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MCAT > MCAT BIOLOGY: Microbiology Ch 5 > Flashcards

MCAT BIOLOGY: Microbiology Ch 5 Flashcards

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1
Q

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

A

Anaphase

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2
Q

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

A

Attachment

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3
Q

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

A

Auxotroph

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4
Q

A bacterium having a rod-like shape

A

Bacillus

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5
Q

Bacterium grows in size until it has doubled its cellular components then it replicates it genomes and splits in two

A

Binary fission

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6
Q

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

A

Chemoreceptors

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7
Q

A bacterium having a round shape

A

Coccus

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8
Q

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

A

Conjugation

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9
Q

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

A

Endospore

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10
Q

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.

A

Endotoxin

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11
Q

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

A

Envelope

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12
Q

The removal (and usually the activation) of a viral genome from its host’s genome.

A

Excision

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13
Q

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)

A

Exotoxin

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14
Q

A bacterial plasmid that allows the bacterium to initiate conjugation. Bacteria that possess this are known as F+ “males”

A

F (fertility factor)

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15
Q

Bacteria that have a thin peptidoglycan cell wall covered by an outer plasma membrane. They stain PINK in gram stain.

A

Gram negative bacteria

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16
Q

Bacteria that have a thick peptidoglycan cell wall, and no outer membrane. They stain very darkly (purple) in Gram stain

A

Gram-positive bacteria

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17
Q

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

A

Hfr Bacterium

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18
Q

A dense growth of bacteria that covers the surface of a Petri dish

A

Lawn

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19
Q

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

A

Lysogenic cycle

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20
Q

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

A

Lysozyme

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21
Q

A viral life cycle in which the host is turned into a “virus factory” and ultimately lysed to release the new viral particles

A

Lytic cycle

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22
Q

The second step in viral infection, the injection of the viral genome into the host cell

A

Penetration

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23
Q

A complex polymer of sugars and amino acids; the substance from which bacterial cell walls are made

A

Peptidoglycan

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24
Q

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

A

Periplasmic Space

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25
Q

A long projection on a bacterial surface involved in attachment, e.g. the sex ___ attaches F+ and F- bacteria during cinjugation

A

Pilus

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26
Q

A clear area in a lawn of bacteria. ____ represent an ara where bacteria are dying and usually caused by lytic viruses

A

Plaque

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27
Q

Misfolded, self replicating proteins responsible for a class of diseases known as transmissible spongiform encephalopathies that cause degeneration of CNS tissue

A

Prions

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28
Q

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

A

Productive cycle

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29
Q

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

A

Retrovirus

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30
Q

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

A

Reverse transcriptase

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31
Q

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

A

RNA dependent RNA polymerase

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32
Q

A bacteria having a spiral shape

A

Spirochete

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33
Q

The transfer by a lysogenic virus of a portion of a host cell genome to a new host

A

Transduction

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34
Q

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

A

Viroids

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35
Q

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?

A

NO, viruses possess only one kind of nucleic acid. Either RNA or DNA this is likely a bacteria

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36
Q

How are viruses classified?

A

By the shape of their capsid
Helical capsid= rod-shaped
Polyhedral capsi=multiple-sided geometric figures with regular surfaces

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37
Q

How do viruses develop an envelope?

A

The enveope is made from phospholipids, proteins, and carbohydrates on the host membrane. They get this envelope from budding through the host cell membrane

38
Q

What is a naked virus? What are examples of naked viruses?

A

A naked virus is a virus that does not have an envelope. All phages and plant viruses are naked

39
Q

Why would phages and plant viruses not have enveloped?

A

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

40
Q

Why is hydrolase made initially by some bacteriophages in the lytic cycle?

A

Hydrolase is a hydrolytic enzym that degrades the entire host genome

41
Q

Why is lysozyme produced at the end of the lytic cycle?

A

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

42
Q

When a phage incorporates its DNA into the bacterial genome during the lysogenic cycle it is referred to as a __

A

prophage

43
Q

Why are prophages in the lysogenic cycle not expressed and progeny not produced?

A

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

44
Q

Many animal viruses enter cells by ___

A

endocytosis: a process whereby the host cell engulfs the virus and internalizes it

45
Q

What is the term for animal virus lytic cycle and what is the difference?

A

Its the same thing! but does not destroy the host cell

46
Q

Why are the host cells not destroyed by animal viruses after the productive cycle (animal virus lytic cycle)

A

The enveloped viruses exit the host cell by budding through the host’s cell membrane, not lysing it with lysozyme enzymes

47
Q

The term for the dormant animal virus in the lysogenic cycle is ___

A

provirus

48
Q

a +RNA virus must encode ___ but does not have to carry it

A

RNA-dependent RNA polymerase

49
Q

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?

