Lecture 5 - Eukaryotic Cell Structure Flashcards
Describe the origin of the eukaryotes referred to as The Endosymbiotic Hypothesis
- most common ancestor 2.1 bya
- oxygen was accumulating in the atmosphere 2.4 bya but all cells were toxic to oxygen
- eukaryotes evolved oxygen-neutralizing enzymes
How did internal membranes form?
- the surface area of Archaean increased by the infoldings of membranes
What are the steps of Eukaryote Evolution?
1) endomembrane system (infoldings of membranes)
2) endosymbiotic organelles (mitochondria and chloroplasts arose from a primitive prokaryote living inside a primitive eukaryote)
What is the good roommate hypothesis? provide evidence
- bacteria are sensitive to rising oxygen
- Archaea have evolved enzymes to neutralize toxic oxygen and they also have lots of space
evidence = mt and cp have: circular genome, bacterial-like gene organization, prokaryote-like ribosomes
also, the bacteria was ingested and not digested
What is the endomembrane system?
membrane-bound organelles that arose from infoldings of the membrane and are connected via vesicles
What are vesicles?
membrane-bound compartments that contain cargo
What are the organelles in the endomembrane system?
- outer nuclear membrane
- endoplasmic reticulum
- golgi
- lysosome
What is the function and structure of the nucleus?
function: storage of DNA and the site of gene expression
structure: double-membrane bound, the outer membrane is continuous with the ER
- NPC = nuclear pore complexes (transmembrane complexes that span both bilayers, allow non-specific transport)
What is the function of the nucleolus?
function: site of ribosomal subunit assembly
- ribosomes consist of two major protein components and associate with their rRNA at the nucleolus
- leave nucleus as independent subunits and come together in cytoplasm during translation
What is the function and structure of the nuclear envelope?
function: separates nucleoplasm from the cytoplasm (protects DNA)
structure: two lipid bilayers + nuclear lamina
Why do we need chromatin packaging?
- organize DNA
- protect from damage
What is the order of packaging?
*refer to notes, too much to type out
What is the function of the RER?
- covered in ribosomes
- enzymes of translation
- called bound ribosomes
- function: site of protein synthesis for a protein that functions within the endomembrane system and the site of protein quality control
What is the function of the SER?
- ion storage
- phospholipid synthesis
- steroid synthesis
- detoxification of drugs and alcohol
What is the function and structure of The Golgi Apparatus?
function: receives cargo from ER and sorta cargo to different destinations and then packages it into vesicles
structure: a set of flattened membrane sacs called cisternae
What are the two models of Golgi Trafficking?
- Vesicle Trafficking
- Cisternal Maturation
- refer to notes for extra content
What are lysosomes?
- ‘cell stomach’ = involved in digestion of macromolecules from endocytosis, contains many hydrolytic enzymes that function best at pH 5, lysosomes actively pump in H+ to maintain low pH to protect cells from accidental autophagy
What is autophagy?
- lysosome is a site of organelle recycling
- cells can commit cell suicide (apoptosis)
What organelles are not found in the endomembrane system?
- mitochondria and chloroplasts
- peroxisomes
- cytoskeleton
What are peroxisomes?
- specialized metabolic compartment
- involved in the oxidation reactions that often produce toxic byproducts
- involved in the detox of alcohol and metabolism of fats
What is the function and structure cytoskeleton?
- network of fibers extending throughout the cytoplasm
- three types: microtubules, microfilaments, and intermediate filaments
- function: support, motility, and cell shape
- structure: 3 components
What is the function and structure of microtubules?
- function: compression resistance
- structure: polymers of tubulin
- tubulin is a dimer of alpha and beta-tubulin monomers and 13 protofilaments bundle to form a rigid tube
What are associated motor proteins? What are Kinesin and Dynein?
- proteins that change shape with ATP hydrolysis that generates a force
- Kinesin = (+) end-directed MT motor
- Dynein = (-) end-directed MT motor
What is the function and description of the Eukaroyitc Flagellum?
- function: cell movement
- whiplike
- powered by ATP hydrolysis
- membrane-bound
- single and long = flagellum
- short and numerous = cilia
- movement is generated by dynein
What are the function and motor of microfilaments?
- polymer of actin
- function: tension resistance
- movement: cytokinesis, muscular contraction
- motor: myosin
What is the function and structure of intermediate filaments?
- function: tension-resistance, not very dynamic, they have no associated motor proteins and low turnover
- structure: many different subunit types that form rope-like filaments
