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The cell Flashcards

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1
Q

The human body contains approximately how many ce;;s?

A

37 trillion

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2
Q

How are organs formed?

A

Through tissues created from cells.

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3
Q

What outnumbers the other in the human body? bacteria or eukaryotic cells? and by how many?

A

bacteria. 10 to 1.

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4
Q

Why were organisms perceived as being complete and inseparable into smaller parts prior to the 1600s?

A

due to the inability to see smaller structures through optical instrument like the microscope.

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5
Q

Who first examined cells using a compound microscope in 1665?

A

Robert Hooke

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6
Q

Why did Robert Hooke not see organelles like nuclei when testing the CM in 1665?

A

He tested the CM using a cork which is a non living thing.

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7
Q

Who was the first to view a living cell under the CM and in what year?

A

Anton van Leuwenhoek. 1674

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8
Q

The function of tissues is dependent on

A

the function of the cells it is made up of.

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9
Q

In 1850, who demonstrated that diseased cells could arise from normal cells in normal tissues?

A

Rudolph Virchow.

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10
Q

What are the three basic tenets of cell theory?

A
  • All living things are composed of cells.
  • The cell is the basic functional unit of life.
  • Cells arise only from pre-existing cells
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11
Q

What is the fourth tenet that was added to cell theory after advances in molecular biology?

A
  • Cells carry genetic information in the form of dna, which is passed from parent to daughter cell.
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12
Q

These small structures contain genetic material but are unable to reproduce on their own.

A

Viruses

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13
Q

Viruses through their nature violate which tenets of cell theory?

A

the third and fourth.

  • Cells arise only from pre-existing cells.
  • Cells contain genetic material (DNA) that is passed from parent to daughter cell.
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14
Q

Why are viruses said to violate the third and fourth basic tenets of cell theory?

A

Because virions can only replicate by invading other organisms, and some contain RNA as their genetic material instead of DNA.

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15
Q

List the 4 fundamental tenets of cell theory.

A
  • All living things are composed of cells.
  • Cells are the basic functional unit of life.
  • Cells only arise from pre-existing cells.
  • Cells contain genetic info called dna that is passed from parent to daughter cells.
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16
Q

What is the first major distinction that can be made between living organisms?

A

whether they are composed of prokaryotic or eukaryotic cells.

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17
Q

What is the difference between eukaryotic and prokaryotic cells?

A

eukaryotic cells contain a true nucleus enclosed in a membrane whereas prokaryotic cells do not contain a nucleus.

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18
Q

in what are the organelles suspended in a cell?

A

in a semifluid cytosol enclosed by the cell membrane.

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19
Q

What allows for compartmentalization of functions in organelles in eukaryotic cells?

A

Most organelles are membrane bound.

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20
Q

Why are eukaryotic cells’ membrane unique?

A

Their membrane consist of a phospholipid bilayer making their surface hydrophilic, electrostatically interacting with the aqueous environments inside and outside the cell, while the inner portion is hydrophobic which helps provide a highly selective barrier between the interior of the cell and the outside environment.

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21
Q

what part of the cell is hydrophilic and what part if hydrophobic?

A

The cell membrane is hydrophilic while the interior of the cell is hydrophobic.

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22
Q

What is the function of the cytosol/cytoplasm in the EC?

A

Permits diffusion of molecules throughout the cell

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23
Q

genetic material (deoxyribonucleic acid) is encoded in what part of the cell?

A

the nucleus

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24
Q

genetic material in the nucleus is is organized into

A

chromosomes.

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25
Q

Through what mechanism do EC reproduce?

A

through mitosis, allowing for the formation of two identical daughter cells.

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26
Q

What is the control center of the cell?

A

nucleus

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27
Q

This organelle of the cell contains all the genetic material required for cell replication?

A

the nucleus.

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28
Q

what surround the nucleus?

A

nuclear membrane/envelope

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29
Q

describe the nuclear membrane/envelope of the nucleus.

A

double membrane that maintains the nuclear environment separate and distinct from the cytoplasm.

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30
Q

what does the nuclear membrane of the nucleus contain that allows selective two-way exchange of material of material between the nucleus and the cytoplasm?

A

nuclear pores

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31
Q

the nuclear envelope of the nucleus contains nuclear pores that permit

A

a selective two-way exchange of material in and out of the nucleus.

