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166 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Nuclear envelope |
Is a double membrane that surrounds the nucleus how |
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How does the nucleus communicate with the cytosol |
Via nuclear pores that perforate the envelopes t |
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Endoplasmic reticulum |
A system of interconnected membranous sacs and tubes that extends throughout the cell |
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Rough ER |
Has ribosomes |
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Fx of ribosomes |
Synthesize proteins that are inserted into the ER membrane or delivered to the ER interior |
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Lumen |
Interior area of the ER |
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Cytosol fx |
Metabolic pathways Proteins synthesis Cytoskeleton |
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Fx nucleus |
Contains main genome DNA and rna synthesis |
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Fx of ER |
Synthesis of most lipids Synthesis of proteins for distribution to many organelles and to the PM |
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Golgi apparatus fx |
Modification, sorting, packaging of proteins and lipids for either secretion or delivery to another organelle |
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Lysosome fx |
Intracellular degradation |
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Endosomes |
Sorting of e doctrines material |
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Mitochondria |
ATP synthesis by oxidative phosphorylation |
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Chloroplast( plant cells) |
ATP synthesis and carbon fixation by photosynthesis |
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Peroxiding |
Oxidative breakdown of toxic molecules |
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Cytoskeletal filaments |
Provide tracks for moving the organelles around and for directing the traffics of vesicles between one organelle and another |
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Differential centrifugation |
Seperate one type of organelle from another |
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Which organelles are part of the endomembrane system? |
ER, Golgi apparatus, peroxisomes, endosomes and lysosomes ( Legep) |
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What must a eukaryotic cell do before it divides? |
It must duplicate its membrane enclosed organelles |
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Which organelle has a major site of lipid and protein synthesis |
ER |
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In what way are proteins delivered for the following organelles directly from the cytosol |
Mitochondria, chloroplast and interior of the nucleus |
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In what way are proteins delivered for the Golgi aparatus, lysosomes, endosomes and Inner nuclear membrane |
Indirectly via the ER |
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Pathway of how proteins travel |
Enter the ER directly from the cytosol-Some stay here and some are transported by vesicles to the Golgi apparatus-then to the PM or to other organelles |
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Where does the synthesis of proteins being in the cell? |
On ribosomes in the cytosol |
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What do protein depend on to be synthesized in the cytosol? |
Amino acid sequence which can contain a sorting signal that directs the protein to the organelle in which it is required |
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What happens to proteins that don’t have a sorting signal |
They stay in the cytosol |
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Name the 3 mechanisms membrane enclosed proteins use to import proteins |
1 transport through nuclear pores 2. Transport across membranes 3. Transport by vesicles |
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Proteins moving from the cytosol into the nucleus are transported through? |
Nuclear pores which penetrate the inner and outer nuclear membranes. The pores function as selective gates that actively transports specific macromolecules but also allow free diffusion of smaller molecules |
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Proteins moving from the cytosol into the ER, mitochondria, or chloroplast are transported across the organelle membrane by |
Protein translocators For this process the protein must fold |
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Proteins moving onward from the ER- and from one compartment of the endomembrane system to another are transported by |
A mechanism. These proteins are ferried by transport vesicles, which pinch off from the membrane of one compartment and then fuse with the membrane of a second compartment |
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What do signal sequence do? |
Direct protein to a particular destination |
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Nuclear envelope |
Encloses the nuclear DNA and is formed from two membranes |
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Name the 2 concentric membranes of the nuclear envelope |
Inner nuclear membrane and outer nuclear membrane |
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Inner nuclear membrane |
Contains proteins that acts as binding sites for the chromosomes and others that provide anchorage for the nuclear lamina |
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Nuclear lamina |
A finely woven mesh work of protein filaments that lines the inner face of this membrane and provides structural support for the nuclear envelope |
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Outer nuclear membrane |
Resembles the membrane of the ER with which it continues |
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Nuclear pores |
They are perforated on the nuclear envelope and they form gates through which molecules enter or leave the nucleus |
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Nuclear localization signal |
A signal sequence that directs a protein from the cytosol into the nucleus
This is how large molecules and macro molecular complexes gain entry into a pore |
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Nuclear localization signal |
A signal sequence that directs a protein from the cytosol into the nucleus
This is how large molecules and macro molecular complexes gain entry into a pore |
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Nuclear import receptors |
Help direct a newly synthesized protein to a nuclear pore by interaction with the tentacle like fibrils that extend from the rim of the pore into the cytosol. |
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The import of nuclear proteins is powered by? |
The energy provided by the hydrolysis of GTP |
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What mediates the hydrolysis of GTP? |
