How did scientists observe metabolic pathways in organisms?

In summary: It's not a textbook, but it's a great resource for people studying this field.In summary, the scientists observed that macromolecules like proteins, carbohydrates and lipids are synthesized from other molecules with intermediate products by living cells. They did this by measuring the conversion of one molecule to another with different types of instrumentation.
  • #1
Aafia
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how the scientists observed that macromolecules like proteins, carbohydrates and lipids are synthesized from other molecules with intermediate products by living cells. Did they observe this under microscope. I want to know this because I am studying bioenergetics and while studying photosynthesis and cellular respiration I have doubt that whether this all stuff is correct or not. I hope that you will help me to clear this doubt.
 
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  • #3
One way - a simple answer:
For photosynthesis - Carbon dioxide + water -> glucose + free oxygen.
If you put plant cells in an environment with carbon dioxide and manufacture the carbon dioxide from radioactive carbon you can see that other new molecules in the cell become radioactive. Why? Because the special carbon dioxide got pulled apart and rearranged into brand new molecules by cell metabolism. What you get in terms of newly created molecules is predictable and matches the expected values for given cellular processes. So you see radioactive glucose for example.

Edit:
Darn. Yggdrasil gave a better scientific answer - mine was based on the level of understanding I saw in the post.
 
  • #4
An "observation" is not necessarily something you "see". It can be something you measure.

For example, ethanol is converted to acetaldehyde in the body. How did they determine this was occurring? First, you start with a model organism in a small space, like a bacteria. You add one substance and measure the other. Then what happened? They dissolved the bacteria, removed the cabohydrates and fats and then purified the proteins.

They took each of these purified proteins and added them to a series of vials.

They added ethanol to each one until they found one vial where where acetaldehyde appeared.

Then, they examine the protein, determine its structure. Now they know how it could interact with an ethanol molecule. They run experiments with the purified protein to measure its performance converting one molecule to the other. They block the enzyme with other molecules to affirm their hypothesis. Their observations confirm this biological molecule converts one chemical to another. This is a metabolic pathway.

Using the same isolation technique they purify the proteins from multiple tissue types, for example, the liver. They discover large amounts of alcohol dehydrogenase in the liver. They take isolated liver cells and subject them to ethanol. It converts to acetaldehyde. But then the acetaldehyde becomes acetic acid, through a different process, but they have localized this enzyme activity to a specific body part.

How the concepts in biochemistry were discovered are are best explained as a combination of approaches: cell biology, cell culture, organic and physical chemistry, microbiology, and molecular biology. The explanation above was just a plausible guess as to how you might determine what enzymes might exist in a cell or organism in a lab. The actual story of how any particular metabolic process was discovered is out there.
 
  • #5
Aafia said:
how the scientists observed that macromolecules like proteins, carbohydrates and lipids are synthesized from other molecules with intermediate products by living cells. Did they observe this under microscope. I want to know this because I am studying bioenergetics and while studying photosynthesis and cellular respiration I have doubt that whether this all stuff is correct or not. I hope that you will help me to clear this doubt.

Optical methods can be used for some things, especially in the mitochondrial respiratory chain- cytochrome redox reactions were studied spectroscopically, with visible light. More typical instrumentation is electrochemical, using species-sensitive electrodes to measure reversal potentials and the like. To be sure, there's a lot more than that- cells need to be fractionated to isolate pure populations of mitochondria, for example.

Since you mentioned bioenergetics, the book "Bioenergetics" by Nicholls and Ferguson is highly readable and provides many experimental details.
 
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Related to How did scientists observe metabolic pathways in organisms?

1. How did scientists first discover metabolic pathways in organisms?

Scientists first began to discover metabolic pathways in organisms through a combination of careful observation and experimentation. They studied the chemical reactions occurring in living organisms and were able to piece together the steps and processes involved in metabolism.

2. What techniques did scientists use to observe metabolic pathways in organisms?

Scientists used a variety of techniques to observe metabolic pathways in organisms, such as biochemical assays, isotopic labeling, and genetic studies. These methods allowed them to track the flow of molecules and identify key enzymes and reactions involved in metabolic processes.

3. How do scientists map out metabolic pathways in organisms?

Scientists use a combination of experimental data and computational models to map out metabolic pathways in organisms. They collect data on the reactions and molecules involved in metabolism and use computer programs to create visual representations of the pathways.

4. What challenges do scientists face when studying metabolic pathways in organisms?

One of the main challenges scientists face when studying metabolic pathways in organisms is the complexity of these pathways. Metabolism involves a large number of interconnected reactions and pathways, making it difficult to isolate and study individual pathways. Additionally, metabolism is highly regulated and can be influenced by a variety of factors, making it challenging to fully understand and predict.

5. How do scientists use their knowledge of metabolic pathways in organisms?

Scientists use their knowledge of metabolic pathways in organisms to gain a better understanding of how living organisms function and to develop new treatments for diseases. By understanding the role of specific metabolic pathways, scientists can target them with drugs or other interventions to treat metabolic disorders and other health conditions.

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