Term
| Separates the cell from its surrounding environment |
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| Thick gel-like substance inside of the cell composed of numerous organelles suspended in watery cytosol; each type of organelle is suited to perform particular functions[image] |
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Term
Large membranous structure near the center of the cell;
Consists of nuclear envelope (composed of two membranes each with essentially the same molecular structure as plasma membrane) surrounding nucleoplasm; nuclear envelope has holes called nuclear pores;
ØContains DNA (heredity molecules), which appear as the following:
•Chromatin threads or granules in nondividing cells
•Chromosomes in early stages of cell division
•Functions of nucleus are functions of DNA molecules; DNA determines both structure and function of cells and heredity
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Made of canals with membranous walls and flat, curving sacs arranged in parallel rows throughout the cytoplasm; extend from the plasma membrane to the nucleus; proteins move through the canals [image] |
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Ribosomes dot the outer surface of the membranous walls
Ribosomes synthesize proteins, which move toward the Golgi apparatus and then eventually leave the cell
Function in protein synthesis and intracellular transportation |
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Definition
| Round Endoplasmic Reticulum |
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Term
No ribosomes border membranous wall;
Functions are less well established and probably more varied than for rough endoplasmic reticulum;
Synthesizes certain lipids and carbohydrates and creates membranes for use throughout cell;
Removes and stores Ca++ from cell’s interior. |
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Definition
| Smooth Endoplasmic Reticulum |
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Term
Many are attached to the rough endoplasmic reticulum and many lie free, scattered through the cytoplasm;
Each ribosome is a nonmembranous structure made of two pieces, a large subunit and a small subunit; each subunit is composed of rRNA ;
Ribosomes in the endoplasmic reticulum make proteins for “export” or to be embedded in the plasma membrane; free ribosomes make proteins for the cell’s domestic use
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Membranous organelle consisting of cisternae stacked on one another and located near the nucleus;
Processes protein molecules from the endoplasmic reticulum;
Processed proteins leave the final cisterna in a vesicle; contents may then be secreted to outside the cell
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Made of microscopic membranous sacs that have “pinched off” from Golgi apparatus;
The cell’s own digestive system; enzymes in lysosomes digest the protein structures of defective cell parts, including plasma membrane proteins, and particles that have become trapped in the cell
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Hollow, protein cylinders found throughout the cytoplasm;
Break down abnormal/misfolded proteins and normal proteins no longer needed by the cell;
Break down protein molecules one at a time by tagging each one with a chain of ubiquitin molecules and unfolding it as it enters the proteasome, then breaking apart peptide bonds
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Small membranous sacs containing enzymes that detoxify harmful substances that enter the cells;
Often seen in kidney and liver cells |
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Made up of microscopic sacs; wall composed of inner and outer membranes separated by fluid; thousands of particles make up enzyme molecules attached to both membranes;
The “power plants” of cells; mitochondrial enzymes catalyze series of oxidation reactions that provide about 95% of cell’s energy supply;
Each mitochondrion has a DNA molecule, allowing it to produce its own enzymes and replicate copies of itself
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| The cell’s internal supporting framework made up of rigid, rodlike pieces that provide support and allow movement and mechanisms that can move the cell or its parts [image] |
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An area of the cytoplasm near the nucleus that coordinates the building and breaking of microtubules in the cell;
Nonmembranous structure also called the microtubule-organizing center (MTOC);
Plays an important role during cell division;
The general location of the centrosome is identified by the centrioles |
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found in epithelial cells that line the intestines and other areas where absorption is important; they help to increase the surface area manyfold |
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cell processes that have cylinders made of microtubules at their core; cilia are shorter and more numerous than flagella; flagella are found only on human sperm cells |
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Fibers on the outer surface of each desmosome interlock with each other; anchored internally by intermediate filaments of the cytoskeleton;
Spot desmosomes, connecting adjacent membranes, are like “spot welds” at various points;
Belt desmosomes encircle the entire cell like
a collar |
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membrane channels of adjacent plasma membranes adhere to each other; have two effects:
Form gaps or “tunnels” that join the cytoplasm of two cells;
Fuse two plasma membranes into a single structure |
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Occur in cells that are joined by “collars” of tightly fused material;
Molecules cannot permeate the cracks of tight junctions;
Occur in the lining of the intestines and other parts of the body, where it is important to control what gets through a sheet of cells
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