A monomeric GTPase named Ran |
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Two conformations of Ran |
1. Bearing a molecule of GTP 2. Bearing a molecule of GDP |
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Localization of Ran-GTP |
Present in high concentrations in the nucleus |
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Localization if Ran-GDP |
Is produced in the cytosol |
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What happens in the nucleus when Ran-GTP displaces the prospective nuclear protein from its receptor? |
Allows the imported protein to be released. The import receptor now bearing Ran-GTP returns to the cytosol, where hydrolysis of GTP allows Ran-GDP to dissociate, leaving the receptor free to pick up another protein destined for the nucleus. In this way GTP hydrolysis drives nuclear transport in the appropriate direction |
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Similarities between mitochondria and chloroplasts |
1. Surrounded by inner and outer membranes 2.specializes in the synthesis of ATP |
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What is the name of the extra membrane that chloroplasts contain? |
The thylakoid membrane |
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Fx of chaperone proteins inside the organelles |
Help to pull the protein across the two membrane and to fold it once it is inside |
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How are phospholipids transported to organelles by lipid carrying proteins? |
They extract a phospholipid molecule from one membrane and deliver into another |
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From where do proteins enter the peroxisome? |
Cytosol and ER |
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Peroxisome |
Is packed with enzymes that digest toxins and synthesize certain phospholipids, including those present in the myelin sheath surrounding nerve cell axons |
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Do proteins need to fold to enter the peroxisome like the Mito and chloro |
No |
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Do proteins need to fold to enter the peroxisome like the Mito and chloro |
No |
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In what way do proteins enter the ER? |
While being synthesized |
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Endoplasmic reticulum serves as? |
An entry point for proteins destined for other organelles. As well for the ER itself |
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Proteins destined for other organelles enter the ER first, what happens after? |
Once inside the ER lumen, or embedded in the ER membrane, individual proteins will not re-enter the cytosol during their onward journey. They will be ferried by transport vesicles from organelle to organelle within the endomembrane system or to the PM |
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What are the two kinds of proteins that are transferred from the cytosol to the ER? |
1. Water soluble proteins 2. Prospective transmembrane proteins |
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Water soluble proteins |
Are completely translocated across the ER membrane and are released into the ER lumen |
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Prospective transmembrane proteins |
Are translocated across the ER membrane and become embedded in it |
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What are the water soluble proteins destined for? |
Secretion ( by release on the cell surface) Or for the lumen of an organelle of the endomembrane system |
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The transmembrane proteins are destined to? |
Reside in the membrane of one of these organelles or in the PM |
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2 types of ribosomes in the cytosol |
Membrane bound ribosomes Free ribosomes |
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Membrane bound ribosomes |
Are attached to the cytosolic side of the ER membrane and are making proteins that are being translocated into the ER |
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Free ribosomes |
Are unattached to any membrane and are making all of the other proteins encoded by the nuclear DNA |
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Location of the signal recognition particle |
Cytosol |
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Two proteins components help guide ER signal sequences to the ER membrane |
1. Signal recognition particle SRP 2. SRP receptor |
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Location of the signal recognition particle |
Cytosol |
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Two proteins components help guide ER signal sequences to the ER membrane |
1. Signal recognition particle SRP 2. SRP receptor |
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Location of SRP receptor |
Embedded in the ER membrane |
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What happens when an SRP binds to a ribosome that displays an ER signal sequence? |
Slows protein synthesis by that ribosome |
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What do start and stop signals determine? |
The arrangement of a transmembrane protein in the lipid bilayer |
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What does the N terminal signal sequence initiate? |
Translocation |
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Stop transfer sequence |
Is a sequence of hydrophobic amino acids that halts the transfer process |
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Start transfer sequence |
Is an internal signal sequence used to start the protein transfer in transmembrane proteins |
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Start transfer sequence |
Is an internal signal sequence used to start the protein transfer in transmembrane proteins |
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Transport vesicles |
Transport proteins from the ER to Golgi and from Golgi to other compartments of the endomembrane system |
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Coated vesicles |
Are vesicles that have a distinctive protein coat on their cytosolic surface |
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2 functions of the coat |
1. It helps shape the membrane into a bud 2. It captures molecules for onward transport |
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Clathrin coated vesicles |
Bud from both the Golgi on the outward secretory pathway and from the plasma membrane on the inward endocytic pathway |
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Clathrin coated vesicles |
Bud from both the Golgi on the outward secretory pathway and from the plasma membrane on the inward endocytic pathway |
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Name the 2 classes of coats |
1. Clathrin 2. Adaptins |
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Fx of adaptins |
1. Secure the Clathrin coat to the vesicles membrane 2. Helps select cargo molecules for transport |
