Cell Wall Structure

Question 1

What is the concept of life?

Answer 1

Self Duplication, Replicate informational molecules.

A way to extract energy from the environment and use it to grow and replicate.

Question 2

What is Partitioning?

Answer 2

Separation of living from the enviro-requires non-randomness-living must separate from entropy of non-living chemistry and physics of enviro

Question 3

What is the concept of cell?

Answer 3

Model for all life on earth

Question 4

Functions of Cell Wall

Answer 4

1. Rigidity, Osmotic integrity
2. Sieving
3. Catalytic center

Question 5

Structure of Peptidoglycan

Answer 5

Linear strand of 2 alternating sugars
Lactic acid side group
Lysozyme-sensitive glycosidic bond
Tetramer linear peptide side chain
Cross linking for structural integrity against osmotic lysis
DAP-NH2>COOH D-ala 
Gram + extra peptide bridge

Question 6

What does glycan do? In gram - vs gram +?

Answer 6

Glycan forms threat around cell body

One layer around gram - and multi-layers around gram +

Question 7

What are the variations in peptide?

Answer 7

• Sometimes lysine instead of DAP
• Sometimes hydroxylated glutamate instead of glutamate
• Much interbridge variation
• No variation in (NAG-NAM)x

Question 8

What do Archaea walls look like?

Answer 8

• Rigid
• More variation in structures than bacteria
• Pseudo PG-diff carbs, glycosidic bond, aa
• Some have no PG-like structure
• Halococcus sulfated sugars and acids

Question 9

Archaea S-Layer

Answer 9

Most common type of cell wall

-All protein: identical subunits arranged in a crystalline array.

Question 10

Gram + Cell Wall Components: Teichoic acids

Answer 10

• Neg. charge, covalently bound to either peptidoglycan or plasma membrane
• Makes surface polar, acidic
• Inhibits entry of hydrophobic solutes
• Reservoir for Mg2+
• Regulates peptidoglycan synthesis
• Attachment to host cells
• Acid tolerance

Question 11

Gram +: Teichuronic Acids

Answer 11

• Substitute for teichoic acids in some species
• Complex carbs
• Neg. charged, acidic

Question 12

S-Layer in Bacteria

Answer 12

• Same concept as archaea – crystalline array of pure protein
• Outermost layer of cell wall
• Often has carbohydrate attached
• Function: resistance to proteinases, denaturants, phages and phagocytic immune cells

Question 13

Capsule

Answer 13

• Not attached to wall – outside of cell wall
• Polysaccharide composition
• Not a pure substance – often contains different kinds of polysaccharides and glycoproteins
• Capsule production depends on growth medium

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Question 14

Function of Capsule

Answer 14

1. Protection – excludes high MW solutes, antiphagocytic
2. Attachment – binds to specific tissue in animals and plants (see figure)
3. Antidessication – very hydrated. Difficult to remove bound H2O

Question 15

Flagella Structure and Function

Answer 15

• Long, thin appendages
• Not straight, but helical in shape
• Diff. arrangements on cell body
• Polymeric protein composed of flagellin
• Attached to PM by complex of proteins that are attached to protein motor
• Function=motility

Question 16

Pili Structure and Functions

Answer 16

• i.e. fimbriae
• Shorter, more numerous on cell than flagella
• Various functions-conjugation, motility (jerky movements), attachment to surfaces (inanimate, host cells, biofilms)