Cell Phys Exam 3 (Module 9-13)

functions of mitochondria

functions of mitochondria

ATP production, cell death, calcium homeostasis, amino & fatty acid metabolism, aging, immunity

beta oxidation

fatty acid metabolism

mitochondrial matrix

contains mitochondrial genome, ribosomes, and metabolic enzymes

positive charge of MTS is attracted to negative charge of matrix

why must the matrix be negatively charged?

mitochondrial inner membrane

contains electron transport chain

mitochondrial outer membrane

contains channels that transport proteins from cytosol into mitochondria

endosymbiosis

mitochondria were an ancient bacterium that was engulfed by an ancient primitive archaeal cell

proteome

the complete set of proteins that make up a specific organelle

1%

what percentage of total mitochondrial proteins is encoded by the genome?

99%

percentage of mitochondrial proteins encoded by nucleus

mitochondrial genome

encodes for some of the subunits of the electron transport chain

F, it only codes for SOME, the rest come from the nucleus

T/F: The mitochondrial genome encodes for all of the subunits of the electron transport chain.

T

T/F: Proteins have sorting signals to target them to specific cell locations

signal sequences

can be found at the edge or within proteins; very specific due to having specific arrangements & compositions of amino acids that are recognized by specific proteins to bring them to the organelle

after the entire genome is translated

when do mitochondrial proteins enter the mitochondria?

cytosolic ribosomes

responsible for post-translational translocation

free cytosolic & ER-bound

what types of ribosomes translate proteins?

Green Fluorescent Protein

fluorophore that glows in the presence of blue light; used to find localization signals on proteins; attaching targeting sequence will bring it to where that protein is going to

aequorin

bioluminescent protein that gives off blue light

1. specific mitochondrial targeting sequences

2. specific transporters

what does mitochondrial protein import involve?

mitochondrial matrix targeting sequence

Located at N-terminus of matrix protein; amphipathic helix; must be at beginning of protein sequence; only cleavable

mitochondrial inner membrane sequence

has non-cleavable transmembrane segment & cleavable targeting sequence

T

T/F: It is possible to have only non-cleavable internal sorting sequences in a protein

mitochondrial outer membrane sequence

has non-cleavable internal sorting sequences

TOM (Translocase of the Outer Membrane) complex

recognizes all nuclear encoded mitochondrial proteins through multiple receptors; only recognizes targeting sequence of outer membrane proteins; located in outer mitochondrial membrane; INDIRECTLY inserts protein into outer membrane

SAM complex

DIRECTLY inserts nucl. encoded mitochondrial proteins into outer membrane through mediation of the TOM complex

TIM22 (translocase of the inner membrane) complex

inserts nucl. encoded mitochondrial proteins into inner membrane

TIM23 complex

dimer; the transporter that brings proteins into the matrix and the inner mitochondrial membrane

OXA complex

inserts mito encoded mitochondrial proteins into inner membrane

mitochondrial targeting sequence

MUST be the first amino acid sequence in the protein

TOM40

central channel that proteins pass through

TOM20 & TOM22

the receptors recognizing matrix proteins with a MTS (mitrochondrial targeting sequence)

TOM20

recognizes hydrophobic side

TOM22

recognizes positively charged side

TIM50

first receptor to bind incoming matrix protein as it passes thru TOM40

until the stop-transfer sequence is recognized

when an inner membrane protein reaches the TIM channel, it will travel thru until when?

cytosolic hsp70

makes sure protein is linear1

mitoHSP70

chaperone that binds incoming MTS of matrix protein and pulls it in

peptidase

what cleaves MTS?

mitochondrial and nuclear genomes

encode mitochondrial inner membrane proteins

2

there must be how many import pathways for inner membrane proteins?

Path A

import pathway for nuclear encoded mito inner membrane proteins

nuclear encoded mito inner membrane proteins

have MTS & a hydrophobic stop-transfer sequence

Path B

import pathway for mitochondrial-encoded mito inner membrane proteins

through genome and ribosomes

how do mitochondria translate ETC subunit proteins?

