Chapter 3: Bacterial Cell Structure I & II, Structures & Energetics Flashcards
What is the purpose of the cytoplasmic membrane?
to separate the cytoplasm from the environment
What type of molecules can travel by diffusion?
non-polar
What kind of molecules have to be transported through channels?
polar
What are hopanoids?
pentracyclic chemicals that stabilize the bacterial membrane
What are the 3 functions of the cytoplasmic membrane?
Permeability barrier
Protein anchor
Energy conservation
Where are lipids in the cytoplasmic membrane?
the phospholipid bilayer
What are the parts of the phospholipid bilayer?
Polar heads (hydrophilic)
Non-polar hydrocarbon tails (hydrophobic)
Saturated vs Unsaturated Fatty acids
Saturated fatty acids DO NOT contain double bonds
Unsaturated fatty acids DO contain double bonds
Cis fatty acid
H bonds are on the same side of the double bond
Trans fatty acid
H bonds are on opposite sides of the double bond
What component of the phospholipid is linked to the phosphate group (head) and the fatty acids (tail)
Glycerol
What is the inner leaflet of a gram negative cell composed of?
phospholipid
What is the outer leaflet of a gram negative cell composed of?
Lipopolysaccharide (LPS)
Interact with a variety of substrates or process large molecules for transport
outer surface proteins
interact with substrates involved in energy-yielding reactions and other important cellular functions
inner surface proteins
firmly embedded in the membrane
integral membrane protein
one portion anchored in the membrane (do not span the membrane)
peripheral membrane protein
What is the purpose of channels and carrier proteins?
movement of solute or something larger across the membrane
Where are channels mostly found?
In the outer membrane of gram-negative bacteria
What kind of transfer do channels facilitate?
passsive transfer
What kind of transfer do carrier proteins facilitate?
active and passive transport
What is the slime layer made of?
glycocalyx
Functions of a receptor protein
bonds extracellularly and conformation change relays information to cell
Uniporters
move molecules in one direction
Symporter
moves more than one molecule in the same direction
Antiporter
moves molecules simultaneously into and out of the cell
functions of capsule and slime layers?
- Assist in attachment to surfaces
- Protect against phagocytosis
- Resist desiccation
What are fimbriae?
Short, helical, filamentous structures
Stick to surfaces or eachother
What are pili?
thin filamentous protein structure
longer than fimbriae
functions of pili
- allow for bacterial attachment to surfaces
- can allow for movement through twitching motility
- help bacteria evade components of the innate immune system
what does the conjugal pilus do?
Exchnage DNA form one bacteria to another
what does the conjugal pilus do?
Exchnage DNA form one bacteria to another
how does pili twitching motility work?
- pili extends
- pilli binds to receptor
- pili retracts, pulling bacteria along
how does pili DNA exchange work?
- Donor binds to recipient through conjugal pilus
- plasmids are sent to recipient on the pilus with conjugative proteins
- DNA is now in the recipient cell
what are flagella
Long protein filaments attached to a complex integral membrane protein
how do flagella move the cell?
proton passage drives clockwise or counterclockwise rotation
monotrichuous
single polar flagellum
amphitricuous
a flagellum at each pole
lophotricuous
multiple flagella localized at cell pole
peritrichous
multiple flagella inserted at many locations in the cell membrane
Which types of flagella move coutnerclockwise?
Peritrichous/Lophotricuous
Which types of flagella move clockwise?
Monotrichuous/Amphitricuous
What is taxis?
directed movement in response to chemical or physical gradients
response to chemicals, the best studied movement system
Chemotaxis
response to light
Phototaxis
response to oxygen
Aerotaxis
response to ionic strength
Osmotaxis
response to water
Hydrotaxis
How is chemotaxis measured?
by adding an attractant or repellant to a microbial space and then measuring movement
What is an endospore?
Dormant, non-reproductive structure that allows bacteria survival in harsh environmental conditions
How do you kill endospores?
autoclaving, they are resistant to most cleaning techniques
Vegetative cell vs Endospore
- vegetative cells are still growing/reproductively active to grow endospores
- endospores are dormant versions of the cell
Structure of the bacterial nucleoid
single molecule of DNA in a closed loop
How is DNA condensed?
supercoiling