Biology Chapter on Cell Organelles

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Questions and Answers

What is the primary function of the nucleolus?

DNA replication

Translation of mRNA into proteins

Packaging of proteins into vesicles

Production of ribosomal RNA (rRNA) (correct)

Which of the following is NOT a component of the endomembrane system?

Rough endoplasmic reticulum

Lysosomes

Mitochondria (correct)

Golgi apparatus

What are the two subunits of a ribosome and their respective roles?

80S and 40S; catalyze translation and process rRNA

50S and 30S; bind amino acids and mRNA

70S and 50S; synthesize lipid molecules and export proteins

40S and 60S; bind mRNA and catalyze peptide bond formation (correct)

Which part of the nucleus is primarily involved in the liquid phase surrounding chromatin?

Nucleoplasm Signup and view all the answers

What is the primary purpose of the endomembrane system?

Create, modify, and export cell products like proteins and lipids Signup and view all the answers

What is the primary function of peroxisomes in a cell?

Metabolizing nitrogen-containing compounds and removing toxic lipids Signup and view all the answers

Which organelle is responsible for the process of cellular respiration?

Mitochondria Signup and view all the answers

Which component of ATP makes it a high-energy molecule?

The high phosphoryl transfer potential Signup and view all the answers

What structures make up the cytoskeletal network?

Microtubules, Microfilaments, and Intermediate filaments Signup and view all the answers

What is a significant feature of chloroplasts?

They contain thylakoids stacked into grana. Signup and view all the answers

What is the primary function of the nucleus in eukaryotic cells?

Containment of hereditary information Signup and view all the answers

Which of the following statements about ribosomes is true?

They synthesize proteins by translating mRNA Signup and view all the answers

What is a key feature of the endomembrane system in eukaryotic cells?

It enables compartmentalization of cellular functions Signup and view all the answers

How does the structure of mitochondria assist in energy production?

Their double membrane creates a large surface area for reactions Signup and view all the answers

What are the components of the cytoskeleton primarily made of?

Proteins Signup and view all the answers

Which statement best describes compartmentalization in eukaryotic cells?

It allows for the specialization of cells in multicellular organisms Signup and view all the answers

What role do nuclear pores play in eukaryotic cells?

They regulate movement of molecules in and out of the nucleus Signup and view all the answers

Which feature distinguishes eukaryotic cells from prokaryotic cells?

Compartmentalized organelles Signup and view all the answers

What is the primary purpose of the rough endoplasmic reticulum?

Translation of mRNA and formation of new peptides Signup and view all the answers

Which site on the ribosome is responsible for holding the tRNA carrying the growing polypeptide chain?

P (peptidyl) site Signup and view all the answers

What aligns the Golgi complex within the cell?

It is located between the rough endoplasmic reticulum and the plasma membrane. Signup and view all the answers

Which of the following is a function of the smooth endoplasmic reticulum?

Lipid and steroid hormone production Signup and view all the answers

What role do secretory vesicles play in the cell?

They transport and release proteins. Signup and view all the answers

What is a key characteristic of lysosomes?

They have hydrolytic enzymes that allow them to digest cellular components. Signup and view all the answers

Which function is NOT associated with the smooth endoplasmic reticulum?

Protein synthesis Signup and view all the answers

What occurs to proteins as they move through the Golgi complex?

They undergo modification such as the removal of amino acid chains. Signup and view all the answers

What is the primary function of microtubules in the cytoskeleton?

Intracellular transport of vesicles and organelles Signup and view all the answers

Which type of filament is primarily involved in muscle contraction?

Microfilaments Signup and view all the answers

What is the diameter of microtubules?

25 nm Signup and view all the answers

What type of organization do intermediate filaments provide for the cell?

Structural support and maintenance of cell shape Signup and view all the answers

Which subunits make up microtubules?

Alpha and beta tubulin Signup and view all the answers

What structure is responsible for the nucleation of microtubules?

Centrosome Signup and view all the answers

Which of the following is NOT a function of microfilaments?

Chromosome movement Signup and view all the answers

Which protein is primarily associated with constructing intermediate filaments found in epithelial cells?

Keratin Signup and view all the answers

What do filopodia primarily consist of?

G-actin Signup and view all the answers

Which class of intermediate filaments provides a nuclear scaffold for all cells?

Nuclear lamins Signup and view all the answers

Study Notes

Eukaryotic Cell Structures

Eukaryotic cells contain organelles enclosed by membranes
Understanding the structures and functions of these organelles is crucial to understanding cellular processes

Learning Outcomes

Students need to understand the structures of eukaryotic organelles
Explaining the structure, role, and function of the nucleus is essential
Understanding ribosomes, their roles, and functions is crucial
The endomembrane system is crucial to explaining how mitochondria and chloroplasts generate energy for the cell
The cytoskeleton network, its composition, and its function in cellular activities is key

Modern Cell Theory

All living things are comprised of cells
Cells can have specialized functions within different organisms
The cell is the smallest living unit within all organisms
DNA and RNA are the hereditary information
Cells manufacture new molecules
Cells use organic molecules as energy sources for cellular metabolism
All cells originate from pre-existing cells

Eukaryotic and Prokaryotic Cell Similarities

Both have DNA
Both contain ribosomes
Both have cytoplasm
Both have cell membranes

Eukaryotic and Prokaryotic Cell Differences

Prokaryotic cells lack a nucleus
Prokaryotic cells lack membrane-bound organelles (like mitochondria or chloroplasts)
Eukaryotic cells have a nucleus
Eukaryotic cells have membrane-bound organelles
Prokaryotic cells are generally smaller
Prokaryotic cells have circular DNA without a nucleus (nucleoid)

