unit 3 Flashcards
what are the types of microscope?
light, fluorescent, and electron
how does bright field microscopy work?
light rays emitted, condenser focuses rays onto a sample, light that is absorbed produces contrast, objective lens captures the rays
what is the product of bright field?
magnified version of sample
what is the limit of resolution?
the extent to which a microscope can distinguish fine details in the specimen as separate, distinct points
why is phase contrast used?
enables us to visualize unstained, live cells
how does phase contrast work?
shows difference in refractive index parts of cells as different areas of brightness and darkness
due to phase plate being between illumination source and condenser lens
why is dark field microscopy used?
to visualize small structures
how does dark field microscopy work?
an opaque disc is placed on the center of the condenser so light only passes around its edges which results in light scattering
what are the types of electron microscopes?
transmission (specimen must be thin) and scanning (3D)
what is the function of electron microscopy?
to increase the resolving power of the microscope
what is the purpose of atomic force microscopy?
to study surface topography at molecular and atomic resolution
what is immune staining?
the process of identifying proteins in tissue sections, incubating with antibodies specific to protein of interest, then visualizing the bound antibody using a chromogen
what are the steps for preparing tissues for microscopy?
fixation (usually with aldehydes)
dehydration (alcohol)
clearing (xylene)
embedding (paraffin)
sectioning
staining
what is the function of the cell membrane?
boundary and permeability barrier
organization and localization of function
transport process
signal detection
cell-to-cell communication
what is the fluid mosaic model?
describes the structure of the plasma membrane as a mosaic of components
has a phospholipid bilayer, with hydrophilic heads pointed out and hydrophobic tails away from the aqueous surface
are phospholipids amphipathic?
yes (hydrophobic and hydrophilic)
what regulates the rigidity of the membrane?
cholesterol
what does the outer leaflet of the lipid bilayer consist of?
phosphatidyl choline, sphingomyelin, and glycolipids
what does the inner leaflet of the lipid bilayer consist of?
aminophospholipids (phosphatidyl serine, ethanolamine, inositol)
what contributes a negative charge in the inner membrane?
phosphatidyl serine
what does protein kinase C bind to? when?
PKC binds to negatively charged phosphatidyl serine on the inner membrane when active
what is essential for PKC function?
negatively charged environment
what is phosphoinositol involved in?
signal transduction
what are the functions of membrane carbohydrates?
protection, lubrication, cell to cell recognition, adhesion
what is glycocalyx?
carbohydrate coat on the cell surface
what are some specializations of the plasma membrane?
microvilli, stereocilia
what are the two primary mechanisms for molecular transport across the membrane?
passive and active
what is endocytosis?
a process by which extracellular materials are captured and enclosed within membrane bound carriers that invaginate and pinch off cytoplasm from membrane
what is exocytosis?
process where intracellular molecules like hormones, antibodies etc contained within a membrane-bound vesicle discharged outside of a cell by fusion of vesicle with plasma membrane of a cell
endocytosis
what coated proteins are involved in endocytosis/exocytosis?
clathrin and caveolin
exocytosis
what are caveoli?
invaginations braced by the protein calveolin
what is potocytosis?
surface caveoli concentrate substances from the extracellular space and transport them into the cell
what is transcytosis?
caveoli are used to transport materials from the extracellular space on one side to extracellular space on the other side
general features of the nucleus
site within eukaryotic cell where chromosomes are localized and replicated
where DNA is selectively transcribed
what does the eukaryocyte do?
compartmentalizes activities of the cell’s genome, both replication and transcription, from the rest of the cellular metabolism
what does the nuclear envelope consist of?
inner and outer nuclear membrane, perinuclear space
how is the inner nuclear membrane supported?
by a rigid network of protein filaments attached to its inner surface called nuclear lamina
also contains specific laminate receipts that bind to chromosomes and secure attachment of the nuclear lamina
what is the perinuclear space filled with? what do its contents do?
filled with fluid, continuous with ER
protects and regulates the function of the genome
how is the nuclear pore formed? what is if lined with?
formed by the fusion of the two membranes of the nuclear envelope
lined with nuclear pore complex
what does the nuclear pore complex provide?
direct contact between the cytosol and nucleoplasm
what is the nuclear lamina?
a thin electron-dense protein layer which acts as a nucleoskeleton
what does the nuclear lamina do?
serves as a scaffolding for chromatin, chromatin-associated proteins, nuclear pore complex, and membrane of nuclear envelope
what are the two types of chromatin?
heterochromatin, euchromatin
what does each nucleosome consist of?
a histone octamer core and ~2 turns of DNA wound around it
what does the histone octamer contain?
2 H2A, 2 H2B, 2 H3, 2 H4 histones
where are nucleolus present?
eukaryotic nucleus
what is the nucleolus the site of?
ribosomal RNA synthesis and initial ribosomal assembly
what are the three distinct regions of the nucleolus?
fibrillar centers, fibrillar component, and granular component
what do fibrillar centers contain?
contain DNA loops of 5 different chromosomes that contain rRNA genes together with significant amounts of RNA polymerase I and transcription factor
what do fibrillar components contain?
ribosomal genes that are actively undergoing transcription accumulating large amounts of ribosomal RNA
what do granular centers represent?
the site of initial ribosomal assembly which contains densely packed pre ribosomal particles
how many membranes do mitochondria have?
2, inner and outer
what do the two mitochondrial membranes create?
the matrix and a narrow intermembrane space
what is the inner membrane of the mitochondria a location of?
electron transport protein complexes and ATP synthesis
what are the infoldings of the inner mitochondrial membrane called?
cristae, increase SA
what kind of DNA is found in the mitochondria?
double-stranded circular
the rough ER mainly synthesizes what?
protein
what will proteins synthesized in rER require?
sorting signals called signal sequences
the smooth ER mainly synthesizes what?
fatty acids and phospholipids
sER in liver
helps detoxify hydrophobic compounds like pesticides and carcinogens by chemically converting them into water-soluble products to be eliminated from the body
what does the sarcoplasmic reticulum do?
sequesters Ca++ that is essential for the contractile process
found in skeletal and cardiac muscle
what are polyribosomes? what do they do?
several ribosomes together, attach to a thread of mRNA
what is the Golgi complex the site of?
processing and packing ER products
glycosylation of proteins produced in the ER and their packaging
(located near nucleus, prominent in secretory cells)
primary lysosome
contains one or many enzymes
secondary lysosome
fusion with one or more primary lysosomes with phagocytized material
residual body lysosome
incomplete digestion by the lysosome (high numbers of residual bodies in Tay-Sachs)
why do nuclei stain dark in H&E stains?
nuclei are acidic in nature, so they bind with the basic hematoxylin
paneth cells vs RBCs
paneth cells contain acidic granules and therefore appear more granular
PAS staining
used to identify carbohydrates, carbs are stained bright pink
Feulgen staining
stains DNA magenta, specific for deoxyribose sugar
trichrome stain
nuclei - dark purple
cytoplasm - bright red
connective tisse - blue
immunohistochemistry
localizes specific antigens by exploiting the specific binding relationship between antibody and antigen in a tissue section
immunocytochemistry
localizes a specific antigen by way of specific antibody/antigen binding in a single layer of cells
what are the kinds of light microscope?
bright field, phase contrast, dark field
what is Zellweger syndrome?
a lethal condition caused by the defective assembly of peroxisomes due to the lack of transport of enzyme proteins into the peroxisome
