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MCAT > Microbiology > Flashcards

Microbiology Flashcards

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MCAT flashcards
1
Q

Viruses

A

Obligate intercellular parasites (obligated/only able) that reproduce within cells (intracellularly)

Incapable of common chemical reactions of life outside of a cell -> therefore not cells or living organisms

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2
Q

Exterior Protein Shell

A

Rigid structure of fixed size (*limiting factor) that cannot expand to incorporate a larger genome (evolved to be extremely economical to rely on host encoded proteins for transcription/translation/replication).

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3
Q

Adaptation of Multiple Proteins

A

Virus can utilize more than one reading frame within a piece of DNA so that genes can overlap

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4
Q

Capsid

A

Protein coat surrounding viral nucleic acid genome -> made from repeating pattern of few protein building blocks

Helical (rod shaped)
Polyhedral (multiple sided geometric figures)

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5
Q

Capsid Heat

A

Within which the genome is located

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6
Q

Tail Fibers

A

Attach to the surface of the host cell

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7
Q

Base Plate

A

Attached to surface of host cell (connected to the tail fibers, connected to central shaft/sheath)

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8
Q

Sheath

A

Contracts using energy of stored ATP injecting genome into the host

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9
Q

Envelope

A

In animal viruses that surrounds capsid (containing phospholipids, proteins, and carbohydrates) -> derived from host cell

Budding through host cell membrane

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10
Q

Naked Virus

A

Virus without envelop (phages and plant viruses)

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11
Q

Bacteriophage

A

Viruses that use bacteria as host (bind to exterior of bacterial cell). Can then enter lytic or Lysogenic cycle

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12
Q

Penetration

A

AKA eclipse, injection of viral genome into host cell

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13
Q

Lytic Cycle

A
  1. Attachment of phage to E. coli and injection of phage chromosome
  2. Breakdown of bacterial chromosome by phage-specific enzyme
  3. Bacterial chromosome totally broken down
  4. Replication of Phage chromosome using bacterial materials + phage enzymes
  5. Expression of phage genes to produce phage structural components
  6. Assembly of progeny phage particles
  7. Release of progeny phage by lysis of bacterial wall
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14
Q

Early Gene

Ex. Hydrolase

A

Genes that are immediately expressed after infection

Hydrolytic enzyme that degrades the entire host genome

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15
Q

Late Gene

Ex. Lysozyme

A

Created later

Destroys bacterial cell wall -> host bacterium bursts (‘lyses’)

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16
Q

Lysogenic Cycle

A
  1. Phage binds to bacterium
  2. Phage DNA enters host cell
  3. The phage DNA integrates and becomes noninfective prophage
  4. Chromosome with integrated prophage (phage genome incorporated into bacterial genome) replicates
  5. In rare cases the prophage may separate and then cell is induced to lyse
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17
Q

Lysogen

A

Host of lysogenic virus

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18
Q

Excision

A

Removal of prophage from host genome that enters lytic cycle

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19
Q

Transduction

A

When excision occurs, prophage takes part of the bacterial genome with it; giving the new host a new ability

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20
Q

Animal Viruses

A
  • have specific proteins on the surface of plasma membranes that serve as specific receptors (typically play a role in regular cellular function)
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21
Q

Endocytosis

A

Method by which animal host cell engulfs virus and internalizes it

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22
Q

Uncoated

A

Viral genome after entering host being released from its capsid

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23
Q

Productive Cycle

A

Similar to lytic cycle but doesn’t destroy the host cell

Enveloped viruses exit host cell by budding (cell doesn’t lyse) the lipid bilayer can reseal as the virus leaves

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24
Q

Provirus

A

animal virus form of a prophage (in lysogenic cycle)

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25
Q

Viral Genomes

A

Determined by uniqueness of each virus (can be many factors)

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26
Q

(+) RNA viruses

A

has ss-RNA gene, gene is infective (injection will result in viral production)

ENCODE for RNA-dependent RNA polymerase that allows RNA to be replicated by RNA

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27
Q

(-) RNA viruses

A

Complementary genome to the piece of RNA that encodes viral mRNA production/proteins (creates useful polypeptides)

