Chapter 3

Question 1

Prokaryotes differ from eukaryotes

Answer 1

in size and simplicity. most lack internal membrane systems and no internal phospholipid bilayer membrane.

Question 2

coccus

Answer 2

spherical or ovoid

Question 3

bacillus

Answer 3

cylindrical shape

Question 4

spirilum

Answer 4

spiral shape, rigid helices

Question 5

vibrios

Answer 5

resemble rods, comma shaped

Question 6

spirochetes

Answer 6

flexible helices

Question 7

mycelium

Answer 7

network of long, multinucleate filamentous cells.

Question 8

pleomorphic

Answer 8

organisms that are variable in shape

Question 9

advantages of being small

Answer 9

small cells have more surface area relative to cell volume than large cells.this allows greater nutrient exchange per unit cell volume. thus, small cells tend to grow faster than larger cells,

Question 10

Fluid Mosaic Model

Answer 10

membrane somewhat fluid, somewhat solid. Lipid bilayers with floating proteins. Amphipathic lipids- polar ends (hydrophilic interact with water). non polar tails (hydrophobic insoluble in water). Membrane proteins.

Question 11

Composition of Membrane

Answer 11

general structure is phospholipid bilayer plus proteins (6- nm wide), no sterols, but +- hopanoids or other molecules.
Conatin both hydrophobic and hydrophilic component.
Can exist in many different chemical forms as a result of variation in the groups attached to the glycerol backbone. Fatty acids point inward to form hydrophobic env, hydrophilic portions remain exposed to external env or the cytoplasm

Question 12

membrane proteins

peripheral

Answer 12

loosely connected to membrane on cytoplasmic side, easily removed

Question 13

membrane proteins

integral

Answer 13

amphipathic-embedded to membrane on cytoplasmic side, easily removed.
carry out important functions
may exist ass microdomains

Question 14

Transmembrane proteins

Answer 14

completely crosses membrane from one side to the other

Question 15

Sterols

Answer 15

rigid, planar, lipids found in eukaryotic membranes. strengthen and stabilize membranes. only found in a very few prokaryotes

Question 16

hopanoids

Answer 16

structurally similar to sterols. present in membranes of many bacteria

Bacterial membranes lack sterols but do contain sterol like molecules, hopanoids stabilize membrane, found in petroleum

Question 17

Passive transport

Answer 17

transport which does not require ATP or other cellular energy to be used by the cell

Question 18

active transport

Answer 18

transport which requires the cell to expend its own energy in the form of ATP

Question 19

simple transport

Answer 19

transport which does not require a transport protein

Question 20

facilliatated transport

Answer 20

transporter which requires a transport protein. common in eukayotes, less common prokaryotes. in direction of concentration gradient

Question 21

diffusion

Answer 21

the movement of a molecule due to its inherited kinetic energy from a region where it is in higher concentration to a region of lower concentration (passive)

Question 22

osmosis

Answer 22

the diffusion of water across a membrane (passive)

Question 23

Receptor mediated transport systems-

Answer 23

ligand binds specific protein receptors on cell surface

• show saturation effect.
• highly specific

Question 24

group translocation

Answer 24

simultaneous transport and chemical modification of transported substance.
Energy dependent transport that chemically modifies molecule as it is brought into cell. Best known translocation system is phosphoenolpyruvate: sugar phosphotransferase systems (PTS)

Question 25

Hypotonic environments

Answer 25

solute concentration outside the cell is less than inside the cell, and water concentration is higher. water moves into cell and cell swells. cell wall protects from lysis

Question 26

Osmotic lysis

Answer 26

pressure from water entering cell causes a rupture of the cell membrane and death of the cell. In unicellular and colonial prokaryotes, the primary function of the cell wall is to prevent osmotic lysis

Question 27

hypertonic environments

Answer 27

solute concentration outside the cell is greater than inside, water concentration lower, water leaves the cell, plasmolysis occurs

Question 28

Protective nature of cell wall

Answer 28

lysozyme breaks the bond between n-acetyl glucosamine and n-acetylmurmic acid. Penicillin inhibits peptidoglycan synthesis. If cells are treated with either of the above they will lyse if they are in hypotonis solution

Question 29

mycoplsma

Answer 29

does not produce a cell wall. plasma membrane stronger(with sterols) more resistant to osmotic pressure. hyper regulates internal solute conc.

Question 30

gram positive

Answer 30

stain purple, thick layer of peptidoglycan

Question 31

gram negative

Answer 31

stain pink or red, thin peptidoglycan and outer membrane

Question 32

peptidoglycan

Answer 32

(murein) the structural polysaccharide in the cell walls of domain bacteria prokaryotes

Question 33

peptidoglycan structure

Answer 33

mesh like polymer of identical subunits forming long strands, a structural polysaccharide with amino acids that surrounds the cell. Basic subunit is a disaccharide of two alternating modified sugars joined by Beta glycosidic bonds (NAG and NAM). alternating D and L amino acids in a tetrapeptide (4 amino acids) attached to muramic acid that forms cross links with other tetrapeptides.

Question 34

periplasmic space

Answer 34

lies between plasma membrane and cell wall and is smaller than that of gram negative bacteria. periplasm has relatively few proteins. enzymes secreted by gram positive bacteria are called exoenzymes (aid in degradation of large nutrients)

Question 35

gram negative cell walls

Answer 35

consist of a thin layer of peptidoglycan surrounded by an outer membrane. outer membrane composed of phospholipids, lipoproteins and lipopolysaccharides. no teichoic acids. peptidoglycan is 5-10% of cell wall weight and in periplasmic space. Outermembrane lies outside the thin peptidoglycan layer. braun’s lipoproteins connect outer membrane to peptidoglycan.

Question 36

gram positive cell walls

Answer 36

composed primarily 90% of peptidoglycan. contains large amounts of teichoic acids (help maintain cell envelope, may bind to host cells, may store PO4, may attract cations). Some gram positive bacteria have layer of proteins on surafec of peptidoglycan. Lipoteichoic acid which attches wall to cell membrane.

Question 37

lipopolysaccharides

Answer 37

consists of 3 parts.
1. lipid A (endotoxin)
2. core polysaccharide
3. O side chain (O antigen)
lipid a embedded in outer membrane, core polysaccharide, O side chain extend out from the cell

Question 38

Importance of lipopolysaccharides

Answer 38

contributes to negative charge on cell surface, helps stabilize outer membrane structure, may contribute to attachment to surfaces and biofilm formation, creates a permeability barrier, protection from host defenses (o antigen), can act as an endotoxin (lipid a)

Question 39

Glycocalyx

Answer 39

polysaccharide rich (glucose or modified glucose subunits) material exterior to cell wall, sometimes has protein component (2 types-capsule, slime layer)

• capsule-dense, tightly attached, regular arrangement of polysaccharides, visible to light microscope
• slime layer- diffuse, loosely attached, irregular arrangement of polysaccharides
  functions: attachment to solid surfaces, antidessicant, reserve source of energy, antiphagocytic for some pathogens, prevents virus attachment

Question 40

S Layer

Answer 40

Regurlary structured layers of protein or glycoprotein that self assemble.
In gram negative bacteria the S layer adheres to outer membrane. In gram positive bacteria it is associated with the peptidoglycan surface.

Question 41

S Layer Functions

Answer 41

protect from ion and pH fluctuations, osmotic stress, enzymes, and predation. Maintains shape and rigidty, promotes adhesion to surfaces, protects from host defenses, potential use in nanotechnology, s layer spontaneously associates