Test 2 Lecture 34-35 Flashcards
Each organelle is surrounded by its own ___
membrane
These membranes divide the cell into ___ that have different internal environments specialized for different organelle functions.
compartments
Cells employ complex mechanisms to ___ molecules between compartments.
transport
which organelle is used for protein modification, sorting, and packaging for secretion or delivery to other organelles
golgi appartatus
Which organelle is used for protein synthesis and distribution, lipid synthesis
ER
endoplasmic reticulum
which organelle is used for degradation and recycling
lysosomes
which organelle is used for sorting of materials taken up from the extracellular environment
endosomes
which organelle is used for oxidation of toxic molecules
peroxisomes
three types of transport
gated transport
transmembrane transport
vesicular transport
___ involves binding of ____ on a protein with a translocator in the membrane to be crossed.
protein sorting through selective transport
sorting signals (signal sequences)
where does protein synthesis take place
on ribosomes, either free floating or attached to the endoplasmic reticulum.
in the cytoplasm
After synthesis in the ___, proteins get sorted and transported to their destinations in different intracellular compartments
cytoplasm
free floating ribosomes will produce proteins which will be transported to the
nucleus
mitochondria
chloroplasts
peroxisomes
ER bound ribosomes will produce protein that will ___
be transported to the plasma membrane
secretory vesicles
lysosomes
signal patch vs signal sequence
patch- several parts of protein have to come together to trigger signal that tells protein where to go
sequence- single part usually at end of protein that tells the protein where to go
Signal sequences are recognized by ____ receptors that guide proteins to their appropriate destinations.
complementary sorting
gated transport
transport of proteins into nucleus
nucleus has “nuclear pores”
karyopherins will release FG repeats (phenylalanine/glycine) these will bind to protein and transport through pore
nuclear transport receptors are known as
karyopherins
the fibrils of nuclear pores contain ___
phenylalanine/glycine repeats (FG repeats
Proteins synthesized on soluble ribosomes are targeted to ___ post- translationally
mitochondria
will form alpha helix with +, - (hydrophobic) and neutral charges on different sides
uses alot of ATP
two types of receptors in mitochondria
TOMs (translocators on the outer membrane)
TIMs (translocators on the inner membrane)
energy demanding process- uses alot of ATP
Peroxisomes contain ≥50 different enzymes involved in ____ reactions.
oxidative
Peroxisomes ___ various toxic molecules that enter the bloodstream, e.g., phenols, formic acid, formaldehyde, alcohol, acetaldehyde.
detoxify
Peroxisomes detoxify and are involved in ___ and breakdown of fatty acids
lipid synthesis
Proteins are recognized by ___ to come into the peroxisomes. Import is helped by ___
C-terminal import signal sequence: -Ser-Lys-Leu-COO-
import involves the activity of peroxins (soluble cytoplasmic proteins)
“empty” peroxisomes; hereditary disease
Zellweger syndrome
Zellweger syndrome
“empty” peroxisomes; hereditary disease
enlarged liver, high levels of iron and copper in the blood stream, and vision disturbances.
Symptoms at birth may include a lack of muscle tone, an inability to move and glaucoma. Other symptoms may include unusual facial characteristics, mental retardation, and seizures.
The ER is a network of membrane-bounded branching tubules that extends from the nuclear membrane throughout the cytoplasm, enclosed by a ___.
continuous membrane
The ___ is the largest organelle in most eukaryotic cells, enclosing ~10% of the cell volume.
endoplasmic reticulum
___ is a major site of protein synthesis:
ER
Protein synthesized on the ER will travel to :
ER
Golgi
Lysosomes
Plasma membrane
Secreted outside the cell
why are there so many ribosomes attached to ER
ribosomes produce protein, protein has ER signal sequence and binds to ER, as protein is made it is pushed into ER, holding ribosome in place
the same strand of mRNA can have many ribosomes coding for proteins at the same time
ER signal sequence is
20 amino acids long
hydrophobic residues
Peroxisome signal sequence
C-terminal import signal sequence: -Ser-Lys-Leu-COO-
import involves the activity of peroxins (soluble cytoplasmic proteins)
nucleus signal
+ charge
Nuclear localization signal -Pro-Pro-Lys-Lys-Lys-Arg-Lys-Va l -
explain ER transport
SRP binds to ER targeting signal of nascent peptide chains.
