Biology Flashcards
What are the tenets of the cell theory?
- 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
What are nuclear pores?
- Pores in the nuclear membrane which allow for selective two way excahnge of material between the cytoplasm and the nucleus
What is the function of the smooth ER?
- Utilized primarily for lipid synthesis and the detoxification of certain drugs and poisons
- also transports proteins from the RER to the golgi
What are peroxisomes?
- 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
What is a clevage furrow?
- 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
Which motor proteins utilize microtubules as their primary pathways?
- Kinesin and dynein
What is the 9+2 structure?
A eukaryotic flagellum is a bundle of nine fused pairs of microtubule doublets surrounding two central single microtubules.
What are centrioles?
- 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
What are kinetochores?
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
What is psuedostratified epithelia?
- Appear to have multiple layers, but in reality have only one layer of cells
What are archaea?
What are some similarities to eukaryotes? To bacteria?
- 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
What are the possible shapes/types of bacteria?
- Cocci: spherical bacteria
- Bacilli: rod-shaped bacteria
- Spirilli: spiral shaped bacteria
What are aerotolerant anerobes?
- Unable to use oxygen fo metabolism, but are not harmed by its presence in the environment
What are facultative anaerobes?
- Bacteria which can toggle between metabolic processes, using oxygen for aerobic metabolism when it is present and switiching to anaerobic metabolism if its not
What are obligate anaerobes?
- 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
What makes a bacteria gram-positive?
- 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
What is the filament, basal body and hook of the flagella?
- 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
What are plasmids?
- 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
What are the subunits of ribosomes in eukaryotes vs. prokaryotes?
Eukaryotes: 40S and 60S
Prokaryotes: 30S and 50S
What is binary fission?
- 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
What are episomes?
A subset of plasmids that are capable of integrating into the genome of the bacteria
With regard to prokaryotes, what is transformation?
- 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
With regard to prokaryotes, what is conjugation?
- 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 (-)
With regard to prokaryotes, what is transduction?
- 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
What are transposons?
- 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
What are the phases of bacterial growth?
- 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
In viruses, what is positive and negative sense RNA?
- 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
What protein is specific to negative-sense RNA viruses?
- RNA replicase: must be carried in the virion to ensure that the complementary strand is synthesized
In regard to bacteriophages, what is the lytic cycle? Why is the lysogenic cycle?
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
Describe the phases of mitosis.
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
What is the product of meiosis I?
What is the product of meiosis II?
Meiosis I: results in homologous chromosomes being separated, resulting in haploid daughter cells
Meiosis II: results in the separation of sister chromatid
When does crossing over (genetics) occur?
During prophase I of meiosis
When does disjunction (genetics) occur? What is disjunction?
- 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
Where is sperm produced?
Seminiferous tubules
What cells nourish sperm?
- 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
What are interstitial cells of Leydig?
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).
Where are sperm stored until ejaculation?
In the epididymis
What is the function of the seminal vesicles?
- 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
Describe the stages of spermatogenesis?
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
Describe the hormone changes in the various phases of the menstural cycle
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
If implantation of blastocyst occurs, how is the uterine lining maintained?
- 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
In evolution, what are the three types of selection?
- Stabilizing
- Directional
- Disruptive
What is divergent evolution?
- 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
What is parallel evolution?
The process whereby related species evolve in a similar way for a long period of time in response to analogous environmental selection pressures
What is convergent evolution?
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
What is genetic drift?
- Changes in the composition of the gene pool due to chance
- Tends to be more pronounced in small populations
What is the Founder Effect?
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
Describe the Actin-Myosin Cross-Bridge Cycle
