What is the cytoskeleton?
Network of protein fibers that help maintain the shape of the cell and secures some organelles in specific positions, allow cytoplasm and vesicles to move within the cell, and enable unicellular organisms to move independently.
three types of fibers within the cytoskeleton
- microfilaments
- intermediate filaments
- microtubules.
Define actin
A globular structural protein that polymerizes in a helical fashion to form an actin filament (or microfilament)
Define myosin
a large family of motor proteins found in eukaryotic tissues, allowing mobility in muscles
Filamentous means what?
Having the form of threads or filaments.
What is responsible for transport along microtubules? [2]
Microtubules provide long tracks along which a broad range of organelles and vesicles are transported by kinesin and dynein motors. Motor protein complexes also tether cargoes to cytoskeletal filaments, helping facilitate their interaction and communication.
Discuss the microtubule’s structures.
A microtubule is a polar structure, its polarity arising from the head-to-tail arrangement of the α- and β-tubulin dimers in a protofilament. Because all protofilaments in a microtubule have the same orientation, one end of a microtubule is ringed by α-tubulin, while the opposite end is ringed by β-tubulin.
What are cilia and flagella?
Cilia and flagella are hair-like structures that assist with locomotion in some cells, as well as line various structures to trap particles
What are motor proteins and where are they found and what do they interact with?
Motor proteins are molecular motors that use ATP hydrolysis to move along cytoskeletal filaments within the cell. They fulfill many functions within biological systems, including controlling the sliding of filaments in muscle contraction and mediating intracellular transport along biopolymer filament tracks.
Microfilaments, What are they?
Microfilaments, which are the thinnest part of the cytoskeleton, are used to give shape to the cell and support all of its internal parts.
Describe the structure and function of microfilaments.
- Microfilaments assist with cell movement and are made of a protein called “actin” which works with another protein called “myosin” to produce muscle movements, cell division and cytoplasmic streaming.
- Microfilaments keep organelles in place within the cell. Microfilaments have a diameter of about 7 nm, and are made of two intertwined strands of a globular protein called actin. For this reason, microfilaments are also known as actin filaments.
Fun fact on actin and myosin.
Actin and myosin are plentiful in muscle cells. When your actin and myosin filaments slide past each other, your muscles contract.
Microfilaments can disassemble, why?
They can depolymerize (disassemble) and reform quickly, thus enabling a cell to change its shape and move. White blood cells (your body’s infection-fighting cells) make good use of this ability. They can move to the site of an infection and engulf the pathogen.
Describe the roles of microtubules as part of the cell’s cytoskeleton.
are part of the cell’s cytoskeleton, helping the cell resist compression, move vesicles, and separate chromosomes at mitosis.
How would you describe the structures of cilia and flagella?
: a “9+2 array,” meaning that a ring of nine microtubules is surrounding two microtubules.
Microtubules important function
Microtubules attach to replicated chromosomes during cell division and pull them apart to opposite ends of the pole, allowing the cell to divide with a complete set of chromosomes in each daughter cell.
Define microtubule
they are small hollow tubes made of protein and found in cells; part of the cytoskeleton.
Define flagellum:
a flagellum is a lash-like appendage that protrudes from the cell body of certain prokaryotic and eukaryotic cells.
More on cytoskeleton:
A cellular structure like a skeleton, contained within the cytoplasm.
Describe the structure of microtubules.
- Microtubules are the largest element of the cytoskeleton.
- The walls of the microtubule are made of polymerized dimers of α-tubulin and β-tubulin, two globular proteins.
- Like microfilaments, microtubules can dissolve and reform quickly.
- Microtubules are hollow, with walls consisting of 13 polymerized dimers of α-tubulin and β-tubulin. They are also the structural elements of flagella, cilia, and centrioles.
Intermediate Filaments.
- cytoskeletal components found in animal cells.
- Intermediate filaments contribute to cellular structural elements and are often crucial in holding together tissues like skin.
- Intermediate filaments have an average diameter of 10 nanometers.
Flagella and Cilia
- Flagella are long, hair-like structures that extend from the plasma membrane and are used to move an entire cell (for example, sperm, Euglena). When present, the cell has just one flagellum or a few flagella.
- When cilia are present, however, many of them extend along the entire surface of the plasma membrane. Cilia are short, hair-like structures that are used to move entire cells (such as paramecia) or move substances along the outer surface of the cell (for example, the cilia of cells lining the Fallopian tubes that move the ovum toward the uterus, or cilia lining the cells of the respiratory tract that trap particulate matter [dust] and move it toward your nostrils.
Flagella and Cilia share a common structural arrangement of microtubules called
“9 + 2 array.” —- a single flagellum or cilium is made of a ring of nine microtubule doublets surrounding a single microtubule doublet in the center.
What are the two main systems in cellular movements:
1) specialized motor proteins & microtubules
2) actin microfilaments and myosin motor molecules.
