Cell Anatomy Flashcards
Cell anatomy
look at appearance position of various parts materials that comprise each part, and their location; constituents and apperance, blue print of cell how to fit things together inside/ how do things move around cell
Overview of cell anatomy
- How to visualize internal structure (fluorescent-based microscopy techniques) and electron microscopy
- What structures exist within a cell
- organells
- cytoskeleton (filaments and associated proteins)
To visualize internal structures of cells
problems: cells and their constituets are small and colorless
solution:
- need something that can resolve structures (<10um)
-means to provide contrast and make structure visible
light microscopy
relies on glass lenses and light, resolution of ~.2um; can do live or fixed cells, straightforward prep, cheap, non-destructive to cells
Electron microscopy
relies on electron beams and electromagnets as lenses; resolution of less than ~.1nm; more expensive, prep takes longer and is more in depth, destructive to cells, cells must be fixed to do this; bombard cells with electrons
resoluotion
minimal distance required for two individual objects to be separated in order to be discerned as independent entities
Fluorescent based probes
use of fluorescent based probes allows you to to stain and visualize contents within the cell can light up intraceullar components; can use dyes that are going to go to certain organelle to visualize them; detection requires light microscope with filters designed to detect light emitted from fluorescent compound
GFP (green flourescent protein)
protein that is fluorescent used to tag and visualize celluar components; GFP is intrinsically fluorescent there is a variety of colors you can use
immunofluoresence
proteins inside cell are visualized using antibodies and fluorescence; antibodies added to cells after cells are fixed
immunofluorescence steps
- Antigen (your protein in the cell); detected with primary antibody
- secondary antibody (recognizes all antibodies of primary antibody species), fused to a flourecent marker is added
- flourescence emitted is detected using fluorescent microscope
how to test for lupis
- add patient sample to liver cells primary antibody will bind nuclear protein (antigen) in liver cells
- add fluorescent secondary antibody
- Image with fluorescent microscope
other uses for GFP
can make glow in the dark fish
Transmission electron microscopy
similar to light microscope but similar; stained with electron dense material where stain is most dense get black spot
Scanning electron microscopy
smaller simpler and cheaper than TM and lower resolution; samples coated with electron dense heavy metals; image is 3-D
Electron microscopy in clinic
useful for identifying virus based on distinct morphology of viral families
organelles
specialized subunits within a cell that has a specific function usually enclosed within its own lipid bilayer
proteasome
large protein complex that is considered an organel
organelles overview
- Manufacture
- Nucleus
- ER
- Golgi apparatus - Breakdown
- proteasome
- lysosome
- Peroxisome - Energy Processing
- Mitochondria
eukaryotic organelles
all eukaryotic cells have same basic set of organelles; structure and function for organelles conserved between species; organelles can varry in abundance btwn cell types
nucleus structural features
round or elliptical in shape; envelope in double membrane continuous with ER; membrane has nuclear pores to facilitate entry and exit of protein and nucleic acid; contiguous with ER
nucleus function
control center of cell; principal site of DNA and RNA synthesis; site of ribosomal RNA (rRNA) synthesis; contain one or more darkly stained bodies nucleoli
Endoplasmic reticulum structural features
membrane network that extends from nucleus throughout the cell; contains 2 subdomains (rough ER associated with ribosomes and smooth ER ribosome free)
Endoplasmic reticulum functional features
role in lipid (SER) and protein (RER) biosynthesis; storage site for calcium; initial site of protein glycosylation
ER reticulum system
part of exocytic (secretory) pathway (1st part)
Golgi apparatus structural features
stack of disc-like compartment (cisternae); stack has polarity
- cis face closest to ER
- trans face farthest from ER
Golgi apparatus functional features
- major site of protein sorting and modifications
- receives protein and lipids from ER and dispatches them to various destination
- site of extensive protein glycosylation
Golgi apparatus system features
part of exocytic secretory pathway
Proteasome structural features
