Bacteria and Viruses

(4A) Compare & contrast prokaryotic and eukaryotic cells.

SIMILARITIES:1. They both have DNA as their genetic material.

2. They are both membrane bound.

3. They both have ribosomes .

4. They have similar basic metabolism .

5. They are both amazingly diverse in forms.


1. eukaryotes have a nucleus, while prokaryotes do not

2. eukaryotes have membrane-bound organelles, while prokaryotes do not. The organelles of eukaryotes allow them to exhibit much higher levels of intracellular division of labor than is possible in prokaryotic cells.

3. Eukaryotic cells are, on average, ten times the size of prokaryotic cells.

4. The DNA of eukaryotes is much more complex and therefore much more extnsive than the DNA of prokaryotes.

5. Prokaryotes have a cell wall composed of peptidoglycan, a single large polymer of amino acids and sugar . Many types of eukaryotic cells also have cell walls, but none made of peptidoglycan.

6. The DNA of prokaryotes floats freely around the cell; the DNA of eukaryotes is held within its nucleus and associated with histones (proteins)

7. Eukaryotes undergo mitosis; prokaryotes divide by binary fission (simple cell division)

(4A) What are the basic structures of bacteria?


Bacteria in human intestines aid in the digestion of certain foods; Production of cheese, yogurt, and other foods Decomposition and recycling of dead organisms Fixation of nitrogen from the atmosphere into useable nitrogen in soils Production of antibiotics Photosynthetic bacteria produce oxygen

(4C) What is the lytic cycle?

In the viral life cycle there are two different forms of reproduction. One of them is rapid and results in the death of the infected (host) cell. This is the lytic cycle and it generates thousands to millions of copies of new virus in a few hours.

(4C) What is the difference between the structure of bacteria and viruses?

   Viruses :

-Lack cellular machinery.

-Requires a host cell to replicate. Can't replicate on its own.

-Are mostly pathogenic. Cause several diseases in both plants & animals.

-There is a protein-coat surrounding its genetic material, konwn as 'capsid'.

-Genetic material is either DNA or RNA.

-Size is around 200-400nm.

-Visible only under Electron Microscope.

Bacteria :-

-Possesses a cellular machinery.

-Can replicate on its own.

-There is a cell

-wall surrounding the cell, made up of nitrogenous compounds.

-Genetic material is circular DNA.

-Size is not greater than 0.01mm.

-Visible under Light Microscope.


The immune system is the body's defense against  a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. The cells involved are white blood cells, or leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.Leukocytes are produced or stored in many locations in the body, including the thymus, spleen, and bone marrow. For this reason, they're called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily as lymph nodes, that house the leukocytes.The leukocytes circulate through the body between the organs and nodes via lymphatic vessels and blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for germs or substances that mi

(4b) What is N2 fixation, and what causes it?

Nitrogen-fixing bacteria and algae use nitrogen gas to make ammonium compounds. These compounds are absorbed by plants.

(4b) What is binary fission and conjugation?

Similarities: they are both a simple form of reproduction. They both involve multiplying by cytoplasmic and nuclear division.

Binary fission: Asexual. One organism divides into two approx. equal organisms.

Conjugation: Sexual reproduction. Two organisms pair up, exchange nuclear material (micronuclei in the Paramecium) and then split twice by binary fission. Conjugation seems to give the new organisms "rejuvenation", that is ,the ability to withstand harsher environmental conditions, as opposed to binary fission alone.


An endospore is a dormant, tough, non-reproductive structure produced by a small number of bacteria from the Firmicute family.The primary function of most endospores is to ensure the survival of a bacterium through periods of environmental stress.They are therefore resistant to ultraviolet and gamma radiation, desiccation, lysozyme, temperature, starvation, and chemical disinfectants.Endospores are commonly found in soil and water, where they may survive for long periods of time.

(11B) What is the basic structure of an endospore?