What is the function of starch in plants?

Question

iii. What is the function of glycogen in humans?
iv. Not all carbohydrates are digestible by humans
● There are unique polysaccharides that are indigestible by
humans, but can serve as structural material for various
organisms. Give an example of where each of the following is
found.
○ Chitin:
○ Cellulose:
● Why is cellulose an important part of the human diet even
though humans cannot digest it?
20. Lipids: Multifunctional Macromolecules
Lipids are a large, diverse group of macromolecules with important functions.
a. What are some functions of lipids?
b. Dietary fats differ in degrees of saturation
i. The fats we are concerned about in the foods we eat are also called

Answer 1

1. Functions of Starch and Glycogen

i. Function of Starch in Plants: Starch functions as a primary energy storage form in plants. It is composed of long chains of glucose molecules, which can be broken down into glucose when the plant requires energy for growth, development, and metabolism. Starch is stored mainly in non-photosynthetic tissues such as roots, tubers, and seeds, providing energy reserves that the plant can utilize during periods when photosynthesis is not occurring.

ii. Function of Glycogen in Humans: Glycogen is the main storage form of glucose in humans and is primarily found in the liver and muscle tissues. It serves as a quickly accessible energy reservoir. When blood glucose levels decrease or when energy is needed for muscular activity, glycogen can be rapidly broken down into glucose and released into the bloodstream or used by muscle cells for immediate energy.

2. Indigestible Polysaccharides and Their Locations

iii. Example of Unique Indigestible Polysaccharides:

• Chitin:
  Chitin is a polysaccharide that serves as a structural component in the exoskeletons of arthropods (such as insects, crabs, and lobsters) and in the cell walls of fungi.

• Cellulose:
  Cellulose is a major component of the cell walls in green plants, algae, and some bacteria. It provides structural support and rigidity to plant cells.

3. Importance of Cellulose in the Human Diet

iv. Why Cellulose is Important: Even though humans cannot digest cellulose due to a lack of the necessary enzymes, it plays a crucial role in the diet as a form of dietary fiber. Cellulose contributes to digestive health by adding bulk to stools, promoting regular bowel movements, and preventing constipation. It also helps maintain a healthy gut microbiome and can aid in cholesterol regulation and blood sugar control.

4. Functions of Lipids

a. Functions of Lipids: Lipids serve numerous important functions in biological systems, including:

• Energy storage: Lipids, particularly triglycerides, provide a dense source of energy storage in adipose tissue.
• Structural components: Phospholipids are essential in forming cell membranes, providing compartmentalization within the cell.
• Insulation: Lipids help insulate the body and maintain temperature homeostasis.
• Protection: Lipids can form protective barriers, e.g., the waxy cuticle on plant leaves or the fatty layers protecting organs.
• Signaling: Certain lipids act as hormones or signaling molecules (e.g., steroid hormones, lipid mediators).
• Nutrient absorption: Lipids facilitate the absorption of fat-soluble vitamins (A, D, E, K).

5. Dietary Fats and Saturation

b. i. Dietary fats we are concerned about in foods: The dietary fats most commonly assessed in terms of health impact are often referred to as triglycerides. Additionally, they can be categorized as saturated and unsaturated fats. The unsaturated fats include monounsaturated and polyunsaturated fats, which are generally considered healthier compared to saturated fats and trans fats, which are often linked to health risks when consumed in excess.