.5 Nucleic acids store, transmit, and help express hereditary information

The nucleic acids DNA and RNA will be the core topics of Chapter 17. For now, you should just review the general functions and know the components.

Why are the strands said to be antiparallel?

The strands are said to be antiparallel because they run in opposite 5' 3' directions from each other.

Study your sketch. Why are the tails all located in the interior?

The tails are in contact with each other and remote from water because they are hydrophobic.

Have you noticed that all the sugars end in -ose? This root word means

sugar

To summarize, when two monomers are joined, a molecule of

water is always removed.

lactose

"Milk sugar"

polypeptide

:A polymer of many amino acids linked by a peptide bond. See page 80 of your text for the labeled figure.

peptide bond

A covalent bond in which two amino acids are joined by a dehydration reaction.

What is a glycosidic linkage?

A glycoside linkage is a covalent bond formed between two monosaccharides by a dehydration reaction.

dipeptide

A polymer of two amino acids linked by a peptide bond.

What is a trans fat? Why should you limit them in your diet?

A trans fat is an unsaturated fat with a trans double bond; the result of the process of hydrogenating vegetable oils to prevent lipids from separating out in liquid (oil) form. Trans fats should be limited in your diet because they have been found to contribute to atherosclerosis, a cardiovascular disease caused by plaque buildup within the walls of blood vessels.

Function

Accelerate chemical reactions

Example

Actin, myosin

Notice that there are five nitrogen bases. Which four are found in DNA?

Adenine, guanine, cytosine, thymine

Which four are found in RNA?

Adenine, guanine, cytosine, uracil

Lipids include fats, waxes, oils, phospholipids, and steroids. What characteristic do all lipids share?

All lipids mix poorly, if at all, with water.

Example

Casein, which is the major source of amino acids for baby mammals; ovalbumin, the protein of egg white

Secondary α helix β pleated sheet

Coils and folds resulting from the hydrogen bonds between the repeating constituents of the polypeptide backbone Alpha helix: Delicate coil held together by hydrogen bonding between every fourth amino acid Beta pleated sheet: Two or more strands of the polypeptide chain lying side by side, connected by hydrogen bonds between parts of the two parallel polypoptide backbone

Polymers are assembled and broken down in two types of reactions: dehydration synthesis and hydrolysis. Which kind of reaction is this?

Dehydration synthesis

Besides mutation, which changes the primary structure of a protein, protein structure can be changed by denaturation. Define denaturation, and give at least three ways a protein may become denatured.

Denaturation is the changing of a protein during which the protein unravels and loses its native shape because the weak chemical bonds and interactions within a protein have been destroyed. Possible examples of ways a protein may become denatured include alteration of pH, salt concentration, temperature, transfer from aqueous environment to nonpolar solvent, chemicals, and excessive heat

How do ribose and deoxyribose sugars differ?

Deoxyribose sugar lacks an oxygen atom on the second carbon in the ring.

What is the difference between an aldehyde sugar and a ketone sugar?

Depending on the location of the carbonyl group, a sugar is either an aldose (aldehyde sugar) or a ketose (ketone sugar). Glucose, for example, is an aldose; fructose, an isomer of glucose, is a ketose. In aldehyde sugars, the carbonyl group is at the end of the carbon skeleton, while in the ketone sugars, the carbonyl group is within the carbon skeleton.

Here is the abbreviated ring structure of glucose. Where are all the carbons?

Each corner represents a carbon; each carbon in this figure is labeled 1 through 6.

List four important functions of fats.

Energy storage, long-term food reserve in mammals, adipose tissue cushions vital organs, body insulation.

Structural

Examples :Cellulose, chitin

Storage

Examples :Starch, glycogen

glycogen

Is a storage polysaccharide produced by vertebrates; stored in your liver

So, as a quick review, all of the sugars in the figure above have the same chemical formula: C6H12O6. What term did you learn in Chapter 3 for compounds that have the same molecular formulas but different structural formulas?

Isomers

Primary

Linked series of amino acids with a unique sequence

maltose

Malt sugar; used to brew beer

Example

Maltase, pepsin, sucrase

Is C6H12O6 (glucose) a monomer, or a polymer?

Monomer

Monomers are connected in what type of reaction? What occurs in this reaction?

Monomers are connected in a dehydration reaction. During a dehydration reaction, two monomer molecules are covalently bonded to each other, with the loss of a water molecule. In this reaction, each monomer contributes part of the water molecule that is released during the reaction. This reaction is repeated as monomers are added to the chain one by one, making a polymer.

fructose

Monosaccharide commonly called "fruit sugar"

Let's look at carbohydrates, which include sugars and starches. First, what are the monomers of all carbohydrates?

