Question 1

Fructose and glucose both have the formula $$\mathrm{C_6H_{12}O_6$}$$, but their structures differ. Which of the following statements is TRUE regarding their relationship?

Accepted Answer

They are structural isomers, meaning they have the same molecular formula but different arrangements of atoms.

Question 2

Which of the following best describes the arrangement of phospholipids in water, as illustrated in image B?

Accepted Answer

Hydrophilic heads face outward toward water, while hydrophobic tails cluster inward away from water.

Question 3

Which of the following molecules can freely diffuse across a pure phospholipid bilayer without the aid of transport proteins?

Accepted Answer

Oxygen ($$\mathrm{O_2$}) $$and steroid molecules

Question 4

Why can humans extract energy from pasta but not from the box it comes in, even though both are composed of glucose monomers?

Accepted Answer

Humans have enzymes to break down starch in pasta but lack enzymes to digest cellulose in the box.

Question 5

Which statement about the formation of a phospholipid bilayer is correct?

Accepted Answer

It forms spontaneously due to phospholipid interactions with water and does not require energy input from the cell.

Question 6

In the diagram of a membrane channel protein, which region is most likely to be hydrophobic?

Accepted Answer

Region C, which is in contact with the phospholipid tails in the membrane's interior.

Question 7

Most transmembrane pumps, channels, and carriers in the cell membrane are composed of which type of macromolecule?

Accepted Answer

Proteins

Question 8

During normal kidney function, sodium ions are transported from an area of low concentration to an area of high concentration. Which of the following must be true about this process?

Accepted Answer

It requires energy input and a transmembrane protein, and is an example of active transport.

Question 9

A Paramecium caudatum living in fresh water is hypertonic to its environment. What is the net direction of water movement, and what is the function of its contractile vacuole?

Accepted Answer

Water moves into the cell, and the contractile vacuole pumps water out to maintain internal solute concentrations.

Question 10

Which molecule is a monosaccharide based on its structure and formula?

Accepted Answer

Molecule A, because it has the general formula $$\mathrm{C_n(H_2O)_n}$$, many hydroxyl groups, and a carbonyl group.

Question 11

Which molecule stores energy in animals in the form of glucose and allows glucose to be made available when needed?

Accepted Answer

Glycogen

Question 12

Which category of biological molecule is NOT built from monomers?

Accepted Answer

Lipids

Question 13

Which of the following is a structural polysaccharide found in plant cell walls?

Accepted Answer

Cellulose

Question 14

Which molecule is the primary energy storage molecule in plants?

Accepted Answer

Starch

Question 15

Which of the following is TRUE about the permeability of a pure phospholipid bilayer?

Accepted Answer

Small, non-polar molecules like $$\mathrm{O_2$}$$ and steroids can cross freely by simple diffusion.

Question 16

Which of the following best explains why water can cross a phospholipid bilayer to some extent, despite being polar?

Accepted Answer

Water is small enough to pass through the bilayer, but its polarity prevents it from crossing completely freely.

Question 17

Which of the following is a correct match between a biological molecule and its monomer?

Accepted Answer

Proteins: amino acids

Question 18

Which molecule is described as a ribonucleotide based on its structure?

Accepted Answer

Molecule B, because it has a 5-carbon sugar attached to phosphate and a nitrogenous base, and the sugar has a 2'-OH group.

Question 19

Which molecule is described as an amino acid based on its structure?

Accepted Answer

Molecule C, because it has a central carbon with an amino group, a carboxyl group, a hydrogen, and an R-group.

Biology Study Guide: Carbohydrates, Membranes, and Molecular Transport

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