Histology 1 & 2 Flashcards
Name the 3 phospholipids on the P-face of the lipid bi-layer and their general functions
Phosphatidylserine- apoptosis, coagulation
Phosphatidylethanolamine- particularly present in nervous tissue, cell division
Phosphotidylinositol- signaling, membrane trafficking
Name the 2 phospholipids found of the E-face of the lipid bilayer of the plasma membrane
Phosphatidylcholine- signaling
Sphingomyelin- myelin sheath
What is the name of the coating formed when polysaccharides extend from integral proteins of the plasma membrane?
Glycocalyx
Describe the anatomy of a lipid raft
Micro domain in the plasma membrane: group of integral (and peripheral?) proteins surrounded by a high concentration of glycosphingolipids and cholesterol
Describe the difference between COP-II and COP-I
COP-II coats vesicles carrying proteins from the RER to the Golgi apparatus where they are modified then carried in vesicles from the trans-golgi network to the plasma membrane
COP-I vesicles carry stuff retrograde from the Golgi apparatus back to the RER
Constitutive pathway
Proteins leave the cell immediately after synthesis in vesicle but with no secretory products
Regulated Secretory Pathway
Protein secretion that is regulated by hormonal or neural stimuli. The proteins have to be transiently stored in vesicles within the cytoplasm.
Describe the two types of phagocytosis (antibody vs non-antibody)
What does it mean that both are actin dependent?
Are they Clathrin dependent?
Antibody mediated phagocytosis is for uptake and disposal of biological materials (such as bacteria) to which antibodies attach
Non-antibody uptake still uses receptors on the cell surface but is for non-biological materials (like carbon inhalation)
Actin rearranges itself to the cell surface in order to project the cell membrane around the particle needing to be phagocytosed
No
Describe the process of Clarthin dependent endocytosis
A cargo protein fuses with a cargo receptor which is then recognized by adaptin. Clarthin recognizes the adaptin and forms a coated pit which is then pinched off by dynamin and taken into the cell. The Clarthin dissociates and the vesicle fuses with an endosome
Pinocytosis
“Cell drinking”; small invaginations of extracellular fluid and anything that is soluble. These vesicles eventually fuse with lysosomes.
Describe the following signaling types: Endocrine Paracrine Synaptic Autocrine Juxtacrine
Endocrine- hormones are carried in the blood to their target cells
Paracrine- signaling molecule travels in extracellular fluid to a nearby cell
Synaptic- special type of paracrine; uses neurotransmitters in a synapse
Autocrine- signal molecules bind to receptors on the same cell
Juxtacrine- signaling molecules are bound to their parent cell and interact with an adjacent cell
Enzymatic receptor
A ligand binds to activate usually a protein kinase which then phosphorylates another enzyme
Channel linked receptors
Ligand binds to open up a channel that then lets certain ions into the cell
G-protein coupled receptor
A ligand binds which causes a conformation change of a G-subunit allowing GTP to bind said protein. The G subunit leaves its receptor home to then bind other proteins such as adenyl cyclase or an ion channel which triggers secondary messengers to turn on protein kinase enzymes which phosphorylate other enzymes.
Describe the difference between hydrophilic signaling molecules and hydrophobic signaling molecules
Hydrophilic- polypeptide hormones and neurotransmitters. Bind to receptors on the CELL SURFACE
Hydrophobic- steroids and thyroid hormones which can pass straight through the lipid bilayer to then bind a receptor on the nucleus (which allows it to pass into the nucleus and bind to DNA)
What is spingomyelinase? What can a deficiency in this enzyme cause?
Breaks down excess sphingomyelin (myelin sheaths). A deficiency can cause excess sphingomyelin to build up inside lysosomes and causes enlarged cells in the spleen, liver, lungs, bone marrow, and brain. Type A involves an enlarged liver and jaundice in infants. Type B exhibits an enlarged spleen and liver and usually is found in preteens.
Describe the mechanism of Multiple Sclerosis
Upregulation of certain cytokines from CSF (like tumor necrosis factor alpha) causes overactivation of sphingomyelinase resulting in degradation of sphingomyelin
Describe what an acanthocyte looks like. What causes this shape?
Spikey cell. Abetalipoproteinemia causes an excess of sphingomyelin on the outer leaflet of red blood cell membranes.
Describe Cystic Fibrosis
A mutated gene codes for a CFTR protein (which isn’t normal). This protein is a transmembrane chloride channel that doesn’t actually let chloride through. Usually, the negative charge from chloride ions draws Na+ out of the cell allowing H2O to follow thus washing away excess mucus
Cystinuria
Normally a carrier protein takes cysteine out of the urine. When a mutation is inherited (both parents), recurrent kidney stones can occur.
