MCAT BIOLOGY: Microbiology Ch 5 Flashcards
Third phase of mitosis. During this phase, replicated chromosomes are split apart at their centromers (sister chromatids are separated) and moved to the opposite side of the cells
Anaphase
The first step in viral infection. It is at this point that a virus attaches to its host and it is very specific, also known as adsorption
Attachment
A bacterium that cannot survive on minimal medium (glucose alone) because it lacks the ability to synthesize a molecule it needs to live (typically an amino acid). This bacterium must have the needed substance added to their medium in order to survive typically called the auxiliary trophic substance
Auxotroph
A bacterium having a rod-like shape
Bacillus
Bacterium grows in size until it has doubled its cellular components then it replicates it genomes and splits in two
Binary fission
A sensory receptor that responds to specific chemicals. Some exaples are:
gustatory (Taste) receptors
Olfactory (Smell) receptors
Central chemoreceptors (respod to pH changes in the cerebrospinal fluid
Chemoreceptors
A bacterium having a round shape
Coccus
A form of genetic recombination in bacteria in which plasmid and/or genomic DNA is transferred from one bacterium to the other through a conjugation bridge
Conjugation
A bacterial structure formed in unfavorable growth conditions. These have very tough outer shells made of peptidoglycan and can survive harsh conditions. The bacterium inside these structures is essentially dormant and can become active (called germination) when conditions again become favorable
Endospore
A normal component of the outer membrane of Gram-negative bacteria. These produce extreme immune reactions (septic shock), particularly when many of them enter the circulation at once.
Endotoxin
A lipid bilayer that surrounds the capsid of an animal virus, The __is acquired as the virus buds out through the plasma membrane of its host cell. Not all animal viruses possess this
Envelope
The removal (and usually the activation) of a viral genome from its host’s genome.
Excision
A toxin secreted by a bacterium into its surrounding medium that help the bacterium compete with other species. Some of these toxins cause serious diseases in hjumans (botulism, tetanus, diphtheria, toxic shock syndrome)
Exotoxin
A bacterial plasmid that allows the bacterium to initiate conjugation. Bacteria that possess this are known as F+ “males”
F (fertility factor)
Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma membrane. They stain PINK in gram stain.
Gram negative bacteria
Bacteria that have a thick peptidoglycan cell wall, and no outer membrane. They stain very darkly (purple) in Gram stain
Gram-positive bacteria
High frequency of recombination bacterium. An F+ bacterium that has the fertility facotr integrated into its chromosome. When conjugation takes place, it is able to transfer not only the F factor, but also its genomic DNA
Hfr Bacterium
A dense growth of bacteria that covers the surface of a Petri dish
Lawn
A viral life cycle in which the viral genome is incorporated into the host genome where it can remain dormant for an unspecified period of time. Upon activation, the viral genome is excised from the host genome and typically enters the lytic cycle
Lysogenic cycle
An enzyme that lyses bacteria by creating holes in their cell walls. It is produced in the end stages of the lytic cycle so that new viral particles can escape their host; it is also found in human tears and human saliva
Lysozyme
A viral life cycle in which the host is turned into a “virus factory” and ultimately lysed to release the new viral particles
Lytic cycle
The second step in viral infection, the injection of the viral genome into the host cell
Penetration
A complex polymer of sugars and amino acids; the substance from which bacterial cell walls are made
Peptidoglycan
The space between the inner and outer cell membranes in Gram-negative bacteria. The peptidoglycan cell wall is found in the periplasmic space, and this space sometimes contains enzymes to degrade antibiotics
Periplasmic Space
A long projection on a bacterial surface involved in attachment, e.g. the sex ___ attaches F+ and F- bacteria during cinjugation
Pilus
A clear area in a lawn of bacteria. ____ represent an ara where bacteria are dying and usually caused by lytic viruses
Plaque
Misfolded, self replicating proteins responsible for a class of diseases known as transmissible spongiform encephalopathies that cause degeneration of CNS tissue
Prions
A life cycle of animal viruses in which the mature viral particles bud from the host cell, acquiring an envelope (a coating of lipid bilayer) in the proces
Productive cycle
A virus with an RNA genome that undergoes a lysogenic life cycle in a host with a double-stranded DNA genome. In order to integrate its genome with the host cell genome, the virus must first reverse transcribe its RNA genome to DNA
Retrovirus
An enzyme that polymerizes a strand of DNA by reading an RNA template (an RNA dependent DNA polymerase); this is used by retroviruses in order to integrate their genome with the host cell genome
Reverse transcriptase
A viral enzyme that makes a strand of RNA by reading a strand of RNA. All prokaryotic and eukaryotic RNA polymerase are DNA dependent; they make a strand of RNA by reading a strand of DNA
RNA dependent RNA polymerase
A bacteria having a spiral shape
Spirochete
The transfer by a lysogenic virus of a portion of a host cell genome to a new host
Transduction
Short pieces of a circular single-stranded RNA that do not code for proteins but interfere with normal gene expression. Mostly they cause disease in plants; the only human disease linked to this is Hepatitis D
Viroids
A disease agent that is isolated from a human cannot reproduce on its own in cell-free broth but can reproduce in a culture of human cells. In its pure forme it possesses both RNA and DNA. Is it possible that the disease agent is a virus?
NO, viruses possess only one kind of nucleic acid. Either RNA or DNA this is likely a bacteria
How are viruses classified?
By the shape of their capsid
Helical capsid= rod-shaped
Polyhedral capsi=multiple-sided geometric figures with regular surfaces
How do viruses develop an envelope?
The enveope is made from phospholipids, proteins, and carbohydrates on the host membrane. They get this envelope from budding through the host cell membrane
What is a naked virus? What are examples of naked viruses?
A naked virus is a virus that does not have an envelope. All phages and plant viruses are naked
Why would phages and plant viruses not have enveloped?
Viruses acquire envelopes by budding through host membranes. Phages and plant viruses infect hoss that possess cell walls. There is no membrane through which the remaining viruses must but, they just escape
Why is hydrolase made initially by some bacteriophages in the lytic cycle?
Hydrolase is a hydrolytic enzym that degrades the entire host genome
Why is lysozyme produced at the end of the lytic cycle?
Lysozyme destorys the bacterial cell wall. BEcause of osmotic pressure no longer counteracted by the protection of the cell wall, the host bacterium bursts releasing 100 progeny virus
When a phage incorporates its DNA into the bacterial genome during the lysogenic cycle it is referred to as a __
prophage
Why are prophages in the lysogenic cycle not expressed and progeny not produced?
Dormancy is due to the fact that transcription of phage genes is blocked by phage encoded repressor proteins that bind to specific DNA elements in phage promoters
Many animal viruses enter cells by ___
endocytosis: a process whereby the host cell engulfs the virus and internalizes it
What is the term for animal virus lytic cycle and what is the difference?
Its the same thing! but does not destroy the host cell
Why are the host cells not destroyed by animal viruses after the productive cycle (animal virus lytic cycle)
The enveloped viruses exit the host cell by budding through the host’s cell membrane, not lysing it with lysozyme enzymes
The term for the dormant animal virus in the lysogenic cycle is ___
provirus
a +RNA virus must encode ___ but does not have to carry it
RNA-dependent RNA polymerase
If a viral genome is (+) strand RNA because it is a (+)RNA virus, what is used as a template by the RNA-dependent RNA polymerase?
To make the (+) strand copies of the genome the virus needs complementary strands as a template: the (-) strand RNA, thus RNA-dependent RNA polymerase produces a (-) strand intermediate before generating new (+) strand.
Why do (+) RNA viruses have to ENCODE RNA-dependent RNA polymerase but not carry it?
They need RNA-dependent RNA polymerase to make the complementary strand as a template before generating the (+) strand
What is the genome of a (-) RNA virus?
The genome is complementary to the piece of RNA that encodes viral proteins. IT is the template for viral mRNA production
Why does the (-) RNA virus have to carry RNA-dependent RNA polymerase and encode for it?
If the host ribosomes translated (-) RNA they would make useless proteins. The enzyme will create a (+) strand from the (-) genome and then use the (+) strand as a template to replicate new (-) strand genomes
What must a retrovirus encode for ?
Reverse transcriptase an RNA-dependent DNA polymerase
What is a retrovirus?
