Carbohydrates, Chirality and Stereoisomerism

What are carbohydrates commonly referred to as, and why?

Carbohydrates are commonly referred to as saccharides because of the sweet taste of many carbohydrates (from Latin, saccharum, meaning sugar).

What are the three naturally present sugars that contribute to the sweetness of ripe peaches?

The three naturally present sugars are fructose, glucose, and sucrose.

What is the difference between bioinorganic and bioorganic substances?

Bioinorganic substances do not contain carbon (e.g., water, inorganic salts), whereas bioorganic substances contain carbon (e.g., proteins, lipids, carbohydrates, nucleic acids).

What is the primary function of carbohydrates in green plants?

Green plants produce carbohydrates via photosynthesis, using them mainly in the form of cellulose (structural element) and starch (energy reserve).

What is the role of chlorophyll in carbohydrate production?

Chlorophyll, found in green plants, is essential for photosynthesis, the process by which plants convert CO₂ and H₂O into carbohydrates using solar energy.

What are the two main forms of carbohydrates in plants, and what are their functions?

Cellulose acts as a structural element, while starch serves as an energy reserve.

What happens during carbohydrate breakdown in the human body?

Carbohydrates are broken down into simpler sugars, absorbed into the bloodstream, and insulin is released to help store excess glucose as glycogen.

What are the conditions associated with high and low blood sugar levels?

Hyperglycemia refers to elevated levels of sugar in the blood, while hypoglycemia refers to low levels of sugar in the blood.

What is the difference between monosaccharides and disaccharides?

Monosaccharides are single polyhydroxy aldehydes or ketones (e.g., glucose, fructose), while disaccharides are two monosaccharides that are covalently bonded (e.g., sucrose, lactose).

What are oligosaccharides, and how many monosaccharide units do they typically contain?

Oligosaccharides are carbohydrates composed of 2 to 10 monosaccharide units covalently bonded (e.g., galactose, maltose).

What are polysaccharides, and what are some examples?

Polysaccharides are carbohydrates composed of many monosaccharide units covalently bonded. Examples include cellulose, starch, and glycogen.

What is the significance of the aldehyde and ketone groups in carbohydrates?

The aldehyde group (CHO) and ketone group (C=O) are functional groups that define the structure of carbohydrates, with glucose being a polyhydroxy aldehyde and fructose being a polyhydroxy ketone.

What is the difference between superimposable and nonsuperimposable mirror images?

Superimposable mirror images have all points coinciding when laid upon each other (e.g., achiral objects like a flask), while nonsuperimposable mirror images do not coincide at all points (e.g., chiral objects like hands).

Why is molecular handedness important in biological systems?

Right-handed and left-handed forms of a molecule often elicit different responses in the body. Naturally occurring monosaccharides are always right-handed, while amino acids are always left-handed.

What is the difference between enantiomers and diastereomers?

Enantiomers are nonsuperimposable mirror images of each other, while diastereomers are molecules that are not mirror images of each other (e.g., cis-trans isomers).

What is the Fischer projection formula used for?

The Fischer projection formula is used to represent the spatial arrangement of groups around chiral centers in two dimensions, showing the tetrahedral arrangement of bonds.

How do you determine the D or L configuration of a carbohydrate?

The D or L configuration is determined by the orientation of the -OH group on the chiral center farthest from the carbonyl group. If the -OH is on the right, it is D; if on the left, it is L.

What is the difference between constitutional isomers and stereoisomers?

Constitutional isomers have different connectivity of atoms (e.g., skeletal, positional, functional group isomers), while stereoisomers have the same connectivity but differ in spatial arrangement (e.g., enantiomers, diastereomers).

What are the three types of constitutional isomers?

Skeletal isomers have different carbon atom arrangements, positional isomers differ in the location of the functional group, and functional group isomers contain different functional groups.

What is the difference between an atom and a molecule?

An atom is the smallest unit of matter that cannot be broken down chemically (e.g., oxygen, hydrogen), while a molecule is a group of two or more atoms bonded together (e.g., O₂, H₂O).

What is the difference between an element and a compound?

An element is a pure substance made up of only one type of atom (e.g., oxygen, carbon), while a compound is made of two or more different elements chemically bonded together (e.g., H₂O, CO₂).

What is an isomer?

An isomer is a molecule that has the same chemical formula but a different arrangement of atoms (e.g., glucose and fructose, both C₆H₁₂O₆).

What is the difference between hydrolysis and dehydration synthesis?

Hydrolysis breaks down molecules by reacting with water, while dehydration synthesis forms larger molecules by removing water.

What is the role of carbohydrates in cell membranes?

Carbohydrates linked to lipids form structural components of cell membranes and are involved in cell-cell and cell-molecule recognition processes.

