concept 2b Flashcards
cell theory
- all living things are composed of cells
- the cell is the basic functional unit of life
- cells arise only from preexisting cells
- cells carry genetic information in the form of DNA. this genetic material is passed on from patron to daughter cell
eukaryotic cells
contain a true nucleus enclosed in a membrane
organisms can be unicellular or multicellular
contain many organelles in the cells
reproduce by mitosis allowing the formation of 2 identical daughter cells
prokaryotic cells
do not contain a nucleus
nucleus
control center of the cells
contains genetic material encoded in DNA, organized into chromosomes
surrounded by the nuclear membrane (envelope)
nuclear pores
in the nuclear membrane
allow for selective 2-way exchange of material b/w the cytoplasm and the nucleus
nucleolus
subsection of the nucleus
synthesizes rRNA
about 25% of the volume of the entire nucleus and can often be identified as a darker spot in the nucleus
mitochondria
power plants of the cell
important in metabolic functions
contains 2 membranes, inner and outer
contain some of their own genes and replicate independently of nucleus via binary fission
capable of killing cell by release of enzymes from ETC to kickstart apoptosis
mitochondrial matrix
space inside the inner membrane
pumping of protons from the matrix to the inter membrane space (out of the matrix) establishes the proton-motive force, protons then flow through ATP synthase to generate ATP during oxidative phosphorylation
lysosomes
membrane-bound organelle
contain hydrolytic enzymes that are capable of breaking down many different substrates
autolysis
process of release of lysosome enzymes
results in apoptosis
release of enzymes directly lead to degradation of cellular components
endoplasmic reticulum
interconnected membranes that are continuous with the nuclear envelope
folded into numbers invaginations creating complex structures w/ a central lumen
2 varieties: smooth and rough
rough ER
studded with ribosomes
site of protein translation that are destined for secretion directly into lumen
smooth ER
lacks ribosomes
utilized for lipid synthesis and detoxification of certain drugs and poisons
transports proteins from the RER to the Golgi apparatus
Golgi apparatus
consists of stacked membrane-bound sacs
modifies, sorts, and repackages, and transferred to correct cellular location in vesicles
materials are transferred from the ER to the Golgi and vesicles
peroxisomes
contain hydrogen peroxide
primary function is the breakdown of long chain fatty acids via beta-oxidation
participate in the synthesis of phospholipids and contain some of the enzymes involved in pentose phosphate pathway
cytoskeleton
provides structure to the cell and help it to maintain its shape
provides a pathway for the transport of material around the cell
3 components: microfilaments, microtubules, and intermediate filaments
microfilaments
made up of polymerized rods of actin
actin filaments are organized in bundles and networks that provide protection for the cell
role in cytokinesis, division of materials b/w daughter cells, during mitosis the cleavage furrow is formed from microfilaments
microtubules
hollow polymers of tubular proteins
provide primary pathway along witch motor proteins like chines and dyne carry vesicles
cilia and flagella are motile structures composed of microtubules
cilia
projections from a cell that are primarily involved in moment of materials along the surface of the cell
one projection
made up of microtubules
flagella
structures involved in movement of the cell itself
multiple small, hairlike projections
made up of microtubules
centrioles
found in centrosome
organizing centers for microtubules
structured as 9 triplets of microtubules with hollow center
migrate to opposite poles of dividing cell in mitosis and microtubules originate from these and attach to chromosomes at the kinetochores
intermediate filaments
diverse group of filamentous proteins, including keratin and desmin
involved in cell-cell adhesion or maintenance of the overall integrity of the cytoskeleton
able to withstand a lot of tension making the cell structure more rigid
help to anchor other organelles
tissue types
epithelial tissue
connective tissue
muscle tissue
nervous tissue
epithelial tissue
cover the body and line its cavities
means for protection against pathogen invasion and desiccation
involved in absorption, secretion, and sensation
tightly joined to each other and to an underlying layer of connective tissue
tissues are diverse and serve numerous functions depending on the identity of the organ
often polarized, one side faces a lumen or outside world and other interacts w/ blood vessels and structural cells
parenchyma
the functional parts of the organ
in most organs this constitutes as epithelial cells
classes of epithelial cells by # of layers
simple epithelia: single layer of cells
stratified epithelia: multiple layers of cells
pseudo-stratified epithelia: appear to have multiple layers due to differences in cell height but only have one layer
classes of epithelia cells by shape
cuboidal: cells are cube shaped
columnar: cells are long and thin
squamous: cells are flat and scalelike
connective tissue
supports the body and provides framework for the epithelial cells to carry out their functions
main contributors to the stroma (support structure)
most cells produce and secrete materials to form the extracellular matrix, like collagen and elastin
exp of connective tissues: bone, cartilage, tendons, ligaments, adipose tissue, and blood
binary fission
simple form of asexual reproduction seen in prokaryotes
circular chromosome attaches to the cell wall and replicates while cell grows in size
plasma membrane and cell wall grow inward at midline to produce 2 daughter cells
requires fewer steps than mitosis and is more rapid
plasmids
extrachromosomal material in bacteria
carry genes that impart some benefit to bacterium, antibiotic resistance
may also carry virulence factors
virulence factors
traits that increase how pathogenic a bacterium is
toxin production, projections that allow the bacterium to attach to certain kinds of cells, or evasion of the host’s immune system
contained in plasmids
episomes
subset of plasmids
capable of integrating into the genome of the bacterium
bacterial genetic recombination
helps increase bacterial diversity
permits evolution of a bacterial species over time
process includes transformation, conjugation, and transduction
transformation
results from integration of foreign genetic material into the host genome
