Help with Mitochondria Structure
Help Questions
GRE Subject Test: Biochemistry, Cell, and Molecular Biology › Help with Mitochondria Structure
Crucial steps of the citric acid cycle and the electron transport chain occur within the mitochondria. Which of the following pairs of answers contains an enzyme essential to ATP synthesis, and its correct mitochondrial localization?
ATP synthase, inner mitochondrial membrane
ATP synthase, outer mitochondrial membrane
ADP phosphorylase, inner mitochondrial membrane
ADP phosphatase, mitochondrial cristae
ATP reductase, mitochondrial cristae
Explanation
ATP synthase is the correct enzyme, and it is powered by a 
In what part of mitochondria does the electron transport chain take place?
Inner membrane
Intermembrane space
Outer membrane
Thylakoid space
Matrix
Explanation
While the matrix, outer membrane, and intermembrane spaces are components of mitochondria, the correct answer is inner membrane. The thylakoid space is found in chloroplasts not mitochondria. Compounds are embedded in the inner membrane and transfer electrons from electron donors to electron acceptors by redox reactions. The final enzyme in the chain is ATP synthase, which generates ATP from ADP and inorganic phosphate.
Where does the Krebs cycle take place in the mitochondria?
Mitochondrial matrix
Inner mitochondrial membrane
Outer mitochondrial membrane
Intermembrane space
Explanation
The mitochondrion is a double-membraned organelle responsible for generating ATP for the cell. The Krebs cycle is the middle step of cellular respiration, and takes place in the mitochondrial matrix.
What is the primary purpose of cristae in the mitochondria?
Provide a large surface area for chemical reactions
Prevent the mitochondria from folding in on itself
Protect the mitochondrial genome
No purpose has yet been identified; they are likely an evolutionary remnant
Explanation
The importance of the cristae comes from the fact that they greatly increase the surface area of the inner membrane of the mitochondria. This is important because this membrane houses the electron transport chain proteins. A larger surface area allows reactions to occur at a higher rate and, thus, more ATP can be generated. The cristae are not essential to protecting the mitochondrial genome or maintaining shape.