Week 3 Quiz

A cell joins two amino acids into a short chain. Which reaction does it use, and what happens to water?

Select one.

• Hydrolysis, which removes one water molecule for each new bond
• Hydrolysis, which adds one water molecule for each new bond
• Dehydration synthesis, which removes one water per new bond
• Dehydration synthesis, which adds one water molecule for each new bond

Starch is built from glucose by dehydration synthesis. How many water molecules are removed when 3 glucose units are joined in a row?

Select one.

• 3 water molecules, one for each glucose unit
• 2 water molecules, one for each new bond
• 1 water molecule for the whole chain
• 4 water molecules, one per unit plus one to start

Which class of macromolecules is NOT made as a chain of one repeating monomer?

Select one.

• Carbohydrates
• Proteins
• Nucleic acids
• Lipids

Starch and cellulose are both polysaccharides. What explains why one is stored fuel and the other is structural fiber?

Select one.

• Both are built from glucose, linked differently
• Starch is built from glucose; cellulose from amino acids
• Cellulose is a lipid that only looks like a carbohydrate
• Starch is a disaccharide; cellulose is a polysaccharide

Which list puts the four levels of protein structure in order, starting from the first level?

Select one.

• Secondary, primary, tertiary, quaternary
• Primary, tertiary, secondary, and then quaternary
• Primary, secondary, tertiary, quaternary
• Quaternary, tertiary, secondary, and then primary

True or false: when heat denatures a protein, the amino-acid chain is cut into pieces, so the protein's primary structure is lost.

True or false.

• True
• False

In sickle cell disease, one amino acid at position 6 of hemoglobin's beta chain is replaced by another. Which swap is it?

Select one.

• Glutamic acid takes the place of valine
• Valine takes the place of glutamic acid
• Uracil takes the place of thymine
• The amino acid is lost and the chain is cut short

Which features describe RNA? Select all that apply.

Select every option that applies.

• It has the sugar ribose.
• It uses thymine as one of its bases.
• It uses uracil where DNA uses thymine.
• It is usually a single strand.
• It is usually built as a two-stranded double helix.

In the iodine starch test (illustrative results), five foods are each tested with a drop of iodine. Which sample is the negative control?

Select one.

• Bread, because it turns blue-black
• Sugar water, because it tastes sweet
• Fruit, because it changes only faintly
• Plain water, because it has no starch

In the iodine starch test (illustrative results), sugar water stays amber. What does that result show?

Select one.

• No starch: sucrose is a disaccharide with no coil
• No carbohydrate of any kind is present in the sugar water
• The iodine was used up before it could react with anything
• Sugar water is a lipid, like the cooking oil