Eukaryotic Cell Structure and Organelles Overview

What is the primary function of the plasma membrane in a eukaryotic cell?

It encloses and defines the homeostatically regulated interior environment of the cell, separating the cytosol from the extracellular space.

What does the cytosol include in a eukaryotic cell?

All internal volume within the cell that is not enclosed within an organelle membrane, essentially the space between organelles.

What metabolic pathways occur in the cytosol?

Numerous specific metabolic pathways, including glycolysis, and all catalytic activity of the cell's 80S ribosomes.

What is the significance of the reducing chemical environment of the cytosol?

It plays a crucial role in various metabolic processes and reactions within the cell.

What are the two layers of the nuclear envelope?

The outer nuclear envelope and the inner nuclear envelope.

What is the function of nuclear pores?

They connect the nucleoplasm and cytosol, allowing for the exchange of substances while bypassing the perinuclear space.

What does the endoplasmic reticulum (ER) membrane define?

It defines the ER lumen and is physically continuous with the outer nuclear envelope.

What is the role of the outer mitochondrial membrane (OMM)?

It defines the outer boundary of the mitochondrion and separates the cytosol from the mitochondrial intermembrane space.

What does the inner mitochondrial membrane (IMM) enclose?

It encloses the mitochondrial matrix and separates the intermembrane space from the mitochondrial matrix.

What are organelles defined as in the context of eukaryotic cells?

Membrane-bound compartments that are typically present in eukaryotic cells.

What is the perinuclear space?

The space between the two layers of the nuclear envelope.

How is the nucleoplasm defined in relation to the cytoplasm?

Some cell biologists consider the nucleoplasm separate from the cytoplasm, but it is included as part of the cytoplasm in this course.

What is the minimum standard set of membranes in a typical eukaryotic cell?

Plasma membrane, nuclear envelope, and endoplasmic reticulum membrane.

What is the function of the cytoplasm in a eukaryotic cell?

It includes the cytosol plus all organelle interiors, providing a medium for cellular processes.

What distinguishes organelles from other functional units in eukaryotic cells?

Organelles are specifically defined as membrane-bound compartments, while other functional units may not be enclosed by membranes.

What is the importance of the membrane systems in eukaryotic cells?

They define and separate various compartments, allowing for specialized functions and processes within the cell.

What is a characteristic of eukaryotic cells regarding organelles?

Eukaryotic cells typically have a standard set of organelles that are almost always present.

What is meant by 'endomembrane system' in eukaryotic cells?

A system of membranes that includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and vesicles, which work together to modify, package, and transport lipids and proteins.

What is the role of the cytosol in eukaryotic cells?

It serves as the site for metabolic pathways and the activity of ribosomes.

What defines the lumen of organelles in eukaryotic cells?

The membranes of organelles and vesicles separate the lumen from the surrounding cytosol.

What is the relationship between the ER membrane and the nuclear envelope?

The ER membrane is continuous with the outer nuclear envelope, defining the ER lumen.

What are some examples of additional major organelles in eukaryotic cells?

Examples include lysosomes, peroxisomes, and Golgi apparatus, which may not be universally present.

What is the primary function of the nucleus in a eukaryotic cell?

It houses the nuclear genome, facilitates DNA replication and maintenance, synthesizes nuclear-encoded RNAs, and biogenesis of ribosomal subunits.

What are the two distinct compartments of the nucleus?

Nucleoplasm and perinuclear space.

What is the role of nucleoplasm?

It houses the nuclear genome in the form of chromatin and is involved in DNA replication, RNA synthesis, and ribosomal subunit biogenesis.

What is the function of the endoplasmic reticulum (ER)?

It accepts newly synthesized polypeptides, facilitates protein folding, serves as a calcium reservoir, and carries out lipid biosynthesis.

What distinguishes rough ER from smooth ER?

Rough ER is involved in protein synthesis and processing, while smooth ER is involved in lipid biosynthesis and does not have ribosomes.

What is the Golgi apparatus responsible for?

Final processing, sorting, and targeting of proteins synthesized in the ER.

What are the three regions of the Golgi apparatus?

Cis Golgi (receiving zone), medial Golgi (processing zone), and trans Golgi (sorting and packaging zone).

What are endosomes and their function?

Endosomes are organelles that receive proteins from the Golgi and materials from the cell surface for processing.

What is the function of lysosomes?

They contain hydrolytic enzymes for degrading endocytosed materials.

What is the difference between classic lysosomes and endolysosomes?

Classic lysosomes are sacs of enzymes for degradation, while endolysosomes form when lysosomes fuse with late endosomes.

What is the role of vacuoles in eukaryotic cells?

They can store materials, maintain osmotic balance, and carry out degradative functions.

What are peroxisomes and their primary function?

They carry out oxidative metabolic processes, particularly neutralizing reactive oxygen species.

What is the primary function of mitochondria?

They are involved in aerobic ATP production and various metabolic processes.

What is the structure of plastids?

Plastids have an outer and inner membrane and contain internal compartments such as stroma and thylakoids.

What is the main function of chloroplasts?

They carry out photosynthesis and can produce ATP in autotrophic eukaryotes.

What are ribosomes and their role in the cell?

Ribosomes are responsible for synthesizing new polypeptides, either in the cytosol or on the ER.

What are the three types of ribosomes found in eukaryotic cells?

Cytosolic 80S ribosomes, membrane-bound 80S ribosomes, and mitochondrial 70S ribosomes.

What is the function of proteasomes?

They degrade cytosolic proteins that are tagged for destruction.

What is the role of the cytoskeleton in eukaryotic cells?

It provides structural support, facilitates intracellular transport, and contributes to cell motility.

What are flagella and cilia used for?

They are used for cell motility or moving extracellular materials across the cell surface.

What is the difference between flagella and cilia?

Flagella are long and whip-like, while cilia are shorter and more compact.

What is the nuclear genome composed of?

Linear dsDNA molecules complexed with proteins, forming chromatin.

What is the mitochondrial genome (mtDNA)?

It consists of multiple identical copies of a single circular chromosome.

What is the plastid genome (cpDNA)?

It consists of multiple identical copies of a single circular or linear chromosome.

What is the function of the actin cytoskeleton?

It provides structural scaffolding and contributes to cell motility.

What is the role of intermediate filaments in eukaryotic cells?

They mechanically strengthen and stiffen the cytoplasm.

What is the function of vesicles in a eukaryotic cell?

They transport materials between different organelles.

What is the significance of the endomembrane system?

It consists of organelles that work together to modify, package, and transport lipids and proteins.