Cell Physiology Flashcards
(33 cards)
What are the basic components of the cell?
Nucleus Plasma membrane Cytoplasm -organelles -cytosol
Describe the structure and function of the nucleus
The nucleus is the control center of the cell
It contains the genetic material that is packaged DNA
It is responsible for gene expression
What is the difference between heterochromatin and euchromatin?
Heterochromatin: compacted, transcriptionally inactive
Euchromatin: transcriptionally active
What is the nuclear envelope and its function?
Nuclear envelope: Separates nuclear material from cytosol
- Separates nuclear contents from cytosol-Barrier-nucleus as distinct biochemical compartments
- 2 nuclear membranes->inner and outer
- outer membrane is continuous with ER, lumen enzymes same as ER, attached ribosomes
- phospholipid bilayer permeable only to small Nonpolar molecules
What is the lamina?
Attached to inner nuclear membrane, fibrous mesh work, lamins, barrier to molecules, structural support, intermediate fibers
Describe the nuclear pore complex.
Nuclear membrane is impermeable to large molecules
Only permeable to small polar molecule, ions and macromolecules.
Nuclear localization signals (nuclear import signals)-importins (karyopherin)
Nuclear export signals-RA related nuclear proteins-exportins (karyopherin)
Nuclear pore complex is energy dependent
What is the main role of the ER?
Central role in lipid and protein biosynthesis. Site of productions of all transmembrane proteins and lipids for most of the cells organelles including ER
Site of production of all proteins and lipids
What is the signal hypothesis?
The leader sequence serves as a signal peptide that directs the secreted proteins to the ER membrane and is cleaved off by a signal peptidase in the ER membrane before the peptide chain is completed
What is the Nascent polypeptide chain
~20 residues, mostly hydrophobic and not present in mature proteins.
What is an SRP?
Signal recognition particle, directs ER signal peptides to a specific receptor/SRP receptor/docking site in the ER
What is a ribophorin?
SRP-ribosome binding proteins on ER
What is a translocons?
Protein translocation across and into ER membrane sites. Pore for secretory proteins
What does the signal peptidase do?
Cleaves signal peptide and translated protein is escorted by chaperones
What are chaperones?
Protein transport, folding and activity requires ATP
Go through the process of a protein exiting the cell starting at the RER.
1) RER synthesizes and releases new proteins into the ER lumen
2) Within ER lumen, a newly synthesized protein is folded into a final conformation and my be modified
3) A new protein is not able to pass out through the ER membrane
4) new protein goes to the SER
5) SER packages the new protein into transport vesicles
6) Synthesizes lipids, phosopholipids and steroids
7) These vesicles bud off the Golgi complex
8) protein exists the beta cell
What is the job of the Golgi complex?
Molecules travel through the sacs of the Golgi complex by vesicular transport
Molecules are altered from a raw form to a more finished, functional form
Molecules are also sorted into groups based on their functions and final destinations in the cell to carry out those functions
What are the steps of protein modifications in the Golgi.
1) Cis and CGN Cisternae:RER retrieval, add PO4 on mannose, then remove mannose
2) Medial Cisternae: mannose removal then N-acetlyglucosamine addition
3) Trans Cisternae: fructose and glucose addition
4) Sialic acid addition, then protein sorting
What is exocytosis?
The mechanism by which secretory cells release or secrete their products.
-vehicle fusion is very specific; contents are never in contact with the cytosol
How is vehicle formation and fusion with the plasma membrane specifically achieved?
1) marker proteins act as recognition markers for only specific proteins(NSF receptor and SNAP)
2) linking of coat proteins case the membrane to curve and budding from other outer membrane-(Clatherins and Adaptins)
3) shedding of coat, exposing docking markers -v-SNARE
4) docking of vehicle with a plasma membrane marker protein (t-SNARE)
* SNARE hypothesis: v-SNAREs and t-Snares interaction and recruitment of NSF and SNAPs
In order summarize the steps for secretion of an ER-Synthesized protein.
1) The RER synthesizes proteins to be secreted
2) The SER packages the secretory product into transport vesicles, which bud off and move to the Golgi complex
3) The transport vesicles fuses with the Golgi complex
4) The newly synthesized proteins travel through the layers of the Golgi complex and being modified
5) Secretory vesicles contains the finished protein product bud off the Golgi complex and remain in cytosol
6) with appropriate stimulation, the secretory vesicles fuse with the plasma membrane, open and empty their contents to the cells exterior
Define the difference between lysosomes and peroxisomes
Lysosomes degrade material that is brought into the cell through endocytosis. They contain digestive enzymes and digest worn out and excess organelles, food particles, and engulfed viruses and bacteria.
Peroxisomes are also enzyme filled but they have oxidative enzymes and catalase
What does a peroxisomes do?
Breaks down hydrogen peroxide to make O2 and water
Name and define the three types of endocytosis.
1) pinocytosis: “cell drinking”, internalizes small broken particles and is non-selective
2) Phagocytosis: “cell eating”, internalizes large particles
3) Receptor-mediated endocytosis: a molecule attaches to a receptor site on the membrane, triggering can internalization event; it’s highly selective and molecule specific
What are the components of the mitochondria?
Outer membrane Inner membrane Matrix DNA Ribosome
