The Cell Flashcards
cell theory
four basic tenets:
- 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 deoxyribonucleic acid (DNA); this genetic material is passed on from parent to daughter cell
eukaryotic cells
contain a true nucleus enclosed in a membrane
prokaryotic cells
do not contain a nucleus
lack mitochondria
primitive cytoskeleton
different size of ribosome
organelles
in eukaryotic cells, most are membrane-bound, which allows for compartmentalization of functions
cytosol
allows for the diffusion of molecules throughout the cell
nucleus
within which genetic material encoded in DNA, organized into chromosomes
contains all of the genetic material necessary for replication of cell
surrounded by double membrane that maintains a environment separate and distinct from the cytoplasm
mitosis
how eukaryotic cells reproduce, forming two identical daughter cells
nuclear envelope
double membrane that maintains an environment separate and distinct from the cytoplasm
nuclear pores
in nuclear membrane, allow for selective two-way exchange of material between the cytoplasm and the nucleus
genes
coding regions of DNA
histones
linear DNA wound around these organizing proteins
chromosomes
once linear DNA wound around histones, wound further into these linear strands
nucleolus
subsection of the nucleus where ribosomal RNA (rRNA) is synthesized
only takes about ~25% of volume of entire nucleus
mitochondria
“the power plants of the cell” – reference to important metabolic functions
contain two layers: outer and inner membranes
semi-autonomous
contain some of their own genes and replicate independently of the nucleus via binary fission
thought to have evolved from an anaerobic prokaryote engulfing an aerobic prokaryote and establishing a symbiotic relationship
capable of killing the cell by release of enzymes from the electron transport chain –> kick-starts apoptosis
outer membrane of mitochondria
serves as barrier between cytosol and inner environment
cristae
numerous infolding of the inner membrane, which contains molecules and enzymes necessary for electron transport chain
highly convoluted structures that increase the surface area available for electron transport chain enzymes
intermembrane space
space inside the inner and outer membranes
mitochondrial matrix
space inside the inner membrane
apoptosis
programmed cell death
lysosomes
membrane-bound structures containing hydrolytic enzymes that are capable of breaking down many different substrates, including substances ingested by endocytosis and cellular waste products
autolysis
release of hydrolytic enzymes of the lysosome
results in apoptosis
directly lead to degradation of cellular components
endoplasmic reticulum (ER)
series of interconnected membranes that are actually contiguous with the nuclear envelope
single membrane folded into numerous invaginations, creating complex structures with a central lumen
two varies: smooth and rough
rough ER (RER)
studded with ribosomes
ribosomes
permit the translation of proteins destined for secretion directly into its lumen
smooth ER (SER)
lacks ribosomes and is utilized primarily for lipid synthesis and the detoxification of certain drugs and poisons
transports proteins form the RER tot he Golgi apparatus
Golgi apparatus
consists of stacked membrane-bound sacs
materials from ER transferred here in vesicles, may be modified by the addition of various groups, including carbohydrates, phosphates, and sulfates
may also modify cellular products through introduction of signal sequences, which direct the delivery of the product to a specific cellular location
after modification, cellular products are repackaged in vesicles, which are subsequently transferred to the correct cellular location
exocytosis
if product in Golgi apparatus is destined for secretion, secretory vesicle merges with cell membrane and its contents are released
peroxisomes
contain hydrogen peroxide
one of primary functions: breakdown of very long chain fatty acids via ß-oxidation
participate in synthesis of phospholipids and contain some of the enzymes involved in the pentose phosphate pathway
cytoskeleton
provides structure to the cell and helps it to maintain its shape
provides a conduit for the transport of materials around the cell
three components: microfilaments, microtubules, and intermediate filaments
microfilaments
made up of solid polymerized rods of actin
organized into bundles and networks and are resistant to both compression and fracture, providing protection for the cell
can use ATP to generate force for movement by interacting with myosin (i.e. muscle contraction)
cytokinesis
division of materials between daughter cells
role of microfilaments: create cleavage furrow
- actin filaments contract to pinch off connection between the two daughter cells
cleavage furrow
formed from microfilaments
organize as a ring at the site of division between the two new daughter cells
microtubules
hollow polymers of tubulin proteins
radiate throughout the cell, providing the primary pathways along which motor proteins (i.e. kinesin/dynein) carry vesicles
cilia and flagella are motile structures composed of these
cilia
projections from a cell that are primarily involved in movement of materials along the surface of a cell (i.e. line the respiratory tract and are involved in movement of mucus)
composed of nine pairs of microtubules forming an outer ring, with two microtubules in the center
flagella (eukaryotes)
structures involved in movement of the cell itself, such as the movement of sperm cells through the reproductive tract
composed of nine pairs of microtubules forming an outer ring, with two microtubules in the center
9 + 2 structure
nine pairs of microtubules forming an outer ring, with two microtubules in the center
structure of cilia and flagella, seen only in eukaryotic organelles of motility
centrioles
found in region of the cell called the centrosome
organizing centers for microtubules and structured as nine triplets of microtubules with a hollow center
during mitosis, these migrate to opposite poles of the dividing cell and organize the mitotic spindle
- microtubules emanating from these attach to the chromosomes via complexes called kinetochores and can exert force on the sister chromatids, pulling them apart
intermediate filaments
diverse group of filamentous proteins, including karting and desmin
many involved in cell-cell adhesion or maintenance of the overall integrity of the cytoskeleton
able to withstand a tremendous amount of tension, making the cell structure more rigid
help anchor other organelles, including the nucleus
identity of proteins within a cell is specific to the cell and tissue type
epithelial tissues
cover the body and line its cavities, providing a means for protection against pathogen invasion and desiccation
its cells are involved in absorption, secretion, and sensation; tightly joined to each other and to an underlying layer of connective tissue known as the basement membrane
- highly diverse and serve numerous functions depending on the identity of the organ in which they are found
parenchyma
in most organs, epithelial cells constitute this
functional parts of the organ
i.e. nephrons in the kidney, hepatocytes in the liver, and acid-producing cells of the stomach are all composed of epithelial cells
epithelial cells
polarized, meaning that one side faces a lumen (the hollow inside of an organ or tube) or outside world, while the other side interacts with blood vessels and structural cells
i.e. in the small intestine, one side of the cell will be involved in absorption of nutrients from the lumen, while the other side will be involved in releasing those nutrients into circulation for use in the rest of the body
simple epithelia
have one layer of cells
stratified epithelia
have multiple layers
pseudostratified epithelia
appear to have multiple layers due to differences in cell height, but are, in reality, only one layer
cuboidal epithelia
cube-shaped
columnar epithelia
long and thin
squamous epithelia
flat and scalelike
connective tissue
supports the body and provides a framework for the epithelial cells to carry out their functions
main contributors to the stroma (support structure)
i.e. bone, cartilage, tendons, ligaments, adipose tissue, blood
most of its cells produce and secrete materials such as collagen and elastin to form the extracellular matrix
nucleoid region
genetic material of prokaryotes organized into a single circular molecule of DNA concentrated in this area of the cell
Archaea
single-celled organisms that are visually similar to bacteria, but contain genes and several metabolic pathways that are more similar to eukaryotes than to bacteria (share a common origin with eurkarya?)
