Cell Organelles: Mitochondria and Peroxisomes
48 Questions
3 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary component of the mitochondrial genome?

  • Linear DNA molecules
  • Circular DNA molecules (correct)
  • Chromosomal DNA
  • RNA molecules

How many proteins does the human mitochondrial genome encode that are involved in electron transport and oxidative phosphorylation?

  • 13 (correct)
  • 16
  • 8
  • 10

Which type of genes encode the proteins necessary for transcription and translation in mitochondria?

  • Plasmid genes
  • Nuclear genes (correct)
  • Mitochondrial genes
  • Cytoplasmic genes

What is the size of the human mitochondrial genome?

<p>16 Kb (D)</p> Signup and view all the answers

Where are mitoribosomal proteins (MRPs) synthesized?

<p>Cytosol (D)</p> Signup and view all the answers

What is the complete mitoribosome complex called?

<p>55S monosome (D)</p> Signup and view all the answers

Which mitochondrial structure interacts with the translocase OXA1L?

<p>Inner mitochondrial membrane (D)</p> Signup and view all the answers

What is primarily encoded by the mitochondrial genome apart from proteins?

<p>tRNA and rRNA (C)</p> Signup and view all the answers

What is the main goal of mitochondrial replacement techniques?

<p>To avoid transmission of mitochondrial diseases to offspring (A)</p> Signup and view all the answers

How many proteins are estimated to be encoded by the nuclear genome for mammalian mitochondria?

<p>1,500 (C)</p> Signup and view all the answers

What is the primary function of the Tom complex?

<p>To direct protein translocation across the outer membrane (C)</p> Signup and view all the answers

Which sequence is crucial for directing proteins to the mitochondrial matrix?

<p>Amino-terminal presequence (A)</p> Signup and view all the answers

What process converts glucose into pyruvate in animal cells?

<p>Glycolysis (C)</p> Signup and view all the answers

What role does the electrochemical potential play in mitochondrial protein import?

<p>It aids in the translocation of matrix proteins across the inner membrane. (C)</p> Signup and view all the answers

What is the primary role of the enzymes within the citric acid cycle?

<p>To oxidatively degrade carbohydrates and fatty acids (A)</p> Signup and view all the answers

Which process is NOT associated with mitochondrial replacement techniques?

<p>Cloning of mitochondrial DNA (C)</p> Signup and view all the answers

Which protein complex is responsible for transferring proteins to the inner membrane of mitochondria?

<p>Tim23 (C)</p> Signup and view all the answers

Which of the following statements about the inner mitochondrial membrane is true?

<p>It contains 70% proteins involved in oxidative phosphorylation. (D)</p> Signup and view all the answers

How is the energy used for ATP synthesis generated during oxidative phosphorylation?

<p>Through the proton gradient across the inner membrane (A)</p> Signup and view all the answers

Which of the following describes the structure of mammalian mitochondria?

<p>A double membrane system (D)</p> Signup and view all the answers

What is the fate of pyruvate after glycolysis?

<p>It is oxidized to acetyl CoA in the mitochondria. (B)</p> Signup and view all the answers

Which type of molecules can freely pass through the outer mitochondrial membrane?

<p>Small molecules and ions (B)</p> Signup and view all the answers

What type of relationship is believed to have led to the evolution of mitochondria?

<p>Symbiotic relationship (C)</p> Signup and view all the answers

Which statement correctly describes the fate of the high-energy electrons from NADH and FADH2?

<p>They are transferred to oxygen through transporters. (A)</p> Signup and view all the answers

What is the primary function of mitochondria in cells?

<p>Generate ATP from the breakdown of carbohydrates and fatty acids (C)</p> Signup and view all the answers

What unique feature do mitochondria possess that distinguishes them from peroxisomes?

<p>Capable of protein synthesis from their own DNA (C)</p> Signup and view all the answers

How are most mitochondrial proteins synthesized?

<p>On free ribosomes in the cytoplasm (D)</p> Signup and view all the answers

What structural feature increases the surface area of the inner mitochondrial membrane?

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

What is the role of enzymes contained within peroxisomes?

<p>Facilitate metabolic pathways such as fatty acid breakdown (C)</p> Signup and view all the answers

Which compartments of mitochondria are primarily involved in oxidative metabolism?

