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mcat: bio > chapter 1: the cell > Flashcards

chapter 1: the cell Flashcards

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1
Q

what are the three tenets the cell theory consist of?

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
  4. cells carry genetic info in the form of DNA. This genetic material is passed on from parent to daughter cell.
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2
Q

what are the properties of eukaryotic cells?

A
  • can be multicellular or unicellular eukaryotic organisms
  • eukaryotic cells contain a true nucleus enclosed in a membrane
  • most organelles are membrane bound, allowing for compartmentalization of functions
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3
Q

what are the properties of prokaryotic cells?

A
  • always single celled prokaryotic organisms
  • prokaryotic cells do not contain any membrane-bound organelles
  • genetic material is organized into a single circular molecule of DNA concentrated in the nucleoid region
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4
Q

describe the membrane properties of eukaryotic organelles.

A

most organelles in eukaryotes are membrane bound.

membranes of eukaryotic cells consist of a phospholipid bilayer, where the surface is hydrophilic and electrostatically interacts with the aqueous environment inside and outside the cell, and the inner proportion is hydrophobic. This helps provide a highly selective barrier between the interior of the cell and the external environment.

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5
Q

what does the cytosol in membrane bound organelles allow for?

A

it allows for the diffusion of molecules through the cell

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6
Q

what does the nucleus store? explain its properties.

A
  • the nucleus encodes genetical material (DNA) for replication, which is organized into chromosomes
  • the nucleus is surrounded by the nuclear envelope (aka nuclear membrane), which is a double membrane that maintains a nuclear environment separate and distinct from the cytoplasm.
  • nuclear pores in the nuclear membrane allow selective two-way exchange of material between the cytoplasm and the nucleus.
  • the genetic material (DNA) contains coding regions called genes. Linear DNA is wound around histones, and it is then further wound into linear strands called chromosomes
  • the nucleus also contains the nucleolus, where ribosomal RNA (rRNA) is synthesized
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7
Q

what is the main function of the nucleolus?

A

ribosomal RNA synthesis

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8
Q

explain the parts of the mitrochondria.

A
  • outer membrane: serves as a barrier between cytosol and the inner environment of the mitochondria
  • inner membrane: arranged into cristae (infoldings); contains the molecules and enzymes of the electron transport chain; cristae increase the surface area available for electron transport chain
  • intermembrane space: space between the inner and outer membranes
  • mitochondrial matrix: the space inside. the inner membrane; the pumping of protons from the mitochondrial matrix to the intermembrane space establishes a proton-motive force; protons ultimately flow through ATP synthase to generate ATP during oxidative phosphorylation
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9
Q

describe mitochondrial DNA.

A

circular

self replicating

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10
Q

how are mitochondria unique from other cells?

A

they are semi-autonomous

they contain some of their own genes and replicate independently of the nucleus via binary fission

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11
Q

What is cytoplasmic or extranuclear inheritence?

A

the transmission of genetic material independent of the nucleus

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12
Q

what are some functions of the mitochondria?

A
  • keeping cell alive by providing energy
  • capable of killing the cell by release of a certain enzyme (cytochrome c i think) that triggers apoptosis
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13
Q

what are lysosomes?

A

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

often function in conjunction with endosomes

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14
Q

what are endosomes?

A

endosomes transport, package, and sort cell material traveling to and from the membrane

they are capable of transporting material to the trans-golgi, to the cell membrane, or to the lysosomal pathway for degradation

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15
Q

what is autolysis?

A

when lysosomes release their hydrolytic enzymes

this leads to the degradation of cellular components

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16
Q

what is the endoplasmic reticulum?

A

the ER is a series of interconnected membranes that are actually contiguous with the nuclear envelope

the double membrane of the ER is folded into numerous invaginations, creating complex structures with a central lumen

two types: rough and smooth ER

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17
Q

what is the rough ER? its function?

A
  • the rough ER is studded with ribosomes, which permit the translation or proteins destined for secretion directly into its lumen
  • rough ER synthesizes proteins destine for secretion
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18
Q

are ribosomes surrounded by a membrane?

A
  • ribosomes are found in both eukaryotes and prokaryotes
  • prokaryotes do not have any membrane-bound organelles, thus ribosomes are membrane bound
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19
Q

what is the smooth ER?

