Biology 5.3 Cell Biology: Ribosomes and Endomembrane System

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Questions and Answers

What is the total size of a fully assembled prokaryotic ribosome?

70s (correct)

50s

60s

80s

What primary function does the endomembrane system serve in cells?

Cell division

Energy production

Modification and transport of proteins (correct)

DNA replication

Which subunits combine to form the eukaryotic ribosome?

40s and 70s

30s and 60s

40s and 60s (correct)

50s and 80s

What is a unique feature of prokaryotic cells concerning ribosome activity?

Translation occurs in the cytosol near the ribosomes Signup and view all the answers

Which components are involved in the endomembrane system?

Nuclear envelope, lysosomes, and endoplasmic reticulum Signup and view all the answers

Which of the following statements is incorrect about prokaryotic cells?

Prokaryotic cells have a nucleus. Signup and view all the answers

How do membranes within the endomembrane system relate to each other?

They come into direct contact or are connected via vesicles. Signup and view all the answers

Which organelle is NOT a part of the endomembrane system?

Mitochondria Signup and view all the answers

Where are proteins that are to be incorporated into the plasma membrane synthesized?

In the rough endoplasmic reticulum Signup and view all the answers

What happens to proteins destined to be secreted from the cell during synthesis?

They are deposited into the RER lumen Signup and view all the answers

What role do hydrolytic enzymes in the lysosome serve?

To degrade various biomolecules Signup and view all the answers

What is the pH level maintained within lysosomes?

Acidic (pH around 5.5) Signup and view all the answers

How are lysosomes formed in the cell?

By budding from the trans face of the Golgi apparatus Signup and view all the answers

What process do molecules undergo to enter the cell and potentially reach lysosomes?

Endocytosis Signup and view all the answers

What happens to proteins embedded in vesicle membranes after vesicle fusion with the plasma membrane?

They become part of the plasma membrane Signup and view all the answers

What is the primary function of lysosomes in the cell?

Digestion of food particles and organic matter Signup and view all the answers

What is the primary function of cilia in eukaryotic cells?

Movement of substances away from the lungs Signup and view all the answers

Which motor protein is primarily responsible for muscle contractions?

Myosin Signup and view all the answers

What differentiates flagella from cilia in terms of their arrangement and movement?

Flagella have a whip-like undulating motion, whereas cilia have a back-and-forth motion. Signup and view all the answers

Which role do microtubules play in eukaryotic cells?

Facilitating intracellular transport of organelles Signup and view all the answers

What is one function of the cytoskeleton concerning organelles?

Helps anchor organelles to specific cellular compartments Signup and view all the answers

During fertilization, which feature of sperm cells is primarily responsible for their movement?

Flagella Signup and view all the answers

Which of the following statements is correct regarding cellular extensions in eukaryotic cells?

Cilia are typically involved in moving substances across the cell surface, while flagella enable movement. Signup and view all the answers

What is a fundamental difference in the structure of cilia and flagella?

Cilia have a specific arrangement of microtubules, making them shorter but more numerous. Signup and view all the answers

What determines the number of mitochondria in a cell?

The cell's metabolic needs Signup and view all the answers

What is the primary function of the cristae in mitochondria?

To increase the surface area for chemical reactions Signup and view all the answers

What supports the endosymbiotic theory regarding mitochondria?

Mitochondrial DNA is circular and similar to prokaryotic DNA Signup and view all the answers

Which of the following correctly describes the intermembrane space in mitochondria?

The space between the outer and inner membranes Signup and view all the answers

Which type of cells are likely to contain more mitochondria due to their higher metabolic activity?

Muscle cells Signup and view all the answers

What is the primary composition of the mitochondrial matrix?

Enzymes, DNA, and ribosomes Signup and view all the answers

Why are mitochondria considered to have a symbiotic origin?

They reproduce through binary fission like bacteria Signup and view all the answers

Which component of mitochondria is primarily involved in ATP production?

Cristae of the inner membrane Signup and view all the answers

What structural arrangement of microtubules characterizes eukaryotic cilia and flagella?

9+2 arrangement Signup and view all the answers

Which part of the cell anchors cilia and flagella?

Basal body Signup and view all the answers

What is a significant difference between prokaryotic and eukaryotic flagella?

Eukaryotic flagella contain microtubules. Signup and view all the answers

Which of the following best describes the main function of cilia and flagella?

