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mcat biology > Chapter 1: The Cell > Flashcards

Chapter 1: The Cell Flashcards

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1
Q

What is Robert Hooke known for? (c. 1665)

A

Assembling the first crude compound microscope and looking at cork

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2
Q

What is Anton van Leeuwenhoek known for? (c. 1674)

A

First to view a living cell under a microscope

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3
Q

What is Rudolph Virchow known for? (c. 1850)

A

Demonstrating that diseased cells could arise from normal cells in normal tissues

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4
Q

What are the three basic tenets of cell theory?

  1. All living things are composed of ____.
  2. The cell is the basic ____________ ______ of life.
  3. Cells arise only from ____________ ______.

high yield

A
  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
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5
Q

What is the 4th newly added tenet of cell theory?

high yield

A
  1. Cells carry genetic info in the form of DNA, which is passed on from parent to daughter cell
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6
Q

What are viruses? Are they alive?

A

Viruses are small structures that contain genetic material but cannot reproduce on their own.

This violates the 3rd and 4th tenet because they can only replicate by invading other organisms and because they can use RNA as their genetic info.

They are not considered alive.

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7
Q

Prokaryotic Organism - how many cells?

A

Always single-celled

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8
Q

Eukaryotic organism - how many cells?

A

Unicellular OR multicellular

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9
Q

Eukaryotic Cells have a _____ nucleus.

A

Contain a true nucleus enclosed in a membrane

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10
Q

Prokaryotic Cells- has nucleus?

A

do NOT contain a nucleus

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11
Q

What type of cells are organelles found in?

A

Only in eukaryotic cells, not prokaryotic

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12
Q

What surrounds cells and what is inside cells?

A

Cells are surrounded by a membrane that has a phospholipid bilayer.

Inside the cell is cytosol (liquid that fills the cell), and cytosol + organelles = cytoplasm

Organelles are surrounded by their own membrane

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13
Q

What is the phospholipid bilayer?

A

A thin polar membrane made of two layers of lipid molecules

Its surfaces are hydrophilic and interact with the aqueous environments

Inner portion of the bilayer is hydrophobic; allows it to be highly selective

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14
Q

How do eukaryotic cells reproduce?

A

By mitosis

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15
Q

What is the nucleus surrounded by?

A

A nuclear envelope/membrane (double membrane) that has nuclear pores (for selective 2-way exchange)

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16
Q

What are histones?

A

organizing proteins (have a lot of lysine and arginine residues) that are found in eukaryotic cell nuclei.

They act as spools around which DNA winds to create structural units called nucleosomes

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17
Q

What is a nucleosome and what is its structure?

A

Basic structural unit of DNA packaging in eukaryotes

The structure of a nucleosome consists of a segment of DNA wound around 8 histone proteins (octamer) and is like thread wrapped around a spool

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18
Q

What is chromatin and what is it made up of?

A

Chromatin is made up of DNA and associated proteins (histones)

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19
Q

What are chromosomes and what are they made up of?

A

Long DNA molecule with part or all of the genetic material of an organism

Composed of condensed chromatin fibers

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20
Q

Where in the cell is DNA located?

A

In the nucleus

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21
Q

What is the nucleolus and what does it do?

A

A subsection of the nucleus, where ribosomal RNA (rRNA) is synthesized. Takes up 25% of the nucleus’ volume (looks like a darker spot in the nucleus)

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22
Q

How many layers does the mitochondrion have?

A

2; inner and outer layers

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23
Q

What is the function of the outer membrane of the mitochondrion?

A

barrier between cytosol and inner environment of mitochondrion

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24
Q

What is the function of the outer membrane of the mitochondrion?

A

It contains the molecules/enzymes of the electron transport chain

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25
Q

What is the structure of the mitochondrion’s inner membrane like?

A

It has numerous infoldings called cristae, which are highly convoluted so as to increase surface area available for electron transport chain enzymes

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26
Q

What is the space between the inner and outer membranes of the mitochondrion called?

A

Intermembrane space

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27
Q

What is the space inside the mitochondrion’s inner membrane called?

A

Mitochondrial matrix

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28
Q

What is the proton pump of the mitochondria?

A

The pumping of protons from the mitochondrial matrix to the intermembrane space establishes the proton-motive force.

These protons flow through ATP synthase to generate ATP during oxidative phosphorylation

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29
Q

What is extranuclear inheritance and what is an example of it?

A

The transmission of genetic material independent of the nucleus.

Example: the mitochondria are semi-autonomous, as they contain some of their own genes and replicate independently of the nucleus via binary fission

They are thought to have originated when an anaerobic prokaryote engulfed an aerobic prokaryote, establishing a symbiotic relationship

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30
Q

What role do mitochondria play in apoptosis?

A

They release enzymes from the electron transport chain that kickstarts the process of apoptosis

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31
Q

What are lysosomes?
What type of enzymes do they have?
What do those enzymes do?

A

membrane-bound structures that contain hydrolytic enzymes that breakdown many different substrates, e.g. substances ingested by endocytosis and cellular waste products

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32
Q

What are endosomes?

A

Intracellular sorting organelles that transport, package, and sort cell material traveling to/from membrane

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33
Q

Where do endosomes transport materials?

A

To the trans-golgi, the cell membrane, or lysosomal pathway for degradation

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34
Q

What is autolysis?

A

When lysosomal enzymes are released, resulting in apoptosis, which leads directly to the degradation of cellular components

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35
Q

What is the endoplasmic reticulum?
What is its membrane like?

A

A series of interconnected membranes that are contiguous with the nuclear envelope.

Its membrane is folded into numerous invaginations, which creates complex structures with a central lumen

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36
Q

What are the two types of ER?

A

Smooth and Rough ER

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37
Q

What is the difference between smooth and rough ER?

A

Rough ER has ribosomes, smooth ER does not

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38
Q

What is the function of the rough ER (and its ribosomes)?

A

They permit translation of proteins directly into its lumen. These proteins are destined for secretion.

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39
Q

What are the 3 main functions of the smooth ER?

A

It lacks ribosomes, but is used primarily for lipid synthesis, e.g. phospholipids in the cell membrane, detoxification of certain drugs and poisons, and transportation of proteins

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40
Q

The smooth ER transports proteins from the ______ to the ______ __________.

A

The smooth ER transports proteins from the RER to the Golgi apparatus.

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41
Q

What is the structure of the Golgi apparatus?

A

It is composed of stacked membrane-bound sacs

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42
Q

How are materials transferred from the RER to the Golgi appartus?

A

They are transferred in vesicles

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43
Q

What happens inside the Golgi apparatus?

A

Cellular modification can occur

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44
Q

What happens inside the Golgi apparatus?

A

Cellular modification can occur

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45
Q

What are two ways that the Golgi appartus can modify cellular products?

A
  1. Adding groups like carbohydrates, phosphates, and sulfates
  2. Introducing signal sequences to direct the delivery of the product to a specific cellular location
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46
Q

What happens after the Golgi apparatus modifies and sorts cellular products?

A

The cellular products are repackaged in vesicles, which are then directed to the correct cellular location.

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47
Q

What happens to products coming from the Golgi apparatus that are destined for secretion?

A

The secretory vesicles merge with the cell membrane, and its contents are released via exocytosis

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48
Q

Draw

The relationship between lysosomes, ER, and Golgi apparatus

A
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49
Q

What are peroxisomes? What are their 2 main roles?

A

They contain hydrogen peroxide and:
1. Breakdown very long chain fatty acids
2. Synthesize phospholipids and contain some of the enzymes involved in the pentose phosphate pathway

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50
Q

By what process do peroxisomes breakdown fatty acids?

A

β-oxidation

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51
Q

What is the cytoskeleton? What are its main functions?

A

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

Also provides a conduit for transportin materials around the cell.

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52
Q

What are 3 components of the cytoskeleton?

A
  1. microfilaments
  2. microtubules
  3. intermediate filaments
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53
Q

What are microfilaments?

A

A type of cytoskeleton; a small rodlike structure, about 4–7 nanometers in diameter, present in numbers in the cytoplasm of many eukaryotic cells.

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54
Q

Microfilaments are made up of solid polymerized rods of ______.

A

Actin

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55
Q

How are actin filaments organized in cytoskeleton?

A

The actin filaments are organized into bundles and networks and are resistant to both compression and fracture; provides protection for cell

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56
Q

How does actin effect movement?

A

They use ATP to generate force for movement by interacting with myosin, e.g. muscle contraction

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57
Q

What is cytokinesis?

A

The division of materials between daughter cells; microfilaments play a role in cytokinesis.

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58
Q

What is the role of microfilaments in mitosis?

A

Microfilaments form the cleavage furrow during mitosis, which organize as a ring at the site of division between the 2 new daughter cells.

The actin filaments within the ring contract, make the ring smaller, which eventually pinches off the connection between the 2 daughter cells

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59
Q

What are microtubules?

A

A type of cytoskeleton; hollow, rigid polymers, approximately 25 nm in diameter

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60
Q

Microtubules are made up of hollow polymers of ______ proteins.

A

Tubulin

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61
Q

Microtubules form the primary pathways along which motor proteins like ______ and ______ carry vesicles.

A

Kinesin and dynein

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62
Q

Microtubules also comprise ______ and ______, which are motile structures on the surface of the cell.

A

Cilia and flagella

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63
Q

What are cilia and what is their function?

A

Cilia are projections from a cell made of microtubules and are involved in the movement of materials along the surface of the cell.

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64
Q

What are flagella and what is their function?

A

Flagella are structures made of microtubules and are involved in the movement of the cell itself

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65
Q

What is the structure of cilia and flagella in eukaryotic organelles

A

9 + 2 structure
9 pairs of microtubules forming an outer ring, with 2 microtubules in the center

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66
Q

What is a centrosome?

A

an organelle near the nucleus of a cell which contains the centrioles (in animal cells) and from which the spindle fibers develop in cell division.

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67
Q

What are centrioles and what is their structure?

A

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

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68
Q

What do centrioles do during mitosis?

First, they migrate to ________ ______ of the dividing cell and organize the __________ ________.

Then, the microtubules that emanate from the centrioles attach to the ______________ via complexes called ______________ and exert force on the ________ ____________, pulling them apart.

A

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

Then, the microtubules that emanate from the centrioles attach to the chromosomes via complexes called kinetochores and exert force on the sister chromatids, pulling them apart.

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69
Q

What are intermediate filaments and what are their function?

A

A type of cytoskeleton; a diverse group of filamentous proteins, e.g. keratin, desmin, lamins, etc.

They are primarily involved in cell-cell adhesion or maintenance of cytoskeleton integrity

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70
Q

What are 2 reasons that intermediate filaments important for cell structure?

A

They can withstand a lot of tension to increase the structural rigidity of the cell AND they anchor other organelles, like the nucleus

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71
Q

What determines the identity of the intermediate filament proteins within a cell?

A

The cell and tissue type

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72
Q

What are each type of cytoskeleton made up of?

A

Microfilaments ~ actin
Microtubules ~ tubulin
Intermediate filaments ~ diverse group of filamentous proteins

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73
Q

What does each type of cytoskeletal protein make up / what are their roles?

A

Microfilaments
* cleavage furrow during mitosis
* interacting with myosin to cause movement

Microtubules
* paths for kinesin and dynein to walk on
* forming cilia and flagella

Intermediate filaments
* cell-cell adhesion and cytoskeleton integrity

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74
Q

What are the four types of tissue?

A
  1. Epithelial
  2. Connective
  3. Muscle
  4. Nervous
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75
Q

Where is epithelial tissue found and what does it do?

A

Covers the body and lines its cavities

It protects against pathogen invasion and desiccation, and have numerous functions depending on the identity of the organ in which they are found

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76
Q

How do epithelial cells remain as one cohesive unit? What structure is involved?

A

They are joined tightly to each other and to an underlying layer of connective tissue known as the basement membrane

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77
Q

What do epithelial cells constitute in most organs?

A

The parenchyma, which is the functional part of an organ

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78
Q

What is a unique quality of epithelial cells?

A

They are polarized, meaning 1 side faces a lumen (hollow inside of an organ or tube) or the outside world, whereas the other side interacts with underlying blood vessels and structural cells

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79
Q

How are different epithelia classified? (what 2 features?)

A
  1. The # of layers they have
  2. The shape of their cells
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80
Q

What are the different types of epithelia as classified by # of layers?

  1. Which epithelia have a single layer of cells?
  2. Which epithelia have multiple layers of cells?
  3. Which epithelia seem to have multiple layers due to differences in cell height but are, in reality, only 1 layer?
A
  1. Simple epithelia
  2. Stratified epithelia
  3. Pseudostratified epithelia
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81
Q

What are the different types of epithelia as classified by shape of cells?

  1. Which epithelia have cube-shaped cells?
  2. Which epithelia have long and thin cells?
  3. Which epithelia have flat and scale-like cells?
A
  1. Cuboidal epithelia
  2. Columnar epithelia
  3. Squamous epithelia
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82
Q

What does connective tissue do?

A

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

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83
Q

What do connective tissues constitute in most organs?

A

The stroma, or support structure

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84
Q

Most cells in connective tissues produce and secrete materials such as collagen and elastin to form the ______________ ______.

A

Most cells in connective tissues produce and secrete materials such as collagen and elastin to form the extracellular matrix.

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85
Q

Do prokaryotes contain membrane-bound organelles?

A

NO.

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86
Q

How is prokaryotic genetic material organized?

A

A single circular molecule of DNA

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87
Q

Where is prokaryotic DNA concentrated in the cell?

A

the nucleoid region

88
Q

What is prokaryotic DNA coiled around?

A

Histone-like proteins

89
Q

Does Archaea have histones?

A

Yes, they are true histones.

90
Q

What are the three domains into which all life is classified?

A

Archaea
Bacteria
Eukarya

91
Q

Which of the three domains of life are prokaryotic?

A

Bacteria
Archaea

92
Q

What are archaea?

A

Single-celled organisms that are visually similar to bacteria but contain genes/metabolic pathways that are more similar to eukaryotes

93
Q

What are extremophiles?

A

This is what archaea used to be considered - they are more commonly isolated from harsh environments with extremely high temperatures, high salinity, or no light

94
Q

What is notable about Archaea’s metabolism?

A

They can utilized different types of energy; some photosynthesize, chemosynthesize, and can generate energy from inorganic compounds, like ammonia

95
Q

List 3

What are the similarities between Archaea and Eukarya?

A
  • Start translation with methionine
  • Contain similar RNA polymerases
  • Associate their DNA with histones
96
Q

list 3

What are the differences between Archaea and Eukarya?

A
  • Archaea has a single circular chromosome
  • Archaea divides by binary fission or budding
  • Archaea are more structurally similar to bacteria

Archaea are also resistant to many antibiotics

97
Q

What are 2 structures that all bacteria have?

A

A cell membrane and cytoplasm

98
Q

What structures do some bacteria have?

A

Flagella
Fimbriae (like cilia)

99
Q

What is a mutualistic symbiotic relationship?

A

Both human and bacteria benefit

100
Q

What are pathogens or parasites?

A

Provide no advantage/benefit, instead cause disease

101
Q

What are the 3 main shapes of bacteria?

A

Cocci = spherical
Bacilli = rod-shaped
Spirilli = spiral-shaped

102
Q

Which bacteria require oxygen for metabolism?

A

Obligate aerobes

103
Q

Which bacteria uses fermentation or other forms of cellular metabolism that do not require oxygen?

A

Anaerobes

104
Q

What are the 3 different types of anaerobes?

A

Obligate anaerobes
Facultative anaerobes
Aerotolerant anaerobes

105
Q

What are obligate anaerobes?

A

Cannot survive in an oxygen-containing environment

106
Q

What happens to obligate anaerobes when they are exposed to oxygen?

A

They produce reactive oxygen-containing radicals that cause cell death

107
Q

What are facultative anaerobes?

A

They can toggle between metabolic processes, using oxygen for aerobic metabolism if present, and switching back to anaerobic metabolism if not

108
Q

What are aerotolerant anaerobes?

A

They cannot use oxygen for metabolism, but are not harmed by its presence in the environment

109
Q

What are the biggest differences between eukaryotes and prokaryotes?

A

Prokaryotes are single-celled and lack a nucleus and membrane-bound organelles

110
Q

List from outside to inside

What are the components of the outer protective structure of a bacterium?

2 major parts

A

Cell wall
Cell membrane (plasma membrane)

111
Q

What is the “cell wall + cell membrane” together referred to as?

A

Cell envelope

112
Q

List 2

What are the main roles of the cell wall?

A
  1. Provide structure
  2. Control the movement of solutes into and out of the bacterium
113
Q

What are the 2 main types of bacterial cell walls?

A

Gram positive and Gram negative

114
Q

What experimental technique determines the type of bacterial cell wall?

A

The Gram staining process

115
Q

The Gram staining process involves the use of a ______ ______ stain, followed by a counterstain with a substance called ________.

A

The Gram staining process involves the use of a crystal violet stain, followed by a counterstain with a substance called safranin.

116
Q

What color is a gram positive bacteria? Why?

A

Deep purple - it absorbs the crystal violet stain

117
Q

What color is a gram negative bacteria?

A

Pink-red - it absorbs the safranin counterstain

118
Q

What are the 2 things that gram-positive cell walls consist of?

A

Peptidoglycan
Lipoteichoic acid

119
Q

What is peptidoglycan?

A

A polymeric substance made from amino acids and sugars

120
Q

What effect does lipoteichoic acid possibly have on the human body?

A

It may activate the immune system by exposure to these chemicals

121
Q

What are gram-negative cells like?

Thick or thin? Do they have peptidoglycan?

A

Very thin! Contain peptidoglycan but in much smaller amounts than gram-positive.

122
Q

What are additional components of gram-negative outer structures (in addition to cell wall and cell membrane?

What 2 things do these components contain?

A

Outer membranes containing phospholipids and lipopolysaccharides

123
Q

What reaction do lipopolysaccharides cause in humans? How does this reaction compare to lipoteichoic acid?

A

It triggers the immune response. The response is much stronger than the response to lipoteichoic acid.

124
Q

What are flagella?

A

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

125
Q

What role do flagella play?

A

They aid bacteria in moving toward food or away from toxins or immune cells

126
Q

What is the ability of a cell to detect chemical stimuli and move toward or away from them called?

A

Chemotaxis

127
Q

What are the 3 primary components of a flagella?

A

Filament
Basal body
Hook

128
Q

What is the filament of a flagella and what is it made of?

A

The filament is a hollow, helical structure composed of flagellin

129
Q

What is the basal body of the flagella?

A

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

130
Q

What is the hook of the flagella?

A

It connects the filament and the basal body so that, as the basal body rotates, it exerts torque on the filament, which thereby spins and propels the bacterium forward

131
Q

What are plasmids?

A

Smaller circular DNA structures that carry bacterial DNA (usually an external source)

This material is “extrachromosomal (extragenomic)”

132
Q

What type of bacterial DNA do plasmids carry? What advantage could it confer on bacteria?

A

The DNA on plasmids is not necessary for prokaryotic survival, thus, it is not considered part of the bacterial genome. It may confer advantages like antibiotic resistance

133
Q

What major eukaryotic organelle do prokaryotes lack?

A

Mitochondria

134
Q

Since prokaryotes do not have mitochondria, how do they generate energy?

A

The cell membrane is used for the electron transport chain and generation of ATP

135
Q

Do prokaryotes have a cytoskeleton?

A

Yes, but it is primitive and not nearly ascomplex as the eukaryotic cytoskeleton

136
Q

What is the difference between prokaryotic and eukaryotic ribosomes?

A

Prokaryotic = 30S and 50S subunits
Eukaryotic = 40S and 60S subunits

137
Q

How do prokaryotes reproduce?

A

Asexual reproduction in the form of binary fission

138
Q

What can prokaryotes do with external genetic material?

A

They can acquire and utilize it

139
Q

What is binary fission?

A

A simple form of prokaryotic asexual reproduction

140
Q

What are the steps in binary fission?

2 steps

A
  1. The circular chromosome attaches to the cell wall and replicates while the cell continues to grow in size
  2. The plasma membrane and cell wall grow inward along the midline of the cell to produce 2 identical daughter cells
141
Q

Which is quicker - binary fission or mitosis? Why?

A

Binary fission - there are fewer steps

142
Q

What are virulence factors and where are they found?

A

Virulence factors may be carried on plasmids and they increase bacterial pathogenicity

e.g. may aid toxin production, create projections that allow attachment to certain cells, or evade host’s immune system

143
Q

What are the three main modes of genetic transfer/recombination in bacteria?

A

Transformation
Conjugation
Transduction

144
Q

What does genetic recombination accomplish?

A

It increases bacterial diversity and permits bacterial evolution over time.

145
Q

What type of plasmids can be integrated into the bacterial genome?

A

Episomes

146
Q

What is bacterial transformation?

A

The integration of foregin genetic material into the host genome

147
Q

Where does genetic material come from in bacterial transformation?

A

From other bacteria that spill their contents (upon lysing) into the vicinity of a bacterium that can undergo transformation

148
Q

What type of bacteria commonly carries out transformation?

A

Gram-negative rods

149
Q

What is bacterial conjugation?

A

A bacterial form of sexual reproduction

2 cells form a conjugation bridge that facilitates the transfer of genetic material.

