Microbiology

Question 1

The oldest form of cellular life. They are defined by the absence of a nucleus and membrane-bound organelles.

Answer 1

Prokaryotes

Question 2

What are the two domains of life of prokaryotes?

Answer 2

Archaea and Bacteria

Question 3

These are unicellular organisms that have been traditionally known as extremophiles, capable of inhibiting environments with high salinity or extreme temperatures.

Answer 3

Archaea

Question 4

How does archaea resemble both bacteria and eukaryotic cells?

Answer 4

They resemble bacteria with their lack of nuclei and membrane-bound organelles. They resemble eukaryotic cells in terms of certain genes and enzymes used in metabolic pathways. Furthermore, they use organic compounds such as ammonia, metal ions, and even hydrogen.

Question 5

Example of mutualistic relationship of bacteria with the body?

Answer 5

Vitamins K and B7 are produced in the gut by bacteria

Question 6

Spherical bacteria are known as

Answer 6

Cocci

Question 7

Rod-shaped bacteria are called

Answer 7

Bacilli

Question 8

Spiral-shaped bacteria are known as

Answer 8

Spirilla

Question 9

Bacteria that do not require oxygen for metabolism are known as

Answer 9

Anaerobes

Question 10

Oxygen is toxic for this bacteria

Answer 10

Obligate anaerobes

Question 11

Bacteria that can engage in aerobic or anaerobic metabolism, depending on circumstances

Answer 11

Facultative anaerobes

Question 12

Unlike eukaryotes, bacteria have cell wall that encloses a cell membrane which provides structural support in a range of environments. It is characterized by by the presence of a polysaccharide known as?

Answer 12

Peptidoglycan- gives cell wall its rigidity

Question 13

This process is used to differentiate between the two main types of bacterial cell walls which contain different quantities of peptidoglycan

Answer 13

Gram staining

Question 14

Which are gram-positive bacteria and which are gram-negative?

Answer 14

Gram-positive bacteria have cells with extensive peptidoglycan structures while gram-negative have a thin peptidoglycan layer surrounded by a liposaccharide outer membrane

Question 15

Gram staining instructions

Answer 15

See biology book, pg.44

Question 16

Colors of gram-positive and negative

Answer 16

Positive- deep purple

Negative- pink

Question 17

Describe sedimentation rate. It refers to how long it takes a particle to sink to the bottom of a test tube under high-intensity centrifugation.

Answer 17

Svedberg Units

Question 18

The Svedberg units are proportional to ?

Answer 18

Mass- larger particles take longer to sediment (but this is not a linear relationship)

Question 19

Clinical importance of the difference between prokaryotic and eukaryotic ribosomes?

Answer 19

Ribosomes can be a target of antibiotics

Question 20

Difference in the movement of flagella in bacteria and eukaryotes

Answer 20

Bacteria- rotational movement

Eukaryotes- whipping motion

Question 21

Which part of the flagella is where the rotation takes place?

Answer 21

Basal body

Question 22

The three components of flagella

Answer 22

Filament, basal body, and hook

Question 23

Movement in response to chemical signals is known as

Answer 23

Chemotaxis

Question 24

The bacteria’s genetic material is contained in a single circular chromosome that tends to congregate in a region of the cell known as the

Answer 24

Nucleoid region

Question 25

T or F. Unlike eukaryotes, prokaryotes can carry out transcription and translation simultaneously

Answer 25

True.

Question 26

In addition to the main chromosome, prokaryotes often contain small circular pieces of DNA known as

Answer 26

Plasmids

Question 27

*Important info regarding PLASMIDS

Answer 27

They generally code for advantageous but non-essential abilities, and play a major role in ANTIBIOTIC RESISTANCE. They also often code for virulence factors

Question 28

Refers to anything that allows a bacterial infection to be more virulent, or harmful to the host

Answer 28

Virulence factors

Question 29

Bacteria reproduce through what process?

Answer 29

Binary Fission

Question 30

Mitosis occurs in eukaryotes and binary fission occurs in prokaryotes

Answer 30

They are not the same!! Bacteria have neither linear chromosomes nor a proper cytoskeleton.