<p>Mitochondrial matrix and inner membrane (D)</p> Signup and view all the answers

What process describes the dynamic changes in mitochondria as they fuse and divide?

<p>Fusion and fission (D)</p> Signup and view all the answers

What type of genetic material is found within the mitochondrial matrix?

<p>Mitochondrial DNA coding for tRNA and rRNA (C)</p> Signup and view all the answers

What is the primary role of cardiolipin in the mitochondria?

<p>It enhances the efficiency of oxidative phosphorylation. (B)</p> Signup and view all the answers

Which statement about peroxisomes is correct?

<p>Human cells may contain between 100 and 1000 peroxisomes depending on activity. (B)</p> Signup and view all the answers

How are lipids transferred from the ER to the mitochondria?

<p>At close contact points mediated by phospholipid transfer proteins. (A)</p> Signup and view all the answers

What distinguishes the enzymes found in peroxisomes from those in mitochondria?

<p>Peroxisome enzymes resemble typical eukaryotic proteins. (B)</p> Signup and view all the answers

What is produced as a result of oxidative reactions in peroxisomes?

<p>Hydrogen peroxide. (D)</p> Signup and view all the answers

Which of the following is NOT a characteristic of peroxisomes?

<p>They generate energy through ATP synthesis. (B)</p> Signup and view all the answers

Cardiolipin is classified as which type of lipid?

<p>Double phospholipid. (C)</p> Signup and view all the answers

Which structure in the cell is responsible for the synthesis of phospholipids that may end up in the mitochondrial membranes?

<p>Endoplasmic reticulum (ER). (D)</p> Signup and view all the answers

What is the primary function of catalase in peroxisomes?

<p>To break down hydrogen peroxide (D)</p> Signup and view all the answers

Which two signals are used for the targeting of internal peroxisomal proteins?

<p>PTS1 and PTS2 (B)</p> Signup and view all the answers

Which of the following is NOT involved in the import of matrix proteins into peroxisomes?

<p>Pex19 (C)</p> Signup and view all the answers

What is a key function of plasmalogens formed in peroxisomes?

<p>Phospholipid synthesis for cell membranes (B)</p> Signup and view all the answers

How are most transmembrane proteins for peroxisomes synthesized?

<p>Synthesized in the ER (A)</p> Signup and view all the answers

Which peroxin is specifically involved in recognizing the PTS1 signal?

<p>Pex5 (B)</p> Signup and view all the answers

What is one of the mechanisms through which new peroxisomes can form?

<p>Budding from the ER (A)</p> Signup and view all the answers

Which of the following components are recognized by Pex19 during the import of peroxisomal membrane proteins?

<p>Peroxisomal targeting signal (mPTS) (A)</p> Signup and view all the answers

Flashcards

Oxidative Phosphorylation

The process of converting energy from the breakdown of carbohydrates and fatty acids into ATP.

Mitochondrial cristae

The inner membrane of the mitochondria folds inwards, creating the cristae which increase surface area for oxidative phosphorylation.

Mitochondrial matrix

The fluid-filled space within the inner membrane of the mitochondria.

Mitochondrial Fusion and Fission

The process where mitochondria fuse together and subsequently divide.

Signup and view all the flashcards

Mitochondrial protein import

The process of proteins synthesized by the cell's ribosomes being transported into the mitochondria.

Signup and view all the flashcards

Mitochondrial DNA

A circular DNA molecule within the mitochondria that carries genetic information for some of the organelle's proteins.

Signup and view all the flashcards

Mitochondrial Membranes

A double-membrane system surrounding the mitochondria, composed of two separate membranes with an intermembrane space in between.

Signup and view all the flashcards

Mitochondrial Diseases

Conditions caused by genetic mutations affecting mitochondrial function, resulting in various symptoms and health issues.

Signup and view all the flashcards

Glycolysis

The process where glucose is broken down into pyruvate. It takes place in the cytoplasm.

Signup and view all the flashcards

Citric Acid Cycle (Krebs Cycle)

The process where pyruvate is oxidized to CO2 in the mitochondria, generating ATP.

