Genetic Disorders & Cell Organelles
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Questions and Answers

What primary function is disrupted in Zellweger Syndrome due to peroxisome biogenesis defects?

  • Protein synthesis
  • Oxidative reactions (correct)
  • ATP generation
  • DNA replication

Which organelle is responsible for generating ATP through cellular respiration?

  • Mitochondria (correct)
  • Endoplasmic Reticulum
  • Nucleus
  • Peroxisomes

What is the process called that forms peroxisomes from existing structures?

  • Biogenesis (correct)
  • Mitosis
  • Apoptosis
  • Endocytosis

In which cellular structure do developmental issues arise due to Zellweger Syndrome?

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

What role does the nucleus primarily serve within the cell?

<p>Storing genetic material and coordinating activities (C)</p> Signup and view all the answers

What type of reactions do peroxisomes primarily conduct?

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

Which cellular process is directly affected by the malfunction of peroxisomes?

<p>Fatty acid metabolism (B)</p> Signup and view all the answers

What is the location of ATP generation in a cell?

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

What is the primary role of the KDEL sequence in protein sorting?

<p>Maintains soluble ER-resident proteins in the ER (A)</p> Signup and view all the answers

Which pathway involves the degradation of cellular components via autophagy?

<p>Lysosomal degradation pathways (D)</p> Signup and view all the answers

What initiates the process of N-Glycosylation in proteins?

<p>The endoplasmic reticulum (ER) (B)</p> Signup and view all the answers

What is the main purpose of the KKXX motif within the context of protein sorting?

<p>To retain membrane proteins in the ER (C)</p> Signup and view all the answers

Which of the following statements regarding membrane protein orientation is true?

<p>Orientation established in the ER is conserved throughout transport (B)</p> Signup and view all the answers

What is the primary role of H⁺ pumps in the context of acidic environment maintenance?

<p>To actively pump protons into the lumen (D)</p> Signup and view all the answers

Lysosomal enzymes are tagged with which molecule in the Golgi for recognition by M6P receptors?

<p>Mannose-6-phosphate (M6P) (D)</p> Signup and view all the answers

Which process specifically involves the internalization of small cytoplasmic portions?

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

What is the function of constitutive secretion in protein transport?

<p>Transports proteins without signals to the cell surface (A)</p> Signup and view all the answers

During lysosome biogenesis, what happens to endosomes?

<p>They are transformed into lysosomes. (A)</p> Signup and view all the answers

In the context of protein sorting, what does endocytosis primarily involve?

<p>Internalization of smaller particles (D)</p> Signup and view all the answers

What is the primary function of peroxisomal targeting signals (PTS)?

<p>To direct proteins to peroxisomes (A)</p> Signup and view all the answers

What type of secretion pathway is involved in the transport of specific secretory proteins?

<p>Regulated secretion pathway (C)</p> Signup and view all the answers

Which sugars are commonly involved in the modification of glycoproteins during N-Glycosylation?

<p>N-acetylglucosamine, galactose, and sialic acid (C)</p> Signup and view all the answers

Which statement about PTS1 and PTS2 is accurate?

<p>Both PTS1 and PTS2 direct proteins to the same cellular compartment. (C)</p> Signup and view all the answers

Which mechanism serves to digest cellular components in a recycling fashion?

<p>Lysosomal degradation pathways (B)</p> Signup and view all the answers

What characterizes the cis side of the Golgi apparatus?

<p>It is the side that receives vesicles from the ER. (C)</p> Signup and view all the answers

What is the primary function of M6P receptors in the trans-Golgi network (TGN)?

<p>To bind and package proteins for lysosome delivery (A)</p> Signup and view all the answers

What process involves the engulfing of large particles by cells?

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

What is the role of oxidases within peroxisomes?

<p>They produce hydrogen peroxide during oxidation reactions. (A)</p> Signup and view all the answers

Which function does catalase serve in peroxisomes?

<p>It prevents oxidative damage by breaking down hydrogen peroxide. (D)</p> Signup and view all the answers

What does the trans side of the Golgi apparatus primarily do?

