Question 1

Which of the following best explains why cellulose provides structural support in plant cell walls, while starch serves primarily as an energy storage molecule in plants?

Accepted Answer

Cellulose has straight, unbranched chains that allow hydrogen bonding between molecules, creating rigid structures, while starch has branched or helical chains that are more easily broken down for energy.

Question 2

A scientist is analyzing a molecule that consists of a long chain of carbon and hydrogen atoms with very few oxygen atoms. The molecule does not dissolve in water. Which class of biological macromolecule does this molecule most likely belong to?

Accepted Answer

Lipids

Question 3

Which of the following statements about the structure of phospholipids is correct?

Accepted Answer

Phospholipids have two fatty acid chains and a phosphate group, with the head being polar and hydrophilic.

Question 4

Which process is responsible for joining monosaccharides together to form polysaccharides such as starch and cellulose?

Accepted Answer

Dehydration reaction

Question 5

A triglyceride is formed by combining which of the following components?

Accepted Answer

One glycerol molecule and three fatty acids

Question 6

Why are unsaturated fats typically liquid at room temperature, while saturated fats are solid?

Accepted Answer

Unsaturated fats have one or more double bonds causing kinks, preventing tight packing of molecules.

Question 7

Which of the following best describes the hydrophobic nature of lipids?

Accepted Answer

Lipids are made up of carbon and hydrogen atoms, forming nonpolar covalent bonds that do not interact with water.

Question 8

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

Accepted Answer

Catalyzing chemical reactions

Question 9

A patient is found to have a deficiency in steroid hormones. Which type of lipid is most directly involved in the synthesis of these hormones?

Accepted Answer

Steroids

Question 10

Which of the following statements about the phospholipid bilayer in cell membranes is correct?

Accepted Answer

The hydrophilic heads face outward toward water, while the hydrophobic tails face inward, away from water.

Question 11

Which of the following best explains why starch and glycogen are both effective energy storage molecules, but glycogen is more suitable for animals?

Accepted Answer

Glycogen is more highly branched than starch, allowing for faster release of glucose when energy is needed.

Question 12

Which of the following equations correctly represents the dehydration reaction that forms a disaccharide from two monosaccharides?

Accepted Answer

$$C_6H_{12}O_6$ + C_6H_{12}O_6$ \rightarrow C$$_{12}$$H_{22}O$$_{11} + H_2O$

Question 13

A researcher finds a molecule with the following structure: a fused ring system of carbon atoms, no fatty acid chains, and it functions as a hormone. Which type of lipid is this molecule?

Accepted Answer

Steroid

Question 14

Which of the following statements about the relationship between structure and function in biological macromolecules is most accurate?

Accepted Answer

The three-dimensional structure of a macromolecule is critical for its specific function in the cell.

Question 15

Which of the following best describes why phospholipids are able to form bilayers in water?

Accepted Answer

Their hydrophilic heads interact with water, while their hydrophobic tails avoid water, causing the tails to face inward and the heads to face outward.

Question 16

Which of the following is a key difference between saturated and unsaturated fatty acids?

Accepted Answer

Unsaturated fatty acids have one or more double bonds, causing kinks in the chain, while saturated fatty acids have no double bonds and are straight.

Question 17

Which of the following is a function of steroids in the human body?

Accepted Answer

Acting as chemical messengers between different units in the body

Question 18

A food scientist is testing a sample and finds it contains molecules that are hydrophobic, contain long hydrocarbon chains, and are solid at room temperature. Which type of fat is most likely present in the sample?

Accepted Answer

Saturated fat

Question 19

Which of the following best explains why lipids do not mix with water?

Accepted Answer

Lipids are made up of nonpolar carbon-hydrogen bonds, which do not interact with polar water molecules.

Carbohydrates and Lipids: Structure, Function, and Biological Importance

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