ENCODES for and CARRIES RNA-dependent RNA polymerase

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28
Q

Retroviruses

A

(+) RNA viruses that undergo lysogeny (integrate as proviruses)

In order to integrate into our DNA, must be composed of double stranded DNA as well. Need to make DNA from an RNA template: RNA-dependent DNA polymerase

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29
Q

Main Retroviral Genes

A

Gag (codes for viral capsid proteins)

Pol (codes for reverse transcriptase)

Env (codes for viral envelope proteins)

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30
Q

Double Stranded DNA Viruses

A

Have large genomes that include genes for enzymes involved in deoxyribonucleotide synthesis (done whenever we make DNA) and DNA replication

Encode enzymes required for dNTP synthesis/DNA replication

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31
Q

Subviral Particles

A

Infectious agents smaller and simpler than viruses

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32
Q

Prions

A

Self replicating proteins (do not follow Central Dogma), misfolded proteins that can alter shapes of normal protein

Causes transmissible spongiform encephalopathies (TSEs) but also can be genetically linked

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33
Q

Central Dogma

A

States that information flows in its nucleotide form from DNA to RNA then amino acid from RNA to protein

34
Q

TSE

A

transmissible spongiform encephalopathies that result in degeneration of the nervous system (always fatal - Mad cow disease, etc.)

35
Q

Viroid

A

Consist of short, circular ss-RNA - does not code for proteins

Mostly found in plants except Hepatitis D (enter hepatocytes, liver cells)

36
Q

Prokaryotes

A

Do not contai membrane-bound organelles: include bacteria, archae and blue-green algae

37
Q

Prokaryotic Cytoplasm Contents

A
  • Genome is a single ds-DNA circular chromosome
  • Translation/Transcription occur simultaneously in the ribosomes (polyribosomes = multiple ribosomes translating single mRNA)
  • plasmids are extrachromosomal genetic elements (circular ds-DNA, contain things like antibiotic resistance)
  • plasmids important in conjugation (bacterial exchange of information)
38
Q

Shapes

Round
Rod-shaped
Spiral Shaped

A

Cocci/Coccus
Bacilli/Bacillus
Spirilla/Spirillum

39
Q

Cell Membrane

A

Lipid Bilayer binds cytoplasm

40
Q

Cell Wall

A

Outside the cell membrane, wall composed of peptidoglycan (provides structure, target of antibiotics)

Prevents osmotic lysis (explosion)

41
Q

Protoplast

A

Bacteria with degraded cell wall (lysozyme degraded peptidoglycan) that is osmotically fragile

42
Q

Gram Staining

A

Classification type according to cell wall, derived from bacteria’s ability to change color

43
Q

Gram Positive

A

Strong purple color, thick peptidoglycan layer after cell membrane

44
Q

Gram Negative

A

Light pink staining

Thinner layer of peptidoglycan (in periplasmic space, sometimes where enzymes that degrade antibiotics is found) in cell wall but have additional outer layer containing lipopolysaccharide

45
Q

Endotoxins

A

Normal components of outer membrane of Gram-negative bacteria that aren’t inherently poisonous - but cause immune system to have extreme reaction (leads to septic shock)

46
Q

Exotoxins

A

Toxic substances secreted by both gram neg/pos bacteria into surrounding medium. Compete with other bacterial species (ex. normal inhabitants of mammalian gut) cause disease like tetanus

47
Q

Capsule

A

AKA glycocalyx, sticky layer of polysaccharide goo surround bacterial cell and makes it more difficult for immune cells to eradicate

Allows it to adhere to surfaces (i.e. lining of digestive tract)

48
Q

Flagella

A

Whip-like, long filaments that help with motility

49
Q

Flagellar Locations/Number

Monotrichous
Amphitrichous
Peritrichous

A

Flagella at one end
Flagella at each end
Multiple flagella

50
Q

Components of flagella

A

Filament, hook, and basal structure

51
Q

Pili

A

long projections involved in attaching to different surfaces in bacteria.

