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chapter 2 Flashcards

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1
Q

what are the 3 components of the cell theory?

A
  1. all living organisms are composed of one or more cells
  2. the cell is the most basic unit of life
  3. all cells arise only from pre-existing cells
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2
Q

Eukaryotes are defined by 3 major structural/functional features?

A
  • presence of a membrane bound nucleus
  • organelles
  • mitotic division
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3
Q

which eukaryotic cells do not have a membrane bound nucleus?

A
  • red blood cells (erythrocytes) - do not contain nuclei
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4
Q

the basic function of the nucleus is to compartmentalize and store genetic information, which is encoded in DNA in the form of?

A
  • linear chromosomes
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5
Q

what is the nuclear membrane?

A
  • AKA the nuclear envelope, is a double membrane composed of 2 sets of phospholipid bilayers
  • smaller molecules such as ions and fluids can simply diffuse through the membrane
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6
Q

what are nuclear pores?

A
  • protein complexes that cross the nuclear membrane and allow the selective transport of larger molecules (>50 kDa) into and out of the nucleus
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7
Q

what is the nucleolus responsible for?

A
  • ribosome assembly
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8
Q

How is the cytoplasm defined?

A
  • as everything else within a living cell besides the nucleus and external membrane
    • includes all other organelles and the cytosol (dens, gel-like, aqueous solution that comprises the liquid found inside cells)
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9
Q

The citric acid cycle, beta oxidation of fatty acids and oxidative phosphorylation take place where?

A
  • in the mitochondria
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10
Q

what is the structure and function of the mitochondria?

A
  • mitochondira are seperated from the rest of the cytoplasm by 2 membranes which are composed of a phospholipid bilayer
  • the mitochondrial matrix is the site of the citric acid cycle
  • oxidative phosphorylation takes places in the inner membrane
  • contain mitochondrial DNA which is only inherited from the mother
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11
Q

what are lysosomes?

A
  • the garbage disposal system of the cell
    • material from outside the cell enters into the lysosome through endocytosis while material from inside the cell enters through autophagy
  • membrane bound vesicles that contain a diverse range of enzymes that hydrolyze various polyerms
  • operate best at acidic pH levels (4.4-5)
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12
Q

what is the endoplasmic reticulum?

A
  • net-like organelle that extends out from the nuclear membrane
    • split into the rough and smooth ER
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13
Q

what is the rough ER?

A
  • covered with ribosomes whcih are the site of protein synthesis
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14
Q

what is the smooth ER?

A
  • does not have ribosomes
  • involved in lipid metabolism (synthesis and breakdown), production of steroid hormones, and detoxification
    • produces the phospholipid components throughout the cell
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15
Q

what is the Golgi apparatus?

A
  • modifies and packages proteins into membrane bound vesicles that are sent to the ultimate destination of the proteins
  • composed of cisternae
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16
Q

what are peroxisomes?

A
  • peroxides (such as hydrogen peroxide H2O2) accumulate in the peroxisomes
    • play a role in the metabolism of very-long chain lipids by breaking them down to medium-chain lipids that are transported to mitochondria for further processing
    • also play a role in the detoxification of substances such as ethanol
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17
Q

what is the cytoskeleton?

A
  • what provides structural support to a cell and helps it move
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18
Q

what are the major components of the cytoskeleton?

A
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19
Q

what are microfilaments?

A
  • composed of 2 strands of actin polymers and play a role in cell motilit and endo/exocytosis
  • contribute to the process of cell cleavage during division and to the ability of cells to contract
  • the actin components of microfilaments also interact with myosin as part of muscle contraction
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20
Q

what are microtubules?

A
  • composed of dimers of proteins known as alpha-tubulin and beta-tubulin
  • help maintain the structure of the cell and make up cilia and flagella
  • also help facilitate intracellular transport and make up mitotic spindles, which play a role in chromosome seperation during mitosis and meiosis
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21
Q

what are intermediate filaments?

A
  • constitute a broad category of protiens that provide structural support and are involved in cellular adhesion processes
  • keratin is a well known example
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22
Q

what are centrioles?

A
  • cylindrical structures made up of tubulin that help organize the mitotic spindle and are an important constituent of the centrosome, which is the major microtubule organizing center within the cell
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23
Q

what is flagella?

