The Cell Flashcards
(143 cards)
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
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
3
Q
Who and when was the first to view a living cells under a microscope?
A
In 1674, Anton van Leeuwenhoek
4
Q
What was the scientific contribution of Rudolph Virchow?
A
In 1850, demonstrated that diseased cells could arise out of normal cells
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
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
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
8
Q
Each cell has a membrane enclosing a semifluid______________in which organelles are suspended
A
Cytosol
9
Q
How eukaryotic cells reproduce?
A
By mitosis
10
Q
What is the function of cytosol?
A
Allows for diffusion of molecules throughout the cell
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
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
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
14
Q
What are histones?
A
Organizing proteins which linear DNA is wound around
15
Q
Where is the rRNA(ribosomal RNA) synthesized?
A
In the nucleolus (a subsection of the RNA)
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
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
18
Q
What is the mitochondrial intermembrane space ?
A
The space between the mitochondrial membranes
19
Q
What is the mitochondrial matrix?
A
The space inside the inner membrane
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
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
22
Q
What is cytoplasmic/extranuclear inheritance? Give an example
A
Example-mitochondria
Inheritance independent of the nucleus
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
24
Q
What is autolysis?
A
When lysosomes release enzymes it is autolysis
Like the mitochondria, it causes apoptosis
25
What is the endoplasmic reticulum?
A series of interconnected membrane that are actually contiguous with the nuclear envelope
26
What is the rough ER( rER)?
Is studded the ribosomes which permit the translation of proteins destined for secretion directly into its lumen
27
What is the smooth endoplasmic reticulum(SER)?
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
28
What are the functions of the Golgi apparatus?
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
29
What are peroxisomes?
Contain hydrogen peroxide
30
What is the primary function of peroxisomes?
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
31
What are the 3 components of the cytoskeleton?
1. Microfilaments
2. Microtubules
3. Intermediate filaments
32
What are the functions of the cytoskeleton?
Provides structure to the cell and and helps it to maintain shape
Provides a conduit for the transport of materials around the cell
33
Describe microfilaments
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
34
What is cytokinesis?
The division of materials between daughter cells
35
What is the role of microfilaments in in cytokinesis?
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
36
What are cilia?
Projections from a cell primarily involved in movement of materials along the surface of the cell
37
What are microtubules?
Hollow polymers of tubules proteins
38
What are the functions of microtubules?
Provide primary pathways along which the motor proteins like kinds in and dyenein
39
Describe the structure of cilia and flagella
Both have the same structure, composed of nine pairs of microtubules forming an outer ring with two in the center(9+2 structure)
40
What are the functions of centrioles?
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
41
Describe intermediate filaments
These are a diverse group of filamentous proteins including keratin, desmin, vimentin and Lamins
42
What are the functions of intermediate filaments?
- involved in cell to cell adhesion
- maintenance if cytoskeleton integrity
- make the cell more rigid
- help anchor other organelles including the nucleus
43
What are the 4 types of tissue?
1. Epithelial tissue
2. Connective tissue
3. Muscle
4. Nervous tissue
44
What are the functions of epithelial tissue?
Provides protection against pathogens
involved in absorption, secretion and sensation
45
What is the basement membrane?
An underlying connective tissue that keeps epithelial tissue together
46
In many organs, epithelial cells constitute the parenchyma, what is this?
The functional parts of the organ
47
Epithelial are said to often be polarized, what does this mean?
One side faces the lumen of the organ interacting with underlying blood vessels while the other side faces the outside world
48
How can epithelial be categorized based on the number of layers they have?
Simple epithelia
Stratified epithelia
Psuedostratified epithelia
49
What are simple epithelia?
Epithelia with one layer of cells
50
What are psuedostratified epithelia?
Appear in multiple layers due to differences in height but in reality is one layer
51
What are stratified epithelia?
Epithelia with multiple layers
52
How can epithelia be categorized according to shape?
Cuboidal-cube shaped
Columnar- long and thin
Squamous-flat and scalelike
53
What is the purpose of connective tissue?
Provides a framework for epithelial cells to carry out their functions
54
Differentiate between connective tissue and epithelial tissue
Epithelial cells contribute to parenchyma of an pan while connective tissue contribute to the stroma of support structure like bone, cartilage, tendons....