52
Q

Fimbriae

A

Smaller structures not involved in locomotion but help adhere to surfaces

53
Q

Temperature

A

Mesophiles - favor mild temperature
Thermophiles - high temperatures
Psychrophiles - cold temperatures

54
Q

Nutrition

A

Chemoautotroph - build organic molecules from CO2 using energy of chemicals (inorganic molecules)

Chemoheterotroph- require organic molecules lie glucose made by other organisms as their carbon source/for energy

Photoautotroph - use CO2 as carbon source and obtain energy from sun

Photoheterotroph - are odd in that they get energy from sun but require organic molecule from another organism as carbon source

55
Q

Growth Media

A

Bacteria grow in agar on petri dishes through a process called plating, eventually forming colonies (minimal media contains nothing but glucose and agar)

56
Q

Bacterial Lawn

A

Dense growth of bacteria (plaque is clear area in the lawn)

57
Q

Auxotrophs

A

Bacteria not capable of surviving on minimal medium because can’t synthesize a molecule which they need to live (requires auxiliary trophic substance to live)

58
Q

Doubling time

A

Amount of time required for a population of bacteria to double its number

59
Q

Obligate Aerobes

A

Bacteria which require oxygen

60
Q

Anaerobes

A

Do not require oxygen

61
Q

Facultative Anaerobes

A

Will use oxygen when it’s around but don’t need it

62
Q

Tolerant Anaerobes

A

Can grow in the presence or absence of oxygen but do not use it in their metabolism

63
Q

Obligate Anaerobes

A

Poisoned by oxygen (lack the enzymes necessary for the detoxification of free radicals which form spontaneously when oxygen is around) - commonly infect wounds

64
Q

Fermentation

A

Glucose catabolism uses final production of lactate

65
Q

Respiration

A

Glucose catabolism with oxygen as an electron acceptor

66
Q

Anaerobic Respiration

A

Respiration without oxygen as final electron acceptor (S, CO2, etc.)

67
Q

Binary Fission

A

Asexual bacterial reproduction - growing in size until synthesizing enough cell components for two cells then divides into two

68
Q

Conjugation

A

Exchange of genetic information of bacteria

69
Q

Phases of Bacterial Cycle

A

Lag phase - biosynthetic pathways pathways are creating items needed for bacterial growth (no increase in # cells)

Log/Exponential Phase - Exponentially grows

Stationary Phase - Cells cease to divide for lack of nutrients (maximum population at this stage is referred to as carrying capacity)

Death Phase: Exponential decrease in number of living bacterial cells

70
Q

Endospore Formation

A

Some gram-positive bacteria form endospores (thick external shells of peptidoglycan) that form under unfavorable growth conditions) under unfavorable growth conditions (Ex.high temp)

71
Q

Germination

A

Metabolic reactivation of an endospore

72
Q

Transduction

A

Transfer of genomic DNA between bacteria in the lysogenic phage

73
Q

Transformation

A

When pure DNA is added to bacterial culture, bacteria internalizes DNA under certain conditions

74
Q

Conjugation

A
  • most related to normal bacterial function

Physical contact (bridging between cellls) wherein one cell copies DNA and copies this information through bridge to other cell

75
Q

F (fertility) factor

A

Bacteria with F+ are considered male, and transfer F factor to female cells.

A circular DNA molecule that contains genes

76
Q

Hfr

A

High frequency recombination, F factor can get incorporated into the cellulary environment (these characteristics can be transferred into the F cell

77
Q

Conjugate Mapping

A

Hfr conjugation stopping at various time points can help determine the order of genetic transfer

78
Q

Archaebacteria

A

nontypical (not Eukaryotic bacteria) that live typically in extreme environments.

Cell wall lacks peptidoglycan and reproduce via fission/budding

Genetically more similar to eukaryotes (introns, similar mRNA sequences, etc.)

79
Q

Parasitic Bacteria

A

Damage host cell; modulate course of damage to ensure they have materials to survive and reproduce

Obligate - must be inside host cell to replicate

Facultative - can live and replicate inside or outside of a host cell

80
Q

Symbiotic Bacteria

A

Coexist with host where both host and cell derive benefit

Ex. bacterial flora in human gut

MCAT (7 decks)

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