A
  • a structure involved in cell motility that are formed from the microtubule
  • tail-like appendages that protrude from a cell and allow it to move, although they can serve as sensory appendages
  • found in both eukaryotes and prokaryotes with difference in structure
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24
Q

what is cilia?

A
  • a structure involved in cell motility that are formed from the microtubule
  • relatively small projections that help move substances along the cell surface
  • ex. in the respiratory tract to help move mucus out of the lungs
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25
Q

In eukaryotes, both cilia and flagella are characterized by?

A
  • 9 + 2 structure in which an outer ring of nine pairs of microtubules surrounds an innter ring of 2 microtubules
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26
Q

what is the difference between eukaryotic and prokaryotic flagella?

A
  • eukaryotic flagella flap back and forth and their movement is powered by ATP
  • prokaryotic flagella use rotary motion, powered by a proton gradient and are composed of flagellin
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27
Q

what is the plasma membrane?

A
  • the plasma membrane of a cell separates the cell from the extracellular environment surrounding it, and therefore is critical for maintaining cellular integrity and for mediating communication of a cell with its surroundings
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28
Q

what is the plasma membrane primarily composed of?

A
  • composed of lipids and proteins
    • defined by presence of lipid bilayer (phospholipids)
    • sphingolipids
    • cholesterol
    • waxes (in some plants)
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29
Q

how is the plasma membrane often described?

A
  • in terms of the fluid mosaic model
30
Q

what does the fluid mosaic model of the plasma membrane contain in addition to the phospholipid bilayer?

A
  • lipid rafts (cholesterol and sphingomyelins)- fluidity control
  • embedded protains
  • membrane-associated proteins- held together by non-covalent interactions with other structures present on the surface of the p.m.
  • many different types of transmembrane proteins
31
Q

what is the cell cycle?

A
  • describes the rhythm of a cell’s life cycle through the phases of division
32
Q

what are the parts of the cell cycle?

A
  • resting phase (G0) where nothing really happens and some cells remain here for long periods of time
  • interphase- when the cell prepares for division and can take up 90% of the time of the cell cycle
    • 2 major things occur: growth and DNA replication
      • G1- the cell grows
        • G1 checkpoint/restriction point is when a cell commits to division. DNA damage or other factors can stop a cell from further division
      • S- DNA is replicated
      • G2-cell grows more
        • G2 checkpoont takes place before cell division and checks for DNA damage after replication and pauses if there is until it’s repaired
  • throughout interpahse, chromait is loosely packed (euchromatin) to allow transcription and replication
    • then mitosis occurs
33
Q

what are the phases of cell division/mitosis and their functions

A
  • prophase
    • prepares the cell to go through mitosis so the DNA is condensed so distinct chromosomes become visible as sister chromatids joined st the centromere. The kinetochose assembles on the centromere and is the site where microtubule fibers attach to pull the chromatids apart in later syages
    • asters extend from the centrosome to anchor the cell membrane
    • perperation of the rest of the structures involved in mitosis
    • nuclear envelope and nucleus disappear and mitotic spindle forms
  • metaphase
    • chromosomes line up at the middle of the cell along the metaphase plate
    • has a final cell checkpoint that makes sure the kinetochores are attached properly to the microtubules of the mitotic spindle (prevents improper separation)
  • anaphase
    • the sister chromatids are separated and pulled to opposite sides of the cell by shortening of the microtubules attached to the kinetochores. each side of the cell should have a complete set of chromosomes
  • telophase
    • opposite of prophase
    • a new nuclear envelope appears around each set of chromosomes and a nucleolus reappears within each of those nuclei
  • the process of mitosis is completed by cytokinesis
34
Q

What is meiosis?

A
  • a form of cell division that is essential for sexual reproduction
  • takes place in germ cells
    • in humans, meiosis can be subdivided into spermatogenesis and oogenesis
35
Q

meiosis differs from mitosis in that?

A
  • it results in the formation of 4 daughter cells, each of which has only one copy of each chromosome (haploid, n) in contrast to mitosis which generates cells with two copies of each chromosome (diploid, 2n) that are essentially identical to their parent cell
  • these daughter cells are known as gametes and 2 haploid cells fuse to form a zygote which is different from its parents
36
Q

How many stages does meiosis go through?

