Lec 23: Cellular Respiration
Big Picture of Cellular Respiration
A series of enzyme catalyzed reactions that break down glucose to release energy
→ That energy is used in the electron transport chain to make
ATP
Catabolic reactions — breaking down glucose — release energy
→ Anabolic reaction — using energy released by catabolic reactions to build
ATP
→
Ultimate goal of cellular respiration is to make ATP
All cells use ATP to power the work that they do. Remember that the hydrolysis
of ATP releases energy. That energy is used by the cell to do everything it needs to do to keep it alive
● But cells can’t store ATP, so they have to make it constantly
There are high energy electrons that get released through the breakdown of glucose that get used to
power an enzyme called ATP synthase to make ATP.
Where is ATP synthase located?
● ATP synthase is coupled with a membrane channel that
is embedded in the inner membrane of the mitochondria
● Blue areas = intermembrane space
How does ATP synthase work?
● There is a hydrogen ion gradient that is built up inside the intermembrane space. The high
concentration of H+ causes H+ to flow through the membrane channel and that spins ATP
synthase, It works in the same way flowing water spins a water mill
○ Hydrogen ion gradient ⇒ Higher concentration of hydrogen ions in the intermembrane
space than in the matrix, and these hydrogen atoms (because flowing down
concentration gradient) flow through the membrane channel
○ Causing ATP synthase to spin
● H+ ions spinning ATP synthase provides the power needed to synthesize ATP:
○ ADP + Pi → ATP
, 1. As the concentration of ATP increases, ATP synthase will
a. Speed up
b. Slow down
c. Maintain the same rate
2. If the hydrogen ion gradient in the intermembrane space increases, ATP synthase will
a. Speed up
b. Slow down
c. Maintain the same rate
The hydrogen gradient powers ATP synthase…so what builds and maintains the H+ gradient?
● The H+ gradient is built up by a series of molecules called the electron transport chain that are
also embedded in the inner membrane. These molecules drive H+ from the matrix to the
intermembrane system
Practice:
1. True or False? The molecules of the electron transport chain must use energy to drive H+ to the
intermembrane space and maintain the high concentration there.
a. You are maintaining a high concentration, so they must use energy to make this
happen
2. What kind of transport are the molecules of the electron transport chain using to create and
maintain the H+ gradient?
a. Active transport - move through the cell membrane against their concentration gradient
(from low to high) through a protein channel and uses energy
The molecules of the electron transport chain get their energy from the breakdown of glucose
→ “Energy”
= talking
about high
Big Picture of Cellular Respiration
A series of enzyme catalyzed reactions that break down glucose to release energy
→ That energy is used in the electron transport chain to make
ATP
Catabolic reactions — breaking down glucose — release energy
→ Anabolic reaction — using energy released by catabolic reactions to build
ATP
→
Ultimate goal of cellular respiration is to make ATP
All cells use ATP to power the work that they do. Remember that the hydrolysis
of ATP releases energy. That energy is used by the cell to do everything it needs to do to keep it alive
● But cells can’t store ATP, so they have to make it constantly
There are high energy electrons that get released through the breakdown of glucose that get used to
power an enzyme called ATP synthase to make ATP.
Where is ATP synthase located?
● ATP synthase is coupled with a membrane channel that
is embedded in the inner membrane of the mitochondria
● Blue areas = intermembrane space
How does ATP synthase work?
● There is a hydrogen ion gradient that is built up inside the intermembrane space. The high
concentration of H+ causes H+ to flow through the membrane channel and that spins ATP
synthase, It works in the same way flowing water spins a water mill
○ Hydrogen ion gradient ⇒ Higher concentration of hydrogen ions in the intermembrane
space than in the matrix, and these hydrogen atoms (because flowing down
concentration gradient) flow through the membrane channel
○ Causing ATP synthase to spin
● H+ ions spinning ATP synthase provides the power needed to synthesize ATP:
○ ADP + Pi → ATP
, 1. As the concentration of ATP increases, ATP synthase will
a. Speed up
b. Slow down
c. Maintain the same rate
2. If the hydrogen ion gradient in the intermembrane space increases, ATP synthase will
a. Speed up
b. Slow down
c. Maintain the same rate
The hydrogen gradient powers ATP synthase…so what builds and maintains the H+ gradient?
● The H+ gradient is built up by a series of molecules called the electron transport chain that are
also embedded in the inner membrane. These molecules drive H+ from the matrix to the
intermembrane system
Practice:
1. True or False? The molecules of the electron transport chain must use energy to drive H+ to the
intermembrane space and maintain the high concentration there.
a. You are maintaining a high concentration, so they must use energy to make this
happen
2. What kind of transport are the molecules of the electron transport chain using to create and
maintain the H+ gradient?
a. Active transport - move through the cell membrane against their concentration gradient
(from low to high) through a protein channel and uses energy
The molecules of the electron transport chain get their energy from the breakdown of glucose
→ “Energy”
= talking
about high