Describe epithelial tissue
Protective layer that covers surfaces of the body and lines ducts and tubes that communicate with the exterior. These cells are close together
Describe connective tissue
Serves to support and strengthen. Cells are spread apart and the tissues are mainly held together by the intercellular matrix
Which are more numerous in the CNS, glial cells or neurons? Which has the larger cell body?
Glial
Neuron
Fixation
Small pieces of tissue are placed in solutions of chemicals that cross link proteins and inactivate degradative enzymes
How is dehydration accomplished?
After fixation, the section is immersed in increasing concentrations of alcohol
Clearing
A section is placed in a liquid miscible with both paraffin and alcohol. The resulting section is transparent
Name the three steps that occur after clearing
Infiltration, Embedding, and Trimming
Does collagen stain pink or blue in an H&E stain? Cartilage? What does this mean about the two?
Pink. This means that collagen is basic or acidophilic.
Cartilage stains blue which means it is acidic, anionic, or basophilic.
Describe the function of the Smooth Endoplasmic Reticulum. What does it synthesize? What is its role in detoxification and metabolism?
The smooth ER does not have ribosomes because its job is to synthesize non-protein substances such as lipids and steroid hormones (in the endocrine cells of the gonads and adrenal cortex). Cytochrome P450 is found in the SER of liver cells and is involved in the detoxification of metabolic waste products, drugs, alcohol, and other organic substances. The outer membrane of SER also contains enzymes that participate in the release of glucose from glycogen in the liver (metabolism)
Where is Ca2+ stored in muscle cells?
Smooth ER
What can be found in the cytosol/cytoplasm of a cell?
Membranous and non-membranous organelles, enzymes, oxygen, carbon dioxide, low-weight molecular substrates, metabolites, and waste products.
What would a cytoplasm that stains intensely with hematoxylin indicate?
The presence of active protein synthesis (high concentration of basophilic ribosomes)
Which types of proteins are synthesized by cytosolic ribosomes? Which are synthesized by ER bound ribosomes?
Intracellular proteins: cytosolic, mitochondria, peroxisomes, nucleus
Extracellular proteins: go first to Golgi apparatus, then are secreted in vesicles, incorporated into the membrane, or go to lysosomes
How does the SER work to detoxify the body?
The SER of liver cells has enzymes that work with cytochrome P450 to turn toxic agents into water soluble molecules that can be excreted
What types of organelles will be in large concentration in a cell that secretes steroids? What about pancreatic cells?
Smooth ER because it makes lipids and steroids
RER and Golgi because pancreatic cells are secretory cells
Describe sickle cell anemia
A point mutation in which valine replaces glutamine in the B chain of hemoglobin. The result is a blood cell that looks like a sickle
What happens if an amino acid mutation renders the RER unable to export a1-antitrypsin (A1AT)?
Emphysema
Chemiosmotic Coupling
Movement of protons down the concentration gradient(/electrical gradient) back into the mitochondrial matrix
ATP/ADP exchange protein and the Voltage Dependent Anion Channel
Exchanges ADP and ATP across inner membrane
Exchanges ADP and ATP across outer membrane
What is MERRF? What is the mechanism?
Myoclonic epilepsy with ragged red fibers. It affects muscle cells. A mutation of mitochondrial DNA that codes for the tRNA of lysine causes malformation of two ETC complexes.
What happens to denatured or misfolded proteins within the cell?
They conjugate with ubiquinone and are destroyed by proteosomes
What does it mean that secretory cells are polarized?
The cell has different structures in different parts. For example, a pancreatic acinar cell has RER on the basilar end and secretory vesicles on the apical end that go out towards the lumen of the gland
Cells with great phagocytic activity (macrophages, neutrophils) are rich in which type of organelle?
Lysosomes
Heterolysosome
A lysosome that is actively digesting stuff. The broken down nutrients get released back into the cell
ATPase
Enzyme found in proteosomes that denatures proteins bound to ubiquitin
What is the role of the mitochondria in apoptosis?
The mitochondria releases cytochrome c into the cytoplasm which triggers certain proteases to initiate apoptosis
What happens to the mitochondria when a cell undergoes mitosis?
Each new daughter cell gets half a mitochondria
Which types of cells might have a large amount of peroxisomes?
Liver and kidney cells (for breaking down harmful ingested substances)
What is the mechanism of peroxisomal digestion?
Oxidases make hydrogen peroxide out of a substrate and proteases (like catalase) immediately break it down
Where do lysosomes originate from? What about peroxisomes?
Lysosomes originate from the Golgi appartus. Peroxisomes originate from the ER and other peroxisomes
Where do lipid and glycogen metabolic enzymes come from?
