Cell Structure Overview Flashcards
What is eukaryotic cell composed of?
cytoplasm and nucleus
What is cytoplasm made of?
cytosol (cytoplasmic matrix) and organelles
What is in nucleus?
genetic info of cell
plasma membrane structure
dynamic, composed of phospholipids, cholesterol, and proteins
plasmalemma
external membrane of cell
glycocalyx
on external surface, layer of carb chains that are components of plasma membrane glycoproteins & glycolipids
glycocalyx appearance in TEM
fuzzy region on cell surface
glycocalyx functions
cell recognition & adhesion
T/F glycocalyx can be found in intracellular structures
F
intracellular membrane
surrounds nucleus & membrane-bound organelles
plasma membrane appearance under TEM
trilaminar structure with two electron-dense layers separated by a lighter layer.
The total thickness of the plasmamembrane
5-10 nm
modified fluid mosaic model
structure of plasma membrane as a two-dimensional lipid fluid with associated proteins.
where can membrane proteins move?
w/in plane of membrane
integral proteins and how are they visualized
directly incorporated within the lipid bilayer, Freeze fracture
peripheral proteins
weaker association with membrane
vesicular transport
only type of transport typically observed under a microscope
How are vesicles form?
from plasma membrane budding
endocytosis
vesicular transport of substances that enter the cell
pinocytosis
(‘cell drinking’) nonspecific ingestion of fluids via small vesicles (<150 nm).
receptor-mediated endocytosis
specific transport facilitated by binding extracellular molecules to their receptors concentrated cell surface
what happens once molecules bind to their receptors in receptor-mediated endocytosis
region becomescoated pit w/ clathrin molecules aggregating on cytoplasmic aspect plasma membrane, coated pit invaginates & forms coated vesicle
what does vesicle do once formed in receptor-mediated endocytosis?
pinches off from cell membrane, vesicles lose clathrin coat & fuse w early endosomes
early endosomes
vesicles observed in the vesicles in cytoplasm near the cell surface
phagocytosis
the ingestion of large particles such as bacteria, cell debris, or foreign materials.
most common phagocytic cells
macrophages and neutrophils
exocytosis
vesicular transport in which substances leave the cell where cell membrane stays intact
exocytosis steps
vesicle generated in cell fuses w/ plasma membrane & releases its contents into extracellular space
endoplasmic reticulum (ER) appearance in EM
3-dimensional network of intercommunicating channels and sacs that are formed by a continuous plasma membrane.
cisternae
spaces enclosed by ER often described as a system of flattened sacs
ribosome function
facilitate protein synthesis
what is RER continuous with?
outer membrane of the nuclear envelope
RER functions
. Synthesis of secretory proteins
. Synthesis of lysosomal enzymes
. Synthesis of integral plasma membrane proteins
. Initial glycosylation of glycoproteins
where is RER prominent?
cells specialized in protein export (antibody secreting plasma cells) & cells w/ large amounts of plasma membrane (e.g. neurons).
polysome
Multiple free ribosomes attached to a molecule of mRNA
free ribosomes synthesize proteins targeted to ____
nucleus, mitochondria, peroxisomes, or proteins that remain in the cytosol
what causes cytoplasmic basophilia?
Large amounts of free ribosomes and polysomes
Nissl bodies
In neurons large basophilic structures comprised of both RER and free ribosomes
smooth endoplasmic reticulum (SER) cisternae characteristics
tubular
SER appearance in EM
system of channels
SER functions
Lipid and lipoprotein synthesis (steroid-secreting cells)
. Plasma membrane formation and recycling
. Detoxification of lipid-soluble drugs & alcohol (hepatocytes)
. Carb metabolism (conversion of glycogen to glucose in hepatocytes)
5) stores and releases Ca ions
sarcoplasmic reticulum
SER in muscle cells
golgi apparatus appearance in EM
system of flattened sacs and cisternae, sometimes see small vesicles from intracellular transport associated w/ it
golgi functions
. post-translational modifications (glycosylation, sulfation, phosphorylation)
. sorting and packaging of proteins
cis/convex face in golgi
cisternae located closest to RER represent the forming side
trans/concave face in golgi
opposite side of the Golgi complex is the maturing side
medial golgi
cisternae located between the forming and maturing faces
vesicle movement with golgi
. vesicles budding from RER deliver newly synthesized proteins to cis- Golgi for further processing
. proteins travel in budding transporting vesicles w/in Golgi network in direction of trans-Golgi
negative golgi
in H&E preparations it appears as a clear area close to the nucleus
where is golgi well developed?
secretory cells
lysosomes
membrane-bound spherical bodies, filled with hydrolytic enzymes active in the low pH (4.5-5.0)
lysosome function
principal sites of intracellular digestion and are particularly prominent in phagocytic cells
what is unique about lysosome membrane?
most of its proteins are highly glycosylated & are resistant to hydrolysis by lysosomal enzymes.
where are lysosomal proteins synthesized and processed?
synthesized in the RER and modified in the Golgi
types of lysosomal digestion
micropinocytosis, endocytosis, autophagy, & digestion of phagocytosed material
micropinocytosis
. Digestion of microdroplets of fluids/ small particles attached to plasma membrane.
