Organelles Flashcards
Endosymbiotic theory
Archaea engulged aerobic around 2.5 billion years ago, becoming eurkaryotic cells containing either mitochondira or chloroplasts in an endosymbiotic relationship.
List the theories supported by the endosymbiotic theory.
- ) Archae glycosylate their proteins like eukaryotes, while bacteria do not
- ) Archaean DNA contains introns, promoters, histones, RNA polymerase, and transcriptional machinery more similar to eukaryotes.
- ) Bacteria have circular plasmid DNA that replicate through fission, as do mitochondira and chloroplasts
List the 1.) function and 2.) structure of the plasma membrane.
Function: Regluate movment of substances into and out of the cell via a semi-permeable membrane
Structure: Phospholipid bilayer made of charged, polar heads and non-polar hydrophobic tails.
What is a Glycocalyx?
Coat of sugar residues found on the exterior of the lipid bilayer. Attached to:
- Glycolipids: Lipids + saccaride
- Glycoproteins: Lipid + Protein
What is the function of the nuclear envelope.
To surround the nucleus and act as a selectively permeable membrane regulating traffic.
What is the 1.) structure of the nuclear envelope and 2.) describe the three membranes.
Double membrane that’s continuous with the rough endoplasmic reticulum (RER)
- Inner membrane: associated with nuclear lamina proteins that tether chromatin when cells is resting (not dividing)
- Outer membrane: Often speckled with ribosomes from the RER; continous with the inner memrbane at nucluear pores
- Cisterna: the space between the two membranes; aka the perinuclear space
What is the 1.) function, 2.) structure of the nucleolus?
- Function: To produce ribosomal RNA
- Strucure: 3 histologically distinct regions:
- Pars amphora (NO)–> DNA that codes for rRNA (aka Nucluear Organizing region
- Pars fibrosa ( PF)–> primary RNA transcripts
- Pars Granlulosa (PG)–> maturing ribosomal subunits (granular)
- Nucleolonema–> PF + PG ( which are both RNA)
List the two forms of chromatin
- Heterochromatin–> Heavy staining
- Euchromatin–> Light staining
List the following in most deconsed to condensed: DNA double helix, Chromatin fiber, Metaphase chromosome, condensed chromosome, nucleosomes
- ) DNA double helix
- ) Nucleosomes (DNA with histones)
- ) Chromatin fiber
- ) Looped domains
- ) Metaphase chromosome
What is the 1.) function, and 2.) structure of ribosomes
- Function: Translate mRNA transcripts into polypeptide chains.
- Structure: 1 large subunit + 1 small subunit that come together.
Distinguish between free ribosomes and ribosomes between attached to the endoplasmic ribosomes
Free ribosomes reside inside the cell (for the cytoplasm, cytoskeleton, nuclues, mitochondria, peroxisomes) while ribosomes attached to the ER are destined to leave the cell or will end up in the lysosomes.
What are the functions of the Endoplasmic Reticulum (ER)
- ) Cleave signal peptides
- ) Faciliate proper protein folding
- ) Attach oligosaccharides to maturing proteins
- ) Synthesize phospholipids, fats, and steroids
- ) Detoxify drugs or other harmful substances via enzymes
Distinugish between rough and smooth endoplasmic reticulum
Smooth ER- Lacks ribosomes
Rough ER- Dotted with ribosomes (continuous with nuclear envelope)
Describe the process of protein translocation and folding in the ER.
- ) Signal sequence appears on a growing peptide chain as it emerges from the ribosome
- ) Signal recognition particle (SRP) binds to signal sequence Translation pauses.
- ) SRP-bound ribosomes binds to a SRP receptor on the RER membrane. The SRP is cleaved and released. Translation resumes.
- ) Growing chain enters ER lumen and starts undergoing modifications as it’s being made.
Describe the process-translational modifications of proteins in the RER
- ) First glycoslyation of a protein occurs in the RER lumen. A dolichol linked to a pyrophosphate and oligosaccharide will use the PP link to transfer the sufar moiety onto an Asn residue on the growing peptide.
- ) The completed chain is released into the ER lumen to be properly folded
- ) If the protein isnt’ properly folded, its is tagged with ubiquitin to be degraded in proteosomes.
What is the function of Golgi Apparatus.
To sort, further modify, and package proteins from the ER vesicle for transport.
What are the two stacks of membrane (cisternae) that are continous with the RER.
- Cis (forming) face- receives proteins from adjacent RER
- Trans (maturing) face- secretes maturing proteins in vesicles for transport
State the significance of COP proteins for the vesicular transport between the RER and the Golgi apparatus
There are two COP proteins: COPII and COPI.
- COPII–> responsible for the forward transport from the RER to the cis-Golgi
- COPI–> brings vesicles backward from the Golgi to the RER (these contain improperly glycoylated or folded proteins.
What is the function of the KDEL receptor in the transport between RER and the Golgi apparatus
Receptors find misfolded proteins and help COPI ferry them back to the RER to get folded again
Identify the specific protein modifications of the Golgi appartus saccules as they passs from the Cis to Trans
In chronlogical order as they pass the Golgi apparatus:
1.) Cis Golgi network- phosphylate sugars (oligosaccharides) on lysosomal proteins
2.) Cist cisterna- removes mannose residues
3.) Medial cisterna- removes mannose residues, adds Glc
4.) Trans cisterna- addition of Galactose
End of the Golgi stack
5.) Trans Golgi network- Addition of NANA (sialic acid)
What is the function of Mannose-6-phosphate in the tranportation of vessicles from the cis-Golgi Network
When added in the cis-Golgi, Mannose-6-phosphate marker determines segregation to lysosomes
What is the function of the lysosomes
Lysosomes contain enzymes (acid hydrolases) that degrade substances
Distinguish between primary and seconday lysosomes
- Primary lysosomes have acid hydrolases but have not yet fused with any vesicles (they are newly budded fromthe trans Golgi)
- Secondary lysosomes have fused with a vesicle.
Describe the function of the peroxisosomes.
- Generates H2O2 (hydrogen peroxide) which oxidizes harmful substances
- Detoxifices alcohol and other harmful chemical
- Contains enzymes that perform beta oxidation of long chain fatty acids
