Cell Biology: Intracellular Compartments Quiz

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Questions and Answers

What happens to LDL after it is internalized by the cell?

It is directly transported to the nucleus.

It is stored in the cytoplasm for later use.

It remains bound to the receptors on the cell surface.

It is degraded in lysosomes to release free cholesterol. (correct)

How does LDL dissociate from its receptors?

In the acidic environment of the endosome. (correct)

By direct contact with the cell membrane.

When exposed to oxygen in the mitochondria.

In the neutral pH of the cytoplasm.

What is the primary fate of LDL receptors after they dissociate from LDL?

They are transported back to the plasma membrane. (correct)

They are converted into free cholesterol.

They are degraded in lysosomes.

They undergo endocytosis again immediately.

How often does an LDL receptor make a round trip into the cell and back?

Every 10 minutes. Signup and view all the answers

During its lifespan, how long does an LDL receptor typically remain functional before being recycled?

20 hours. Signup and view all the answers

What directs ribosomes in the cytosol to the ER?

An ER signal sequence recognized by a signal-recognition particle Signup and view all the answers

Which type of proteins pass completely into the ER lumen?

Soluble proteins destined for secretion or organelles Signup and view all the answers

What initiates the translocation process of ribosomes into the ER membrane?

Binding of the ribosome-SRP complex to an SRP receptor on the ER Signup and view all the answers

What is the primary function of transport vesicles?

To carry proteins and membranes between cell compartments Signup and view all the answers

Which pathway describes the transport of synthesized proteins to the plasma membrane?

Outward secretory pathway Signup and view all the answers

Where do extracellular molecules ingested by the cell go first?

To early endosomes Signup and view all the answers

What remains anchored in the lipid bilayer during the translocation process?

Transmembrane proteins Signup and view all the answers

What does vesicular transport within the endomembrane system rely on?

Highly organized pathways between membrane-enclosed compartments Signup and view all the answers

What is one of the primary functions of membrane-enclosed organelles in eukaryotic cells?

To segregate different metabolic processes Signup and view all the answers

Which organelle is considered the most prominent in eukaryotic cells?

Nucleus Signup and view all the answers

How do eukaryotic cells communicate between their internal membranes and the cytosol?

Using nuclear pores Signup and view all the answers

What major site is primarily responsible for the synthesis of new membranes in eukaryotic cells?

Endoplasmic reticulum Signup and view all the answers

What is one consequence of mixing the contents of eukaryotic cells in a test tube?

Chemical chaos occurs and proteins degrade Signup and view all the answers

Which of the following describes the arrangement of reactions in eukaryotic cells?

Reactions are segregated into different membrane-enclosed compartments Signup and view all the answers

Which of the following is NOT a strategy used by cells to organize metabolic processes?

Storing excess proteins in the cytoplasm Signup and view all the answers

What typically arises if the contents of liver cells are mixed in vitro?

Quick degradation of enzymes and proteins Signup and view all the answers

What determines the fate of receptor proteins involved in endocytosis?

Type of receptor involved Signup and view all the answers

Which of the following pathways lead materials to the lysosome?

Autophagy Signup and view all the answers

What is formed when an organelle is enclosed by a double membrane during autophagy?

Autophagosome Signup and view all the answers

What type of endocytic pathway results in receptor recycling to the same plasma membrane?

Recycling Signup and view all the answers

Which component of the lysosome contributes to the degradation process?

Hydrogen ions and a H+ pump Signup and view all the answers

What is the role of the signal sequence in mitochondrial protein import?

To translocate the protein across the membranes Signup and view all the answers

What distinguishes membrane-bound ribosomes from free ribosomes?

Membrane-bound ribosomes synthesize proteins to be translocated into the ER Signup and view all the answers

How does the Signal-Recognition Particle (SRP) affect protein synthesis?

It binds to the signal sequence and slows protein synthesis Signup and view all the answers

What is one of the primary functions of chaperone proteins in mitochondrial import?

To assist in pulling proteins across membranes and refolding them Signup and view all the answers

Which of the following statements about the endoplasmic reticulum (ER) is accurate?

The ER contains a common pool of ribosomes for synthesizing proteins Signup and view all the answers

What happens to ribosomal subunits after a round of protein synthesis?

They are released and rejoin the common pool in the cytosol Signup and view all the answers

What characterizes the structure of the endoplasmic reticulum in eukaryotic cells?

It forms a complex network of tubes Signup and view all the answers

Which feature is specific to rough endoplasmic reticulum?

It contains ribosomes that synthesize proteins Signup and view all the answers

Study Notes

Intracellular Compartments and Protein Transport

Eukaryotic cells segregate different metabolic processes within different membrane-enclosed compartments.
This allows for more efficient and organized chemical reactions within the cell.
Membrane-enclosed compartments are called organelles.

Organelles

The nucleus is the most prominent organelle, containing the cell's genetic material.
The endoplasmic reticulum (ER) is the site of new membrane synthesis.
The Golgi apparatus processes and distributes proteins synthesized in the ER.
Lysosomes are involved in the breakdown of macromolecules.
Mitochondria are the powerhouses of the cell, responsible for ATP production.
Peroxisomes contain enzymes that break down fatty acids and other molecules.

Protein Transport

Proteins destined for the ER, Golgi apparatus, lysosomes, or secretion are synthesized on ribosomes attached to the ER membrane.
Proteins contain an ER signal sequence that directs them to the ER.
The signal-recognition particle (SRP) binds to the signal sequence and the ribosome, slowing protein synthesis.
The SRP-ribosome complex binds to an SRP receptor on the ER membrane.
The ribosome docks with a protein translocator in the ER membrane.
The protein is translocated across the ER membrane.
The signal sequence is cleaved off by a signal peptidase inside the ER lumen.

Vesicular Transport

Transport vesicles carry soluble proteins and membranes between cell compartments.
The secretory pathway transports newly synthesized proteins from the ER to the Golgi apparatus, plasma membrane, and lysosomes.
The endocytic pathway brings extracellular molecules into the cell by engulfing them in vesicles derived from the plasma membrane.
These vesicles fuse with endosomes and eventually lysosomes for degradation.

Receptor-Mediated Endocytosis

LDL (low-density lipoprotein) binds to LDL receptors on the cell surface.
The LDL-receptor complex is internalized in clathrin-coated vesicles.
The vesicles lose their coat and fuse with endosomes.
The LDL dissociates from its receptor in the acidic environment of the endosome.
LDL is degraded in lysosomes, releasing free cholesterol.
LDL receptors are recycled back to the plasma membrane.

Lysosomes

Lysosomes contain hydrolytic enzymes that degrade macromolecules.
They maintain an acidic pH, optimal for the activity of their enzymes.

Autophagy

Autophagy is the process of degrading obsolete parts of the cell itself.
An organelle is enclosed by a double membrane, forming an autophagosome.
The autophagosome fuses with a lysosome, and the contents are degraded.

Summary

Eukaryotic cells have developed a system of membrane-enclosed organelles to compartmentalize different metabolic processes.
Proteins destined for different organelles are synthesized on ribosomes attached to the ER membrane.
Vesicular transport carries proteins and membranes between cell compartments.
Receptor-mediated endocytosis is a mechanism by which cells take up specific molecules from the extracellular environment.
Lysosomes are responsible for the degradation of macromolecules and cellular components through autophagy.

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Description

Test your knowledge on eukaryotic cells and their organelles. This quiz covers various cell compartments, their functions, and the process of protein transport within these organelles. Perfect for biology students aiming to understand cellular organization.