protein complex, not membrane bound, found in cytoplasm and nucleus
Proteasome functional features
- degrades cellular proteins that do not properly fold in cytoplasm and ER
- degrades foreign proteins in the cytoplasm (eg viral proteins)
ubiquitin
tags protein for degradation via covalent linkage
Breakdown proteasome
Ub tagging catalyzed by series of enzymes in 3 steps
- ATP- dependent conjugation of Ub to an Ub-activating enzyme (E1)
- Transfer of activated Ub to an Ub conjugating enzyme (E2)
- Transfer of Ub from E2 to target protein by Ub protein ligase (E3)
velecade
multiple myeloma drug that targets proteosome
Lysosomes structural features
membrane bound spheres, filled with enzymes (hydrolyses)
lysosomes functional features
- digestion of nucleic acids, proteins, and lipids
- contents come to lysosome via endocytosis, autophagy, and phagocytosis
- contents come to lysosome via collection of membrane-bound organelles called endosomes
lysosomes system features
part of endocytic pathway (break things down from outside cell)
Peroxisomes structural features
- membrane bound spheres
- contain enzymes involved in various oxidative reactions
peroxisomes functional features
- site of oxidative metabolism
- breakdown of fatty acids to produce acetyl Co-A
- convert free radicles to peroxide
- convert peroxide to water
mitochondria strucutre
double membrane structure inner and outer membrane form folds called cristae, contain their own genome
mitochondria function
- powerhouse of cell
- Provides energy (ATP) for cell via oxidative metabolism
organelle failure
can lead to loss of cell fx; disruption of delivery of one or more proteins to a given organelle can disrupt organelle activity and cause disease pathology
lysosomal storage disease
disruption to variety of lysosomal protein hydrolyses leading to inability to breakdown proteins/ lipids/ carbs dogs with mucopolysacharidosis VII are missing a lysosomal hydrolase that normally breaks down complex carbs; dogs develop paralysis have heart joint and eye abnormalities
Tay-Sachs
example of lysosomal storage disease; deficiency in lysosomal enzyme hexosaminaside A leads to harmful lipid accumulations in nerve cells and brain; naturally occurring in Jacob’s sheep
organelle size and shape clinically
can be used to monitor disease Cancer halmarks - enlarged nucleus - irregular nuclear contour - altered chromatin content
cytoskeleton
system of protein filaments in cytoplasm of eukaryotic cell that gives cell its shape and capacity for directed movement “skeleton of cell”; can form stable structures and can be dynamic and adaptable; related to shape, support, and locomotion
cytoskeleton: Major concepts
3 major types protein filaments: microtubules, actin filaments, intermediate filaments; filaments share certain fundamental principles; each type has distinct mechanical properties, dynamic and biological roles
cytoskeleton general properties
self-assemble from small diffusible subunits making rapid assembly and disassembly possible; held together by weak non-covalent interactions; consist of multiple protofilaments that associate laterally with each other; filaments combine strength and adaptability
subunit removal cytoskelton
easy to remove from ends (dynamic) hard to remove from middle (stable)
accessory proteins and cytoskeleton
regulate assembly of new filaments and partitioning btwn filament and subunit form; accessory proteins respond to extracellular and intracellular signals to regulate cytoskeletal behavior and function; important accessory protein = motor
Microfilaments
composed of globular actin filaments; actin monomers bind ATP; actin monomers assemble to form a filament; form R handed helix; grows from + end; fairly bendable given more tensile strength via accessory proteins; located near cell periphery can run length of cell; forms rigid gels, networks, and linear bundles; tracks for myosin;
microfilament function
determine shape of cell surface and facilitate whole cell locomotion ; cellular protrusion; focal adhesions
actin filament
= microfilament
microcillament locomotion
adding things to plus end push out cell and allow for crawling of leading edge
lysteria and Rickettsia
coopt bacteria cellular actin to propell themselves within and between cells
Microtubules
composed of: tubulin which binds to GTP; alpha and beta tubulin monomers form tubulin heterodimers; protofilament composed of alternating alpha and beta tubulin
- cylinder long and hollow with 13 protofilaments building MT cylinder; MT subunits have polarity growing at plus end, protofilaments are parallel
- very stiff and hard to bend bc multiple contacts in MT lattice
