Q: Cellulose and starch are both polymers of glucose. Which structural difference accounts for their different functions in plants?

Cellulose has $eta$-1,4-glycosidic linkages, while starch has $oldsymbol{ ext{both}}$ $oldsymbol{ ext{1,4}}$ and $oldsymbol{ ext{1,6}}$ $oldsymbol{ ext{glycosidic}}$ $oldsymbol{ ext{linkages}}$ in amylopectin.

Question 1

Which of the following best describes the difference between a monomer and a polymer in biological macromolecules?

Accepted Answer

A monomer is a repeating unit that serves as a building block, while a polymer is a long molecule consisting of many monomers linked together.

Question 2

Which chemical reaction is responsible for linking monomers together to form polymers, and what is a byproduct of this reaction?

Accepted Answer

Dehydration synthesis; water is produced as a byproduct.

Question 3

Which of the following statements about monosaccharides is correct?

Accepted Answer

Monosaccharides have an aldehyde (or carbonyl $C=O$) group and multiple hydroxyl groups.

Question 4

Which type of bond links two monosaccharides together to form a disaccharide?

Accepted Answer

Glycosidic linkage

Question 5

Cellulose and starch are both polymers of glucose. Which structural difference accounts for their different functions in plants?

Accepted Answer

Cellulose has $eta$-1,4-glycosidic linkages, while starch has $oldsymbol{	ext{both}}$ $oldsymbol{	ext{1,4}}$ and $oldsymbol{	ext{1,6}}$ $oldsymbol{	ext{glycosidic}}$ $oldsymbol{	ext{linkages}}$ in amylopectin.

Question 6

Which of the following is NOT a function of carbohydrates in living organisms?

Accepted Answer

Catalyzing chemical reactions

Question 7

Lipids are grouped together because they share which property?

Accepted Answer

They are all hydrophobic or amphipathic.

Question 8

Phospholipids are essential components of cell membranes. Which feature of their structure allows them to form bilayers in aqueous environments?

Accepted Answer

They are amphipathic, with a hydrophilic head and hydrophobic tails.

Question 9

Which of the following is a correct pairing of a macromolecule class with its monomer?

Accepted Answer

Carbohydrate – Monosaccharide

Question 10

A scientist is studying a molecule with the following structure: a nitrogenous base, a five-carbon sugar, and one or more phosphate groups. This molecule is most likely a:

Accepted Answer

Nucleotide

Question 11

Which type of bond connects nucleotides together in a single strand of DNA?

Accepted Answer

Phosphodiester bond

Question 12

Which of the following best explains why DNA is double-stranded while RNA is usually single-stranded?

Accepted Answer

DNA has complementary base pairing between strands, stabilized by hydrogen bonds.

Question 13

Which of the following is a function of nucleic acids in cells?

Accepted Answer

Storing, transmitting, and expressing genetic information

Question 14

Which of the following best describes the difference between DNA and RNA?

Accepted Answer

DNA is usually double-stranded and contains deoxyribose; RNA is usually single-stranded and contains ribose.

Question 15

A mutation causes a cell to produce a phospholipid with two hydrophilic tails. What is the most likely effect on the cell membrane?

Accepted Answer

The phospholipids would not form a bilayer, disrupting membrane structure.

Question 16

Which of the following is a correct match between a polysaccharide and its biological function?

Accepted Answer

Starch – stores glucose in plants

Question 17

Which of the following best explains why lipids are not considered true polymers?

Accepted Answer

Lipids are not made of repeating monomer units linked by covalent bonds.

Question 18

A dehydration reaction between two glucose molecules forms which disaccharide?

Accepted Answer

Maltose

Question 19

Which of the following best describes the amphipathic nature of phospholipids?

Accepted Answer

They have both a hydrophilic head and hydrophobic tails.

Question 20

Which of the following is a correct description of the role of mRNA in the cell?

Accepted Answer

mRNA carries genetic instructions from DNA to the ribosome for protein synthesis.

Biological Macromolecules I: Structure, Chemistry, and Function

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