150
Q

What direction does bacterial conjugation occur in?

A

Unidirectionally, from the donor male (+) to the recipient female (-)

151
Q

What is the bacterial conjugation bridge made of?

A

Appendages called sex pili that are found on the donor male

152
Q

How is the sex pilus made?

A

Bacteria must contain plasmids known as sex factors that contain the necessary genes

153
Q

What is the F (fertility) factor?

A

A sex factor in E. coli. During conjugation, an F+ cell replicates its F factor and donates the copy to the F- cell to convert the F- to an F+. Now that cell can carry out conjugation.

154
Q

What process allows the sex factor plasmid to be integrated into the host genome?

A

Transformation

155
Q

What is special about cells that have a high frequency of recombination (Hfr)?

A

They have incorporated an F factor into their chromosome and can then transfer the chromosome during conjugation.

156
Q

What is a vector?

A

A virus that carries genetic material from one bacterium to another

157
Q

What is bacterial transduction?

A

the process by which DNA is transferred from one bacterium to another by a vector

158
Q

What is a bacteriophage?

A

A virus that can infect bacteria specifically

159
Q

Viruses are obligate intracellular pathogens. What does this mean?

A

They cannot reproduce outside of a host cell.

160
Q

Because bacteriophages are obligate intracellular pathogens, what can happen during their assembly?

A

They can accidentally incorporate a segment of host DNA

161
Q

What happens when a bacteriophage (that has incorporated a previous host’s DNA) infects another bacterium?

A

It can release trapped DNA into the new host cell, which can then be integrated into the bacterial genome, giving the new host additional genes

162
Q

What are transposons?

A

Genetic elements capable of inserting and removing themselves from the genome

163
Q

Where are transposons found?

A

Prokaryotes and eukaryotes

164
Q

What happens if a transposon is inserted within a coding region of a gene?

A

The gene may be disrupted

165
Q

What are phases of bacterial growth?

A
  1. Lag phase
  2. Exponential/log phase
  3. Stationary phase
  4. Death phase
166
Q

What occurs during the lag phase of bacterial growth?

A

Bacteria adapt to their new environment’s conditions

167
Q

What occurs during the exponential/log phase of bacterial growth?

A

The rate of division increases exponentially

168
Q

What occurs during the stationary phase?

A

Resources are depleted after the exponential phase, leading to slowed reproduction

169
Q

What occurs in the death phase?

A

The environment can no longer support the number of bacteria and resources are depleted

170
Q

What are main components of viruses?

A

Genetic material
Protein coat
Sometimes an envelope containing lipids

171
Q

What is the viral protein coat known as?

A

Capsid

172
Q

What are some capsids surrounded by?

A

An envelope composed of phospholipids and virus-specific proteins

173
Q

What is a special quality of the viral envelope?

A

It is very sensitive to heat, detergents, and dessication, making it easier to kill

174
Q

How do viruses reproduce?

A

They depend on a host cell in which they must express and replicate their genetic info.

175
Q

Why can’t viruses reproduce independently?

A

They lack ribosomes to carry out protein synthesis

176
Q

What happens after a virus hijacks a cell’s machinery? What are viral progeny called?

A

It replicates and produces viral progeny called virions that can be released to infect additional cells

177
Q

How do bacteriophages infect bacteria?

A

They simply inject their genetic material (without entering) and leave the remaining structures outside the infected cell

178
Q

What other structures does a bacteriophage contain?

2 structures

A

A tail sheath and tail fibers

179
Q

What is a viral tail sheath?

A

It acts like a syringe that injects genetic material into a bacterium

180
Q

What are viral tail fibers?

A

They help the bacteriophage recognize and connect to the correct host cell. They serve as an anchor to the host cell membrane

181
Q

What quality do some tail fibers have?

A

Enzymatic activity, allowing for cell wall penetration and poreformation in the cell membrane

182
Q

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

A

Positive sense and negative sense

183
Q

What are positive sense ssRNA viruses?

A

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

184
Q

What are negative-sense ssRNA viruses?

A

They act as a template for synthesis of a complementary strand, which can then be used as a template for protein synthesis

185
Q

What does a negative-sense ssRNA virus need for synthesis?

A

The virion must carry RNA replicase to ensure the synthesis of the complementary strand

186
Q

What is a retrovirus?