A

2

  • meiosis 1 and meiosis 2
37
Q

describe meiosis 1 and meiosis 2

A
  • the first round of division and results in the formation of 2 haploid daighter cells that contain duplicate sister chromatids
    • in prophase 1, homologous chromosomes pair up with eachother in a process known as synpasis, forming tetrads. while paired up, homologous chromosomes may exchange geentic information in a process called crossing over
      • the crossing over points are known as chiasmata and this process results in recombinant DNA
    • metaphase 1, homologous pairs line up at the metaphase plate in the form of tetrads (randomly)
    • anaphase 1, the homologous pairs are separated and each pulled to one side of the cell (when cell goes from diploid to haploid) but each individual member of the homologous pair still has 2 chromatids
  • meiosis 2 is essentially the same as mitosis but the sister chromatids are split up into 2 haploid daughter cells
38
Q

what are prokaryotes?

A
  • the oldest form of cellular life, have tremendous effects, both good and bad on human health
  • defined by the absence of a nucleus and membrane-bound organelles, and are classified into 2 domains of life: bacteria and archaea
39
Q

what are archaea?

A
  • unicellular organisms that have been traditionally known as extremophiles, capable of inhaviting environments with high salinity or extreme temperatures
  • the in between of eukaryotes and prokaryotes
  • use a broad range of energy sources
40
Q

what is bacteria?

A
  • ubiquitous
  • bacteria can be commensal, mutualistic or parasitic (pathogens)
41
Q

what are the shapes of bacteria?

A
  • cocci (spherical)
  • bacilli (rod-shaped)
  • spirilli (spiral shaped)
42
Q

bacteria that do not require oxygen for metabolism are called?

A
  • anaerobes
    • obligate- oxygen is toxic
    • aerotolerant- cannot engage in aerobic metabolism but oxygen is not toxic for them
    • facultative- can engage in either aerobic or anaerobic metabolism
    • obligate aerobes- depend on oxygen to survive
43
Q

Unlike eukaryotes, prokaryotes have?

A
  • a cell wall that encloses a cell membrane which is known as peptidoglycan which provides structural support for bacteria in a range of environments
44
Q

How are the 2 main types of bacterial cell walls that contain different quantities of peptidoglycan differentiated?

A
  • gram staining
45
Q

what are the steps of gram staining?

A
  1. crystal violet is applied as a primary stain to heat-fixed bacteria
  2. iodide is added. iodide binds to the crystal violet stain and traps it within the peptidoglycan layer
  3. an ethanol or acetone wash is applied. this washes away the lipopolysaccharide membrane of the gram-negative bacteria and allows the crystal violet iodide complexes to be washed away as well
  4. safranin is applied as a counterstain to visualize gram-negative cells as pink (otherwise they would be unstained)
46
Q

after gram staining what colours are seen?

A
  • gram-positive cells are a deep purple (thick peptidoglycan layer)
  • gram-negative cells are pink (thin peptidoglycan layer surrounded by a lipopolysaccharide outer membrane)
47
Q

what are 2 facts about gram-negative bacteria?

A
  • generally gram-negative bacteria are not susceptible to antiobiotics such as penicillin that target the peptidoglycan cross linking but specific antiobiotics exist that target gram-negative bactera
  • the lipopolysaccharide membrane of gram-negative bacteria can induce an innate immune repsonse in humans causing inflammation and complicating the course of treatment
48
Q

prokaryotes use what for aerobic respiration?

A
  • the cell membrane as they do not have separate mitcohondria
49
Q

what are prokaryotic ribosomes?

A
  • have a 30S and 50S subunit creating a 70S ribosome compared to 40S and 60S making an 80S subunit in eukaryotes
50
Q

What is bacterial flagella?

A
  • used for movement
  • 3 components: flagellin, the basal body and the hook
    • movement in response to chemical signals is known as chemotaxis
51
Q

where is genetic material stored in porkaryotes since they do not have a nucleus?

A
  • contained in a single circular chromome that tends to congregate in a region of the cell known as the nucleoid region
  • can carry out transcription and translation simultaneously
  • prokaryotes often contain small circular DNA known as plasmids
52
Q

plasmids code for?

