Prokaryotes

Question 1

Prokaryotes versus Eukaryotes

Answer 1

Prokaryotes: -smaller

• lack internal membrane system around organelles -cell size is 0.5-4.0 um wide
• spherical prokaryotes (coccus) are very small

Eukaryotes: -have inner membranes around organelles -cell size 10-20 um wide

Question 2

Coccus

Answer 2

spherical or oval shaped (little spheres)

diplococcus- 2 cocci linked together

streptococcus- chains of cocci linked together tetrad- 4 cocci group together

sarcinae- 8 cocci linked together

staphylococcus- many cocci bunched together in a bundle

Question 3

Bacillus

Answer 3

cylindrical rod shaped

diplobacilli- 2 bacilli

streptobacilli- chain of bacilli

palisade- several parallel cells lined up next to eachother

vibrios- comma shaped rods

Question 4

Spirillum

Answer 4

spiral shaped

spirilla- rigid helix

spirochetes- flexible helices

Question 5

Mycelium

Answer 5

network of long, multinucleate filaments

prefix: (-myces)

Question 6

Pleomorphic

Answer 6

organisms that are variable in shape

Question 7

Surface area to volume ratio and Growth Rates

Answer 7

small cells have more surface area relative to their volume than larger cells (larger S/V ratio) which means there is greater nutrient exchange per unit cell volume

-more area for exchange relative to volume allows small prokaryotes to grow and replicate faster than larger cells

Question 8

Functions of cell membrane (all domains)

Answer 8

• maintain cell’s integrity (separates cytoplasm from environment)
• regulates transport by being a highly selective permeable barrier
• energy metabolism in prokaryotes (not eukaryotes)
• proteins attachment (receptors/channels)
• receptors for detection and response to chemicals outside of cell

Question 9

General Structure of Domain Bacteria membrane

Answer 9

phospholipid bilayer plus proteins

-no sterols but contain hopanoids

Question 10

Membrane proteins (list)

Answer 10

Peripheral, Integral, Transmembrane

Question 11

Peripheral proteins (fluid mosaic membrane)

Answer 11

loosely connected to membrane on cytoplasmic side -easily moved

Question 12

Integral proteins (fluid mosaic membrane)

Answer 12

amphipathic (polar and nonpolar regions) -embedded within membrane and project outward or inward -carry out important functions

Question 13

Transmembrane proteins (fluid mosaic membrane)

Answer 13

completely crosses membrane from one side to the other

Question 14

Membrane strengthening lipids

Answer 14

sterols and hopanoids

-saturation levels of membrane lipids reflect environmental conditions such as temperature

Question 15

Sterols

Answer 15

• rigid, planar lipids found in eukaryotic membranes
• strengthen and stabilize membranes

Question 16

Hopanoids

Answer 16

• structurally similar to sterols
• present in membranes of many Bacteria

Question 17

Membrane fluidity

Answer 17

cell membrane has properties of both liquid and solid

-membrane needs to be at right fluidity which is temperature dependent

too cold= solidification (gelling)

too hot= thermal lysis (cell death)

Question 18

Adjusting to maintain correct membrane fluidity

Answer 18

• adjust fatty acid composition of phospholipids
  1. cold- more unsaturated fatty acids (minimize van der waals forces)
  2. hot- more saturated fatty acids (maximize van der waals forces *van der waals forces strength determines if fatty acid tails attract and stick to eachother or not
• adjust ratio of sterols, hopanoids, or other lipids in the membrane to maximize or minimize van der waals forces

Question 19

Transport in prokaryotes

Answer 19

active transport is always facilitated in prokaryotes

-no endocytosis/exocytosis in prokaryotes

Question 20

Group translocation

Answer 20

simultaneous transport and chemical modification of transported substance

-energy (ATP) dependent transport that chemically modifies molecule as it is brought into the cell

Question 21

Domain Bacteria Cell Walls

Answer 21

mostly structural polysaccharides and peptides/proteins -prevents osmotic lysis

-gram (+) and gram (-) cells

peptidoglycan- structural polysaccharide in cell walls of domain Bacteria

Question 22

Osmotic lysis

Answer 22

pressure from water entering cell causing a rupture of the cell membrane and death of the cell