SRP (RNA protein complex)
SRP then drags the entire peptide with bound ribosomes- mRNA complex to the SRP recognition protein in the rough ER
this is close by to a protein translocator channel (hole), protein will go through hole as it is translated
SRP and SRP receptor are broken off once protein goes through channel
signal peptide is cleaved off by a specific signal peptidase.
Translation continues until the entire polypeptide is synthesized and the newly synthesized polypeptide resides in the lumen of ER.
In ER tranport, After the N-terminus of the nascent peptide enters the ER channel, peptide chain elongation continues and the signal peptide is cleaved off by a ____
specific signal peptidase.
Role of Stop Transfer signals in the generation of ___ proteins in the ER
transmembrane
protein starts synthesis into ER, then a stop transfer signal (mostly hydrophobic) will cause the protein to get stuck and rest of protein will translate into the cytoplasm
When sorting in the ER: Secreted or lumenal proteins are___, their signal peptides are cleaved, and the soluble proteins are released.
translocated,
when sorting proteins in the ER, Integral membrane proteins remain embedded in the ER membrane. Key is a ___ of hydrophobic amino acids
stop-transfer sequence
Proteins undergo specific modifications (____) in the ER as part of sorting and packaging for transport to their destination
glycosylation
what are two types of glycosylation
N linkage (asparagine)
O linkage (serine)
N linked glycosylation
happens to proteins in the ER- way of marking for transport
14 sugar residues is transferred to specific
asparagine residues in the growing polypeptide chain, while translation is still in
progress.
The recognition sequence for addition of N-linked sugars is Asn-X-Ser/Thr.
ER tranport disease
cystic fibrosis
cystic fibrosis
inherited disease
Involves accumulation of a slightly misfolded protein important for Cl- transport in the ER
lumen
Patients suffer from the formation of thick, sticky mucus lining the respiratory and gastrointestinal tracts. Symptoms in children and adults range from mild to severe
___ is delivery to the cell exterior of the macromolecules produced in the cell.
Secretory pathway (exocytosis)
___ is uptake of macromolecules and delivery of these molecules to lysosomes, which contain digestive enzymes.
Endocytic pathway (endocytosis):
basics of vesicle transport
donor compartment will bud off and transport to target compartment, the vesicle will bind/fuse with the target compartment and release its contents
Types of proteins that promote budding
COP
clathrin (endocytosis- outside to the golgi)
COPI (Golgi cisternae and out)
COPII (ER to golgi)
docking mechanism for vesciles
SNARE proteins
lives on outside and grabs floating vesicle with same piece, pull vesicle close enough that it will fuse with target compartment
to recycle snares lots of energy and adaptor proteins are needed
Golgi apparatus has a __ face, that is closer to the nucleus and a __ face that is farther away from the nucleus
cis
trans
The Golgi has a distinct morphology - flattened membrane-enclosed ___ or stacks.
cisternae,
Vesicles bud from the ER, and are then transported to the ___, where they fuse with the ___ membrane.
Golgi
Golgi
ER proteins are recognized by a ___ receptor in the Golgi, and are transported via vesicle exchange.
KDEL
As proteins move from the cis to the ___of golgi the proteins are changed/processed and sorted
trans cisterna
Three major pathways for proteins from trans golgi network:
trafficking to lysosomes
regulated secretion
bulk flow
Lysosomes
acidic (lower pH then rest of cell)- maintains low pH through hydrogen ATPase pumps- uses ATP to pump hydrogen into lysosome
acid hydrolases
contains transporters for final products of the digestion of macromolecules
stomachs of cell- breaks down unwanted stuff
three pathways of degradation in lysosomes
endocytosis- small particles
phagocytosis- big thing
autophagy- breakdown mitochondria
explain how lysosome is formed
hydrolase comes for ER to golgi
phosphate and sugar added (mannose 6- phosphate- M6P)
moved through golgi and binds to M6 receptor this triggers COT protein Clath to bind to outside of golgi, forcing it to bend and eventually bud off and transport to the late endosome
late endosome pumps H in and gathers lysosomal hydrolase until it gets enough and is a lysosome
disease caused by missing lysosomal enzymes responsible for the breakdown of glucosaminoglucans.
