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57 Cards in this Set

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  • Back
Which organelles are visible with the light microscope?
-plasma membrane
-nucleus
-golgi
-nucleolus
-mitochondria
-centriole
Cell membrane composition
-composed of phospholipids, cholesterol and protein molecules
-bi-layered arrangement
-hydrophobic portion is at the center
-hydrophilic is on the surfaces
Glycocalyx
-consists of the glycoproteins, glycolipids and secreted proteoglycans that make up the carbohydrate rich zone of the cell surface
-carries a "code"
Membrane protein functions
-ion pumps
-channels
-membrane receptors (recognizes and binds specific ligands such as hormones, neurotransmitters, etc)
-enzymes
-structural proteins
Endocytosis (3 types)
-Pinocytosis: non-specific ingestion of fluid and small protein molecules via small vesicles

-Receptor-mediated endocytosis: allows entry of specific molecules (cargo receptors)

-Phagocytosis: ingestion of large particles such as bacteria, cell debris, etc performed by specialized cells called macrophages or histiocytes
Endosomes
-membrane bound structures associated with any of the endocytotic pathways
Early endosomes
-near cell membrane
-important for sorting and recycling of proteins internalized by various endocytotic pathways
Late endosomes
-formed from early endosomes
-travel deeper into the cytoplasm
-eventually develop into lysosomes
-regulate amount of transporter proteins to and from the plasma membrane
Lysosomes
-membrane bound organelles
-rich in hydrolytic enzymes synthesized by the rER, modified by the Golgi and packed into the lysosomes
Lysosomal enzymes
-acid phosphatase
-glucuronidase
-ribonuclease
-lipase
-collagenase
Phagolysosomes
-primary lysosomes fuse with phagosomes to form secondary lysosomes aka phagolysosomes
Autophagy
-removal, digestion and reprocessing of damaged and worn out organelles
-lysosomes play a big role in this process
Heterophagy
-process by which lysosomes ingest and breakdown material from teh external environment
-performed by macrophages
Lysosomal Storage Diseases
-can result in the accumulation of substrates within the cell and can make cells swell
Rough Endoplasmic Reticulum
-studded with ribosomes so it functions in protein synthesis
-cells with a lot of rER have basophilic cytoplasm
-continuous with the outer layer of the nuclear envelope
Smooth Endoplasmic Reticulum
-no ribosomes
-important in metabolism of exogenous chemicals that may be toxins
-these detox reactions are performed by the p-450 mixed function oxidase system
-common in the liver and in cells that synthesize and secrete steroid hormone
Golgi
-functions in post-translational modification and sorting and packing of proteins synthesized by the cell
-found in cells that make a lot of membrane associated protein
-appear as a clear zone in H&E
Mitochondria
-have circular DNA
-have their own ribosomes
-abundant in cells with high energy requirements
How do mitochondria make ATP?
-beta oxidation of fatty acids
-oxidative phosphorylation
Mitochondrial role in apoptosis
-mediated by release of cytochrome c through the mitochondrial membrane into the cytoplasm
-regulated by Bcl-2 proteins which initiate a cascade of proteolytic enzymatic reactions resulting in DEATH
Peroxisomes
-contain catalase and other oxidative enzymes
-beta oxidation of fatty acids also occurs
-prominent in hepatocytes and renal tubular cells
Cell Membrane Injury
-occurs through: chemicals, infectious agents, physical trauma, nutritional imbalances and immune mediated reactions
-results in: loss of ability to maintain a selectively permeable barrier
Carbon tetrachloride Toxicity
-liver cell toxin that injures the cell membrane when it is converted to the trichloromethyl radical CCl3 by the sER
Perforation of cell membrane
killing strategy used by:
-bacterial toxins (E.Coli, Staph aureus)
-perforins (natural killer cells)"
-complement
-defensins (antibacterial molecules)
Actin filaments
-6-8nm in diameter
-found in bundles close to the cell membrane
-functions:
-internal mechanical support
-anchor membrane junctions
-"railroad track" for internal transport of vesicles and organelles
-component of cilia and microvilli
-scaffold for myosin in muscle cells
Spectrin
-cytoskeletal protein that lines the inner surface of the plasma membrane
-arranged in a pentagonal or hexagonal configuration
-maintains cytoskeletal structure and membrane shape
Intermediate Filaments
-8-10nm in diameter
-supporting function in the cytoplasm
-subdivided into four classes
1. keratins or cytokeratins-epithelial
2. vimentin and desmin-mesenchymal
3. neurofilaments- nerve cells
4. lamins- nuclear envelope and nuceloplasm
