Rider Biology 1.8: Mitochondria & Cellular Respiration
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What is a mitochondrion?
A double-membraned organelle that converts energy from carbohydrate fuels into ATP.
Why are mitochondria called the power plants of the cell?
They convert energy from food molecules into ATP that can power cell activities.
What molecule do mitochondria produce for cell energy?
ATP.
What does ATP stand for?
Adenosine triphosphate.
Which cells tend to have many mitochondria?
Cells with high energy needs, such as muscle cells.
How many mitochondria can a cell contain?
Hundreds or even thousands.
How many membranes does a mitochondrion have?
Two.
What are the two mitochondrial membranes called?
Outer membrane and inner membrane.
What is special about the mitochondrial inner membrane?
It is highly folded.
What are the folds of the inner mitochondrial membrane called?
Cristae.
Why are cristae important?
They increase the surface area available for ATP-producing proteins.
What is the mitochondrial matrix?
The innermost fluid-filled region of the mitochondrion.
What is found in the mitochondrial matrix?
Enzymes, mitochondrial DNA, ribosomes, and other components.
What is a mitochondrial nucleoid?
The region containing mitochondrial DNA.
What shape is mitochondrial DNA?
Circular.
Do mitochondria have their own ribosomes?
Yes.
What do mitochondrial ribosomes do?
They help make some mitochondrial proteins.
What are mitochondrial storage granules?
Granules that store some nutrients inside mitochondria.
What does the endosymbiotic theory suggest about mitochondria?
Mitochondria evolved from ancient bacteria that lived inside larger host cells.
What evidence supports the bacterial origin of mitochondria?
They have two membranes, circular DNA, ribosomes, bacterial-like shape, and reproduce by division.
Are mitochondria surrounded by a cell wall?
No.
Why might mitochondria have lost their ancestral cell wall?
To make exchange of nutrients and ATP with the host cell easier.
What is the overall job of cellular respiration?
To transfer energy from fuel molecules into ATP.
What is the first major stage of cellular respiration?
Glycolysis.
Where does glycolysis occur?
In the cytosol outside the mitochondrion.
What does glycolysis do to glucose?
It splits one glucose molecule into two smaller pyruvate molecules.
How many carbon atoms are in glucose?
Six.
How many carbon atoms are in each pyruvate?
Three.
What does Rider mean by “glycolysis”?
Sugar splitting.
What molecule is the starting fuel for glycolysis?
Glucose.
What molecule is produced from glucose during glycolysis?
Pyruvate.
How many pyruvate molecules are produced from one glucose?
Two.
How much ATP does Rider's figure show being made during glycolysis?
2 ATP.
What other energy carrier does glycolysis produce?
NADH.
Where does pyruvate go after glycolysis?
Into the mitochondrion.
Where is pyruvate further broken down?
In the mitochondrial matrix.
What major cycle occurs in the matrix after pyruvate enters the mitochondrion?
The citric acid cycle.
What is another common name for the citric acid cycle?
Krebs cycle.
What gas is released during breakdown in the matrix?
Carbon dioxide, CO₂.
What important energy carriers are produced during the citric acid cycle?
NADH and FADH₂.
How much ATP does Rider's figure show from the citric acid cycle?
About 2 ATP.
What is the third major stage of cellular respiration?
Oxidative phosphorylation.
Where does oxidative phosphorylation occur?
On the inner mitochondrial membrane.
What is the role of the electron transport chain?
It transfers electrons and uses their energy to pump H⁺ ions across the inner membrane.
What happens to H⁺ ions during electron transport?
They are pumped to one side of the inner mitochondrial membrane, creating a gradient.
What is a proton gradient?
A difference in H⁺ concentration across a membrane.
Why is the proton gradient important?
It stores potential energy used to make ATP.
What protein uses the proton gradient to make ATP?
ATP synthase.
What happens when H⁺ flows through ATP synthase?
ATP synthase uses that flow to make ATP.
What is the simple ATP-making sequence in mitochondria?
Electron transport → H⁺ gradient → ATP synthase → ATP.
What is the final electron acceptor in mitochondrial respiration?
Oxygen.
What happens to oxygen at the end of oxidative phosphorylation?
It combines with hydrogen-related components to form water.
What molecule is formed from oxygen during the final stage of respiration?
Water, H₂O.
Why is oxygen important in aerobic cellular respiration?
It serves as the final electron acceptor and allows the electron transport process to continue.
What does oxidative phosphorylation produce?
A large amount of ATP.
How much ATP does Rider's Figure 20 show being made by ATP synthase?
About 28 ATP.
Which stage of respiration produces the most ATP?
Oxidative phosphorylation.
What is the overall order of the three major stages of cellular respiration?
