Exam 1 (The Cell, Endosymbiotic Theory, Prokaryotic Cells)

Spontaneous generation myths

Maggots from meat

Fleas from hair

Flies from fresh and rotting fruit

Mosquitoes from stagnant pond water

Termites are generated

Francesco Redi's experiment

Maggots could only form when flies were allowed to lay eggs in the meat

Maggots were the offspring of flies, not the product of spontaneous generation

John Needham

Briefly boiled broth infused with plant or animal matter. hoping to kill all preexisting microbes, sealed the flasks

Argued that the new microbes must have arisen spontaneously

Results: He likely did not boil the broth enough to kill all preexisting microbes

Lazzaro Spallanzani

Heated but sealed flasks remained clear

Suggested microbes were introduced into these flasks

Results: No microbial growth

Louis Pasteur (disproving spontaneous generation)

Studying microbial fermentation and the causes of wine spoilage, accepted the challenge

Created 'swan-neck' flask (prevents bacteria and particles from entering)

Boiled the solution, left flasks exposed to air

Results: No growth of microorganisms in swan neck flasks, demonstrated that microbes are present in nonliving matter- air, liquids, and solids

Theory of Biogenesis

Rudolf Virchow

Popularized the concept of cel theory using the Latin phrase omnis cellula a cellula (all cells arise from cells)

Germ Theory of Disease

Disease may result from microbial infection

Ignaz Semmelweis

Proposed that physicians were somehow transferring the causative agent to their patients

Importance of handwashing to prevent transfer of disease between patients

Joseph Lister

Began using carbolic acid (phenol) spray disinfectant/antiseptic during surgery

Successful efforts to reduce post surgical infection caused his techniques to become standard medical practice

Robert Koch

Produced a series of postulates based on the idea that the cause of a specific disease could be attributed to a specific microbe

Able to definitively identify the causative pathogens of specific diseases, including anthrax, TB, and chlore

Koch's Postulates

1. Microorganisms are isolated from a diseased or dead animal

2. The microorganisms are grown in pure culture

3. Microorganisms are inoculated into a healthy laboratory animal

4. Disease is reproduced in a laboratory animal

5. The microorganisms are isolated from this animal and grown in pure culture

6. Microorganisms are identified

Vaccination

Coined by Edward Jenner

Observed that milkmaids who developed cowpox, a disease similar to small pox but milder, were immune to the more serious small pox

Pasteur- rabies vaccine

First Antimicrobial drugs

"Magic bullet" or antibiotic that would kill only the microbe, leaving the host unharmed

Paul Ehrlich

Development of antibiotics

Alexander Fleming 1928

Mold contaminant caused a "zone of clearing"

Penicillin- produced by Penicillium chrysogenum

Second half of 20th century- H Florey and E Chain purified penicillin- saved lives of Allied troops

Endosymbiotic Theory

Defined as the theory that mitochondria and chloroplasts arose as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host

Both mitochondria and chloroplasts resemble bacteria in size and shape

Contain circular DNA, typical of prokaryotes

Can reproduce independently of their host cell

Ribosomes resemble those of prokaryotes, and their mechanism of protein synthesis is more similar to that found in bacteria than eukaryotes

Antibiotics that inhibit protein synthesis on ribosomes in bacteria also inhibit protein synthesis on ribosomes in mitochondira and chloroplasts

Prokaryotic cell structure

Envelope (lipopolysaccharide, outer membrane, cell wall, periplasm, inner membrane), Cytoplasm (80% water proteins), Nucleoid (DNA proteins)

Bacterial cell

The cytoplasm of the bacterial cell is a gel-like network of proteins and other macromolecules, contained by cell membrane

Outside the membrane the cell body is enclosed by a cell wall

Gram negative bacteria- have an outer membrane outside the cell wall

Cell membrane, cell wall, and outer membrane (For Gram-negative species)

Chromosome is organized within the cytoplasm as a system of looped coils called the nucleoid

Phospholipids

Core of glycerol

Phosphate, fatty acids

Can be hydrophilic/hydrophobic- attracts cytoplasm

Bilayer

Plasma membrane structure is dynamic

Fluid mosaic model

Cell (plasma) membrane separates the cytoplasm from the outside environment

Phospholipid bilayer with proteins

Bacterial membrane proteins

Peripheral and integral membrane proteins

Support for structure that protrude from the cell (flagella, pili)

Transport of substance in and out cell across the membrane

Signaling and communication (e.g. signal from bacteria - plant - nodules - legumes and nitrogen fixing bacteria)

Passive transport

Moves nutrients with the concentration gradient

Active transport

Moves nutrients against the concentration gradient

Coupled transport

The use of energy from one gradient to drive transport up another gradient (symport and antiport)

Simple diffusion

No energy required, move down concentration gradient

Facilitated diffusion

No energy required

Transporter (channel)- move molecules (high to low)

Four types of active transport

Symport

Antiport

Group translocation

ABC transporters

Symport

1. Energy is released as one substrate moves down concentration gradient

2. This energy moves a second substrate against its gradient and into the cell

Antiport

1. Antiporter binds substrate A on the cytoplasmic side of the membrane

2. Antiporter opens to the outside of the cell, where the concentration of A is lower

3. Substrate A leaves it binding site, and substrate B then binds to its site

4. Antiporter opens to the inside of the cell. Substrate B is released in exchange for substrate A

Group translocation

A biological process where a molecule crossing the cell membrane not only gets transported but also gets transformed in itself

Unique to prokaryotes

High energy organic compounds- goes through phosphorylation cascade- giving energy for transport of sugars

ABC systems

The periplasm binding protein has high affinity for substrate, the membrane-spanning proteins form the transport channel, and the cytoplasmic ATP-hydrolyzing proteins supply the energy for the transport event

1. Solute binds to the substrate-binding protein, and the complex then binds to the membrane transporter

2. The ATPase activity of one component powers the opening of the channel and movement of the solute into the cell

Ion transport by siderophore and an ABS transport complex

1. Bacterium secretes siderophore that binds Fe2+

2. ABC transporter brings Fe3+ across the membrane

3. Inside the cell, the iron is released