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Biology Kaplan MCAT > Ch. 1: The Cell > Flashcards

Ch. 1: The Cell Flashcards

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1
Q

Cell Theory

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– it is passed from parent to daughter cell
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2
Q

Eukaryotes

A

membrane bound organelles, nucleus and can form multicellular organisms

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3
Q

Cell Membrane and Membranes of Organelles

A

contain phospholipids which organize to form hydrophilic interior and exterior surfaces w a hydrophobic core

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4
Q

Cytosol

A

Suspends organelles and allows diffusion of molecules throughout the cell

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5
Q

Nucleus

A

Contains linear DNA wound around organizing proteins called histones then is wound/organized into linear strands called chromosomes
- In nucleus allows for compartmentalization of DNA transcription separate from RNA translation

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6
Q

Nuclear Membrane/Envelope

A

Double membrane w nuclear pores for two-way exchange of materials between the nucleus and cytosol; maintains a nuclear environment separate and distinct from cytoplasm

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7
Q

Nuclear Pores

A

In the nuclear membrane, allow selective two-way exchange of material between the cytoplasm and the nucleus

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8
Q

Genes

A

Arrangement of DNA, coding regions

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9
Q

Nucleolus

A

Subsection of the nucleus where ribosomal (rRNA) is synthesized, can be identified as a darker spot in the nucleus, takes up 25% of nucleus volume

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10
Q

Mitochondria

A

Contain an outer and inner membrane
-Outer membrane: forms barrier w cytosol
- Inner membrane: folded into cristae, contains enzymes for the electron transport chain
-Intermembrane space: between the membranes
-Matrix: inside the inner mitochondrial membrane
Can divide independently from nucleus via binary fission (paradigmatic example of cytoplasmic or extranuclear inheritance,

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11
Q

cytoplasmic or extranuclear inheritance

A

The transmission of genetic material independent of the nucleus

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12
Q

Mitochondria triggering apoptosis

A

can trigger apoptosis by releasing mitochondrial enzymes into the cytoplasm (Bax Bcl thing)
- Kidney senses when oxygen is low
- Kidney releases EpO which leads to production of RBCs
- EpO releases Bcl which inhibits Bax
- Bax: forms the pore in mitochondria that releases cytochrome C
which activate caspases (ETC enzymes) which lead to apoptosis

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13
Q

Lysosomes

A

Contain hydrolytic enzymes that can break down substances ingested by endocytosis and cellular waste products. When these enzymes are released, autolysis of the cell can occur

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14
Q

Endosomes

A

Transport, package, and sort cell material travelling to and from the membrane: 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

Endoplasmic Reticulum

A

Series of interconnected membranes and is continuous w nuclear envelope. Double membrane of ER is folded into numerous invaginations, creating complex structures w a central lumen

  • Rough ER: studded w ribosomes which permit translation of proteins destined for secretion (endomembrane sys)
  • Smooth ER: used for lipid synthesis and detoxification
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16
Q

Endomembrane System

A

Endomembrane System: starts at the ER which releases vesicles that go to golgi, where vesicle is sent to its proper place like lysosomes, plasma membrane, blood etc

  • Targeting signal: ~20 amino acids long @ start of polypeptide (N terminal), Used to get protein into SRP to go to the ER, binds to receptor which lets it into lumen of ER
  • Signal Recognition Protein (SRP), binds to targeting signal, pauses translation, Binds to surface of ER
  • When the ribosome/mRNA/targeting protein/SRP complex binds to the surface of ER: SRP comes off, translation continues, polypeptide snakes into lumen of ER via a pore, A polysaccharide is covalently attached to polypeptide coming in (it’s a glycoprotein), Polypeptide starts folding up– HSP90 chaperone there that is helping w/ folding inside, An enzyme chops off targeting signal, Golgi modifies polysaccharide and sends out vesicle w protein to lysosome, cell membrane or back to ER based on a secondary signal on protein
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17
Q

Golgi Apparatus

A

Consists of stacked membrane-bound sacs in which cellular products can be modified, packaged, and directed to specific cellular locations

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18
Q

Peroxisomes

A

Contain hydrogen peroxide and can break down very long chain fatty acids via beta oxidation. They also participate in phospholipid synthesis and the pentose phosphate pathway.

