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The Cell Flashcards

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1
Q

What are the 3 basic tenets of the cell theory?

A
  • All living things are composed of cells
  • The cell is the basic functional unit of life
  • Cells arise only from preexisting cells
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2
Q

What is Robert Hooke most known for?

A

In 1665, he assembled a compound microscope.

He then observed a cork and its non living cells

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3
Q

Who and when was the first to view a living cells under a microscope?

A

In 1674, Anton van Leeuwenhoek

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4
Q

What was the scientific contribution of Rudolph Virchow?

A

In 1850, demonstrated that diseased cells could arise out of normal cells

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5
Q

What is the fourth tenet of the cell theory, added due to advances in molecular biology?

A

Cells carry genetic information, in the form of DNA, which is passed on from parent to daughter cell

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6
Q

Why are viruses not considered living organisms?

A

Viruses are unable to reproduce on their own, this violates the third and fourth tenets and cell theory

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7
Q

What is the major distinction of nuclei between prokaryotic and eukaryotic cells?

A

Eukaryotic cells- contains a nucleus enclosed by a membrane

Prokaryotic cells- do not contain a nucleus

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8
Q

Each cell has a membrane enclosing a semifluid______________in which organelles are suspended

A

Cytosol

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9
Q

How eukaryotic cells reproduce?

A

By mitosis

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10
Q

What is the function of cytosol?

A

Allows for diffusion of molecules throughout the cell

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11
Q

Describe the phospholipid belayer

A

The surfaces are hydrophilic

  • hydrophobic in its inner portion which provides a selective barrier
  • electrostatically interacting with the aqueous environment
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12
Q

Describe the surrounding of the nucleus

A
  • Nucleus is surrounded by nuclear envelope/membrane (a double membrane that maintains a nuclear environment, distinct from the cytoplasm)
  • Nuclear pores in the nuclear envelope allow for selective two-way exchange of material between cytoplasm and nucleus
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13
Q

What is the function of nuclear envelope?

A

Creates two distinct environments within the cell because it separates nucleus from cytoplasm

This allows for compartmentalizations of transcription and translation

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14
Q

What are histones?

A

Organizing proteins which linear DNA is wound around

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15
Q

Where is the rRNA(ribosomal RNA) synthesized?

A

In the nucleolus (a subsection of the RNA)

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16
Q

Wha s the function of the outer membrane of the mitochondria?

A

Serves as a barrier between the cytosol and the inner environment of the mitochondria

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17
Q

What is the function of the inner membrane of the mitochondria?

A

Thrown into numerous folding called Cristae, contains the molecules and enzymes needed by the electron transport chain

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18
Q

What is the mitochondrial intermembrane space ?

A

The space between the mitochondrial membranes

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19
Q

What is the mitochondrial matrix?

A

The space inside the inner membrane

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20
Q

What is the serial endosymbiosis theory?

A

Explains the formation of some membrane-bound organelles

States that these organelles formed by one prokaryote engulfing the other and forms a symbiotic relationship between the two

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21
Q

Why is the mitochondria considered semi-autonomous?

A

Has some of their own genes, and replicate independently of the nucleus via binary fission

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22
Q

What is cytoplasmic/extranuclear inheritance? Give an example

A

Example-mitochondria

Inheritance independent of the nucleus

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23
Q

What is the role of the mitochondria in apoptosis /programmed cell death?

A

Releases enzymes from the electron transport chain and kick-starts apoptosis

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24
Q

What is autolysis?

A

When lysosomes release enzymes it is autolysis

Like the mitochondria, it causes apoptosis

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25
Q

What is the endoplasmic reticulum?

A

A series of interconnected membrane that are actually contiguous with the nuclear envelope

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26
Q

What is the rough ER( rER)?

A

Is studded the ribosomes which permit the translation of proteins destined for secretion directly into its lumen

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27
Q

What is the smooth endoplasmic reticulum(SER)?

A

Lacks ribosomes and is utilized primarily for lipid synthesis(such as for phospholipid bilayer) and the detoxification of certain drugs and poisons.

Also transports proteins from the RER to the Golgi apparatus

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28
Q

What are the functions of the Golgi apparatus?

A

Materials from the ER are transferred to the Golgi apparatus in vesicles which may be modified by various groups

Golgi apparatus may modify cellular products, then repackage products in vesicles and transferred to the correct cellular location

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29
Q

What are peroxisomes?

A

Contain hydrogen peroxide

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30
Q

What is the primary function of peroxisomes?

