The Cell Flashcards
What are most taxonomical classification systems based upon? So what can you conclude about any two animals from the same class for example?
Based upon genetic similarity resulting from shared phylogeny, or evolutionary history.
So all mammals likely share a common genetic ancestor.
What is a likely mechanism of mitochondria evolution?
From a symbiotic relationship btwn aerobic prokaryotes and eukaryotes.
What is the cell wall of bacteria made of? (detail)
Peptidoglycan.
- consists of a series of disaccharide polymer chains with AAs. The chains are attached by an interbridge of more AAs, or via their own AAs. * these crosslinks are targeted by antibiotics(ie, penicillin) --> which disrupts the cell wall, lyses the cell and kills bacterium
How can bacteria be classified?
via Gram Staining.
gram-negative: thin peptidoglycan cell wall located btwn its two plasma membranes
- appear pink
- permeability: outer membrane > inner membrane
- has lipopolysaccharides-- works as protective barrier from Abs and antibiotics
gram-positive: thick peptidoglycan cell wall
- appears purple (bc thickness doesn’t let stain leak out)
What is the space btwn the cell wall and the plasma membrane?
What does it conatin?
Periplasmic space.
Contains proteins that help the bacteria acquire nutrition (eg, hydrolytic enzymes)
What some basic differences between prokaryotes and eukaryotes?
**
• Presence of complex membrane-bound organelles (they have things like smaller ribosomes though to translate proteins)
• Membrane-bound Nucleus:
- instead of a nucleus, proks have a single circular double stranded molecule of “naked” DNA. This joins with RNA and proteins to form a Nucleoid.
- euks have DNA coiled with histone proteins.
• Mitotic Division vs Binary Fission
Proks: mRNA does not undergo post-translational modifications.
Euks: mRNA undergoes splicing, addition of Pol-A tail and 5’ cap
What is Flagellar Propulsion on a gram-negative bacteria used for?
Flagellar Propulsion
- long, hollow, rigid cylinders made from flagellin protein
- rotate counterclockwise to propel bacterium in a single direction
- rotate clockwise to make bacterium tumble (change orientation)
- uses proton gradient energy
- directed movement toward substances that will promote survival and growth = Chemotaxis
Bacteria do not undergo mitosis or meiosis, instead they undergo what?
Explain the process.
Binary Fission.
- 2 DNA Pols begin at ORI on circle and move in opposite directions, making complementary DNA double stranded circles
- the cell then divides resulting in 2 genetically identical daughter cells
- exponential growth
Explain Conjugation
- CONJUGATIVE plasmid (possesses gene for sex pilus) transferred via sex pilus
- Can transfer an F plasmid = fertility factor because it codes for the sex pilus. A bacteria with the F factor is called F+, one without is F-
- F factor can be in the form of an episome (=integrated in chromosome) - Can transfer the R plasmid: donates resistance to antibiotics.
- if you prescribe multiple antibiotics at same time, you can develop super-bacterium which contain antibiotic resistances on 1+ R plasmids
What does it mean that a plasmid is extragenomic DNA?
= replicate independently from nuclear DNA
What is the cell wall of bacteria made of? (detail)
What are eukaryotic cell walls made of (if any)?
Peptidoglycan.
- consists of a series of disaccharide polymer chains with AAs. The chains are attached by an interbridge of more AAs, or via their own AAs. * these crosslinks are targeted by antibiotics(ie, penicillin) --> which disrupts the cell wall, lyses the cell and kills bacterium
Euks: if plants = cellulose. If fungi= chitin
Explain Transduction
transfer of genetic material by a virus. Capsid of a virus mistakenly encapsulates host cell DNA instead of its own
What is Flagellar Propulsion on a gram-negative bacteria used for?
What are flagella made of in Euks?
Flagellar Propulsion
- long, hollow, rigid cylinders made from Flagellin protein
- rotate counterclockwise to propel bacterium in a single direction
- rotate clockwise to make bacterium tumble (change orientation)
- uses proton gradient energy
- directed movement toward substances that will promote survival and growth = Chemotaxis
Euks: made of microtubules.
Bacteria do not undergo mitosis or meiosis, instead they undergo what?
Explain the process.
How do Euks divide?
Binary Fission.