Cellular motion Signup and view all the answers

What type of cellular structure do cilia and flagella share in their composition?

Microtubules Signup and view all the answers

How are the microtubules organized within the structure of cilia and flagella?

In a ring-like structure Signup and view all the answers

Which of the following best distinguishes prokaryotic flagella from eukaryotic flagella?

Eukaryotic flagella have a 9+2 arrangement. Signup and view all the answers

What additional structure is associated with the microtubules found in eukaryotic cilia and flagella?

Basal body Signup and view all the answers

What is the primary function of nuclear pores in eukaryotic cells?

They regulate the passage of materials in and out of the nucleus. Signup and view all the answers

What must happen for a protein to be translocated into the nucleus?

It must be recognized by the nuclear localization sequence. Signup and view all the answers

Which component forms the nuclear pore complex (NPC)?

Nucleoporins Signup and view all the answers

How are the chromosomes organized within the nucleus?

They are organized into discrete structures called chromosomes. Signup and view all the answers

What limits the size and type of molecules that can pass through nuclear pores?

The size of the nuclear pores themselves Signup and view all the answers

What is one primary function of peroxisomes in eukaryotic cells?

Facilitation and containment of oxidative reactions Signup and view all the answers

How do peroxisomes differ from mitochondria regarding genetic material?

Mitochondria contain DNA, while peroxisomes do not Signup and view all the answers

What is produced during oxidative reactions in peroxisomes that requires detoxification?

Reactive oxygen species (ROS) Signup and view all the answers

What process allows mitochondria to reproduce independently?

Binary fission Signup and view all the answers

Which enzyme found in peroxisomes helps to neutralize harmful effects of ROS?

Catalase Signup and view all the answers

What is the primary role of nucleoli within eukaryotic cells?

Synthesizing and assembling ribosomal RNA Signup and view all the answers

Which component is NOT part of a fully assembled ribosome?

Pre-rRNA precursors Signup and view all the answers

Where do ribosomal proteins combine with pre-rRNA?

In the nucleolus Signup and view all the answers

What initiates the translocation of ribosomes to the rough endoplasmic reticulum during protein synthesis?

Signal recognition particle recognition of signal peptide Signup and view all the answers

What is the composition of ribosomes in both prokaryotic and eukaryotic cells?

Ribosomal RNA and proteins Signup and view all the answers

Study Notes

Prokaryotic Ribosomes

30s and 50s ribosomal subunits combine to form a 70s ribosome
Prokaryotes do not have a nucleus, nucleolus, or membrane-bound organelles
mRNA is transcribed in the cytoplasm and translated by ribosomes in the cytosol

Eukaryotic Ribosomes

40s and 60s ribosomal subunits assemble to form an 80s ribosome

The Endomembrane System

A collection of membranous organelles involved in various tasks within a cell
Includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and the plasma membrane
Plays a role in protein modification, transport, carbohydrate and lipid metabolism, and detoxification
Membranes are connected by direct contact or transfer of membranous sacs called vesicles

The Rough Endoplasmic Reticulum (RER)

Site for protein synthesis and modification
Proteins destined for the plasma membrane are embedded in the RER membrane during synthesis
Proteins destined for secretion are deposited in the RER lumen

The Golgi Apparatus

Further modifies proteins from the RER
Packages proteins in vesicles for exocytosis

Lysosomes

Specialized vesicles that act as the cell's digestive system
Maintain an acidic environment with hydrolytic enzymes for degrading biomolecules
Involved in digestion of food particles, organic matter, and engulfed organisms during endocytosis
Formed from the Golgi apparatus via budding from the trans face

Mitochondria

Enclosed by an outer membrane and inner membrane
Inner membrane has convolutions called cristae, increasing surface area
Space bounded by the inner membrane is the mitochondrial matrix
Matrix contains enzymes for cellular respiration, mitochondrial DNA, and ribosomes
Region between the outer and inner membranes is the intermembrane space

Endosymbiotic Theory

Mitochondria are thought to have originated from a symbiotic relationship between an engulfed bacterium and a primitive eukaryotic host cell
Engulfed bacterium, an aerobic prokaryote, evolved into the mitochondrion
Supported by similarities between mitochondrial ribosomes and prokaryotic ribosomes, and mitochondrial DNA and prokaryotic DNA