Signup and view all the flashcards

Electron Transport Chain

The transfer of electrons from NADH and FADH2 to oxygen, creating a proton gradient across the inner mitochondrial membrane.

Signup and view all the flashcards

Oxidative Metabolism

The main source of energy for animal cells, involving the breakdown of glucose and fatty acids.

Signup and view all the flashcards

Inner Mitochondrial Membrane

The inner membrane of the mitochondria, folded into cristae, containing proteins involved in oxidative phosphorylation and metabolite transport.

Signup and view all the flashcards

Outer Mitochondrial Membrane

The outer membrane of the mitochondria, permeable to small molecules due to porin proteins.

Signup and view all the flashcards

Endosymbiosis

Mitochondria are thought to originate from bacteria that lived inside larger cells.

Signup and view all the flashcards

Protein Import into Mitochondria

Proteins destined for the mitochondrial matrix must cross both the outer and inner mitochondrial membranes.

Signup and view all the flashcards

Tom Complex

The Tom complex on the outer mitochondrial membrane guides proteins into the mitochondria.

Signup and view all the flashcards

Tim23 Complex

The Tim23 complex on the inner mitochondrial membrane facilitates the movement of proteins into the matrix.

Signup and view all the flashcards

Electrochemical Potential in Mitochondrial Protein Import

The electrochemical potential across the inner mitochondrial membrane drives the transport of proteins into the matrix.

Signup and view all the flashcards

Transmembrane Proteins and the Tim23 Channel

Proteins containing transmembrane sequences insert into the inner mitochondrial membrane.

Signup and view all the flashcards

Leader Sequences for Mitochondrial Targeting

A leader sequence, typically at the amino terminus of a protein, guides it to specific mitochondrial compartments.

Signup and view all the flashcards

Presequences for Mitochondrial Targeting

These sequences are rich in positively charged amino acids and bind to the Tom complex.

Signup and view all the flashcards

Mitochondrial Protein Synthesis

Mammalian mitochondria contain approximately 1,500 proteins, with the majority encoded by the nuclear genome.

Signup and view all the flashcards

What is mtDNA?

Mitochondrial DNA, or mtDNA, is a circular molecule found in mitochondria, not in the cell's nucleus. It carries genes essential for mitochondrial function.

Signup and view all the flashcards

How much mtDNA is in each mitochondrion?

The number of mtDNA copies per mitochondrion varies significantly between species, and even within different tissues of the same organism.

Signup and view all the flashcards

Where are most mitochondrial proteins encoded?

While mtDNA encodes some proteins, the majority of mitochondrial proteins are encoded by nuclear genes. This suggests a transfer of genetic material from an ancestral mitochondira to the nucleus.

Signup and view all the flashcards

How does mtDNA size differ between species?

Mitochondrial DNA (mtDNA) is much smaller in humans and animals compared to plants and yeasts. However, the difference mainly arises from non-coding sequences in the larger genomes.

Signup and view all the flashcards

What is the main role of mtDNA encoded proteins?

mtDNA codes for 13 proteins directly involved in electron transport and oxidative phosphorylation, the energy production process in mitochondria.

Signup and view all the flashcards

How do mitochondria translate their own proteins?

Mitochondria have their own ribosomes and tRNAs to translate the proteins encoded by their own DNA.

Signup and view all the flashcards

What role do nuclear genes play in mitochondrial function?

Nuclear genes are responsible for producing proteins involved in transcription and translation inside the mitochondria. This includes enzymes, ribosomal proteins, and transcription factors.

Signup and view all the flashcards

What are mitoribosomes made of?

Mitoribosomes are made up of proteins (MRPs) synthesized in the cytosol and imported into mitochondria, and ribosomal RNA (rRNA) transcribed from mtDNA.

Signup and view all the flashcards

What are peroxisomes?

Peroxisomes are small organelles that contain enzymes involved in various metabolic reactions, including the breakdown of hydrogen peroxide (H2O2), oxidation of fatty acids, and synthesis of plasmalogens.

Signup and view all the flashcards

What is the role of catalase in peroxisomes?

Catalase is an enzyme found in peroxisomes that breaks down harmful hydrogen peroxide into water (H2O) and oxygen (O2).

Signup and view all the flashcards

What are plasmalogens and where are they important?

