Answer
**Defining Characteristics of Carbohydrates:**
Carbohydrates are a class of organic compounds with specific defining characteristics:
1. **Composition:** Carbohydrates are composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The ratio of hydrogen to oxygen atoms is typically 2:1, which is similar to water (H2O). The general formula for carbohydrates is (CH2O)n, where "n" is the number of carbon atoms.
2. **Polyhydroxy Aldehydes or Ketones:** Carbohydrates contain one or more polyhydroxy aldehyde or ketone functional groups. This means they have multiple hydroxyl (-OH) groups and either an aldehyde (-CHO) or ketone (>C=O) group.
3. **Solubility in Water:** Most carbohydrates are soluble in water due to the presence of polar hydroxyl groups, which can form hydrogen bonds with water molecules.
**Principal Roles of Carbohydrates in the Body:**
Carbohydrates serve several essential roles in the body:
1. **Energy Source:** Carbohydrates are a primary source of energy for the body. When consumed, they are broken down into glucose, which can be used by cells for energy production through cellular respiration. Glucose is especially critical for the brain and red blood cells, which rely on it as their primary energy source.
2. **Energy Storage:** Excess glucose is converted into glycogen and stored in the liver and muscles. When blood glucose levels drop (e.g., between meals or during physical activity), glycogen is broken down into glucose to maintain blood sugar levels.
3. **Structural Support:** Carbohydrates are important structural components in various biological molecules. In plants, cellulose (a complex carbohydrate) provides structural support to the cell walls. Chitin, another carbohydrate, forms the exoskeletons of arthropods and cell walls in fungi.
4. **Cell-Cell Recognition:** Carbohydrates on the surface of cells play a crucial role in cell-cell recognition and communication. They are involved in processes such as immune responses, cell adhesion, and signaling.
5. **Dietary Fiber:** Some carbohydrates, like dietary fiber, are not digested by human enzymes. However, they are essential for maintaining digestive health. Fiber adds bulk to the diet, aids in bowel regularity, and can help lower the risk of certain gastrointestinal disorders.
6. **Flavor and Sweetness:** Carbohydrates, particularly simple sugars like glucose, fructose, and sucrose, provide sweet flavors in foods. This sweetness is often used to enhance the palatability of foods and beverages.
7. **Intermediate Metabolism:** Carbohydrates can be converted into intermediates that participate in various metabolic pathways. For example, glucose can be converted into pentose sugars, which are essential for nucleic acid (DNA and RNA) synthesis.
In summary, carbohydrates are vital macronutrients that serve as a primary energy source, play structural roles, and are involved in various physiological processes. They are a fundamental component of a balanced diet and contribute to the overall health and function of the body.
Work Step by Step
**Defining Characteristics of Carbohydrates:**
Carbohydrates are a class of organic compounds with specific defining characteristics:
1. **Composition:** Carbohydrates are composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The ratio of hydrogen to oxygen atoms is typically 2:1, which is similar to water (H2O). The general formula for carbohydrates is (CH2O)n, where "n" is the number of carbon atoms.
2. **Polyhydroxy Aldehydes or Ketones:** Carbohydrates contain one or more polyhydroxy aldehyde or ketone functional groups. This means they have multiple hydroxyl (-OH) groups and either an aldehyde (-CHO) or ketone (>C=O) group.
3. **Solubility in Water:** Most carbohydrates are soluble in water due to the presence of polar hydroxyl groups, which can form hydrogen bonds with water molecules.
**Principal Roles of Carbohydrates in the Body:**
Carbohydrates serve several essential roles in the body:
1. **Energy Source:** Carbohydrates are a primary source of energy for the body. When consumed, they are broken down into glucose, which can be used by cells for energy production through cellular respiration. Glucose is especially critical for the brain and red blood cells, which rely on it as their primary energy source.
2. **Energy Storage:** Excess glucose is converted into glycogen and stored in the liver and muscles. When blood glucose levels drop (e.g., between meals or during physical activity), glycogen is broken down into glucose to maintain blood sugar levels.
3. **Structural Support:** Carbohydrates are important structural components in various biological molecules. In plants, cellulose (a complex carbohydrate) provides structural support to the cell walls. Chitin, another carbohydrate, forms the exoskeletons of arthropods and cell walls in fungi.
4. **Cell-Cell Recognition:** Carbohydrates on the surface of cells play a crucial role in cell-cell recognition and communication. They are involved in processes such as immune responses, cell adhesion, and signaling.
5. **Dietary Fiber:** Some carbohydrates, like dietary fiber, are not digested by human enzymes. However, they are essential for maintaining digestive health. Fiber adds bulk to the diet, aids in bowel regularity, and can help lower the risk of certain gastrointestinal disorders.
6. **Flavor and Sweetness:** Carbohydrates, particularly simple sugars like glucose, fructose, and sucrose, provide sweet flavors in foods. This sweetness is often used to enhance the palatability of foods and beverages.
7. **Intermediate Metabolism:** Carbohydrates can be converted into intermediates that participate in various metabolic pathways. For example, glucose can be converted into pentose sugars, which are essential for nucleic acid (DNA and RNA) synthesis.
In summary, carbohydrates are vital macronutrients that serve as a primary energy source, play structural roles, and are involved in various physiological processes. They are a fundamental component of a balanced diet and contribute to the overall health and function of the body.