A

the smooth ER lacks ribosomes and it utilized primarily for lipid synthesis and detoxification of certain drugs and points

the smooth ER also transports proteins from the rough ER to the Golgi apparatus

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20
Q

what is the Golgi apparatus?

A
  • the Golgi apparatus consists of stacked membrane-bound sacs.
  • materials from the ER are transferred to the Golgi in vesicles
  • once inside the Golgi, cellular products may be modified by the addition of groups like carbohydrates, phosphates, and sulfates
  • Golgi may also modify cellular products through the introduction of signal sequences, which direct the delivery of the product to a specific cellular location
  • after the modification and sorting in the Golgi, cellular products are repacked into vesicles, which are then directed to the correct cellular location
  • if product is destined for secretion, the secretory vesicle merges with the cell membrane and its contents are released via exocytosis
  • packages, modifies, and distributes cellular products
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21
Q

what are peroxisomes?

A

peroxisomes contain hydrogen peroxide

one primary function is the breakdown of very long fatty acid chains via beta-oxidation

peroxisomes participate in the synthesis of phospholipids and contain some enzymes involved in the pentose phosphate chain

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22
Q

what is the cytoskeleton, and what are its three components?

A
  • provides structure to the cell and helps it to maintain its shape
  • provides a conduit for the transport of material around the cell
  • three components: microfilaments, microtubules, and intermediate filaments
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23
Q

what properties do actin filaments have that make it helpful in microtubules?

A
  • actin filaments are organized into bundles and networks, and they are resistant to compression and fracture, which helps provide protection for the cell
  • actin filaments also use ATP to generate force for movement by interacting with myosin
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24
Q

what are microfilaments made up?

A

microfilaments are made up of solid polymerized rods of actin

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25
Q

what roles do microfilaments have?

A
  • microfilaments play a role in cytokinesis (the division of materials between daughter cells)
  • during mitosis, the cleave furrow is formed from microfilaments, which organize a ring at the site of division between the two new daughter cells. as the actin filaments within this ring contract, the ring becomes smaller, eventually pinching off the connection between the two daughter cells
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26
Q

what is the structure of a microtubule?

A

microtubules are hollow polymers of tubulin protein

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27
Q

what are cilia and flagella composed of?

A

microtubules

28
Q

what are cilia?

A

cilia are projections from a cell that are primarily involved with the movement of materials along the surface of the cell

present only in eukaryotic cells

example: movement of mucus

29
Q

what are flagella?

A

flagella are structures involved in the movement of the cell itself, such as the movement of sperm cells throughout the reproductive tract

present in eukaryotic and prokaryotic cells

30
Q

what does the “9+2 structure” refer to?

A

the structure of cilia and flagella

only seen in eukaryotic cells

cilia and flagella are both composed of 9 pair of microtubules forming an outer ring, with two microtubules in the center

31
Q

what are centrioles and where are they found?

A

centrioles are found in the centrosome

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

during mitosis, the centrioles migrate to opposite poles of the dividing cell and organize the mitotic spindle

the microtubules emanating from the centrioles attach to the chromosomes via kinetochores and exert force on the sister chromatids, pulling them apart

32
Q

what are intermediate filaments? what are their purposes?

A
  • intermediate filaments are a diverse group of filamentous proteins, which includes: keratin, desmin, vimentin, and lamins

purposes:

  • many IFs are involved in cell-cell adhesion or maintenance of the overall integrity of the cytoskeleton
  • IFs are able to withstand a tremendous amount of tension, increasing the structural rigidity of the cell.
  • IFs help anchor organelles, including the nucleus
33
Q

what are the four types of tissues?

A
  1. epithelial tissue
  2. connective tissue
  3. muscle tissue
  4. nervous tissue
34
Q

what are the purposes/functions of epithelial tissue?

A
  • epithelial tissues cover the body and line its cavities, providing a means for protection against pathogen invasion and desiccation
  • involved in absorption, secretion, and sensation
  • to remain as one cohesive unit, epithelial cells are tightly joined to each other and to an underlying layer of connective tissue known as the basement membrane
  • in most organs, epithelial tissues constitute the parenchyma (the functional parts of the organ)
  • ET are often polarized; one side faces the lumen (hollow inside of an organ/tube) or outside world, while the other side interacts with underlying blood vessels and structural cells
35
Q

what are the different classifications of epithelia?