Plasmalogens are a type of phospholipid with an ether bond instead of an ester bond, found in membranes of tissues like the heart and brain.

Signup and view all the flashcards

How do proteins get into peroxisomes?

Peroxisomes import proteins from both free ribosomes and the endoplasmic reticulum (ER).

Signup and view all the flashcards

What is PTS1 and what is its role?

PTS1 is a signal sequence at the carboxyl terminus of some peroxisomal proteins, consisting of the amino acid sequence Ser-Lys-Leu.

Signup and view all the flashcards

How are the PTS1 and PTS2 signals recognized by peroxisomes?

Recognition of PTS1 and PTS2 signals by the peroxins Pex5 and Pex7, respectively, is crucial for the import of proteins into peroxisomes.

Signup and view all the flashcards

How are new peroxisomes formed?

Peroxisomes can form through budding from the ER or by division and growth.

Signup and view all the flashcards

What is the role of Pex19 in peroxisome membrane protein import?

Pex19 is a receptor protein involved in the import of some peroxisomal membrane proteins synthesized on free ribosomes.

Signup and view all the flashcards

What is cardiolipin?

A double phospholipid found in the inner mitochondrial membrane, which helps with oxidative phosphorylation and restricts proton flow.

Signup and view all the flashcards

How do lipids get from the ER to mitochondria?

A process involving the movement of lipids from the ER to mitochondria. This is done by proteins that carry individual lipid molecules through the cytosol.

Signup and view all the flashcards

What are some key features of peroxisomes?

They have their own specialized enzymes, are surrounded by a membrane, and do not have their own genome. All proteins are synthesized in the cytoplasm, with some coming from the ER.

Signup and view all the flashcards

What are some of the functions of peroxisomes?

They contain over 50 different enzymes involved in various metabolic reactions, including the production of Hydrogen peroxide.

Signup and view all the flashcards

Describe the structure of peroxisomes.

Peroxisomes are surrounded by a single membrane and are typically 0.1-1µm in diameter.

Signup and view all the flashcards

How are peroxisomes formed?

Peroxisomes can be replicated by division or generated by the cell from scratch.

Signup and view all the flashcards

What is the difference between mitochondrial and peroxisomal proteins?

While mitochondrial proteins often resemble those of prokaryotes, peroxisome proteins resemble typical eukaryotic proteins.

Signup and view all the flashcards

Study Notes

Mitochondria and Peroxisomes

  • Mitochondria are responsible for generating most of the cell's usable energy from the breakdown of lipids and carbohydrates.
  • Peroxisomes contain enzymes involved in various metabolic pathways, including fatty acid breakdown and photorespiration.
  • Proteins destined for mitochondria and peroxisomes are synthesized on free ribosomes in the cytosol, except for membrane proteins of the peroxisome.
  • Proteins import into target organelles, in the form of complete polypeptide chains.
  • Mitochondria contain their own genomes, which include genes transcribed and translated within the organelle itself.
  • Mitochondria are surrounded by a double membrane system, an inner and outer mitochondrial membrane separated by an intermembrane space
  • The inner membrane folds into numerous cristae, which extend into the mitochondrial matrix
  • The matrix and inner membrane are the primary functional compartments of mitochondria.
  • Mitochondria are dynamic and undergo fusion and fission.
  • The matrix contains mitochondrial genetic system and enzymes responsible for central reactions of oxidative metabolism.
  • The primary source of metabolic energy involves the breakdown of glucose and fatty acids.
  • The oxidation of acetyl CoA to CO2 is linked to the reduction of NAD+ and FAD to NADH and FADH2, respectively.
  • Most energy from oxidative metabolism is produced by oxidative phosphorylation in the inner mitochondrial membrane.
  • High-energy electrons from NADH and FADH2 are transferred to oxygen via membrane transporters.
  • The energy from electron transfer is converted into a proton gradient used to synthesize ATP.
  • The inner mitochondrial membrane has high protein content, is involved in oxidative phosphorylation, and maintains a critical proton gradient.
  • Outer membrane is completely permeable to small molecules via porins, which allow passage of molecules smaller than 1000 daltons.
  • The composition of the intermembrane space is similar to that of the cytosol.