55
What 2 domains do prokaryotes fall under?
Archea and bacteria
56
Describe organisms that would be categorized as Archea
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
57
What similarities imply that Archea and eukaryotes share a common ancestor ?
Both eukaryotes and Archea start translation with methionine, contain similar RNA polymerases and associate their DNA with histones.
58
What are some differences between Archea and eukaryota?
Archea contain a single circular chromosome
Archea divide by binary fission
Archea share a similar DNA to bacteria
59
Why are newborns at risk of hemorrhage ?
They are not yet colonized by bacteria which produce vitamin K in the intestines and cannot produce clotting factors
60
What is a mutuslistic symbiotic relationship? Give and example
Both organisms benefit from a relationship
Humans and bacteria in the gut that produce vitamin K and biotin(vitamin B7)
61
Describe how bacteria can be categorized according to shape?
Spherical bacteria- cocci
Rod shaped bacteria- bacilli
Spiral shaped bacteria- spirilli
62
Give an example of a cocci bacteria?
Streptoccocus pyogenes
63
Give an example of a bacilli bacteria
E. coli
64
Give an 3 examples from spilling bacteria and the diseases caused by each
1. Treponema pallium- causes Syphilis
2. Borrelia burgdorferi- causes Lyme diseases
3. Leptospira interrogans- causes Weil’s disease
65
What are obligate aerobes?
Bacteria’s which need oxygen to live
66
What are anaerobes?
Bacteria which uses fermentation or other form of cellular metabolism other than oxygen
67
What are obligate anaerobes?
Bacteria which cannot survive in an oxygen-containing environment
68
Why do obligate anaerobes die in an oxygen containing environment ?
Presence of oxygen leads to the production of reactive oxygen-containing radicals in these species killing them
69
What are facultative anaerobes?
Bacteria can use oxygen for metabolic processes if presence and switch to anaerobic metabolism if oxygen is absence
70
What are aerotolerant anaerobes?
Bacteria unable to use oxygen for metabolism but are not harmed by its presence in the environment
71
Together the celll wall and cell membrane are Calle ....
The envelope
72
What are the 2 types of cell walls in bacteria?
Gram positive
Gram negative
73
What is the function of the cell wall in bacteria?
Cell wall provides structure and controls movement of solutes which allows the cell to maintain concentration gradients relative to the environment
74
Describe the gram staining process
Uses a crystal violet stain followed by a counter stain called safranin
75
How is a gram positive bacteria differentiated from and gram negative bacteria
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
Describe gram positive cell walls
Consists of a thick layer of of peotidoglycan and lipoteichoic acid
77
What is the purpose of lipoteichoic acid in gram positive ?
The function of this acid is unknown in bacteria but in the human immune system may be activated upon exposure to these chemicals
78
What is the purpose peptidoglycan in bacterial cell wall?
Structural and barrier functions and also aids in pathogens to by providing protection from the host immune system
79
How does the antibiotic penicillin work?
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
Describe Gram-negative cell walls
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
What is the drawback of lipopolysaccharides in gram-negative cell walls?
Triggers the immune response in human beings
The inflammatory response to lipopolysaccharides is much stronger than the response to lipoteichoic acid
82
What is peptidoglycan made of?
Polymeric substance made from amino acids and sugars
83
What is chemotaxis?
The ability of a cell to detect chemical stimuli and move toward or away from them
84
Describe the structure of the flagella
Composed of of a filament, basal body and a hook
85
Describe the flagella filament
A hollow helical structure composed of flagellin
86
Describe the basal body of the flagella
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
Describe the hook of the flagella
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
What are plasmids?
Circular structures which carry DNA, possibly acquired from external sources
89
What is the function of plasmids?
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
What is the function of the cell membrane in prokaryotes?
Used for the electron transport chain and ATP
91
Contrast ribosomes in prokaryotes and eukaryotes
Prokaryotes- contain 30S and 50S
Eukaryotes- contain 40S and 60S
92
Describe binary fission
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
Which is faster between mitosis and binary fission? Why?
Binary fission, it has less steps
94
What are virulence factors?
Traits that increase how pathogenic a bacterium is, such as toxin production
These are carried on plasmids
95
What are episomes?
A subset of plasmids that are capable of integrating into the genome of the bacteria
96
What are the bacterial recombination processes?