Compartmentalisation of Activities

Organelles compartmentalize tasks within the cell
This concentrates enzymes and necessary compounds allowing for more efficient processes
This system allows for specialization in specialized eukaryotic cells
This is crucial in multicellular organisms

Membrane-bound Organelles

Membrane-bound organelles in eukaryotes help compartmentalize and organize functions
Organelles include: nucleus, ribosomes, and the endomembrane system

Nucleus

The nucleus is surrounded by the nuclear envelope
The nuclear envelope is a double membrane
The nuclear matrix maintains the shape of the nucleus
Nuclear pores are channels that allow regulated movement of biomolecules into and out of the nucleus

Endomembrane System

The endomembrane system consists of inter-related membrane sacs
This system is responsible for protein synthesis, modification, and transport
Structures of the endomembrane system include: the nuclear envelope, rough ER, smooth ER, Golgi, and lysosomes

Ribosomes

Ribosomes are responsible for protein synthesis.
Ribosomes consist of two subunits: small (40S) and large (60S)
Ribosomes are crucial to the process of translation
Ribosomes contain three binding sites for tRNA (P, A, and E sites)

Endoplasmic Reticulum - Rough ER

The rough ER is studded with ribosomes
Rough ER is responsible for the formation of new peptides
Rough ER increases surface area
Rough ER is a network of interconnected membranous channels
These channels are called cisternae, which are the spaces surrounding the rough endoplasmic reticulum

Endoplasmic Reticulum - Smooth ER

Purpose of smooth ER—production and metabolism of fats and steroid hormones
Calcium storage
Detoxification of drugs and toxins
Smooth and rough ER can be connected to function in a continuous network.

Golgi Complex

The Golgi complex is responsible for protein sorting and modification
Proteins are received from the endoplasmic reticulum
Proteins are modified (removing or adding amino acid chains)
Proteins are then transported to other parts of the cell.
Proteins can potentially be secreted.

Secretory Vesicles

Vesicles contain specialized membrane signals to prepare for fusion with the cellular membrane
Fusion of membranes occurs to release secreted vesicles' contents out of the cell
Membranes integrate with the cellular membrane during secretion

Lysosomes and Peroxisomes

Lysosomes contain hydrolytic enzymes for breaking down cellular wastes or invading substances
Peroxisomes metabolize nitrogen compounds and also break down lipids

Energy and Eukaryotes

Eukaryotic cellular function is greatly dependent on mitochondria (organelles)
Mitochondria involve the fundamental process to generate energy.

ATP (Adenosine Triphosphate)

Energy in cells is primarily in the form of ATP molecules
ATP is an energy-rich molecule with high phosphoryl transfer potential (energy transfer)
ATP-ADP cycle is crucial for transferring energy needed for cellular processes
ATP functions are fundamental in biological systems
ATP is the immediate energy source, not a long-term storage molecule

Mitochondria

Mitochondria are involved in cellular respiration.
Consist of outer and inner membranes (Cristae)
The matrix is found inside the inner membrane
Contains a small circular mitochondrial DNA

Chloroplasts

Chloroplasts are the energy-producing organelles in plant cells
Similar structure to mitochondria with inner and outer membranes.
The stroma contains thylakoids
The thylakoids are stacked to form grana
Photosynthesis in plants takes place in chloroplasts

Cytoskeletal Network

The cytoskeleton is made up of microtubules, microfilaments, and intermediate filaments.
The cytoskeleton helps with maintenance of cell shape and internal transport of molecules

Cytoskeletal Architecture

The cytoskeleton is made up of small subunits that polymerize (combine structures into one large structure)
This process makes it possible for the cell to create and disassemble structures easily and quickly.
Addition of subunits adds a polarity to the cytoskeletal structures

Microtubules

Microtubules are made of alpha and beta tubulin.
They have polarity with plus and minus ends.
Microtubules have a diameter of 25nm
Microtubules are used in cell organization, intracellular transport, and chromosome movement.

Centrosome

Microtubules are nucleated in the cytoskeleton by the centrosome
Centrosome contains barrel-shaped centrioles.

Role of Micro tubules

Microtubules help with cell shape, polarity, intracellular transport of vesicles and organelles, and chromosomal movement.

Role of Microfilaments

Microfilaments help with cell shape and polarity
They also help with cell locomotion, cytokinesis, muscle contraction, and intracellular transport.

Actin Protrusions

Actin protrusions form structures called lamellipodia and filopodia used for cellular movement and adhesion.

Role of microfilaments 2)

Role of microfilaments in cell locomotion
The proteins in the cytoskeleton enable the motion.

Intermediate Filaments

A cytoskeletal composed of multiple proteins
Intermediate filaments have a diameter between 8 to 12nm
They maintain the structure and shape of cells
Nuclear lamina is a type of intermediate filament

Four Classes of Intermediate Filaments

Keratins are in epithelial cells
Vimentin and related proteins are in connective tissue
Desmin is in muscle tissue
Neurofilaments are in nerve tissue
Nuclear lamins are in all animal cells

Disorders of Intermediate Filaments - Keratin Filaments

Genetic disorders involving mutations in proteins that create keratin filaments
These result in defects and easy blistering in the skin.

Disorders of the Nuclear Lamina Progeria

Rare genetic disorder that causes premature aging
Mutated progerin is improperly formed and unable to maintain the nuclear lamina
It limits the cells ability to divide

Summary

Eukaryotic cells have a cytoskeletal structure of filaments to maintain shape.

Studying That Suits You

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Description

Test your knowledge about cell organelles with this quiz focused on their functions and components. Questions cover the nucleolus, endomembrane system, ribosomes, and more. Perfect for biology students looking to reinforce their understanding of cellular structures.