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Biology Flashcards

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1
Q

What are the tenets of the cell theory?

A
  • All living things are composed of cells
  • The cell is the basic functional unit of life
  • Cells only arise from preexisting cells
  • Cells carry genetic information in the form of DNA; this genetic material is passed on from parent to daughter cell
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2
Q

What are nuclear pores?

A
  • Pores in the nuclear membrane which allow for selective two way excahnge of material between the cytoplasm and the nucleus
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3
Q

What is the function of the smooth ER?

A
  • Utilized primarily for lipid synthesis and the detoxification of certain drugs and poisons
  • also transports proteins from the RER to the golgi
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4
Q

What are peroxisomes?

A
  • An organelle which ontains hydrogen peroxide
  • Primary function: to break down of very long chain fatty acids via β-oxidation
  • Participate also in the syntehsis of phospholipids and contain some enzymes involved in the pentose phosphate pathway
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5
Q

What is a clevage furrow?

A
  • Formed from microfilaments during mitosis
  • Microfilaments organize as a ring at the site of the division between the 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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6
Q

Which motor proteins utilize microtubules as their primary pathways?

A
  • Kinesin and dynein
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7
Q

What is the 9+2 structure?

A

A eukaryotic flagellum is a bundle of nine fused pairs of microtubule doublets surrounding two central single microtubules.

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8
Q

What are centrioles?

A
  • The organizing center for microtubules
  • Structured as nine triplets of microtubules with a hollow center
  • During mitosis, the centriole migrate to opposite poles of the dividing cell and organize the mitotic spindle
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9
Q

What are kinetochores?

A

A kinetochore is a disc-shaped protein structure, found at the centromere of a chromatid, to which microtubules attach during cell division.

  • Microtubules eminating from the centrioles attach to the chromosomes via kinetochores and can exert a force on sister chromatids, pulling them apart
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10
Q

What is psuedostratified epithelia?

A
  • Appear to have multiple layers, but in reality have only one layer of cells
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11
Q

What are archaea?

What are some similarities to eukaryotes? To bacteria?

A
  • Single celled organisms that are visually similar to bacteria, but contain genes and several metabolic pathways that are more similar to eukaryotes
  • Notable for their ability to use alternative energy sources; some are photosynthetic, but some are chemosynthesis, and generate energy from inorganic compounds (sulfur and nitrogen based bompounds)

Similarites to eukaryotes:

  • Start translation with methionine
  • contain similar RNA polymerases
  • associate their DNA with histones

Similarities to bacteria:

  • single circular chromosome
  • divide by binary fissuion or budding
  • similar structure to bacteria
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12
Q

What are the possible shapes/types of bacteria?

A
  • Cocci: spherical bacteria
  • Bacilli: rod-shaped bacteria
  • Spirilli: spiral shaped bacteria
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13
Q

What are aerotolerant anerobes?

A
  • Unable to use oxygen fo metabolism, but are not harmed by its presence in the environment
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14
Q

What are facultative anaerobes?

A
  • Bacteria which can toggle between metabolic processes, using oxygen for aerobic metabolism when it is present and switiching to anaerobic metabolism if its not
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15
Q

What are obligate anaerobes?

A
  • Anaerobes that cannot surrive in an oxygen-containing environment
  • The presence of oxygen leads to the production of reactive oxygen-containg radicals in these species, which leads to cell death
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16
Q

What makes a bacteria gram-positive?

A
  • Cell wall cosnsits of a thick layer of peptidoglycan, a polymeric substance made from amino acids and sugars
  • Gram negative bacteria have peptidoglycan in their cells walls, but in much smaller amount
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17
Q

What is the filament, basal body and hook of the flagella?

A

- Filament: a hollow, helical structure made up of flagellin

- Hook: connects the filament and the basal body, so as the asal body rotates, it exerts torque on the filament

- Basal body: a complex strucutre that anchors the falgellum to the cytoplasmic membrane and is also the mottor of the flagellum, rotating at up to 300Hz

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18
Q

What are plasmids?