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2 types of adaptins |
1. The one that binds cargo receptors in the PM 2. The one that binds cargo receptor in the Golgi |
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COP coated vesicles |
Involved in transporting molecules between the ER and Golgi from one part of the Golgi to another |
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What transports the vesicles to it’s destination? |
Motor proteins that move along cytoskeletal fibers |
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See back |
What do transport vesicles on its surface that identify the vesicle according to its origin and cargo? |
Molecular markers |
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What does the identification process depend on? |
Monomeric GTPases called rab proteins |
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How are the Rab proteins on the vesicle recognized? |
By tethering proteins on the cytosolic surface of the target membrane |
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SNAREs |
Are transmembrane proteins that provide additional recognition |
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SNAREs on the vesicle is called |
V-snares |
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SNAREs on the vesicle is called |
V-snares |
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SNAREs on the target membrane is called? |
T- snares |
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Exocytosis |
Proteins, lipids, and carbohydrates are delivered from ER to Golgi to the cell surface of the transport vesicle that fuse with the PM |
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What do the disulfide bonds that are formed by the oxidation of pairs of cysteine side chains help with? |
To stabilize the structure proteins that will encounter degradative enzymes and changes in the pH outside the cell |
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What do the disulfide bonds that are formed by the oxidation of pairs of cysteine side chains help with? |
To stabilize the structure proteins that will encounter degradative enzymes and changes in the pH outside the cell |
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Do disulfide bonds form in the cytosol? |
No, because the environment is reducing |
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Glycosylation |
Is the process of converting proteins that enter the ER lumen or ER membrane to glycoproteins in the ER |
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Function of the oligosaccharides on proteins? |
1. Protect a protein from degradation 2. Hold it in the ER until it is properly folded 3. Help guide it to the appropriate organelle by serving as a transport signal for packing the protein into appropriate transport vesicles |
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Function of the oligosaccharides on proteins? |
1. Protect a protein from degradation 2. Hold it in the ER until it is properly folded 3. Help guide it to the appropriate organelle by serving as a transport signal for packing the protein into appropriate transport vesicles |
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Glycocalyx |
Cell’s outer carbohydrate layer ( oligosaccharide form part of this) |
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Function of the oligosaccharides on proteins? |
1. Protect a protein from degradation 2. Hold it in the ER until it is properly folded 3. Help guide it to the appropriate organelle by serving as a transport signal for packing the protein into appropriate transport vesicles |
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Glycocalyx |
Cell’s outer carbohydrate layer ( oligosaccharide form part of this) |
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Some proteins are destined to stay in the ER and are returned to the ER if they manage to escape by? |
A C terminal sequence of four amino acids called ER retention signal |
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Function of the oligosaccharides on proteins? |
1. Protect a protein from degradation 2. Hold it in the ER until it is properly folded 3. Help guide it to the appropriate organelle by serving as a transport signal for packing the protein into appropriate transport vesicles |
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Glycocalyx |
Cell’s outer carbohydrate layer ( oligosaccharide form part of this) |
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Some proteins are destined to stay in the ER and are returned to the ER if they manage to escape by? |
A C terminal sequence of four amino acids called ER retention signal |
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What happens to proteins that fail to fold correctly, and dimeric or multi Eric proteins that do not assemble properly? |
They are retained in the ER by binding to chaperone proteins |
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Why do chaperones hold proteins in the ER? |
They hold them until proper folding or assembly occurs. They also prevent misfolded proteins from aggregating, which helps steer proteins along a path toward proper folding |
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What happens if proper folding still fails? |
The proteins are then exported to the cytosol, where they are degraded by the proteasome |
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Unfolded protein response (UPR) |
Is a complex program that gets triggered when the quality system in the ER get overwhelmed with misfolded proteins |
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What does the unfolded protein response( UPR) complex do? |
Prompts the cell to produce more ER, including more chaperones and other proteins concerned with quality control |
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What does the unfolded protein response( UPR) complex do? |
Prompts the cell to produce more ER, including more chaperones and other proteins concerned with quality control |
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What does UPR also do? |
Adjust the size of its ER to properly handle the volume of proteins entering the secretory pathway |
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What happens when an expanded ER cannot keep up with the demand? |
The unfolded protein response directs the cell to self destruct by undergoing apoptosis |
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Cisternae |
Flattened, membrane enclosed sacs in the Golgi |
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Name the two distinct faces of the Golgi |
1. Cis face, entry 2. Trans face, exit |
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The cis face is adjacent to______ The trans face points toward the __________ |
1. ER 2. PM |
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The two ways proteins travel through the cisternae |
1. By transport vesicles that bud from one cisternae and fuse with the next 2. By a maturation process in which the Golgi cisternae themselves migrate through the Golgi stack |