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32
Q

Dna contains coding regions called

A

genes

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33
Q

Linear dna is wound around organizing proteins called

A

histones

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34
Q

Linear dna is further wound into linear strands called

A

chromosomes

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35
Q

what permits the compartmentalization of dna transcription separate from rna translation?

A

the location of dna within the nucleus.

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36
Q

The subsection of the nucleus in which ran is synthesized is called

A

the nucleolus

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37
Q

how much of the nucleus does the nucleolus take up?

A

About 25% of the nucleus’s entire volume.

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38
Q

This organelle is often referred to as the power plant/house of the cell.

A

the mitochondria

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39
Q

how many membranes does the mitochondria have?

A

two. outer and inner

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40
Q

What is the purpose of the mitochondria’s outer membrane?

A

it serves as a barrier between the cytosol and the inner environment of the mitochondria

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41
Q

the inner membrane of the mitochondria has numerous infolding called

A

cristae

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42
Q

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

A

it contains molecules and enzymes necessary for electron transport chain.

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43
Q

This highly convoluted structures increase the surface area available for electron transport chain enzymes.

A

cristae

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44
Q

what is the space between the inner and outer membrane if the mitochondria called?

A

inter membrane space

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45
Q

what is the space inside the inner membrane of the mitochondria called?

A

mitochondrial matrix

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46
Q

What is the proton-motive force?

A

protons flowing through ATP synthase to generate ATP to generate ATP during oxidative phosphorylation.

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47
Q

how is the proton-motive force established?

A

by the pumping of protons from the mitochondrial matrix to the inter membrane space.

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48
Q

How is the mitochondria different from other organelles?

A

It is semi-autonomous, containing some of their own genes and replicate independently of the nucleus vis binary fission.

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49
Q

What organelle is an example of cytoplasmic or extranuclear inheritance?

A

mitochondria

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50
Q

what is extranuclear/cytoplasmic inheritance?

A

transmission of genetic material independent of the nucleus.

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51
Q

Mitochondria is believed to have evolved through what?

A

anaerobic prokaryote engulfing an aerobic prokaryote thereby establishing a symbiotic relationship.

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52
Q

which organelle keeps the cell alive by providing energy?

A

mitochondria

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53
Q

How does the mitochondria perform apoptosis (programmed cell death)?

A

by releasing enzymes from the electron transport chain which kick-starts apoptosis.

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54
Q

what are lysosomes?

A

membrane-bound structures containing hydrolytic enzymes that are capable of breaking down many substrates including substances ingested by endocytosis and cellular waste products.

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55
Q

lysosomes often function in conjunction with

A

endosomes

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56
Q

what is the purpose of lysosomes working with endosomes?

A

transporting, packaging and sorting cell material traveling to and from the membrane.

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57
Q

this structure is capable of transporting cell material to the trans-golgi, to the cell membrane or to the lysosomal pathway for degradation.

A

endosome

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58
Q

where are the lysosome’s hydrolytic enzymes sequestered in order to prevent cell damage?

A

in the lysosomal membrane.

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59
Q

the release of enzymes by the lysosome occurs in a process called

A

autolysis

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60
Q

what is the result of lysosomal release of hydrolytic enzymes?

A

apoptosis.

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61
Q

what is the endoplasmic reticulum?

A

a series of interconnected membranes that are contiguous to the nuclear membrane/envelope.

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62
Q

describe the ER

A

its double membrane is folded into numerous invaginations, creating complex structures with a central lumen.

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63
Q

what are the two types of ER?

A

smooth and rough

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64
Q

what is the rough ER?

A

it is the ER studied with ribosomes, permitting the translation of proteins destined for secretion directly into its lumen.

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65
Q

what is the smooth ER?

A

it is the ER that lacks ribosomes and is utilized primarily for lipid synthesis, detoxification of certain drugs and poisons, and transportation of proteins from the RER to the Golgi apparatus.

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66
Q

material from the ER are transferred to the Golgi in

A

vesicles

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67
Q

What is the Golgi apparatus?

A

stacked membrane-bound sacs.

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68
Q

what happens to material from the ER once they get to the GA?

