Introduction to Metabolism

Objectives

• After the lecture, students should be able to define metabolism.
• After the lecture, students should be able to differentiate between catabolism and anabolism.
• After the lecture, students should be able to determine the relationship between nutrition, metabolism, and energy.

What is Metabolism

• Metabolism refers to the chemical reactions involved in maintaining the living state of cells and organisms.
• Bioenergetics refers to the biochemical or metabolic pathways by which the cell ultimately obtains energy.
• Metabolic pathways allow the basic chemicals from nutrition to be changed through a series of steps into another chemical by a sequence of enzymes.
• Energy is the force or power that enables the body to do its work.
• In the human body, metabolism is illustrated in reactions that break substances down, reactions that produce larger substances from smaller substances, and reactions that chemically modify substances.

Categories of Metabolism

• Catabolism involves the breakdown of molecules to obtain energy.
• Anabolism involves the synthesis of all compounds needed by the cells.

Catabolism vs Anabolism

• Catabolism is destructive metabolism, while anabolism is constructive metabolism.
• Catabolism involves energy-producing pathways, while anabolism involves energy-consuming pathways.
• Catabolism produces the energy needed for all activity in the cells.
• Anabolism supports the growth of new cells, maintenance of body tissues, and storage of energy for future use.
• Catabolism breaks down large molecules (carbohydrates and fats) to release energy.
• Anabolism changes small molecules into larger, more complex molecules of carbohydrates, protein, and fat.

Nutrition, Metabolism, and Fuel

• Nutrition is key to metabolism.
• Metabolic pathways rely on the nutrients that they break down to produce energy.
• The body requires energy from metabolism to produce new proteins and nucleic acids (DNA, RNA), among other nutrients.
• Food provides a variety of substances essential for the building, upkeep, and repair of body tissues and for efficient functioning of the body.
• Metabolic fuels include carbohydrates, lipids (mainly), proteins (to a little extent), glucose, fatty acids, and amino acids. Glucose is the major metabolic fuel for most tissues.

Carbohydrates in Metabolism

• Carbohydrates exist in forms such as starch, sugar, and cellulose (fibers).
• Fibers provide bulk in the diet.
• Starches and sugars provide energy for humans.
• CHO and sugars produce glucose through digestion or metabolism.

Proteins in Metabolism

• Protein is the main tissue builder of the body.
• Proteins aid in cell structure functions and hemoglobin formation, carrying oxygen and enzymes in executing vital reactions and numerous functions of the body.
• Proteins supply nitrogen for DNA and RNA genetic material and energy production.
• Proteins use amino acids to make more proteins.

Fats in Metabolism

• Fats help form the cellular structure.
• Fats form a protective cushion and insulation around vital organs.
• Fats help absorb fat-soluble vitamins.
• Fats provide a reserve storage for energy.

Minerals in Metabolism

• Minerals act as body regulators.
• Minerals play a role in the metabolic pathways of the body.
• There are 25 essential elements in the body.
• There are 50 elements in the body.

Vitamins in Metabolism

• Vitamins are important organic compounds that the body cannot synthesize by itself and must obtain from the diet.
• Key vitamins include Vitamin A, Vitamin B-Thiamine (B1), Riboflavin (B2), Niacin (B3), or Nicotinic acid, and Pantothenic acid (B5).