Smooth ER
Tay Sachs disease
Lysosomal storage disorder (LSD) in which hexoaminidase A is deficient causing build up of GM-2 gangliosides in neurons (the result is a vegetative state)
Zellweger syndrome
Peroxisomal disorder where the proper enzymes for B oxidation cannot be incorporated because the target signal receptor (in the peroxisome) is absent. The result is lack of plasmalogen production which is the most abundant phospholipid in myelin. Nervous system is affected and it is fatal
What are inclusions?
Cytoplasmic structures or deposits that store macromolecules usually not bound by a membrane (lipid droplets form a single layer phospholipid membrane)
Cells with high metabolic activity are rich in which type of inclusion molecules?
Glycogen granules
What is lipofuscin? What does it look like? How is it different from melanin?
Lipofuscin appears as yellowish brown pigments and accumulates in long-lived cells (cardiac cells, neurons). They are membrane bound remnants of lysosomal byproducts that were not digestible. Melanin is a type of pigment deposit manufactured by melanocytes and pigment cells. It has a protective function.
Hemosiderin
Type of pigment deposit; iron-storage complex thought to be the remnants of degraded hemoglobin when an erythrocyte has been phagocytosed such as in the spleen to by a macrophage in the lungs. It appears brown in light microscopy just like lipofuscin
True or false: centrioles replicate during cell division
True
What is an Axoneme?
Makes of cilia and flagella. 9 microtubule doublets form a circle around a pair of 2 central microtubules. Dynein arms projects from one doublet to the adjacent doublet. The rhythmic grab and release of dynein arms causes motion
Tubulin is the building protein for which type of cell filament?
Microtubules
What is the main role of intermediate filaments?
Provide mechanical strength and resist shear stress (in epithelial cells, the intermediate filaments extend between cytoplasms of adjacent cells for increased rigidity)
Name the location of intermediate filaments composed of the following polypeptides: lamins A, B, & C, vimentin, desmin, glial fibrillary acidic protein, peripherin. What about type I keratins (acidic) or type II keratins (basic)? Neurofilament proteins?
Nuclear lamina (inner lining of nuclear envelope), many cells of mesenchymal origin, muscles cells, glial cells (astrocytes and Schwann cells), some neurons
Both types found in epithelial cells and their derivatives (hair and nails, etc.)
Neurons; axonal intermediate filaments
Which of the three cytoskeletal fibers are polar?
Microtubules and microfilaments (actin). Intermediate filaments are not
Compare and contrast the location, general structure, and function of the three types of cytoskeletal fibers.
Microtubules- radiating from centrosomes and in axonemes. One microtubule made of 13 protofilaments (made of tubulin which is an a & b dimer). Help maintain cell shape and polarity. Provide tracks for organelle movement. Move cilia and flagella
Microfilaments- made of a helical strand of two F-actin filaments (made of G-actin subunits). Concentrated beneath the cell membrane (inner surface) and in microvilli. Help change the shape of the cell membrane and link epithelial cells together. Help move cells.
Intermediate filaments- antiparallel tetramers of two rod like dimers. Found webbed throughout the cell especially at desmosomes and inside the nuclear envelope. Help maintain cell shape and hold desmosomes together.
Which tubulin subunit is the (+) end and which is the (-) end?
B is (+) and a is (-)
Dyneins and Kinesins are classified as which type of macromolecule? What is their driving force?
Which goes from + to -?
Molecular motor proteins. ATP driven.
Dyneins go from + to - and Kinesins go from - to +
What is a centriole? What is a centrosome? What happens during mitosis?
Centriole is a set of nine microtubule triplets (27 total). A centrosome is two perpendicular centrioles (usually near the nucleus). Before mitosis, the centrosome duplicates and the two move to opposite ends of the dividing cell
Where are primary cilia found?
On virtually every cell. They have a 9+0 arrangement with no dyneins and don’t do any motion
What is the role of protein bridges in axonemes?
They hold the A tubule to the adjacent B tubule and restrict the movement caused by dyneins (which actually produces the back and forth motion)
What are filamin, spectrin, fimbrin, and fascin?
Filamin and spectrin are microfilament linking proteins that help arrange actin into a stiff, cross-linked meshwork that lines the plasma membrane of cells and resists sudden forces (spectrin is known in erythrocytes). Fimbrin and fascin are actin-binding proteins found in microvilli extensions.
What is the aggresomal response?
That’s when intermediate filaments aggregate around damaged cell components. After the components have been eliminated, the meshwork re-expands
Kartagener’s syndrome
Defects in microtubules and microtubule proteins which can affect the respiratory system and the reproductive system
What do colchicine, vinblastine, and vincristine have in common?
They all stop the microtubule function (polymerization or mytotic spindle formation) to arrest inappropriate cell functioning.