A

they may be modified by the addition of various groups like carbs, phosphates and sulfates, or modification by the GA through introduction of signal sequences which direct the delivery of the product to a specific cellular location.

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69
Q

What happens after cellular products in the GA have bene modified?

A

they’re repackaged in vesicles and transferred to their correct cellular location, or put in secretory vesicles that merge with cell membrane and release the content out of the cell.

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70
Q

Through what process do secretory vesicles merge with cell membrane and release its content?

A

exocytosis.

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71
Q

What are peroxisomes?

A

structures that contain hydrogen peroxide

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72
Q

what are the functions of peroxisomes?

A
  • Primarily to breakdown very long chain fatty acids via B-oxidation.
  • Participate in the synthesis of phospholipids and contains some enzymes involved in the pentose phosphate pathway.
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73
Q

what is the purpose of the cytoskeleton?

A

providing structure to the cell and helping it maintain its shape, providing a conduit for the transport of materials around the cell.

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74
Q

what are the 3 types of cytoskeleton?

A

microfilaments, microtubules and intermediate filaments.

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75
Q

what are microfilaments made up of?

A

solid polymerized rods of actin organized in bundles and networks and are resistant to compression and fracture, providing protection to the cell.

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76
Q

how can actin filaments generate force for movement?

A

by using ATP and interacting with myosin such as in muscle contraction.

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77
Q

what is cytokinesis?

A

division of material between two daughter cells.

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78
Q

How do microfilaments contribute to cytokinesis?

A

during mitosis, the cleavage furrow formed is made up of filaments which organize as a ring at the site of division between the two new daughter cells.

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79
Q

what are microtubules?

A

hollow polymers of tubular proteins that radiate through the cell providing the primary pathways along which motor motor proteins like kinesin and dyne carry vesicles.

80
Q

which motile structures are made up of microtubules?

A

the cilia and flagella

81
Q

what are cilia?

A

projections from the cell that are primarily involved in the movement of material along the surface of the cell.

82
Q

what are flagella?

A

these are structures involved in the movement of the cell itself.

83
Q

the cilia and flagella share the same structure composed of how what?

A

9 pairs of microtubules forming and outer ring, two microtubules at the center.

84
Q

which structure is only seen in eukaryotic organelles of motility?

A

9 + 2 structure

85
Q

centrioles are found in the region of the cell called the

A

centrosome.

86
Q

what are centrioles?

A

organizing centers for microtubules structures as nine triplets of microtubules with a hollow center

87
Q

what is the function of centrioles in mitosis?

A

they migrate to opposite poles of the dividing cell and organize the mitotic spindle.

88
Q

microtubules emanating from centrioles attach to chromosomes via complexes that can exert force on the sister chromatid pulling them apart known as

A

kinetochores

89
Q

what are intermediate filaments?

A

diverse group of filamentous proteins including keratin, desmin, vimentin, and lamins involved in cell-cell adhesion or maintenance of the overall integrity of the cytoskeleton.

90
Q

what are the 4 types of tissues?

A

epithelial
connective
muscle
nervous

91
Q

which type of tissue covers the body and line its cavities providing a means for protection against pathogen invasion and dessication?

A

epithelial tissue

92
Q

to remain one cohesive unit, epithelial cells are tightly joined to each other and to an underlying layer of connective tissue known as the

A

basement membrane.

93
Q

in most organs, epithelial cells constitute what?

A

the parenchyma

94
Q

what is the parenchyma?

A

functional part of the organ.

95
Q

what are examples of organs parts composed of epithelial cells?

A

nephrons of the kidneys
hepatocytes of the liver
acid-producing cells of the stomach

96
Q

what does it mean that epithelial cells are often polarized?

A

one side faces the lumen or the outside world while the other side interacts with the underlying blood vessels and structured cells.

97
Q

distinguish the different epithelia

A
  • simple epithelia: one layer of cells
  • stratified epithelia: multiple layers
  • pseudo-stratified: seems to have multiple layer due to cell height but only have one
98
Q

distinguish the different shapes of epithelia

A

squamous: flat, scale-like
cuboidal: cube-shapped
columnar: long and thin

99
Q

this tissue supports the body and provides a framework for the epithelial cells to carry out their functions.

A

connective tissue

100
Q

the same way epithelial cells constitute the parenchyma, connective tissue constitute the

A

stroma / support structure.

