The Cytosol and Cytoskeleton

Flashcards covering the cytosol, cytoskeleton components (microtubules, intermediate filaments, actin filaments), and the function of motor proteins, cilia, and flagella based on the lecture notes.

What is the cytosol and where is it located in a eukaryotic cell?

The cytosol is the region of a eukaryotic cell that is outside the membrane-bound organelles but inside the plasma membrane. It is a central coordinating region for metabolism.

How does the cytoplasm differ from the cytosol in a eukaryotic cell?

The cytoplasm refers to the region enclosed by the plasma membrane, including both the cytosol and the organelles.

Define metabolism, and differentiate between catabolism and anabolism.

Metabolism is the sum of chemical reactions by which cells produce materials and utilize energy. Catabolism involves the breakdown of molecules into smaller components, while anabolism involves the synthesis of molecules and macromolecules.

What is translation, and where are ribosomes found in a cell?

Translation is the process where amino acids are covalently connected to form a polypeptide, using information within mRNA. Ribosomes are found freely floating in the cytosol, attached to the nuclear envelope or endoplasmic reticulum, and within mitochondria or chloroplasts.

What is the cytoskeleton, and what are its three main types of protein filaments?

The cytoskeleton is a network of protein filaments found primarily in the cytosol and along the inner nuclear membrane. Its three types are microtubules, intermediate filaments, and actin filaments.

Describe the structure and protein composition of microtubules.

Microtubules are long, hollow, cylindrical structures about 25 nm in diameter, composed of α- and β-tubulin protein subunits. They are polar, with a plus end and a minus end.

What is dynamic instability in relation to microtubules?

Dynamic instability is the phenomenon where a single microtubule oscillates between growing (only at the plus end) and shortening phases (at either end), which is important for activities like chromosome sorting during cell division.

What are the common functions of microtubules?

Microtubules are important for cell shape, organization of cell organelles, chromosome sorting in cell division, intracellular movement of cargo, and cell motility (cilia and flagella).

What is a microtubule-organizing center (MTOC), and which specific MTOC is found in animal cells?

A MTOC is a site in a eukaryotic cell from which microtubules grow. In non-dividing animal cells, the single MTOC near the nucleus is called the centrosome, which contains centrioles.

Describe the structure and common functions of intermediate filaments.

Intermediate filaments are about 10 nm in diameter, forming a twisted, ropelike structure from staggered alignment of various proteins (e.g., keratin, lamin). They function in cell shape, mechanical strength, and anchoring cell and nuclear membranes, and are relatively permanent.

What are actin filaments, also known as microfilaments, and what are their key functions?

Actin filaments are the thinnest cytoskeletal filaments, approximately 7 nm in diameter, composed of two intertwined strands of actin monomers. They play key roles in cell shape, cell strength, muscle contraction, intracellular movement of cargo, cell movement (amoeboid movement), and cell division in animal cells.

Describe the general structure of a motor protein and its three key domains.

Motor proteins use ATP to promote various movements and consist of three domains: a head (binds/hydrolyzes ATP, interacts with filament), a hinge (bends causing movement), and a tail (attaches to cargo or other proteins).

What are the three main ways that motor proteins promote cellular movements?

Motor proteins promote movement in three ways: moving cargo along a fixed filament, moving a filament with a fixed motor protein, or causing a filament to bend when both the motor protein and filament are fixed.

Explain how motor proteins cause a filament to bend, using an example.

When motor proteins and filaments are both fixed in place due to linking proteins, the motor protein's action (e.g., dynein attempting to walk along microtubules) exerts a force that causes the filament to bend. This is seen in the movement of cilia and flagella.

What are flagella and cilia, and what motor protein is involved in their movement?

Flagella and cilia are cell appendages that enable movement in certain eukaryotic cells. They both generate bending movements using microtubules and the motor protein dynein.

Describe the internal structure of flagella and cilia.

The internal structure of flagella and cilia is called the axoneme, which contains microtubules arranged in a '9 + 2 array' (9 outer doublet microtubules and 2 central single microtubules), along with dynein arms and radial spokes. They emanate from basal bodies anchored to the plasma membrane.