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28 terms

A & P Chapter 3 - Nonmembranous Organelles

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cytoskeleton
provides an internal protein framework that gives the cytoplasm strength and flexibility
The _________ of all cells includes microfilaments, intermediate filaments, and microtubules
cytoskeleton
Muscle cells contain ________ __________ in the cytoskeleton in addition to the 3 types of filaments contained in all cells
thick filaments
The ___________ plays a key role in the metabolic organization of the cell by determining where in the cytoplasm key enzymatic reactions occur and where specific proteins are synthesized
cytoskeleton
microfilaments
the smallest of the cytoskeletal elements; typically less than 6 nm in diameter
typical microfilaments are composed of the protein ________
actin
3 major functions of microfilaments
1. Anchor the cytoskeleton to integral proteins of the cell membrane; provides the cell additional strength and attach the cell membrane to the enclosed cytoplasm
2. Determine the consistency of the cytoplasm. Where microfilaments form a dense, flexible network, the cytoplasm has a gelatinous consistency; where they are widely dispersed, the cytoplasm is more fluid.
3. Actin (a microfilament) can interact with the protein myosin to produce active movement of a portion of a cell or to change the shape of the entire cell.
intermediate filaments
protein composition varies among cell types; range from 7 to 11 nm in diameter
3 major functions of intermediate filaments
1. Strengthen the cell and help maintain its shape
2. Stabilize the positions of the organelles
3. Stabilize the position of the cell with respect to surrounding cells through specialized attachment to the cell membrane
__________ filaments, which are insoluble, are the most durable of the cytoskeletal elements
intermediate
microtubules
hollow tubes built from the globular protein tubulin; the largest components of the cytoskeleton, with a diameter of about 25 nm
5 major functions of microtubules
1. Form the primary components of the cytoskeleton, giving the cell strength and rigidity and anchoring the position of major organelles
2. The dis-assembly of microtubules provides a mechanism for changing the shape of the cell
3. Can move vesicles or other organelles within the cell, using proteins called molecular motors.
4. During cell division, microtubules form the spindle apparatus, which distributes duplicated chromosomes to opposite ends of the dividing cell.
5. Form structural components of organelles, such as centrioles and cilia.
thick filaments
are relatively massive bundles of subunits composed of the protein myosin; about 15 nm in diameter, and appear only in muscle cells
microvilli
small, finger-shaped projections of the cell membrane on their exposed surfaces; greatly increase the surface area exposed to the extracellular environment
centrioles
cylindrical structures composed of short microtubules (9 groups of 3). During cell division, the centrioles form the spindle apparatus associated with the movement of DNA strands
__________ are found in all animal cells capable of undergoing cell division
centrioles
Name 4 types of cells that have no centrioles and are incapable of dividing
mature red blood cells
skeletal muscle cells
cardiac muscle cells
typical neurons
centrosome
the cytoplasm surrounding the centrioles
cilia
relatively long, slender extensions of the cell membrane
Name two places cilia are found
on cells lining the respiratory tract
on cells lining the reproductive tract
__________ can beat rhythmically to move fluids or secretions across the cell surface
cilia
ribisomes
the organelles responsible for protein synthesis
composition of a ribosome
roughly 60 percent ribosomal RNA
40 percent protein
_________ are made up of two subunits
ribosomes
before protein synthesis can begin, a small and large ribosomal subunit must join together with a strand of _________
messenger RNA
free ribosomes
are scattered throughout the cytoplasm; the proteins they manufacture enter the cytosol
fixed ribosomes
are attached to the endoplasmic reticulum; the proteins they manufacture enter the ER, where they are modified and packaged for secretion
proteasomes
are organelles that contain an assortment of protein-digesting enzymes, or proteases; are responsible for removing and recycling damaged or denatured proteins, and for breaking down abnormal proteins