What is the difference between cellulose and starch in plants?

Cellulose provides structural support in plant cell walls, while starch serves as an energy reserve in plants.

What is the difference between glucose and fructose?

Glucose is a polyhydroxy aldehyde, whereas fructose is a polyhydroxy ketone.

What is the difference between glycogen and starch in humans?

Glycogen is the storage form of glucose in animals (short-term energy reserve), while starch is the storage form of glucose in plants.

What is the difference between cis-trans isomers and enantiomers?

Cis-trans isomers are diastereomers that differ in spatial arrangement around a double bond or ring, while enantiomers are nonsuperimposable mirror images of each other.

What is the difference between dextro (D) and levo (L) configurations?

Dextro (D) has the -OH group on the right side of the chiral center, while levo (L) has the -OH group on the left side of the chiral center.

What is the difference between a chiral center and an achiral center?

A chiral center has four different groups attached to it, creating handedness, whereas an achiral center does not have four different groups attached, so it lacks handedness.

What is the difference between a monosaccharide and a polysaccharide?

A monosaccharide is a single sugar unit (e.g., glucose), while a polysaccharide consists of many sugar units bonded together (e.g., cellulose, starch).

What is the difference between a ketone and an aldehyde group?

A ketone group has C=O located within the carbon chain, while an aldehyde group has C=O located at the end of the carbon chain.

What is the difference between a chiral molecule and an achiral molecule?

A chiral molecule has nonsuperimposable mirror images (e.g., hands), while an achiral molecule has superimposable mirror images (e.g., a flask).

What is the difference between a structural isomer and a stereoisomer?

A structural isomer has atoms with different connectivity, while a stereoisomer has atoms with the same connectivity but differs in spatial arrangement.

What is the process of photosynthesis?

Photosynthesis is the process by which green plants convert carbon dioxide and water into glucose and oxygen using sunlight, primarily facilitated by chlorophyll.

What role do carbohydrates play in energy metabolism?

Carbohydrates serve as the primary source of energy for most living organisms, which is converted into glucose and utilized by cells.

What are glycoproteins and their role in cells?

Glycoproteins are proteins that have carbohydrate groups attached to them, important for cell recognition, signaling, and immune responses.

What is the function of dietary fiber, and where is it found?

Dietary fiber is a type of carbohydrate that aids in digestive health and is found in fruits, vegetables, whole grains, and legumes.

How are carbohydrates classified based on their complexity?

Carbohydrates are classified into three groups based on their complexity: monosaccharides (simple sugars), oligosaccharides (short chains of sugars), and polysaccharides (long chains of sugars).

What is the glycemic index and its significance?

The glycemic index (GI) measures how quickly carbohydrate-containing food raises blood sugar levels, influencing diet and diabetes management.

What is the role of insulin in carbohydrate metabolism?

Insulin is a hormone that helps regulate blood sugar levels by facilitating the uptake of glucose into cells for energy or storage.

What are some sources of complex carbohydrates?

Sources of complex carbohydrates include whole grains, legumes, and starchy vegetables, which provide sustained energy and fiber.

What is the importance of carbohydrates in food labeling?

Carbohydrates are an essential component of food labels, informing consumers about the nutritional content, including total carbohydrates, sugars, and fiber.

What enzyme is responsible for breaking down carbohydrates in the digestive system?

Amylase is the enzyme responsible for breaking down carbohydrates into simpler sugars during digestion.

What are simple carbohydrates and where are they commonly found?

Simple carbohydrates consist of one or two sugar units and are commonly found in fruits, milk, and sweeteners like sugar and honey.

What is a common consequence of excessive consumption of simple carbohydrates?

Excessive consumption of simple carbohydrates can lead to weight gain and higher risk of type 2 diabetes.

How do carbohydrates affect blood sugar levels post-meal?

Carbohydrates can cause a rapid increase in blood sugar levels, followed by insulin release to help stabilize those levels.

What type of carbohydrate is lactose and where is it found?

Lactose is a disaccharide found in milk and dairy products.

What role do carbohydrates play in athletic performance?

Carbohydrates are a primary source of energy for athletes, providing fuel for high-intensity activities.

What is dietary fiber, and how does it benefit health?

Dietary fiber is a type of carbohydrate that aids digestion, promotes satiety, and helps regulate blood sugar levels.

What happens to excess carbohydrates in the body?

Excess carbohydrates are converted to fat for storage in adipose tissue when glycogen stores are full.

What are resistant starches and their benefits?

Resistant starches are not fully digested in the small intestine and can improve gut health and increase feelings of fullness.

What is the relationship between carbohydrates and fat in energy provision?

Carbohydrates are often the preferred energy source for immediate needs, while fats serve as a reserve energy source.