answer

watching

views

aquamarinegoose0Lv1

28 Sep 2019

Porin-like structures are prevalent among Gram-negative bacteria. Why are these structures stable in the membrane? (Hint: Compared alpha helix and beta strand. Explain genetic economy.)

answer

watching

119

views

For unlimited access to Homework Help, a Homework+ subscription is required.

You have 0 free answers left.
Get unlimited access to 3.8 million step-by-step answers.

Get unlimited access

Already have an account? Log in

Casey DurganLv2

28 Sep 2019

Unlock all answers

Get 1 free homework help answer.

Already have an account? Log in

Related questions

The non-polar core of a membrane bilayer is found to be 3.4 nmin thickness. From studies of protein structure, we know that eachamino acid residue in a beta strand extends the length of thestrand by 0.35 nm on average (twists in the strand may cause somevariation in this length, but we will ignore these for now.) Usingthis information, answer the following questions:

a.What is the minimal number ofamino acids that must be found in a transmembrane ?-strand thatspans the non-polar core of the membrane? (Your answer should be awhole number.)

b. Porins are large channel proteins found in bacteria and inthe outer mitochondrial membranes of eukaryotes. The human porin(also known as the VDAC = voltage-dependent anion channel) has 19transmembrane ?-strands that form a ?-barrel. The porin protein isformed by 283 amino acids. Approximately what percentage of theamino acids (to the nearest whole number) are found in thetransmembrane segments?

c.At the N-terminus of thepolypeptide, there is a segment of 25 amino acids that extends outfrom the membrane and is not part of a ?-strand. Only 1 amino acidextends beyond the membrane surface at the C-terminus. Assumingthat the remaining amino acids form connecting loops of random coilbetween the ?-strands, on average, about how many amino acids arefound in each loop? (Your answer does not need to be a whole numberin this case, but do not exceed one decimal place.)

amethystmallard140

QUESTION 1

Which of the following statements about the bacterial cytoplasmic membrane is false?

	a.	It resists attachment of the bacterial chromosome to its inner surface.
	b.	It contains a protein complex that drives ATP synthesis.
	c.	It is asymmetric.
	d.	It consists of relatively equal amounts of phospholipids and proteins.

1 points

QUESTION 2

Which of the following statements regarding Mycobacteria is false?

	a.	The genome has relatively low Guanine (G) and Cytosine (C) content.
	b.	The cytoplasmic membrane is surrounded by a polymer (peptidoglycan) consisting of alternating N-Acetylglucosamine (NAG) and N-Acetylmuramic (NAM) acid units.
	c.	It infects approximately one-third of the global human population.
	d.	It has a Gram-positive cell wall with an additional waxy lipid layer of mycolic acid.

1 points

QUESTION 3

Which of the following outer membrane porins enables Mycobacteria to adapt to acidic and intracellular environments, and shows homology to outer membrane porin A?

	a.	OmpATb.
	b.	OmpA.
	c.	MspA.
	d.	Lipid A.

1 points

QUESTION 4

Based on your understanding of bacterial membranes, which of the following is not likely to be found in an E. coli outer membrane?

	a.	Membrane-anchored enzymes.
	b.	Mycolic acid.
	c.	Lipopolysaccharide.
	d.	Porin channels.

1 points

QUESTION 5

Based on the conclusions of this paper, which of the following statements would the author most likely disagree with?

	a.	Some archaeon do not contain all of the genes essential for life.
	b.	The membrane structures of prokaryotes show far greater diversity than those of eukaryotes.
	c.	As demonstrated in this definitive report, scientists have a great understanding of the majority of basic functions and evolution of bacterial membranes.
	d.	The outer membrane (and its associated components) of archaea, Gram-negative bacteria, and Gram-positive bacteria likely evolved independently of one another.

1 points

QUESTION 6

Which of the following is not true for Gram-negative, acid-fast, and archaeal membranes?

	a.	They modify their lipid content in response to environmental changes.
	b.	They have co-evolved the same outer membrane composition and structure.
	c.	They all have a cytoplasmic membrane.
	d.	Membrane transport proteins regulate nutrient uptake and waste removal.

1 points

QUESTION 7

Compared to Mycobacteria, Gram-negative bacterium contain:

	a.	More mycolic acid.
	b.	Pores of increased length.
	c.	Less peptidoglycan.
	d.	50-fold-lower numbers of porins.

1 points

QUESTION 8

Archaea are found to survive in strongly acidic lakes compared to bacteria and Eukaryotes. Which of the following supports this claim according to the study?

	a.	The presence of L-glycerol ether linked lipids in Archaea membranes.
	b.	The presence of D-glycerol ether linked lipids in Archaea membranes.
	c.	The presence of L-glycerol ester linked peptidoglycans in Archaea membranes.
	d.	The presence of L-glycerol ester linked lipids in Archaea membranes.

1 points

QUESTION 9

Based on your understanding of the symbiotic relationship between Nanoarchaeum equitans and Ignicoccus, which of the following below is not true?

	a.	The membrane lipids of N. equitans are synthesized by Ignoccocus.
	b.	In exchange for membrane lipids, N. equitans provide Ignicoccus with many essential cytoplasmic enzymes.
	c.	N. equitans lack enzymes capable of catalyzing lipid biosynthesis.
	d.	Intraperiplasmic vesicles produced by Ignicoccus allow for lipid transfer to N. equitans.

1 points

QUESTION 10

What is the role of hydrogen bonds in bacteria, as mentioned in the article?

	a.	They mediate transmembrane electron flow.
	b.	They mediate lipid biosynthesis.
	c.	They help to stabilize the cytoplasmic membrane.
	d.	They are responsible for the selective permeability of the cytoplasmic membrane.