MCAT BIOLOGY: Microbiology Ch 5

Question 1

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

Answer 1

Anaphase

Question 2

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

Answer 2

Attachment

Question 3

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

Answer 3

Auxotroph

Question 4

A bacterium having a rod-like shape

Answer 4

Bacillus

Question 5

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

Answer 5

Binary fission

Question 6

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

Answer 6

Chemoreceptors

Question 7

A bacterium having a round shape

Answer 7

Coccus

Question 8

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

Answer 8

Conjugation

Question 9

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

Answer 9

Endospore

Question 10

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.

Answer 10

Endotoxin

Question 11

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

Answer 11

Envelope

Question 12

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

Answer 12

Excision

Question 13

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)

Answer 13

Exotoxin

Question 14

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

Answer 14

F (fertility factor)

Question 15

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

Answer 15

Gram negative bacteria

Question 16

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

Answer 16

Gram-positive bacteria

Question 17

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

Answer 17

Hfr Bacterium

Question 18

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

Answer 18

Lawn

Question 19

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

Answer 19

Lysogenic cycle

Question 20

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

Answer 20

Lysozyme

Question 21

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

Answer 21

Lytic cycle

Question 22

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

Answer 22

Penetration

Question 23

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

Answer 23

Peptidoglycan

Question 24

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

Answer 24

Periplasmic Space

Question 25

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

Answer 25

Pilus

Question 26

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

Answer 26

Plaque

Question 27

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

Answer 27

Prions

Question 28

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

Answer 28

Productive cycle

Question 29

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

Answer 29

Retrovirus

Question 30

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

Answer 30

Reverse transcriptase

Question 31

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

Answer 31

RNA dependent RNA polymerase

Question 32

A bacteria having a spiral shape

Answer 32

Spirochete

Question 33

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

Answer 33

Transduction

Question 34

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

Answer 34

Viroids

Question 35

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?

Answer 35

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

Question 36

How are viruses classified?

Answer 36

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

Question 37

How do viruses develop an envelope?

Answer 37

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

Question 38

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

Answer 38

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

Question 39

Why would phages and plant viruses not have enveloped?

Answer 39

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

Question 40

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

Answer 40

Hydrolase is a hydrolytic enzym that degrades the entire host genome

Question 41

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

Answer 41

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

Question 42

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

Answer 42

prophage

Question 43

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

Answer 43

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

Question 44

Many animal viruses enter cells by ___

Answer 44

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

Question 45

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

Answer 45

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

Question 46

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

Answer 46

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

Question 47

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

Answer 47

provirus

Question 48

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

Answer 48

RNA-dependent RNA polymerase

Question 49

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?

Answer 49

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.

Question 50

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

Answer 50

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

Question 51

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

Answer 51

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

Question 52

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

Answer 52

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

Question 53

What must a retrovirus encode for ?

Answer 53

Reverse transcriptase an RNA-dependent DNA polymerase

Question 54

What is a retrovirus?

Answer 54

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

Question 55

What are the three main retroviral genes?

Answer 55

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

Question 56

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

Answer 56

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

Question 57

How do prions affect host nervous tissue?

Answer 57

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

Question 58

Describe the genome of prokaryotes

Answer 58

- 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

Question 59

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

Answer 59

Plasmid

Question 60

What two things make plasmids important?

Answer 60

- encode advantageous gene products | - orchestrate bacterial exchange of genetic information (conjugation)

Question 61

___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

Answer 61

Endotoxins

Question 62

___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

Answer 62

Exotoxins

Question 63

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

Answer 63

Capsule or glycocalyx

Question 64

___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

Answer 64

Glycocalyx or capsule

Question 65

___means bacteria have flagellum located only at one end

Answer 65

Monotrichous

Question 66

___means bacteria have flagella at both ends

Answer 66

Amphitrichous

Question 67

___means bacteria has multiple flagella

Answer 67

Peritrichous

Question 68

What is the difference between the eukaryotic and prokaryotic flagellum?

Answer 68

The eukaryotic flagella contains 9+2 arrangement of microtubules

Question 69

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

Answer 69

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

Question 70

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

Answer 70

Chemoreceptors

Question 71

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

Answer 71

Pili

Question 72

____are smaller than pili and involved in adhering to surfaces

Answer 72

Fimbriae

Question 73

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

Answer 73

Respiration

Question 74

___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

Answer 74

Fermentation

Question 75

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

Answer 75

32 ATP

Question 76

How much ATP is produced through glucose fermentation by prokaryotes?

Answer 76

2 ATP

Question 77

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

Answer 77

Endospores

Question 78

What are found within a bacterial endospore?

Answer 78

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

Question 79

Bacteria have 3 mechaniss of acquiring new genetic material

Answer 79

Transduction Conjugation Transformation

Question 80

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

Answer 80

Transduction

Question 81

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__

Answer 81

Transformation

Question 82

___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

Answer 82

Conjugation

Question 83

Identify foreign pathogens, antigen presenting and produce antibodies

Answer 83

B cells

Question 84

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

Answer 84

T cells

Question 85

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

Answer 85

Dendritic cells

Question 86

Degrading pathogens and dead body cells via phagocytosis

Answer 86

Macrophages

Question 87

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

Answer 87

Basophils

Question 88

Releasing chemical mediators such as histamines that modulate an allergic reaction

Answer 88

Mast cells

Question 89

Killing and phagocytizing bacteria cells

Answer 89

Neutrophils

Question 90

Defending against parasitic infections and modulating immune responses during allergic reaction

Answer 90

Eosinophils

Question 91

Release toxins to destroy virus-infected body cells

Answer 91

NK (natural killer) cells