Bioquímica - Aula 11 - Catabolismo - Carboidratos

Summary

In this lesson on biochemistry, Professor Ângelo Celaz delves into the topic of catabolism, particularly focusing on carbohydrates. He explains the two types of organisms based on energy sources: phototrophs, which rely on light, and chemotrophs, which obtain energy from compound oxidation. The professor also introduces essential coenzymes like FAD and NAD, which play crucial roles in metabolic reactions. The core of the lecture covers glycolysis, the breakdown of glucose into pyruvate, highlighting the reactions and the formation of ATP. The lesson provides a detailed look at how cells process carbohydrates to generate energy, paving the way for more advanced metabolic processes.

Takeaways

• 😀 Catabolism is a metabolic process aimed at producing energy for living organisms to stay alive, breaking down nutrients like carbohydrates, lipids, and proteins.
• 😀 Organisms can be classified into phototrophs (which obtain energy from sunlight) and chemotrophs (which obtain energy from the oxidation of compounds in the environment).
• 😀 Most living organisms, including humans, are chemio-organotrophic, meaning they obtain energy primarily from organic compounds like carbohydrates, lipids, and proteins.
• 😀 Aerobic organisms, like humans, rely on food (carbohydrates, lipids, proteins) to produce carbon dioxide, protons, and electrons, which are transferred to coenzymes for energy production.
• 😀 Coenzymes like FAD (Flavin Adenine Dinucleotide) and NAD (Nicotinamide Adenine Dinucleotide) play essential roles in energy production, receiving electrons and protons during metabolic reactions.
• 😀 In aerobic respiration, oxygen is reduced by accepting electrons and protons, forming water, and allowing coenzymes to become oxidized again to continue the energy production cycle.
• 😀 Carbohydrates are a major source of energy, and most of the carbohydrates in our diet come from starch, which is broken down into glucose during digestion.
• 😀 The breakdown of glucose begins in the mouth with saliva, and continues in the digestive system, turning complex carbohydrates into monosaccharides (simple sugars) for absorption into the bloodstream.
• 😀 Glycolysis is the process by which glucose (a six-carbon molecule) is broken down into two three-carbon molecules called pyruvate, generating ATP and NADH in the process.
• 😀 Glycolysis involves a series of reactions that convert glucose into energy, and these reactions are common to all organisms, including humans and plants.

Q & A

What is catabolism, and what is its purpose in organisms?

Catabolism is a series of metabolic reactions aimed at producing energy for organisms. It involves breaking down molecules to release energy, which is essential for maintaining life.

What are the two main types of organisms based on how they obtain energy?

The two main types of organisms based on energy acquisition are phototrophs, which obtain energy from light (usually sunlight), and chemotrophs, which acquire energy through the oxidation of compounds in the environment.

What is the role of coenzymes like FAD and NAD in metabolism?

Coenzymes such as FAD and NAD are essential in transferring electrons and protons during oxidation-reduction reactions. FAD, derived from vitamin B2, and NAD, derived from vitamin B3, help in the reduction and oxidation cycles necessary for metabolic processes.

How does the process of glycolysis begin?

Glycolysis begins with the breakdown of glucose, a six-carbon molecule, into two molecules of three-carbon compounds called pyruvate. This process occurs in the cytoplasm of cells.

What are the key enzymes involved in the first steps of glycolysis?

The first steps of glycolysis involve the phosphorylation of glucose to form glucose-6-phosphate, catalyzed by hexokinase, and the isomerization of glucose-6-phosphate to fructose-6-phosphate, catalyzed by phosphoglucose isomerase.

What is the significance of ATP in the glycolysis process?

ATP is used in the early steps of glycolysis to activate glucose and convert it into glucose-6-phosphate. This investment of energy is crucial for the subsequent breakdown of glucose and production of additional ATP later in the process.

What is the role of NADH in glycolysis?

During glycolysis, NADH is produced as glucose is oxidized. NAD+ accepts electrons and a proton to become NADH, which will later be used in other metabolic pathways to produce ATP.

What happens to the energy released during glycolysis?

The energy released during glycolysis is stored in the form of ATP and NADH. ATP is used immediately by the cell for energy, while NADH will participate in the electron transport chain to produce more ATP.

How does the reaction of glucose to glucose-6-phosphate in glycolysis work?

In the first reaction of glycolysis, glucose reacts with ATP, transferring a phosphate group to glucose. This forms glucose-6-phosphate, and ADP is produced in the process.

What happens after the formation of fructose-1,6-bisphosphate in glycolysis?

After the formation of fructose-1,6-bisphosphate, it is cleaved into two three-carbon molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P). These molecules continue through the rest of the glycolytic pathway to form pyruvate.