Maltose is a disaccharide formed from two glucose molecules. Mammals use the enzyme maltase to digest maltose. Lactose is a disaccharide formed from one glucose and one galactose molecule. Mammals use the enzyme lactase to digest lactose. Sucrose is a disaccharide formed from one glucose and one fructose molecule. Mammals use the enzyme sucrase to digest sucrose. Mammals cannot digest cellulose because they do not have the necessary enzymes to do so in their digestive tracts.

Glycogen is a multi-branched glucose polysaccharide that functions in energy storage in animals. Its chemical formula is . In contrast, starch is a glucose polymer which functions in energy storage in plants. Glycogen is also not an artificial sweetener (synthetic sugar substitute). As stated, it is the main storage form of glucose in animals.

Beta-linked polysaccharides are tougher to break down than alpha-linked polysaccharides. This feature makes beta-linked polysaccharides a key component in the cell walls of many bacteria such as peptidoglycan. For even more added structure, beta-linked polysaccharides can also pack into tight crystalline conformations (i.e., cellulose in celery stalks). Thus, all of the answer choices are correct. 

The sugar we eat, or table sugar, is known as sucrose. It is a disaccharide made of one molecule each of glucose and fructose.

Fructose is "fruit sugar." It is a monosaccharide found in honey, fruits, and flowers. Glucose is "blood sugar." It is a monosaccharide that is (like the name suggests) found in our blood. Maltose is "malt sugar." It is a disaccharide formed from two molecules of glucose. It is found in seeds such as barley and is also produced when glucose is caramelized.

"Oligo-" is a prefix which means "few." "Poly-" is a prefix which means "many." Just as the names suggest, combining a few monosaccharides leads to the formation of oligosaccharides. In the same way, combining many monosaccharides leads to the formation of polysaccharides. 

Lactase deficiency is common in humans, particularly those of European descent. Without this enzyme, products containing the sugar lactose cannot be broken down. When lactose cannot be digested, it serves as an osmotic agent in the intestines resulting in abdominal distention and subsequent diarrhea.

Reduction of carbonyl groups in aldoses and ketoses gives sugar alcohols.

Glycogen is an example of a polysaccharide. It is composed of > 10 individual units of a base sugar. On the other hand, disaccharides are composed of only two base sugars. Lactose, sucrose, and maltose are important disaccharides.

Most lipids are made up of a 3-carbon backbone called glycerol. The differences between lipids result from the types of chains attached to the carbons of the glycerol molecule.

The question states that the 3-carbon backbone has two hydrocarbon chains attached. Recall that fatty acids are long, hydrocarbon chains (made up of only carbon and hydrogen atoms); therefore, the molecule in this question has a glycerol molecule with two fatty acids attached. Phospholipids are composed of a glycerol backbone with two fatty acids and one phosphate group. This means the identity of this molecule could be a phospholipid.

Triglycerides are lipids that contain a glycerol molecule with three fatty acids. Sphingolipids are special lipids found in cell membranes that contain a different type of backbone called sphingosine. 

Essential fatty acids are fatty acids that cannot be synthesized by humans; therefore, these fatty acids need to be ingested through food. Essential fatty acids are typically polyunsaturated fatty acids, such as alpha-linoleic acid. Alpha-linoleic acid is a 18-carbon unsaturated fatty acid that has a double bond on the 15^th carbon atom. This cannot be synthesized in the body because humans don’t have enzymes that add double bonds past the ninth carbon atom.

Oleic acid is also an 18-carbon fatty acid; however, humans can synthesize it because it is saturated and does not have any double bonds. Vitamin A is a lipid-soluble vitamin; however, it is not a fatty acid. Recall that all vitamins are molecules that also cannot be synthesized by humans and, therefore, must be ingested via the diet.