101
Q

list some examples of connective tissue

A

bone, cartilage, tendons, ligaments, adipose tissue, blood etc

102
Q

what do most cells in connective tissue produce and secrete?

A

materials such as collagen and elastin to form extracellular matrix.

103
Q

prokaryotes include what type if organisms?

A

all bacteria

104
Q

what are prokaryotes?

A

cell types that do not contain any membrane-bound organelle, and whose genetic material is organized into a single circular molecule of dna concentrated in an area of the cell called the nucleic region.

105
Q

what are the 3 domains in which all life is classified

A

archaea
bacteria
eukarya

106
Q

what are archaea?

A

single-celled organisms that are visually similar to bacteria but contain genes and several metabolic pathways similar to to eukaryotes.

107
Q

why were archaea considered extremophiles?

A

they were most commonly isolated from harsh environments with extremely high temperatures, high salinity, or no light

108
Q

how are eukaryotes and archaea similar?

A

both start translation with methionine, contain similar RNA polymerases and associate their dna to histones.

109
Q

how are archaea different from eukaryotes but similar to bacteria?

A

single circular chromosome

divide by binary fission or budding

110
Q

all bacteria contain a

A

cell membrane and cytoplasm

111
Q

what motility factor do some bacteria have?

A

flagella or fimbriae

112
Q

how many bacteria are there on earth?

A

~ 5 x 10^30

113
Q

what does it mean when bacteria are said to be mutualistic symbiotes?

A

both humans and bacteria benefit from the relationship

114
Q

give examples of mutualistic symbolism in the body

A
  • bacteria in the human gut that produce vitamin K and biotin (vitamin b7) preventing the overgrowth of harmful bacteria.
  • lactobacillus in the female giant tract protecting and maintaining the acidic environment keeping it healthy and less susceptible to infection.
115
Q

when bacteria are not mutualistic symbiotes, what are they?

A

pathogens or parasites meaning they provide no advantage or benefit to the host, but rather cause disease.

116
Q

pathogenic bacteria live

A

intracellularly (Chlamydia trachomatis)

extracellularly (Clostridium tetani)

117
Q

Most bacteria exist in three shapes. Name them

A

cocci
bacilli
spirilli

118
Q

bacteria that require oxygen for metabolism are called

A

obligate aerobes.

119
Q

bacteria that use fermentation or some other form of cellular metabolism that dies not require oxygen are called

A

anaerobes

120
Q

anaerobes that can’t survive in oxyegen-containing environments are called

A

obligate anaerobes

121
Q

why do obligate anaerobes die in the presence of oxygen?

A

the presence of oxygen cause leads to the production of reactive oxygen-containing radicals in them.

122
Q

organisms that can switch between aerobic and anaerobic metabolisms are known as

A

facultative anaerobes

123
Q

what are aerotolerant anaerobes?

A

organisms unable to use oxygen for metabolism but that are not harmed by their presence.

124
Q

what are the main differences between prokaryotes and eukaryotes?

A
  • prokaryotes lack a nucleus and membrane-bound organelle.
  • prokaryotes are single-celled so each cell must be able to perform all the functions necessary for life.
  • prokaryotes have both cell wall and cell membrane, eukaryotes only have a cell membrane.
125
Q

together, the cell wall and cell membrane of a prokaryote is called

A

the envelope.

126
Q

what is the purpose of the cell wall?

A

providing structure and controlling the movement of solutes into and out of the bacteria.

127
Q

what are the two types of bacteria cell wall?

A

gram positive and gram negative

128
Q

a bacteria’s cell wall type is determined by what

A

the gram staining process with crystal violet stain followed by a safranin counter stain.

129
Q

what is the difference between gram positive and gram negative?

A

if the bacteria’s envelope absorbs crystal violet, it produces a purple color which is said to be gram positive, and if it absorbs safranin, it shows pink called gram negative.

130
Q

what makes gram positive bacteria absorb crystal violet?

A

their cell wall consist of a thick layer of petidoglycan, a polymeric substance made from amino acids and sugars.

131
Q

gram positive cell walls are composed of what other substance aside peptidoglycan?

A

lipoteichoic acid

132
Q

why do gram negative bacteria absorb safranin?

A

they have a much smaller layer of peptidoglycan, adjacent to the cell membrane but separated from it by the periplasmic space, and have outer membranes containing phospholipids and lipopolysaccharides.

133
Q

what substance in gram negative bacteria triggers an immune response in human beings?

A

lipopolysaccharides.

134
Q

what are flagella?

A

long, whip-like structures that can be used for propulsion.

135
Q

what do bacteria use flagella for?

A

bacteria use flagella to move towards food or away from toxins or immune cells.

136
Q

the ability of a cell to detect chemical stimuli and move towards or away from them is known as

A

chemotaxis

137
Q

what is the composition of flagella?

A

a filament, basal body and a hook.

138
Q

describe the flagella’s filament

A

hollow, helical structure composed of flagellin.

139
Q

describe the flagella’s basal body

A

complex structure that anchors the flagellum to the cytoplasmic membrane and is the motor of the flagellum, rotating at rates up to 300Hz

140
Q

what is the function of a flagellum’s hook?

A

connects the basal body and the filament.

141
Q

how is prokaryotic dna carried?

A

on a single circular chromosome found coiled around histone-like proteins in some bacteria.

142
Q

True histone proteins are found in

A

archaea and eukaryotic

143
Q

dna acquired by bacteria through external sources may be carried on smaller circular structures called

A

plasmids.

144
Q

what are plasmids?

A

small circular structures that carry dna that is not necessary for survival of the prokaryote but may confer an advantage such as antibiotic resistance.

145
Q

How is a flagellum different in a eukaryote and prokaryote?

A

in eukaryotes, flagellum have 9 pairs of filaments with 2 filaments at the center, while in prokaryotes, they have a basal body, a hook and a filament.

146
Q

how do prokaryotes reproduce?

A

via asexual reproduction in the form of binary fission.

147
Q

who between prokaryotes and eukaryotes are capable of obtaining genetic material from outside the cell and using it?

A

prokaryotes.

148
Q

what is binary fission?

A

it is the term used for asexual reproduction by prokaryotes

149
Q

describe binary fission

A

the circular chromosome attaches to the cell wall and replicates while the cell continues to grow in size. The cell wall and membrane begin to grow inward along the midline of the cell to produce two identical daughter cells.

150
Q

aside antibiotic resistance, what other advantages can plasmids provide a bacteria with

A

additional virulence factors like how pathogenic a bacterium is such as toxin production, projections that allow the bacterium to attach to certain kinds of cells, evasion of host’s immune system.

151
Q

The subset of plasmids that is capable of integrating into a bacterium’s genome is called

A

episomes

152
Q

This helps increase bacterial diversity, thus permitting evolution of a bacterial species over time.

A

bacterial genetic recombination

153
Q

what are the three bacterial genetic recombination processes?

A

transformation
conjugation
transduction

154
Q

The integration of foreign genetic material into the host genome results in what genetic recombination process?

A

transformation

155
Q

what is the source of foreign genetic material during transformation?

A

most frequently comes from other bacteria that upon lysing, spill their contents in the vicinity of a bacterium capable of transformation.

156
Q

what is the bacterial form if sexual reproduction (mating) called?

A

conjugation.

157
Q

what does conjugation involve?

A

two cells forming a conjugation bridge between them that facilitates a unidirectional transfer of genetic material from donor male (+) to recipient female (-)

158
Q

what is a conjugation bridge made up of?

A

appendages called sex pili that are found on the donor male.

159
Q

how can a male donor form a plus for conjugation?

A

the male donor must contain plasmids known as sex factors that contain the necessary genes.

160
Q

what is the sex factor in E. coli?

A

F (fertility) factor

161
Q

Cells that undergo a transformation process in which the plasmid of the donor integrates its genome and replicates, then the entire copy of its genome is transferred to the recipient although the bridge usually breaks are termed

A

high frequency of recombination (Hfr)

162
Q

the only genetic recombination process that requires a vector is

A

transduction

163
Q

what is a vector in transduction?

A

a virus that carries genetic material from one bacterium to another.

164
Q

what term describes the nature of viruses not being able to reproduce outside of a host cell?

A

they’re obligate intracellular pathogens

165
Q

viruses that infect bacteria are called

A

bacteriophages.