A

Enveloped, single-stranded RNA viruses in the family Retroviridae

187
Q

What does a retrovirus’s virion usually contain?

A

2 identical RNA molecules

188
Q

What enzyme do retroviruses carry?

A

Reverse transcriptase

189
Q

What does reverse transcriptase do?

A

It synthesizes DNA from ssRNA.

190
Q

What happens to the DNA synthesized by reverse transcriptase? Why does it make it difficult for retroviruses to be treated?

A

It is integrated into the host cell genome, where it is replicated and transcribed as if it were the host cell’s DNA

The infected cell must be killed

191
Q

What is a common retrovirus?

A

HIV

192
Q

What cells can viruses infect?

A

Only a specific set of cells, because they must bind to specific host cell receptors

193
Q

What happens when the virus binds the correct receptors?

A

The virus and cell are brought close together

194
Q

How does the virion of an enveloped virus enter the host cell?

A

The virus fuses with the plasma membrane of the host cell

195
Q

What can a host cell sometimes do to a virion bound to its membrane?

A

It may mistake it for nutritients and endocytose the virus

196
Q

What happens after a cell is infected by a virus?

A

The genetic material is translocated to the correct location in the cell in order to be properly transcribed and translated

197
Q

Where do most DNA viruses go after infecting bacteria?

A

Most go to the nucleus to be transcribed into mRNA, which then goes to the cytoplasm to be translated into proteins

198
Q

Where does positive-sense RNA viral genetic material go after infection?

A

Stays in the cytoplasm to be directly translated into protein by host cell ribosomes

199
Q

Where do negative sense RNA viruses go?

A

They synthesize a complementary RNA strand using RNA replicase, which is then translated to form proteins

200
Q

Where does DNA formed through reverse transcription in retroviruses go after infecting bacteria?

A

To the nucleus, to be integrated into the host genome

201
Q

What are common types of proteins that viral RNA is translated into?

A

Structural capsid proteins that allow for the creation of new virions in the cytoplasm in the host cell

202
Q

What happens once the viral genome has been replicated in the bacterial host cell?

A

It is repackaged within the capsid in its original form (meaning if it came as ssRNA, for example, it must return as ssRNA)

203
Q

What are 3 ways in which viral progeny can be released?

A
  • Viral invasion can initiate cell death, which results in spilling of progeny
  • The host cell may simply lyse from having too many virions (unideal for virus, since cell is no longer viable for viral replication)
  • The virus can fuse to the host cell’s plasma membrane in a process called extrusion (ideal, keeps host cell alive for use!)
204
Q

What is it called when a virus can keep using a host cell to replicate?

A

Productive cycle

205
Q

What is the lytic cycle?

A

The bacteriophage maximizes the use of the cell’s machinery with little regard for the survival of the host cell. Once swollen, the cell lyses, and other bacteria can be infected

206
Q

What are viruses in the lytic phase called?

A

Virulent

207
Q

What happens if the virus doesn’t lyse the bacterium? What cycle does this initiate?

A

It may integrate into the host genome as a provirus or prophage, initiating the lysogenic cycle

208
Q

What occurs in the lysogenic cycle?

A

The virus will be replicated as the bacterium reproduces because it’s now a part of the host genome

209
Q

Can the virus de-integrate from the host genome after being incorporated?

A

Yes! Environmental factors can cause the provirus to leave and revert to the lytic cycle

210
Q

What can happen as a provirus leaves the genome?

A

It can extract bacterial genes, allowing transduction of genes from one bacterium to another

211
Q

How can phage integration into the host bacterial genome be beneficial?

A

Infection with 1 strain of phage can make the bacterium less susceptible to superinfection with other phages - may confer an evolutionary advantage

212
Q

What are prions?

A

Infectious proteins that cause disease by trigger misfolding of other proteins

213
Q

What type of misfolding do prions typically cause and what effect does this have on the protein? What lasting effects does this have on the cell?

A

Conversion of a proteion from alpha-helix to beta-sheet, reducing protein solubility and the ability of the cell to degrade the protein, ultimately causing protein aggregation, which interferes with cell function

214
Q

What are viroids?

A

Small pathogens consisting of a very short circular ssRNA that infect plants (some can be found in humans, like HDV)

215
Q

What do viroids do?

A

they can bind to a large number of RNA sequences and can silence genes in the plant genome, preventing protein synthesis and disrupting metabolism and causing structural damage

mcat biology (12 decks)

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