A

based on layers:

simple epithelia: have one layer of cells

stratified epithelia: have multiple layers

pseudostratified epithelia: appear to have multiple layers due to differences in cell height, but actually is one layer

based on shape:

cuboidal, columnar, squamous (flat and scale-like)

36
Q

what is the function of connective tissue? what are examples of connective tissue?

A
  • supports the body and provides framework for the epithelial cells to carry out their functions
  • main contributors to the stroma (support structure) of an organism
  • most cells in connective tissue produce and secrete materials such as collagen and elastin to form the extracellular matrix
  • examples: bone, cartilage, tendons, ligaments, adipose tissue (body fat), blood
37
Q

what are the three domains that classify life? which of those contain prokaryotes?

A
  • archaea (contain prokaryotes)
  • bacteria (contain prokaryotes)
  • eukarya
38
Q

explain the characteristics of archaea.

A
  • single-celled organisms and visually similar to bacteria
  • contain genes and several metabolic pathways that are more similar to eukaryotes
  • able to use alternative sources of energy; some of photosynthetic, many of chemosynthetic and can generate energy from inorganic compounds (including sulfur and nitrogen based compounds like ammonia)
  • contain a single circular chromosome
  • divide by binary fission or budding
  • resistant to many bacteria
39
Q

how are eukaryotes and archaea similar?

A
  • hypothesized that they share a common origin
  • both start translation with methionine
  • contain similar RNA polymerases
  • associate their DNA with histonrs
40
Q

explain the characteristics of bacteria.

A
  • contain a cell membrane and cytoplasm
  • some have flagella or fimbriae (similar to cilia)
  • some bacteria are mutualistic symbiotes (humans and bacteria both benefit)
  • some are pathogens or parasites (bacteria provide no advantage or benefit to the hot, but rather cause disease
41
Q

what are the classifications of bacteria by shape?

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

what are obligate aerobes?

A

bacteria that require oxygen for metabolism

43
Q

what are anaerobes, and what are the different types?

A
  • anaerobes: bacteria that use fermentation, or some other form of cellular metabolism that does not require oxygen
  • obligate anaerobes: cannot survive in oxygen containing environments (presence of oxygen leads to production of reactive oxygen-containing radicals, which lead to cell death)
  • facultative anaerobes: bacteria that can toggle between metabolic processes, using oxygen for aerobic metabolism if it present, and switching to anaerobic metabolism if it is not
  • aerotolerant anaerobes: unable to use oxygen, but not harmed by its presence
44
Q

what is the cell wall, and what is its function?

A
  • cell forms the outer barrier of the cell only in prokaryotes
  • provides structure and controls the movement of solutes into and out of the bacterium; this allows the cell to maintain a concentration gradient relative to the environment
  • may also aid a bacterial pathogen by protecting it from a host organism’s immune system
45
Q

differentiate between gram positive and gram negative cell walls.

A

gram positive

  • consist of a thick layer of peptidoglycan (a polymeric substance made from amino acids and sugars)
  • also contains lipoteichoic acid

gram negative

  • very thin and also contains peptidoglycan
  • gram negative bacteria also have outer membranes contains phospholipids and lipopolysaccharides (this triggers an immune response in humans)
46
Q

what is the purpose of flagella?

A
  • can be used for movement (propulsion, move toward food, move away from toxins, etc)
47
Q

what are flagella composed of?

A
  • flagella composed of a filament, basal body, and a hook
  • the filament is a hollow, helical structure composed of flagellin
  • the basal body is a complex structure that anchors the flagellum to the cytoplasmic membrane; is also the motor of flagella
    • hook 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 bacterium forward
48
Q

where do prokaryotes concentrate their DNA?

A

prokaryotes concentrate their DNA in the nucleoid region, which does not contain a nuclear envelope

49
Q

do prokaryotes have mitochondria? what does this imapct?

A

no, prokaryotes do not have mitochondria

instead the cell membrane is used for the ETC and generation of ATP

50
Q

do prokaryotes have ribosomes?

A

yes, they are different sizes

prokaryotic ribosomes: 30s and 50s subunits

eukaryotic ribosomes: 40s and 60s subunits

51
Q

what is binary fission?