Microtubules

Involved in cellular shape, cellular locomotion, anchoring organelles, and mitotic chromosome movement
Motor proteins include kinesin, dynein, and myosin

Cilia and Flagella

Microtubule-based cellular extensions
Cilia: Short, numerous, back-and-forth movement; function in moving substances
Flagella: Longer, few per cell, whip-like undulating motion; function in locomotion
Both contain a 9+2 arrangement of microtubules and are anchored to cells by a basal body

Extracellular Matrix (ECM)

Composed of substances secreted by cells
Performs various functions outside the cell
Examples include collagen, elastin, and proteoglycans
Provides structural support, cell adhesion, and communication

Cell Junctions

Specialized structures that connect cells, allowing for communication and coordination
Types include tight junctions, desmosomes, and gap junctions
Tight junctions: Prevent leakage of substances between cells
Desmosomes: Anchoring junctions, provide strong adhesion
Gap junctions: Communication junctions, allow passage of small molecules between cells

Eukaryotic Organelles

Eukaryotic cells are larger and more complex than prokaryotic cells.
Eukaryotic cells contain membrane-bound organelles, while prokaryotic cells do not.
The nucleus is the largest eukaryotic organelle and stores most of the cell's DNA, where DNA replication and transcription occur.
The nuclear envelope is a double membrane that surrounds the nucleus and is continuous with the endoplasmic reticulum.
Within the nucleus, DNA is organized into chromosomes, which are compacted into chromatin.
Nuclear pores regulate the passage of materials between the nucleus and cytoplasm.
The nuclear pore complex (NPC) is made up of proteins called nucleoporins and allows the transport of large molecules like ribosomal subunits and proteins.
Proteins targeted to the nucleus contain a nuclear localization sequence that facilitates their transport.
Ribosomes are essential for protein synthesis and are found in both eukaryotic and prokaryotic cells.
Ribosomes are composed of rRNA and proteins and are not membrane-bound organelles.
Nucleoli are sites of ribosomal synthesis and assembly.
Ribosomal RNA (rRNA) is transcribed from ribosomal DNA (rDNA) in the nucleolus.
Ribosomal proteins are synthesized in the cytoplasm and transported into the nucleolus for ribosome assembly.
Mature ribosomal subunits are transported out of the nucleus through nuclear pores.
The endoplasmic reticulum (ER) is a network of interconnected membranes that extends throughout the cytoplasm.
The ER is involved in protein synthesis, lipid metabolism, and detoxification.
The rough endoplasmic reticulum (RER) is studded with ribosomes, while the smooth endoplasmic reticulum (SER) lacks ribosomes.
The Golgi apparatus is a stack of flattened membranous sacs called cisternae.
It modifies, sorts, and packages proteins and lipids from the ER.
The Golgi apparatus is involved in the synthesis of lysosomes.
Lysosomes are membrane-bound organelles that contain digestive enzymes.
They break down worn-out organelles, cellular debris, and ingested material.
Mitochondria are the powerhouses of the cell and are responsible for ATP production through cellular respiration.
Mitochondria have their own DNA and ribosomes.
They grow and reproduce independently through mitochondrial fission.
Peroxisomes are small, membrane-bound organelles that carry out various metabolic reactions.
They contain oxidative enzymes and are involved in fatty acid metabolism, lipid biosynthesis, and detoxification.
Peroxisomes contain catalase, an enzyme that neutralizes reactive oxygen species (ROS).
While peroxisomes are not considered part of the endomembrane system, they are able to grow and replicate in a similar fashion to mitochondria.

The Extracellular Matrix (ECM)

Animal cells synthesize an extracellular matrix (ECM) that is composed mainly of proteins, many of which are glycoproteins.
The ECM participates in cell attachment, communication, growth, migration, mechanical stability, and tissue repair.
Collagen is the most abundant ECM protein, forming a strong network of fibers outside the cell.
The ECM interacts with the cell's cytoskeleton through integrin proteins.

Cell-Cell Junctions

Desmosomes provide tensile strength by anchoring intermediate filaments between neighboring cells.
Gap junctions mediate communication between cells.
Tight junctions form a seal between cells, preventing leakage of fluids.

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Description

Explore key concepts in cell biology focusing on prokaryotic and eukaryotic ribosomes, as well as the endomembrane system. Understand how ribosomal subunits assemble and the functions of various organelles involved in protein synthesis and metabolism. This quiz covers essential components that are crucial for cellular functions.