Regulating Cellular Respiration Quiz

Regulating Cellular Respiration and Metabolic Pathways

• Study questions in the text are:
  • How does the cell control the rate at which it produces ATP?
  • Explain how proteins and lipids can be used for energy.

Regulation of Aerobic Respiration

• Rate of cellular respiration depends on:
  • Supply and demand
  • High demand during exercise
  • Low demand when resting
• Basal metabolic rate (BMR):
  • Amount of energy expended per unit time at rest
  • Measured in oxygen consumption
  • BMR varies by age and sex (data provided in a chart)

Regulation of Aerobic Catabolic Pathways

• Feedback inhibition:
  • A process for cells to ensure sufficient product when biochemical reactions occur
  • The product of the last reaction inhibits the enzyme catalyzing the first reaction
  • Ensures enough product for reactions, reduces unnecessary reactions

Feedback Inhibition of Enzymes in Aerobic Respiration

• Many enzymes in glycolysis and Krebs cycle are controlled by feedback inhibition of ATP and NADH
• Phosphofructokinase (PFK) is the main control point for glycolysis
• ATP inhibits PFK which means sufficient ATP causes inhibition for enough product
• Citrate inhibits PFK, causing an accumulation of the substance when conversion to Acetyl-CoA does not occur until sufficient citrate is used by other steps

Pyruvate Dehydrogenase

• Inhibited by NADH
• Slows down conversion of pyruvate to Acetyl-CoA and CO2

Other Factors Affecting Rate of Reaction

• Temperature: Higher temperature leads to faster reactions
• Nutrient concentration: Higher concentration leads to faster reactions
• Availability of oxygen

Interconnections of Metabolic Pathways

• Mitochondria harvest energy from one molecule of glucose
• Carbohydrates can be broken down into glucose and enter glycolysis
• Other macromolecules (not carbohydrates) also have metabolic pathways

Protein Catabolism

• Proteins first broken down to amino acids (hydrolysis)
• Before feeding into glycolysis or Krebs cycle, amino groups must be removed
• Deamination: removal of the amino group (-NH2) from amino acids
• Amino acids can feed into different points of glycolysis or Krebs cycle through different processes
• Process occurs in the liver
• Amine group converted into ammonia (toxic), then to urea (harmless)
• Urea is excreted by kidneys
• Amine groups can be transferred to other amino acids (transamination)
• Remaining carbon skeletons can feed into different points of glycolysis or Krebs cycle

Lipid Catabolism

• Fat molecules broken down into glycerol and fatty acids

• Two glycerol molecules combine to form one glucose molecule (gluconeogenesis)

• Glycerol is converted into Glyceraldehyde 3-Phosphate (a precursor to pyruvate)

• Fatty acids undergo beta-oxidation to become Acetyl-CoA

• Carbon atoms are removed 2 at a time

• Each 2-carbon unit becomes an acetyl Co-A for use in the Krebs Cycle

• Cleavage of fatty acids uses 1 ATP, Produces 1 NADH, 1 FADH2

• The amount of ATP yield from a particular fatty acid structure relates to the number of carbons it contains, in multiples of 2

Discussion Question

• Calculate ATP production from a 14 Carbon Fatty acid chain

Summary

• Carbohydrates, some amino acids, and glycerol enter the metabolic pathway through glycolysis
• Pyruvate oxidation leads to the citric acid cycle
• Oxidative phosphorylation occurs next to complete the process

Test your knowledge on how cellular respiration is regulated, including the production of ATP and the roles of proteins and lipids in energy metabolism. This quiz covers key concepts such as supply and demand during exercise, basal metabolic rate, and feedback inhibition in aerobic pathways.