BIOLOGY: Reproduction, development, viruses & prokaryotes/eukaryotes Flashcards
1
Q
card 128: starts reproduction & cells
microtubule transport
The intracellular scaffolding of a eukaryotic cell is composed of three families of protein filaments:
which motor protein mediates anterograde transport?
Which mediates retrograde transport?
A
- Microfilaments, intermediate filaments, and microtubules.
-
Intracellular transport of cargo (eg, organelles, vesicles) is mediated primarily by two microtubular motor proteins (kinesin and dynein).
- Kinesin mediates anterograde transport (ie, away from the nucleus)
- dynein mediates retrograde transport (ie, toward the nucleus).
2
Q
3 families of protein fibers
A
3
Q
Structure of mature sperm
head contains:
midpeice contains:
tail is used for?
A
- head (contains the acrosome and nucleus)
- midpiece (contains mitochondria that generate the ATP required for flagellum-driven sperm motility)
- tail (ie, the flagellum necessary for motility through a fluid environment).
4
Q
Fertilization image
A
5
Q
Spermatogenesis image
A
- spermatogonium—>spermatocyte—>spermatid–>spermatozoon
6
Q
Blastulation
A
7
Q
OOGENESIS process in a pic
A
8
Q
Overview of mitosis
A
- Prophase: DNA condenses to form chromatids. Each pair of sister (identical) chromatids are joined by a region called the centromere to form chromosomes. The nuclear envelope breaks down and centrosomes (microtubule-organizing structures) migrate to opposite poles within the cell. The mitotic spindle is formed as microtubules grow from these centrosomes.
- Metaphase: Chromosomes attach to spindle fiber microtubules at their kinetochores and align at the metaphase plate, a central plane within the cell.
- Anaphase: Sister chromatids are pulled apart by the spindle fibers and move toward opposite poles of the cell. This forms two sets of chromosomes within the cell (one set at each cellular pole).
- Telophase: The nuclear envelope is reformed around each set of chromosomes. Chromosomes decondense and the parental cell undergoes cytokinesis (cytoplasmic division) to produce two identical daughter cells.
9
Q
A single diploid cell containing 46 chromosomes underwent meiosis and produced four daughter cells, two with 22 chromosomes and two with 24 chromosomes. An error in which of the following stages of meiosis would most likely explain this result?
Chromosomal Disjunction
A
- Answer: Anaphase
- If a diploid cell with 46 chromosomes undergoes meiosis, four haploid daughter cells should be produced with each containing 23 chromosomes.
- However, in the given scenario two daughter cells have an extra chromosome and two daughter cells are missing a chromosome. Such a finding is most likely due to chromosomal nondisjunction, which occurs when either homologous chromosomes (during anaphase of meiosis I) or sister chromatids (during anaphase of meiosis II) fail to separate to opposite poles of the cell.
- Chromosomal nondisjunction during anaphase I may produce one daughter cell with an extra homologous chromosome (24 chromosomes) and one daughter cell missing a chromosome (22 chromosomes)
- Division of these cells in meiosis II would yield two cells with 22 chromosomes and two cells with 24 chromosomes.
10
Q
Difference of meiosis I & meiosis II:
A
11
Q
Metaphase chromosome
A
12
Q
CELL CYCLE
INTERPHASE
A
13
Q
SPERMATOGENESIS & OOGENESIS
similarities & differences
A
14
Q
Cell Migration in embryogenesis
neural crest give rise to:
nerual tube gives rise to:
A
- is the movement of cells into their final positions within the embryo
- The migratory actions of neural crest cells during neurlation (the formation of the nervous system) gives rise to many peripheral nervous system structures
- schwann cells & satellite cells
-
incontrast, the central nervous system is derived from the nerual tube
- oligodendrocytes & astrocytes
15
Q
3 Germ layers form during gastrulation
A
- Endoderm (innermost layer): gives rise to accessory digestive organs (eg, liver, pancreas) as well as to the lining (epithelium) of the digestive and respiratory tracts.
-
Mesoderm (middle layer): gives rise to the circulatory system, the musculoskeletal system, and parts of the urinary and reproductive systems.
- notochord is a mesodermal structre
- Ectoderm (outermost layer): gives rise to the nervous system (neurulation) and develops into the integumentary system, which includes hair, skin, nails, and the lining of the mouth, nostrils, and anus.
16
Q
Potency during development
Totipotent
Pluripotent
Multipotent
A
- Totipotent stem cells are the least specialized cells and can give rise to both placental and fetal cells.