A

The breakdown of very long chain fatty acids via B-oxidation

Peroxisomes participate in the synthesis phospholipids and contain some of the enzymes involved in pentode phosphate pathway

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31
Q

What are the 3 components of the cytoskeleton?

A
  1. Microfilaments
  2. Microtubules
  3. Intermediate filaments
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32
Q

What are the functions of the cytoskeleton?

A

Provides structure to the cell and and helps it to maintain shape

Provides a conduit for the transport of materials around the cell

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33
Q

Describe microfilaments

A

Made up solid polymerized rods of actin.

Actin filaments are organized into bundles and networks and are resistant to both compression and fracture providing protection for the cell

Actin filaments can also use ATP to generate force for movement by interacting with myosin, such as in muscle contraction

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34
Q

What is cytokinesis?

A

The division of materials between daughter cells

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35
Q

What is the role of microfilaments in in cytokinesis?

A

During mitosis, the cleavage furrow is formed by microfilaments which organize as a ring at the site of division between the two daughter cells

Actin filaments within this ring contract, the ring becomes smaller, eventually pinching off the connection between the two daughter cells

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36
Q

What are cilia?

A

Projections from a cell primarily involved in movement of materials along the surface of the cell

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37
Q

What are microtubules?

A

Hollow polymers of tubules proteins

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38
Q

What are the functions of microtubules?

A

Provide primary pathways along which the motor proteins like kinds in and dyenein

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39
Q

Describe the structure of cilia and flagella

A

Both have the same structure, composed of nine pairs of microtubules forming an outer ring with two in the center(9+2 structure)

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40
Q

What are the functions of centrioles?

A

The organizing centers for microtubules and are structured as nine triplets of microtubules with a hollow center

In mitosis, microtubules emanating from the centrioles(which are at opposite sides poles of the cell) attach to chromosomes via kinetochores

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41
Q

Describe intermediate filaments

A

These are a diverse group of filamentous proteins including keratin, desmin, vimentin and Lamins

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42
Q

What are the functions of intermediate filaments?

A
  • involved in cell to cell adhesion
  • maintenance if cytoskeleton integrity
  • make the cell more rigid
  • help anchor other organelles including the nucleus
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43
Q

What are the 4 types of tissue?

A
  1. Epithelial tissue
  2. Connective tissue
  3. Muscle
  4. Nervous tissue
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44
Q

What are the functions of epithelial tissue?

A

Provides protection against pathogens

involved in absorption, secretion and sensation

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45
Q

What is the basement membrane?

A

An underlying connective tissue that keeps epithelial tissue together

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46
Q

In many organs, epithelial cells constitute the parenchyma, what is this?

A

The functional parts of the organ

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47
Q

Epithelial are said to often be polarized, what does this mean?

A

One side faces the lumen of the organ interacting with underlying blood vessels while the other side faces the outside world

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48
Q

How can epithelial be categorized based on the number of layers they have?

A

Simple epithelia

Stratified epithelia

Psuedostratified epithelia

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49
Q

What are simple epithelia?

A

Epithelia with one layer of cells

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50
Q

What are psuedostratified epithelia?

A

Appear in multiple layers due to differences in height but in reality is one layer

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51
Q

What are stratified epithelia?

A

Epithelia with multiple layers

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52
Q

How can epithelia be categorized according to shape?

A

Cuboidal-cube shaped

Columnar- long and thin

Squamous-flat and scalelike

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53
Q

What is the purpose of connective tissue?

A

Provides a framework for epithelial cells to carry out their functions

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54
Q

Differentiate between connective tissue and epithelial tissue

A

Epithelial cells contribute to parenchyma of an pan while connective tissue contribute to the stroma of support structure like bone, cartilage, tendons….

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55
Q

What 2 domains do prokaryotes fall under?

A

Archea and bacteria

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56
Q

Describe organisms that would be categorized as Archea

A

Are single-called organisms that are visually similar to bacteria but contain genes and metabolic pathways that are more similar to eukaryotes than bacteria

They are extremophiles

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57
Q

What similarities imply that Archea and eukaryotes share a common ancestor ?

A

Both eukaryotes and Archea start translation with methionine, contain similar RNA polymerases and associate their DNA with histones.

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58
Q

What are some differences between Archea and eukaryota?

A

Archea contain a single circular chromosome

Archea divide by binary fission

Archea share a similar DNA to bacteria

59
Q

Why are newborns at risk of hemorrhage ?