A retrovirus is a (+) RNA virus that undergoes lysogeny to integrate into the host genome as a provirus. It has to first become ds-DNA thats why it needs reverse transcriptase
What are the three main retroviral genes?
gag: codes for viral capsid proteins
pol: polymerase codes for reverse transcriptase
env: envelope codes for viral envelope proteins
How does a prion infect a normal version of the protein in the host cell?
When the normally folded protein (PrPc) comes into contact with prion (PrPSc) the prion acts as a template and the shape of the normal protein is altered to become infectious
How do prions affect host nervous tissue?
The misfolded proteins cause the destruction of neurons particularly in the CNS which leads to loss of coordination, dementia, and death
Describe the genome of prokaryotes
- Single double-dstranded circular DNA chromosome
- not in a nucleus (no nucleus in prokaryotes)
- not associated with histone proteins
- transcription and translation occur in the same place and at same time
____are circular pieces of double stranded DNA found in prokaryotes that often often carry antibiotic resistance genes
Plasmid
What two things make plasmids important?
- encode advantageous gene products
- orchestrate bacterial exchange of genetic information (conjugation)
___are normal components of the outer membrane of Gram-negative bacteria that aren’t inherently poisonous but cause an immune reaction.
-these can cause septic shock when many bacteria die and disintegrated outer membrane parts are released into circulation
Endotoxins
___Are a very toxic substance secreted by both gram-negative and gram-positive bacteria into the surrounding medium. They help bacterium compete with other bacterial species such as in the mammalian gut
Exotoxins
___is a sticky layer of polysaccharide “goo” surroudning the bacterial cell.
Capsule or glycocalyx
___makes bacteria more difficult for immune system cells to eradicate and enables bacteria to adhere to smooth surfaces such as rocks, streams, or lining of human respiratory tract
Glycocalyx or capsule
___means bacteria have flagellum located only at one end
Monotrichous
___means bacteria have flagella at both ends
Amphitrichous
___means bacteria has multiple flagella
Peritrichous
What is the difference between the eukaryotic and prokaryotic flagellum?
The eukaryotic flagella contains 9+2 arrangement of microtubules
What powers the rotation of the rod in a bacterial flagellum?
Powered by the diffusion of H+ down the proton graident generated across the inner membrane by electron transport
___bind attractants or repellents and transmit a signal that influences the direction of flagellar rotation
Chemoreceptors
___are long projections on the bacterial surface involved in attaching to different surfaces.
Pili
____are smaller than pili and involved in adhering to surfaces
Fimbriae
___is glucose catabolism with use of an inorganic electron acceptor such as oxygen
Respiration
___is glucose catabolism which does not use an electron acceptor such as O2 instead gives off by-product of glucose catabolism such as lactate or ethanol
Fermentation
How much ATP does aerobic respiration produce per glucose molecule in Prokaryotes?
32 ATP
How much ATP is produced through glucose fermentation by prokaryotes?
2 ATP
___are found in some gram-positive bacteria and have a tough, thick external shell comprised of peptidoyglycan able to survive high temperatures
Endospores
What are found within a bacterial endospore?
- genome
- ribosome
- RNA
- **A single bacterium is able to from only one spore per cell, bacteria cannot increase their population through spore formation
Bacteria have 3 mechaniss of acquiring new genetic material
Transduction
Conjugation
Transformation
___is the transfer of genomic DNA from one bacterium to another by a lysogenic phage
Transduction
If pure DNA is added to a bacterial culture, the bacteria internalize the DNA in certain conditions and gain any genetic information from DNA this is known as__
Transformation
___bacteria make physical contact and form a bridge between cells. One cell copies DNA and this copy is transferred through the bridge to the other cell
Conjugation
Identify foreign pathogens, antigen presenting and produce antibodies
B cells
Mediating a number of immune responses, including those agaisnt viruses, bacteria, and parasites
T cells
Identify foreign pathogens, antigen preseting, and activating other immune cells
Dendritic cells
Degrading pathogens and dead body cells via phagocytosis
Macrophages
Release chemical mediators, such as histamine, that enhance an immune response
Basophils
Releasing chemical mediators such as histamines that modulate an allergic reaction
Mast cells
Killing and phagocytizing bacteria cells
Neutrophils
Defending against parasitic infections and modulating immune responses during allergic reaction
Eosinophils
Release toxins to destroy virus-infected body cells
NK (natural killer) cells