Genetic System of Mitochondria

  • Mitochondria evolved from bacteria.
  • Mitochondrial genome forms a circular DNA molecule and several copies per organelle.
  • Size of the mitochondrial genome varies between different species.
  • Mitochondrial DNA encodes essential components for oxidative phosphorylation (tRNA, rRNA, some proteins).
  • Other mitochondrial proteins are encoded by nuclear genes and transferred from ancestral mitochondrial genomes.
  • Human mitochondrial genome is only 16 kb, while yeast and plants have larger genomes
  • Human mitochondrial genome codes for 13 proteins, 16S and 12S ribosomal RNA, and 22 transfer RNAs.
  • Nuclear genes provide the rest of the proteins required for mitochondrial functions.

Mitochondrial Diseases

  • Mitochondrial DNA mutations, primarily transmitted through the maternal line, are often harmful to the organelle.
  • Mitochondrial inheritance means defects in mtDNA are inherited from the mother.
  • Homoplasmy means the multiple copies of mitochondrial DNA in the cell are identical, while heteroplasmy means a combination of wild-type and mutated mitochondrial DNA.

Mitochondrial Protein Internalization and Formation

  • Mammalian mitochondria contain about 1,500 proteins encoded by nuclear genome.
  • Nuclear-encoded proteins are synthesized by free ribosomes in the cytoplasm and transported into mitochondria.
  • Protein import is complex due to the double membrane of mitochondria.
  • Proteins with amino terminal pre-sequences are the most studied.
  • These pre-sequences bind to the Tom complex on the outer membrane for initial translocation.
  • Mitochondrial matrix proteins cross the inner membrane via the Tim23-complex, utilizing the electrochemical gradient.
  • Other proteins utilizing a transmembrane sequence laterally insert into the inner membrane via other transport mechanisms.
  • Matrix proteases remove pre-sequences.
  • Protein import through complex pathways in the matrix and inner membrane, necessitating chaperones

Peroxisomes

  • Peroxisomes are small organelles (0.1-1 µm) with a membrane.
  • Human cells have a variable number (100-1000) depending on activity.
  • Peroxisomes lack a genome and utilize ribosomes in the cytoplasm for protein synthesis, while some proteins from the ER.
  • Peroxisome function includes various metabolic reactions and protein synthesis.
  • Peroxisomes are responsible for oxidation reactions that produce hydrogen peroxide.
  • Catalase, a key peroxisomal enzyme, breaks down hydrogen peroxide.
  • Peroxisomes oxidize branched and longer-chain fatty acids, along with other substrates.
  • Peroxisomes participate in plasmalogen synthesis (important membrane component of heart and brain).

Peroxisome Assembly

  • Internal peroxisomal proteins synthesize in the cytosol, while the bulk of transmembrane proteins are synthesized in the ER.
  • Transmembrane proteins (peroxins, Pex proteins) are important for metabolite transport.
  • PTS1 (Ser-Lys-Leu) signal, is widely used for proteins targeting peroxisomes.
  • PTS2 (amino-terminal sequences of 9 aa) is another targeting designation.
  • Peroxins (Pex5, Pex7, etc), as cytosolic receptors, bind to PTS1/PTS2 to initiate import to the peroxisome.
  • The Pex complex anchors proteins to peroxisome membrane and helps them enter.

Lipid Transfer and Lipids in Peroxisomes

  • Lipid transfer between ER and mitochondria happens at contact points and requires phospholipid transfer proteins to extract phospholipid molecules from ER and introduce them to the mitochondria.
  • Lipids can then transport via an aqueous environment.
  • Lipids move between the inner and outer mitochondrial membranes at contact points.
  • The majority of lipids in the mitochondrial membranes originate from the cytosol and undergo synthesis in the ER.
  • Phosphatidylethanolamine is produced from phosphatidylserine.
  • Cardiolipin, a four fatty acid chain phospholipid, is synthesized in the inner membrane and enhances oxidative phosphorylation.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Unit 6: Mitochondria and Peroxisomes PDF

Description

This quiz covers the key functions and characteristics of mitochondria and peroxisomes within cells. You'll explore their roles in energy production, metabolism, and protein synthesis. Perfect for anyone studying cell biology or biochemistry!

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser