Chapter 15: Intracellular Compartments and Protein transport Flashcards
1
Q
Cytosol
A
- contains many metabolic pathways
- protein synthesis
- the cytoskeleton
2
Q
Nucleus
A
- contains main genome
- DNA and RNA synthesis
3
Q
Endoplasmic reticulum
A
- synthesis of most lipids
- synthesis of proteins for distribution to many organelles and the plasma membrane
4
Q
Golgi apparatus
A
- modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another organelle
5
Q
Lyosomes
A
intracellular degradation
6
Q
Endosomes
A
sorting of endocytosed material
7
Q
Mitochondria
A
ATP synthesis by oxidative phosphorylation
8
Q
Chloroplasts (in plant cells)
A
- ATP synthesis and carbon fixation by photosynthesis
9
Q
Peroxisomes
A
- oxidative breakdown of toxic molecules
10
Q
Name the three types of protein transport and how they sort
A
- transport through nuclear pores
- transport across membranes
- transport by vesicles
(signal sequences direct proteins to the correct compartment)
11
Q
Transport through nuclear pores
A
- maintains folding
- proteins can get into nucleus if they have NLS
(protein with NLS can possibly drag others without NLS in with them) - NLS recognized by import receptor, protein translated into cytosol
12
Q
NLS
A
nuclear localization signal
13
Q
How does nuclear transport happen?
A
- energy supplied by GTP hydrolysis
14
Q
Explain nuclear transport
A
- Ran protein (small GTPase) either carries GTP or GDP, converted when needed by accessory proteins
- Ran-GAP found in cytosol converts GTP to GDP
- Ran-GEF found in nucleus release GDP and uptake GTP
- GTP important in nucleus, so nuclear import receptors can bring in and attach nuclear proteins
- binding of Ran-GTP with receptor and its nuclear protein releases the nuclear protein into nucleus
- import receptor leaves nucleus through pore into cytosol with Ran-GTP still attached, hydrolyzes to GDP and falls off to bind to another protein
15
Q
Transport across membranes
A
- proteins unfold to cross the membrane of mitochondria and chloroplasts
- proteins can cross the membrane of the endoplasmic reticulum while being synthesized
16
Q
Describe transport into mitochondria
A
- mitochondrial precursor proteins are unfolded during import
- must cross mitochondrial outer and inner membrane
- receptor with TOM on outer membrane recognizes mito. precursor protein, transports signal sequence to intermembrane space
- 2nd receptor with TIM on inner membrane recevies signal as well
- together they push signal across membranes to unfold protein
- signal sequence cleaved off by peptidase in mito matrix
17
Q
Describe endoplasmic reticulum transport
A
- an ER signal sequence and an SRP direct a ribosome to the ER membrane
- SRP binds to exposed ER signal sequence and ribosome, which slows ribosome protein synthesis
- SRP/ribosome complex binds to SRP receptor in ER membrane
- SRP released and ribosome passes from SRP receptor to protein translocator in ER membrane
- protein synthesis resumes, translocator starts to transfer growing polypeptide across lipid bilayer
18
Q
TIM/TOM description
A
- translocator of inner membrane
translocator of outer membrane
19
Q
Describe Protein sorting: vesicular transportq
A
- allows materials to exit or enter the cell through endocytosis and exocytosis
- carry soluble proteins and membrane between compartments