Fundamentals of Biological Molecules and Processes Quiz

1. How can glyceraldehyde be converted to an important component of two major classes of lipid? Name these two types of lipid and indicate which of these two is primarily for storage.

Glyceraldehyde is oxidized to acetyl-CoA, which is crucial for the synthesis of sphingolipids and cholesterol.

Glyceraldehyde is transformed into fatty acids, which are important components of triglycerides and sphingolipids.

Glyceraldehyde is reduced to glycerol (see below), which is an important part of tri(acyl)glycerides (primarily for storage) and phospholipids.

Glyceraldehyde is converted to cholesterol, which is an important part of triglycerides and phospholipids.

Glyceraldehyde is reduced to glycerol, which serves as a backbone for triglycerides that are primarily for storage and phospholipids. The incorrect answers provided incorrect information about the conversion of glyceraldehyde and the types of lipids it contributes to.

Explanation

Glyceraldehyde is reduced to glycerol, which serves as a backbone for triglycerides that are primarily for storage and phospholipids. The incorrect answers provided incorrect information about the conversion of glyceraldehyde and the types of lipids it contributes to.

2. You probably know that P is present in DNA, RNA and nucleotides. What is the other type major biomolecule that also contains P? Where in this type of macromolecule do you expect to find P?

Carbohydrates; In the sugar molecules.

Proteins; In the side chain of amino acids.

Fats; In the glycerol backbone.

Phosphorus is indeed present in phospholipids, where it is linked to the third carbon via an ester linkage, not in proteins, carbohydrates, or fats as mentioned in the incorrect answers.

Explanation

Phosphorus is indeed present in phospholipids, where it is linked to the third carbon via an ester linkage, not in proteins, carbohydrates, or fats as mentioned in the incorrect answers.

3. Mammals lack cellulase, an enzyme that degrades the ?-1,4 linkages between glucose molecules in cellulose. However, many mammals (for example, cows and other ruminates) rely on plants materials as foods and derive energy from cellulose. How is this possible?

These mammals have a unique enzyme, different from cellulase, which breaks down cellulose efficiently.

Mammals have a special adaptation in their stomachs that allows them to directly convert cellulose to glucose.

Mammals rely on a process known as regurgitation and re-chewing to break down cellulose effectively.

These mammals rely on a symbiotic relationship with specific bacteria in their GI tracts to break down cellulose, as they themselves lack the enzyme cellulase.

Explanation

These mammals rely on a symbiotic relationship with specific bacteria in their GI tracts to break down cellulose, as they themselves lack the enzyme cellulase.

4. Oil bodies are major storage organelles for lipids. Oil bodies are surrounded by a unique and exceptional membrane with only one phospholipid layer instead of the phospholipid bilayer in a typical membrane. Describe how this could happen.

Oil bodies have a unique osmotic pressure that prevents the formation of a phospholipid bilayer membrane.

The membrane surrounding oil bodies lacks proper formation due to a genetic mutation, resulting in a single phospholipid layer.

The presence of specific proteins in the oil body membrane replaces the need for a second phospholipid layer.

Oil bodies store tri(acyl)glycerides inside, creating a hydrophobic interior that is best suited for interaction with a monolayer of phospholipids. This unique membrane structure eliminates the need for a second phospholipid layer for oil bodies.

Explanation

Oil bodies store tri(acyl)glycerides inside, creating a hydrophobic interior that is best suited for interaction with a monolayer of phospholipids. This unique membrane structure eliminates the need for a second phospholipid layer for oil bodies.

5. What is the approximate molecular weight of a protein that contains 550 amino acids?

550 X 90 Dalton (0.09 kD) = 49.5 kD

550 X 120 Dalton (0.12 kD) = 66.0 kD

550 X 100 Dalton (0.10 kD) = 55.0 kD

The correct approach is to multiply the number of amino acids by an average molecular weight value per amino acid (110 Dalton) to get the approximate molecular weight of the protein.

Explanation

The correct approach is to multiply the number of amino acids by an average molecular weight value per amino acid (110 Dalton) to get the approximate molecular weight of the protein.

6. What is the key to improve ethanol production from corn stover?

The key is to focus on increasing the amount of corn stover used in the fermentation process.

The key is to add more water to the corn stover to enhance the fermentation process.

The key is to use traditional ethanol production methods to convert corn stover into ethanol.

The correct answer emphasizes the importance of discovering cellulose hydrolyzing enzymes in animals which can be utilized to improve the hydrolysis of cellulose in corn stover for ethanol production.

Explanation

The correct answer emphasizes the importance of discovering cellulose hydrolyzing enzymes in animals which can be utilized to improve the hydrolysis of cellulose in corn stover for ethanol production.

7. Draw the structure of galactose. The milk sugar, lactose, is a disaccharide made of ?-D-galactosyl-(1->4)-?-glucose. Draw the structure of lactose.

See below

Option C: Incorrect Disaccharide Linkage Structure of Lactose

Option A: Incorrect Structure of Galactose

Option B: Incorrect Structure of Lactose

The question asked for the correct structures of galactose and lactose, specifically focusing on the difference in configuration at the hydroxyl group on #4 C between these two sugars. The correct structures should reflect this distinction as well as the correct disaccharide linkage present in lactose.

Explanation

The question asked for the correct structures of galactose and lactose, specifically focusing on the difference in configuration at the hydroxyl group on #4 C between these two sugars. The correct structures should reflect this distinction as well as the correct disaccharide linkage present in lactose.