BIO QUIZ 2 NOTES Flashcards
Why viruses are not considered part of the 6 kingdom classification
Viruses do not fit in the six-kingdom system because they do not display most of the characteristics of living cells. Viruses can only live as parasites, cannot live independently (occupy a position between nonliving and living)
lytic viral reproduction cycle
- Attachment - phage injects its DNA into bacterial target
- Synthesis - parental phage DNA replicates
- Assembly - 200 daughter phages assemble
- Release - daughter phages lyse (break open) the bacteria and start another cycle
lysogenic viral reproduction
a. Attachment – Phage binds to the bacterial cell surface and injects its DNA.
b. Integration – Phage DNA incorporates into the bacterial chromosome, becoming a prophage.
c. Dormancy – The prophage remains inactive, replicating along with the bacterial DNA as the cell divides.
d. Activation – A trigger (e.g., stress, UV light) causes the prophage to exit the bacterial genome.
e. Lytic Entry – The phage enters the lytic cycle, where new phages are synthesized, assembled, and released by lysing the bacterial cell.Attachment:
Proteins on the surface of
the virus bind to protein
receptors on the surface
of the host cell’s membrane.
Entry:
The virus injects
its genetic material
(RNA or DNA) into
the host cell.
Provirus Formation:
Viral DNA becomes
part of the host
cell’s chromosome.
cell division with the provirus inside host cell, then the provirus leaves the host cell
Replication:
The host cell makes
more viral DNA or
RNA and proteins.
Assembly:
New viral particles
are assembled.
Lysis and Release:
The host cell breaks
open and releases
new viral particles.
Protease
a protein that is essential for assembling the virus during the last step of the infection
Reverse transcriptase
to convert genome from RNA (single) to DNA (double) using this lock that allows HIV to enter the host cell.
CD4 receptors
located on surface of T-helper cells and is the “lock” that allows HIV to enter host cell
RNA polymerase
host enzyme that works as a copy machine to use viral DNA to make thousands of copies of viral RNA
Integrase
enzyme that helps insert viral DNA into the host cells DNA. now the viral DNA can remain a latent state or made into a new viral host
Ribosomes and golgi apparatus
ribosomes assemble the virus. Golgi apparatus makes the cell specific instructions needed to send it away
The impact of Immunization on the incident rate of Measles.
The greater that rate of immunization, the number of measles incidence decreases. This shows that the vaccines are working, suggesting that more people should be vaccinated.
The bacteriophage - its features and how a phage is different from other viruses.
**A bacteriophage **is a type of virus that specifically infects and replicates within bacteria. They are among the most abundant biological entities on Earth and play a crucial role in bacterial population control and genetic exchange.
Key Features of Bacteriophages
Host Specificity – Phages only infect bacteria and archaea, unlike other viruses that target eukaryotic cells.
Structure – They often have a capsid (protein coat) enclosing their genetic material and a tail used for injecting DNA/RNA into the host. The structure can be simple (icosahedral) or complex (e.g., T4 phage).
Genetic Material – Phages can have DNA or RNA genomes, which may be single-stranded or double-stranded.
Replication Cycles – They follow either:
Lytic cycle (virulent phages) – The phage takes over the bacterial machinery, produces new viruses, and bursts the bacterial cell.
Lysogenic cycle (temperate phages) – The phage integrates its genome into the bacterial DNA, remaining dormant until conditions trigger the lytic cycle.
Abundance and Diversity – Found in soil, water, and the human microbiome, phages outnumber bacteria by a large margin.
How Bacteriophages Differ from Other Viruses
Infect only bacteria, whereas other viruses infect plants, animals, or humans.
Inject their DNA/RNA into the host using a tail, while other viruses enter via endocytosis or membrane fusion.
Replicate in the bacterial cytoplasm, whereas many viruses replicate in the nucleus or cytoplasm of eukaryotic cells.
Typically cause bacterial lysis (bursting), while other viruses may exit via lysis, budding, or exocytosis.
Play a role in bacterial population control and gene transfer, whereas other viruses often cause diseases or have therapeutic uses.
common shapes of bacteria
They have three main shapes:
Cocci (round)
Bacilli (rod-shaped)
Spirilla (spiral)
what type of cell is bacteria
Bacteria are single-celled microorganisms classified as prokaryote
common features of bacteria
-Cell wall
-Can reproduce quickly through binary fission.
-Some can form spores to survive harsh conditions.
bacterial reproduction
Bacteria reproduce through two main types of processes: asexual reproduction (e.g., binary fission) and sexual reproduction (e.g., conjugation).
binary fission and its steps
Binary Fission: the asexual form of reproduction used by most prokaryotes (and some eukaryotic organelles), in which a cell divides into two genetically identical cells (or organelles)
steps:
1. The bacterial cell elongates and its DNA is copied.
2. The DNA moves to opposite ends of the cell and septum begins to form.
3. The cell membrane pinches inward, and a new cell wall forms.
4. The cell splits into two identical daughter cells.
what is conjugation and its steps
Conjugation: In less favourable conditions, some bacteria and archaea are able to exchange DNA by conjugation. This process produces cells with new genetic combinations, and thereby provides a chance that some may be better adapted to changing conditions. During conjugation, one cell links to another cell through a bridging structure and transfers all or part of its chromosomes to the other cell. Unlike asexual reproduction, conjugation results in cells with new genetic content. This increases diversity.
Steps:
1. Conjugation tube forms between a donor and recipient. 2. An enzyme nicks the plasmid.
Plasmid DNA replication starts by moving through the tube.
3. In the recipient cell, replication starts on transferred DNA.
4. The cells move apart and the plasmid in each form a circle
Contrast and compare obligate aerobes, obligate anaerobes and facultative anaerobes
- Obligate Aerobes – bacteria that require oxygen for respiration (like all other plants and animals)
- Obligate Anaerobes – Cannot survive in oxygen (e.g., Clostridium botulinum).
- Facultative Anaerobes – bacteria that prefer environments with oxygen, but can live without oxygen (e.g., E. coli). In absence of oxygen, energy is obtained through fermentation.
Antibiotic Resistance - how it occurs and why it occurs.
How It Occurs:
Bacteria can develop resistance through mutations or by acquiring resistance genes from other bacteria (conjugation).
Overuse or misuse of antibiotics speeds up resistance development.
Why It Occurs:
Natural selection: Resistant bacteria survive and multiply when antibiotics kill non-resistant bacteria.
Horizontal gene transfer: Bacteria share resistance genes through plasmids.
Difference between a Vaccine and an Antibiotic. How does each fight off infection?
Vaccine:
Prevents infections before they happen.
Introduces a weakened or inactive pathogen to stimulate the immune system.
Helps the body develop immunity to specific bacteria or viruses.
Example: Polio vaccine, flu vaccine.
Antibiotic:
Treats bacterial infections after they occur.
Kills bacteria or stops their growth.
Ineffective against viruses.
Example: Penicillin, tetracycline.
4 ways viruses can differ
-Envelope
-Host(s)
-Genome Type
-Transmission
