Cellular respiration is regulated so that cells make enough ATP without wasting resources or losing useful metabolic intermediates. This lesson introduces the main regulatory strategies and follows control through glucose entry, glycolysis, and the conversion of pyruvate to acetyl CoA.
Cells need ATP, but they also need intermediate molecules to build amino acids, proteins, glycogen, lipids, and nucleic acids. If every available carbon compound were continually oxidized to make ATP, cells could lack the building blocks needed for growth and repair. Regulation helps balance energy production with the cell’s other needs.
All flashcards
Why must cellular respiration be regulated?
Regulation balances ATP supply with the cell’s need for intermediates used to build molecules such as amino acids, glycogen, lipids, and nucleic acids.
What is an allosteric effector?
It is a molecule that binds to a regulatory site other than an enzyme’s active site and changes enzyme activity by altering the enzyme’s shape.
How does hexokinase help retain glucose in a cell?
It phosphorylates glucose to glucose-6-phosphate. The charged product does not readily cross the cell membrane, so it is retained for metabolism.
What signals inhibit phosphofructokinase?
High ATP, high citrate, and acidic conditions inhibit phosphofructokinase, signaling that energy is abundant or pathway conditions do not favor more glycolysis.
How is pyruvate dehydrogenase regulated?
ADP and pyruvate favor its activity, while ATP, NADH, and acetyl CoA reduce it. Phosphorylation inactivates the enzyme, and dephosphorylation reactivates it.
Quiz questions
How do ADP, ATP, and NADH regulate isocitrate dehydrogenase?Answer: ADP activates it, while ATP and NADH inhibit it.
Which signals can stimulate α-ketoglutarate dehydrogenase?Answer: ADP and calcium ions can stimulate its activity.
What is the effect of accumulating succinyl CoA on α-ketoglutarate dehydrogenase?Answer: It inhibits the enzyme, slowing conversion of α-ketoglutarate.
How does ADP availability affect the overall rate of electron transport?Answer: More available ADP supports faster ATP synthesis and electron transport.
How can slowing α-ketoglutarate oxidation support biosynthesis?Answer: It can leave more α-ketoglutarate available for glutamate production.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.