Ch. 5 Cell Respiration and Metabolism

These flashcards cover key concepts related to cell respiration and metabolism.

What are the two main categories of metabolism?

Catabolism and Anabolism.

What is the difference between catabolism and anabolism?

Catabolism involves the breakdown of molecules to release energy, while anabolism refers to the synthesis of larger molecules, requiring energy input.

Name three types of organic molecules involved in metabolism.

Proteins, lipids, and carbohydrates.

State a general overview statement about glucose catabolism.

Plasma glucose is dervied from digestion of carbohydrates and is used as a primary energy source for cellular processes.

In the aerobic synthesis of ATP from glucose, who is oxidized and who is reduced?

Glucose becomes oxidized (loses electrons) while oxygen becomes reduced.

What are the stages of cellular respiration?

Glycolysis → Citric Acid Cycle → Electron Transport Chain

In Glycolysis, glucose is broken down into pyruvate, producing 2 ATP and 2 NADH. In Citric Acid Cycle, acetyl-CoA is oxidized, yielding NADH, FADH₂, and ATP. The Electron Transport Chain then uses these carriers to produce a larger amount of ATP through oxidative phosphorylation.

What does glycolysis produce from glucose?

Glycolysis is a metabolic pathway by which glucose is converted into 2 molecules of pyruvate. For each glucose molecule, you’ll get 2 NADH and 2 ATP. This process requires some ATP to begin with.

What is the fate of pyruvic acid in the absence of oxygen?

It is converted to lactic acid. Since there is no oxygen but an adequate amount of glucose, pyruvates undergoes fermentation in which pyruvic acid will get reduced to lactic acid.

What occurs in the Cori Cycle?

During anaerobic respiration, skeletal muscles will convert stored glycogen into glucose 6-phosphate (glucose intermediate) and subsequently into pyruvate through the glycolysis process. If oxygen is limited, pyruvate is converted to lactic acid. The lactic acid then leaves the skeletal muscle cell and enters the bloodstream, traveling to the liver. Liver will then take the lactic acid and convert it back into glucose through glycolysis in reverse. Liver has the ability to take the glucose and transport back to the skeletal muscle through the bloodstream. This cycle helps to recycle lactic acid back into glucose for energy use and keep the acidity levels down.

Explain what occurs in aerobic respiration.

In glycolysis, pyruvate is formed. Then, it’s converted into an acetyl coA through pyruvate oxidation. The acetyl coA enters the citric acid cycle where it's further oxidized, producing NADH and FADH2 (reduced coenzymes), which provide electrons that are used in the electron transport chain to generate a large amount of ATP. Oxygen is the final electron acceptor in this process.

Explain what occurs in Pyruvate Oxidation

During pyruvate oxidation, pyruvate is transported into the mitochondria where it is oxidized by NAD+, releasing carbon dioxide. A molecule of NADH is generated, and the remaining two-carbon fragment is converted into acetyl CoA, which enters the citric acid cycle for further energy production.

Explain what occurs in the Citric Acid Cycle.

Acetyl CoA is the initial substrate that enters the Citric Acid Cycle, where itundergoes a series of oxidations, releasing carbon dioxide and producing NADH, FADH2, and ATP, which are essential for energy production in cellular respiration.

Explain what occurs in Oxidative Phosphorylation.

Oxidative phosphorylation is the final stage of cellular respiration where electrons from NADH and FADH2 are transferred through the electron transport chain,leading to the pumping of protons across the mitochondrial membrane. The first pump will oxidize NADH and uses that energy to pump ions from the matrix to the intermembrane space. These electrons are further oxidized and passed down through the remaining pumps. This creates a proton gradient that drives ATP synthesis through ATP synthase, with oxygen acting as the final electron acceptor, producing water.

What is the magnitude difference of ATP synthesis when oxygen is around vs when' it’s not around?

In the presence of oxygen, there is 16x as much ATP vs when oxygen is not around.

In metabolism, what is glycogenolysis?

The process of breaking down glycogen into glucose molecules for energy, primarily occurring in the liver and muscles.

In metabolism, what is glycologenesis?

The synthesis of glycogen from glucose.

Why is Acetyl CoA considered a magic molecule?

Acetyl CoA is considered a "magic molecule" because it serves as a crucial metabolic intermediate that connects various biochemical pathways, including the citric acid cycle and fatty acid synthesis, facilitating energy production from carbohydrates, fats, and proteins.

What is lipogenesis (lipid anabolism)?

Synthesis of fatty acids and triglycerides from Acetyl CoA and a glycolysis intermediate. If you have Acetyl CoA, you can stick on a chain to form a fatty acid. Glycerol can be formed from a glycolysis intermediate, which is then combined with fatty acids to form triglycerides.

What happens to fatty acids during β-oxidation?

Fatty acids are cleaved two at a time to produce Acetyl-CoA. Acetyl-CoA will then enter the Citric Acid Cyclefor further oxidation, generating NADH and FADH2. A single fatty acids molecule can produce 3.5-4x ATP as glucosewhen fully oxidized.

Explain amino acid catabolism

In a severe starvation state, the brain reverts to using amino acids for energy production after depleting glycogen and fat reserves. The body will metabolize ketone bodies for energy.

What is the preferred energy source for the brain?

Blood Glucose.

They CANNOT use fatty acids as an energy source

What energy source do skeletal muscles prefer?

Skeletal muscles prefer fatty acids but can use glucose as an energy source.

What are ketone bodies?

They are water-soluble molecules produced by the liver from fatty acids during periods of low carbohydrate availability, serving as an alternative energy source.

What is ketosis?

High levels of ketone bodies in the blood due to the breakdown of fats for energy when carbohydrate intake is low.