Ch. 3 - Bacterial Cell Structure Flashcards
(63 cards)
1
Q
Pleomorphism
A
•variations in size and shape among cells of a single species
2
Q
Peptidoglycan
A
• main component of bacterial cell walls • A complex of sugars and amino acids • two types based on Gram stain: 1) gram positive - stain purple; thick 2) gram negative - stain pink; thin
3
Q
Mycelium
A
- A possible shape of bacteria
* network of long, multinucleate filaments
4
Q
Pleomorphic
A
• organisms that are variable in shape
5
Q
Smallest bacteria size
A
0.3 micro meters (Mycoplasma)
6
Q
Average bacteria size
A
1.25 x 2 to 6 micro meters (E. Coli)
7
Q
Very large bacteria size
A
600 x 80 micro meters (Epulopiscium fishelsoni)
8
Q
Three general shapes of bacteria
A
- coccus - spheres, oval, bean-shaped, pointed
- bacillus - cylindrical
- spirillum - rigid helix
9
Q
Bacterial cell organization common features
A
- cell envelope - 3 layers
- cytoplasm (plasma membrane)
- external structures
10
Q
Bacterial cell envelope 3 layers
A
- plasma membrane
- cell wall
- layers outside cell wall
11
Q
Bacteria plasma membrane functions
A
• encompasses the cytoplasm • selectively permeable barrier • interacts with external environment -receptors for detection of and response to chemicals in surroundings -transport systems -metabolic processes
12
Q
Periplasmic space
A
- found in gram negative bacteria between the plasma membrane and outer membrane
- sometimes observed between the plasma membrane and cell wall in gram-positive bacteria
13
Q
Peptidoglycan main components
A
•sugars and amino acids
14
Q
Coccus
A
• spherical, oval, been shaped, pointed
15
Q
Bacillus
A
•Cylindrical, Rod shaped
16
Q
Spirillum
A
• rigid helix
17
Q
Streptococcus
A
•Long chains of cocci (spherical shapes)
18
Q
Staphylococcus
A
• divide in random planes to generate irregular, grapelike clumps
19
Q
Cell wall
A
• layer that lives just outside the plasma membrane
20
Q
Cell wall functions
A
- maintains shape of the bacteria
- helps protect Cell from osmotic lysis
- helps protect from toxic materials
- May contribute to pathogenicity
21
Q
Peptidoglycan structure
A
• mesh like polymer of identical subunits forming long strands
-2 alternating sugars:
•N-acetylglucosamine (NAG)
•N-acteylmuramic acid (NAM)
-alternating D- and L- amino acids
22
Q
Peptide interbridge
A
- crosslink sugars together in peptidoglycan structure
* A component of peptidoglycan which connects one sugar polymer to another
23
Q
Teichoic acid
A
- found only in gram-positive cell walls
- extend to surface of the peptidoglycan
- negatively charged and help give the cell wall it’s negative charge
- help maintain cell envelope
- protect from environmental substances
- made bind to host cells
- contribute to acidic charge on cell surface of gram-positive
24
Q
Exoenzymes
A
- enzymes secreted by gram-positive bacteria
* Aid in degradation of large nutrients, ex: Mucinase, keritinase
25
Gram-positive cell walls
* composed primarily of peptidoglycan
* May also contain teichoic acids
* some have layer of proteins on the surface of peptidoglycan
26
Gram-negative cell walls
• more complex than gram-positive
• consists of a thin layer of peptidoglycan surrounded by an outer membrane
• outer membrane composed of lipids, lipoproteins, and lipopolysaccharides (LPS)
• no techoic acids
• peptidoglycan is 5 to 10% of cell wall wait
• Periplasmic space may constitute 20 to 40% of cell volume
• many enzymes present and periplasm
-hydrolytic enzymes, transport proteins, and others
27
Brauns lipoproteins
* found in gram-negative cell walls
| * Connect outer membrane to peptidoglycan
28
Importance of LPS
* 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 endotoxin (lipid A)
29
Permeability of gram-negative outer membrane
* more permeable then plasma membrane due to presence of porin proteins in transporter proteins
* porin proteins form channels to let small molecules pass
30
Mechanism of Gram stain reaction
* stain with Violet which is positively charged and attracts to negatively charged bacteria
* iodine added for dye retention
* decolorization with ethanol
* safranin
31
Hypotonic environment
* solute concentration outside the cell is less than inside the cell
* water moves into cell and cell swells
* cell wall protects from lysis
32
Hypertonic environment
* solute concentration outside the cell is greater than inside
* water leaves the cell
* plasmolysis occurs
33
Capsule
```
• located outside of the cell membrane in bacterial cells
• well organized and not easily removed from cell
• usually composed of polysaccharides
• visible in light microscope
•advantages:
-resistant to phagocytosis
-protect from desiccation
-exclude viruses and detergents
```
34
Slime layer
* similar to capsules except diffuse, unorganized and easily removed
* slime may aid in motility
35
Glycocalyx
* refers to a layer consisting of a network of polysaccharides extending from the surface of the cell
* can include both capsules and slime layers because they usually are composed of polysaccharides
* aids in attachment to solid surfaces including tissue surfaces in plants and animal hosts
36
Similarities between eukaryotic and bacterial cell membranes
* bilayer of lipids
* fluid
* contains integral proteins
* composed of primarily of lipids
37
S layer
