The Cell Flashcards
Difference between cytoskeletal structures of centrioles and flagella
Centrioles consist of nine triplets of microtubules around a hollow center
Flagella consist of nine doublets on the outside, with two microtubules on the inside
Predominant proteins of…
- Microfilaments
- Microtubules
- Intermediate filaments
Actin
Tubulin
Differ by cell type, but include keratin and desmin
Similarities between Archaea and bacteria vs Archaea and eukaryotes
Archaea are similar to bacteria in that both are single-celled organisms that lack a nucleus or membrane-bound organelles, contain a singular circular chromosome, divide by binary fission or budding, and overall share a similar structure.
Similar to eukaryotes in that they start translation with methionine, contain similar RNA polymerases, and associate their DNA with histones.
Structure of prokaryotic flagellum structure
Composed of a filament, a basal body, and a hook.
The filament is a hollow, helical structure composed of flagellin.
The basal body anchors the flagellum to the cytoplasmic membrane and is also the motor of the flagellum.
The hook connects the filament and the basal body so that it exerts torque on the filament, which can thereby spin and propel the bacterium forward.
Gram-positive cell walls
- Consists of a thick layer of peptidoglycan, a polymeric substance made from amino acids and sugars.
- May also made a pathogen by providing protection from a host organism immune system.
- Also contains lipoteichoic acid (function unknown, but the human immune system may be activated by exposure to these chemicals)
Gram-negative cell walls
- Very thin and also contain peptidoglycan, but in much smaller amounts
- cell walls of these bacteria directly abut the cell membrane
- also have outer membranes containing phospholipids and lipopolysaccharides (lipopolysaccharides are the part of the gram-negative bacteria that triggers an immune response in human beings)
Prokaryotic ribosome size vs eukaryotic ribosomes
Prokaryotic ribosomes: 30S and 50S subunits
Eukaryotic ribosomes: 40S and 60S subunits
Bacterial genetic recombination processes
Transformation, conjugation, transduction
Four phases of the bacterial growth curve
Lag phase, exponential phase, stationary phase, and death phase
Transformation
Results from the integration of foreign genetic material into the host genome. Frequently comes from other bacteria that, upon lysing, spill their contents in the vicinity of a bacterium capable of transformation.
Conjugation
Bacterial form of mating
- two cells form a conjugation bridge between them that allows for the transfer of genetic material
- plasmid can be transferred from F+ cells to F- cells, or a portion of the genome can be transferred from an Hfr cell to a recipient.
Transduction
Transfer of genetic material from one bacterium to another using a bacteriophage as a vector
Transposons
Genetic elements capable of inserting and removing themselves from the genome
Pathway of retroviral nucleic acids from infection of a host cell to release of viral progeny
The nucleic acid enters as single-stranded RNA which undergoes reverse transcription (using reverse transcriptase) to form double-stranded DNA. This DNA can enter the host genome and replicate with the host cell. The DNA is transcribed to mRNA, which can be used to make structural proteins. This mRNA doubles as the viral genome for new virions. Once new virions are assembled from the structural proteins and mRNA (single-stranded RNA) genome, the virions can be released to infect other cells.
Positive-sense RNA
Implies that the genome may be directly translated to functional proteins by the ribosomes of the host cell, just like mRNA