Which cytoskeleton component helps diagnose cancer and how?
-intermediate filaments
-antibodies directed toward them are used to classify poorly differentiated maligmant tumors based on embryonic germ layer origin
Disease involving actin filaments
-toxins of poisonous mushrooms (Amanita phalloides) binds to actin and prevents their depolarization
-results in rapid cell death by necrosis
Microtubules
-20-25nm in diameter
-ridged, non-branching, hollow tubes
-forms a system of connections in the cytoplasm on which vesicles can move
-unstable structures that are constantly assembling/diassembling
-essential to the movement of chromosomes during mitosis and meiosis
-represent the core of cilia and flagella
Centrioles
-paired, short, rod-like cylinders that are formed from microtubules
-surrounded by golgi
-associated with a zone of amorphous pericentriolar material known as the microtubule organizing center
Microtubule Organizing Center (MTOC)
-zone of amorphous pericentriolar material
-microtubules are formed here and directed to their locations in the cell
Intracellular Inclusions (General)
-found in cytoplasm and nucleus of cells
-products of metabolic activity and have special staining properties
Lipofuscin
-intracellular inclusion
-brown/yellow pigment seen in neurons and muscle cells
-result of oxidative degradation of mitochondria and lysosomal digestion
Hemosiderin
-intracellular inclusion
-dark brown/brown/yellow iron containing pigment that cannot be distinguished from lipofuscin in H&E
Glycogen
-liver cells and striated muscle fibers have a lot
-periodic acid-schiff stain is used to show this material (magenta)
Lipid
-cells with lipid appear to have clear space
-oil red-O stains lipid bright red
Pathologic Intracellular Inclusions
-viral infection
-RNA virus->cytoplasm
-DNA virus->nucleus
-toxicity
-alcohol->mallory body
-lead-> intranuclear inclusion
Karyogenic hypothesis
-nucleus resulted from a process of segregating DNA to a region of the cell where another membrane surrounded it
-not likely to be correct
Endokaryotic hypothesis
-one prokaryote was phagocytosed by another and survived and became incorporated
What advantages do eukaryotic cell have over prokaryotic cells?
1. development of a larger genome
2. spatial separation of transcription and translation
Chromatin
-nucleoprotein complex which is composed of DNA in addition to structural proteins called histones
-
Heterochromatin
-densely stained, clumped region
-low level of transcription
Euchromatin
-uncoiled/stretched out regions of DNA
-actively being read and transcribed
Nuclear pores
-holes in the nuclear membrane that allow communication between nucleoplasm and cytoplasm
-allows passage of RN?a dn ribonucleoproteins between nucleus and cytoplasm
Nuclear lamina
-thin, electron dense protein layer
-has a supporting or nucleoskeletal function
-composed of proteins called lamins (similar to intermediate filaments)
Lamin Disease
-impairment of nuclear lamine is associated with several human genetic disorders including progeria
Nucleolus
-non-membrane bound region of the nucleus
-contains transcriptionally active RNA genes
-site of rRNA synthesis
-prominent in cells secreting protein
Telomeres
-region of highly repetitive DNA at the end of a chromosome
-helps prevent loss of genetic information due to the fact that DNA polymerase cannot replicate all of the way to the end of a chromosome
-cancer cells have telomerase that is constantly turned on
Cell Turnover
-measured by counting the number of mitotic figures in a single high powered light microscopic field

-static: no longer capable of division (neurons, cardiac muscle)
-stable: undergoing periodic division (liver, CT cells)
-continuously dividing: always dividing (epithelial cells, bone marrow)
Interphase
-period of continuous growth
-Subdivided into:
G1
S
G2
Mitosis/M phase
-halving of genome occurs here
-subdivided into:
Prophase
Metaphase
Anaphase
Telophase
Mitotic catastrophe
-results in aberrant chromosome segregation with the generation of aneuploid cells
Hyperplastic/Neoplastic Disease
-excessive cell production
Hypoplasic/atrophic disease
-decreased cell division or excessive cell loss
Necrosis
-initated by external factors such as hypothermia, heat, low pH, radiation, microbial pathogens
-die by swelling and membrane rupture
-results in a secondary inflammatory response
Apoptosis
-internal programming to eliminate cells no longer needed or cells with irreparable damage
-is usually a normal process (unlike necrosis)
-can be induced by external factors:
-tumor necrosis factor produced by macrophages in response to bacterial infection
-TGF-beta
-free radicals
-UV light
-ionizing radiation
-also activated when accidents in the cell cycle result in malfunction of DNA damage checkpoints