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19
Q

Cytoskeleton (not under organelles):

A

Provides stability and rigidity to the overall structure of the cell while also providing transport pathways for molecules within the cell:

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20
Q

Microfilaments

A

part of cytoskeleton: Composed of actin, provide structural protection for the cell and can cause muscle contraction through interactions with myosin, also help form the cleavage furrow during cytokinesis in mitosis

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21
Q

Microtubules

A

Composed of tubulin (non covalently bonded), create pathways for motor proteins like kinesin and dynein to carry vesicles, contribute to cilia and flagella structures where they are organized into 9 pairs of microtubules in a ring w 2 microtubules at the center (9+2 structure)
- Centrioles: found in centrosomes and are involved in microtubule organization and the mitotic spindle

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22
Q

Cilia vs Flagella

A

Both made of microtubules , cilia move materials along, flagella moves cell itself

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23
Q

Intermediate filaments

A

Involved in cell-cell adhesion or maintenance of the integrity of the cytoskeleton; help anchor organelles, common examples include keratin and desmin

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24
Q

Epithelial Tissues

A

Cover the body and line its cavities, protecting against pathogen invasion and desiccation. Tightly joined to each other and and to an underlying layer of connective tissue known as the basement membrane. Some epithelial cells absorb or secrete substances, or participate in sensation:

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25
Q

Parenchyma

A

Functional parts of the organ, formed of epithelial cells

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26
Q

Epithelial cells

A

often polarized: one side facing a lumen or outside world and the other side facing blood vessels and structural cells

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27
Q

Epithelia classification by layers

A

Simple epithelia: one layer
Stratified epithelia: many layers
Pseudostratified epithelia: appear to have multiple layers bc of differences in cell heights, but actually have only one layer

28
Q

Epithelia classification by shapes of cells

A

Cuboidal cells: cube shaped
Columnar cells: long and narrow
Squamous cells: flat and scalelike

29
Q

Connective Tissues (not part of epithelia):

A

Support the body and provide a framework for epithelial cells: bone, cartilage, tendons, ligaments, adipose tissue, blood

30
Q

Stroma

A

Support structure, formed of connective tissues that secrete materials to form an extracellular matrix

31
Q

Prokaryotes

A

Do not contain membrane-bound organelles; organize their genetic material in a single circular molecule of DNA concentrated in the nucleoid region

32
Q

3 overarching domains of life

A
  1. Archaea: often extremophiles, live in harsh environments (high temp, high salinity, no light), often use alternative sources of energy like chemosynthesis, similarities to both eukaryotes (start translation w methionine, similar RNA polymerases, histones) and bacteria (single circular chromosome, divide by binary fission or budding)
  2. Bacteria: many similar structures to eukaryotes, and have complex relationships w humans including mutualistic symbiosis and pathogenesis
  3. Eukarya: only non-prokaryotic domain
33
Q

Bacteria relationship to humans

A

Mutualistic symbiotes: both humans and bacteria benefit vs Pathogens or parasites

34
Q

Bacteria classification by shape

A
  • Cocci: spherical
  • Bacilli: rod shaped
  • Spirilli: spiral shaped
35
Q

Bacteria classification by metabolic processes

A
  • Obligate aerobes: require oxygen for metabolism
  • Obligate anaerobes: cannot survive in oxygen-containing environments and can only carry out anaerobic metabolism
  • Facultative anaerobes: can survive in environments with or without oxygen and will toggle metabolic processes based on the environment
  • Aerotolerant anaerobes: cannot use oxygen for metabolism, but can survive in an oxygen containing environment
36
Q

Envelope

A

Formed by cell wall and cell membrane of bacteria, together control the movement of solutes into and out of the cell

37
Q

Bacteria classification by Gram staining

A

Color their cell walls turn during Gram staining w crystal violet stain followed by a counterstain w safranin.

  • Gram positive: turn purple, thick cell wall composed of peptidoglycan (polymeric substance made from amino acids and sugars) and lipoteichoic acid (may activate human immune sys)
  • Gram negative bacteria: pink-red, thin cell wall composed of peptidoglycan and an outer membrane containing phospholipids and lipopolysaccharides
38
Q

Bacterial movement:

A

Bacteria may have 1, 2 or many flagella that generate propulsion to move the bacterium toward food or away from immune cells. Bacterial flagella contain a filament composed of flagellin, a basal body that anchors and rotates the flagellum and a hook that connects the two

39
Q

Chemotaxis

A

moving in response to chemical stimuli

40
Q

Motion by flagella

A

Composed of a filament, a basal body, and a hook:

  • filament: hollow helical structure composed of flagellin
  • basal body: complex structure that anchors the flagellum to the cytoplasmic membrane and is also the motor of the flagellum
  • hook: connects the filament and basal body so that as the basal body rotates, it exerts torque on the filament, which can spin and propel the bacterium forward
41
Q

Prokaryotes carry out the electron transport chain using

A

The cell membrane

42
Q

Prokaryotic ribosomes are ______ than eukaryotic ribosomes

A

Smaller than (30S and 50S vs 40S and 60S)