Hurler’s disease:
Hurler’s disease:
missing lysosomal enzymes responsible for the breakdown of glucosaminoglucans.
symptoms including grotesque skeletal and facial deformities, skin and cardiac changes, clouding of the cornea, and mental deficiency. Also known as gargoylism; lipochondrodystrophy.
disease from all the hydrolytic enzymes are missing from lysosomes because of a defect in GlcNAc phosphotransferase, which results in secretion of these enzymes out of the lysosomes.
Inclusion cell-disease (I-cell disease)
Inclusion cell-disease (I-cell disease)
all the hydrolytic enzymes are missing from lysosomes because of a defect in GlcNAc phosphotransferase, which results in secretion of these enzymes out of the lysosomes.
hydrolytic enzymes stuck in golgi, never make it to the lysosome
Onsets in early childhood with symptoms including gum hypertrophy, thoracic dysplasia, congenital hip dislocation, and mental retardation
___ is the uptake of macromolecules and particulates by the cell, and the trafficking of these from the plasma membrane to the lysosome.
Endocytosis
two types of endocytosis
pinocytosis (drinking) -uptake of fluids and solutes via small vesicles.
Phagocytosis (eating) involves the uptake of larger particles such as microorganisms.
Phagocytosis
involves the uptake of larger particles such as microorganisms.
can only be done by specialized cells such as macrophages, dendritic cells and neutrophils.
Involves activation of receptors on the surface of phagocytes
Pinocytosis
“drinking”
involves the uptake of fluids and solutes via small vesicles.
Most eukaryotic cells undergo continual pinocytosis
formation of clathrin-coated pits
Pinocytosis is a ___
Cells can ingest 100% of their plasma membrane in less than ___.
continuous process.
30 min.
Endocytosis through pinocytosis of membrane internalization must be balanced by addition of cell membrane by ___.
exocytosis
endocytic-exocytic cycle.
endocytosis through pinocytosis and exocytosis must be balanced and results in renewal of plasma membrane every 30 minutes
Receptor-Mediated Endocytosis
Macromolecules from the extracellular fluid bind to specific cell-surface receptors, and these receptor accumulate in coated pits. The molecule-receptor complexes enter the cell in clathrin-coated vesicles.
Use of a specific receptor allows the cell to increase the efficiency of ligand uptake more than 1,000-fold over fluid phase endocytosis.
More than 25 different receptors function in receptor- mediated endocytosis
explain LDL uptake into cell
LDL floats in ECM
LDL receptor on plasma membrane attaches to LDL
this attachment recruits adaptin and clathrin
more clathrin causes membrane to curve and eventually bud off into cell with help from dynamin
LDL will go to early endosome and be broken down by lysosomes
rececptor will be recycled and placed back onto membrane to capture more LDL
things go bad if receptor doesn’t work or too much LDL- LDL then floats in ECM and clumps together
___ is the major coating protein for the endocytic vesicles.
clathrin
what is the protein that helps bud off clathrin vesicles
dynamin
familial hypercholesterolemia
Endocytosis-related disease
Inability of LDL to bind its receptor
things go bad if receptor doesn’t work or too much LDL- LDL then floats in ECM and clumps together : formation of atherosclerotic plaques; heart disease
steps of secretory vesicles
golgi to outside
Aggregation/clumping of the secretory proteins mediated by signaling patches.
Budding of the secretory vesicles from the TGN.
Concentration of the contents of secretory vesicles through membrane recycling
formation of synaptic vesicles in neurons
Cystic fibrosis:
Inherited disease
Involves accumulation in the ER of a protein important for Cl- transport that is slightly misfolded
Clinical manifestation: formation of thick sticky mucus lining the respiratory and gastrointestinal tracts
Lysosomal storage diseases:
The I-cell disease: missorting of lysosomal hydrolases to the plasma membrane due to a loss in the activity of a transferase responsible for the synthesis of Mannose-6-phosphate tag; substrates of hydrolases accumulate in lysosomes. Results in the pathological consequences in the nervous system
Hurler’s disease; defect in lysosomal hydrolases
The I-cell disease:
The I-cell disease: missorting of lysosomal hydrolases to the plasma membrane due to a loss in the activity of a transferase responsible for the synthesis of Mannose-6-phosphate tag; substrates of hydrolases accumulate in lysosomes. Results in the pathological consequences in the nervous system
Hurler’s disease
defect in lysosomal hydrolases
hydrolase does not make it out of golgi to the lysosome
Lysosomal storage diseases:
Zellweger syndrome:
“empty” peroxisomes; abnormalities in brain, liver, kidneys
