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Biology MCAT > Chapter 1 > Flashcards

Chapter 1 Flashcards

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1
Q

M

A

A

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2
Q

Obligate Aerobes (a type of bacteria)

A

Requires oxygen for metabolism

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3
Q

Anaerobes ( a type of bacteria)

A

Does not require oxygen (uses fermentation or other form of cellular metabolism)

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4
Q

What are the 3 types of anaerobes?

A

Obligate anaerobes = cannot survive in oxygen (leads to production of reactive-oxygen containing radicals which leads to cell death)

Facultative anaerobe = survives in both presence and absence in oxygen

Aerotolerant anaerobe = unable to use oxygen

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5
Q

Define Prokaryote

A

1) Lacks a nucleus
2) Lacks membrane-bound organelles (Ex: doesn’t have mitochondria)
3) single-called organisms (30S and 50S subunits)
4) contains a cell membrane (used for electron transport chain and generation of ATP)

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6
Q

What is the Prokaryote cell structure?

A

Flagellum, DNA (nucleoid region), cell membrane, cell wall, ribosome

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7
Q

Define Envelope and what is its function

A

Envelope = cell wall (outer layer of the cell) + Cell membrane (plasma membrane made of phospholipids)

Function: To protect itself from the environment

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8
Q

Function of the cell wall is..

A

1) Provides Structure
2) Controls the movement of solutes into and out of the bacterium (allows the cell to maintain a concentration gradient relative to the environment)

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9
Q

What are the 2 types of cell walls? (Provide colors)

A

Gram positive (pink-red) and Gram negative (purple)

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10
Q

Why are Gram-negative cells purple? Why are Gram-positive cells pink-red?

A

The envelope absorbs the crystal violet stain; the envelope does not absorb the crystal violet stain, but absorbs the Safranin counterstain

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11
Q

Describe the cell walls of Gram-positive and Gram-negative

A

Gram-positive cell walls = Plasma membrane < thick layer of peptidoglycan that contains lipoteichoic acid (human immune system may be activated by exposure to this acid)

Gram-negative cell walls = Plasma membrane < Periplasmic space (empty space between ) < thin layer of peptidoglycan < outer membrane (contains phospholipids and lipopolysaccharides [this is called LPS and triggers immune response in humans])

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12
Q

Define flagella and its function

A

Long, whip-like structures that can be used for:

1) Propulsion
2) Move towards food or away from toxins or immune cells (chemotaxis)

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13
Q

Define chemotaxis

A

Ability of a cell to detect chemical stimuli and move toward or away

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14
Q

what four basic tenets described in the cell theory apply for living organisms ?

A

-all living things are composed of cells
-the cell is the basis foundational unit of life
-cells arise only from preexisting cells
-Cells carry genetic information in the form of deoxyribonucleic acid (DNA).
This genetic material is passed on from parent to daughter cell.

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15
Q

What tenets do viral cells violate and what does this violation consider the living or nonliving ?

A

Third and fourth tenet, no living

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16
Q

What is the structure of flagella (flagellum)?

A

Composed of a filament, a basal body, and a hook

Filament = a hollow, helical structure composed of flagellin
Hook = Connects the filament and the basal body (this allows for exertion of torque on the filament by the basal body as it rotates, thus allowing the bacterium to propel forward)
Basal body = a complex structure that anchors the flagellum to the cytoplasmic membrane and is also the motor of the flagellum

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17
Q

Define plasmids

A

Circular structures of DNA that can be absorbed by bacteria cell (this can lead to negative or positive effects on bacteria)

Note: Plasmids don’t change the genome of the bacteria. After absorption, there is two circular DNA: the original bacteria DNA and the absorbed foreign plasmid circular DNA

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18
Q

Do prokaryotic cells have a nucleus ?
How many cells are in prokaryotic cells?

A

-Always single celled
-do not contain nucleus

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19
Q

How can plasmids benefit/harm a bacterium?

A

Typically, bacterium may acquire/absorb DNA from external sources. This is found in circular plasmids that may provide an advantage to the bacteria such as antibiotic resistance or disadvantage through virulence factors

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20
Q

Where are the organelles suspended in?