43
Q

Binary fission

A

Method by which prokaryotes multiply, circular chromosome attaches to cell wall and replicates while cell grows in size until cell wall begins to grow inward along the midline of the cell and divides it into two identical daughter cells. Proceeds rapidly, fewer steps than mitosis

44
Q

Plasmids

A

In addition to single circular chromosome in prokaryotes, extrachromosomal material can be carried in plasmids, may contain antibiotic resistance genes or virulence factors

45
Q

Episomes

A

Plasmids that can integrate into the genome

46
Q

Bacterial genetic recombination:

A

Increases bacterial diversity: transformation, conjugation, transduction, transposons

47
Q

Transformation

A

Acquisition of genetic material from the environment, which can be integrated into the bacterial genome

48
Q

Conjugation

A

Transfer of genetic material from one bacterium (+) to another (-) across a conjugation bridge made from appendages called sex pili found on the donor male (+): a plasmid can be transferred from F^+ cell to F^- cells or a portion of the genome can be transferred from an Hfr cell to a recipient.

49
Q

Sex factors

A

To form the pilus bacteria must contain plasmids know as sex factors that contain the necessary genes. Best studied sex factor is the F (fertility factor) in e. Coli bacteria w this plasmid are termed F+ cells without are called F- cells. During conjugation F+ cell replicates its F factor and donates the copy to the recipient converting it to a F+ cell this allows for rapid aquisition of antibiotic resistance or virulence factors throughout a colony

50
Q

Transduction

A

Transfer of genetic material from one bacterium to another using a bacteriophage as a vector

51
Q

Transposons

A

Genetic elements that can insert into or remove themselves from a genome

52
Q

Pattern of bacterial growth

A
  1. Lag phase: bacteria adapt to new local conditions
  2. Exponential (log) phase: growth then increases exponentially
  3. Stationary phase: as resources are reduced, growth levels off
  4. Death phase: as resources become insufficient, bacteria begin to die
53
Q

Capsid

A

Viruses contain genetic material, a protein coat (capsid) and sometimes a lipid containing envelope– viruses without envelope are more resistant to sterilization and are likely to persist on surfaces for an extended period of time

54
Q

Presence of a viral envelope

A

if an envelope is present, it will surround capsid and is composed of phospholipids and virus-specific protein. It is very sensitive to heat, detergents and desiccations so enveloped viruses are easier to kill

55
Q

Host cell

A

Viruses are obligate intracellular parasites, meaning that they cannot survive and replicate outside of a host cell as they dont have the “machinery”: ribosomes for protein synthesis

56
Q

Virions

A

Individual virus particles, viral progeny

57
Q

Bacteriophages

A

Viruses that target bacteria. Contain a tail sheath which injects the genetic material into a bacterium and tail fibers which allow the bacteriophage to attach to the host cell. Remaining structures stay outside of bacterial cell

58
Q

Viral Genomes

A

May be made of various nucleic acids. May be composed of DNA or RNA and may be single or double stranded. Circular or linear. Few genes or several hundred

59
Q

Positive sense virus

A

Single stranded RNA viruses have RNA which can be translated by the host cell– like mRNA

60
Q

Negative Sense virus

A

Single stranded RNA virus which have RNA where a complementary strand must be synthesized using RNA replicase. Complementary strand can be translated. Must carry RNA replicase in the virion

61
Q

Retroviruses

A

Contain a single-stranded RNA genome to which a complementary DNA strand is made using reverse transcriptase. The DNA strand can then be integrated into the genome

62
Q

Ways viruses infect cells

A

Attach to specific receptors and then either fuse with the plasma membrane, get brought in by endocytosis, or inject their genome into the cell

63
Q

Virus Reproduction

A

Replicate and translate genetic material using host cell’s ribosomes, tRNA, amino acids and enzymes

64
Q

Viral progeny release methods

A

Cell death: spilling of viral progeny, lysis as a result of filling w progeny (disadvantage bc virus can no longer use cell for reproduction), or extrusion: keeps cell alive to allow for continued use of the host cell by the virus–productive cycle

65
Q

Life cycles of bacteriophages

A
  1. Lytic cycle: bacteriophage produces massive numbers of new virions until the cell lyses. Bacteria in the lytic phase are termed virulent
  2. Lysogenic cycle: the virus integrates into the host genome as a provirus or a prophage which can then reproduce along with the cell. The provirus then leaves the genome in response to stimulus at some later time and enters the lytic cycle.
66
Q

Prions

A

Infectious proteins that trigger misfolding of other proteins usually converting alpha helical structure into beta pleated sheet decreasing the solubility and degradability of the misfolded protein

67
Q

Viroids

A

Plant pathogens that are small circles of complementary RNA that can turn off genes, resulting in metabolic and structural derangements of the cell and–potentially–cell death

Biology Kaplan MCAT (12 decks)

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