- Pluripotent stem cells can give rise to only fetal cells (ie, all cell lineages from the three germ layers).
- Multipotent cells are able to differentiate only into the specialized cells of certain tissues and are also found in adults.
17
Q
Cell determination:
Cell Differentiation
Inductive Signaling
A
- Cell determination (specification of cell fate)
- Cell differentiation (acquisition of unique/specialized biomedical & structural cellular characterisitcs)
- BOTH ^^ result from asymmetric segregation of cytoplasmic determinants & inductive signaling
- Cell fate is influenced by _inductive signaling_ between cells in the early embryo. In inductive signaling, an inducer (the signaling cell) releases chemical signals that act on competent neighboring cells by regulating the expression of specific genes required for cell determination.
18
Q
Morphogens
A
-
are signaling molecules that influence cell differentiation in the emebryo
- they are released by signaling cells & diffuse outward to alter gene expression in competent cells in a conentration-dependent manner
- morphogens are paracrine factors
19
Q
Apoptosis:
newborn with myelomeningocele
A
- newborn with myelomeningocele has HIGH incidence of apoptosis induced by oxidative stress during gestation as well as:
- Higher frequency of cell damage at critical developmental periods during gestation
- Higher cellular concentrations of free radicals during gestation
- Lower levels of enzymes with antioxidant capabilities during gestation
-
Apoptosis (programmed cell death) is crucial for normal embryonic patterning and development. Oxidative stress occurs when the body is unable to detoxify naturally generated reactive oxygen species, which then cause considerable cell damage upon accumulation.
- This damage can result in abnormal apoptosis and congenital malformations.
20
Q
Oxidative Stress
A
- Oxidative stress occurs when the body is unable to detoxify reactive oxygen species (ROS), such as peroxides and free radicals.
- ROS are naturally generated from cellular reactions involving oxygenase or oxidase enzymes, as well as from reactions that take place in mitochondria (via oxidative phosphorylation) and peroxisomes (via β-oxidation of long-chain fatty acids).
- ROS contain an unstable number of electrons and are usually trapped or converted to less reactive molecules by antioxidants or enzymes with antioxidant activity, respectively.
- When ROS production exceeds the body’s natural elimination capabilities, ROS react with and damage cellular components. This type of injury can result in abnormally activated _apoptosis_.
21
Q
DNA sequencing
Southern Blot
Northern Blot
A
- DNA sequencing and Southern blotting are DNA assays that may be used to assess the relative quantity of genes between tissue types.
- Northern blotting is an RNA assay used to assess gene expression in different tissues
22
Q
Effects of estrogen & progesterone
A
-
in addition to image
- Bone is continuously being resorbed (broken down) by osteoclasts and rebuilt by osteoblasts. Female sex hormones maintain bone mass by helping balance the rate of osteoclast activity with the rate of osteoblast activity. Withdrawal of female sex hormones (due to ovary removal) leads to greater osteoclast than osteoblast activity, diminishing bone mass and leading to porous and fragile bone.
23
Q
Vasoconstriction & vasodilation
A
- Vasodilation (blood vessel widening) decreases blood pressure and increases blood flow to the tissues supplied by that blood vessel.
- Vasoconstriction (blood vessel narrowing) increases blood pressure and decreases blood flow to the tissues supplied by that blood vessel.
24
Q
Vasodilation & vasoconstriction with body temperature
A
- When body temperature is higher than normal (eg, in warm environments), blood vessels supplying the skin vasodilate to facilitate blood flow to the body surface, promoting heat loss through the skin and decreasing body temperature.
- In addition, Vasodilation of renal blood vessels inc blood flow to the kideny & consequently inc GFR (amountof blood filtered per unit time). This increased urine output & dec blood volume, worsening hydration
- When body temperature is lower than normal (eg, in cold environments), blood vessels supplying the skin vasoconstrict to limit the amount of blood reaching the body surface, limiting heat loss to the environment and increasing body temperature.
25
Q
Cell cycle, checkpoints, & effectiveacncer drug target which phase?
A
- Most cells in the human body are arrested in G0.
- However, cellular transition into G1 prepares a cell for division and DNA synthesis (S phase). In the G2 phase, DNA is checked for errors and the cell ensures that sufficient organelles and cytoplasm are available for cell division.
- Subsequently, the cell divides in the M phase via mitosis and cytokinesis.
- Compounds that inhibit cell division typically target the cell cycle in phases G1 to M.