A

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.

50
Q

Why do (+) RNA viruses have to ENCODE RNA-dependent RNA polymerase but not carry it?

A

They need RNA-dependent RNA polymerase to make the complementary strand as a template before generating the (+) strand

51
Q

What is the genome of a (-) RNA virus?

A

The genome is complementary to the piece of RNA that encodes viral proteins. IT is the template for viral mRNA production

52
Q

Why does the (-) RNA virus have to carry RNA-dependent RNA polymerase and encode for it?

A

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

53
Q

What must a retrovirus encode for ?

A

Reverse transcriptase an RNA-dependent DNA polymerase

54
Q

What is a retrovirus?

A

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

55
Q

What are the three main retroviral genes?

A

gag: codes for viral capsid proteins
pol: polymerase codes for reverse transcriptase
env: envelope codes for viral envelope proteins

56
Q

How does a prion infect a normal version of the protein in the host cell?

A

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

57
Q

How do prions affect host nervous tissue?

A

The misfolded proteins cause the destruction of neurons particularly in the CNS which leads to loss of coordination, dementia, and death

58
Q

Describe the genome of prokaryotes

A
  • 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
59
Q

____are circular pieces of double stranded DNA found in prokaryotes that often often carry antibiotic resistance genes

A

Plasmid

60
Q

What two things make plasmids important?

A
  • encode advantageous gene products

- orchestrate bacterial exchange of genetic information (conjugation)

61
Q

___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

A

Endotoxins

62
Q

___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

A

Exotoxins

63
Q

___is a sticky layer of polysaccharide “goo” surroudning the bacterial cell.

A

Capsule or glycocalyx

64
Q

___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

A

Glycocalyx or capsule

65
Q

___means bacteria have flagellum located only at one end

A

Monotrichous

66
Q

___means bacteria have flagella at both ends

A

Amphitrichous

67
Q

___means bacteria has multiple flagella

A

Peritrichous

68
Q

What is the difference between the eukaryotic and prokaryotic flagellum?

A

The eukaryotic flagella contains 9+2 arrangement of microtubules

69
Q

What powers the rotation of the rod in a bacterial flagellum?

A

Powered by the diffusion of H+ down the proton graident generated across the inner membrane by electron transport

70
Q

___bind attractants or repellents and transmit a signal that influences the direction of flagellar rotation

A

Chemoreceptors

71
Q

___are long projections on the bacterial surface involved in attaching to different surfaces.

A

Pili

72
Q

____are smaller than pili and involved in adhering to surfaces

A

Fimbriae

73
Q

___is glucose catabolism with use of an inorganic electron acceptor such as oxygen

A

Respiration

74
Q

___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

A

Fermentation

75
Q

How much ATP does aerobic respiration produce per glucose molecule in Prokaryotes?

A

32 ATP

76
Q

How much ATP is produced through glucose fermentation by prokaryotes?

A

2 ATP

77
Q

___are found in some gram-positive bacteria and have a tough, thick external shell comprised of peptidoyglycan able to survive high temperatures

A

Endospores

78
Q

What are found within a bacterial endospore?

A
  • genome
  • ribosome
  • RNA
  • **A single bacterium is able to from only one spore per cell, bacteria cannot increase their population through spore formation
79
Q

Bacteria have 3 mechaniss of acquiring new genetic material

A

Transduction
Conjugation
Transformation

80
Q

___is the transfer of genomic DNA from one bacterium to another by a lysogenic phage

A

Transduction

81
Q

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__

A

Transformation

82
Q

___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

A

Conjugation

83
Q

Identify foreign pathogens, antigen presenting and produce antibodies

A

B cells

84
Q

Mediating a number of immune responses, including those agaisnt viruses, bacteria, and parasites

A

T cells

85
Q

Identify foreign pathogens, antigen preseting, and activating other immune cells

A

Dendritic cells

86
Q

Degrading pathogens and dead body cells via phagocytosis

A

Macrophages

87
Q

Release chemical mediators, such as histamine, that enhance an immune response

A

Basophils

88
Q

Releasing chemical mediators such as histamines that modulate an allergic reaction

A

Mast cells

89
Q

Killing and phagocytizing bacteria cells

A

Neutrophils

90
Q

Defending against parasitic infections and modulating immune responses during allergic reaction

A

Eosinophils

91
Q

Release toxins to destroy virus-infected body cells

A

NK (natural killer) cells

MCAT (45 decks)

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