Nutritional Biochemistry

Optical activity refers to the ability of a substance to rotate the plane of plane-polarized light. D and L isomers are used to denote the direction of rotation, with D being dextrorotatory (rotates right) and L being levorotatory (rotates left).

The sweetness of sugars is determined by the orientation of the OH groups in the sugar molecules, which interacts with taste receptors on the tongue to signal sweetness. Factors like color, shape, and temperature do not directly impact the sweetness of sugars.

Aspartame is commonly used as a tabletop sweetener and in diet sodas. It's prepared from aspartic acid, phenylalanine, and methanol. Aspartame is 180 times sweeter than sucrose, but it is unstable at high temperatures. Additionally, it has a caloric value of 4 kcal/g.

Bulking agents are primarily used to adjust the volume of ingredients when using artificial sweeteners, not for enhancing color, increasing protein content, or extending shelf life.

Sugar alcohols are commonly used as bulking agents in various food products due to their low-calorie content and ability to mimic the taste of sugar. Stevia is a natural sweetener often used as a sugar substitute, not a bulking agent. Agar Agar is a gelatinous substance derived from seaweed, not used as a bulking agent. Caffeine is a stimulant commonly found in coffee and tea, it is not used as a bulking agent in food products.

Commonly used bulking agents are known for being incompletely absorbed and containing fewer calories (2kcal/g) compared to other sources.

Hemiacetals and hemiketals are formed through specific reactions between aldehydes/ketones and alcohols. They are formed due to their increased stability in solution compared to regular aldehydes or ketones, making them important in various chemical processes.

The cyclization of hexose involves the formation of a ring structure, specifically in the form of a hemiacetal or hemiketal. This process is crucial in carbohydrate chemistry to understand the structure and function of different sugars.

Anomers are isomers that differ at a new asymmetric carbon atom formed on ring closure. The two forms used in glucose are alpha (OH down at C1) and beta (OH up at C1). Drawings that show anomers are called Haworth projections, which depict the cyclic structure of monosaccharides.

In alpha D glucose, the OH group on the anomeric carbon (C1) is below the plane of the ring, while in beta D glucose, it is above the plane of the ring. This conformational difference results in distinct chemical properties and biological activities between the two forms.

The question is asking for the anomers, which are a type of diastereomers that differ in the configuration at the anomeric carbon in a cyclic sugar ring. The correct answer is to refer to notes or literature where the specific structures of anomers in a furanose ring are detailed.

D-glucose and D-galactose are structural isomers that only differ in the spatial arrangement of hydroxyl groups on the fourth carbon atom.

Carbohydrates are biomolecules composed of C, H, and O, not N. They are not defined as saturated fats, and the general formula for a hexose carbohydrate is C6(H2O)6.

Carbohydrates typically contain carbonyl (aldose, keto) and hydroxyl functional groups. Other functional groups like amine, carboxylic acid, and sulfhydryl are not commonly found in carbohydrates.

Stereoisomers have the same empirical structure but differ in their spatial arrangement, optical activity, and biological properties. Molecular weight, chemical reactivity, and physical state may vary between stereoisomers.

Enantiomers are a specific type of isomers that are non-superimposable mirror images of each other. The D and L forms refer to the configuration of chiral molecules based on their similarity to D- or L-glyceraldehyde.

A chiral carbon is a carbon atom that has four different groups attached to it, leading to non-superimposable mirror images known as stereoisomers. A chiral carbon plays a crucial role in creating stereoisomers due to its ability to create asymmetry within a molecule, allowing for different spatial arrangements of atoms and molecules.

The number of possible enantiomers per chiral carbon is 2^n, and the number of biologically active is half the number of enantiomers. The incorrect answers provided do not follow this relationship and therefore are incorrect.

In Fischer projections, L and D configurations are determined based on the orientation of the hydroxide groups on the chiral carbon furthest from the carbonyl group. L and D configurations are mirror images of each other.

D-glyceraldehyde is considered the simplest sugar because it is an aldotriose, meaning it has the smallest possible carbon skeleton for a sugar molecule.

D-glucose is considered the most important sugar in the diet as it is the primary source of energy for the body's cells. While other sugars like sucrose, fructose, and maltose are commonly consumed, D-glucose plays a crucial role in metabolism and is directly used by the body for various functions.

D-fructose is considered to be the sweetest of all sugars due to its higher level of sweetness compared to other commonly known sugars like sucrose, glucose, and lactose.

D-galactose is a simple sugar that is found in milk and is a component of lactose.

RNA is composed of a chain of nucleotides, with each nucleotide containing a sugar molecule. In RNA, the sugar molecule is D-ribose, which differs from the sugar molecule in DNA, which is deoxyribose.

A solution of an optical isomer rotates the plane of polarized light in one direction due to its chiral nature.