Lipids differ from other large biological molecules in that they a. are much larger. b

Lifes molecular diversity is based on the properties of carbon. Carbons ability to bond with four other atoms is the basis for building large and diverse organic compounds. Hydrocarbons are composed of only carbon and hydrogen. Isomers have the same molecular formula but different structures.

A few chemical groups are key to the functioning of biological molecules. Hydrophilic functional groups give organic molecules specific chemical properties.

Cells make a huge number of large molecules from a limited set of small molecules. A monosaccharide has a formula that is a multiple of CH2O and contains hydroxyl groups and a carbonyl group.

Two monosaccharides are linked to form a disaccharide.

What is high-fructose corn syrup, and is it to blame for obesity? HFCS, a mixture of glucose and fructose derived from corn, is commonly added to drinks and processed foods.

Polysaccharides are long chains of sugar units. Starch and glycogen are storage polysaccharides; cellulose is structural, found in plant cell walls. Chitin is a component of insect exoskeletons and fungal cell walls.

Fats are lipids that are mostly energy-storage molecules. Lipids are diverse, hydrophobic compounds composed largely of carbon and hydrogen. Fats (triglycerides) consist of glycerol linked to three fatty acids. Saturated fatty acids are found in animal fats; unsaturated fatty acids are typical of plant oils.

Phospholipids and steroids are important lipids with a variety of functions. Phospholipids are components of cell membranes. Steroids include cholesterol and some hormones.

Anabolic steroids pose health risks.

Proteins are made from amino acids linked by peptide bonds. Protein diversity is based on different sequences of amino acids, monomers that contain an amino group, a carboxyl group, an H, and an R group, all attached to a central carbon. The R groups distinguish 20 amino acids, each with specific properties.

A proteins specific shape determines its function. Proteins are involved in almost all of a cells activities; as enzymes, they regulate chemical reactions.

A proteins shape depends on four levels of structure. A proteins primary structure is the sequence of amino acids in its polypeptide chain. Its secondary structure is the coiling or folding of the chain, stabilized by hydrogen bonds. Tertiary structure is the overall three-dimensional shape of a polypeptide, resulting from interactions among R groups. Proteins made of more than one polypeptide have quaternary structure.

DNA and RNA are the two types of nucleic acids. DNA and RNA serve as the blueprints for proteins and thus control the life of a cell.

Nucleic acids are polymers of nucleotides. Nucleotides are composed of a sugar, a phosphate group, and a nitrogenous base. DNA is a double helix; RNA is a single polynucleotide chain.

Lactose tolerance is a recent event in human evolution. Mutations in DNA have led to lactose tolerance in several human groups whose ancestors raised dairy cattle.

The diversity of life is staggering. Yet the molecular logic of life is simple and elegant: Small molecules common to all organisms are ordered into unique macromolecules. Explain why carbon is central to this diversity of organic molecules. How do carbon skeletons, chemical groups, monomers, and polymers relate to this molecular logic of life?

Complete the table to help review the structures and functions of the four classes of organic molecules.

A glucose molecule is to starch as (Explain your answer.) a. a steroid is to a lipid. b. a protein is to an amino acid. c. a nucleic acid is to a polypeptide. d. a nucleotide is to a nucleic acid. e. an amino acid is to a nucleic acid.

What makes a fatty acid an acid? a. It does not dissolve in water. b. It is capable of bonding with other molecules to form a fat. c. It has a carboxyl group that donates an H+ to a solution. d. It contains only two oxygen atoms. e. It is a polymer made of many smaller subunits.

Where in the tertiary structure of a water-soluble protein would you most likely find an amino acid with a hydrophobic R group? a. at both ends of the polypeptide chain b. on the outside, next to the water c. covalently bonded to another R group d. on the inside, away from water e. hydrogen-bonded to nearby amino acids

Cows can derive nutrients from cellulose because a. they produce enzymes that recognize the shape of the glucose-glucose bonds and hydrolyze them. b. they rechew their cud to break down cellulose fibers. c. one of their stomachs contains prokaryotes that can hydrolyze the bonds of cellulose. d. their intestinal tract contains termites, which produce enzymes to hydrolyze cellulose. e. they convert cellulose to starch and can digest starch.

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture a. DNA. b. proteins. c. cellulose. d. fatty acids. e. sucrose.

Lipids differ from other large biological molecules in that they a. are much larger. b. are not polymers. c. do not have specific shapes. d. are nonpolar and therefore hydrophilic. e. contain nitrogen atoms.

Of the following functional groups, which is/are polar, tending to make organic compounds hydrophilic? a. carbonyl b. amino c. hydroxyl d. carboxyl e. all of the above 1

Unsaturated fats a. are more common in animals than in plants. b. have fewer fatty acid molecules per fat molecule. c. are associated with greater health risks than are saturated fats. d. have double bonds in their fatty acid chains. e. are usually solid at room temperature. 1

List three different kinds of lipids and describe their functions. 1

Explain why heat, pH changes, and other environmental changes can interfere with a proteins function. 1

How can a cell make many different kinds of protein out of only 20 amino acids? Of the myriad possibilities, how does the cell know which proteins to make? 1

Briefly describe the various functions performed by proteins in a cell. 1

Explain how DNA controls the functions of a cell. 1

Sucrose is broken down in your intestine to the monosaccharides glucose and fructose, which are then absorbed into your blood. What is the name of this type of reaction? Using this diagram of sucrose, show how this would occur. 1

Circle and name the functional groups in this organic molecule. What type of compound is this? For which class of macromolecules is it a monomer? 1

Enzymes usually function best at an optimal pH and temperature. The following graph shows the effectiveness of two enzymes at various temperatures. a. At which temperature does enzyme A perform best? Enzyme B? b. One of these enzymes is found in humans and the other in thermophilic (heat-loving) bacteria. Which enzyme would you predict comes from which organism? c. From what you know about enzyme structure, explain why the rate of the reaction catalyzed by enzyme A slows down at temperatures above 40C (140F). 1

Some scientists hypothesize that life elsewhere in the universe might be based on the element silicon rather than on carbon. Look at the electron shell diagrams in Figure 2.

What properties does silicon share with carbon that would make siliconbased life more likely than, for example, neon-based or sulfur-based life?