. Particles are transported via endosomal compartment & fuse w/ lysosomes for final degradation
lysosomal endocytosis digestion
endocytosed particles transported via endosomal compartment and fuse with lysosomes for degradation
phagosome
phagocytic cells that have digested extracellular particles
phagolysosome and what else is it called?
phagosome fuses with the lysosome (also known as a secondary lysosome)
autophagy
digestion of intracellular particles (proteins/organelles) which become enclosed by ER membranes and then fuse with lysosomes
where do contents of lysosomes go after digestion?
contents diffuse into the cytosol
residual bodies
Indigestible compounds retained in the cytoplasm
lipofuscin
age pigment, accumulated residual bodies observed in LM
mitochondria function
. transform chemical energy of metabolites present in cytoplasm into high-energy phosphate bonds in ATP molecules
. detecting cellular stress & initiation of apoptosis
when do mitochondria increase in number?
divisions during the interphase
where do mitochondria localize?
metabolically active areas of the cell
structure of mitochondrion
outer membrane, inner membrane w/ cristae, matrix inside inner membrane
what does cristae look like in steroid metabolic cells?
tubular
intermembrane space
space between mitochondrial membranes
what is mitochondrial outer membrane permeable to?
small metabolites and ions
T/F inner membrane space similar environment as cytosol
T
mitochondrial inner membrane protein functions
. oxidation reactions of respiratory ETC
. synthesis of ATP
. regulation of metabolite transport into & out of mitochondrial matrix
what is in mitochondrial matrix
enzymes of the citric acid cycle (Krebs cycle) and enzymes involved in fatty acid β-oxidation
how many proteins encoded in mitochondrial DNA?
13 proteins (subunits of protein complexes involved in ETC & oxidative phosphorylation
cardiolipin
ound only in the membrane of mitochondria. Several enzymes embedded in the mitochondrial membrane need cardiolipin to function
what occurs when autoimmune diseases build antibodies against cardiolipin?
severe cardiovascular and neurological symptoms (lupus and erythematosus)
peroxisomes characteristics
. Spherical organelles surrounded by a single membrane
. Self-replicating organelles w/ some precursor vesicles originating from the ER
peroxisome function
. Produce hydrogen peroxide (H2O2), which they employ for oxidative purposes
. Contain catalase (~40% of the peroxisomal protein) to destroy the excess of H2O2
what does H2O2 breakdown?
. fatty acids (β oxidation)
. toxins and prescription drugs, (detoxification of about half of consumed alcohol within the liver)
proxisomal disorder consequences
CNS malformations, myelin abnormalities, and neuronal degeneration, liver dysfunction & skeletal abnormalities.
cytoplasmic inclusions
. non-living elements of the cell
. Metabolic or endocytic products
. Membrane-bound (golgi products/endocytosis) or not membrane-bound
what are cytoplasmic inclusions made up of?
. storage products (e.g. glycogen, lipids)
. pigments (e.g. melanin, hemosiderin – breakdown product of hemoglobin)
. crystals
what percent of cellular membrane is in intracellular organelles?
95%
loss of ER function disorders
cystic fibrosis & COPD
cystic fibrosis
Lack of export of mutated Cl channel to the cell surface in lungs
chronic obstructive pulmonary disease (COPD)
Lack of secretion into the blood of mutated α1-antitrypsin by the liver
ER gain of function disorders
hepatic fibrosis and huntington’s
hepatic fibrosis
Accumulation of mutated α1-antitrypsin in the liver
huntington’s disease
excessive poly-glutamine sequence in huntingtin
what in golgi defines destination to organelles?
signal sequences
secretory lysosomes
Osteoclast, Melanocytes, NK & cytotoxic T cells
primary lysosomes
vesicle with enzymes but no material
secondary lysosomes
bound with something inside of lysosome
lysosomal storage diseases (LSD)
. Defective enzyme causes progressive accumulation of
partially degraded product
. 2/3 of LSDs affect nervous system
How many mitochondrial diseases are there and what are the most affected organs?
~50, brain and heart
What organelle is in charge of 80% of phospholipids of myelin in the brain?
Peroxisome
