Lecture 14 - Peroxisomes, Mitochondria, Chloroplasts & Nucleus Flashcards
_____ _______ _______ allows polypeptide to enter organelles after they’ve been synthesized
post-translational import
where are proteins destined for peroxisome, mitcohondrion, chloroplast or nuclear interior synthesized?
on free ribosomes and released into the cytosol
in the rough ER, proteins that are imported by organelles need what?
- a sorting signal (amino acid sequence)
- a receptor (recognizes the sorting signal, and transports the protein to the membrane)
- a membrane transporter (facilitates passaged into the organelle, through the bilayer
def: spherical organelles, defining characteristic is the presence of catalase, H2O2 metabolism
perioxisome
what are the essential roles of peroxisomes?
- H2O2 metabolism
- detoxification of harmful compounds
- oxidation of fatty acids
- metabolism of nitrogen-containing compounds
- catabolism of unusual substances
def: enzymes that degrade H2O2 into water and oxygen
catalases
def: enzymes that oxidize organic substances and produce H2O2 in the process
oxidases
membrane lipids are either synthesized by ________ ______ or transported there by ______ _____ ______
peroxisomal enzymes, lipid transfer proteins
where are most peroxisomal proteins are synthesized and then translated?
on free cytosolic ribosomes, the post-translationally imported via a C-terminal peroxisomal target signal (PTS-1)
def: in mitochondria, contains porins, which allow free movement of small molecules and ions across the outer membrane
outer membrane
def: in mitochondria, acts as a permeability barrier to most solutes
inner membrane
def: within the inner membrane; contains most of the enzymes associated with mitochondria function, in addition to DNA and ribosomes
matrix
def: area between the outer and inner membranes
inter membrane space
def: localized regions where protons can accumulate during the electron transport process
intracistal space
where are most mitochondrial and polypeptides synthesized
on cytoplasmic ribosome
what kind of molecules can pass through the porins in the outer membrane of mitochondria?
ATP, ADP
CoA, NAD
ions
what is the DNA composition of mitochondrial proteins?
99% nuclear genes
1% mitochondrial genome
where are most of the mitochondrial proteins found?
mitochondrial matrix or inner mitochondrial membrane
what state are the proteins that enter the mitochondria
unfolded state and contain a pre sequence or “internal targeting sequence”
where does translocation occur simultaneously in the mitochondria?
where the inner and outer membrane are close together
what are TOMs
Translocase of the Outer Mitochondrial Membrane
what are TIMs
Translocase of the Inner Mitochondrial Membrane
how are cytosolic proteins kept in an unfolded state?
bound by molecular chaperones
__________ encoded by an N-terminal alpha-helix binds the receptor component of ____ on the outer mitochondria membrane, and is positioned into the TOM channel on the outer mitochondrial membrane
“presequences”, TOM
