Mitochondria and Chloroplasts Questions and Answers

Q: The folds of the inner mitochondrial membrane are called

Correct answer: cristaeThe cristae are the infoldings of the inner mitochondrial membrane, and their number and depth track how much oxidative work the cell does - a cardiac muscle mitochondrion is packed with them. Thylakoids and grana belong to the chloroplast, which achieves the same end by a different geometry: stacked flattened sacs rather than folds.

Q: The space enclosed by the inner mitochondrial membrane is the

Correct answer: matrixThe matrix is the compartment inside the inner membrane, and it holds the enzymes of the citric acid cycle and of fatty acid oxidation, along with the mitochondrial DNA and its ribosomes. The intermembrane space lies between the two membranes and is where protons accumulate; the stroma and thylakoid lumen are the corresponding chloroplast compartments.

Q: Chemiosmosis, as proposed by Peter Mitchell, explains ATP synthesis as being driven by

Correct answer: a proton gradient across a membraneMitchell’s proposal was that the respiratory chain pumps protons out of the matrix, and that the electrochemical gradient so created - not any chemical intermediate - drives ATP synthesis as protons flow back through the ATP synthase. It was resisted for years because it required a *membrane* to be the coupling device rather than a molecule, and it earned the Nobel Prize in 1978.

The folds of the inner mitochondrial membrane are called

A.cristae
B.thylakoids
C.grana
D.lamellae

Answer: A

Correct answer: cristae

The cristae are the infoldings of the inner mitochondrial membrane, and their number and depth track how much oxidative work the cell does - a cardiac muscle mitochondrion is packed with them. Thylakoids and grana belong to the chloroplast, which achieves the same end by a different geometry: stacked flattened sacs rather than folds.

Discuss in Forum

The space enclosed by the inner mitochondrial membrane is the

A.thylakoid lumen
B.matrix
C.intermembrane space
D.stroma

Answer: B

Correct answer: matrix

The matrix is the compartment inside the inner membrane, and it holds the enzymes of the citric acid cycle and of fatty acid oxidation, along with the mitochondrial DNA and its ribosomes. The intermembrane space lies between the two membranes and is where protons accumulate; the stroma and thylakoid lumen are the corresponding chloroplast compartments.

Discuss in Forum

The citric acid cycle takes place in the

A.intermembrane space
B.cytosol of the cell
C.mitochondrial matrix
D.inner membrane itself

Answer: C

Its enzymes are dissolved in the matrix, whereas the electron transport chain is embedded in the inner membrane beside them. Glycolysis, by contrast, happens in the cytosol before pyruvate ever reaches the mitochondrion. The three stages are thus spread across two separate compartments.

Discuss in Forum

The electron transport chain of a mitochondrion is located in the

A.outer mitochondrial membrane
B.matrix alongside the cycle enzymes
C.cytosol surrounding the organelle
D.inner mitochondrial membrane

Answer: D

Embedding the carriers in a membrane is essential, because pumping protons across it is how the energy of the electrons is captured. A chain floating free in solution could store nothing. Compartmentation is therefore not incidental to respiration but essential to it.

Discuss in Forum

Assertion (A): The inner mitochondrial membrane is far more extensively folded than the outer one.
Reason (R): The inner membrane carries the electron transport chain and the ATP synthase.

A.Both A and R are true, and R is the correct explanation of A
B.Both A and R are true, but R is not the correct explanation of A
C.A is true but R is false
D.A is false but R is true

Answer: A

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the purpose. The rate of ATP production is limited by how much membrane is available to carry the respiratory complexes and the ATP synthase, so folding the inner membrane into cristae multiplies that area several times within the same volume. The outer membrane carries no such machinery and needs no such area.

Discuss in Forum

Chemiosmosis, as proposed by Peter Mitchell, explains ATP synthesis as being driven by

A.the mechanical rotation of the whole organelle
B.a proton gradient across a membrane
C.the direct transfer of phosphate from NADH
D.heat released by the oxidation of glucose

Answer: B

Correct answer: a proton gradient across a membrane

Mitchell’s proposal was that the respiratory chain pumps protons out of the matrix, and that the electrochemical gradient so created - not any chemical intermediate - drives ATP synthesis as protons flow back through the ATP synthase. It was resisted for years because it required a *membrane* to be the coupling device rather than a molecule, and it earned the Nobel Prize in 1978.

Discuss in Forum

Protons are pumped from the mitochondrial matrix into the

A.thylakoid lumen
B.nucleus of the cell
C.intermembrane space
D.cytosol directly

Answer: C

Accumulating there makes the intermembrane space acidic relative to the matrix, and the resulting gradient stores the energy. The narrowness of the space helps the concentration build quickly. A wider space would dilute the protons and weaken the gradient.

Discuss in Forum

State whether the following is true or false.
The proton gradient in a mitochondrion is highest across the outer membrane.

A.True only at large scales
B.False only at small scales
C.True
D.False

Answer: D

The outer membrane is freely permeable to small molecules and ions through porins, so no gradient can be maintained across it. The whole gradient sits across the inner membrane, which is where the pumps and the synthase are.

Discuss in Forum

ATP synthase produces ATP as protons

A.flow back down their gradient through it
B.are pumped outward against their gradient
C.combine chemically with phosphate ions
D.are converted into hydrogen molecules

Answer: A

The flow turns a rotor, and that mechanical rotation drives the chemistry at the catalytic head. It is one of the few molecular machines that genuinely rotates. Each full turn of the rotor yields three molecules of ATP.

Discuss in Forum

10.

If about 4 protons must pass through ATP synthase for each ATP made, how many protons are needed for 30 ATP?

A.7.5
B.120
C.34
D.60

Answer: B

Four protons per ATP over thirty molecules requires 120. The ratio is not a whole number in reality, which is one reason ATP yields per glucose are now quoted as approximate. Earlier textbook figures of 36 or 38 ATP per glucose were falsely precise.

Discuss in Forum

Loading…

Topics

Other Subjects

Tags: Mitochondria and Chloroplasts Questions and Answers || Mitochondria and Chloroplasts MCQ Questions and Answers || Mitochondria and Chloroplasts GK Questions and Answers || Mitochondria and Chloroplasts GK MCQ Questions || Mitochondria and Chloroplasts Multiple Choice Questions and Answers || Mitochondria and Chloroplasts GK || GK on Mitochondria and Chloroplasts || Cell Biology Questions and Answers || Cell Biology MCQ Questions and Answers || Cell Biology GK Questions and Answers || GK on Cell Biology

Mitochondria and Chloroplasts Questions and Answers

Topics

Other Subjects

About Us

Stay informed about all important Dates & Notifications