A

They are not yet colonized by bacteria which produce vitamin K in the intestines and cannot produce clotting factors

60
Q

What is a mutuslistic symbiotic relationship? Give and example

A

Both organisms benefit from a relationship

Humans and bacteria in the gut that produce vitamin K and biotin(vitamin B7)

61
Q

Describe how bacteria can be categorized according to shape?

A

Spherical bacteria- cocci

Rod shaped bacteria- bacilli

Spiral shaped bacteria- spirilli

62
Q

Give an example of a cocci bacteria?

A

Streptoccocus pyogenes

63
Q

Give an example of a bacilli bacteria

A

E. coli

64
Q

Give an 3 examples from spilling bacteria and the diseases caused by each

A
  1. Treponema pallium- causes Syphilis
  2. Borrelia burgdorferi- causes Lyme diseases
  3. Leptospira interrogans- causes Weil’s disease
65
Q

What are obligate aerobes?

A

Bacteria’s which need oxygen to live

66
Q

What are anaerobes?

A

Bacteria which uses fermentation or other form of cellular metabolism other than oxygen

67
Q

What are obligate anaerobes?

A

Bacteria which cannot survive in an oxygen-containing environment

68
Q

Why do obligate anaerobes die in an oxygen containing environment ?

A

Presence of oxygen leads to the production of reactive oxygen-containing radicals in these species killing them

69
Q

What are facultative anaerobes?

A

Bacteria can use oxygen for metabolic processes if presence and switch to anaerobic metabolism if oxygen is absence

70
Q

What are aerotolerant anaerobes?

A

Bacteria unable to use oxygen for metabolism but are not harmed by its presence in the environment

71
Q

Together the celll wall and cell membrane are Calle ….

A

The envelope

72
Q

What are the 2 types of cell walls in bacteria?

A

Gram positive

Gram negative

73
Q

What is the function of the cell wall in bacteria?

A

Cell wall provides structure and controls movement of solutes which allows the cell to maintain concentration gradients relative to the environment

74
Q

Describe the gram staining process

A

Uses a crystal violet stain followed by a counter stain called safranin

75
Q

How is a gram positive bacteria differentiated from and gram negative bacteria

A

Gram positive- absorbs crystal violet stain and appears deep purple

Gram negative- bacterial envelope doesn’t absorb crystal violet stain but absorbs counter stain then cell appears pink-red

76
Q

Describe gram positive cell walls

A

Consists of a thick layer of of peotidoglycan and lipoteichoic acid

77
Q

What is the purpose of lipoteichoic acid in gram positive ?

A

The function of this acid is unknown in bacteria but in the human immune system may be activated upon exposure to these chemicals

78
Q

What is the purpose peptidoglycan in bacterial cell wall?

A

Structural and barrier functions and also aids in pathogens to by providing protection from the host immune system

79
Q

How does the antibiotic penicillin work?

A

Targets the enzyme that catalyzes the cross-linking of peptidoglycan

Gram-positive cells that cannot crosslink no longer serve as a barrier

This makes them vulnerable to osmotic damage and lyses

80
Q

Describe Gram-negative cell walls

A

Are very thin also contain peptidoglycan but in smaller amounts than gram-positive cell walls

Has cell membrane as well as outer membrane containing phospholipids lipopolysaccharides

81
Q

What is the drawback of lipopolysaccharides in gram-negative cell walls?

A

Triggers the immune response in human beings

The inflammatory response to lipopolysaccharides is much stronger than the response to lipoteichoic acid

82
Q

What is peptidoglycan made of?

A

Polymeric substance made from amino acids and sugars

83
Q

What is chemotaxis?

A

The ability of a cell to detect chemical stimuli and move toward or away from them

84
Q

Describe the structure of the flagella

A

Composed of of a filament, basal body and a hook

85
Q

Describe the flagella filament

A

A hollow helical structure composed of flagellin

86
Q

Describe the basal body of the flagella

A

A complex structure that anchors the flagellum to the cytoplasmic membrane and is also the motor of the cytoplasmic membrane

Rotating rates up to 300Hz

87
Q

Describe the hook of the flagella

A

Connects filament and the basal body so the basal body rotates which exerts torque on the filament which then spin and propel the bacterium forward

88
Q

What are plasmids?

A

Circular structures which carry DNA, possibly acquired from external sources

89
Q

What is the function of plasmids?

A

Plasmids carry DNA that is not necessary for survival of the prokaryote so not considered part of the bacterial genome

But may give an advantage such as an antibiotic resistance

90
Q

What is the function of the cell membrane in prokaryotes?

