Because glycogen is so heavily branched, it is able to pack more glucose units together in a small space, thus it is more compact and has a greater solubility. Moreover, the branching allows for glycogen enzymes to act more efficiently on the chains of glucose, and so both degradation and synthesis have increased rates.

lactose is made up of galactose and glucose and is bound via a beta 1,4 glycosidic bond. 

the enzyme lactase cleaves this bond to break down the sugar lactose. Maltose is glucose- alpha 1,4- glucose, and sucrose is glucose- alpha, 1,2- fructose. 

Aldotrioses are monosaccharides that contain both an aldehyde (an aldose) and three carbons (a triose). Knowing the definition of the word, and the breakdown of parts of the word, can help you recognize the molecule. The simplest aldotriose is glyceraldehyde.

A related concept involves ketotrioses, which are monosaccharides that contain both a ketone (a ketose) and three carbonds (a triose). Dihydroxyacetone is an example of a ketotriose.

Enantiomers are chiral molecules that are non-superimposable mirror images of each other. Diastereomers result when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent stereocenters and are not mirror images of each other. An epimer is one of two stereoisomers that differ in configuration at only one stereocenter. An anomer is a type of epimer; it is one of two stereoisomers of a cyclic sugar that differs only in its configuration at the hemiacetal or acetal carbon (the anomeric carbon).

When it comes to metabolizing sugars, only reducing sugars are able to undergo breakdown. This is because reducing sugars are able to be converted from their closed chain form into their open chain form. It is only in the open chain form that sugars such as glucose can be metabolized.

Only reducing sugars can be converted into their open chain form. The reason for this is that the anomeric carbon for these sugars is not occupied. In their ring form, such sugars exist as hemiacetals that can readily and reversibly undergo chain opening. Additionally, some hemiketals can be converted into their open chain form, but they need to be able to tautomerize into their aldose form first.

Non-reducing sugars have their anomeric carbon tied up in a bond, and thus are locked in an acetal or ketal form. Consequently, they cannot convert into their open chain form, meaning that they cannot be metabolized.

Glucose has five (not six) hydroxyl groups. Reducing sugars either have an aldehyde group or can form one through isomerism; sucrose doesn’t fit either description. Although there are more amylose molecules than amylopectin in starch, amylose is a minor component by mass; amylopectin makes up 70-80% of starch by mass. Polysaccharides are indeed joined in the union of two oses, which form glycosidic bonds.

Carbohydrate chains contain aldehyde or ketone functional groups, which are types of carboxyl groups. Remember the general formula for a carbohydrate is:  since they are hydrates (water) of carbon.

To identify the answer choice that is NOT a polysaccharide, let's go delve into each answer choice a bit.

Cellulose is a polysaccharide and also a very important component of the cell wall of plants. It consists of many glucose sugars bound together via beta (1-4) linkages.

Peptidoglycan is also a polysaccharide and a very important component of the cell wall of bacteria. Its structure consists of alternating N-acetylglucosamine and N-acetylmuramic acid connected via beta (1-4) linkages. Both of these are modified sugar molecules.

Chitin is a polysaccharide that plays an important role in the structure of the exoskeleton of many fungi, arthropods, and insects. Its structure consists of a long chain of N-acetylglucosamine, which is a derivative of the sugar glucose.

Collagen is the only answer choice that does not represent a carbohydrate. Rather, collagen is a protein that plays a very important role in the extracellular matrix of various connective tissues found in animals.

Glycogen is a branched form of glucose that is the storage form in animals. It contains beta (1-4) and beta (1-6) linkages.

Cyclized monosaccharides can exist in two different stereoisomers that depend on the orientation of the hydroxyl group on the anomeric carbon. If this  group is on the opposite side of the ring as the  group, the sugar as the alpha anomer. The opposite orientation is referred to at the beta anomer. Cellulose is a polymer of beta glucose while starch is a polymer of alpha glucose, and the bonds between these glucose monomers differ depending on their anomer. This makes it so an enzyme can recognize one or the other but not both. Note that D-sugars are biologically relevant. 

A glycosaminoglycan (GAG) is a long, unbranched polysaccharide that consists of many repeating disaccharide units. Dermatan sulfate, keratan sulfate, hyaluronate, and heparin are all examples of glycosaminoglycans. Erythropoietin, however, is a glycoprotein hormone that stimulates production of red blood cells.