Control of cellular division occurs at checkpoints within the cell cycle.
- At the G1/S phase transition, the cell commits to undergoing a division cycle whereas the G2/M phase transition acts as a quality-control step in which the cell cycle is stopped and cellular components are checked for abnormalities.
- Checkpoints are regulated primarily by cyclins and cyclin-dependent kinases. Cells with abnormalities that cannot be repaired undergo apoptosis; those that pass the checkpoints continue to divide. Anticancer drugs often target these checkpoints due to the regulatory roles on the cell cycle.
26
Q
Human spern & oocyte are different & same in when?
A
- SAME: EQUAL CONTRIBUTION OF CHROMOSOMES TO A ZYGOTE
-
DIFFERENT:
- cell volume: sperm is the smallest cell in the human body (neglgible cytoplasm), egg is the largest human cell & has organelles and large amount of cytoplasm
-
matrutation at birth
- testes contain immature germ cells (spermatogonia), they begin to undergo meiosis at puberty (early teen years) when the gonads mature
- girls have primary oocyte arrested at prophse of meiosis I & remain in this state until ovulatory cycle beings at puberty
- rate at whch they are produced
27
Q
Oogenesis
A
- Oogenesis is the process by which females produce sex cells (gametes) called eggs. All of a woman’s developing eggs (oocytes) are produced during fetal development.
- At birth, their maturation is arrested in prophase I; these arrested eggs are known as primary oocytes. At puberty, the menstrual cycle begins, and each month a single primary oocyte develops into a secondary oocyte by continuing meiosis up to metaphase II.
28
Q
Fertilization & implantation
A
29
Q
Endocytosis & types
how do viruses uptake material into cells?
A
-
Cells take up their surrounding environment via endocytosis, which includes mechanisms of phagocytosis, pinocytosis, and receptor-mediated endocytosis.
- when the virus inside the vesicles pinches off-it becomes an endosome
-
Many viruses use receptor-mediated endocytosis to enter cells.
- Enveloped viruses can also enter cells by fusing their membrane with the membrane of the cell.
- in which an external ligand binds specific receptor proteins on the cell surface. This binding induces the plasma membrane to bud inward toward the cytosol before pinching off as a vesicle that contains both the ligand and its receptor.
30
Q
Viruses with a caspid encased in a phospholipid membrane, known as enveloped viruses, HOW DO THEY ENTER THE CELL?
A
- Can fuse with their membranes with the cell membrane
- When this occurs, no vesicle is formed and the capsid is released directly into the cytosol.
31
Q
Phagocytosis
A
- “cell-eating” solids
32
Q
Pinocytosis
A
- nonspecific process (doesn’t require receptor binding) that involves the continuous invagination fo the cell membrane to take up the extracellular fluid
- taking in iiquids
33
Q
Fluid Mosiac Model
A
- The cell membrane is said to be fluid as its various nonphospholipid components are able to migrate laterally through the entire phospholipid-rich surface of the cell in any direction.
- These other important components include cholesterol, glycoproteins, and glycolipids (proteins and lipids that have been modified with carbohydrates).
- Many membrane proteins, called transmembrane proteins, span the width of the membrane. When a ligand binds to transmembrane proteins, which must be able to migrate laterally through the phospholipid environment of the cell membrane.
34
Q
Transmembrane proteins
A
- The phospholipid bilayer of the cell membrane has an outer leaflet that interacts with the extracellular environment and an inner leaflet that interacts with the cytoplasm of the cell.
- Transmembrane proteins cross the entire phospholipid bilayer and therefore interact with both the outer and inner leaflets.
- Proteins that interact with only one leaflet are not transmembrane proteins.
35
Q
Plasma Membrane
Secretory pathway of processing proteins
A
-
The secretory pathway involves the processing of proteins as they go through the endoplasmic reticulum and the Golgi apparatus.
- Translation of mRNA to proteins always begins in the cytosol, but proteins intended for the secretory pathway have an N-terminal sequence called a signal sequence.
- Once the signal sequence is recognized, the ribosome is transported to the roughendoplasmic reticulum (RER)
- After processing in the Golgi, proteins destined for the cell membrane are packed into secretory vesicles, which fuse with the plasma membrane.
- Other organelles, such as the nucleus, mitochondria, and peroxisomes, are not involved in the secretory pathway, and most of their proteins are translated in the cytosol.
36
Q
Endosomal acidification requires what type of transport?