- polarization
- tracks for kinesin and dyneins
microtubules localization
Nucleation occurs at microtubule organizing center
- MTOC anchors and protects minus end
- MTOC= centrosome is near nucleus, Mts eminent from MTOC forming star like conformation
microtubule function
determine positions of membrane enclosed organelles and direct intracellular transport
- organelle localization
- intracellular transport
- establishes cell polarity
- meiotic and mitotic spindle
Intermediate filaments
- heterogenous family of rope like filaments
- assembled from distinct subunits (keratins, neurofilaments, vimiten like proteins, lamins; do not contain an associated nucleotide; non-polar; easily bend hard to break; no nucleotide; great tensile strength; unpolarized; no motors
intermediate filament structure
elongated alpha-helical monomeric subunits dimerize and associate to form staggered tetrameric subunits;
protofilament
formed by packing together of tetramers
filament
formed from 8 parallel protofilaments
intermediate filament function
provide strength to tissues for squishy animals; prominent in cells prone to mechanical stress; provide mechanical strength, provide shape to cells and help to resist pulling forces; mechanical strength, intracellular scaffold, cell-cell junctions
keratins provide strength to
hooves, nails, hair, claws, scales
destruction of lamins in nucleus
causes severe disorders bc lamins give shape to nucleus
Accessory proteins
bind to filaments or subunits to control filament behavior (cross link, cap, nucleate things, sever filaments, ect) and organization; generally associated with microtubules and microfilaments intermediate filaments have things that can crosslink and bundle things but they aren’t called accessory proteins
Motor proteins
- type of accessory protein they bind to cytoskeleton
- funciton to move molecules and membrane enclosed organelles throughout cell
- generate force required to move filaments themselves (muscle contraction, cilliary beating, cell division)
What do molecular motor proteins do
convert energy from ATP hydrolysis into mechanical force to walk along MF and MT filaments
myosin
motor protein family; associated with actin (microfilaments), walks toward + direction
kinesin
motor protein family; associated with microtubules; walks toward + direction
dynein
motor protein family; associated with microtubules; walks toward - direction
motor proteins tructure
have head, stalk, and tail
- Head binds and hydrolyzes ATP
- tail region contains binding site for cargo
kinesin structure
two globular head domains, elongate stalk and tail
dynein stucture
these are largest and fastest; formed from two or three main proteins plus variable number of associated polypeptides
kinesin movement
binding and hydrolysis of ATP by head domains changes the conformation of the protein allowing it to walk or step down MT toward plus end
dynein movement
nucleotide hydrolysis is coupled also to MT binding and unbinding as well as force generated conformational change; power stroke is driven by binding and hydrolysis of ATP causing motor heads to rotate relative to tails generating step along MT toward minus end
kinesin function
brings cargo to periphery of cell; function in organelle positioning, axonal transport, mitosis (move toward synaptic terminal)
dynein funcion
bring cargo to center of cell; function in cilia/ flagella beating, vesicle transport, mitosis (move back toward cell body)
canine x linked muscular dystrophy
mutation in actin binding accessory protein dystrophin, leads to degeneration of muscle fibers progressive weakness and premature death; present with high levels of creatin kinase bc muscle damage
MT disrupting dogs being used
to treat mast cell tumors in dogs (paclitaxel) and as combo with chemo in lymphoma (vincristine); these drugs kill dividing cells bc MT assembly and disassembly critical for correct cell division
epidermolysis bullosa simplex
mutation in intermediate filament protein keratin; characterized by weakness, skin inflammation, blistering, hair loss
coat variations
due to mutations in keratin (partially not entirely); responsible for variations in color and in texture
filaments are
dynamic, adaptable, can form stable structures, accessory proteins regulate the assembly of filaments and come in many flavors; disruption of cytoskeletal elements associated with variety of disease pathologies
motor protein functoins
move molecules and membrane enclosed organelles throughout the cell; motors bind to filaments throughout head region; motors powered by ATP binding and hydrolysis; 3 major classes Myosin, Kinesin, Dynein
