Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

- They have less rRNA and proteins. a. Why is this difference important? Selective toxicity. We can target their ribosomes without targeting ours.

- 2 roles of the lysosome are: 1. digest items brought into the cell. 2. recycle old/damaged organelles.

The Glycocalyx

- 2 types are capsules and slime layer. - 2 roles are attachment and protection.

Prokaryotic Cells

- Bacillus: Rod shape. - Coccus: Sphere shape. - Spirillum: Spiral shape. - A basic description of a prokaryotic cell: It is an unorganized sac of life.

a. If flagella are all around the cell that arrangement is peritrichous. b. If flagella are absent that is called atrichous.

- Cell movement is called taxis, and it is a biased walk towards or away from something. There are several types of taxis:

Inside the Cell

- Cytosol: The liquid component of the cytoplasm - Ribosomes: Responsible for synthesizing proteins

Escherichia coli uses fimbriae to attach to your urinary tract when it causes a UTI. Drinking cranberry juice is helpful because cranberry juice prevents fimbriae formation. Both structures are composed of a protein called pilin.

- Endospores are survival structures. That is why they are resistant to dessication, heat, chemicals, and disinfectants.

Active Transport

- Energy is required for active transport. Most of the time (but not always) this energy comes from that universal energy currency molecule called ATP. This process requires energy because it is moving molecules against their concentration gradient.

The Eukaryotes

- Eukaryotic cells are about 10 to 100x bigger than prokaryotic cells. - they have internal rooms called organelles, where special processes occur.

Types of Cells

- Gram positive (+) cells have a thick cell wall. They also contain teichoic acids that are important for extra strength and cation movement (we think).

Flagella

- How are eukaryotic flagella different from prokaryotic? 1. protein= flagellin(pro) and tubulin (Eu). 2. structurally very different. 3. EU= internal structure. PRO= external structure. - The glycocalyx of a eukaryotic cell is involved in cell to cell adhesion or cell identity.

- Isotonic: the situation where the concentration inside and outside the cell is equal. a. Which way will water flow? ~ There is NO net flow or movement.

- If the bacterial cell is hypotonic to the environment, the water will flow into the cell. a. This is the normal situation, and is the reason why the bacteria have a cell wall. The cell wall prevents osmotic lysis.

- Escherichia coli O157:H7 is the culprit behind a lot of food poisonings. The O157 is a type of O antigen. The O antigen is made up a series of sugars that are different for different bacteria. The H antigen is found on the flagella.

- In the Gram negative cell, the space in between the 2 membranes is called the periplasm.

A Defense Weapon that We Have

- Lysozymes is an enzyme found in tears (as well as many other secretions) that attacks the cell wall. This leads to osmotic lysis of the bacterial cell, when conditions are appropriate.

The Barrier

- Most of the plasma membrane is made of phospholipids. These lipids are arranged in a tail to tail orientation. a. Transmembrane proteins span the membrane.

Exceptions

- Mycoplasmas lack a cell wall, so gram staining is not used to identify them. - Their membranes are aided by sterols. - Would penicillin be effective against these? Why or why not? No because they don't have cell walls.

a. Never open a Petri dish that contains a colony that looks like an egg, because a lot of Mycoplasma are pathogenic.

- Organisms in the genus Mycobacterium cannot be Gram stained because of their very effective barriers. The Gram stains cannot penetrate these cells.

Getting Across

- Passive transport sends molecules down their concentration gradient (from an area of high concentration to an area of low concentration).

Other Special Structures

- Pili are used for conjugation, while fimbriae are only for attachment. An essential step in the production of disease is attachment of the pathogen to the appropriate area of the body. Fimbriae are just one example of a structure that can allow a pathogen to attach.

- Gram negative (-) cells have a thin cell wall. They also have an outer membrane that is different from the plasma membrane lipopolysaccharide (LPS) is found in this outer membrane.

- The 2 main components of the LPS are lipid A, an endotoxin, and the O polysaccharide. - Lipid A intoxication can induce fever and shock to infected individuals.

The Cell Wall

- The bacterial cell wall is composed of peptinoglycan. - The 2 purposes of the cell wall: a. Provide cell shape (minor role). b. Prevent osmotic lysis (major role)

Movement

- The flagellum is a whip-like structure made of flagellin. It is used for movement. There are several arrangements of flagella.

Osmosis

- The flow of water across a semi permeable membrane is called osmosis. a. In this case, water is flowing down its concentration gradient. 1. Hypo: under or below 2. Hyper: above or more

The Genome

- The genome of a prokaryotic cell is composed of a single circular (shape) piece of DNA(chromosome) that is found in the nucleoid region. DNA is information.