A
  • virulence factors which refers to anything that allows bacterial infection to be more virulent/harmful to the host
53
Q

how do bacteria reproduce?

A
  • through binary fission
54
Q

what are the steps of binary fission?

A
  • replication in whcih the chromosome is duplicated while the cell grows
  • segregstion and growth of a new cell wall in which the chromosomes are pulled towards different sides of the cell and the cell envelope begins to grow towards the middle of the cell
  • seperation of 2 daughter cells
55
Q

binary fission can take place very quickly and is shown on?

A
  • the bacterial growth curve
    • lag phase- when bacteria are introduced to a new environment and adapt to it
    • log phase- grow exponentially
    • stationary phase- the environment stops being able to sustain exponential growth and growth stops
    • death phase- resources in environment are exhausted so the bacteria die
56
Q

bacteria have the ability to engage in?

A
  • bacterial gene transfer
    • a way to compensate for the fact that binary fission excludes any genetic variability except for what is introduced by chance
57
Q

bacterial gene transfers in which 3 ways?

A
  • transformation
  • transduction
  • conjugation
58
Q

what is transformation?

A
  • refers to the ability of some bacteria to absorb genetic material directly from the environment
59
Q

what is transduction?

A
  • virus-mediated gene transfer
  • the lack of nuclei in bacteria make it relatively east for viruses that infect bacteria (bacteriophages) to incorporate part of the bacterial genome during assembly
  • bacteriophages then infect another bacterial cell, taking the genetic material from a previous cell because it became integrated into the genome after infection
60
Q

what is conjugation?

A
  • the bacterial equivalent of sexual reproduction and involves the transfer of a plamid through a bridge that is created when a sex pilus of one bacterium (F+) attaches to another bacterium (F-) and the fertility factor is duplicated and transferred creating a new F+ cell
61
Q

what are viruses?

A
  • obligate intracellular parasites
  • have genetic material and a protein coat known as a capsid
  • some also have an envelope made up of phospholipids and proteins (easily destroyed)
62
Q

what is a virion?

A
  • used specfically to refer to the fully-assembled,infectious virus
63
Q

the genetic material of viruses can be in the form of?

A
  • single-stranded or double-stranded DNA or RNA
64
Q

what are positive sense RNA viruses?

A
  • containing RNA that can immediately be translated by the cell
65
Q

what are negative sense RNA viruses?

A
  • contain RNA that is complementary to mRNA, meaning the mRNA must be synthesized by an enzyme known as RNA replicase that is carried in the virion
66
Q

what are bacteriophages?

A
  • virsues whose host cells are bacteria
  • must inject their genetic material into their host cell through a syringe-like structure known as a tail sheath as they do not enter the cell completely
67
Q

what are retroviruses?

A
  • a distinct class of single-stranded RNA viruses
  • use an enzyme called reverse transcriptase to synthesize DNA from their RNA genome. this DNA is then incorporated into the genome of the host cell
  • ex HIV/AIDS
68
Q

what is the life cycle of a virus?

A
  • depends largely on its genetic material
  • the basic goal of a virus is to reporudce by ensuring that its protein-coding genes are expressed
  • RNA viruses can accomplish this in the cytoplasm while DNA viruses are transported to the nucleus for mRNA to be synthesized. viral genome must also be replicated
  • using the machinery of the host cell, new virions are packaged and released through a process called extrusion or the quantity of virions can be so large that the cell lyses and it spills into the environment
69
Q

bacteriphages have 2 distinct life cycles:

A
  • lytic cycle- the bacteriophage works hard to replicate at full speed, making full use of the cells machinery and fills the cell up to a point where it bursts
  • lysogenic cycle- a bacteriophage can integrate itself into the host genome, at which point it is known as a prophage/provirus and in response to environmental signals, the prophage can re-emerge from the host genome and resume the lytic cycle
70
Q

what are prions?

A
  • infectious proteins
    • misfolded proteins that cause other proteins to become misfolded as well
    • ex. Creutzfeldt-Jakob disease
71
Q

what are viroids?

A
  • small infectious particles found in plants that can silence gene expression by binding to specific RNA sequences
72
Q
A

MCAT biology (12 decks)

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