A

Used for the electron transport chain and ATP

91
Q

Contrast ribosomes in prokaryotes and eukaryotes

A

Prokaryotes- contain 30S and 50S

Eukaryotes- contain 40S and 60S

92
Q

Describe binary fission

A

A simple form of of asexual reproduction seen in prokaryotes

The circular chromosome attaches to the cell wall and replicates while the cell continues to grow in size

Eventually the plasma membrane and cell wall begin to grow inward along the mid line of the cell to produce 2 identical daughter cells

93
Q

Which is faster between mitosis and binary fission? Why?

A

Binary fission, it has less steps

94
Q

What are virulence factors?

A

Traits that increase how pathogenic a bacterium is, such as toxin production

These are carried on plasmids

95
Q

What are episomes?

A

A subset of plasmids that are capable of integrating into the genome of the bacteria

96
Q

What are the bacterial recombination processes?

A
  1. Transformation
  2. Conjugation
  3. Transduction
97
Q

What is bacterial transformation?

A

The integration of foreign genetic material into the host genome

This genetic material usually comes from other bacteria that upon lysing, spill their contents in the vicinity of the bacteria

Many gram-negative rods are capable of transformation

98
Q

What is bacterial conjugation?

A

The bacterial form of mating

99
Q

Describe bacterial conjugation

A

Involves 2 cells forming a conjugation bridge between them and transferring genetic material

Transfer is unidirectional, from the male(+) to female(-)

100
Q

How is the conjugate bridge formed in bacterial conjugation?

A

The bridge is made from appendages called sex pili found on the donor male

To form the pilus, the bacteria must contain plasmids known as sex factors that contain the necessary genes

101
Q

What is the best studied sex factor? How are bacteria which posses it differentiated from those that don’t have it?

A

F (fertility) factor of E. Coli

When present in plasmid- F+ cells

When absent in plasmin- F- cells

102
Q

What role does the F(fertility) sex factor play in conjugation?

A

F+ cell replicates a copy of its F factor and donates it to the F- cell making it F+

This enables the cell obtaining the new plasmid to transfer copies to other cells

103
Q

Conjugation allows for rapid acquisition of ____________________________________ throughout a colony because other plasmids can be passed through the conjugation bridge

A

antibiotic acquisition and virulence factors

104
Q

Which genes may be transferred across a conjugation bridge if a sex factor is integrated into its genome?

A

Trick question:The donor cell will attempt to transfer a copy of its entire genome but the bridge usually breaks before the full DNA sequence can be moved

105
Q

What is high frequency of recombination (Hfr)?

A

When an Hfr cell (cell with that has F factor incorporated into the genome) conjugates a recipient cell

Bacterial genes are transferred to the recipient with high frequency

106
Q

What is transduction?

A

The only genetic recombination process that requires a vector- a virus that carries genetic material from one bacterium to another

107
Q

Viruses are obligate intracellular pathogens, what does this mean?

A

They can not reproduce outside of a host cell

108
Q

What are bacteriophages?

A

Viruses that infect bacteria

109
Q

What enables bacteriophages to trap a segment of host DNA during assembly?

A

Viruses cannot reproduce outside of the host cell(they are obligate intracellular pathogens)

110
Q

What happens a bacteriophage infects a bacteria after trapping a segment of DNA of a previously infected bacteria?

A

It can release the trapped bacteria DNA into the new host cell.

This transferred DNA can then integrate into the genome giving the new host additional genes

111
Q

What are transposons ?

A

Genetic elements capable of inserting and removing themselves for the genome

This is in both prokaryotes and eukaryotes

112
Q

What are the 4 phases of bacterial growth in order?

A
  1. Lag phase
  2. Exponential phase
  3. Stationary phase
  4. Death phase
113
Q

Describe the lag phase of bacterial growth

A

When the bacteria adapts to new local conditions f a new environment

114
Q

Describe the exponential/log phase of bacterial growth

A

Growth increases as bacteria adapt

115
Q

Describe the stationary phase of bacterial growth

A

The reduction of resources causes a slowing of reproduction

116
Q

Describe the death phase of bacterial growth

A

As resources of the environment becomes deleted, the death phase ensues

117
Q

The bacterial growth curve is an example of….

A

A semi log plot

118
Q

What is the capsid?

A

The protein coat of the virus

119
Q

What is the function of the viral envelope? Why?

A

The envelope is sensitive to hear, detergents, desiccation.