Glycolysis → citric acid cycle → oxidative phosphorylation.
Where does glycolysis occur?
Cytosol.
Where does the citric acid cycle occur?
Mitochondrial matrix.
Where does oxidative phosphorylation occur?
Inner mitochondrial membrane.
What is the key function of NADH?
To carry high-energy electrons to the electron transport chain.
What is the key function of FADH₂?
To carry high-energy electrons to the electron transport chain.
What is the relationship between NADH and ATP production?
NADH delivers high-energy electrons whose energy helps create the H⁺ gradient used to make ATP.
What is the relationship between FADH₂ and ATP production?
FADH₂ also provides high-energy electrons to the electron transport chain.
Why does the inner mitochondrial membrane have many folds?
More folds provide more surface area for electron transport proteins and ATP synthase.
What would happen if the inner mitochondrial membrane had less surface area?
The mitochondrion would have less space for ATP-producing machinery.
What is the purpose of ATP synthase?
To make ATP using energy from H⁺ flow.
What powers ATP synthase?
The movement of H⁺ ions down their concentration gradient.
What is the difference between glycolysis and oxidative phosphorylation?
Glycolysis splits glucose in the cytosol, while oxidative phosphorylation uses the inner membrane and proton gradient to make most ATP.
What is the difference between the matrix and the inner membrane?
The matrix is the internal fluid region; the inner membrane contains electron transport proteins and ATP synthase.
What is the difference between cristae and the matrix?
Cristae are folds of the inner membrane; the matrix is the fluid inside the inner membrane.
What is the connection between glucose and ATP?
Energy stored in glucose is gradually transferred into ATP during cellular respiration.
What is the connection between pyruvate and the citric acid cycle?
Pyruvate enters the mitochondrion and is processed before its carbon is further oxidized in the citric acid cycle.
What is the connection between the citric acid cycle and oxidative phosphorylation?
The citric acid cycle produces NADH and FADH₂, which deliver electrons to the electron transport chain.
What is the connection between electron transport and ATP synthase?
Electron transport creates the H⁺ gradient that ATP synthase uses to make ATP.
What is the connection between oxygen and water formation?
Oxygen accepts electrons at the end of the electron transport chain and helps form water.
Why do muscle cells have many mitochondria?
They need large amounts of ATP for contraction and other activities.
Can plant cells contain mitochondria?
Yes.
Do plant cells use mitochondria for cellular respiration?
Yes.
What is the relationship between chloroplasts and mitochondria in plant cells?
Chloroplasts make carbohydrate fuel, and mitochondria use that fuel to make ATP.
What is the main fuel role of glucose in respiration?
It stores chemical energy that can be transferred into ATP.
A cell has a very high energy demand. What organelle would you expect to be abundant?
Mitochondria.
A scientist observes many folds in a mitochondrial inner membrane. What is the benefit?
More surface area for ATP-producing proteins.
A cell cannot use oxygen. Which mitochondrial process would be most directly disrupted?
Oxidative phosphorylation.
A mitochondrion cannot maintain an H⁺ gradient. What process would be impaired?
ATP production by ATP synthase.
A mitochondrion has damaged ATP synthase. What major product would decrease?
ATP.
A mitochondrion has damaged electron transport proteins. What would happen to the proton gradient?
It would be reduced or fail to form properly.
A student says glycolysis happens inside the mitochondrial matrix. Is that correct?
No. Glycolysis occurs in the cytosol.
A student says the citric acid cycle occurs on the inner membrane. Is that correct?
No. It occurs mainly in the mitochondrial matrix.
A student says oxidative phosphorylation happens in the cytosol. Is that correct?
No. It occurs on the inner mitochondrial membrane.
A student says oxygen is the starting fuel for glycolysis. Is that correct?
No. Glucose is the starting fuel for glycolysis.
A student says cristae increase mitochondrial inner-membrane surface area. Is that correct?
Yes.
A student says mitochondria have their own circular DNA. Is that correct?
Yes.
A student says mitochondria make all of their own proteins. Is that correct?
No. Many mitochondrial proteins are encoded by genes in the cell nucleus and transported into mitochondria.
A student says ATP synthase acts like a turbine powered by H⁺ flow. Is that a useful analogy?
Yes.
A student says oxygen is converted directly into ATP. Is that correct?
No. Oxygen serves as the final electron acceptor and helps form water; the proton gradient powers ATP synthase.
What should you identify in Figure 19(a)?
Outer membrane, inner membrane, cristae, matrix, nucleoid, ribosomes, and storage granules.
What is the main idea of Figure 19(b)?
Mitochondria contain their own circular DNA genome.
What is the main idea of Figure 20?
It shows the major stages of cellular respiration and where ATP is produced.