Monosaccharides, or simple sugars

Function

Movement

. Let's look at our reaction in question 7 again: C6H12O6 + C6H12O6 C12H22O11 + H2O

Notice that two monomers are joined to make a polymer. Since the monomers are monosaccharides, the polymer is a disaccharide. Three disaccharides have the formula C12H22O11. Name them below and fill out the chart.

If a fat is composed of three fatty acids and one glycerol molecule, how many water molecules will be removed to form it? Again, what is this process called?

One water molecule is removed for each fatty acid joined to the glycerol, equaling three water molecules for every triacylglycerol formed. This process is called dehydration synthesis.

Quaternary

Overall protein structure that results from the aggregation of these polypeptide subunits

Tertiary

Overall shape of the polypeptide resulting from interactions between the side chains (R groups) of the various amino acids

To summarize, what are the three components of a nucleotide?

Phosphate group, sugar, nucleoside

Large molecules (polymers) are converted to monomers in what type of reaction?

Polymers are disassembled to monomers by hydrolysis, a process that is essentially the reverse of the dehydration reaction.

Name two saturated fats.

Possible examples include lard, butter, or most animal fats.

Name two unsaturated fats.

Possible examples include olive oil, cod liver oil or most plant or fish fats.

What are other examples of steroids?

Possible examples include vertebrate sex hormones.

The flow of genetic information is from DNA RNA protein. Use this figure to explain the process. Label the nucleus, DNA, mRNA, ribosome, and amino acids.

See page 86 of your text for the labeled figure The mRNA molecule interacts with the cell's protein-synthesizing machinery to direct production of a polypeptide, which folds into all or part of a protein. The sites of protein synthesis are tiny structures called ribosomes. In a eukaryotic cell, ribosomes are in the cytoplasm, but DNA resides in the nucleus. Messenger RNA conveys genetic instructions for building proteins from nucleus to the cytoplasm

The components of a nucleic acid are a sugar, a nitrogenous base, and a phosphate group. Label each on the figure below.

See page 87 of your text for the labeled figure

You may recall that early in this chapter we looked at the numbering system for the carbons of a sugar. Label the end of the strand on the left side of the figure below that has the number 5 sugar 5' and the other end of the chain 3'. Finally, label one nucleotide.

See page 87 of your text for the labeled figure

Here is a model of DNA, which was proposed by James Watson and Francis Crick. What is this shape called?

See page 89 of your text for the figure. Double helix

Label each of the levels of protein structure on this figure.

See pages 82-83 of your text for the labeled figure. From Left to Right: Primary, Secondary, Tertiary, Quaternary

Function

Storage of amino acids

cellulose

Structural polysaccharide that comprises plant cell walls

chitin

Structural polysaccharide that gives cockroaches their crunch

Why are the "tails" hydrophobic?

The "tails" are hydrophic (avoid water) because they are hydrcarbon. As previously discussed in chapter 4, hydrocarbons are hydrophobic compounds because the great majority of their bonds are relativelynonpolar carbon-to-hydrogen.

What are the building blocks of fats? Label them on this figure.

The building blocks of fats are glycerol and fatty acids. In the figure below, the glycerol molecule is in gray, and the three fatty acids are in yellow.

Which of the two fatty acid chains in the figure with question 31 is unsaturated? Label it. How do you know it is unsaturated?

The fatty acid chain on the right is unsaturated. We know this because of the kink in the chain, indicating a double bond.

Why are many unsaturated fats liquid at room temperature?

The kinks where the cis bonds are located prevent the molecules from packing together closely enough to solidify at room temperature.

Function

Transport

Example

Transthyretin

Example

Transthyretin polypeptide

glucose

Two monomers of this form maltose

Draw a fatty acid chain that is eight carbons long and is unsaturated. Circle the element in your chain that makes it unsaturated, and explain what this means.

Unsaturated fatty acids have one or more double bond, with one fewer hydrogen atom on each doublebonded carbon. Nearly all double bonds in naturally occurring fatty acids are cis bonds, which cause a kink in the hydrocarbon chain whenever they occur.

Here is a molecule of starch, which shows 1-4 glycosidic linkages. Translate and explain this terminology in terms of carbon numbering.

When glucose forms a ring, the hydroxyl group attached to the number 1 carbon is positioned either below or above the plane of the ring. These two ring forms for glucose are called alpha and beta. In starch, all the glucose monomers are in the alpha configuration.

The root words of hydrolysis will be used many times to form other words you will learn this year. What does each root word mean?

hydro- water lysis break