OXA1 complex

transports mitochondrial-encoded proteins into inner membrane

OXA1 targeting sequence

contained in mitochondrial-encoded mito inner membrane proteins and found in genome-encoded proteins

T

T/F: All outer membrane proteins come from nuclear genome

F

T/F: TOM complex directly inserts the protein into the outer membrane

T

T/F: SAM complex directly inserts an outer membrane protein into the outer membrane

nucleus

largest organelle; contains chromatin (DNA)

nuclear envelope

double membrane (outer & inner); selective transport of molecules in & out of nucleus; contains nuclear pores

nuclear pores

used to transport molecules between nucleus & cytoplasm

nuclear lamina

on the inner side of the inner membrane; support structure

nucleolus

major site of ribosome biogenesis

nuclear envelope outer membrane

contiguous (merged) w/ ER

passive diffusion

Process by which molecules move across a cell membrane from an area of higher concentration to an area of lower concentration without the use of energy

active diffusion

molecules move across membrane from high to low concentration using ATP

passive

proteins smaller than 40 kDa can move in & out of the nuclear pore via ___ diffusion

active

larger proteins move in & out of the nuclear pore via ___ diffusion

terminal structures

extend on either end of nuclear pore

docking

attachment of proteins to the nuclear pore; energy independent

transport thru nuclear pore

requires energy, is selective & requires regulation

nuclear localization sequence

dictates nuclear import; sorting sequence that targets proteins to nucleus

basic residues of NLS

Arginines/R & Lysines/K

necessary

proteins would only go to cytoplasm & not nucleus without NLS

sufficient

NLS can drive localization to the nucleus by putting it w/ GFP

importins

recognize NLS (localization)

exportins

recognize NES (export)

GTPases

control whether a protein is imported or exported

guanine nucleotide exchange factor (GEF)

exchange GDP for GTP

T

T/F: every protein w/ a NES inherent has an analyze sequence because an analyze sequence is required for import

ran GTPase

GTP bound in nucleus

ran GTPase during import

allows release of cargo from importin in nucleus

ran GTPase during export

binding needed for exportin to bind NES-containing cargo proteins

ran GAP

causes ran GTPase to hydrolyze GTP to GDP which releases cargo; located in cytoplasm

key to ran GTPase regulation

location of ran GAP and GEF

ran GEF

in nucleus; needed to have an active ran GTPase to release cargo from importin and to bind export cargo

Ntf2

used to get ran GDP back into the nucleus after GTP hydrolysis

dual-localized protein

function can be same or different in each cellular compartment

mitochondrial unfolded protein response (UPRmt)

protein has both MTS and NLS; transcriptional GEP reporter is used to study activity & experimented in worms

nucleus

all mitochondrial chaperones & proteases are expressed in the ___

ATFS-1

transcription factor that regulates genes that repair mitochondria; during mitochondrial stress it increases expression of chaperones & proteases; has a nuclear export sequence

import into matrix requirements

ATP hydrolysis & membrane potential

TIM9 & TIM10

chaperones that assist w/ insertion of outer membrane proteins into the outer membrane

F: it is only for ran-GDP

T/F: Ntf2 goes back to the cytoplasm for repeated nuclear import of Ran-GTP

weaker membrane potential, less ATP & less mitochondrial import

why does the electron transport chain not work for stressed mitochondria?

F: healthy mitochondria can fuse to unhealthy ones to help out

T/F: mitochondria cannot fuse together

F: ATFS-1 will be degraded because it’s no longer needed

T/F: Healthy mitochondria will import ATFS-1 and store it for later use

F: there is a possibility not to express it when stressed

T/F: A worm will not express fluorescent green only when not stressed

cytoskeleton functions

• Cell support and shape

• Cell motility

• Cell polarity

• Cell engulfment

• Cell migration      

• Wound healing

T

T/F: Cytoskeletal components are all protein polymers

characteristics of actin

• ubiquitous

• highly conserved

• abundant

• multiple isoforms

• polarized

• has longitudinal & lateral bonds to strengthen filament

G-actin

units that make up F-actin

plus end of actin filament

where monomers are put on

minus end of actin filament

where subunits fall off

actin monomer

composed of 2 lobes & a cleft; is an ATPase

T

T/F: ATP hydrolysis is not required for polymerization of the actin filament, but instead is used to regulate the filament

3 phases of actin polymerization

nucleation, elongation & steady state

rapid

is actin elongation slow or rapid?