A
- Active Transport
- there is so much acid inside the endosome, so H+ from the cytosol to the endosome will move against its concentration gradient
37
Q
Endosomal Pathway
A
38
Q
Proteosome
A
- is a protein complex found in the cytosol that typically degrades ubiquitinated proteins.
39
Q
Bacteriophage Life cycles:
Lytic & lysogenic cycles
_All viruses are _________________ because they cannot replicate independently outside of a host cell._
A
- obligate intracellular parasites
- Bacteriophages use the host cell’s machinery and resources to replicate their genome and synthesize viral proteins to form new virions.
- Phages with a lytic life cycle replicate rapidly and release progeny via lysis of the host cell.
- In contrast, phages with a lysogenic life cycle integrate their genome with the host genome and replicate as the cell divides.
42
Q
Bacterial Growth
Example: A student adds 5 bacterial cells to a test tube containing fresh medium and incubates it for 3 hours at 37°C. If the bacterial population shows an initial lag phase of 20 minutes followed by a doubling time of 40 minutes, what is the approximate number of bacterial cells present at the end of the incubation period? (Note: Assume unrestricted growth during incubation.)
A
- Answer: 80 cells
- Binary fission is the process by which a unicellular organism (eg, bacterium) divides into two identical daughter cells.
- The exponential generation time refers to the time in which a bacterial population doubles or the time needed for a single bacterium to divide in two
- When a single cell divides by binary fission, the number of cells that result is calculated by multiplying the original number of bacterial cells by 2n, where n equals the number of generations.
According to the question/explained:
- 5 bacterial cells were incubated for 3 hours (180 minutes); these exhibited a 20-minute lag phase and a 40-minute generation time. Assuming unrestricted growth during incubation, the bacterium could only have had a log phase and a lag phase. Therefore, the number of cells that result after incubation can be calculated as follows:
- Calculate the amount of time in which the bacterial population was in log phase: 180 min incubation time − 20 min lag phase = 160 min log phase
- Find the number of generations in the log phase period: 160 min log phase / 40 min generation time = 4 generations
- Multiply the original number of bacterial cells by 2n to get the final population size: 5 × 24 = 80 cells
43
Q
Bacterial growth curve:
A
44
Q
Prokaryotic domains
A
45
Q
Prokaryotic vs. Eukaryotic
A
46
Q
Glycolysis in prokaryotes/eukaryotes:
A
- glycolysis is a process that occurs in the cytoplasm of both prokaryotic and eukaryotic cells, and results in the synthesis of pyruvate.
- Therefore, the presence of pyruvate in the pathogen’s cytoplasm would not be a defining characteristic that would help determine whether it is prokaryotic or eukaryotic BECUASE IT IS PRESENT IN BOTH
47
Q
ENVELOPED & NONENVELOPED VIRUSES
A
- All viruses contain a protective protein coat known as the capsid.
- Viruses that contain only a capsid as an outer layer are known as non-enveloped or naked viruses, and are able to survive in harsh conditions (more resistance to heat, detergents, and changes in moisture)
- Viruses with a phospholipid bilayer surrounding the viral capsid are referred to as enveloped viruses; these are more susceptible to changes in environmental conditions (sensitive to heat, detergents, and changes in moisture)
- Fluresence anutibodies:*
- depending on the presence or absence of fluorescence, researchers would be able to determine whether the virus is non-enveloped (presence fluorescence) or enveloped (absent flurescent), respectively.
48
Q
Retroviruses
A
- Retroviruses are enveloped, positive-sense, single-stranded RNA viruses (+ssRNA) that convert their RNA genomes into double-stranded DNA using the enzyme _reverse transcriptase (RNA-dependent DNA polymerase activity)_
- During their lysogenic cycles, retroviruses enter the nucleus and integrate their reversed transcribed DNA with the host genome.
49
Q
Bacteriophages
A
- Bacteriophages are viruses that exclusively infect bacterial cells but do not enter host cells to replicate ther genetic material.
- They contain tail fibers that allow them to recognize and attach to the cell membrane, and a tail sheath that injects the viral genome into the bacterium.
50
Q
PRIONS
A
- is a misfolded protein that acts as an infectious agent by inducing other normal proteins to change their secondary structure and become misfolded.
- These less soluble misfolded proteins aggregate and can cause disease.
- Prions do not contain genetic material and cannot transform bacteria.
51
Q
VIROIDS
A
- Viroids are not viruses; instead, they are pathogenic, circular, single-stranded RNA molecules lacking protein coats and primarily affect plants.
