Protein Sorting I: Eukaryotic Organelles
18 Questions
0 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

Which of the following organelles is NOT involved in the endomembrane system?

  • Nuclear envelope
  • Endoplasmic reticulum (ER)
  • Mitochondria (correct)
  • Lysosomes

All nuclear-encoded proteins are synthesized in the nucleus.

False (B)

What role do signal sequences play in protein sorting?

They direct proteins to their correct location within the cell.

Proteins that lack a signal sequence are typically __________.

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

Match the signal sequence to its corresponding characteristic:

<p>N-terminus rich in hydrophobic aa = Promotes import into mitochondria C-terminus with KDEL = Targets protein back to the ER Amphipathic helix with basic aa = Directs import into peroxisomes Alternating hydrophobic aa = Facilitates import into chloroplasts</p> Signup and view all the answers

What sequence signals the import of soluble proteins into peroxisomes?

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

The SKL signal sequence on soluble proteins is cleaved off within the peroxisome.

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

Where is catalase likely located in cells that do not contain peroxisomes?

<p>In the cytosol</p> Signup and view all the answers

In normal cells, catalase shows up as small dots of fluorescence due to its localization in __________.

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

Match the following cellular components with their respective functions:

<p>Peroxisomes = Breakdown of fatty acids and detoxification Nucleus = Storage of genetic information Endoplasmic Reticulum = Synthesis of proteins and lipids Cytosol = Site of metabolic pathways</p> Signup and view all the answers

What is the role of the TOM complex in mitochondria?

<p>To translocate proteins across the outer membrane (D)</p> Signup and view all the answers

TIM23 and TOM complexes can work together to create a translocation channel across both mitochondrial membranes.

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

What is the function of catalase in peroxisomes?

<p>To recycle hydrogen peroxide into water and oxygen</p> Signup and view all the answers

Mitochondrial proteins are imported through the TOM and TIM complexes, which require _____ for active transport.

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

Match the following mitochondria-related complexes with their functions:

<p>TOM = Translocates proteins across the outer membrane TIM = Translocates proteins across the inner membrane TIM22 = Imports multi-pass membrane proteins SAM = Inserts porins into the outer membrane</p> Signup and view all the answers

What would happen if you changed the charged amino acids in a mitochondrial signal sequence to acidic amino acids?

<p>The protein would be unable to enter the mitochondria. (C)</p> Signup and view all the answers

Peroxisomes are involved in the production of cholesterol and long-chain fatty acids.

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

What type of reactions do peroxisomes carry out using O2?

<p>Oxidation reactions</p> Signup and view all the answers

Flashcards

Protein Sorting

The process of delivering proteins to their appropriate destinations within a eukaryotic cell.

Signal Sequence

A specific amino acid sequence within a protein that acts as a "postal code" to direct the protein to its target organelle.

Protein Import Mechanism

Organelles use one of three mechanisms to import proteins: active transport, facilitated diffusion, and endocytosis/exocytosis.

Signal Sequences in Proteins

Signal sequences in proteins determine their final location within the cell.

Signup and view all the flashcards

Protein Import into Nucleus

Nuclear-encoded proteins are synthesized in the cytoplasm and then imported into the nucleus using specific signals.

Signup and view all the flashcards

Mitochondrial protein import

Proteins enter mitochondria using TOM and TIM complexes, requiring energy.

Signup and view all the flashcards

TOM complex

The outer mitochondrial membrane translocator.

Signup and view all the flashcards

TIM complex

The inner mitochondrial membrane translocator.

Signup and view all the flashcards

Peroxisomes

Organelles using oxygen to produce hydrogen peroxide.

Signup and view all the flashcards

Catalase

An enzyme that recycles hydrogen peroxide, creating water and oxygen.

Signup and view all the flashcards

Protein import into mitochondria

The active transport of proteins into mitochondria.

Signup and view all the flashcards

Protein destination in the mitochondria

Proteins can be targeted for the matrix, inner membrane, outer membrane, or intermembrane space.

Signup and view all the flashcards

Peroxisome Import: Folded or Unfolded?

Proteins are imported into peroxisomes in their folded state, unlike mitochondrial import where proteins are unfolded.

Signup and view all the flashcards

Peroxisome Import Receptor: SKL and Cargo

The import receptor recognizes the SKL signal sequence at the C-terminus of soluble proteins destined for peroxisomes. This sequence is not cleaved off after import.

Signup and view all the flashcards

Peroxisome Import: Receptor Recycling

The peroxisome import receptor is ubiquitinated after delivering its cargo. This allows its return to the cytosol to pick up more cargo.

Signup and view all the flashcards

Peroxisome Import: Energy-Dependence

Peroxisome import requires ATP hydrolysis by a complex in the peroxisome membrane, similar to mitochondrial import.

Signup and view all the flashcards

Catalase Location in Peroxisome-Deficient Cells

In cells lacking peroxisomes, catalase, an enzyme normally found in peroxisomes, is likely to be found in the cytosol.

Signup and view all the flashcards

Study Notes

Protein Sorting I: Nucleus, Mitochondria, and Peroxisomes

  • Eukaryotic cells contain many membrane-bound compartments
  • These compartments include the nucleus, mitochondria, chloroplasts (plants), endoplasmic reticulum (ER), Golgi apparatus, endosomes, lysosomes, and peroxisomes
  • Organelles occupy about half the volume of a eukaryotic cell
  • Different organelles contain different proteins and specialized functions
  • The cytosol is the fluid component that occupies the majority in the cell. Other membrane-bound organelles are excluded.

Protein Transport Mechanisms

  • Organelles import proteins using one of three mechanisms
    • Transport through nuclear pores
    • Transport across membranes
    • Transport by vesicles

Protein Sorting in Eukaryotic Cells

  • Proteins are synthesized in the cytosol
  • Signal sequences direct proteins to the right location or organelle—like a postal code
  • Proteins lacking signal sequences remain in the cytosol (or are degraded) or enter the nucleus.
  • Different compartments have specific signal sequences
  • The import process can be either co-translational or post-translational
  • Nuclear localization signals (NLS) direct cargo into the nucleus
  • Nuclear import receptors bind the cargo NLS and nuclear pores. Ran GTP/GDP regulates the cycle. Ran GTP binding causes the release of cargo.
  • Nuclear export utilizes similar mechanisms as nuclear import, but in reverse, using nuclear export signals (NES)

Protein Import into Mitochondria

  • Mitochondrial precursor proteins are unfolded during import
  • A signal peptide at the N Terminus directs the protein to the mitochondria.
  • Import occurs via different complexes (TOM & TIM) in the outer and inner membranes
  • Energy (ATP) is required to import proteins

Protein Import into Peroxisomes

  • Soluble proteins are imported in a folded state through a specific receptor that recognizes C-terminal signals (SKL)
  • The receptor shuttles cargo into peroxisomes
  • The import signals are not cleaved from the protein during the process.
  • Return of the receptor to the cytosol necessitates ATP hydrolysis

Studying That Suits You

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

Quiz Team

Related Documents

Protein Sorting Lecture 13 PDF

Description

This quiz covers the organization and transport mechanisms of proteins within eukaryotic cells, including the nucleus, mitochondria, and peroxisomes. You'll learn about the various membrane-bound compartments and how proteins reach their designated organelles through different transport methods. Test your knowledge on protein sorting and cellular compartmentalization!

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser