Bio 17-20

The first cells were prokaryotes

(single-celled organisms that lack a nucleus)

lytic cycle

1- Attachment, the capsid combines with a receptor in the bacterial cell wall.2- Penetration, a viral enzyme digests away part of the cell wall, and viral DNA is injected into the bacterial cell.3- Biosynthesis, The machinery of the host cell carries out viral DNA replication and production of multiple copies of the capsid protein subunits.4- Maturation, viral DNA and capsids assemble to produce several hundred viral particles. Lysozyme, an enzyme coded for by a viral gene, disrupts the cell wall. 5- and Release, of phage particles occurs. The bacterial cell dies as a result.

Contrast a viroid with a virus.

A viroid is composed of naked RNA, not covered by a capsid. A virus has an inner core of DNA or RNA and a capsid composed of protein subunits.

Capsid

A virus is made up of a DNA or RNA genome inside a protein shell

What kind of protozoan moves using pseudopods?

Amoeba

What two domains of life contain prokaryotic organisms?

Ans. Bacteria and Archaea

Explain why a virus is host-specific—that is, will infect only a certain type of cell.

Ans. In order to enter a cell, a virus must have a specific capsid protein that binds to a specific receptor protein on the cell's surface.

Describe the process of viral reproduction.

Ans. In the lytic cycle, a virus enters a host cell and replicates, producing many copies of itself. Alternatively, in the lysogenic cycle. the virus, after infecting the cell, may enter a latent stage in which it is dormant but ready to replicate in the future.

Describe the structure of a virus.

Ans. Viruses are composed of an outer capsid of protein subunits and an inner core containing DNA or RNA.

Based on the characteristics shared by all living organisms, should viruses be considered living?

Ans. Viruses are obligate intracellular parasites that can reproduce only inside living cells

Similarities between Archaea and bacteria.

Archaea have generally the same shape, size, and appearance as bacteria. Like bacteria, Archaea multiply by binary fission and move primarily by means of flagella.

The West Africa Ebola OutbreakIn 2013

Ebola Outbreak

Describe the two ways that a virus may infect a cell.

In the lytic cycle, a virus enters a host cell and replicates, producing many copies of itself. Alternatively, in the lysogenic cycle. the virus, after infecting the cell, may enter a latent stage in which it is dormant but ready to replicate in the future.

What is an endospore, and why does it have survival value?

It is a spore formed inside a cell, which can survive harsh treatment such as lack of water and severe. temperatures.

Envelope

Some viruses have external membrane

Identify the three different shapes of bacteria?

Spiral, rod and round

lysogenic cylce

The infected bacterium does not immediately produce phages, but it may do so in the future. In the meantime, the phage is latent, hidden or dormant—not actively reproducing.

How do archaea differ from bacteria?

Unlike bacteria, archaea cell walls do not contain peptidoglycan. Archaea have more complex RNA than Bacteria, similar to Eucarya.

Two compents

an outer capsid made of protein and an inner core of genetic material that is DNA or RNA. The capsid of some viruses is surrounded by a membranous envelope with glycoprotein spikes.

Retroviruses

are viruses that use RNA as their genetic material. A retrovirus contains an enzyme called reverse transcriptase, which carries out transcription of RNA to DNA. The enzyme synthesizes one strand of DNA using the viral RNA as a template, as well as a DNA strand that is complementary to the first one. Using host enzymes, the resulting double-stranded DNA is integrated into the host genome.

Plant viruses are often transferred from plant to plant

by insects and gardening tools.

Which portions of a bacterial cell aid the ability of a bacterium to be resistant to antibiotics?

cell membrane, capsule, ribosomes, and plasmids.

Plant Viruses enter through

damaged tissues

What is an important ecological "job" done by many bacteria that ensures plants have a source of inorganic nutrients?

decomposition

Prions

disease-causing misshapen proteins associated with mad cow disease.

HIV, SARS, Bird flu

emerging viruses

Virus

is an infectious particle that reproduces by "commandeering- take possession or control of" a host cell and using its machinery to make more viruses.

There are two types of prokaryotes

the bacteria and the archaea.

Bacteria

the most diverse and prevalent organisms on Earth.

Viroids

uncovered strands of RNA that infect certain crop plants.

Summarize the three means of introducing variation in bacterial cells.

Conjugation, transformation and transduction.