A

Membrane enclosing semifluid cytosol

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21
Q

Define Binary Fission and its steps

A

Simple form of asexual reproduction in prokaryotes

1) Circular chromosome (DNA) of prokaryote cell attaches to the cell wall
2) DNA replicates (meanwhile the cell grows in size)
3) Plasma membrane and cell wall begin to grow inward (along the midline of the cell)
4) Produces 2 identical daughter cells (each has its own DNA)

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22
Q

Membranes of eukaryotic cells consist of …

A

Phospholipid bilayer.

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23
Q

What is the function of the cytosol?

A

The cytosol allows for the diffusion of molecules throughout the cell.

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24
Q

In the nucleus how is genetic material enclosed ?

A

Within the nucleus, genetic material is encoded in deoxyribonuclic acid (DNA),

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25
Q

How is genetic material in the nucleus organized?

A

Organized into chromosomes

26
Q

Define episomes

A

A subset of plasmids capable of integrating into the genome of the bacterium

27
Q

What process do eukaryotic cells reproduce by? And what does this process form?

A

Eukaryotic cells reproduce by mitosis, allowing for the formation of two identical daughter cells.

28
Q

Define Transformation

A

This is a result of:

Integration of foreign genetic material into the host genome

29
Q

Define Transformation

A

This is a result of:

Integration of foreign genetic material into the host genome

30
Q

control center of the cell contains …

A

Nucleus, most tested organelle

contains all of the genetic material necessary for replication of the cell

31
Q

What is the nucleus surrounded by ?

A

surrounded by the nuclear membrane or envelope, a double membrane that maintains a nuclear environment separate and distinct from the cytoplasm.

32
Q

What does the nuclear envelope create ?

A

Two distinct environments within the cell because it separates separates the nucleus from the cytoplasm creating compartmentalization

33
Q

Define Conjugation and how does it occur

A

Bacterial form of mating (Sexual reproduction); it is unidirectional

Donor (+) has a sex pili that connects to the Recipient (-), which forms the conjugation bridge that facilitates the transfer of genetic material

34
Q

Define the F (fertility factor) and how it works

A

a plasmid sex factor present in the Donor(+) bacteria (this bacteria is called F+ cells).

During conjugation, the F+ cell replicates its F factor and donates the copy to the F- cell, converting it to an F+ cell; thus enabling this new F+ cell to donate the plasmid to other F- cells

35
Q

What does the nuclear pore allow ?

A

Nuclear pores in the nuclear membrane allow selective two-way exchange of material between the cytoplasm and the nucleus.

36
Q

What is the genetic material (DNA) contains coding regions called?

A

Genes

37
Q

What is linear dna wound upon ?

A

organizing proteins known as histones,

38
Q

After his tones was is dna further winded linear strands called ?

A

Chromosomes

39
Q

What is the subsection of the nucleus called ?

A

nucleolus, takes up approximately 25 percent of the volume of the entire nucleus

40
Q

Define Hfr

A

High Frequency of recombination ; these are cells that have undergone the change of bacterial conjugation (specifically getting the F factor)

41
Q

What is synthesized in the nucleolus ?

A

Ribosomal DNA (rRNA)

42
Q

Define Transduction

A

A genetic recombination process that requires a vector (a virus that carries genetic material from one bacterium to another)

43
Q

Define Viruse

A

Obligate intracellular pathogens; this means they cannot reproduce outside of a host cell

44
Q

Define bacteriophages

A

Viruses that infect bacteria and can incorporate a segment of host DNA during assembly

45
Q

Define Transposons . Do transposons disrupt genes?

A

Genetic elements capable of inserting and removing themselves from the genome

Transposons can disrupt genes, only if it is inserted within a coding region of a gene

46
Q

What assumptions are made when bacteria reproduces via binary fission?