1. Transformation
2. Conjugation
3. Transduction
97
What is bacterial transformation?
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
What is bacterial conjugation?
The bacterial form of mating
99
Describe bacterial conjugation
Involves 2 cells forming a conjugation bridge between them and transferring genetic material
Transfer is unidirectional, from the male(+) to female(-)
100
How is the conjugate bridge formed in bacterial conjugation?
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
What is the best studied sex factor? How are bacteria which posses it differentiated from those that don’t have it?
F (fertility) factor of E. Coli
When present in plasmid- F+ cells
When absent in plasmin- F- cells
102
What role does the F(fertility) sex factor play in conjugation?
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
Conjugation allows for rapid acquisition of ____________________________________ throughout a colony because other plasmids can be passed through the conjugation bridge
antibiotic acquisition and virulence factors
104
Which genes may be transferred across a conjugation bridge if a sex factor is integrated into its genome?
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
What is high frequency of recombination (Hfr)?
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
What is transduction?
The only genetic recombination process that requires a vector- a virus that carries genetic material from one bacterium to another
107
Viruses are obligate intracellular pathogens, what does this mean?
They can not reproduce outside of a host cell
108
What are bacteriophages?
Viruses that infect bacteria
109
What enables bacteriophages to trap a segment of host DNA during assembly?
Viruses cannot reproduce outside of the host cell(they are obligate intracellular pathogens)
110
What happens a bacteriophage infects a bacteria after trapping a segment of DNA of a previously infected bacteria?
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
What are transposons ?
Genetic elements capable of inserting and removing themselves for the genome
This is in both prokaryotes and eukaryotes
112
What are the 4 phases of bacterial growth in order?
1. Lag phase
2. Exponential phase
3. Stationary phase
4. Death phase
113
Describe the lag phase of bacterial growth
When the bacteria adapts to new local conditions f a new environment
114
Describe the exponential/log phase of bacterial growth
Growth increases as bacteria adapt
115
Describe the stationary phase of bacterial growth
The reduction of resources causes a slowing of reproduction
116
Describe the death phase of bacterial growth
As resources of the environment becomes deleted, the death phase ensues
117
The bacterial growth curve is an example of....
A semi log plot
118
What is the capsid?
The protein coat of the virus
119
What is the function of the viral envelope? Why?
The envelope is sensitive to hear, detergents, desiccation.
This makes the virus easier to kill(those that have)
120
What is the viral envelope?
If present, will consist of phospholipids and virus specific proteins surrounding the capsid
121
Aside from being sensitive, what is another benefit a virus gains by having no envelope?
Viruses with no envelope are more resistant to sterilization and more likely to persist on surfaces
122
Why do viruses require host cells to replicate?
They lack ribosomes to carry out protein synthesis
123
What are virions?
Viral progeny produced when a virus hijacks a cell’s machinery
124
How do bacteriophages infect bacteria?
Bacteriophages inject their genetic material leaving the remaining structures outside the remaining cell
125
What is the function of tail fibers of bacteriophages?
Help the bacteria recognize and connect to the host cell
126
What are the 2 types of viral single stranded RNA?
Positive and negative sense
127
What is a positive sense single stranded viral RNA ?
Implies the genome may be directly translated to functional proteins by the ribosomes of the host cell like mRNA
128
What is negative sense single stranded viral RNA?
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
Negative sense RNA viruses may carry an___________ _________ in the virgin to ensure the complementary strand is synthesized
RNA replicase
130
What are retroviruses ?
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
How do retroviruses infect host cells?
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
HIV is a _____________
Retrovirus
133
Describe the life cycle of HIV
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
Without the proper receptors, a cell is _____________ to a virus
Invisible
135
People with no CCR5 are...
Immmune to HIV
136
Give the various ways viral progeny may be released
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
Why is lysis of a host cell disadvantageous for the virus?
The virus can no longer carry out its life cycle
138
What is the function of extrusion in a viral life cycle ?
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
What types of life cycles may a bacteriophage enter?
Lyric or lysogenic life cycle
140
Describe a lyric cycle of a bacteriophage
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
Bacteria in the lytic phase are termed...
Virulent
142
Describe the lysogenic cycle
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
How does the bacterium benefit from a lysogenic virus?
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
