Chapter 1: Cells

Question 1

What are the 4 Parts of Cell Theory?

Answer 1

The cell theory has four basic tenets:

1. All living things are composed of cells.
2. The cell is the basic functional unit of life.
3. Cells arise only from preexisting cells.
4. Cells carry genetic information in the form of DNA. This genetic
   material is passed on from parent to daughter cell.

Question 2

According to Cell Theory, what are Viruses?

Answer 2

Viruses are not considered living things because they are acellular, cannot reproduce without the assistance of a host cell, and may use RNA as their genetic material.

Question 2

What are Eukaryotes?

Answer 2

Eukaryotes have membrane-bound organelles, a nucleus, and may
form multicellular organisms

Question 3

What is Cytosol?

Answer 3

The cytosol suspends the organelles and allows diffusion of molecules throughout the cell.

Question 3

What are genes?

Answer 3

DNA is organized into coding regions called genes.

A gene is a specific sequence of DNA that acts as the basic unit of heredity, passed from parents to offspring, containing instructions for making proteins which ultimately determine physical traits like eye color or hair type; essentially, genes are the building blocks of our inherited characteristics

Question 3

What are cell membranes composed of?

Answer 3

The cell membrane and membranes of organelles contain phospholipids, which organize to form hydrophilic interior and exterior surfaces with a hydrophobic core.

Question 3

What is the Nucleus?

Answer 3

The nucleus contains DNA organized into chromosomes. It is surrounded by the nuclear membrane or envelope, a double membrane that contains nuclear pores for two-way exchange of materials between the nucleus and cytosol.

Question 4

What is the nucleolus?

Answer 4

The nucleolus is a subsection of the nucleus in which ribosomal
RNA (rRNA) is synthesized.

Question 5

What are Mitochondria?

Answer 5

They generate most of the chemical energy needed to power the cell’s biochemical reactions.

Mitochondria contain an outer and inner membrane.

The outer membrane forms a barrier with the cytosol; the inner membrane is folded into cristae and contains enzymes for the electron transport
chain.

Between the membranes is the intermembrane space; inside
the inner mitochondrial membrane is the mitochondrial matrix.

Mitochondria can divide independently of the nucleus via binary fission and can trigger apoptosis by releasing mitochondrial enzymes into the cytoplasm.

Question 6

What are Lysosomes?

Answer 6

contain hydrolytic enzymes that can break down substances ingested by endocytosis and cellular waste products.

When these enzymes are released, autolysis of the cell can occur.

Question 7

What is autolysis?

Answer 7

the destruction of cells or tissues by their own enzymes, especially those released by lysosomes.

Question 8

What is endoplasmic reticulum (ER)?

Answer 8

The endoplasmic reticulum (ER) is a series of interconnected membranes and is continuous with the nuclear envelope.

Question 9

What is The rough
ER (RER)?

Answer 9

The rough ER (RER) is studded with ribosomes, which permit translation of proteins destined for secretion.

Question 10

What is The smooth
ER (SER)?

Answer 10

The smooth ER (SER) is used for
lipid synthesis and detoxification.

Question 11

What is the Golgi apparatus?

Answer 11

The Golgi apparatus consists of stacked membrane-bound sacs in
which cellular products can be modified, packaged, and directed to
specific cellular locations.

Question 12

What is the Peroxisomes?

Answer 12

Peroxisomes contain hydrogen peroxide and can break down very
long chain fatty acids via β-oxidation.

They also participate in
phospholipid synthesis and the pentose phosphate pathway.

Question 13

What is the Cytoskeleton?

Answer 13

the cytoskeleton provides stability and rigidity to the overall structure
of the cell, while also providing transport pathways for molecules
within the cell.

Question 14

What is the Microfilaments?

Answer 14

Microfilaments are composed of actin. They provide structural
protection for the cell and can cause muscle contraction through
interactions with myosin. They also help form the cleavage furrow
during cytokinesis in mitosis.

Question 15

What are Centrioles?

Answer 15

Centrioles are found in
centrosomes and are involved in microtubule organization in the
mitotic spindle.

Question 16

What are Microtubules?

Answer 16

Microtubules are composed of tubulin. They create pathways for
motor proteins like kinesin and dynein to carry vesicles. ey also
contribute to the structure of cilia and flagella, where they are
organized into nine pairs of microtubules in a ring with two
microtubules at the center (9 + 2 structure).

Question 17

What is an Intermediate filaments?

Answer 17

Intermediate filaments are involved in cell–cell adhesion and
maintenance of the integrity of the cytoskeleton; they help anchor
organelles. Common examples include keratin and desmin.

Question 18

What is the Epithial tissue and Parenchyma?

Answer 18

Epithelial tissues cover the body and line its cavities, protecting against
pathogen invasion and desiccation. Some epithelial cells absorb or
secrete substances, or participate in sensation.

In most organs, epithelial cells form the parenchyma, or the
functional parts of the organ.

Epithelial cells may be polarized, with one side facing a lumen or the
outside world, and the other side facing blood vessels and structural
cells.

Question 19

What are the Epithelial layers?

Answer 19

Epithelia can be classified by the number of layers:
1. simple epithelia: have one layer,
2. stratified epithelia have many layers
3. pseudostratified epithelia appear to have multiple layers due to
differences in cell heights, but actually have only one layer

Question 20

Epithelial classified by ____ and name them:

Answer 20

Epithelia can be classified by the shapes of the cells:
1. cuboidal cells are cube-shaped,
2. columnar cells are long and narrow,
3. squamous cells are flat and scale-like.

Question 21

What are Connective tissue?

Answer 21

Connective tissues support the body and provide a framework for
epithelial cells.

Bone, cartilage, tendons, ligaments, adipose tissue, and blood are all
connective tissues.

Question 22

What is the stroma?

Answer 22

In most organs, connective tissues form the stroma or support
structure by secreting materials to form an extracellular matrix.

Question 23

What are prokaryotes?

Answer 23

Prokaryotes do not contain membrane-bound organelles; they contain their genetic material in a single circular molecule of DNA located in the nucleoid region.

Question 24

3 domains of life:

Answer 24

There are three overarching domains of life; prokaryotes account for
two of these:
Archaea, Bacteria, Eukarya

Question 25

What are Archea?

Answer 25

Archaea are often extremophiles, living in harsh environments (high
temperature, high salinity, no light) and often use chemical sources of
energy (chemosynthesis) rather than light (photosynthesis).

They have similarities to both eukaryotes (start translation with
methionine, similar RNA polymerases, histones) and bacteria (single circular chromosome, divide by binary fission or budding).

Question 26

What are Bacteria?

Answer 26

Bacteria have many similar structures to eukaryotes, and have
complex relationships with humans, including mutualistic symbiosis
and pathogenesis.

Question 27

What is mutualistic symbiosis

Answer 27

Mutualistic symbiosis is when two different organisms live together and help each other out, benefiting both. It’s like a friendship where both sides gain something.

For example:

Bees and flowers: Bees get food (nectar) from flowers, and flowers get help with pollination as bees spread their pollen to other flowers.
Humans and gut bacteria: Humans provide food and a home for the bacteria, and the bacteria help break down food and make vitamins for us.
In mutualistic symbiosis, both partners win!

Question 28

What is pathogenesis?

Answer 28

Pathogenesis is the process by which a disease develops and progresses in the body. It explains how an illness starts, what causes it, and how it spreads or damages the body.

For example, when a harmful bacteria or virus enters your body, pathogenesis describes how it invades cells, avoids the immune system, and causes symptoms like fever or inflammation. It’s essentially the story of how a disease begins and unfolds inside an organism.

Question 29

What are Eukarya

Answer 29

Eukarya are the only non-prokaryotic domain

Eukarya are one of the three domains of life, and they include all living things made up of eukaryotic cells. Eukaryotic cells are special because they have a nucleus (a compartment that holds the cell’s DNA) and other membrane-bound organelles like mitochondria.

Organisms in the Eukarya domain include:

Animals (like humans, cats, and insects)
Plants (like trees and flowers)
Fungi (like mushrooms and yeast)
Protists (like algae and amoebas)
These are more complex than bacteria or archaea (which belong to different domains) because of their organized internal structure.

Question 30

Bacteria can be classified by shape, name the shapes:

Answer 30

1. Spherical bacteria are called cocci.
2. Rod-shaped bacteria are called bacilli.
3. Spiral-shaped bacteria are called spirilli.

Question 31

Bacteria can be classified based on metabolic processes:
name them

Answer 31

Obligate aerobe
Obligate anaerobes
Facultative anaerobes
Aerotolerant anaerobes

Question 32

What is an Obligate aerobe

Answer 32

require oxygen for metabolism.

Question 33

What is an Obligate anaerobe

Answer 33

cannot survive in oxygen-containing
environments and can only carry out anaerobic metabolism.

Question 34

What is a Facultative anaerobes

Answer 34

can survive in environments with or without oxygen and will toggle between metabolic processes based on the environment

Question 35

What is an Aerotolerant anaerobes

Answer 35

cannot use oxygen for metabolism, but can survive in an oxygen-containing environment.

Question 36

The cell wall and cell membrane of bacteria form the ________

Answer 36

The cell wall and cell membrane of bacteria form the envelope.
Together, they control the movement of solutes into and out of the cell.

Question 37

Bacteria can be classified by the color their cell walls.

Explain the procedure and colors of gram + and gram -

Answer 37

Bacteria can be classified by the color their cell walls turn during Gram staining with a crystal violet stain, followed by a counterstain with safranin.

Gram-positive bacteria turn purple, while gramnegative bacteria turn pink-red.

Question 38

What’s in a gram + cell wall?

Answer 38

Gram-positive bacteria have a thick cell wall composed of peptidoglycan and lipoteichoic acid.

Question 39

What’s in a gram + cell wall?

Answer 39

Gram-negative bacteria have a thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides.

Question 40

What is chemotaxis?

Answer 40

Moving in response to chemical stimuli is called chemotaxis.

Question 41

Explain Flaeglla

Answer 41

Bacteria may have one, two, or many flagella that generate propulsion
to move the bacterium toward food or away from immune cells.

Bacterial flagella contain a filament composed of flagellin, a basal
body that anchors and rotates the flagellum, and a hook that connects
the two

Question 42

Prokaryotic Vs Eukaryotic Ribosomes:

Answer 42

Prokaryotic ribosomes are smaller than eukaryotic ribosomes (30S
and 50S, rather than 40S and 60S).

Question 42

Prokaryotes carry out the _______ _______ __________ using the cell
membrane.

Answer 42

Prokaryotes carry out the electron transport chain using the cell
membrane.

Question 43

What is binary fission?

Answer 43

Prokaryotes multiply through binary fission, in which the
chromosome replicates while the cell grows in size, until the cell wall
begins to grow inward along the midline of the cell and divides it into
two identical daughter cells.

Question 44

What are plasmids?

Answer 44

In addition to the single circular chromosome in prokaryotes,
extrachromosomal material can be carried in plasmids

Question 45

What are virulence factors?

Answer 45

Plasmids may contain antibiotic resistance genes or virulence factors.

Question 46

What are episomes?

Answer 46

Plasmids that can integrate into the genome are called episomes.

Question 47

What is transformation?

Answer 47

Transformation occurs when genetic material from the surroundings is taken up by a cell, which can incorporate this material into its genome.

https://www.youtube.com/watch?v=nvYNxoKyQp8

Question 48

Does Bacterial genetic recombination [increase or decrease] bacterial diversity.

Answer 48

Bacterial genetic recombination increases bacterial diversity

Question 49

What is conjugation

Answer 49

Conjugation is the transfer of genetic material from one bacterium
to another across a conjugation bridge; a plasmid can be transferred
from F+ cells to F– cells, or a portion of the genome can be transferred from an Hfr cell to a recipient

https://www.youtube.com/watch?v=nvYNxoKyQp8

Question 50

What is transduction?

Answer 50

Transduction is the transfer of genetic material from one bacterium
to another via a bacteriophage vector

Question 51

What are Transposons?

Answer 51

Transposons are genetic elements that can insert into or remove
themselves from the genome

Question 52

Bacterial growth graph:

Answer 52

Bacterial growth follows a predictable pattern:
The bacteria adapt to new local conditions during the lag phase.

Growth then increases exponentially during the exponential (log)
phase.

As resources are reduced, growth levels off during the stationary
phase.

As resources are depleted, bacteria undergo a death phase.

Question 53

Parts of a Virus?

Answer 53

Viruses contain genetic material, a protein coat (capsid), and
sometimes a lipid-containing envelope.

Question 54

Viruses are obligate intracellular parasites, meaning that they cannot
survive and replicate outside of a _______

Answer 54

Viruses are obligate intracellular parasites, meaning that they cannot
survive and replicate outside of a host cell.

Question 55

Individual virus particles
are called ______.

Answer 55

Individual virus particles
are called virions.

Question 56

Bacteriophages are viruses that target bacteria. In addition to the other structures, they contain a_______ ________, which injects the genetic material into a bacterium, and _____ ______, which allow the bacteriophage to attach to the host cell.

Answer 56

Bacteriophages are viruses that target bacteria. In addition to the other structures, they contain a tail sheath, which injects the genetic material into a bacterium, and tail fibers, which allow the bacteriophage to attach to the host cell.

Question 57

Single-stranded RNA viruses may be ______ _______ (that can be
translated by the host cell)

Answer 57

Single-stranded RNA viruses may be positive sense (that can be
translated by the host cell)

Question 58

Single-stranded RNA viruses may be _____ ______ (which requires a
complementary strand to be synthesized by ____ _______ before
translation)

Answer 58

Single-stranded RNA viruses may be negative sense (which requires a
complementary strand to be synthesized by RNA replicase before
translation)

Question 59

_______ contain a single-stranded RNA genome, from which a
complementary DNA strand is made using ______ ______
The DNA strand can then be integrated into the genome.

Answer 59

Retroviruses contain a single-stranded RNA genome, from which a
complementary DNA strand is made using reverse transcriptase.
The DNA strand can then be integrated into the genome.

Question 60

Explain the procedure of viruses infecting cells

Answer 60

Viruses infect cells by attaching to specific receptors, and can then
enter the cell by fusing with the plasma membrane, being brought in byendocytosis, or injecting their genome into the cell.

Thee virus reproduces by replicating and translating genetic material
using the host cell’s ribosomes, tRNA, amino acids, and enzymes.

Viral progeny are released through cell death, lysis, or extrusion.

Question 61

What is extrusion of viruses

Answer 61

Viral extrusion is the process by which a virus leaves a host cell without destroying it. It’s a way for some viruses to exit the cell and continue spreading, while keeping the host cell alive so it can make more virus particles.

Think of it like a virus sneaking out of the cell, similar to someone carefully opening a door and stepping out without breaking anything. The virus buds off from the cell membrane, taking a bit of the membrane with it, and leaves to infect other cells. This way, the host cell can keep functioning and continue making more viruses.

It’s different from processes like lysis, where the virus bursts the host cell open, killing it in the process.

Question 62

In the lytic cycle, the bacteriophage produces massive numbers of
new virions until the cell lyses. Bacteria in this phase are termed
virulent.

Answer 62

In the lytic cycle, the bacteriophage produces massive numbers of
new virions until the cell lyses. Bacteria in this phase are termed
virulent.

Question 63

What does virulent mean?

Answer 63

Virulent refers to how harmful or deadly a pathogen, like a virus or bacteria, is. The more virulent a pathogen, the more severe or intense the disease it causes.

For example, a virulent virus spreads quickly and causes serious symptoms, while a less virulent one might cause mild illness. Essentially, it’s a measure of how nasty or dangerous an infectious agent can be.

*pictur

Question 64

what is the lysogenic cycle?

Answer 64

In the lysogenic cycle, the virus integrates into the host genome as a
provirus or prophage, which can then reproduce along with the cell.
The provirus can remain in the genome indefinitely, or may leave the
genome in response to a stimulus and enter the lytic cycle.

Question 65

What are Prions?

Answer 65

Prions are infectious proteins that trigger misfolding of other proteins,
usually converting an α-helical structure to a β-pleated sheet. is
decreases the solubility of the protein and increases its resistance to
degradation.

Question 66

What are viroids?

Answer 66

Viroids are plant pathogens that are small circles of complementary
RNA that can turn off genes, resulting in metabolic and structural
changes and, potentially, cell death.

Question 67

What are the four fundamental tenets of the cell theory?

Answer 67

All living things are made of cells. e cell is the basic functional unit of
life. All cells arise from other cells. Genetic information is carried in the
form of deoxyribonucleic acid (DNA) and is passed from parent to
daughter cell.

Question 68

questions.
1. Briefly describe the functions of each of the organelles listed below:

Nucleus:
Mitochondrion:
Lysosome:
Rough endoplasmic reticulum:
Smooth endoplasmic reticulum:
Golgi apparatus:
Peroxisome:

Answer 68

The nucleus stores genetic information and is the site of transcription.

The mitochondria are involved in ATP production and apoptosis.

Lysosomes break down cellular waste products and molecules ingested
through endocytosis, and can also be involved in apoptosis.

The rough endoplasmic reticulum synthesizes proteins destined for secretion.

The smooth endoplasmic reticulum is involved in lipid synthesis and
detoxification.

The Golgi apparatus packages, modifies, and distributes
cellular products.

Peroxisomes break down very long chain fatty acids, synthesize lipids, and contribute to the pentose phosphate pathway.

Question 69

A child is diagnosed with an enzyme deficiency that prevents the
production of hydrogen peroxide. What would the likely outcome be of
such a deficiency?

Answer 69

Peroxisomes are dependent on hydrogen peroxide for their functions, so an enzyme deficiency that results in an inability to form hydrogen peroxide would likely result in an inability to digest very long chain fatty acids. These fatty acids would build up in peroxisomes until they displaced cellular contents, ultimately resulting in cell death.

Question 70

What are the predominant proteins in each cytoskeletal element?

Microfilaments:
Microtubules:
Intermediate filaments:

Answer 70

Microfilaments are composed of actin.

Microtubules are composed of
tubulin.

Intermediate filaments differ by cell type, but may be composed
of keratin, desmin, vimentin, and lamins.

Question 71

How do the cytoskeletal structures of centrioles and flagella differ?

Answer 71

Centrioles consist of nine triplets of microtubules around a hollow center,
while flagella consist of nine doublets on the outside, with two
microtubules on the inside.

Question 72

Classify each of the following cells as epithelial cells or connective tissue:
Fibroblasts, which produce collagen in a number of organs:

Endothelial cells, which line blood vessels:

α-cells, which produce glucagon in the pancreas:

Osteoblasts, which produce osteoid, the material that hardens into
bone:

chrondoblasts which produce cartilage:

Answer 72

Endothelial cells and α-cells are epithelial cells. Fibroblasts, osteoblasts,
and chondroblasts are connective tissue cells.

Question 73

In what ways are Archaea similar to bacteria?

Answer 73

Archaea are similar to bacteria in that both are single-celled organisms
that lack a nucleus or membrane-bound organelles, contain a single
circular chromosome, and divide by binary fission or budding.

Question 74

In what ways are Archaea
similar to eukaryotes?

Answer 74

They are similar to eukaryotes in that they start translation with methionine, contain similar RNA polymerases, and contain DNA associated with histones.

Question 75

What are the three common shapes of bacteria?

Answer 75

The three common shapes of bacteria are spherical (cocci), rod-shaped (bacilli), and spiral-shaped (spirilli)

Question 76

What difference between the envelopes of gram-positive and gramnegative bacteria make gram-positive bacteria more susceptible to
antibiotics such as penicillin?

Answer 76

The antibiotic penicillin targets the enzyme that catalyzes the crosslinking of peptidoglycan. Gram-positive bacteria have a thick layer of
peptidoglycan and lipoteichoic acid, and contain no outer membrane,
whereas gram-negative bacteria have only a thin layer of peptidoglycan
but also have an outer membrane containing lipopolysaccharides and
phospholipids. Penicillin and antibiotics with similar function can more easily reach and weaken the peptidoglycan layer of gram-positive
bacteria

Question 77

How do the structures of eukaryotic and prokaryotic flagella differ?

Answer 77

Eukaryotic flagella contain microtubules composed of tubulin, organized in a 9 + 2 arrangement.

Bacterial flagella are made of flagellin and consist of a filament, a basal body, and a hook

Question 78

Briefly describe the three mechanisms of bacterial genetic recombination:
Transformation, Conjugation, Transduction

Answer 78

Transformation is the acquisition of exogenous genetic material that can
be integrated into the bacterial genome.

Conjugation is the transfer of genetic material from one bacterium to another across a conjugation
bridge; a plasmid can be transferred from F+ cells to F − cells, or a portion
of the genome can be transferred from an Hfr cell to a recipient.

Transduction is the transfer of genetic material from one bacterium to
another by a bacteriophage.

Question 79

Why are viruses considered obligate intracellular parasites?

Answer 79

Viruses do not contain organelles such as ribosomes; therefore, in order
to reproduce and synthesize proteins, viruses must infect cells and hijack
their machinery.

Question 80

A coronavirus, which causes the common cold, is described as an
enveloped, single-stranded positive-sense RNA virus. What does this
indicate about the virus?

Answer 80

This description indicates that the virus contains an outer layer of
phospholipids with an inner capsid. Within the capsid, there is singlestranded RNA that can be immediately translated to protein by the
ribosomes of the host cell.

Question 81

Briefly describe the pathway of retroviral nucleic acids from infection of a
host cell to release of viral progeny:

Answer 81

The nucleic acid enters as single-stranded RNA, which undergoes reverse transcription (using reverse transcriptase) to form double-stranded DNA.
This DNA enters the host genome and replicates with the host cell.

The DNA is transcribed to mRNA, which can be used to make structural
proteins.
This mRNA doubles as the viral genome for new virions. Once
new virions are assembled from the structural proteins and mRNA
(single-stranded RNA) genome, the virions can be released to infect
other cells.

Question 82

What are the differences between the lytic and lysogenic cycles?

Answer 82

In the lytic cycle, bacteriophages replicate in the host cell in extremely
high numbers until the host cell lyses and releases the virions.

In the
lysogenic cycle, the bacteriophage genome enters the host genome and
replicates with the host cell as a provirus. In response to an appropriate stimulus, the provirus may leave the host genome and can be used to synthesize new virions.

Question 83

How do prions cause disease?

Answer 83

Prions cause disease by triggering a change in the conformation of a
protein from an α-helix to a β-pleated sheet. This change reduces
solubility of the protein and makes it highly resistant to degradation.

Question 84

Hyperbaric oxygen may be used as a treatment for certain types of bacterial infections. In this therapy, the patient is placed in a chamber in which the partial pressure of oxygen is significantly increased, increasing the partial pressure of oxygen in the patient’s tissues. This treatment is most likely used for infections with:

A. obligate aerobic bacteria.
B. facultative anaerobic bacteria.
C. aerotolerant anaerobic bacteria.
D. obligate anaerobic bacteria.

Answer 84

D
Obligate anaerobes cannot survive in the presence of oxygen and would likely be killed by such a therapy, treating the infection. The other types of bacteria listed can all survive in the presence of oxygen, so infections involving these bacteria would
likely not be treated using this therapy.

Question 85

Which of the following does NOT describe connective tissue cells?

A. They account for most cells in muscles, bones, and tendons.
B. They secrete substances to form the extracellular matrix.
C. In organs, they tend to form the stroma.
D. In organs, they provide support for epithelial cells

Answer 85

A
While bones and tendons are composed predominantly of connective tissue cells,
muscle tissue is considered a different tissue type. Other examples of connective tissue include cartilage, ligaments, adipose tissue, and blood.

Connective tissue often
secretes substances to form the extracellular matrix, such as collagen and elastin, eliminating (B). (C) and (D) are essentially identical and can both be eliminated: in organs, connective tissue oen forms the support structure for epithelial cells, called the stroma.

Question 86

Which of the following types of nucleic acid could form the genome of a
virus?
I. Single-stranded RNA
II. Double-stranded DNA
III. Single-stranded DNA
A. I only
B. II only
C. I and II only
D. I, II, and III

Answer 86

D
In a virus, the nucleic acid can be either DNA or RNA and—in both cases—can be either single- or double-stranded. Therefore, all of the types of nucleic acids listed
here could be used for a viral genome, making (D) the correct answer.

Question 87

The theory of spontaneous generation states that living organisms can arise
from nonliving material. In 1859, Pasteur demonstrated that no organisms emerged from sterilized growth media, weakening the theory of spontaneous generation and supporting which tenet of cell theory?

A. All living things are composed of cells.
B. The cell is the basic functional unit of life.
C. Cells arise only from preexisting cells.
D. Cells carry genetic information in the form of DNA.

Answer 87

C
The process of sterilization kills all living cells. A lack of cellular growth in these conditions supports the idea that cells can only arise from preexisting cells, matching
(C). By contrast, since this experiment did not directly visualize the cells, nor did it
analyze the genetic material, (A), (B), and (D) can be eliminated.

Question 88

Mitochondrial DNA is:
I. circular.
II. self-replicating.
III. single-stranded.
A. I only
B. II only
C. I and II only
D. I, II, and III

Answer 88

C
Mitochondria are thought to have evolved from an anaerobic prokaryote engulfing an
aerobic prokaryote and establishing a symbiotic relationship; therefore, mitochondrial
DNA, or mDNA, is likely to be similar to bacterial DNA. Both mDNA and bacterial
DNA are organized into a single circular chromosome of double-stranded DNA that
can replicate during binary fission. erefore, Statements I and II are correct, while
Statement III is incorrect.

Question 88

What is the main function of the nucleolus?
A. Ribosomal RNA synthesis
B. DNA replication
C. Cell division
D. Chromosome assembly

Answer 88

A
the nucleolus (not to be confused with the nucleus) is a dense structure within the
nucleus where ribosomal RNA (rRNA) is synthesized. (A) is therefore the correct
answer.

Question 89

Which of the following is NOT a function of the smooth endoplasmic
reticulum?
A. Lipid synthesis
B. Poison detoxification
C. Protein synthesis
D. Transport of proteins

Answer 89

C
The smooth endoplasmic reticulum is involved in the transport of materials
throughout the cell, in lipid synthesis, and in the detoxification of drugs and poisons.

Proteins from the rough ER can cross into the smooth ER, where they are secreted into cytoplasmic vesicles and transported to the Golgi apparatus.
However, protein synthesis is not a function of the smooth ER, but rather of the free ribosomes or the
ribosomes associated with the rough ER. (C) is therefore the correct answer.

Question 90

Which of the following organelles is surrounded by a single membrane?
A. Lysosomes
B. Mitochondria
C. Nuclei
D. Ribosomes

Answer 90

A
Lysosomes are vesicular organelles that digest material using hydrolytic enzymes.
ey are surrounded by a single membrane. Both mitochondria and nuclei are
surrounded by double membranes, eliminating (B) and (C). Ribosomes must not be
surrounded by membranes because they are found not only in eukaryotes but also in
prokaryotes, which lack any membrane-bound organelles. is eliminates (D)

Question 91

Which of the following is NOT a difference that would allow one to distinguish
a prokaryotic and a eukaryotic cell?
A. Ribosomal subunit weight
B. Presence of a nucleus
C. Presence of a membrane on the outside surface of the cell
D. Presence of membrane-bound organelles

Answer 91

C
Some of the main differences between prokaryotes and eukaryotes are that
prokaryotes do not have a nucleus, while eukaryotes do, eliminating (B); prokaryotes
have ribosomal subunits of 30S and 50S, while eukaryotes have ribosomal subunits of
40S and 60S, eliminating (A); and prokaryotes do not have membrane-bound
organelles, whereas eukaryotes do, eliminating (D). e presence of a membrane on
the outer surface of the cell could not distinguish a prokaryotic cell from a eukaryotic
one because both gram-negative bacteria and animal cells share this feature. us, (C)
is the correct answer.

Question 92

Which of the following does NOT contain tubulin?
A. Cilia
B. Flagella
C. Microfilaments
D. Centrioles

Answer 92

C
Tubulin is the primary protein in microtubules, which are responsible for the
structure and movement of cilia and flagella, eliminating (A) and (B). Centrioles
organize microtubules into the mitotic spindle, eliminating (D). Microfilaments are
not composed of tubulin, but rather actin, making (C) the correct answer

Question 93

Herpes simplex virus (HSV) enters the human body and remains dormant in the nervous system until it produces an outbreak after exposure to heat, radiation, or other stimuli. Which of the following statements correctly describes HSV?

A. While it remains dormant in the nervous system, the virus is in its lytic cycle.
B. During an outbreak, the virus is in the lysogenic cycle.
C. Herpes simplex virus adds its genetic information to the genetic
information of the cell.
D. The herpes simplex virus contains a tail sheath and tail fibers.

Answer 93

C
Viruses can exist in either the lytic or lysogenic cycle; they may even switch between them. During the lytic cycle, the virus’s DNA takes control of the host cell’s genetic machinery, manufacturing numerous progeny. In the end, the host cell bursts (lyses)
and releases new virions, each capable of infecting other cells. In the lysogenic cycle, viral DNA is added to the host cell’s genome, where it can remain dormant for days or
years.
Either spontaneously or as a result of environmental circumstances, the
provirus can reactivate and enter a lytic cycle. thus, (A) and (B) are incorrect because the terms are reversed. (D) describes features of bacteriophages, which are viruses
that infect bacteria—not the human nervous system. (C) accurately describes how HSV operates during the lysogenic cycle, making it the correct answer.

Question 94

Resistance to antibiotics is a well-recognized medical problem. Which
mechanisms can account for a bacterium’s ability to increase its genetic
variability and thus adapt itself to resist different antibiotics?
I. Binary fission
II. Conjugation
III. Transduction
A. I and II only
B. I and III only
C. II and III only
D. I, II, and III

Answer 94

C
Bacterial cells reproduce by binary fission, an asexual process in which the progeny is
identical to the parent. erefore, binary fission (Statement I) does not increase genetic variability. Conjugation can be described as sexual mating in bacteria; it is the
transfer of genetic material between two bacteria that are temporarily joined.
Transduction occurs when fragments of the bacterial chromosome accidentally become packaged into viral progeny produced during a viral infection and are introduced into another bacterium by the viral vector. Therefore, both conjugation
and transduction (Statements II and III) increase bacterial genetic variability.

Question 95

A bacterial cell is noted to be resistant to penicillin. The bacterium is transferred to a colony that lacks the fertility factor, and the rest of the colony does not become resistant to penicillin. However, the penicillin-resistant cell has also started to exhibit other phenotypic characteristics, including
secretion of a novel protein. Which of the following methods of bacterial
recombination is NOT likely to account for this change?
A. Conjugation
B. Transformation
C. Transduction
D. Infection with a bacteriophage

Answer 95

A
A bacterial cell that does not rapidly cause a phenotypic change in the rest of the colony is likely not F +, meaning that this cell is not able to form a sex pilus for conjugation, making (A) correct.
The expression of new phenotypic characteristics indicates that this bacterium may have acquired genetic material from the
environment through transformation, (B), or transduction (which occurs via
bacteriophage infection), (C) and (D).

Question 96

In Alzheimer’s disease, a protein called the amyloid precursor protein (APP) is cleaved to form a protein called β-amyloid. This protein has a β-pleated sheet structure and precipitates to form plaques in the brain. This mechanism
of disease is most similar to which of the following pathogens?
A. Bacteria
B. Viruses
C. Prions
D. Viroids

Answer 96

C
Prions are infectious proteins that cause misfolding of other proteins. Prions generally cause a shift toward β-pleated sheet conformations, causing decreased solubility and
increased resistance to degradation. this ultimately leads to disease. this mechanism is very similar to the one described here for Alzheimer’s disease, making (C) the
correct answer.

Question 97

After infection of a cell, a viral particle must transport itself to the nucleus in order to produce viral proteins. What is the likely genomic content of the
virus?
A. Double-stranded DNA
B. Double-stranded RNA
C. Positive-sense RNA
D. Negative-sense RNA

Answer 97

A
A virus that requires transport to the nucleus in order to produce viral proteins likely
requires use of nuclear RNA polymerase in order to create mRNA that can be
translated to protein. erefore, only DNA viruses need to be transported to the
nucleus to produce viral proteins, eliminating all answer choices but (A)

Question 98

Which of the following events does NOT play a role in the life cycle of a typical retrovirus?

A. Viral DNA is injected into the host cell.
B. Viral DNA is integrated into the host genome.
C. The gene for reverse transcriptase is transcribed and the mR A is translated inside the host cell.
D. Viral DNA incorporated into the host genome may be replicated along with the host D A.

Answer 98

A is correct. Retroviruses inject viral RNA into host cells. This RNA is then reverse transcribed into DNA. In DNA form, it can then be integrated into the host genome, and replicated along with host DNA, especially in the lysogenic life cycle. Once the virus is in the host, the reverse transcriptase gene is transcribed, and the enzyme can then convert viral RNA into DNA. The DNA can then be transcribed by the cell, and the resulting mRNA is translated by the host’s ribosomes.

Question 99

If two species are members of the same order, they must also be members of the same:

A habitat.
B. family.
C. class.
D. biome

Answer 99

C is correct. Domains are far larger than orders, so if two species are in the same order, they must be in the same domain. A single class encompasses several orders; two different families can belong to the same order. A common mnemonic for taxonomic ranks is Kings Play Cards On Fridays Generally Speaking (Kingdom, Phylum, Class, Order, Family, Genus, Species), going from most encompassing to least. Two species in the same order could very well live in different habitats or biomes, as genetic relatedness does not restrict location.

Question 100

Most viruses that infect animals:

A. enter the host cell via endocytosis.
B. do not require a receptor protein to recognize the host cell.
C. leave their capsid outside the host cell.
D. can reproduce independently of a host cell

Answer 100

A is correct. Most animal viruses enter host cells via receptor-mediated endocytosis. Thus, a receptor is required to recognize the specific appropriate host cell. Unlike bacteriophages, animal viruses do not leave capsids outside host cells. Finally, no virus can reproduce independently, as a defining characteristic of viruses is reproduction within a host cell.

Question 101

Which of the following structures is (are) found in prokaryotes?
I. A cell wall containing peptidoglycan.
II. A plasma membrane lacking cholesterol
III. Ribosomes
A. I only
B. II only
C. I and II only
D. I,II,andIII

Answer 101

D is correct. Eubacteria have cell walls containing peptidoglycan. Bacterial cell membranes do not contain cholesterol. Finally, ribosomes are present in all cells, eukaryotic or prokaryotic.

Question 102

Prior to infecting a bacterium, a bacteriophage must:
A. reproduce, making copies of the phage chromosome.
B. integrate its genome into the bacterial chromosome.
C. penetrate the bacterial cell wall completely.
D. attach to a receptor on the bacterial cell membrane

Answer 102

D is correct. Bacteriophages can only infect those bacteria who have the specific receptor that the virus can attach to and use to enter the cell body. Viruses do not reproduce until they enter a cell. Integration of the viral genome also does not occur until after infection. Finally, bacterial cell wall penetration is the first step of infection, right after attachment to the receptor. As the question asks what occurs before infection, it is presumably also asking for the step that occurs first, and that is receptor attachment.

Question 103

DNA from phage resistant bacteria is extracted and placed on agar with phage-sensitive E. coli. After incubation it is determined that these E. coli are now also resistant to phage attack. The most likely mechanism for their acquisition of resistance is:

A) transduction.
B) sexual reproduction.
C) transformation.
D) conjugation.

Answer 103

C is correct.
Transformation is the process of picking up stray DNA from the environment and incorporating it. As the DNA is already on the agar, the originally sensitive bacteria most likely underwent transformation and incorporated the resistance genes. Transduction is transfer of genes via a viral vector, and while that could potentially occur here, transformation would definitely have to occur first. Sexual reproduction and conjugation involve transfer and swapping of genes between multiple bacteria, and the resistance genes are on the extracted DNA in the environment, not a bacterium that could conjugate or do sexual reproduction.

Question 104

Which of the following would least likely disrupt the Hardy- Weinberg equilibrium?

A. Emigration of part of a population
B. A predator that selectively targets the old and sick
C. A massive flood killing 15% of a large homogeneous population
D. Exposure of the entire population to intense radiation

Answer 104

C is correct.
Catastrophic events will not cause significant genetic drift to a large, homogeneous (well-mixed) population. These kinds of events only significantly disrupt small and/or nonhomogeneous populations. Emigration, selection, and mutation all affect the HW equilibrium, regardless of population size.

Question 105

Penicillin interferes with peptidoglycan formation. Penicillin most likely inhibits bacterial growth by disrupting the production of:

A bacterial plasma membranes.
B prokaryotic cell walls.
C the bacterial nucleus.
D bacterial ribosomes.

Answer 105

B is correct. The bacterial cell wall would be most aHected, as peptidoglycan is a key component of bacterial cell walls. It is not a significant part of any of the other structures listed.

Question 106

All of the following are composed of microtubules EXCEPT:
A) the tail of a sperm cell.
B) the spind le appa rat us.
C) the cilia of the fallopian tubes.
D) the flagella of bacteria.

Answer 106

D is correct. The flagella of bacteria are made from the protein flagellin. Microtubules are a main building block of the other three organelles.

Question 107

Which of the following is true concerning the nucleolus?
A) It is bound by a phospholipid membrane.
B) It disappears during prophase.
C) lt is the site of translation of ribosomal RNA.
D) It is found in most bacteria.

Answer 107

B is correct. The nucleolus disappearing is one of the defining events of prophase. The nucleolus is the site of rRNA transcription, not translation. It is not membrane bound and is not to be confused with the nucleoid of prokaryotes.

Question 108

In some specialized cells, glucose is transported against its concentration gradient via an integral protein using the energy of the sodium ion electrochemical gradient. If no ATP is used for this transport, it is most likely:
A) active transport.
B) facilitated transport.
C) passive transport.
D) osmosis.

Answer 108

A is correct.
Anytime a compound moves against its electrochemical gradient across a membrane, it is active transport. The sodium electrochemical gradient was established by the expenditure of ATP, making this secondary active transport. Facilitated and passive transport both go down the concentration gradient. Osmosis does as well, and is restricted to water

Question 109

Which of the following cells would be expected to contain the most smooth endoplasmic reticulum?
A) A liver cell
B) An islet cell from the pancreas
C) A mature sperm
0 D) A zygote

Answer 109

A is correct. The smoothER plays a major role in detoxification, and the liver detoxifies the body, so it is most likely a liver cell. The other options do not have a significant role that would suggest more than normal smoothER.

Question 110

Which of the following is not a membrane bound organelle?
0A) The golgi body
0 B) The nucleus
0 C) The smooth endoplasmic reticulum 0 D) The ribosome

Answer 110

D is correct.
Ribosomes are made of RNA and protein. They do not have a phospholipid bilayer.

Question 111

One function of the Iiver is to detoxify alcohol taken into the body. The organelle withi n the liver cell that most directly affects this process is:

0 A) the smooth endoplasmic reticulum. 0 B) the nucleus.
0 C) the Golgi apparatus.
0 D) the rough endoplasmic reticulum.

Answer 111

A is correct.
The smooth endoplasmic reticulum helps to detoxify alcohol in the liver. The nucleus runs the cell and makes nucleic acids; the Golgi body packages materials for transport. The rough endoplasmic reticulum makes proteins for use outside the cell.

Question 112

When a become primary lysosome fuses with a food vesicle to a secondary lysosome:

A) its pH drops via active pumping ofprotons into its interior.
B) its pH drops via active pumping of protons out of its interior.
C) its pH rises via active pumping of protons into its interior.
0 D) its pH rises via active pumping of protons out of its interior.

Answer 112

A is correct. The hydrolytic enzymes of lysosomes are activated by a low pH achieved by pumping protons into the interior. Choices Band C can be ruled out immediately, as the pH change described is the opposite of what actually occurs based on the proton movement. Finally, the enzymes in lysosomes require a low pH to be active, so choice D is unlikely.

Question 113

Which of the following cells would be expected to have a well-developed rough endoplasmic reticulum?
0 A) Pancreatic cells
0 B) Adipocytes
0 C) Muscle cells
0 D) Neurons

Answer 113

A is correct. Peptide hormones are synthesized in the rough ER. Insulin and glucagon are two major peptide hormones synthesized in the pancreas, so a pancreatic cell is most likely. The other cell types do not perform any major functions that would require more than normal amounts of rough ER.

Question 114

The sodium-potassium ATPase hydrolyzes ATP to pump three sodium outside ofthe cell and two potassium into the cell. Which of the following is true about the sodium- potassium ATPase?
I. It is an example of secondary active transport.
II. Sodium is pumped against its concentration gradient
III. Potassium is pumped agaisnst its concentration gradient
A. I Only
B. II only
C. II and III only
D. I, II, and III

Answer 114

C is correct. The sodium-potassium pump transports both ions against their concentration gradient. If they were moving along the gradient, a pump, and energy input, would not be necessary. The sodium-potassium pump is also a form of primary active transport. Energy is used to pump ions against their gradients.

Question 115

Intestinal epithelium uses the diffusion of sodium down its concentration gradient to power the translocation of glucose inside of a cell. This is an example of:
0 A) primary active transport.
0 B) secondary active transport.
0 C) passive diffusion.
0 D) facilitated diffusion.

Answer 115

B is correct. In secondary active transport, one molecule diffuses down its gradient, and this favorable change is paired with the unfavorable movement of another molecule against its gradient. This is happening here with sodium and glucose. Primary active transport uses energy, usually ATP, to pump something against its gradient. Passive and facilitated diffusion both involve molecules only going down their gradient.

Question 116

Which of the following is least likely to require a protein to be transported into a cell?
0 A) Protein
0 B) Glucose
0 C) Amino acids
0 D) Carbon dioxide

Answer 116

19. D is correct. The main characteristics that need to be considered here are size and polarity. Carbon dioxide is a small molecule, and is nonpolar and hydrophobic. Thus, it can go straight through the hydrophobic cell membrane. All other molecules are polar, and larger, and would most likely require some sort of transporter to enter a cell.
    A is correct. Protein hormones bind to structures on the plasma membrane, as proteins are often large and hydrophilic, so they cannot go through the membrane easily. The only option within the cell is binding to a nuclear receptor. Typically, only steroid hormones will bind to a nuclear receptor. All other options are located on the cell membrane, and protein hormones are likely to use them.

Question 117

A protein hormone is least likely to act by which of the following mechanisms?

A) Binding to a receptor in the nucleus
B. Opening a membrane bound channel
C. Activating a membrane bound enzyme D. Activating a G protein

Answer 117

B is correct. I and II are true, but desmosomes are anchored to the cytoskeleton and are stronger than tight junctions.

Question 118

Which of the following statements is (are) true concerning tight junctions?
I. They connect adjacent cells.
II. They may form a barrier to extracellular fluids.
III. They have the greatest strength of all cellular adhesions.

A. I Only
B. II only
C. II and III only
D. I, II, and III

Answer 118

Cis correct. The red blood cells would burst. The osmolarity in the cells is much higher than the pure water, with no solutes. Thus, water would continuously flow into the cells until they burst. Cells stay the same size in an isotonic solution. They would expand in a slightly hypotonic solution, but not in a solution as hypotonic as pure water. Finally, shrinking occurs in a hypertonic solution, which is not the case for pure water.

Question 119

What would be the likely consequence of adding pure water to a petri dish of human red blood cells?

A) the blood cells stay same size
B) the cells would expand
C) the cells will burst
D) the cells will shrink

Answer 119

A is correct. Adult neurons are not preparing for, or in the process of cell division. Cells in the G phase cease to divide, describing these neurons perfectly. All other phases listed are preparing for cell division, producing DNA, organelles, and other components necessary for mitosis.

Question 120

A neuron in an adult human is in which stage of the cell cycle?
A. G0
B. G1
C. S
D. G2

Answer 120

B is correct. Desmosomes are used purely for cell-to-cell adhesion, and not so much for communication. Gap junctions allow molecules and ions to flow freely between the two cells, and are used for communication. Membrane and nuclear receptors also bind signaling molecules in cell-to-cell communication.

Question 121

Which of the following is not involved in cell-to-cell communication?
A) Gap junctions
B) Desmosomes
C) Membrane receptors
D) Nuclear receptors

Answer 121

B is correct. Desmosomes are used purely for cell-to-cell adhesion, and not so much for communication. Gap junctions allow molecules and ions to flow freely between the two cells, and are used for communication. Membrane and nuclear receptors also bind signaling molecules in cell-to-cell communication.

Question 122

In the Vesicular Transport Model, the cis-, medial-, and trans-Golgi cisternae are […] structures

Anki

Answer 122

In the Vesicular Transport Model, the cis-, medial-, and trans-Golgi cisternae are static structures

The contents are physically shuttled from each cisterna to the next

Question 123

[…] are plasmids that integrate into the genome

Anki

Answer 123

Episomes are plasmids that integrate into the genome

Example:
Viruses
F factor
insertion sequences and transposons

Question 124

[type of microorganism] require O2

anki

Answer 124

Obligate aerobes require O2

Question 125

[…] genomes may be made of DNA or RNA and may be single or double stranded

Answer 125

Viral genomes may be made of DNA or RNA and may be single or double stranded

Question 126

Microfilaments make up part of the cell’s […]

Answer 126

Microfilaments make up part of the cell’s cytoskeleton

Question 127

[type of microorganism] do not use O2 but tolerate it

Answer 127

Aerotolerant anaerobes do not use O2 but tolerate it

Question 128

[…] is a small prokaryotic DNA molecule separate from chromosomal DNA

Answer 128

plasmid is a small prokaryotic DNA molecule separate from chromosomal DNA

Often, the genes carried in plasmids provide bacteria with genetic advantages, such as antibiotic resistance

Question 129

The [smooth or rough] ER makes proteins from mRNA

Answer 129

The rough ER makes proteins from mRNA

Question 130

[…] is the transfer genetic material using a bacteriophage

Answer 130

Transduction is the transfer genetic material using a bacteriophage

Question 131

[…] are individual virus particles that are found extracellular

Answer 131

Virions are individual virus particles that are found extracellular

Question 132

Centrioles contain 9 groups of […] and they pull […] apart

Answer 132

Centrioles contain 9 groups of microtubules and they pull chromosomes apart

Question 133

[type of microorganism] toggle between aerobic and anaerobic

Answer 133

Facultative anaerobes toggle between aerobic and anaerobic

Question 134

Gram + is [color] and has a [thick or thin] wall

Answer 134

Gram + is purple and has a thick wall

Wall is made of peptidoglycan/lipoteichoic acid

Question 135

[…] are infectious proteins and can trigger misfolding

Answer 135

Prions are infectious proteins and can trigger misfolding

Causes Creutzfeldt-Jakob Disease

Question 136

Gram - is [color] and has a [thick or thin] wall

Answer 136

gram - is pink / red and has a thin wall

Wall is made of peptidoglycan

Question 137

[…] are DNA sequences that can change their position within a genome

Answer 137

Transposons are DNA sequences that can change their position within a genome

This sometimes creates or reverses mutations

Question 138

The [organelle] modifies and distributes proteins

Answer 138

The Golgi Apparatus modifies and distributes proteins

Eukaryotes only

Question 139

Peroxisomes […] material

Answer 139

Peroxisomes break down material

Question 140

[…] are plant pathogens

Answer 140

Viroids are plant pathogens

Question 141

In a/an […] bacteriophage life cycle, the virus DNA is embedded into the host DNA

Answer 141

In a/an lysogenic bacteriophage life cycle, the virus DNA is embedded into the host DNA

Question 142

The nucleolus makes […]

Answer 142

The nucleolus makes ribosomes

Question 143

Conjugation is the transfer genetic info via a/an […]

Answer 143

Conjugation is the transfer genetic info via a/an conjugation bridge

Sex pilus stuff

Question 144

Unlike microfilaments and microtubules, intermediate filaments such as keratin and desmin do not participate in […]

Answer 144

Unlike microfilaments and microtubules, intermediate filaments such as keratin and desmin do not participate in cell motility

Question 145

The nucleoid region is found in [eukaryotes or prokaryotes] and contains […]

Answer 145

The nucleoid region is found in prokaryotes and contains DNA

Question 146

Retroviruses are single stranded […]

Answer 146

Retroviruses are single stranded RNA

Reverse transcriptase is needed to make DNA

Question 147

[…] are the demolition and recycling center

Answer 147

Lysomes are the demolition and recycling center

Question 148

Microtubules help the cell […] compression forces

Answer 148

Microtubules help the cell resist compression forces

Made of tubulin proteins

Question 149

In a […] bacteriophage life cycle, virions are made until the cell lyses

Answer 149

In a lytic bacteriophage life cycle, virions are made until the cell lyses

Viruses enter cells and use the cell to make copies of themselves, often destroying the cell in the process

Question 150

A/an […] is the protein shell of a virus

Answer 150

A/an capsid is the protein shell of a virus

Question 150

The [smooth or rough] ER is involved in detox and also in lipid formation

Answer 150

The smooth ER is involved in detox and also in lipid formation

Question 151

In the Cisternal Maturation Model, cisternae […]

Answer 151

In the Cisternal Maturation Model, cisternae evolve and mature

The cis-Golgi matures and becomes the medial-Golgi, then eventually, the trans-Golgi

Vesicles move in retrograde motion

Question 152

[type of microorganism] die in O2

Answer 152

Obligate anaerobes die in O2

Question 153

Prokaryotic cells reproduce via […]

Answer 153

Prokaryotic cells reproduce via binary fission

Question 154

[…] is when bacteria gets genetic info from the environment

Answer 154

Transformation is when bacteria gets genetic info from the environment

Griffith experiment with mice (R strain safe, S strain deadly)

Question 154

[…] are bacteria viruses that use a tail sheath to inject DNA / RNA

Answer 154

Bacteriophages are bacteria viruses that use a tail sheath to inject DNA / RNA