* regularly structured layers of proteins or glycoprotein that self assemble
* gram-negative: adheres to outer membrane
* gram-positive: associated with peptidoglycan surface
38
S layer functions
```
• protect from ion and pH fluctuations, osmotic stress, enzymes, and predation
• maintains shape and rigidity
• promotes adhesion to surfaces
• protects from host defenses
• potential use in nanotechnology
- S layer spontaneously associates
```
39
Bacterial cytoplasmic structures
* cytoskeleton
* Intracytoplasmic membranes
* inclusions
* ribosomes
* Nucleoid and plasmids
40
Protoplast
•The plasma membrane and everything within
41
Cytoplasm
• The material bounded by the plasma membrane; thus a major part of the protoplast
42
Functions of cytoskeleton proteins
* participate in cell division
* localize proteins to certain sites in the cell
* determine cell shape
* some appear to be unique to bacteria
43
Endospore
* dormant cells formed within a so-called mother cell
* fascinating bacterial structures only produced by certain members of Bacillus and clostridium (rods) and sporosarcina (cocci)
* resistant to many very hostile environments
44
Fimbriae
* Aid in motility
* Aid in the uptake of DNA
* Aid in attachment to surfaces
45
plasmids
• extrachromosomal DNA
-found in bacteria, archaea , some fungi
-usually small, closed circular DNA molecules
• exist and replicate independently of chromosomes
-episomes - may integrate into chromosome
-inherited during cell division
• contain few genes that are nonessential
-confer selective advantage to host
• classification based on mode of existence, spread, and function
46
Plasma membrane functions
• selectively permeable barrier: they allow particular ions and molecules to pass either in or out of the cell while preventing movement of others
•metabolic processes:
-respiration
- photosynthesis
-synthesis of lipids and cell wall constituents
47
Ribosome
• responsible for protein synthesis
48
Methods of motility for bacteria
* swimming
* swarming
* corkscrew movement
* twitching
* gliding
49
Fluid Mosaic model
• describes the way in which lipids behave in a membrane
50
Bacterial plasma membrane proteins
```
• peripheral
-loosely connected to membrane
-easily removed
• integral
-amphipathic - embedded within membrane
-Carry out important functions
```
51
Hopanoids
* similar to our cholesterol
* stabilizes membrane and makes it stronger
* found in petroleum
52
Macroelements that help uptake of nutrients
•C, H, O, N, P, S
- found in organic molecules such as proteins, lipids, carbs, and nucleic acids
• K, Ca, Mg, and Fe
- cations and serve in variety of roles including enzymes, biosynthesis
• required in large amounts
53
Micronutrients that help uptake of nutrients
* Mn, Zn, Co, Mo, Ni, and Cu
* required in trace amounts
* often supplied in water or in media components
* Ubiquitous in nature
* serve as enzymes and cofactors
54
Characteristics of growth factors that help uptake of nutrients through barrier
* organic compounds
* essential cell components that the cell cannot synthesize
* must be supplied by environment if cell is to survive and reproduce
55
Classes of growth factors
```
• amino acids
-needed for protein synthesis
• purines and pyrimidines
-needed for nucleic acid synthesis
• vitamins
- function as enzyme cofactors
• heme
-iron-based groups
```
56
Transport mechanisms of microorganisms
* facilitated diffusion
* Active transport
* Group translocation -bacteria and Arcaea
* endocytosis - bacteria cannot do this
57
Passive diffusion
* molecules move from region of higher concentration to one of lower concentration between the cells interior and exterior
* H2O, O2, CO2 often move across membranes this way
* no energy required
58
Facilitated diffusion
• similar to passive diffusion
-Direction of movement is from high concentration to low concentration
•Differs from passive diffusion
-uses membrane-bound carrier molecules (permeases)
-smaller concentration gradient is required for significant uptake of molecules
-effectively transports glycerol, sugars, and amino acids
59
Active transport
```
• Energy required
• move molecules from low to high concentration gradient
• limits how quickly this can happen
• involves carrier proteins (permeases)
• 3 types:
1) ABC Transporters
2) Secondary active transport
3) group translocation
```
60
ABC transporters
• primary active transporters use ATP
• ATP binding cassette (ABC) transporters
• observed in bacteria, archaea, and eukaryotes
• consist of:
-2 hydrophobic membrane spanning domains
-2 cytoplasmic associated ATP binding domains
-substrate binding domains
• change shape
61
Secondary active transport
• major facilitator superfamily (MFS)
• use ion gradients to cotransport substances
- protons
- symport - two substances both move in the same direction
- antiport - two substances move in opposite directions
62
Group translocation
* Energy dependent transport that chemically modified molecule as it is brought into cell
* Best known translocation system is phosphoenolpyruvate: sugar phosphotransferase system (PTS)
* prokaryotic cell feature
63
Iron uptake
* Micro organisms require iron
* ferric iron is very insoluble so uptake is difficult
* Micro organisms secrete siderophores to aid in uptake
* siderophores complexes with ferric ion
* complex is then transported into cell