foreign genetic material comes from other bacteria that spills their contents in the vicinity of a bacterium capable of transformation
conjugation
bacterial form of mating (sexual reproduction)
2 cells form a conjugation bridge that allows for the transfer of genetic material
transfer is unidirectional from the donor male (+) to the recipient female (-)
made from sex pili found in donor male
transduction
only genetic recombination process that requires a vector
transposition of genetic material from one organism to another by a virus
vector
a virus that carries genetic material from one bacterium to another
transposons
genetic elements capable of inserting and removing themselves from the genome
not limited to prokaryotes, has been seen in eukaryotes
if transposon is inserted within a coding region of the gene it may be disrupted
growth of bacteria
reproduce via binary fission
growth in a series of phases: lag phase, exponential (log) phase, stationary phase, and death phase
lag phase
in new environment bacteria first adapt to new local conditions during this phase
exponential phase
as bacteria adapt, growth increases, causing an exponential increase in the number of bacteria in the colony
aka log phase
stationary phase
as # of bacteria in colony grows, resources are often reduced
reduction of resources slows reproduction and this phase results
no more growth in bacteria
death phase
occurs as resources in the environment have been depleted
after bacteria have exceeded the ability of the environment to support the number of bacteria
virus structure
composed of genetic material, a protein coat, and sometimes an envelope w/ lipids
have a tail sheath and tail fibers
virus genetic information
may be circular or linear
single or double stranded
composed of DNA or RNA
capsid
the protein coat surrounding a virus
lipid envelope of a virus
it surrounds the capsid and composed of phospholipids and virus-specific proteins
very sensitive to heat, detergents, and desiccation
enveloped viruses are easier to kill
viruses w/out and envelope are more resistant to sterilization and likely to persist on surfaces for extended periods of time
virus reproduction
cannot reproduce independently, considered obligate intracellular parasites
must express and replicate genetic info within a host cells bc they lack ribosomes to carryout protein synthesis
once they take of cell’s machinery the virus will replicate and produce viral progeny (virions) which can be released to infect additional cells
virus structure
composed of genetic material, a protein coat, and sometimes an envelope w/ lipids
bacteriophages
viruses that specifically target bacteria
do not enter bacteria but inject their genetic material
in addition to a capsid they have a tail sheath and tail fibers
tail sheath
can act like a syringe
injects genetic material into a bacterium
tail fibers
help the bacteriophage to recognize and connect to the correct host cell
single-stranded RNA viruses
may be positive sense or negative sense
virus genetic information is single stranded RNA
positive sense
implies that the genome may be directly translated to functional proteins by the ribosomes of the host cells
negative sense
more complicated than positive sense
these viruses require synthesis of an RNA strand complementary to the negative-sense RNA strand
this strand can be used as a template for protein synthesis
may carry RNA replicase in the virion to ensure that the complementary strand is synthesized
retroviruses
enveloped, single stranded RNA viruses
virion contains 2 identical RNA molecules
carry enzyme reverse transcriptase which synthesizes DNA from single stranded RNA
DNA then integrates into the host cell genome where is is replicated and transcribed
mechanism of the integration of genetic material into the host cell genome allows for cell to be infected indefinitely
only way to cure the infection is to kill the infect cell itself
exp. is human immunodeficiency virus (HIV)
viral life cycle
infection
translation and progeny assembly
progeny release
lytic and lysogenic cycles
infection
to infect a cell the virus has to bind to specific receptors on the host cell
once they are bound they are brought in close proximity to permit additional interactions
depending on virus, different portions of the virion will be inserted into the host cells
enveloped viruses fuse w/ membrane and enter the cell to interact
bacteriophages only insert their genetic material
translation
must occur for virus reproduction
translocation of genetic material to the correct location in the cell
using ribosomes, tRNA, amino acids, and enzymes of the host cell, the viral RNA is translated into protein
most of these proteins are structural capsid proteins and allow for creation of new virions
progeny assembly
once viral genome is replicated it is packaged within the capsid
viral genome must be returned to its original form before packaging
progeny release
may be released in multiple ways
- viral invasion may initiate cell death which results in spilling of the viral progeny
- host cell may lyse as a result of being filled with extremely large numbers of virions, lysis is a disadvantage bc virus can no longer use the cell to carry outs its life cycle
- virus can leave the cell by fusing with its plasma membrane in a process known as extrusion, allows for survival of host cell and continued use of host cell by virus, this is called a productive cycle
lytic cycle
bacteriophage makes maximal use of cells machinery w/ little regard for survival of host cell
host swells w/ new virion, cell lyses, and other bacteria can be infected
bacteria in this phase are termed virulent
lysogenic cycle
virus does not lyse the bacterium and may integrate into the host genome as a provirus or prophage
virus is replicated as bacterium reprocess bc it is now part of host genome
environmental factor will cause provirus to leave the genome and revert to lytic cycle
prions
very small (subviral) particles
infectious proteins and nonliving things
cause disease by triggering misfiling of other proteins, usually involve conversion from alpha-helix to beta-sheets
this reduces the solubility of proteins
protein aggregates form and function of the cell is reduced
viroids
small plant pathogens consisting of very short circular single stranded RNA
bind to a large # of RNA sequences and silence genes in the plant genome
this prevents synthesis of proteins and cause metabolic and structural derangements
hepatitis D is an example of this in humans and alone is innocuous but when coinfected with hepatitis B is able to silence functioning on human hepatocytes
