High School Biology : Understanding Lipids and Carbohydrates

Study concepts, example questions & explanations for High School Biology

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Example Questions

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Example Question #1 : Introductory Topics

What is the reason for lipids requiring carrier proteins in order to be transported in the blood?

Possible Answers:

Their stability

Their shape

Their size

Their polarity

Correct answer:

Their polarity

Explanation:

Unlike carbohydrates and proteins, lipids are mainly nonpolar molecules. As a result, they are unable to be dissolved in aqueous solutions, such as blood. This makes them require a lipoprotein in order to be transported through the bloodstream. Without these proteins, lipids would be insoluble in the blood and cause clots.

Example Question #2 : Understanding Lipids And Carbohydrates

Phospholipids are amphipathic molecules. This means that they __________.

Possible Answers:

act as both a reactant and a product

dissolve in aqueous solutions

can be digested or created in the body

have both polar and nonpolar sections

Correct answer:

have both polar and nonpolar sections

Explanation:

Amphipathic molecules have both polar and nonpolar sections. For phospholipids, the phosphate region carries a negative charge, making it polar, while the lipid tail is a nonpolar hydrocarbon. Being amphipathic is a key characteristic that allows phospholipids to form the plasma membrane. The polar ends are able to face the aqueous environment while the nonpolar ends are faced towards each other. This creates an effective nonpolar barrier around the cell, while still remaining stable by having polar regions facing the aqueous environments.

Example Question #3 : Macromolecules

Which carbohydrate cannot be digested by humans?

Possible Answers:

Glycogen

Cellulose

Starch

Amylose

Correct answer:

Cellulose

Explanation:

Cellulose is a polysaccharide in which the monomers are linked by a beta linkage. This linkage requires a specialized enzyme that is not found in human beings. As a result, humans cannot break down cellulose.

Glycogen is used to store glucose in the body, and can be broken down to release energy. Starch is used to store glucose in plants, but can also be broken down by humans. Amylose is a component of starch.

Example Question #2 : High School Biology

Which of the following classes of molecules produces the most energy per gram?

Possible Answers:

Fibers

Carbohydrates

Proteins

Fats

Nucleic acids

Correct answer:

Fats

Explanation:

There are four classes of biological molecules: fats, carbohydrates, proteins, and nucleic acids. Of these, fats produce the most energy per gram at a whopping nine calories per gram. Carbohydrates and proteins produce less than half of this, at only four calories per gram.

Example Question #3 : High School Biology

Which of the following is not a type of fat in the body?

Possible Answers:

Unsaturated fats

Trans fats

Di-saturated fats

Saturated fats

Mono-unsaturated fats

Correct answer:

Di-saturated fats

Explanation:

Lipids, or fats, are formed from hydrocarbon chains. The carbon atoms link together and bond to hydrogen to fill their orbitals. When all the bonds in the molecule are single bonds, the lipid is saturated. There is no such thing as a "di-saturated fat."

When there is a single double bond in the chain, the lipid is mono-unsaturated. When there are multiple double bonds in the chain, the lipid is unsaturated. Trans fats have a double bond with the adjacent hydrogen atoms on opposite sides of the carbon chain, maintaining a linear structure.

Most fats in the body are triglycerides. Their primary function is long-term energy storage.

Example Question #1 : Understanding Lipids And Carbohydrates

Which of the following is a carbohydrate?

Possible Answers:

Ribose

Helicase

Triglyceride

Insulin

Cholesterol

Correct answer:

Ribose

Explanation:

Carbohydrates are known as sugars or saccharides. Virtually all carbohydrates end in the suffix "-ose," making them easy to identify. Ribose is a five-carbon sugar found in RNA. Some other common carbohydrates include deoxyribose, glucose, cellulose, and lactose. Sucrose is the technical name of table sugar, which is also a carbohydrate.

The other classes of molecules are fats, proteins, and nucleic acids. Fats, or lipids, can be further broken down into other categories, such as sterols and glycerolipids. Sterol lipids generally have the suffix "-ol" and include cholesterol and estradiol (estrogen). Glycerolipids include triglycerides. Proteins are formed from amino acids. Enzymes are a class of protein and generally have the suffix "-ase," such as helicase. Other proteins often have the suffix "-in" or "-en," such as insulin.

Example Question #7 : Macromolecules

Which of the following are true regarding lipids?

Possible Answers:

Lipids are hydrophilic

Lipids can only be triglycerides

Lipids are soluble in water

Lipids are soluble in nonpolar solvents

Lipids do not store energy

Correct answer:

Lipids are soluble in nonpolar solvents

Explanation:

Lipids are hydrophobic, which means that they are insoluble in water, a polar solvent. Lipids can store abundant energy. Lipids contain large nonpolar regions, which means that they are soluble in nonpolar solvents. Triglycerides are only one type of lipids. Other types include, but are not limited to: monoglycerides, diglycerides, phospholipids, and fatty acids.

Example Question #6 : Understanding Lipids And Carbohydrates

What is the difference between saturated and unsaturated fatty acids?

I. Saturated fatty acids do not contain double bonds, unsaturated fatty acids contain at least one double bond

II. Saturated fatty acids contain at least one double bond, unsaturated fatty acids do not contain double bonds

III. Saturated fatty acids contain the maximum amount of H atoms on their carbon skeletons

IV. Unsaturated fatty acids contain the maximum amount of H atoms on their carbon skeletons

Possible Answers:

I and III

II only

I only

II and IV

III only

Correct answer:

I and III

Explanation:

Saturated fatty acids do not have double bonds between carbon atoms.  Therefore, the maximum amount of hydrogen atoms are bonded to the carbon skeleton chain.  Saturated fatty acids are solid at room temperature, like butter.  Unsaturated fatty acids have at lease one double bond.  These double bonds create kinks in the carbon skeleton, preventing hydrogen atoms from packing onto the skeleton.  Unsaturated fatty acids are therefore more fluid and are liquid at room temperature, like oil and natural peanut butter. 

Example Question #6 : Understanding Lipids And Carbohydrates

What is true of both lipids and fats?

I. Both are macromolecules

II. Both are hydrophobic

III. Fats are composed of glycerol and fatty acids

IV. Lipids are composed of glycerol and fatty acids

V. Fats are held together via ester linkage

Possible Answers:

I, II, IV, and V

II, III, and V

I, II, and V

I, III, and IV

I and II

Correct answer:

II, III, and V

Explanation:

Because lipids do not include true polymers, they are not big enough to be considered macromolecules.  However, like fats, lipids are hydrophobic.  Fats are considered macromolecules and are composed of glycerol and fatty acid molecules.  The glycerol and fatty acid molecules are joined via an ester linkage, which is formed by a dehydration reaction.  

Example Question #5 : High School Biology

What sugar molecule does ATP contain?

Possible Answers:

Adenine

Adenosine

Triphosphate

Deoxyribose

Ribose

Correct answer:

Ribose

Explanation:

ATP stands for adenosine triphosphate. Ribose is the five-carbon sugar, which is bonded to a phosphate group and adenine group in a molecule of ATP. 

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