Question 31

Steps of Binary Fission

Answer 31

1. Replication- the chromosome is duplicated while the cell grows 2. Segregation and growth of a new cell wall- chromosomes are pulled towards different sides of the cell envelope begins to grow towards the middle of the cell 3. Separation of two daughter cells

Question 32

The Bacterial growth curve

Answer 32

1. Lag phase- they adapt to environment 2. Exponential or log phase 3. Stationary phase- environment is unable to sustain growth 4. Death phase- resources are exhausted

Question 33

Bacteria can engage in horizontal gene transfer through three mechanisms

Answer 33

Transformation, Transduction, and Conjugation

Question 34

Refers to the ability of some bacteria to absorb genetic material directly form the environment

Answer 34

Transformation

Question 35

This is a virus-mediated gene transfer. Bacteriophages incorporate part of the bacterial genome during assembly

Answer 35

Transduction- heavily used in biotechnology

Question 36

Can be thought of as true bacterial equivalent of sexual reproduction, and involves type transfers of a plasmid through a bridge that is created when a sex pious on one bacterium attaches to another bacterium. The fertility factor itself is duplicated and transferred creating a new F+ cell.

Answer 36

Conjugation- major mechanism contributing to the spread of antibiotic resistance

Question 37

These are obligate intracellular parasites, which means they must hijack host cells to replicate

Answer 37

Viruses

Question 38

All viruses contain these 2 structural features

Answer 38

A genetic material, and capsid

Question 39

Important note about virus

Answer 39

Those with an envelope cannot survive for long at all in the environment (ex. HIV- has to be in bodily fluids to survive). They are easily destroyed through light, heat, or desiccation. Rotavirus (diarrhea) do not have envelope -so can be persistent in the environment

Question 40

This term is used specifically to the fully-assembled infectious virus

Answer 40

Vision

Question 41

The genetic material of viruses are single or double stranded?

Answer 41

Both! They can have single and double-stranded DNA or RNA

Question 42

The subdivision of single-stranded RNA viruses that contain mRNA that can immediately be translated by the cell.

Answer 42

Positive-sense virus

Question 43

This subdivision of single-stranded RNA viruses contain RNA that is complementary to mRNA, meaning that mRNA must be synthesized by an enzyme know as ____________ that is carried in the virion

Answer 43

Negative-sense virus, RNA replicase

Question 44

viruses whose host cells are bacteria

Answer 44

Bacteriophages

Question 45

How do bacteriophages infect bacteria?

Answer 45

They inject their genetic material through a syringe like structure known as a tail sheath. Tail fibers are used to attach to host cells

Question 46

MCAT strategy: VIRUSES (Approaches to antiviral medication)

Answer 46

1. Interfering with binding/ cell entry 2. Process of synthesizing new genetic material 3. Blocking/ translation 4. Interfering with the assembly of viral proteins

Question 47

Retroviruses are distinct class of which type of virus

Answer 47

Single-stranded RNA

Question 48

Retroviruses use an enzyme known as _________ __________ to synthesize DNA from their RNA genome. This DNA is then incorporated into the genome of the host cell, where it replicates along with the host

Answer 48

Reverse transcriptase

Question 49

What makes pathogenic retroviruses so hard to kill?

Answer 49

They cannot be killed without killing their host cells | Ex. HIV

Question 50

Clinical application of reverse transcriptase

Answer 50

It is used to generate complementary DNA (cDNA) sequences from RNA in the lab

Question 51

RNA virus vs DNA virus: expression of protein-encoding genes

Answer 51

RNA virus- can accomplish this in the cytoplasm itself DNA virus- needs to get into the nucleus for the mRNA to be synthesized *Viral genome must also be replicated

Question 52

Virions can be released form a host cell through a process known as _________, which is similar to exocytosis and does not damage the host cell.

Answer 52

Extrusion *virions can also be produced in such quantities that they cause the host cell to lose and spill out into the environment

Question 53

During this cycle, the bacteriophages works to replicate at full speed, making full use of the host cell’s machinery until the host cell is so full that it bursts or loses

Answer 53

Lyric cycle

Question 54

In this cycle, a bacteriophage can integrate its levels into the host genome, at which point it is referred to as a ___________ or a ___________. In response to environmental signals, the prophage can re-emerge from the host genome and resume a lytic cycle

Answer 54

Lysogenic cycle | Prophage or a provirus

Question 55

Infectious proteins. Misfolded proteins that cause other proteins to be misfolded as well, with implications for cellular function. Give example.

Answer 55

Prions | Creutzfeldt-Jakob disease or “mad cow disease, fatal familial insomnia, kuru (transmitted by cannibalism)

Question 56

Small infectious particles found in plants can silence gene expression by binding to specific RNA sequences

Answer 56

Viroids