Molecular Biology Flashcards
DNA of prokaryote
Single circular double stranded DNA concentrated in the nucleoid
Can the plasmid of prokaryote (bacteria/archae) replicate independently?
Yes
What is the difference between eukaryotic plasma membrane and prokaryotic plasma membrane?
Do all prokaryotes have cell membrane?
Eukaryotic plasma membrane has cholesterol to provide membrane integrity whereas prokaryotes have similar steroid-like molecule that function the same.
Prokaryotes have invaginations called mesosomes in their plasma membrane whereas eukaryotes do not.
Yes all prokaryotes have phospholipid bilayer membrane.
Structural difference between gram positive and gram negative bacteria
Gram positive bacteria have a thick PTG wall outside the plasma membrane whereas gram negative bacteria has a very thing layer of PTG outside plasma membrane and there is another layer of plasma membrane outside of this thin PTG.
What is a teichoic acid?
Teichoic acids are a protein molecule that extend to the surface of the gram positive bacterial cell. Only found in gram positive bacteria. “Wall”, it protects the bacteria. It protrudes to the surface of gram positive bacteria, stemming from either the plasma membrane or the thick layer of PTG.
What is lipopolysaccharides?
Lipopolysaccharides are polysaccharides that are present in the outer membrane of the gram negative bacteria, the outer membrane just outside the thin PTG cell wall. It stabilizes the membrane, and acts as an endotoxin to provide defense for the gram negative bacteria (protect from drugs, surface adhesion, structural integrity)
It has an O-antigen and elicits a strong immune response in animals
In peptidoglycan cell wall of gram positive and gram negative bacteria, what kind of linkage links the N-acetylglucosamine (G) and N-acetylmuramic acid (M)?
Beta (1,4) linkage
Propeller direction of bacterial flagella and the major protein component of bacterial flagella
Counter-clockwise
flagellin
In bacterial conjugation, what is the sex factor?
During conjugation, how is the F factor replicated?
Sex factor is a plasmid in a bacteria that allows the bacteria to form a sex pili (sex bridge) that transfer the genetic information to another bacterium.
The F factor replicates via the rolling circle mechanism of replication. The single stranded DNA is passed down first and as it is transferred to another bacterium, it begins and continues its replication process.
What happens when sex factor is integrated into the host chromosome through transformation?
The F factor is integrated into the bacterial chromosome and this host chromosome is transferred.
In eukaryotes, how is the DNA condensed? Explain “Beads on a string”, the structure of nucleosome and linker. Do prokaryotes have histones?
Nucleosome, 4 histones with DNA wrapped around it, are linked with a “linker” consisting of Histone 1 protein. H1 protein condenses the series of nucleosomes further, creating a 30nm chromatin fiber. This type of condensation of DNA is unique to eukaryotes only.
Explain the structure of different lipid structures: micelles, and liposomes.
Micelles: spherical structure where the polar heads are outside and the hydrophobic tails are congregated on the inside.
Liposomes: lipid bilayer folding onto itself forming a circle.
How does the speed of lateral diffusion differ from transverse diffusion in the phospholipid bilayer?
The speed of lateral diffusion is very fast whereas the speed of transverse diffusion is very slow. Transverse diffusion occurs rarely.
What is the difference between integral membrane proteins and trans-membrane proteins? What forces hold the integral membrane proteins embedded? What kind of conditions are required to remove them? And when these conditions do occur, what usually happens to the cell?
Trans-membrane protein is a sub-class of integral proteins that span the whole lipid bilayer. Integral membrane proteins are tightly bound to the membrane by hydrophobic forces and harsh conditions are needed to remove them. Once removed, the membrane is usually disrupted.
What forces keep the peripheral membrane proteins attached to the lipid bilayer?
Hydrogen bonding or electrostatic interactions. Removal of the peripheral membrane proteins occur in mild conditions and removal usually keeps the membrane intact.
