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Lecture 7
Nucleus
| Question | Answer |
|---|---|
| Prokaryote | No true nucleas Nucleoid, w/1 to 3 circular chromosomes Eubacteria, Archaebacteria |
| Nucleoid | region of condensed DNA |
| Eukaryote | Have true nucleus w/multiple chromosomes inside the nuclear membrane double layer.Endomembrane system;organelles Plants, animals, fungi, protozoa, and algae. |
| Nuclear envelope | double layer of membrane |
| Plasmids | self replicating extra chromosomal circular DNA molecules. Nonessential for cell survival under nonselective conditions. provide a mechanism for gene transfer and a selective advantage for the microbe. |
| Plasmids Provide | resistance to antibiotics, produce proteins that act as toxins, provide bacteria the ability to fix nitrogen or degrade compounds for nutrition |
| The use of Plasmids in cell physiology | artoficial plasmids as cloning vectors and to transfect specific cells. allow the transfer of specific genetic elements into cells for study |
| Engineered plasmids for study of | protein function gene regulation microRNA (miR) function |
| protein plasmid study | express a functional protein of interest |
| Gene plasmid study | gene regulation; to express a reporter gene under control of specific gene promoters |
| MicroRNA(miR)Plasmid study | to express a specific miR |
| gene promoter study | inject gene of interest into tissue of interest (in vivo or in vitro) and look for results. |
| prokaryote vs. eukaryote | eukaryotic cells have cytoskeletal proteins not found in prokaryotes. exocytosis/endocytosis occurs in eukaryotes;not in prokaryotes mitosis/meiosis in eukaryotes, binary fission in prokaryotes gene expression is complex in eukaryotes |
| binary fission | cell elongation and dna is replicated, cell wall and plasma membrane begin to divide, cross wall forms around divided dna, then cells seperate |
| factors that limit cell size | 1. surface/volume ratio 2. diffusion problems as vol. increases 3. potential for inadequate conc. of reactants and catalyst;enzymes |
| cytoplasmic streaming | by utilizing cyclosis diffusion within the cell becomes problematic as the volume becomes larger. |
| How cells overcome limitations | 1. muscle fibers have hundreds of nuclei to support synthesis of RNA and proteins. 2. in order for a fiber to grow it must add additional myonuclei. |
| The Nucleus | 1. houses the chromosomes (dna) 2. surrounded by the nuclear envelope 3. nucleoplasm 4. nuclear pores 5. nucleolus 6. chromatin |
| Chromatin | dispersed chromosome; heterochromatin, euchromatin |
| heterochromatin | densly packaged, less actively transcribed 1. constitutive- always condensed 2. facultative- inactive chromosomal regions |
| Euchromatin | loosly packed allows for proteins to interact with the DNa gene transcription (more actively transcribed) |
| Nuclear Pores | nucleus contains 3000-4000 nuclear pores diameter of a pore is 120 nm consists of 50 proteins called nucleoporins |
| 4 main nuclear pore components | 1. cytoplasmic ring 2. nuclear ring and basket-regulation 3. lumenal rings- anchor- annular rings 4. transporter (central granule)- involved in physical transport |
| Nuclear Pore functions | 1. mediates the energy dependent transpot of nuclear proteins in and out of nucleus. 2. allows passive diffusion of small molecules and ions. |
| nuclear protein import | protein destined for the nucleus must have a nuclear localizing signal (NLS) |
| karyopherins | class of proteins that assist in shuttling proteins across the nuclear envelope, via the nuclear pore |
| importins | assist in nuclear import |
| exportins | assist in nuclear export by binding with ran-GTP which allows it to bind to its cargo that contains NES, exportin interacts with NPC and moves cargo out of nucleus |
| importin subunits | 1. importin alpha- adapter protein 2. importin beta- interacts directly with the pore transporter |
| Importin beta function | can function alone by direcly interacting with the cargo protein or importin alpha binds to the target protein at its NLS and to importin beta. Importin alpha acts as an adapter protein btwn the cargo protein and importin beta. |
| (RNP) ribonucleoproteins particles | are mRNA and rRNA bound toproteins |
| nuclear export | protein export out of nucleus must have a nuclear export signal (NES)the NES interacts with exportin which facilitaates nucelar export |
| Cargo | can be a protein or RNP (must have NES nuclear export signal) |
| nuclear export in 5 steps | 1. exportin binds to Ran-GTP 2. exportin-ran-GTP binds to the cargo 3. entire complex is exported via the NPC 4. in the cytosol, GTP is hydrolyzed and RNP and exportin are released 5. exportin is then recycled back into the nucleus |
| How does Ran get back into the nucleus? | 1. Ran-GDP associates with NTF2 (nuclear translocation factor 2) 2. Ran-GDP-NTF@ complex interacts with the NPC and translocates into the nucleus 3. the NTF2 releases Ran in the nucleus where Ran interacts with the GEF which binds a new GTP to Ran. |
| Nuclear transport cycle | 1. Ran-GTP binding to importin allows for release of cargo from importin 2.Ran-GTP binding to exportin allows for binding of cargo to exportin |
| NFAT-nuclear factor of activated T-cells | transcription factor protein involved in many cellular processes (t-cells, skeletal muscle, heart) |
| NFAT in cell signaling | transduces a physiological signal into a molecular signal |
| Nuclear Matrix | 3-dimensional fibrous network forms a scaffolding "nuclear skeleton" |
| Nuclear lamina | meshwork of fibrous proteins that line the inner surface of the nuclear envelope |
| the nuclear structure | 1. form a supporting network of proteins that maintains the 3-D shape of the nucleus. 2. anchor and organize the chromatin 3. act to transmit mechanical signals to the genes. |
| nucleolus | site of synthesis of rRNA and ribosomal proteins |
| core | nucleolus organizing region NOR |
| NOR | segments of DNA with repeated sequences that code for rRNA and ribosomal protein |
| nucleolar fibrils | DNA and rRNA |
| nucleolar granules | ribosomal subunits (rRNA and proteins) |
| nucleolar size | correlates with its activity and level of protein synthesis |
Created by:
aareynolds
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