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91 Cards in this Set

  • Front
  • Back
eukaryotic cell consists of (4 things)
1. plasma or cell membrane
2. one or more nuclei, surr by nuc membrane which contains most of DNA
3. cytoplasm
4. basic set of organelles that form specialized compartments
ex of cytoplasmic struct that are not surr by a membrane
various cytoskeletal filaments, lipid droplets, or centrioles
advantages of specialized compartments
1) membranes surr them increase the cell surface and contain enzymes
2) compartment can have a unique composition of sp functions
3 maj mech by which cells move materials
1. mvmt across membrane (transmembrane transp)
2. gated transport
3. vesicular transport
mvmt across membrane --- small uncharged particles
simple diff
mvmt across membrane---- small water sol molecules move through membranes using
active or facilitated transp via carrier proteins or channels
mvmt across membrane---- proteins in process of synthesis
can move across cell membranes in special channels (ex membranes surr RER, perioxisomes, mitochon)
mvmt via vesicular transp --- uptake by vesicles into cell are by
endocytosis and phagocytosis
mvmt via vesicular transp --- sel transp of vesicles occurs when one memb fuse with another carrying cargo. this occurs in which pathways
biosynthetic secretory pathway and endycytic pathway
mvmt via vesicular transp--- 3 types of coated vesicles
1) clathrin coated vesicles: mvt into cell from plasma membrane and from golgi to cell surface
2) COPII coated vesicles mvmt of material from ER to and throuh the golgi memb
3) COPI coated vesicles: gen involved with retrieval of memb and contents (golgi back to ER)
mvmt via vesicular transp ---- pinocytotic vesicles are
clathrin independent
basic fcn of plasma membrane
1) selective barrier
2) formed by complex mix of lipids an dproteins
3) constant state of dynamic flux or can be tethered
4) 7.5 to 10 nm thickness
5) viewed in TEM
enzymatically active areaas of cell membrane contain higher proportion of
lipid rafts
enriched in cholesterol and sphingolipids and are less fluid than most plasma membranes
membranes under TEM, plasma membrane is resolved since
there is a deposition of osmium on hydrophillic groups of lipid bilayer that produces electron densities
plasma membrane has trilaminar appearance designated as a
unit membrane, outer electron dense layer and inner electron dense layer and intermed electron lucent layer
membrane proteins form about what percent of membrane mass and include what kind of proteins
50% of membrane mass and contain integral proteins and peripheral proteins
membranes demonstrate fluidity but also can be tethered which means they
do not move
both lipids and proteins have what on their extracell surfaces
oligosaccharide chains forming glycolipids and glycoproteins at surface that together form a glycocalyx that has an overall neg charge
integral membrane proteins are involved with what functions
transport (pumps and channels)
cell receptors, struct proteins, enzymes, molecules involved with cell adhesion
since many proteins and lipids can move within membrane, structure called tight junction exists where
at luminal border of adj epithelial cells (this tight junction is also called zonula occludens)
tight junction / zonula occludens function is to
limit the mvmt of proteins and lipids within memb to lateral surface or to apical surface so that diff surf of cell can contain diff molecules and therefore diff fcns
organelles: interphase nucleus
size and bounded by how many memb
6-10 micrometers dia, bounded by two unit membranes
functions of nucleus
protection, replication, synthesis, expression of genome
also synthesis of ribosomal components
dna is transcribed into
shape of nucleus and number per cell
differs in acc with the shape of cell, some cells contain more than one nucleus (hundreds in skeletal muscle)
nuclear envelope
comprised of two unit membranes continuous with each other at circ openings called nuc pores
perinuclear cisterna
space between two membranes in nuclear envelope
outer memb contain with RER, studded with ribosomes
nuclear envelope interrupted by
nuclear pore complexes, with 8 fold symm, gated ch for nuc
fibrous lamina
layer of intermed filaments, just inside inner membrane of nuc envelope
polypeptides called lamins A, B, C
when lamins are phosphorylated
the fibrious lamina and nuc envelope disassemble
nuclear envelope segregates the fcns of
nucleus and cytoplasm
in interphase, the chromatin adj to centromeres of chromosomes
is assoc with fibrous lamina
genetic material when not condensed to form chromosomes. fibrillar mass which fills most of nucleus.
chromatin appears .... when staining with basophilic dyes such as heterochromatin
appears densely staining when highly condensed and less active. when more actively transcribed, stains with less basophilia (euchromatin)
chromatin composed of
largely of coiled DNA protein complexes.
densely packed dark staining clumps of chromatin (heterochromatin) are
usually not capable of being expressed (transcribing RNA)
more loosely packed lighter staining chromatin (euchromatin) is
more actively expressed (capable of transcribing RNA)
2 meanings of chromosome
1) darkly stained rod like body during mitosis and meiosis. formed of condensed chromatin, allow genetic mat to be halved during mitosis
2) structure consisting of coiled strands of DNA bound to basic proteins which composed of genetic elements.
