WK1: Unicellular structure and function Flashcards
Why does the permeable barrier of the cytoplasmic membrane exclude large and charged molecules?
To prevent leakage of solutes from the cells
What are the 2 transports for large and charged molecules across the membrane?
Passive; diffusion of molecules across the phospholipid bilayer
Active; recognise specific solutes that can be transported into their cell along their chemical gradient
What is the cell wall made up of? and what does it provide?
The cell wall provides rigidity to the cell as cytoplasmic membrane is easily ruptured. It is made up of peptidoglycan to resist osmotic pressure.
What is peptidogylcan?
It’s made up of strings of alternating sugars (N-acetylglucosamine and N-acetylmuramic acid) which are crosslinked by short peptides to form a lattice-like structure providing protection
What is the difference between gram positive and gram negative cell walls?
Gram positive; thick peptidoglycan cell wall anchored to CM.
Gram negative; thin peptidoglycan with a second phospholipid bilayer.
- The out later contains chains of lipopolysaccharide
What does lipopolysaccharide consist of? and what is its function?
O-specific polysaccaride, a core polysaccaride and lipid. It’s function is strengthen the outer membrane and protect the bacteria from harmful substances in the environment.
How are gram negative and gram positive bacteria differentiated?
Differentiated with gam staning.
- Thick layer of gram positive bacteria means they will retain the most crystal violet and will show purple
Gram negative; don’t retain the crystal violet but will pick up the pink colour during counterstain
What is the function of a cell’s capsule?
Protect the cell from dessication, host immune responses and facilitate interactions with solid surfaces
What is the role of fimbria and pili?
- Allows a bacterial cell to adhere to surfaces (used for attachment and helping the microbes colonize). It can bind to specific receptors on human cells allowing the bacteria to attach
How does the flagella allow bacteria to swim?
It creates a propellor motion. The flagellar filament is rotated by a motor apparatus in the plasma membrane. (powered by a proton motive force)
How does the flagella allow directional swimming?
By switching the direction of the flagella’s rotation - it can tumble (randomly change direction) and run (move in one direction)
What is chemotaxis?
- Directed motion of an organism towards an environmental condition deemed attractive and away from those considered as repellants
How are plasmids (containing DNA) transferred?
Through bacterial conjugation - one bacteria transfering plasmids to another bacterial cell via a sex pilus.
What are the 2 subunits that make up a mature ribosome?
The small and large subunit
What cell division does bacteria undergo?
Binary fission - forms 2 identical daughter cells
