LECTURE 6 Flashcards
Peptidoglycan
A thin sheet composed of
1) chains of repeating disaccharide unit composed of two monosaccharides
2) small peptides
What are the two monosaccharides that compose the repeating chain of disaccharides in peptidoglycan
1) N-acetylglucosmine (NAG)
2) N-acetylmuramic acid (NAM)
Small peptides that make up peptidoglycan
- attaches to NAM peptides in adjacent chains, cross-linking the chain, making them stronger
Where does the short peptide get added to?
Gets added to the NAM
How do tw peptide side chains attach to each other
Via covalent bonds
Transpeptidation
The cross linking reaction of two peptide chains, this adds strength
Is peptidoglycan a barrier to solutes, why or why not?
No, because the opening are to large.
As. A bacteria grows, peptidoglycan
Is produced more.
Some antibiotics are specific to certain bacteria, what is this based on.
Based on their ability to target prokaryotic-specie structures.
Two common targets for antibiotics are
1) Prokaryotic ribosomes
2) Prokaryotic cell walls
What does it mean for a cell to lyse ?
For it to burst
Lysozyme
An enzyme that catalysts hydrolysis of B 1-4 linkages between NAG and NAM
Peptidoglycan falls apart, causing the cell to lyse.
Staphylococcus
Gram positive bacterium
As bacterial cells grow, it synthesizes more
Peptidoglycan
How does penicillin work?
1) transpeptidation is catalyze by a specific enzyme
2) penicillin inhibits this enzyme
3) peptidoglycan weakens
4) eventually the cells bursts (lysis)
What does penicillin work best on ?
Gram positive cells
Many bacteria besides having a cell wall also have a
Capsule
What is a capsule made of
Mostly polysaccharides
Capsules functions
1) protects from environment
2) stick bacteria to surface
What i sa capsule rare is
Archaea
Two types of pili
1) Fimbriae
2) sex pilus
Fibriae
Attaches to surface of host cells
Gonorrhoea uses fumbriae to attached itself to mucus membranes
Sex pilus
Transfers DNA or plasmid between bacteria cells
Bacterial conjugation
DNA is transfers to another bacteria
Plasmid
A small circular DNA distinct form the chromosome
In a heterogenous environment, many bacteria exhibit
Taxis
Taxis
The ability to move towards or away from a stimulus
Chemotaxis
Movement towards or away from a chemical stimulus
How do motile bacteria move
In a series of runs and tumbles
What happenes if the concentration of the attractant increases during the run
The duration of the run is longer.
Who has flagella
Bacteria, archaea, and eukaryotes
What is the flagella composed of ?
Different proteins that evolved independently
What is the flagella used for ?
Movement.
CCW = run CW = tumble
What does E.coli use to power its motor
A proton-based (H+) electrochemical gradient
Archaea cell walls
- no outer membrane
- coverings surrounding plasma membrane, produces a stronger membrane
- no peptidoglycan
What are some archaea covered in ?
Archaea specific lipopolysacchrides
Eukaryotic cell walls
- provides shape and protection
- cellulose chains embedded in a matrix of other polysaccharides and proteins
Do animal cells have cell walls
NO
Ho has cells walls
Plants and fungi
Plant cell walls
- young plant cells secrete a thin cell wall outside the plasma membrane
- primary cell wall
- secondary cell wall
Primary cell wall
- able to expand as the cell grows
- older the cell, stronger the membrane
- secrete hardening substances into primary
Secondary cells wall
- may have many layers
- made of matrix of strong materials
Cells in wood have many layers of
Cellulose, lignin, proteins
Between primary cell walls of adjacent plant cells is the
Middle lamella
The middle lamella is composed of
Sticky polysaccharides called pectins
Pectin
Glues the adjacent cells together
How are pectin and amylopectin different
Pectin is referring to a mixture of polysaccharides, more complex structure.
Ripening first gets soft in part due to the real down of
Pectin
Because of the thick cell wall and middle lamella, plant cells are
Isolated form each other
What enables plant cells to communicate with the thick cell wall and middle lamella ?
Plasmodesmata
Plasmodesmata
Pores that allows H2O and small solutes to pass.
The pores of plasmodesmata can open and close depending on
environmental conditions or age of plant
What is the order or membranes in a plant cell from outermost to inner most
Plasma membrane
Secondary cell wall
Primary cell wall
Middle lamella
Animal cella
- no cell wall, but secrete proteins and polysaccharides = extra cellular matrix (ECM)
How do cells attach to the ECM
Using additional specialized proteins
What are the specialized protein see to attach to ECM?
Fibronectin
Fibronectin
Interacts with Collagen, binds to a specific class of integral protein called integrins
ECM consists of mostly
Glycoproteins and protein fibres (collagen)
Collagen is
Embedded in network of glycoproteins called proteoglycans.
Proteoglycan complex:
A) types of molecules
B) what is molecule made of?
A) proteoglycan molecules
B) carbohydrates and core protein
