BIO 3124 Lecture Notes - Lecture 5: Phospholipid, Archaea, Galactosamine

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6 Jan 2015

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Provide structure and shape and protect the cell from osmotic forces. Assist some cells in attaching to other cells or in resisting anti-microbial drugs. Can target the cell wall of bacteria with antibiotics. Anti-biotics inhibit peptidoglycan synthesis and therefore, cell wall synthesis. Humans do not have peptidoglycan cell walls and are not affected. Made up of a polymer of 2 repeating sugar derivatives: n-acetylglucosamine (nag, n-acetylmuramic acid (nam) They are linked via a b-1,4 glycosidic bond. The peptide linkage of muramic acid residues confer added strength. Peptides include l-alanine, d-glutamic acid, d-alanine and are found in all peptidoglycan. D-forms of amino acids are not typically found in proteins but are found in the cell walls of bacteria. Diaminopimelic acid (dap) is found in gram negative bacteria. Gram-positive cross links can occur through a short interbridge of amino acids (e. g. : l-lysines and l-alanines)

Related Questions

Hi I need help with two Molecular Biology Questions

1. Bacteria are protected from increases in osmotic pressure bytheir cell walls. A major structural component of the cell wallresponsible for its protective properties is the polysaccharidepeptidoglycan. Which of the following best explains the rigidityand strength of the bacterial cell wall (choose all thatapply)?

A) Peptidoglycan forms linear, parallelstrands
B) Neighboring peptidoglycan strands are linked by peptidebonds
C) Peptidoglycan forms a highly branched structuredue to its alpha 1,6 glycosidic linkages.
D) The glycosidic linkages between themonosaccharide building blocks in peptidoglycan are extraordinarilystrong.
E) The polysaccharides in peptidoglycan formhelical structures, as in cellulose.

2. Pure cellulose from the seed threads of cotton is tough,fibrous, and completely insoluble in water. In contrast, glycogenfrom muscle or liver disperses readily in hot water to make aturbid solution. Although markedly different in physicalproperties, both substance are composed of (1-> 4) linkedD-glucose polymers of comparable molecular weight. Which of thefeatures below are responsible for the difference in physicalproperties of these glucose polymers (choose all that apply)?

A) Glycogen also has (1-> 6) linkages
B) The glycosidic linkages in cellulose are beta linkages whichresult in the formation of extended linear strands
C) Glucose monomers in glycogen are linked by alpha linkages whichcause a bend in the chain and prevent formation of longfibers
D) Parallel cellulose fibers are linked by hydrogen bonds, creatingtightly associated durable fibers.
E) Many of glycogenâs hydroxyl groups are exposed to water

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26.The best microscopy technique for observing different subcellular structures on the surface of bacteria is

(A) SEM (B) TEM

(E) fluorescence microscopy

27.Which type of microscopy exploits differences in the refractive index of the specimen, where light is retarded by one-quarter of a wavelength when it passes through a bacterial cell?

(A) SEM (B) TEM

(E) fluorescence microscopy

28.Which type of microscopy should be used to examine bacterial cells that have been Gram stained?

(A) TEM (B) fluorescence microscopy

(E) bright-field microscopy

29.Which of the following is most abundant in a prokaryotic cell (in dry weight)?

(A) RNA (B) DNA

(E) Lipid

30.Which of the following techniques uses the Svedberg unit (S)?

(A) electron microscopy (B) ultracentrifugation

(E) sonication

31.Which of the following is NOT a function performed by the cell membrane or its components?

(A) production of proteins (B) detection of environmental signals

(E) B and D

32.Which of the following statement is true?

(A) Lipopolysaccharides (LPS) are found in the cell wall of Gram-negative bacteria.

(B) Lipopolysaccharides (LPS) are found in the cell wall of Gram-positive bacteria.

(D) Teichoic acids are found in the cell wall of Gram-positive bacteria.

(E) Cholesterol is found in the cell wall of Gram-negative bacteria.

33.Which of the following is found in Archaeabut not in Bacteria?

(A) Hopanoids (B) Terpenoids

(E) Peptidoglycan

34.The glycan chain of archaeal cell wall is made of __________ and __________, while the glycan chain of bacterial cell wall is made of __________ and __________.

(A) peptidoglycan and murein, pseudopeptidoglycan and murein

(B) N-acetylglucosamine and N-acetyltalosaminuronic acid,

N-acetylmuramic acid and N-acetyltalosaminuronic acid

N-acetylglucosamine and N-acetylmuramic acid

(D) N-acetylglucosamine and N-acetylmuramic acid,

N-acetylglucosamine and N-acetyltalosaminuronic acid

(E) N-acetylmuramic acid and N-acetyltalosaminuronic acid,

N-acetylglucosamine and N-acetyltalosaminuronic acid

35.The sacculus of bacteria is composed primarily of

(A) phospholipids (B) peptidoglycans

(E) nucleic acids

36.Lysozyme attacks the following linkage in the bacterial cell wall:

(A) Î²(1,4)-glycosidic bonds

(B) Î²(1,3)-glycosidic bonds

(D) Peptide cross-links between glycan chains

(E) Peptide bonds between L-alanine and D-glutamic acid

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.

BIO 3124 Lecture Notes - Lecture 5: Phospholipid, Archaea, Galactosamine

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