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What is the significance of cell size, and why are microbial cells typically small?
- The amount of nutrients you need to fill up the cell
- increases faster than the size of the cell itself so what you have is you reach
- a certain point where the cells can no longer bring in enough material to fill
- up feed the cell. So we know that microbial cells overcome this by staying
- small. So how then do Eukaryotes get much larger? How does a human cell get 50
- times its size? (1) Folds in the plasma membrane increases surface area. (2) Having
- organelles allows you to shuttle nutrients inside of cell with them getting
- used up.
What are some typically seen shapes and organizations amongst microbial cells?
There are 3 most common shapes that we see.
Spherical – Cocci
Rod – Bacillus
Curved - Vibriod.
Various types of organizations
Diplo- 2 Cells stuck together.
Tetra- 4 Cells
Strep- Chain of Cells
Staph- Random Cluster of Cells
Compare and Contrast the Bacterial and Archaeal cell Membrane?
- The building blocks of all biological membranes are called
- PHOSPHOLIDPIDS. It’s a semi permeable membrane and there are 3 parts to a phospholipids
- (1) Phosphate Group (2) Fatty Acids (3) Central Sugar called Glycerol. What’s
- special about the chemistry of this molecule? One side is hydrophobic and one
- side is hydrophilic. Since the phosphate side is negatively charged, it’s
- hydrophilic. The fats are going to be hydrophobic; therefore when you put those
- molecules in water, the hydrophobic tails tuck themselves into a Bi-layer
- structure to protect themselves from water. The Phospholipid Bi-Layer is how we
- make membranes in all biology with one small exception. When is the only time
- an organism doesn’t use a Phospholipid Bi-Layer as its membrane? Archaea under
- extreme conditions like extreme heat don’t use a Phospholipid Bi-Layer. Fats
- under high heat melt away, so in order to stabilize their membranes under high
- temp conditions, what’s the modification in Archaea that they make in order to
- overcome this. They connect their membranes and make a MONOLAYER MEMBRANE as
- opposed to a Bi-Layer membrane. The fatty acids basically connect all the way
- through the membrane.
What is the role of the Proton Motive Force, and How is it Generated and Utilized?
- It’s an electrochemical gradient used for energy. So it’s going
- to be used in the cell but for bacteria it’s used in 2 special ways. It can be
- automatically used as energy, or used to generate energy in the form of ATP. In
- our cells we always store energy in the form of ATP. This ATP gets used to do work,
- but in the case of the PMF. The PMF can be used to do work directly. So that’s
- an important difference between bacteria and eukaryotic cells.
What is a 2 Component System, and how does it work?
- The 2 component system includes a sensor and a response
- regulator. The sensor picks up extra-cellular stimulus and affects the response
- regulator and activates a response in response to the stimuli. How does the
- sensor activate the response regulator? Phosphate Cascade. It signals a phosphate
- to move inside the cell to activate the response regulator
Describe the difference between prokaryotic and eukaryotic ribosomes, and the significance of this difference.
- Ribosomes make proteins. Pros are much smaller in size. Why
- is this important? This makes it a good target for antibiotics. In general if
- you want a good antibiotic. The best way to make an antibiotic is to find
- something that is going to target something that is common to all bacteria but
- that is also not found in human cells. So we need to find something that is
- uncommon in bacteria but at the same time common to bacteria. These are small Ribosomes.
- A cells wall is common to all bacteria. By targeting these things that are
- different you can then affect things that are different. You can target
- bacteria without damaging our own host cells.
Describe the structure and function of the Glycocalyx.
- It is a slimy/gummy coat that surrounds the cell that has
- two major functions. (1) An adhesive protective layer and there are two
- different forms of this coat. (a) Capsule which is the more rigid form and a (b)
- Slime layer which is the more fluid or liquid form. What type of Glycocalyx has
- an effect on human cells. It’s called DEXTRAND and it is found on your teeth
- and when you find Dextrand it can lead to tooth decay.
Describe the make up of Bacterial Flagella
- (1)Hook (2)Filament (3)Basal Body. The Tail is used for
- motility. The hook is used for change in direction. All the control happens in
- the Basal Body. The basal body has 3 important regulatory functions. What were those
- three functions? There’s a Protein called MOT. What does Mot do? Mot Provides
- energy. (1) Mot is the motor that provides energy for movement. BB also is a (2)
- Molecular Switch that switches back and forth between clockwise and
- counterclockwise movement and this molecular switch uses Flee. Last function of
- BB is an (3) Anchor, It attaches flagella to cells. So by using mot and flee
- how does flagella move bacterial cells? Random Walk by alternating through runs
- and tumbles. Runs are movement in a straight line and tumbles are changes in
- direction. How do you change between runs and tumbles? What do you have to do?
- By alternating the direction of the spin in clockwise and counter clockwise
- movement you can alternate between runs and tumbles which allow the bacteria to
- move by random walk.
What is chemotaxis, and how does a peritrichous organism move towards a chmical attractant?
So let’s saythere is a chemical attractant available in your environment. How does that affectrandom walk? It still has to be random. It leans its way to that direction byway of BIASED RANDOM WALK. This is where I’m moving towards the attractant andrun longer if I’m moving away from the attractant I’ll switch to a tumblefaster so that over time I’ll move in the general direction that I’m trying tomove to. Chemo-taxis leads to a biased random walk.
Draw a Typical Bacterial Cell, and include the typical structures you would find inside and out .
What term describes a short chain of cells?
What homologue of tubulin defines the septum during cell division?
Which Extra-cellular portion of a common bacteria leads to tooth decay?
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