basic unit of chromosome
nucleosome: has core of 4 types of histones wrapped by DNA
nucleolus made of
dense aggregates of protein and nuc acid. may be more than one in nucleus. site of transcription of ribosomal DNA by RNA polymerase I and synthesis of 2 maj subunits of ribosome (ribosomal RNA)
nucleolus composed of three components:
1) nucleolar organizing DNA
2) nucleolonema with granular and fibrillar regions
-- pars fibrosa
-- pars granulosa
number and size of nucleoli related to
number of ribosomes produced and to protein synthetic activity of cell
polyribosomal proteins are synth in
then enter nucleus and assoc with ribosomes in nucleolus
nuclear matrix
comprised mainly of proteins and exists within the nucleus
functions of RNA (mRNA, tRNA, ribosomal RNA)
where are they synth
all synthesized in nucleus and assoc with proteins made in cytoplasm that have moved into nucleus. resulting subunits of ribosomes exit nuc through nuc pore
ribosomes are composed of two subunits:
large (60S) and small (40S) each is a complex of rRNA and proteins
protein or polypeptide synthesis is initiated when
small ribosomal subunit binds so mRNA and tRNA in cytoplasm. then large ribosomal subunit becomes attracted to complex
ribosomes play a key role in
translating the message carried by strand of mRNA
how many ribosomes can simult translate the same mRNA
several. since bound to same mRNA the ribosomes appear as whorls in electron micrographs called polysomes
accumulations of ribosomes are
basophilic (due to content of acidic phosphate groups)
stain hematoxylin indicating sites in cell involved with prot synth
proteins or polypeptides destined for use in cytoplasm
are synth on ribosomes that are free in cytoplasm
polypeptides destined for secretion to become enzymes in lysosomes or to become integral memb proteins
become bound to RER
RER is found as
a series of membrane limited flattened interconnecting cisternae with ribosome son cytoplasmic surfaces of the membranes
RER is prominant in cells that are
specialized for protein synth
invovled in synth of both proteins and lipids of many cell memb
RER synthesizes proteins that are not destined for use in cytoplasm, but for
a) secretion out of cell by exocytosis
b) to be inserted into other membrane bound organelles through vesicular transp to lysosome or endosome compartment
c) to form integral memb proteins
cells specialized for secretion will have: (4 things)
a) euchromatic nuclei
b) abundant RER
c) prominant golgi app
d) often will have dense membrane bounded secretory products
protein modification in RER include:
a) cleavage of signal sequences
b) initial core glycosylation of glycoproetins (addn of core mannose containing oligosacc)
c) post translational mod of protein
d) polypeptide folding
e) assembly of multichain proteins
proteins that are synth in RER move to
golgi via transport vesicles coated by coatamers
golgi app functions:
major site of carb synthesis and both cis and trans golgi networks are sorting stations for material moving within GA
golgi app also functions:
further modifies protein by glycosylation of proetins and lipids and phosphorylation or sulfation of glycoproteins
golgi app also brings about:
intracell sorting an dpackaging of proteins in memb bound vesicles
some ferried to endosomes some secreted directly
structure of golgi app
consists of a stack of 3-10 flattened membrane bound cisternae wtih dilated rims. assoc with small vesicles
golgi app freq resides near
nucleus and assoc with cell center inccluding microtubule organizing center and centrioles
regions of golgi app
cis golgi network (formgin face) region where transfer vesicels have budded from RER fuse wtih golgi membranes
sorting station
mvmt via vesicular transp ---- pinocytotic vesicles are
clathrin independent
basic fcn of plasma membrane
1) selective barrier
2) formed by complex mix of lipids an dproteins
3) constant state of dynamic flux or can be tethered
4) 7.5 to 10 nm thickness
5) viewed in TEM
enzymatically active areaas of cell membrane contain higher proportion of
lipid rafts
enriched in cholesterol and sphingolipids and are less fluid than most plasma membranes
membranes under TEM, plasma membrane is resolved since
there is a deposition of osmium on hydrophillic groups of lipid bilayer that produces electron densities
lysosomes are major
digestive organelles of the cell
contain hydrolases
lysosomes are how many unit membrane
prevents hydrolytic enzymes from digesting the cytoplasm
what kind of pH on lysosomes
low pH. created and maintained by membrane bound ATP driven proton pumps (exch Na+ for H+)
materials to be digested in lysosomes taken up by
endocytosis (also drinking by pinocytosis)
receptor mediated endocytosis, and phagocytosis or are formed by autophagy
proteosomes are
multi-hydrolase enzyme complexes that digest single cytoplasmic proteins that have been misfolded or are short term regulators
SER lacks what which is why it is called smooth
lacks ribosomes on surface
fcns of SER
synth of steroid hormones
detoxifies lipid sol drugs
synth phospholipids for cell memb
involved with glucose mobilization and storage
ca ion sequestration
can have high Ca conc in lumen
in sk and cardiac muscle: called sarcoplasmic retic
mitochon present in all cells except
mature RBC
structure of mitochon
flexible, mobile, self replicating (circlular dna and small ribosomes, most of proteins coded for by nuc DNA and made on cytoplasmic ribosomes)
fcns of mitochondria
pyruvate is conv to AChA, which enters Krebs cycle, oxidized into CO2 and reducing equiv
parts of cytoskeleton:
microtubules, microfilaments (actin filaments), intermediate filaments
microtubules are
unbranched tub structures, support force generating components
microfilaments (actin filaments)
inv with motility of cytoplasmic components and membrane proteins) prov force needed to divide cytoplasm into two during cyto kinesis
supportive meshwork
myosin is the
molec motor that moves actin filaments causing muscle contraction
intermediate filaments
neurofilaments in nerve cells, keratins in epithelial cells, vimentin related such as desmin in muscle, vimentin in fibroblasts and endothel, glial fibrillary acidic proteins in astrocytes, and nuclear lamins
cell junctions: 3 groups
occluding jcns, anchoring jcns, communicating jcns
occluding junctions function to
regulate flow of material from lumen/surface of epithelium to lateral intercell space bet epith cells (include zonula occludens)
anchoring junctions
provide adhesion bet cells
inc desmosome
communicating jcns (gap jcns) consist of patches of
specialeized memb proteins on two adj cell membranes containing transmemb channels or sm pores
connexons that permit diffusion
little elec resistance bet cells at gap jcns
connexons consist of
six integral mem proteins in circ arrangement called connexins
gap jcns occur between
epithelial cells and other such as cardiac muscle cells, bone cells, smooth muscle cells, and nerve cells