A
  • Small circular strucutres, which are DNA that is acquired from external sources
  • Plasmids are not necessary for survival of the prokaryotes, and therefore not considered part of the genome, but may confer an advantage such as antibiotic resistance
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19
Q

What are the subunits of ribosomes in eukaryotes vs. prokaryotes?

A

Eukaryotes: 40S and 60S

Prokaryotes: 30S and 50S

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20
Q

What is binary fission?

A
  • A simple form of asexual reproduction seen in prokaryotes
  • Circular chromosome attaches to the cell wall and replicates; eventually, the plasma membrane and cell wall because to grow inward along the midline of the cell to produce two identical daugther cells
  • Requires fewer events than mitosis, it can proceed rapidly; some e. coli can divide every 20 minutes
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21
Q

What are episomes?

A

A subset of plasmids that are capable of integrating into the genome of the bacteria

22
Q

With regard to prokaryotes, what is transformation?

A
  • Results from the integration of foregin genetic material into the host genome
  • This foreign genetic material most frequently comes from other bacteria that, upon lysing, spill their contents into the vicinity of a bacterium capable of transformation
23
Q

With regard to prokaryotes, what is conjugation?

A
  • The bacterial form of sexual reproduction
  • Involves two cells forming a conjugation brudge that allows for the transfer of genetic material
  • The transfer is unidirectional from the donor male (+) to the recpient female (-)
24
Q

With regard to prokaryotes, what is transduction?

A
  • The only genetic recombination that requires a vector: a virus that carries genetic material from one bacterium to another
  • Since bacteriophages must replicate in their hosts, they can accidentally trap a segement of host DNA during assembly, and thus, when they infect bacteria, they can transfer host DNA into the bacterial genome
25
Q

What are transposons?

A
  • genetic elements thar are capable of inserting and removing themsvels from the genome
  • Can occur in both prokaryotes and eukaryotes
  • If a transposon is inserted within a coding region of a gene, that gene may be disrupted
26
Q

What are the phases of bacterial growth?

A
  • lag phase: in a new environment, bacteria first adapt to the new local condition
  • exponential phase: as bacteria adapt, growth increases, causing an exponential increase in the number of bacteria in the colonary
  • stationary phase: as the number of bacteria in the colony grows, resources are often reuction; the reudction of resouces slows production
  • death phase: after the bacteria have exceeded the ability of the environment to support the number of bacteria, death occurs
27
Q
A
28
Q

In viruses, what is positive and negative sense RNA?

A
  • Positive sense: implies that the genome may be directly translated to functional proteins by the ribosomes of the host cell, just like mRNA
  • Negative sense: must first take the negative sense trstand and synthesize a complementary strand, which can then be used a s template for protein synthesis
29
Q

What protein is specific to negative-sense RNA viruses?

A
  • RNA replicase: must be carried in the virion to ensure that the complementary strand is synthesized
30
Q

In regard to bacteriophages, what is the lytic cycle? Why is the lysogenic cycle?

A

Lytic

  • Bacteriophage make maximal use of the of the cell’s machinery with little regard for survival of the host cell
  • Once the host is swollen with new virions, the cell lyses, and other bacteria can be infected
  • Bacteria in the lytic phase are termed virulent

Lysogenic:

  • If the event that the virus does not lyse the bacterium, it may integrate into the host genome as a provirus or prophage, beginning the lysogenic cycle
  • In this case, the virus will be replicated as the bacterium reproduces, as it is now a part of the host’s genome
31
Q

Describe the phases of mitosis.

A

Prophase:

  • Condensation of chromatin into chromosomes
  • Centrioles move to opposite poles of the cell
  • Spindle fibers begin to form
  • Nuclear membrane begins to dissolve

Metaphase:

  • kinetochore fibers interact with the fibers of the spindle apparatus and align the chromosomes at the metaphase plate

Anaphase:

  • Centromeres are split so that each chromatid has its own distinct centromere
  • Sister chromatid are pulled to opposite poles of the cell by the shortening of the kinetochore fibers

Telophase:

  • Spindle apparatus disappears
  • Nuclear membrane reofrms
  • Chromosomes uncoil, resuming their interphase form
32
Q

What is the product of meiosis I?