- 2 DNA Pols begin at ORI on circle and move in opposite directions, making complementary DNA double stranded circles
- the cell then divides resulting in 2 genetically identical daughter cells
- exponential growth
Euks: mitosis
What are transposons?
Pieces of DNA that can jump from one place to another along genome using transposase to be removed and added
Nucleus
***
- like the brain
• compartmentalization and storage of genetic info other than in mitochondria - aqueous fluid inside called Nucleoplasm
- wrapped in Nuclear Envelope= double phospholipid bilayer which has Nuclear Pores
* DNA cannot leave nucleus, RNA can!
• Nucleolus: center of nucleus where rRNA is transcribed and the subunits of the ribosomes are assembled
What happens to a newly synthesized protein?
**
Depending on the protein’s final destination:
- translated on ribosome in cytosol and stay there (eg, enzymes of glycolysis, actin filaments in muscle)
OR
- from ribosome on outer surface of ER, feed into lumen of Endoplasmic Reticulum (ER) (eg, protein hormones like ACTH; bloodstream proteins like Albumin)
Describe the Rough Endoplasmic Reticulum (ER)
**
- a thick maze of membranous walls with some places where the ER lumen is contiguous with the outer layer of the nuclear envelope
- synthesizes all proteins that do not belong in the cytosol!
- has ribosomes on the cytosolic side where mRNA is translated
- signal sequence may be present on mRNA which directs the protein to the ER membrane for the completion of translation, and are propelled into the ER lumen as they are created
- *= movement of protein from cytosol to ER
What is the Golgi Apparatus?
What is the process whereby newly synthesized proteins from the ER lumen go to it?
**
- series of flattened membrane bound sacs whose major functions are PACKAGING and SECRETING proteins
- Transport Vesicles bud off from the ER and carry them across cytosol to cis face of Golgi.
What does the Golgi do with the vesicles it receives?
(Trafficking of Secretory Proteins)
**
- organizes, concentrates and modifies the proteins as they are shuttled by transport vesicles like an assembly line from one compartment to the next
- ex, glycosylation, removal of AAs
- then the vesicles are expelled by the trans face of Golgi as secretory vesicles… the cell will release the proteins [SECRETORY]
OR - then the vesicles will be released from Golgi to mature into lysosomes
OR - they’ll be transported to other parts of cell (ex, mitochondria or back to ER)
Transport and Fate of Lysosomal Proteins
***
ER lumen –> cis-Golgi –> trans-Golgi –> lysosome
- lysosomes= membrane-bound vesicles containing hydrolytic enzymes which breakdown macromolecules (taken into the cell by endocytosis) via hydrolysis ideally in acidic conditions
- they’ll use these to breakdown old or damaged organelles; or digest the incoming phagocytes
- if they rupture, they kill the cell
- they exist mostly in cells that are about to undergo apoptosis
Trafficking of Secretory Proteins
How does this process actually aid the cell
***
ER lumen –> cis-Golgi –> trans-Golgi –>secretory vesicle
- secretory vesicles contain enzymes, growth factors or ECM components
- released through exocytosis (where the vesicle membrane is incorporated into the cell membrane) – so they supply the membrane with its integral proteins and lipids + membrane expansion
- secretory vesicles are constitutively secreted (released continuously) OR they’ll be released in response to chemical or electrical stimuli (regulated secretion)
- some proteins are activated within secretory vesicles (ex, Proinsulin cleaves to Insulin only after the vesicle buds off the Golgi)
** Endocrine Glands (ex, pituitary and pancreas) and the Liver use this secretion path! (like you’ll see that the cells in these organs have ER and Golgi and do this)
How does Endocytosis aid the cell?
**
The newly formed vesicles (which have just taken some cell membrane) enter and go to Golgi for recycling of the membrane. So when secretory vesicles are made again, the cell membrane gets a fresh batch.
When you see smooth ER, what should you think about?
***
Lipid Metabolism and Storage; and Detoxification.
= portion of ER that lacks ribosomes
- (in smooth muscles, it’s called the Sarcoplasmic Reticulum)
Lipid Metabolism: in liver, triglycerides are made here and these lipids are stored as Adipocyte cells (contribute to energy storage and body temp) here.
Detoxification: it oxidizes foreign substances
