answer all the questions ( you have to be sure ) 1- Select all that apply. Pure
ID: 87688 • Letter: A
Question
answer all the questions ( you have to be sure )
1- Select all that apply. Pure culture:
a- Rarely exists outside the lab
b- Can be determined by doing a streak plate for isolated colonies
c- As long as a bacterium grows on plates in the lab, it is considered to be a pure culture
d- Pure culture is only assumed to be present if all the colonies of the bacterium on the plate look the same.
-Some antibiotics attack peptidoglycan synthesis, killing the cell. Which of the following is an accurate statement? ( select all the correct )
A- Gram negative cells would be killed by this drug because their peptidoglycan wall is the outer layer of the cell envelope
b- Gram positive cells would be killed by this drug because their peptidoglycan wall is the outer layer of the cell envelope
c- Archaea don t have peptidoglycan and therefore wouldn t be affected by this drug.
d-
all are correct
3- Membranes are considered semi-permeable. For the following molecules, indicate which are able to pass freely through the membrane (F), and which are restricted (R) and may require a protein for transport.
Molecular oxygen, nitrogen, carbon dioxide ______
Large biological molecules such as proteins and carbohydrates _______
Glucose ________
Small charged molecules such as H+ _______
4- The correct way to write the name of a bacterium in the binomial system is
a- E. coli.
b- Escherichia coli.
c- Escherichia coli
d- Escherichia Coli.
a- Rarely exists outside the lab
b- Can be determined by doing a streak plate for isolated colonies
c- As long as a bacterium grows on plates in the lab, it is considered to be a pure culture
d- Pure culture is only assumed to be present if all the colonies of the bacterium on the plate look the same.
Explanation / Answer
Answer 1: a, b and d (As explained below)
Option a is true because, bacteria have the ability to organize themselves into multicellular communities and differentiate into specialized cell variants. This is, in fact, one of the survival mechanisms of bacteria. Option b is true because using streaking you can determine if culture is contaminated with other bacteria or is pure. Option c is not true because pure culture is not defined by virtue of its ability to grow on plates in the lab, but rather the characteristic of a culture that contains cells of one kind. And for that reason, the option d is correct.
Answer 2: a and c (As explained below)
Both Gram negative and Gram-positive bacteria bith have peptidoglycan membranes. However, the peptidoglycan layer in the Gram negative bacteria is very thin and so the action insignificant. The Archaea lack peptidoglycans.
Answer 3:
Molecular oxygen, nitrogen, carbon dioxide - F, since their size is small, also oxygen is nonpolar.
Large biological molecules such as proteins and carbohydrates - R, since their size is too big to pass through.
Glucose - R, these are also large in size, so cannot pass through membranes.
Small charged molecules such as H+ - R, ions require ionic channels and sometimes energy, as well.
Answer 4: c (As explained below)
The basic rules for writing the scientific name of bacteria are that the names of both genus and species name have to be included with the genus to be compulsorily capitalized and the species in all lowercase. The name can be abbreviated by writing just its initial, as in this case, E. for Escherichia. If we assume that the dots at the end of the first 2 options is are not full-stops, then we can go for the third option as our correct answer.
Also, pl. note that the binomial system does also mandates that the names be written in italics, which is not being shown here. So, we assume the question does not test for that here.
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