Biomolecules Quiz
Questions: 16 · 10 minutes
1. An enzyme permanently loses activity after being heated well above its optimum temperature. What is the most likely explanation?
Its three-dimensional structure changed, altering the active site
Its peptide bonds were converted into glycosidic bonds
It used up all of its catalytic energy during heating
Its amino acids were changed into nucleotides
2. One DNA strand has the sequence 5'-ACGT-3'. Which sequence shows its complementary, antiparallel strand?
3'-ACGT-5'
3'-TGCA-5'
5'-TGCA-3'
3'-UGCA-5'
3. Why do triglycerides generally store more energy per gram than carbohydrates?
They contain many energy-rich carbon-hydrogen bonds
They are built from repeating nucleotide units
They catalyze their own breakdown without enzymes
They contain more water within their molecular structure
4. Which class of biomolecule forms the basic bilayer of cell membranes?
Polysaccharides
Phospholipids
Nucleic acids
Globular proteins
5. Which statement correctly distinguishes the bases normally found in DNA and RNA?
DNA contains uracil, while RNA contains thymine
DNA contains adenine, while RNA does not
RNA contains cytosine, while DNA does not
DNA normally contains thymine, while RNA normally contains uracil
6. Which smaller units are joined together to form proteins?
Nucleotides
Monosaccharides
Fatty acids
Amino acids
7. A person's diet lacks one essential amino acid. What is the most direct consequence for protein production?
Nucleotides will replace the missing amino acid in polypeptide chains
All amino acids will automatically be converted into that missing amino acid
Synthesis of proteins requiring that amino acid may be limited
Protein synthesis will continue unchanged because amino acid sequence does not matter
8. Lactase catalyzes the hydrolysis of lactose. Which products should result?
Glucose and galactose
Glycerol and three fatty acids
Glucose and fructose
Two glucose molecules
9. Why can a greater proportion of unsaturated phospholipid tails help a membrane remain fluid at lower temperatures?
Their double bonds create kinks that reduce tight packing
They form additional peptide bonds between neighboring lipids
They attach directly to DNA and increase molecular movement
Their phosphate groups are converted into fatty acids
10. Which description best defines the tertiary structure of a protein?
The exact sequence of amino acids in a polypeptide
Local alpha helices and beta sheets formed mainly by backbone hydrogen bonds
The association of two or more separate polypeptide subunits
The overall three-dimensional shape of one polypeptide produced by interactions among its side chains
11. A student adds iodine solution to a food sample and observes a blue-black color. Which substance is present?
Protein
Reducing sugar
Starch
Lipid
12. When two monosaccharides join to form a disaccharide by a condensation reaction, what else is produced?
Carbon dioxide
Ammonia
Oxygen
Water
13. An enzyme works best at pH 7 but becomes much less active at pH 3. What is the most direct molecular explanation?
The substrate has been transformed into a phospholipid
The enzyme has released all of its stored chemical energy
Changes in ionization can alter interactions that maintain the active site's shape and charge
The enzyme's amino acids have been replaced by sugars
14. Which carbohydrate is the main storage polysaccharide in animals?
Cellulose
Starch
Glycogen
Chitin
15. A phosphate group, a five-carbon sugar, and a nitrogenous base together form which unit?
An amino acid
A nucleotide
A monosaccharide
A triglyceride
16. A heated Benedict's test produces a strong orange-to-brick-red precipitate. What does this indicate?
The sample contains abundant starch
The sample contains reducing sugar
The sample contains peptide bonds
The sample contains DNA