<p>It sends proteins and lipids to their final destinations. (D)</p> Signup and view all the answers

Which of the following statements about peroxisomal structure is false?

<p>Peroxisomes have a uniform structure without compartments. (D)</p> Signup and view all the answers

What type of reactions are primarily catalyzed by enzymes located in peroxisomes?

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

What primary function is associated with the Medial Golgi?

<p>Modification and processing of proteins (B)</p> Signup and view all the answers

Which process involves the addition of carbohydrate chains to proteins?

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

Which of the following best describes the Trans-Golgi Network (TGN)?

<p>Final stage of protein sorting and packaging (B)</p> Signup and view all the answers

What is the primary detoxification role of the Golgi apparatus?

<p>Converts H₂O₂ into water and oxygen (A)</p> Signup and view all the answers

Which steroid molecules are produced in the Golgi apparatus?

<p>Cholesterol and bile acids (A)</p> Signup and view all the answers

What environmental condition do the acid hydrolases in the Golgi apparatus require for optimal functionality?

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

What main role does the Golgi apparatus play in protein structural modification?

<p>Further glycosylations and modifications (A)</p> Signup and view all the answers

Which of the following is NOT a function of the Golgi apparatus?

<p>Synthesis of ribosomal RNA (A)</p> Signup and view all the answers

What is the primary role of the Golgi apparatus in relation to lysosomes?

<p>It modifies proteins and adds specific tags for lysosome targeting. (A)</p> Signup and view all the answers

What distinguishes primary lysosomes from secondary lysosomes?

<p>Primary lysosomes are formed from the Golgi apparatus, while secondary lysosomes form from fusions with vesicles. (A)</p> Signup and view all the answers

What particular tag is important for directing lysosomal proteins to their proper destination?

<p>Mannose-6-phosphate (B)</p> Signup and view all the answers

What are residual bodies in the context of lysosomes?

<p>They consist of undigested materials that may be rejected from the cell. (B)</p> Signup and view all the answers

What is a key function of secondary lysosomes?

<p>They digest materials after fusing with primary lysosomes. (D)</p> Signup and view all the answers

How do primary lysosomes contribute to membrane recycling in a cell?

<p>They recycle or create membranes as needed. (D)</p> Signup and view all the answers

What happens to proteins that lack mannose-6-phosphate tags?

<p>They may be sent to the cytoplasm instead of lysosomes. (D)</p> Signup and view all the answers

What is a false statement about lysosomal proteins?

<p>Lysosomal proteins always contain mannose-6-phosphate tags. (C)</p> Signup and view all the answers

Flashcards

Peroxisomal Targeting Signals (PTS)

Short amino acid sequences that act like 'zip codes' guiding proteins to peroxisomes.

PTS1

A C-terminal PTS (at the end of the protein) that signals to peroxisomes.

PTS2

An N-terminal PTS (at the beginning of the protein) that signals to peroxisomes.

Peroxisomes

Membrane-bound sacs within a cell that contain enzymes for oxidation reactions.

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Cis side of the Golgi

The side of the Golgi apparatus facing the endoplasmic reticulum (ER)

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Trans side of the Golgi

The side of the Golgi apparatus facing the plasma membrane.

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Oxidases

Enzymes that produce hydrogen peroxide (H₂O₂) during their reactions.

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Catalase

An enzyme that breaks down hydrogen peroxide (H₂O₂), preventing oxidative damage.

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Medial Golgi

The portion of the Golgi apparatus responsible for further processing and modifying proteins, including glycosylation.

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Glycosylation

A process where carbohydrate chains are added to proteins, enhancing their stability and function.

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Trans-Golgi Network (TGN)

The final stage of the Golgi apparatus where proteins are sorted and packaged into various vesicles for transport.

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Detoxification

The Golgi apparatus plays a crucial role in detoxifying cells by converting harmful hydrogen peroxide into water and oxygen.

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Biosynthesis

The Golgi apparatus is involved in producing essential molecules like cholesterol and bile acids.