166
Q

The process by which a bacteriophage traps a segment of a host bacterium’s dna during assembly and infects another bacterium with it thereby conferring the new host additional genes is called

A

transduction

167
Q

genetic elements capable of inserting and removing themselves from the genome and called?

A

transposons

168
Q

what are the different phases of bacterial growth?

A
  • Lag phase
  • Exponential/log phase
  • Stationary phase
  • Death phase
169
Q

the bacterial growth phase in which the bacteria first adapt to a new environments called the

A

lag phase

170
Q

the bacterial growth phase in which bacteria adapt and grow in the colony is called

A

exponential phase

171
Q

the bacterial growth phase in which resources reduce leading to slow bacterial reproduction is called the

A

stationary phase

172
Q

the bacterial growth phase in which the bacteria have exceeded the ability of the environment to support their number and death occurs is the

A

death phase

173
Q

why are viruses considered non-living things?

A

they’re acellular

174
Q

what is the common structure of a virus?

A

viruses are composed of genetic material, a protein coat and sometimes an envelope containing lipids.

175
Q

what is the nature of viruses’ genetic material?

A

may be circular or linear, single or double-stranded, and composed of either dna or rna.

176
Q

a virus’s protein coat is called a

A

capsid

177
Q

why are enveloped viruses easier to kill?

A

because envelopes are composed of phospholipids and virus-specific proteins that are very sensitive to heat, detergents and dessication.

178
Q

what type of viruses are more resistant to sterilization and are likely to persist on surfaces for an extended period of time?

A

viruses that do not have an envelope.

179
Q

what feature of viruses make them express and replicate genetic information only within a host’s cell?

A

viruses lack ribosomes to carry out protein synthesis.

180
Q

after invading a host cell, a virus will replicate and produce viral progeny which can be released to infect addition cells. This viral progeny is called

A

virions

181
Q

what are bacteriophages?

A

viruses that specifically target bacteria

182
Q

describe the action of bacteriophages?

A

bacteriophages do not actually enter the bacteria. They simply inject their genetic material, leaving the remaining structure outside the infected cell.

183
Q

how do bacteriophages differ from regular viruses in terms of physical structure?

A

bacteriophages in addition to capsid contain a tail sheath and tail fibers.

184
Q

what is a tail sheath on a bacteriophage for?

A

the tail sheath acts like a syringe, injecting genetic material into a bacterium.

185
Q

what is the use of tail fibers?

A

they help the bacteriophage recognize and connect to the correct host cell.

186
Q

Single-stranded RNA viruses may be positive sense or negative sense. What is the difference?

A

positive sense means the genome may be directly translated into functional proteins just like mRNA, while negative sense implies the virus requires synthesis of an RNA strand complimentary to the negative sense strand before it can be used as template for protein synthesis.

187
Q

what are retroviruses?

A

enveloped single-stranded RNA viruses from the Retroviridae family of viruses.

188
Q

usually, the virion of retroviruses contain

A

2 identical RNA molecules.

189
Q

retroviruses carry an enzyme known as

A

reverse transcriptase.

190
Q

what does the enzyme reverse transcriptase do?

A

it synthesizes DNA from single-stranded RNA

191
Q

what must negative sense RNA viruses carry in their virion to ensure that the complimentary strand is synthesized?

A

RNA replicase

192
Q

what mechanism does HIV as well as other retroviruses possess that make them so hard to treat?

A

the synthesizes DNA by reverse transcriptase invades the host cell genome where it replicates and transcribes as if it were the host cell’s own DNA, which allows the cell to be infected indefinitely, and the only way to cure the infection is by killing the cell itself.

193
Q

what does a virus need to infect a cell?

A

it needs to bind to specific receptors on the host cell

194
Q

what are the steps of viral life cycle?

A

infection
translation and progeny assembly
projeny release

195
Q

what happens after viral infection?

A

translation of viral genetic material must occur in order for theirs to reproduce.

196
Q

how do viroids function?

A

by binding to a large number of rna sequences and silencing genes in plant genome, preventing synthesis of necessary proteins, subsequently causing metabolic and structural derangements in the plant cell.

197
Q

viroids are considered pathogens. What is an example of a viroid that affects humans?

A

Hepatitis D virus (HDV)

MCAT Biology (2 decks)

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