4.1:

4.1: Overview of Metabolism

Overview of Metabolism

JoVE Core
Cell Biology

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JoVE Core Cell Biology

Overview of Metabolism

4.2: Carbohydrate Metabolism

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01:40 min

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April 30, 2023

Overview

Living cells constantly carry out various chemical reactions which are necessary for their proper functioning. These reactions are interlinked to one another via multiple pathways. The collection of these chemical reactions is known as metabolism.

Plant Metabolism

Sunlight, the primary source of energy in plants, is first absorbed by the chlorophyll pigments present in their leaves. Plants then use this energy to carry out photosynthesis, where water is oxidized into oxygen and carbon dioxide is reduced to glucose. Glucose acts as a precursor molecule to synthesize several other metabolites for the growth and survival of the plant. Primary metabolites are chemicals like amino acids and fatty acids, which are essential for the plant’s growth and development. In contrast, secondary metabolites offer survival advantages to the plant. For example, secondary metabolites like terpenes and phenolics are involved in plant defence against microbes and pests, whereas flavonoids are responsible for flower pigmentation.

Animal Metabolism

All animals need food, water and oxygen to grow and reproduce. Here, oxygen acts as an oxidizing agent and the complex food molecules are broken down or catabolized to produce energy in the form of ATP, which is later used for the synthesis of necessary macromolecules or anabolism.

Enzymopathy or inborn errors of metabolism are rare genetic disorders in which the body lacks dedicated enzymes to break specific food molecules. Therefore, people with enzymopathy cannot efficiently utilize specific complex food molecules to produce energy. For example, patients with fructose intolerance disorder lack the enzyme aldolase-B required to metabolize fructose. Similarly, patients with galactosemia lack the enzyme galactose-1-phosphate uridyl transferase (GALT) required to metabolize galactose.

Microbial Metabolism

Microbes obtain energy and carbon from both organic as well as inorganic sources using different metabolic pathways. For example, Bacillus can metabolize organic molecules such as starch and cellulose, while Azotobacter and Rhizobium oxidize inorganic molecules such as nitrogen. Some other types of bacteria like Cyanobacteria contain chlorophyll and hence can produce glucose by photosynthesis.

Transcript

Metabolism can be divided into catabolism and anabolism.

Catabolism is a process where complex food molecules like polysaccharides, lipids, and proteins are broken down into simple molecules, such as sugars, fatty acids, and amino acids.

These simpler molecules are then processed inside a cell via various biochemical pathways to produce ATP, the energy currency of the cell.

For example, starch, a complex carbohydrate, is broken down by digestive enzymes into glucose, which is then metabolized to produce pyruvate and ATP via glycolysis.

Anabolism is the reverse of catabolism. Here, small and simple precursors use energy from ATP hydrolysis to synthesize complex polymers.

For example, in glycogenesis, glucose monomers are bonded together to form glycogen, an energy storage molecule in animals.

Since cells need to generate energy to maintain cellular metabolism, it is important to keep an adequate pool of ATP in the cell by modifying rates of ATP producing and utilizing reactions.

Such balance in the cellular metabolism is achieved via various regulatory systems present in the body like the endocrine system, regulatory enzymes, feedback inhibition loops, and modulation of gene expression patterns.

Key Terms and definitions

Metabolism - The collection of chemical reactions happening within living cells.
Primary Metabolite - Essential chemicals for the growth and development of plants and animals.
Secondary Metabolite - Chemicals that offer survival advantages to the plant.
Enzymopathy - Genetic disorders where the body lacks enzymes to break specific food molecules.
Microbial Metabolism - Energy and carbon obtained by microbes from organic and inorganic sources.

Learning Objectives

Define Metabolism – Explain the collection of chemical reactions within living cells (e.g., metabolism).
Contrast Primary vs Secondary Metabolites – Identify key differences (e.g., essential for growth vs survival benefits).
Explore Example of Enzymopathies – Discuss the lack of specific enzymes in some disorders (e.g., fructose intolerance).
Explain Microbial Metabolism – Glimpse into how microbes obtain energy and carbon.
Apply Metabolites in Context – See how primary and secondary metabolites work for plants and animals.

Questions that this video will help you answer

What is metabolism and how does it help in the functioning of living cells?
What are primary and secondary metabolites?
What is enzymopathy, and how does it affect metabolism?

This video is also useful for

Students – Grasp how metabolism and metabolites support understanding of biology.
Educators – Provides a comprehensive view of metabolism for teaching biology.
Researchers – Understanding of how metabolism works for scientific study.
Science Enthusiasts – Offers insights into metabolism for interest and broader understanding.

Tags

Metabolism Chemical Reactions Plant Metabolism Photosynthesis Primary Metabolites Secondary Metabolites Animal Metabolism Catabolism Anabolism Enzymopathy Inborn Errors Of Metabolism Fructose Intolerance Galactosemia Microbial Metabolism Bacillus Azotobacter Rhizobium Cyanobacteria