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Questions and Answers
What is one primary function of the TCA cycle within the mitochondria?
What is one primary function of the TCA cycle within the mitochondria?
Which of the following components is NOT part of human mitochondrial DNA?
Which of the following components is NOT part of human mitochondrial DNA?
What is the role of the ATPase in mitochondria?
What is the role of the ATPase in mitochondria?
In mitochondrial membranes, what is the primary difference between the outer mitochondrial membrane (OMM) and the inner mitochondrial membrane (IMM)?
In mitochondrial membranes, what is the primary difference between the outer mitochondrial membrane (OMM) and the inner mitochondrial membrane (IMM)?
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Which of the following processes does NOT occur in the mitochondrial matrix?
Which of the following processes does NOT occur in the mitochondrial matrix?
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The endosymbiotic theory suggests that mitochondria originated from which type of organism?
The endosymbiotic theory suggests that mitochondria originated from which type of organism?
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Which molecule is primarily produced by the electron transport chain in mitochondria?
Which molecule is primarily produced by the electron transport chain in mitochondria?
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What is the main chemical process by which high-energy electrons contribute to an electrochemical gradient?
What is the main chemical process by which high-energy electrons contribute to an electrochemical gradient?
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Study Notes
Overview of Mitochondria
- Mitochondria are responsible for energy generation in eukaryotic cells
- They have two membranes: outer and inner
- The inner membrane has folds called cristae, increasing surface area for reactions
Mitochondrial Structure
-
Outer Membrane (OMM):
- Permeable to small molecules
- Contains porin proteins for transport
- Involved in communication with other organelles (e.g., ER, endosomes)
- Participates in apoptosis & mitophagy
-
Inner Membrane (IMM):
- Impermeable to most molecules
- Contains proteins for the electron transport chain
- Folds into cristae to increase surface area
- Contains ATP synthase
- Rich in proteins involved in the respiratory chain
-
Intermembrane Space:
- The space between the OMM and IMM
- Contains enzymes & molecules involved in mitochondrial functions
-
Matrix:
- The space enclosed by the IMM
- Contains enzymes for the citric acid cycle and fatty acid oxidation
- Contains mitochondrial DNA (mtDNA)
Mitochondrial Origins
- Mitochondria originated from an endosymbiotic event
- They have their own DNA (mtDNA)
- Human mtDNA encodes 13 respiratory chain proteins, large and small ribosomal units, and tRNA
Mitochondrial Function
-
ATP Production:
- Electron transport chain (ETC) transfers electrons to oxygen
- The energy released pumps protons across the inner membrane
- The proton gradient drives ATP synthesis by ATP synthase
-
Other Reactions:
- Citric acid cycle (TCA cycle) for energy production
- Fatty acid oxidation
- Amino acid synthesis
- Urea cycle
Mitochondrial Trafficking
- Mitochondria are moved along microtubules via motor proteins (kinesin and dynein)
- Miro and Milton proteins link mitochondria to microtubules
Mitochondrial Contact Sites
- Mitochondria interact with other organelles, including the endoplasmic reticulum (ER)
- These contact sites facilitate communication and exchange of molecules
- They are critical for calcium signaling and lipid exchange
Inner Mitochondrial Membrane (IMM)
- Site of energy generation (ATP production)
- Rich in proteins involved in the respiratory chain
- Structure optimized for restricted diffusion and localization of reactions
- Contains transporters for substrates (e.g., ATP, acetyl-CoA)
Electron Transport Chain
- Transfers high-energy electrons from donors to oxygen
- Couples electron transfer to proton pumping across the inner membrane
ATP Synthase
- Utilizes the H+ gradient to synthesize ATP
- Contains a water-soluble head (F₁) and a transmembrane domain (F₀)
ATP/ADP Translocase
- Transports ADP into and ATP out of the mitochondrial matrix
- Stoichiometric exchange (1 ADP for 1 ATP)
- Conformational change driven by ATP binding
Cristae
- Folds in the inner mitochondrial membrane for increased surface area
MICOS
- Mitochondrial contact site and cristae organizing system
- ATPase dimerization to drive membrane curvature
- Involved in membrane invagination and shaping
Why Complex Mitochondrial Structure?
- Increased surface area for enzyme localization (e.g., electron transport chain)
- Efficient substrate transport
- Compartmentalization of reactions for optimized conditions (pH gradients)
Summary Notes
- Location and transport of mitochondria within the cell
- Structure and origins of mitochondria
- Compartments/Membranes of the mitochondria, and their function
- Next week will cover chemiosmotic coupling, electron transport chain, and ATPase
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Description
Explore the vital role of mitochondria in energy generation and cellular functions. This quiz covers their unique structure, including the outer and inner membranes, cristae, and the intermembrane space. Test your knowledge on the components and functions that make mitochondria essential to eukaryotic cells.