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From where do the proteins finally exit in transport vesicles destined for either the cell surface or another organelle of the endomembrane system |
Trans Golgi network |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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What happened with proteins that enter the cis Golgi network? |
1. Move onward through the Golgi stack 2. If they contain an ER retention signal, can be returned to the ER |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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What happened with proteins that enter the cis Golgi network? |
1. Move onward through the Golgi stack 2. If they contain an ER retention signal, can be returned to the ER |
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What happens with proteins exiting from the trans Golgi network? |
Are sorted according to whether they are destined for lysosomes or for the cell surface |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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What happened with proteins that enter the cis Golgi network? |
1. Move onward through the Golgi stack 2. If they contain an ER retention signal, can be returned to the ER |
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What happens with proteins exiting from the trans Golgi network? |
Are sorted according to whether they are destined for lysosomes or for the cell surface |
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Constitutive exocytosis pathway |
Operates in all eukaryotic cells |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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What happened with proteins that enter the cis Golgi network? |
1. Move onward through the Golgi stack 2. If they contain an ER retention signal, can be returned to the ER |
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What happens with proteins exiting from the trans Golgi network? |
Are sorted according to whether they are destined for lysosomes or for the cell surface |
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Constitutive exocytosis pathway |
Operates in all eukaryotic cells |
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Regulated exocytosis pathway |
Operates in cells that are specialized for secretion |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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What happened with proteins that enter the cis Golgi network? |
1. Move onward through the Golgi stack 2. If they contain an ER retention signal, can be returned to the ER |
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What happens with proteins exiting from the trans Golgi network? |
Are sorted according to whether they are destined for lysosomes or for the cell surface |
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Constitutive exocytosis pathway |
Operates in all eukaryotic cells |
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Regulated exocytosis pathway |
Operates in cells that are specialized for secretion |
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Proteins that are destined for regulated secretion are sorted and packed in ? |
The trans Golgi network |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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What happened with proteins that enter the cis Golgi network? |
1. Move onward through the Golgi stack 2. If they contain an ER retention signal, can be returned to the ER |
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What happens with proteins exiting from the trans Golgi network? |
Are sorted according to whether they are destined for lysosomes or for the cell surface |
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Constitutive exocytosis pathway |
Operates in all eukaryotic cells |
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Regulated exocytosis pathway |
Operates in cells that are specialized for secretion |
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Proteins that are destined for regulated secretion are sorted and packed in ? |
The trans Golgi network |
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Two main type of endocytosis |
1. Pinocytosis ( cellular drinking) 2. Phagocytosis ( cellular eating) |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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What happened with proteins that enter the cis Golgi network? |
1. Move onward through the Golgi stack 2. If they contain an ER retention signal, can be returned to the ER |
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What happens with proteins exiting from the trans Golgi network? |
Are sorted according to whether they are destined for lysosomes or for the cell surface |
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Constitutive exocytosis pathway |
Operates in all eukaryotic cells |
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Regulated exocytosis pathway |
Operates in cells that are specialized for secretion |
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Proteins that are destined for regulated secretion are sorted and packed in ? |
The trans Golgi network |
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Two main type of endocytosis |
1. Pinocytosis ( cellular drinking) 2. Phagocytosis ( cellular eating) |
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Pinocytosis |
Involves the ingestion of fluid and molecules via small Pinocytic vesicles |
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Why are cis and trans Golgi networks import? |
Important for protein sorting |
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What happened with proteins that enter the cis Golgi network? |
1. Move onward through the Golgi stack 2. If they contain an ER retention signal, can be returned to the ER |
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What happens with proteins exiting from the trans Golgi network? |
Are sorted according to whether they are destined for lysosomes or for the cell surface |
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Constitutive exocytosis pathway |
Operates in all eukaryotic cells |
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Regulated exocytosis pathway |
Operates in cells that are specialized for secretion |
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Proteins that are destined for regulated secretion are sorted and packed in ? |
The trans Golgi network |
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Two main type of endocytosis |
1. Pinocytosis ( cellular drinking) 2. Phagocytosis ( cellular eating) |
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Pinocytosis |
Involves the ingestion of fluid and molecules via small Pinocytic vesicles |
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Phagocytosis |
Involves the ingestion of large particles, such as microorganisms and cell debris, via large vesicles called phagosomes |
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Pinocytosis is carried out by? |
Clathrin coated pits and vesicles |
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