Retrovirus reverse transcripiton infecting a host cell

Retrovirus replication cycle; how it infect it host cell and assemblying more of it kinds

1.    Retroviruses are enveloped viruses. The virion carries two copies of single-stranded RNA plus enzyme, reverse transcriptase.

2.    When the viruses enter the cell, the single stranded RNA and reverse transcriptase are released inside the cell.

3.    The single-stranded RNA (function: viral information) is converted to double stranded DNA by the enzyme reverse transcriptase (function: transcribe ssRNA to cDNA)

4.    The double stranded DNA is integrated into the host cell’s chromosomes as a provirus

5.    Some cells carry provirus in the latent state and no virions are produced whereas other infected cells continuously synthesize new virions. The viral DNA is transcribed to produce one long polygenic messenger RNA.

6.    The messenger RNA is translated onto a long polyprotein, which is then cleaved by a viral-encoded protease to yield the individual proteins that make up the virons.

(McGraw-Hill. Replication cycle of a Retrovirus. Available from: http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter18/animation_quiz_3.html)

Basic step in viral replication

Step	Description
Attachment	attachment of the virus particle to the host cell receptor
Penetration	the virus is engulfed and enters host cell
Uncoating	viral genetic material is freed into host cytoplasm
Replication and synthesis	viral genetic material replicated, and viral proteins synthesized
Assembly	viral genetic material is packaged within capsid and proteins are packaged together
Release	virus will be released from the cell

waste minimization strategy - 3Rs

Bacterial Endospores

What is spontaneous generation?

It is a theory that says that living organisms can come from non-living organisms (Abiogenesis). However, this theory has been falsified by Louis Pasteur in 1864. Living organism can only come from living organisms (Biogenesis).

Microbial control Method

Disinfection: The destruction or removal of vegetative pathogens but not bacterial endospores. Usually used only on inanimate object

Sterilization: The complete removal or destruction of viable microorganisms. Usually used only on inanimate object

Antisepsis: Chemicals applied to the body surfaces to destroy or inhabit vegetative pathogens

Chemotherapy: Chemicals used internally to kill or inhabit growth of microorganisms with host tissues.

Function of Prokaryotic Structure

Organelle	Function
Plasma membrane	Selectively permeable barrier, mechanical boundary of cell, nutrients and waster transport, location of many metabolic processes (respiration, photosynthesis), detection of environment cues for chemotaxis
Gas vacuole	Buoyancy for floating in aquatic environment
Ribosome	Protein synthesis
Inclusion bodies	Storage of carbon, phosphates, and other substances
Nucleoid	Location of genetic materials (DNA)
Periplasmic space	Contains hydrolytic enzyme and binding proteins for nutrients processing and uptake
Cell wall	Give prokaryotic shape and protection from osmotic stress
Capsules and slime layers	Resistance to phagocytosis, adherence to surfaces
Fimbriae and Pili	Attachment to surfaces , bacterial mating
Flagella	Movement
Endospore	Survival under harsh environment conditions

*Chemotaxis – Bacterial does not move around aimlessly, but are attracted to nutrient (sugar, amino acid), and repelled by many harmful substance. Environment cues – temperature (thermo taxis), light (photo taxis), oxygen (aero taxis), etc .. Movement toward chemical attraction and away from repellents is known as chemotaxis.

Function of Eukaryotic Structure

Organelle	Function
Plasma membrane	Selectively permeable barrier with transport system, mechanical boundary of cell, mediates cell-cell interactions and adhesion to surfaces, secretion
Cytoplasmic matrix	Environment for other organelles, location of many metabolic processes
Ribosome	Protein synthesis
Endoplasmic Reticulum	Transport of materials, protein and lipid synthesis
Microfilament, intermediate filament, microtubules	Cell structure and movements, formation of cytoskeleton
Golgi apparatus	Packing and secretion of materials for various purpose, lysosomes formation
Cell wall and Pellicle	Strengthen and give shape to cell
Lysosomes	Intracellular digestion
Mitochondria	Energy production through use of the tricarboxylic acid cycle, electron transport chain, oxidative phosphorylation, and other pathways
Flagella and cilia	Cell Movement
Chloroplasts	Photosynthesis – trapping light energy and formation of carbohydrates from CO2 and water
Nucleus	Repository for genetic information, control center for cell
Nucleolus	Ribosomal RNA synthesis, ribosome contrustion
Vacuole	Temporary storage and transport, digestion (food vacuole), water balance (contractile vacuole)

Bacterial Endospores

Endospores act as a defense mechanism to help bacteria to survive in harsh environment conditions

Endospores are metabolically inactive, like a seed that is able to wait for the environment to again become favourable. Once environmental conditions improve, the endospore then germinates back into a living, vegetative cell that can grow and thrive.

Vegetative bacteria are those bacteria or microorganisms that can grow and reproduce in place where many nutrients are available. The actively growing bacteria in these conditions are referred to as "vegetative cells".

Some bacterial survive adverse environment conditions by forming endospores, dormant structure resistant to heat, desiccation, and many chemicals.

**The spores are surrounded by a thin, delicate covering called exosporium. A spore coat lies beneath the exosporium, is composed of several protein layers, and may be fairly thick. It is impermeable to many toxic molecules and is responsible for the spore resistance to chemicals. The coat also is thought to contain enzyme that are involved in germination.