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Cell Anatomy
2113L McKinney
Term | Definition |
---|---|
plasma membrane / cell membrane | physical boundary separates the extracellular fluid surrounding the cell from the cell interior. Regulates movement of ions, molecules & other substances into & out of cell. |
extracellular fluid | fluid outside the cell |
nucleus | central structure that encases and proects the chromosomes; controls protein synthesis, gene action, cell division, metabolic rate |
organelles | all internal structures |
cytoplasm | volume inside the plasma membrane but outside the nucleus. Made up of solid components; organelles except nucleus; suspended in liquid - cytosol |
cytosol | just the liquid part of cytoplasm |
nonmembranous organelles | directly exposed to cytosol: ribosomes; microvilli; centrioles; cytoskeleton; cilia; and flagella |
membranous organelles | enclosed in phospholipid membrane that isolates them from cytosol: nucleus; endoplasmic reticulum; Golgi apparatus; lysosomes; peroxisomes, mitochondria |
microvilli | small folds in the plasma membrane that increase the surface area of the cell to absorb extracellular material, nutrients, at a greater rate |
centrioles | paired organelles composed of microtubules which are small hollow tubes made of the protein tubulin; if cell division: replicate; one pair migrates to each pole of cell radiating spindle fibers from each that pull chromosomes of nucleus apart |
centrosome | area surrounding the pair of centrioles in a cell. Cell not dividing: one pair; dividing cell: replicates - 2 pair. |
cytoskeleton | made from microtubules; structural support and anchors organelles |
cilia | short hair-like projections that extend from the plasma membrane. Common to respiratory and reproductive systems |
flagellum | single, long projection for locomotion. Spermatozoon is the only human cell with it. |
Ribosomes | direct protein synthesis; consists of 1 large & 1 small subunit that clamp around mRNA molecule to coordinate protein synthesis |
Free ribosomes | occur in the cytoplasm |
Fixed ribosomes | attached to the endoplasmic reticulum |
chromatin | uncoiled chromosomes consisting of DNA and protein molecules; responsible for dark appearance of nucleus in stained specimen |
nuclear envelope | surrounds the nuclear material; contains pores through which instruction molecules from nucleus pass into cytosol |
nucleolus | produces ribosomal RNA molecules for the creation of ribosomes; darker stained region inside nucleus |
Endoplasmic reticulum | surrounds the nucleus; functions in the synthesis of organic molecules, transport of materials within cell, storage of molecules. Materials may pass into Golgi apparatus for transport out of cell |
rough ER | has ribosomes attached to surface; proteins produced in ribosomes on outer surface enter and assume the complex folded shape of ER. |
Smooth ER | lacks ribosomes; involved in synthesis of many organic molecules such as cholesterol and phospholipids. in reproductive cells, it produces sex hormones; in liver cells synthesizes & stores glycogen; muscle & nerve cells - stores Ca++ |
Golgi apparatus | series of flattened saccules adjoining the ER; ER may pass protein molecules in transport vesicles here for modification & secretion; cell products such as mucus are synthesized, packaged and secreted by this |
exocytosis | process where small secretory vesicles pinch off the saccules of the Golgi apparatus, fuse with the plasma membrane, then rupture; release contents into extracellular fluid. Phospholipid membranes of empty vesicles contribute to renewal of plasma membrane |
lysosomes | vesicles produced by Golgi apparatus; filled with powerful enzymes that digest worn-out cell components & destroy microbes; some dissolved material is used to rebuild organelles. White blood cells trap bacteria & release these to digest bacteria |
peroxisomes | vesicles filled with enzymes that break down fatty acids and other organic molecules; metabolize H2O2 - hydrogen peroxide into oxygen and water |
mitochondria | produce useful energy; is wrapped in double layer phospholipid membrane. Inner layer is fingerlike (cristae). Metabolic enzymes passed along cristae to produce ATP. Muscles & nerve have many of these. Mature red blood cells lack & have low metabolic rate |
mitosis | chromatin in the nucleus condenses into chromosomes & is equally divided between the two forming cells. each daughter cell has 23 pairs of chromosomes |
cytokinesis | occurs toward end of mitosis; separates the cytoplasm to produce the two daughter cells |
Interphase | most of the time cell is not dividing and is in interphase: carries out various functions and prepares for division; nucleus visible & darker nucleolus; G0 phase, G1 phase, S phase; G2 phase |
G0 phase | cell performs its specialized functions; is not preparing to divide (interphase) |
G1 phase | protein synthesis, growth, replication of organelles, including the centriole pair (interphase) |
S phase | replication of DNA; afterward each chromosome is double stranded and consists of two chromatids; 1 chromatid is original strand, other is an identical copy. Chromatids held together by centromere (interphase) |
G2 phase | another time for protein synthesis; by now replication of the centriole pair is complete |
M phase | is the time of mitosis, nuclear material divides. Prophases; metaphase; anaphase; telophase |
Prophase | chromosomes visible in nucleus; chromosomes start long & disorganized; nuclear envelope breaks down; chromosomes shorten, go to center; 2 centriole pairs start go opposite sides ; microtubules fan as spindle fibers from centrioles across cell. (mitosis) |
Metaphase | chromosomes line up in middle at metaphase plate; spindle fibers across cell pole-to-pole & attach to centromeres of chromosomes; (mitosis) |
Anaphase | separation of chromosomes! spindle fibers pull apart chromatids of chromosome, drag to opposite poles; individual chromatids = chromosomes; cleavage furrow develops; plasma membrane pinches; cytokinesis end of this phase (mitosis) |
Telophase | cytokinesis partitions cytoplasm of cell; mitosis nears completion; each batch of chromosomes unwinds inside new nuclear envelope; each daughter has set organelles & nucleus with complete set of genes; daughter cells begin in interphase (mitosis) |