What is the product of meiosis II?

A

Meiosis I: results in homologous chromosomes being separated, resulting in haploid daughter cells

Meiosis II: results in the separation of sister chromatid

33
Q

When does crossing over (genetics) occur?

A

During prophase I of meiosis

34
Q

When does disjunction (genetics) occur? What is disjunction?

A
  • Occurs during anaphase I
  • In disjunction, homologous pairs separate and are pulled to opposite poles of thec ell; during disjuction each chromosome of paternal origin separates or disjoins from its homologue of maternal origin, and either chromosome can end up in either cell
35
Q

Where is sperm produced?

A

Seminiferous tubules

36
Q

What cells nourish sperm?

A
  • Sertoli cells, in the seminiferous tubules
  • Because its main function is to nourish the developing sperm cells through the stages of spermatogenesis, the Sertoli cell has also been called the “mother” or “nurse” cell
37
Q

What are interstitial cells of Leydig?

A

Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone (LH).

38
Q

Where are sperm stored until ejaculation?

A

In the epididymis

39
Q

What is the function of the seminal vesicles?

A
  • Supply fructose to nourish the sperm
  • Along with the prostate gland, give the semenal fluid a mild alkaline property, in order for the sperm to survive in the acidic vaginal tract
40
Q

Describe the stages of spermatogenesis?

A

Spermatogonia

  • replicate their genetic material

Primary spermatocytes: diploid

  • undergo first mitotic division

Secondary spermatocytes: haploid cells

  • undergo meisis to to generate haploid spermatids

Spermatids: haploid

  • undergo maturation to produce spermatozoa

Spermatozoa

41
Q

Describe the hormone changes in the various phases of the menstural cycle

A

Follicular phase

  • In response to the decreased concentrations of estrogen and progesterone at the end of the last cycle, GnRH secretion increases
  • GnRH leads to increass in FSH and LH, which develop several ovarian follicles
  • Follicles produce estrogen, which negatively feedbacks on GnRH, LH and FSH

Ovulation

  • Estrogen levels get so high that it results in positive feedback, and results in a spike of GnRH, LH and FSH
  • LH induces ovulation

Luteal Phase

  • After ovulation, LH causes the ruptured follicle to form the corpus luteum, which secretes progesterone
  • Progesterone maintains the uterine lining for implantation
  • High levels of progesterone negatively feedback on GnRH, LH and FSH in order to prevent ovulation of multiple eggs

Menstration

  • Assuming that implantation does not occur, the corpus luteum loses its stimulation from LH and progesterone begins to decline and the lining is sloughed off
  • The loss of high levels of estrogen and progesterone removes the bock on GnRH so the next cycle begins
42
Q

If implantation of blastocyst occurs, how is the uterine lining maintained?

A
  • The blastocyst will implant into the uterine lining and secrete hCG
  • This hormone is an analog of LH
  • hCG is high in the first trimester, but by the second trimester, the placeta can produce its own progesterone and estrogen
43
Q

In evolution, what are the three types of selection?

A
  • Stabilizing
  • Directional
  • Disruptive
44
Q

What is divergent evolution?

A
  • The indepdent development of dissimilar characteristics in two or more lineages charing a common ancestor
  • Example: cats and seals are both mammals in the order carnivora, yet they differ marketdly in general appearance
45
Q

What is parallel evolution?

A

The process whereby related species evolve in a similar way for a long period of time in response to analogous environmental selection pressures

46
Q

What is convergent evolution?

A

The independent development of similar characteristics in two or more lineages not sharing a recent common ancestor

  • Example: fish and dolphins; resemble one another physically but they are in different classes of vertebrates
47
Q

What is genetic drift?

A
  • Changes in the composition of the gene pool due to chance
  • Tends to be more pronounced in small populations
48
Q

What is the Founder Effect?

A

The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.

  • A type of genetic drift in which a small population of a species finds itself in reproductive isolation from other populations as a result of natural barriers, catastrophic events or bottlenecks
49
Q

Describe the Actin-Myosin Cross-Bridge Cycle

A
50
Q
A

MCAT (8 decks)

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