Cell Biology Chapter 12: What are the different compartments (organelles) in an
ID: 36279 • Letter: C
Question
Cell Biology
Chapter 12:
What are the different compartments (organelles) in an eukaryotic cells?
What are the main function of each organelle and?
How are proteins moved between different compartments?
hint: gated transport, protein translocation, and vesicular transport
hint: know the direction and mechanism between organelles (figure 12.5 should help)
What is the function of the sorting signal in protein transport?
What is the function of signal peptidase?
Where is the signal peptidase located?
Know the four amino acid signal and location on the peptide for returning a protein back to the ER
Know the three amino acid signal sequence and location on the peptide for proteins destine for the peroxisome?
What is the peroxisome?
What are the amino acids for directing proteins to the nucleus?
What is the general feature of the signal sequence of proteins destined for the mitochondria?
Know the basic structure of the nucleus (figure 12.7 and 12.8 are good examples of what you should know along with the accompanying lecture).
Explanation / Answer
1. mitochondria, golgi body, vacuoles, rough and smooth endoplasmic reticulum, peroxisomes and ribosomes
2. ATP production, Lysosome production, transporters, production of proteins and transport them, lytic enzymes production and protein synthesis.
3. proteins are transported by the endoplasmic reticulum by translocation and vesicular transport
4. protein sorting helps in target fixing. meaning, tagging the proteins to their destinations like chloroplast, mitochondria etc.
5. signal peptidases are present in the endoplasmic reticulum and are functionally enzymes that convert secretory and membrane proteins to their mature form.
6. secATPase and BiP is also an essential component of the translocation machinery, as well as playing a role in retrograde transport of proteins across the ER membrane. Transport of aberrant proteins destined for degradation by the proteasome.
7. A target peptide is a short (3-70 amino acids long) peptide chain that directs the transport of a protein to a specific region in the cell, including the nucleus, mitochondria, endoplasmic reticulum (ER), chloroplast, apoplast, peroxisome and plasma membrane. Some target peptides are cleaved from the protein by signal peptidases after the proteins are transported. There are two types of target peptides directing to peroxisome, which are called peroxisomal targeting signals (PTS). One is PTS1, which is made of three amino acids on the C-terminus. The other is PTS2, which is made of a 9-amino-acid sequence often present on the N-terminus of the protein.
8. Lipid metabolism and chemical detoxification are important functions of peroxisomes. Peroxisomes are responsible for oxidation reactions that break down fatty acids and amino acids. Peroxisomes oversee reactions that neutralize free radicals, which cause cellular damage and cell death. Peroxisomes chemically neutralize poisons through a process that produces large amounts of toxic H2O2, which is then converted into water and oxygen.
9. A nuclear localization signal or sequence (NLS) is an amino acid sequence that 'tags' a protein for import into the cell nucleus by nuclear transport. Typically, this signal consists of one or more short sequences of positively charged lysines or arginines exposed on the protein surface. Different nuclear localized proteins may share the same NLS. An NLS has the opposite function of a nuclear export signal, which targets proteins out of the nucleus.
9 and 10. A nuclear localization signal (NLS) is a target peptide that directs proteins to the nucleus and is often a unit consisting of five basic, positively-charged amino acids. The NLS normally is located anywhere on the peptide chain. A nuclear export signal (NES) is a target peptide that directs proteins from the nucleus back to the cytosol. It often consists of several hydrophobic amino acids (often leucine) interspaced by 2-3 other amino acids.Many proteins are known to constantly shuttle between the cytosol and nucleus and these contain both NESs and NLSs.
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