Question 23

Breaking Bacterial cell walls

Answer 23

1. Lysozyme- breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid in cell wall
2. Penicillin- inhibits peptidoglycan synthesis of cell wall

*breakdown of cell wall causes influx of water to rush into the cell from the hypotonic environment outside the cell, causing the cell to burst through lysis

Question 24

Bacteria without cell wall

Answer 24

Mycoplasma: -does not produce a cell wall -plasma membrane stronger (has sterols) more resistant to osmotic pressure -hyper regulates internal solute concentration to stay slightly hypertonic (so cell doesn’t become dehydrated)

Question 25

Gram positive and Gram negative bacteria (quick facts and staining)

Answer 25

gram (+): stain purple, thick layer of peptidoglycan order- membrane, thick cell wall on outside gram (-): stain pink, thin peptidoglycan wall order- thin cell wall in between two membranes

Question 26

Peptidoglycan Cell Wall Structure

Answer 26

mesh-like polymer wall of identical subunits forming long strands (structural polysaccharide with amino acids surrounding cell) basic subunit- disaccharide of two alternating modified sugars (N-acetylglucosamine \*NAG and N-aceylmuramic acid \*NAM) joined by Beta glycosidic bonds

Question 27

Peptidoglycan Cross-linked strands

Answer 27

- strands have a helical shape - cross linked by covalent bonds between the tetrapeptides (4 amino acids) for strength - In gram (-) bacteria crosslinks are directly between amino acids in the tetrapeptide - In gram (+) bacteria, there are often interbridges of additional amino acids betwee the tetrapeptides

Question 28

Gram Positive Cell Walls

Answer 28

composed primarily (90%) of peptodoglycan -also contains large amounts of teichoic acids (negatively charged) Teichoic acids function to: help maintain cell envelope, may bind to host cells, and may store phosphate (PO₄) \*may attract cations - some gram (+) bacteria have layer of proteins on surface of peptidoglycan - also have lipoteichoic acid which attaches to cell membrane Picture: teichoic acid circled

Question 29

Periplasmic Space

Answer 29

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

Question 30

Gram Negative Cell Walls

Answer 30

consist of a thin layer of peptidoglycan surrounded by an outer and inner plasma membrane -outer membrane composed of phospholipids, lipoproteins, and lipopolysaccharides \*Lipopolysaccharides- make up the outer part of outer membrane (no phospholipid heads) \*NO TEICHOIC ACIDS -peptidoglycan is 5-10% of cell wall Periplasmic space: many enzymes present in periplasmic space (transport proteins) -Braun's lipoproteins connect outer membrane to peptidoglycan wall

Question 31

Lipopolyssaccharides (LPS)

Answer 31

- contributes to negative charge on outer cell membrane surface - helps stabilize outer membrane structure - may contribute to attachment to surfaces and biofilm formation - creates a permeability barrier

Question 32

Gram-Negative Outer Membrane Permeability

Answer 32

-more permeable than plasma membrane due to presence of porin proteins and transporter proteins \*porin proteins form channels to let small molecules pass

Question 33

Mechanism of Gram Stain Reaction

Answer 33

gram stain reaction due to nature of cell wall - shrinkage of the pores of peptidoglycan layer of gram-positive cells (constriction prevents loss of crystal violet during decolorization step) - thinner peptodoglycan layer and larger pores of gram (-) bacteria does not prevent loss of crystal violet

Question 34

Structures Exterior to Cell Wall

Answer 34

glycocalyx, capsule, slime layer

Question 35

Glycocalyx

Answer 35

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

Question 36

Capsule

Answer 36

dense, tightly attached, regular arrangement of polysaccharides \*visible to light microscope

Question 37

Slime layer

Answer 37

diffuse, loosely attached, irregular arrangement of polysaccharides functions: attachement to solid surfaces, reserve source of energy, anti-phagocytic for some pathogens, prevents virus attachement \*may aid in motility