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Spherical Vesicles

A specialized compartment within the Golgi apparatus containing acid hydrolases that function optimally at acidic pH.

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Acid Hydrolases

Enzymes that break down molecules using water.

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Golgi Apparatus

A stack of flattened sacs that are interconnected and function as a site of protein processing and sorting.

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Peroxisome Biogenesis

The process by which peroxisomes are formed, either from pre-existing peroxisomes or from vesicles derived from the endoplasmic reticulum.

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Nucleus

The central organelle of a cell, containing the genetic material (DNA) that controls cellular activities.

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Mitochondria

Powerhouse of the cell, responsible for generating energy (ATP) through cellular respiration.

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Zellweger Syndrome

A genetic disorder caused by defects in peroxisome biogenesis, leading to severe developmental issues and often early death.

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Catabolism

The process of breaking down large molecules into smaller ones, often with the release of energy.

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Anabolism

The process of building up larger molecules from smaller ones, usually requiring energy.

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Protein Synthesis

The process of synthesizing proteins from amino acids, based on the genetic instructions in DNA.

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Golgi Apparatus: Modification and Sorting

Part of the Golgi apparatus responsible for adding sugars to proteins, modifying them, and directing them to their correct destinations.

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Primary Lysosome

A type of lysosome that contains digestive enzymes and can fuse with vesicles to break down material.

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Secondary Lysosome

A type of lysosome that forms when a primary lysosome fuses with a vesicle containing material to be digested.

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Residual Body

A type of lysosome that contains undigested material. It may be expelled from the cell or remain inside.

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Mannose-6-phosphate (M6P) Tag

A tag attached to lysosomal proteins in the cis-Golgi network. It directs these proteins to lysosomes.

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Lysosome Formation

The process by which the Golgi apparatus generates new lysosomes and recycles or creates membranes as needed.

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Primary Lysosome

A type of lysosome formed by the Golgi apparatus. They are filled with digestive enzymes but do not yet contain substrates.

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Secondary Lysosome

When a primary lysosome fuses with a vesicle containing material for digestion, it becomes a secondary lysosome.

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Autophagy

The process by which cells break down their own components, like damaged organelles, for recycling or energy.

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Endocytosis

The process where cells engulf and internalize smaller particles from the extracellular space for processing.

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Constitutive Secretion Pathway

The default pathway for transporting proteins from the endoplasmic reticulum (ER) to the cell surface. Proteins without specific signals use this pathway.

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KDEL Sequence

A specific amino acid sequence that acts like a 'zip code' directing soluble proteins to the endoplasmic reticulum (ER).

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KKXX Motif

Specific amino acid sequences found in transmembrane proteins that keep them anchored within the endoplasmic reticulum (ER).

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ER Retention Signals

These are the first steps where proteins are folded and modified within the cell. They create the foundation for further processing in the Golgi apparatus.

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Vesicular Transport

The process where proteins are packaged into vesicles and transported from the ER to the Golgi apparatus, and eventually to their final destinations.

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Membrane Protein Orientation

The orientation of a protein within a membrane, such as the ER membrane or the plasma membrane, is maintained throughout its journey within the cell.

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Acidic Environment Maintenance in Lysosomes

A key feature of lysosomes, their acidic environment is maintained by proton pumps that actively pump hydrogen ions (H+) into the lumen, keeping the pH low.

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N-Glycosylation of Membrane and Secreted Proteins

Proteins destined for the cell membrane or to be secreted outside the cell are further modified during N-glycosylation, by adding sugars like N-acetylglucosamine, galactose, and sialic acid.

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M6P Tagging of Lysosomal Enzymes

Lysosomal enzymes are tagged with mannose-6-phosphate (M6P) in the Golgi apparatus, acting like a 'zip code' for lysosomes.

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M6P Receptor Role in Lysosome Targeting

M6P receptors located in the trans-Golgi network (TGN) recognize and bind to M6P-tagged lysosomal enzymes, packaging them for delivery to the lysosome.