This makes the virus easier to kill(those that have)

120
Q

What is the viral envelope?

A

If present, will consist of phospholipids and virus specific proteins surrounding the capsid

121
Q

Aside from being sensitive, what is another benefit a virus gains by having no envelope?

A

Viruses with no envelope are more resistant to sterilization and more likely to persist on surfaces

122
Q

Why do viruses require host cells to replicate?

A

They lack ribosomes to carry out protein synthesis

123
Q

What are virions?

A

Viral progeny produced when a virus hijacks a cell’s machinery

124
Q

How do bacteriophages infect bacteria?

A

Bacteriophages inject their genetic material leaving the remaining structures outside the remaining cell

125
Q

What is the function of tail fibers of bacteriophages?

A

Help the bacteria recognize and connect to the host cell

126
Q

What are the 2 types of viral single stranded RNA?

A

Positive and negative sense

127
Q

What is a positive sense single stranded viral RNA ?

A

Implies the genome may be directly translated to functional proteins by the ribosomes of the host cell like mRNA

128
Q

What is negative sense single stranded viral RNA?

A

These require the synthesis of an RNA strand that is complementary to the negative sense RNA strand.

This new strand will then be used as a template for protein synthesis

129
Q

Negative sense RNA viruses may carry an___________ _________ in the virgin to ensure the complementary strand is synthesized

A

RNA replicase

130
Q

What are retroviruses ?

A

Are enveloped, single-stranded RNA viruses in the family Retroviridae, the vision contains two identical RNA molecules

These viruses carry reverse transcriptase which synthesizes DNA from RNA

131
Q

How do retroviruses infect host cells?

A

Uses reverse transcriptase to synthesize DNA from single stranded RNA

The DNA then integrates into the host cell genome where it is replicated and transcribed as the host cell’s own DNA

This allows for the host cell to be infected indefinitely and can only be cured by killing the host cell

132
Q

HIV is a _____________

A

Retrovirus

133
Q

Describe the life cycle of HIV

A
  1. Viral envelope must bind to CD4 and CCR5 on the cell surface
  2. As the virus fuses with the cell, it empties its contents into the cytoplasm
  3. A viral enzyme, reverse transcriptase, then copies the virus’s RNA genome into double stranded DNA
  4. Integrase inserts the copy into the host DNA
  5. Cell machinery transcribes the viral genes back into RNA (including RNA that can serve as templates for proteins) that travels to the cytoplasm, where ribosomes produce encoded proteins
  6. Viral RNA and proteins then move toward the cell membrane, where they gather into a budding virus particle
  7. In the immature new virus copy, the HIV protease enzyme modifies viral protein chains, enabling the particles or virions, to mature into a form that is ready to infect a new cell
134
Q

Without the proper receptors, a cell is _____________ to a virus

A

Invisible

135
Q

People with no CCR5 are…

A

Immmune to HIV

136
Q

Give the various ways viral progeny may be released

A
  1. Viral infection may initiate cell death, causing spilling of viral progeny
  2. The host cell may lyse as a result of being filled with extremely large numbers of virions
  3. Virus can leave the cell by fusing with its plasma membrane by a process called extrusion
137
Q

Why is lysis of a host cell disadvantageous for the virus?

A

The virus can no longer carry out its life cycle

138
Q

What is the function of extrusion in a viral life cycle ?

A

Allows for survival of the host cell and use of the host cell by the virus

A virus in this state is said to be in a productive cycle

139
Q

What types of life cycles may a bacteriophage enter?

A

Lyric or lysogenic life cycle

140
Q

Describe a lyric cycle of a bacteriophage

A

The bacteriophage makes maximal use of the cell’s machinery with little regard for the survival of the host cell.

Once the host is swollen with new virions, the cell lyases and other bacteria can be infected. Bacteria in the lytic phase are termed virulent

141
Q

Bacteria in the lytic phase are termed…

A

Virulent

142
Q

Describe the lysogenic cycle

A

Bacterium dies not lyse but virus integrates into the host genome as a provirus or prophage

The virus will be replicated as the bacterium reproduces

Virus genome may remain integrated indefinitely but environmental factors (radiation, light, chemicals) will cause provirus to leave the genome and revert to a lytic cell

143
Q

How does the bacterium benefit from a lysogenic virus?

A

Infection with one strain of phage generally makes bacterium less susceptible to superinfection (simultaneous infection) with other phases

Because the virus in innocuous there may be some evolutionary advantage

MCAT- Biology (2 decks)

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