- They typically silence the expression of specific genes and inhibit protein synthesis by binding RNA sequences.
- Viroids enter cells by hiding inside viruses or through damaged tissue
52
Q
Prokaryote DNA
A
- In the nucleoid region of prokaryotic cells, double-stranded DNA is condensed into a circular chromosome that has no telomeres or associated histones.
- By contrast, eukaryotic cells package their histone-wrapped, double-stranded DNA into linear chromosomes with ends capped by telomeres to prevent DNA from unraveling.
53
Q
Endosymbiotic theory
Symbiotic relationship
A
- The endosymbiotic theory explains how primitive eukaryotic anaerobes engulfed ancient aerobic prokaryotes, and consequently acquired the ability to produce energy through oxidative phosphorylation.
- This endosymbiotic theory of eukaryotic evolution is widely accepted because, like bacteria, mitochondria have their own genome (ie, mitochondrial DNA) and possess an independent system for transcription and translation distinct from that of the nuclear eukaryotic genome.
55
Q
Eukaryotic protein synthesis/ Rough ER protein synthesis
A
- being on free ribosomes in the cytoplasm.
- However, the presence of a signal sequence on the nascent polypeptide directs the ribosome-protein complex to the rough ER (RER). The growing polypeptide chain is threaded into the RER lumen and the signal sequence is removed.
- The peptide is then packaged into vesicles and sent to the Golgi body, where proteins designed for secretion undergo biochemical modifications and are packaged into transport vesicles destined for the plasma membrane.
- These vesicles then fuse with the plasma membrane and release their contents outside the cell.
56
Q
Prokaryotic protein synthesis
A
- signal sequence guides the protein destined for secretion directly to protein channels found on the plasma membrane.
58
Q
Prokaryotes and eukaryotes translation & transcription
A
- Prokaryotic cells have no nucleus; therefore, transcription and translation occur simultaneously in the cytoplasm (ie, translation begins before the mRNA is fully transcribed).
- By contrast, in eukaryotic cells transcription and post-transcriptional modifications occur in the nucleus, but translation occurs in the cytoplasm.
- In eukaryotic cells, transcription of mRNA and its modification (eg, addition of the 5′ cap, 3′ poly-A tail, splicing) typically occur in the nucleus. The modifications, which result in a mature mRNA molecule, increase the stability of the transcript and prevent its degradation in the cytoplasm. Because the nucleus is separated from the cytoplasm by a nuclear envelope, mRNA must first be transported through nuclear pores to the cytoplasm, where it is translated by ribosomes.
Both have ribosomes (P=70S, E=80S)
59
Q
Conjugation
A
- Conjugation is the transfer of genetic information from one bacterial cell to another via direct contact facilitated by the sex pilus. The sex pilus is encoded by genes contained in the F factor plasmid.
- The donor cell contains the F (fertility) factor plasmid, a circular piece of DNA containing genes that direct the formation of the sex pilus.
- During conjugation, the sex pilus from the donor cell attaches to a recipient cell (one that does not contain F factor) and facilitates the transfer of a single strand of the F factor plasmid DNA to the recipient cell.
- The recipient then synthesizes a complementary strand and becomes capable of passing genetic information to another bacterium.
- The F factor plasmid is typically found outside the bacterium’s genome, but it can integrate into the bacterial chromosome. When integration occurs, bacterial genes can be transferred with the F factor.
60
Q
Transformation
A
- is the cellular uptake of foreign DNA from the environment.
- This process is enhanced with increased cell membrane permeability (competence) that occurs in response to physical manipulation.
61
Q
Transduction
A
- involves DNA transfer from one bacterial cell to another by a bacteriophage (a virus that infects bacteria).
- During assembly of bacteriophages inside an infected cell, bacterial DNA can become trapped within the capsid of newly created bacteriophages.
- Subsequent infection of other cells with these new bacteriophages results in the transfer of bacterial DNA into a new host.
64
Q
Bacteria & oxygen dependency
A
66
Q
Wester Blot involves ______________by gel electrophoresis, transfer onto a blotting membrane, & detection with _________________
proteins with _________ molecular weight migrate farthest, and proteins concentration is generally proportional to _____________
A
- protein seperation, protein-specific antibodies
- LOW (shortest amino acid sequence), band intensity (thickness)
67
Q
Cholesterol & fluidity
A
- cholesterol molecules decrease fluidity at higher temperatures and increase fluidity at lower temperatures.