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Transport to Lysosome

Lysosomal proteins are transported in vesicles that bud off from the TGN and fuse with endosomes. These endosomes then mature into lysosomes.

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Lysosome Biogenesis and Function

Lysosomes are formed through a process called lysosomal biogenesis. They function as the cell's recycling center, breaking down waste materials, cellular debris, and worn-out organelles.

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Regulated Secretion Pathway

A specific pathway for releasing proteins from the cell that requires a signal to trigger the release. This is in contrast to the constitutive pathway, where proteins are continuously released.

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Study Notes

  • X-linked Adrenoleukodystrophy: Mutation in ABCD1 gene causes fatty acid buildup, harming brain and adrenal glands.
  • Zellweger Syndrome: Defect in peroxisome biogenesis, severe developmental issues, often fatal early in life.

Peroxisomes: Structure and Enzymatic Functions

  • Structure: Membrane-bound organelles with enzymes for oxidation reactions.
  • Oxidases: Produce hydrogen peroxide during substrate oxidation.
  • Catalase: Breaks down hydrogen peroxide, preventing oxidative damage.
  • Detoxification: Converts hydrogen peroxide to water and oxygen.
  • Biosynthesis: Produces essential molecules like cholesterol and bile acids.

Lysosome Structure and Function

  • Structure: Spherical vesicles containing acid hydrolases, optimal function at acidic pH.
  • Primary Lysosomes: Contain enzymes, no substrates.
  • Secondary Lysosomes: Formed when primary lysosomes fuse with vesicles holding materials for digestion.
  • Residual Bodies: Contain undigested materials, may be expelled or remain in the cell.
  • Acidic Environment Maintenance: Proton pumps maintain low pH.
  • Transport to Lysosome: Lysosomal enzymes tagged with M6P in Golgi, transported to lysosomes.
  • Lysosomal Degradation Pathways: Phagocytosis (engulfing large particles), Endocytosis (internalizing smaller particles), Autophagy (digesting cellular components), and Microautophagy (engulfing small portions directly).

Golgi Apparatus Structure and Function

  • Structure: Membrane-bound cisternae (compartments) organized into a stack.
  • Polarity: Cis side (receiving, closer to ER) and Trans side (sending, closer to plasma membrane).
  • Compartments: Cis-Golgi Network (CGN), Medial Golgi, Trans-Golgi Network (TGN).
  • Functions: Modifies, sorts, and packages proteins for destinations.
  • Protein Modification and Sorting: Glycosylation (carbohydrate addition), Protein processing (further modifications), Membrane/lysosome formation (generation of lysosomes).
  • N-Glycosylation: Initiation in ER and continued in Golgi.
  • TGN Sorting Mechanisms: Lysosomal Proteins (M6P tags), Membrane/Secreted Proteins.
  • Regulated Secretion Pathway: Specific signals direct proteins to secretory vesicles.
  • Constitutive Secretion Pathway: Proteins without signals are transported to the cell surface by default.

ER Retention Signals

  • KDEL Sequence: Retains soluble ER-resident proteins within the ER.
  • KKXX Motif: Retains ER transmembrane proteins within the ER.
  • Retrieval Mechanism: Proteins escaping to the Golgi are retrieved via CGN receptors recognizing these signals, returning them to the ER.

Membrane Protein Orientation

  • Orientation established in ER, conserved in vesicular transport. This includes the orientation of glycoproteins.

Intracellular Compartments and Protein Sorting

  • Proteins destined for different organelles are sorted by signals or receptors.
  • Key organelles include ER, Golgi Apparatus, Lysosomes, and Peroxisomes.
  • Proteins are tagged or modified to specify their destination.

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Description

This quiz explores genetic disorders related to peroxisomes, such as X-linked Adrenoleukodystrophy and Zellweger Syndrome. Additionally, it covers the structure and functions of peroxisomes and lysosomes, highlighting their enzymatic roles and importance in cellular processes. Test your understanding of these critical cellular components and their associated disorders.

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