4. Safranin is a secondary stain. a. Gram + cells will appear purple. b. Gram - cells will be pink.

- The importance of Gram staining: a. Remember that some antibiotics only work on certain cell types.

The Ribosome

- The ribosome is composed of rRNA and proteins. - What is the ribosome's job? Protein Synthesis

- There is an internal network of structures called the cytoskeleton. a. Microfilaments: Used to transport items within the cell. b. Microtubules: Transport items within the cell. c. Intermediate Filaments: Stable structures that hold everything in place.

- What is the difference between prokaryotic and eukaryotic ribosomes? Prokaryotic ribosomes are smaller.

This process has lead to the rapid spreading of antibiotic resistance. Mating factors are genes that allow microbes to share plasmids with one another through conjugation.

- What is the simple process by which bacteria divide? Binary Fission

General Questions

- Which cells are larger: Eukaryotes. - Which are more complex?: Eukaryotes.

2. Facilitative Diffusion uses a carrier to get molecules across the membrane. - integral proteins attach and transport the molecules across the membrane.

- the molecules that are being transported across the membrane go down their concentration gradient.

Types of Passive Transport

1. Simple Diffusion uses a channel to get atoms or molecules across the membrane. -The molecules that are being transported across the membrane go down their concentration gradient.

Gram Staining

1. The primary stain is crystal violet. it gets into both cell types (both types turn purple).

2. Iodine is a mordant that reacts with the crystal violet and forms huge crystals. a. Gram positive cells have a thick cell wall. b. Gram negative cells have a thin cell wall. c. Hint: to remember this, draw out the symbols + and -. Thicker symbol has thick cell wall.

3. Alcohol is the decolorizer. It causes different things to happen in the different cell types.

The force behind this type of transport is diffusion, and it is due to the movement of water molecules.

Solute motion, due to the constant bombardment by water molecules, is called Brownian motion.

b. Peripheral proteins stay on one side. - What is selective permeability? Water. - ATP production at the membrane is essential because ATP = the universal energy currency of the cell.

Some microbes can also carry out photosynthesis, which captures energy from the sun.

Penicillin is one of those antibiotics that works well on gram + cells, but not so well on gram - cells.

The dosage must be increased for penicillin to effectively treat a Gram negative infection or a different antibiotic should be chosen.

- Treponema pallidum causes the sexually transmitted infection (STI) sexually transmitted disease (STD). Its special form of locomotion allows it to spin its way through thick secretions, like those that are found in the vaginal regions.

The infectious dose is estimated to =1 organism.

The cell does not have to make use of all of the information in its genome. Segments of the information (genes) can either be used or unused at any given point in time, depending upon the cell's needs.

When the cell makes use of the information that is found within the genome, the cell gains characteristics. When the cell doesn't use of the information that is found within the genome, the cell lacks those characteristics.

- Examples of how the glycocalyx helps pathogens cause disease: a. Streptococcus mutans inhabits your mouth. It attaches to your teeth because it has a sticky glycocalyx. It sits there metabolizing and producing acids that cause dental caries.

b. Bacillus anthracis causes death. It has a capsule that helps it evade the immune system by preventing destruction.

- When in the old west, people used to salt their meat to prevent spoilage. Cells that land on salted meat will find themselves hypertonic compared to the environment.

a. Which way will water flow? - Outside the cell b. What will happen to the cell? - Plasmolysis

a. In Gram positive (+) cells, it dehydrates the cells making it harder for the crystals to leave. The thick cell wall is slightly damaged but remains intact. The crystals cannot leave the cell (cells stay purple).

b. In Gram negative (-) cells, the alcohol punctures the cell membrane, punctures the thin cell wall and destroys the outer membrane. This makes it easier for the crystals to leave (clear cells).

a. Chemotaxis = movement towards or away from chemicals. 1. A microbe may want to move towards sugar and away from disinfectants.

b. Phototaxis = movement towards or away from light.

If the cell gains DNA, since DNA is information, then the cell may have extra characteristics. - Example of extra characteristics: a. Antibiotic resistance genes are often found on plasmids.

b. Plasmids are extra pieces of circular DNA that can easily be transferred from one cell to another through the process called conjugation. Plasmids can even be transferred between different species.

- Unlike most prokaryotes, Eukaryotes can engulf large amounts of materials at once. a. Cell drinking is called pinocytosis, while cell eating is called phagocytosis.

b.Which process is important for cells if the immune system? Cells of the immune system use phagocytosis to eliminate invaders.