Unit 4 Flashcards
Describe the origin, basic structure and fission/fusion of mitochondria.
Thought to have come from endocytosis of bacteria early in eukaryotic development.
Double membrane. Outer membrane porous, inner cell very tight.
Fission/fusion of mitochondria is very important to maintain mitochondrial health to help repair/replace damaged/inactive channels.
Describe the basic machinery of mitochondria import.
Import through outer membrane is mostly passive, while import through inner membrane requires ATP activity by Translocase of Inner Membrane (TIM) complexes.
State the basic principles of electron transport and ATP production in mitochondria.
Beta-oxidation of Acetyl-CoA produces NADH, NADPH, FADH. These transport H+ out of the matrix and reduce O2 to H2O. Proton gradient (charge and concentration) drive ATP-ase. ATP is exported out of and ADP imported into the matrix via an antiporter.
Explain the basic mechanisms of cell death regulation by mitochondria.
Apoptosis is regulated by the Mitochondria’s release of Cytochrome-C into the cytosol. Cyt-C binds with other proteins forming apoptosomes which activate caspases.
During ischemic cell death (necrosis) mitochondria release H+ and cyt-c into cytosol. Lack of ATP production causes cell to lyse.
State the principles of mitochondria quality control.
Damaged mitochondria are at risk of producing reactive oxygen species which can negatives impact the cell. As such, the quality of mitochondria function is tightly regulated. If faulty, the Mitochondria fuse and then redistribute properly working machinery. If excessive, cell apoptoses.
Describe the role of mitochondria in senescence and some of the mitochondria‐related diseases.
Increased dysfunction of mitochondria leads to neuronal degeneration leading to diseases such as optic atrophy and Charcot-Marie-Tooth.
State the structural arrangements, classifications, and functions of epithelial tissues, and state their general structural relationships (orientation) to connective tissue, blood vessels, muscle, and neurons (peripheral nervous tissue).
Usually attached to a connective surface. Have polarity - Apical vs. Basal surfaces and serve to protect, absorb, secrete, or signal.
Aren’t in direct contact with blood vessels/nerves but get their nutrients through diffusion.
Describe the epithelial to mesenchymal transition during development.
Embryonic epithelia disassemble and move into the mesenchymal (connective) tissues; there they may migrate to other locations to form new epithelia, or transform into distinct non-epithelial cell lineages that give rise to other tissues.
Describe the cellular basis for apical‐basal polarity of epithelial cells and describe the functions of epithelial polarity.
Organelles are organized in a specific fashion and ion/molecular transporters are on specific cell surfaces with specific polarities. This leads to side-specific function of cells.
State the different cell junctions that connect epithelial cells to one another and to the basal lamina, and describe their key components and functions.
Tight junctions (zonula occludens): Provide a highly selective barrier between epithelial cells. Proteins: occludins and claudins.
Adherence junctions (zonula adherens): provide structural integrity to epithelial sheets and contribute to polarity and stem cell regulation. Proteins: cadherins - bind to intracellular actin.
Desmosomes (macula adherens): Promote mechanical strength and resist shearing forces and promote the structural organization of the epithelial sheet. Proteins: cadnherins - bind to intracellular intermediate filaments.
Gap junctions: Promote rapid communication between epithelial cells, through diffusion of ions and small molecules.
Describe epithelial classifications
Simple; stratified; pseudostratified; squamous; cuboidal; columnar; transitional
Simple epithelia: cells arranged in a single layer or sheet.
Stratified epithelia: more than one layer of cells in which cells of the outer layers do not directly contact the basal lamina.
Pseudostratified epithelia: special case where some cells do not reach the free surface (giving a stratified appearance), but all directly rest on the basal lamina.
Squamous cells are flattened cells,
cuboidal cells are cube-like,
columnar are taller than they are wide.
Stratified epithelia are named according to their outermost layer
Transitional epithelia (found around the bladder) are a special case: these epithelia are stratified, but when stretched change their shape from cuboidal to squamous, and appear to decrease the layering: this is indicative of a tightly adherent epithelium that is very resilient and stretchable.
State the types and functions of the different cell surface modifications on epithelial cells. (Apical/Basil-Lamina)
Apical
- Microvilli: increase surface area
- Cilia:
– Primary: function in cell communication
– Motile: function in moving media around passageways
– Sensory: function in sensory reception
Basolateral
- Infold and Outfolds: increase surface area.
Describe basal laminae by stating their basic components, their functions, the basis of their diversity, and their structural relationship to epithelia and other tissues.
Extracellular matrix: Formed by collagen and glycoproteins.
- Mediate attachment of epithelia to connective tissue.
- Contribute to selective filtration of substances
- Establishment and maintenance of epithelial cell polarity.
- Serve as specific “highways” for the migration of cells through connective tissue.
- Provide a barrier to movement of invading microbes or cancerous cell into other tissues.
- Control the gene expression of cells
- Control the development, morphogenesis, and organization of epithelial cells, providing a
sort of “tissue scaffolding” function.
Compare and contrast exocrine and endocrine glands in terms of their development, general structure, and functions; and for both types of glands, trace the path that a secreted molecule must take from its synthesis to its destination, and describe all the barriers/structures the molecule must cross en route.
Exocrine glands secrete materials onto the apical side of epithelial surfaces. Materials are either mucous, serous or mixed and secreted from apical side of cells.
Endocrine glands have no ducts and secrete substances to the blood stream. Hormones are secreted from basilar side of cells.
Describe the genetics and underlying protein defect in Cystic Fibrosis (CF).
CF is caused by a defect in an ATP-binding cassette transporter gene on chromosome 7 that encodes for the CF Transmembrane Conductance Regulator (CFTR) protein.
