Mitochondria: Structure and Function
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Questions and Answers

What is the main function of mitochondria?

  • Synthesis of proteins
  • Storage of genetic material
  • Detoxification of substances
  • Oxidation of organic compounds (correct)

Mitochondria are the site of glycolysis.

False (B)

Which statement about mitochondria is true?

  • Mitochondria are present in all eukaryotes. (correct)
  • Mitochondria are found in prokaryotes.
  • Mitochondria are transmitted from both parents.
  • Mitochondria are uniformly sized across all cell types.

Name the two series of biochemical reactions involved in glucose oxidation.

<p>Glycolysis and Krebs cycle</p> Signup and view all the answers

Mitochondrial proteins are synthesized by free ribosomes and delivered to the mitochondrion __________.

<p>post-translationally</p> Signup and view all the answers

Mitochondria only contain proteins encoded by the nucleus.

<p>False (B)</p> Signup and view all the answers

Which type of fatty acid oxidation occurs in the mitochondria?

<p>β-oxidation (C)</p> Signup and view all the answers

Match the following mitochondrial functions with their respective processes:

<p>Glycolysis = Occurs in the cytosol Krebs cycle = Takes place in the mitochondrial matrix Fatty acid oxidation = Also occurs in peroxisomes Protein import = Involves a targeting sequence</p> Signup and view all the answers

The inner mitochondrial membrane contains high levels of __________.

<p>cardiolipin</p> Signup and view all the answers

Match the parts of the mitochondrion with their descriptions:

<p>Outer Mitochondrial Membrane = Composed of 50% proteins Inner Mitochondrial Membrane = Thicker with cristae Mitochondrial Matrix = Gel-like consistency with high protein concentration Intermembrane Space = Contains enzymes and protons</p> Signup and view all the answers

Mitochondria play a role in the synthesis of non-essential amino acids.

<p>True (A)</p> Signup and view all the answers

What type of enzymes do the mitochondrial matrix contain?

<p>Enzymes for oxidation of organic compounds, Krebs cycle, and β-oxidation</p> Signup and view all the answers

What is the primary method by which mitochondria proliferate?

<p>Fission of pre-existing mitochondria (B)</p> Signup and view all the answers

Mitochondria are completely devoid of cholesterol.

<p>True (A)</p> Signup and view all the answers

What shape are most mitochondria?

<p>Ovoid</p> Signup and view all the answers

Flashcards

Mitochondria: Energy Powerhouses

Mitochondria are the powerhouses of the cell, extracting energy from organic compounds and storing it in the form of a proton gradient across their inner membrane.

Mitochondrial Function: Oxidation

Mitochondria break down organic compounds like carbohydrates and fatty acids to produce energy through a series of oxidation reactions.

Krebs Cycle: Breaking Down Glucose

The Krebs cycle is a series of chemical reactions that occur within the mitochondrial matrix, breaking down glucose and producing energy carriers like NADH and FADH2.

Beta-Oxidation: Breaking Down Fats

Beta-oxidation is a metabolic process where fatty acids are broken down into smaller units, generating energy in the form of ATP.

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Mitochondrial Roles: Synthesis

Mitochondria are involved in the synthesis of steroid hormones, phospholipids, and lipoprotein particles, often in collaboration with the endoplasmic reticulum (SER).

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Mitochondrial Storage: Ion and Organic Compound Bank

Mitochondria store various substances, including ions like calcium, sodium, and potassium, as well as organic compounds like lipoproteins.

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Protein Import: Post-Translational Delivery

Proteins destined for the mitochondria are synthesized by free ribosomes in the cytoplasm and then transported to the mitochondrion after translation.

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Mitochondrial Targeting Sequence: The Address Code

Mitochondria have a specific signal sequence, called a presequence or targeting sequence, near the N-terminus of proteins targeted for the organelle. This sequence guides the protein to the correct location.

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What are mitochondria?

Mitochondria are essential organelles present in all eukaryotic cells, but absent in prokaryotes. They are involved in crucial cellular processes such as energy production through aerobic respiration and the oxidation of organic compounds.

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What are the key features of mitochondria?

Mitochondria, although primarily inherited maternally, have a small contribution from the father's DNA. Their shape can vary, and they tend to be concentrated in areas of high metabolic activity.

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Describe the structure of the mitochondrial membranes.

The outer mitochondrial membrane (OMM) is composed of 50% proteins, while the inner one (IMM) contains over 75%. The IMM is thicker and has greater surface area as it forms inward folds known as cristae.

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What is the intermembrane space?

The intermembrane space, located between the two mitochondrial membranes, is rich in enzymes like cytochrome c and protons. It plays a key role in cellular respiration.

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What are some features of the inner mitochondrial membrane?

The IMM (inner mitochondrial membrane) lacks cholesterol and has a high concentration of cardiolipin, a unique phospholipid crucial for its function.

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What is the mitochondrial matrix?

The mitochondrial matrix is a gel-like substance containing a high concentration of proteins and other organic and inorganic molecules. This is where many important metabolic processes occur.

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What is the central function of mitochondria?

Mitochondria are essential for the production of ATP, the main energy currency of the cell, through a process called oxidative phosphorylation. This process involves the breakdown of organic compounds to release energy.

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How do prokaryotes carry out energy production without mitochondria?

Although prokaryotes lack mitochondria, they still carry out oxidation of organic compounds and cell respiration by enzymes in their cytoplasm and plasma membrane. This is similar to the function of mitochondria.

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Study Notes

Mitochondria: General Description

  • Mitochondria are large enough to be seen by light microscopy, but their internal structure is only visible with electron microscopy
  • Found in all eukaryotes, but not in prokaryotes
  • In humans, mitochondria are solely inherited maternally, as only the nucleus from the sperm enters the egg
  • Mitochondria contain proteins encoded by both maternal and paternal alleles
  • Mitochondrial structure, number per cell, and intracellular location vary greatly between organisms and even between different tissues of the same organism. These characteristics also vary within a single cell type based on the physiological state of the cell
  • Certain microorganisms only have one mitochondrion, while others can have hundreds or thousands, concentrated in areas of high metabolic activity (e.g., epithelial intestine cells, muscle fibers)
  • Mitochondrial number can increase or decrease, being higher in actively dividing or moving cells

Mitochondrial Structure

  • Typically ovoid, ranging in size from 1-4 µm in length and 0.2-1 µm in diameter. However, filamentous mitochondria or tubular structures, interconnected networks or spiral formations also occur
  • Bounded by two membranes (inner and outer) separated by an intermembrane space
  • Inner membrane folds into cristae, increasing surface area
  • The inner membrane contains proteins involved in the electron transport chain and ATP synthesis
  • The matrix contains enzymes for the Krebs cycle, oxidation of organic compounds, and mitochondrial DNA

Mitochondrial Functions

  • Oxidation and Respiration: Mitochondria oxidize organic compounds to produce ATP through aerobic cell respiration
  • Carbohydrate Oxidation: Glucose is oxidized through glycolysis and the Krebs cycle
  • Fatty Acid Oxidation: Fatty acids are oxidized to generate acetyl-CoA, which then enters the Krebs cycle
  • Other Functions: Mitochondria cooperate with smooth endoplasmic reticulum in steroid hormone synthesis. They also synthesize certain phospholipids and non-essential amino acids. They can also store various substances within inclusions.

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Description

Explore the fascinating world of mitochondria, the powerhouses of eukaryotic cells. This quiz covers their structure, inheritance, and variability across different organisms and cell types. Test your knowledge on the essential role mitochondria play in cellular metabolism.

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