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Prokaryotic Cell Biology and Plasmid DNA Isolation
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Prokaryotic Cell Biology and Plasmid DNA Isolation
Prokaryotic Cell Biology and Plasmid DNA Isolation
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1
Question
What is considered the structural and functional unit of the cell?
2:07
Answer
The cell is the basic structural and functional unit of all living organisms.
2
Question
How do prokaryotic and eukaryotic cell sizes generally compare?
4:34
Answer
Prokaryotic cells are typically in the micrometer range, while eukaryotic cells are much larger, reaching up to 40 micrometers in diameter.
3
Question
How is the genetic material organized in a typical prokaryotic cell?
5:04
Answer
It consists of a circular DNA molecule present freely in the cytosol, not bound within a membrane.
4
Question
How does the origin of replication compare between prokaryotes and eukaryotes?
5:56
Answer
Prokaryotes have a single origin of replication, whereas eukaryotes have multiple origins of replication.
5
Question
What is the primary difference in ribosomal size between prokaryotes and eukaryotes?
7:35
Answer
Prokaryotes possess 70S ribosomes, while eukaryotes possess 80S ribosomes.
6
Question
Why do prokaryotes perform transcription and translation simultaneously?
7:56
Answer
Because they lack a membrane-bound nucleus, allowing the cytosol to house both genomic material and the translational machinery.
7
Question
Which organisms possess a cell wall among eukaryotic types?
7:18
Answer
Plants and fungi have cell walls, whereas animal cells do not.
8
Question
What process involves directed bacterial motion toward a chemical gradient?
10:55
Answer
Chemotaxis.
9
Question
What is the main protein component of the bacterial flagellum?
12:57
Answer
Flagellin.
10
Question
What is the primary function of the bacterial capsule?
14:26
Answer
It serves as a protective outermost layer made of high molecular weight polysaccharides that prevents damage from external chemicals.
11
Question
What two sugar molecules constitute the peptidoglycan polymer?
17:27
Answer
N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
12
Question
How does lysozyme act on the bacterial cell wall?
19:40
Answer
It degrades the peptidoglycan layer by cleaving the beta 1,4 glycosidic bond connecting NAG and NAM.
13
Question
Which specific cell wall component is unique to gram-positive bacteria?
21:36
Answer
Lipoteichoic acid.
14
Question
What are lipopolysaccharides (LPS) and where are they found?
21:50
Answer
LPS are important antigenic determinants located exclusively in the gram-negative bacterial cell wall.
15
Question
What is a plasmid in a bacterial cell?
24:23
Answer
It is an extra-chromosomal, circular DNA molecule that exists independently of the main bacterial chromosome.
16
Question
Why is the exchange of plasmids between bacterial species a clinical concern?
24:48
Answer
It facilitates the rapid spread of antibiotic resistance genes across bacterial populations.
17
Question
What are the three conformational forms of plasmid DNA?
27:47
Answer
Covalently closed circular (CCC), open circular (OC), and supercoiled forms.
18
Question
What is the specific action of the enzyme DNA gyrase on plasmids?
28:11
Answer
It introduces additional turns into circular DNA to adopt the supercoiled conformation.
19
Question
What is the primary function of the origin of replication on a plasmid?
29:22
Answer
It acts as the starting site for the DNA replication machinery of the host bacteria.
20
Question
Which method is commonly used for plasmid DNA isolation?
31:38
Answer
Alkaline lysis method.
21
Question
During alkaline lysis, what happens to genomic DNA upon neutralization?
32:24
Answer
It fails to renature properly and is discarded as a precipitate.
22
Question
What is the function of the phenol-chloroform solution in plasmid purification?
33:04
Answer
It is used for deproteinization to remove proteins and yield high-purity plasmid DNA.
23
Question
Why must the alkaline lysis step last no longer than five minutes?
38:39
Answer
Excessive exposure to strong alkaline conditions will degrade plasmid DNA and cause genomic DNA contamination.
24
Question
What is the primary difference between manual alkaline lysis and commercial kit-based isolation?
43:28
Answer
Commercial kits utilize silica-based columns that bind plasmid DNA, whereas the manual method requires ethanol precipitation.
25
Question
What component is used in commercial kits to remove unwanted contaminants?
44:29
Answer
An extra wash buffer.
26
Question
Prokaryotic cell genomes do not contain non-coding regions known as _____.
7:30
Answer
introns
27
Question
How does the penicillin antibiotic work to kill bacteria?
19:34
Answer
It targets and inhibits the synthesis of the peptidoglycan cell wall.
28
Question
Which bacteria type has a thicker peptidoglycan layer?
17:07
Answer
Gram-positive bacteria.
29
Question
What defines the open circular (OC) form of a plasmid?
27:24
Answer
A configuration resulting from a nick in one of the strands of the circular DNA.
30
Question
What is the function of topoisomerase in regard to plasmid DNA?
28:42
Answer
It relaxes the turns in supercoiled DNA, converting it toward the covalently closed circular form.