A

Assumptions:
1) all of Bacteria are exactly the same in a local colony (assuming no mutations or genetic recombination)
2) No bacteria are dividing faster than the others

47
Q

What is the Bacteria Growth Curve? What are its different phases?( (Search the image for clarification)

A

1) Lag Phase - Little to Zero growth; as bacteria are adapting to their new environment
2) Exponential Phase - Rate of division increases (highest growth seen here); bacteria adapted
3) Stationary Phase - Little to Zero growth; reduction of resources account for this growth
4) Death Phase - Negative growth; depletion of resources

48
Q

What is the structure of a bacteriophage (in other words: viral structure) ? (Search up image for clarity)

A

Body: Genetic information stored inside < Capsid (protein coat) < Envelope (made of lipids) [not all viruses have an envelope]
Legs: Under the body is the Tail Shealth < under the Tail Shealth is the tail fibers

Genetic information = can be either circular or linear, can be either single-stranded DNA, single-stranded RNA, double-stranded DNA, or double-stranded RNA

49
Q

Nonenveloped viruses vs Enveloped Viruses; List the disadvantages of an envelope

A

The viral structure contains the envelope around the capsid in envelope viruses; in non-enveloped viruses there is no envelope present

Envelope is very sensitive to heat, detergents, and desiccation (dryness); thus, enveloped viruses are easier to kill. On the other hand, viruses that don’t have an envelope are more resistant to sterilization and are likely to persist on surfaces for an extended period of time

50
Q

Why are viruses considered as obligate intracellular parasites?

A

Viruses must express and replicate genetic information within a host cell because they lack ribosomes to carry out protein synthesis; After hijacking a cell’s machinery, a virus will replicate and produce viral progeny (virions) which can be released to infect additional cells

51
Q

Define Tail Shealth and Tail Fibers

A

Tail Shealth = acts like a syringe; they inject their genetic material into a bacteria
Tail Fibers = help the bacteriophage recognize and connect to the correct host cell

52
Q

Define bacteriophages

A

Viruses that target bacteria

53
Q

What are the 2 types of single-stranded RNA viruses?

A

+ Sense = Implies that the genome may be directly translated to functional proteins by the ribosomes of the host cell
- Sense = Implies that the negative RNA strand acts as a template strand for synthesis of a complementary strand which can then be used as a template for protein synthesis

54
Q

In negative-sense RNA strands, how is the complementary strand made?

A

Negative-sense RNA viruses must carry an RNA replicase in the virion to ensure that the complementary strand is synthesized

55
Q

Define retroviruses and how do they function?

A

Retroviruses = enveloped, single-stranded RNA viruses that carries an enzyme called Reverse Transcriptase

Reverse transcriptase synthesizes DNA from single-stranded RNA —> the DNA is then integrated into the host cell genome (basically the virus DNA is integrated into the host DNA) —> virus DNA is replicated and transcribed via host cell’s machinery —> viral proteins are made —> more viruses are created

56
Q

Lytic cycle vs Lysogenic cycle ; how are they connected?

A

Lytic = Virulent viruses are found here; the bacteriophage maximizes the use of the cell’s machinery with little regard of the survival of the host cell; once the host is swollen with new virions, the cell lyses, and other bacteria can be infected

Connection: If bacteria doesn’t lyse, it can integrate into the host genome and enter the:

Lysogenic = Provirus or prophage found here; Virus will be replicated as the host reproduces because it is now part of the host’s genome

Connection: If the bacteria is affected by environmental factors it mat cause it to revert back to the lytic cycle

57
Q

How is the lysogenic cycle beneficial to bacteria?

A

It doesn’t kill them but makes them stronger;

Bacteria infected by one strain of phage generally makes the bacteria less susceptible to superinfection

58
Q

Prions vs Viroids

A

Prions = non-living organisms; they are infectious proteins that causes disease by triggering misfolding of other proteins

Viroids = small pathogens consisting of short circular single-stranded RNA that infects plants by binding to a large number of RNA sequences and silence genes in plant genome

59
Q

How does the misfolding mechanism of a prion work?

A

CONVERTS A HOST PROTEIN FROM A-HELICE TO B-SHEET which LEADS to reduction of the solubility of the protein AND ability of cell to degrade host protein; eventually leading to the protein to aggregate thus interfering with cell function

60
Q

How do viroids affect plants?

A

Viroids bind to large number of RNA sequences and silence genes in the plant genome; thus, preventing synthesis of necessary proteins, which results in metabolic disruption and structural damage to the cell

61
Q

Define the extrusion and productive cycle

A

A newly synthesized virus leaves the cell (in order to infect other bacteria cells) by extrusion allowing for the productive cycle

Extrusion = a virus leaves the cell by fusing with the cell’s plasma membrane
Productive cycle = extrusion allows for the cell to not be killed by the virus allowing the host cell to be used by the virus again

Biology MCAT (2 decks)

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