A
  • binary fission is a simple form 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 midline to produce two identical daughter cells
  • does not produce genetic variability because identical daughter cells are created
52
Q

what is bacterial transformation a result of?

A

it results from the integration of foreign genetic material into the host genome

53
Q

what is conjugation

A
  • conjugation is the bacterial form of mating (sexual reproduction)
  • it involves two cells forming a conjugation bridge between them that facilitates the transfer if genetic material
  • the transfer is unidirectional (from donor male to female recipient)
  • the bridge is made from appendages called sex pili (which are found on the donor male)
54
Q

what is transduction?

A
  • involves a vector (a virus that carries genetic material from one bacterium to another)
    *
55
Q

what are transposons?

A

genetic elements capable of inserting and removing themselves from the genome

56
Q

what are the phases of bacterial growth?

A
  • lag phase: bacteria first adapt to local conditions in a new environment
  • exponential/log phase: rate of division increases as the bacteria adapt, causing an exponential increase in the number of bacteria in the color
  • stationary phase: the reduction of resources slows reproduction
  • death phase: bacteria have exceeded the ability of the environment; marks the depletion of resources
57
Q

what are the three mechanisms of genetic recombination

A
  • transformation
  • conjugation
  • transduction
58
Q

what are viruses composed of?

A

viruses are composed of

  • genetic material
  • a protein coat called the capsid; the capsid can be surrounded by an envelope composed of phospholipids and virus-specific proteins (this envelope is very sensitive to heat, detergents, and desiccation, thus enveloped viruses are easier to kill)
    • viruses w/o an envelope are more resistant to sterilization and are likely to persist on surfaces for an extended period of time
59
Q

why can’t viruses reproduce independently? how do they reproduce?

A
  • viruses lack ribosomes to carry out protein synthesis
  • must hijack host cell’s machinery, then the virus will replicate and produce viral progeny, called virions, which can be released to infect additional cells
60
Q

what are bacteriophages?

what is their process for replication?

what are they composed of?

A
  • viruses that specifically target bacteria
  • they do not enter bacteria; they simply inject their genetic material, leaving the remaining structures outside the infected cell
  • in addition to a capsid, bacteriophages contain a tail sheath (which can act like a syringe injecting genetic material into a bacterium) and tail fibers (which help bacteriophage recognize and connect to the correct host cell)
61
Q

what are three ways viruses release progeny

A
  • viral invasion may initiate cell death, which results in the spilling of the viral progeny
  • host cell may lyse as a result of being filled with a lot of virions
  • a virus can leave the cell by fusing with its plasma membrane; this is known as extrusion
    • this process keeps host cell alive, and thus allows for the continued use of the host cell by the virus
    • a virus in this state is said to be in a productive cycle
62
Q

what occurs during a lytic cycle?

A
  • bacteriophages maximize the 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 lyses an other bacteria can be infected
  • viruses in the lytic phase are termed virulent
63
Q

what occurs during the lysogenic cycle?

A
  • in the event that the virus does not lyse the bacterium, the virus may integrate into the host genome as a provirus or prophase, initiating the lysogenic cycle
  • in this case, the virus will be replicated as the bacterium reproduces because it is now a part of the host’s genome
  • environmental factors may cause the provirus to leave the genome and revert to a lytic cycle
  • in lysogenic cycle, virus adds viral DNA to host cell’s genome, where it can remain dormant
64
Q

what is the generic definition of prions and viroids

A

prions and viroids are very small (subviral) particles than can cause disease under certain circumstances

65
Q

what are prions?

A
  • prions are infectious proteins, and thus are nonliving things
  • they cause disease by triggering misfoldings of other proteins, usually through the conversion of a protein from an alpha-helical structure to a beta-pleated sheet
    • this drastically reduces the solubility of the protein, as well as its ability of the cell to degrade the protein
  • eventually, the proteins aggregate, interfering will cell function
66
Q

what are viroids?

A
  • viroids are small pathogens consisting of a very short circular single-stranded RNA (ssRNA) that infect plants
  • can bind to large number of RNA sequences and can silence genes in plant genome, resulting in the incorrect synthesis of necessary proteins
    • this results in metabolic disruption and damage to the cell
      *
67
Q

which types of nucleic acid can form the genome of a virus?

A

the nucleic acid can be either DNA or RNA

in both cases, can be single or double stranded

mcat: bio (12 decks)

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