-both start translation with methionine, contain similar RNA polymerases, and associate their DNA with histones
-contain a single circular chromosome, divide by binary fission/budding, share similar structure to bacteria
resistant to many antibiotics
considered extremophiles
great variety of habitats for these organisms, including the human body
notable for ability to use alternative sources of energy
- many are chemosynthetic and are able to generate energy from inorganic compounds, including sulfur- and nitrogen-based compounds (NH3)
bacteria
all contain a cell membrane and cytoplasm, and some have flagella or fimbrae
ribosome significantly smaller than that of eukarya
approximately 5 x 10^30 on earth
mutualistic symbiotes or pathogens
mutualistic symbiotes
both humans and bacteria benefit from the relationship
i.e. bacteria in the human gut that produce vitamin K and biotin (vitamin B7), an which prevent the overgrowth of harmful bacteria
pathogens
provide no advantage or benefit to the host, but rather cause disease
these bacteria may live intracellularly or extracellularly
i.e. Chlamydia trachomatis: common sexually transmitted infection, lives inside cells of the reproductive tract; Clostridium tetani: cause of tetanus, lives outside of cells and produces toxins that enter the bloodstream
cocci
spherical bacteria
bacilli
rod-shaped bacteria
spirilli
spiral-shaped bacteria
obligate aerobes
bacteria that require oxygen for metabolism
anaerobes
bacteria that use fermentation or some other form of cellular metabolism that does not require oxygen
obligate anaerobes
anaerobes that cannot survive in an oxygen-containing environment
presence of oxygen leads to the production of reactive oxygen-containing radicals in these species, which leads to cell death
facultative anaerobes
bacteria that can toggle between metabolic processes, using oxygen for aerobic metabolism if it is present, and switching to anaerobic metabolism if it is not
aerotolerant anaerobes
bacteria that are unable to use oxygen for metabolism, but are not harmed by its presence in the environment
cell wall
forms outer barrier of the cell
each bacterium responsible for protecting itself from the environment
combined with cell membrane –> envelope
provides structure and controls the movement of solutes into and out of the bacterium, which allows cell to maintain conc gradients relative to the environment
two types: gram negative and gram positive
- type determined through Gram staining process with crystal violet stain, followed by counterstain with safranin
- envelope absorbs crystal violet stain (deep purple) = gram +
- envelope does not absorb crystal violet stain, but absorbs safranin counterstain (pink-red) = gram -
peptidoglycan
polymeric substance made from amino acids and sugars
found in gram + cell walls (thick)
cell wall may also aid pathogen by providing protection from host organism’s immune system
also found in gram - cell walls but in much smaller amounts (very thin)
lipoteichoic acid
function unknown, found in cell wall of gram + bacteria immune system may be activated by exposure to these chemicals
lipopolysaccharides
found in outer membranes of gram - bacteria (with phospholipids as well)
part of the gram - bacteria that triggers an immune response in human beings
inflammatory response to this much stronger than the response to lipoteichoic acid
chemotaxis
ability of cell to detect chemical stimuli and move toward or away from them
flagella (bacteria)
may have one, two, or many depending on species
composed of a filament, basal body, and hook
overall structure similar in both gram bacteria
filament (bacteria flagellum)
hollow, helical structure composed of flagellin
basal body (bacteria flagellum)
complex structure that anchors it to the cytoplasmic membrane and is also the motor, rotating at rates up to 300 Hz
hook (bacteria flagellum)
connects filament and basal body so that, as basal body rotates, it exerts torque on filament, which can thereby spin and propel bacterium forward
plasmids
found in bacteria
carry DNA that is not necessary for survival of the prokaryote (not considered genome of the bacterium) but may confer advantage such as antibiotic resistance
- extrachromosomal (extragenomic) material
may also carry virulence factors
subset call episomes
binary fission
simple form of asexual reproduction seen in prokaryotes
circular chromosome attaches to the cell wall and replicates while the cell continues to grow in size
eventually, the plasma membrane and cell wall begin to grow inward along midline of the cell to produce two identical daughter cells
can proceed more rapidly than mitosis
virulence factors
found in plasmids
traits that increase how pathogenic a bacterium is, such as toxin production, projections that allow the bacterium to attach to certain kinds of cells, or evasion of the host’s immune system
episomes
subset of plasmids
capable of integrating into the genome of the bacterium
bacterial genetic recombination
helps increase bacterial diversity and thus permits evolution of bacterial species over time processes include: - transformation - conjugation - transduction
transformation
genetic recombination
results from integration of foreign genetic material into host genome
most frequently, material comes from other bacteria that, upon lysing, spill their contents in vicinity of a bacterium capable of this
capability of many gram - rods
conjugation
genetic recombination
bacterial form of mating
involves two cells forming a bridge between them that allows for the transfer of genetic material
- transfer is unidirectional from the donor male (-) to the recipient female (+)
bridge made from appendages called sex pili found on donor male
- to form pili, bacteria must contain plasmids known as sex factors that contain the necessary genes
allows for rapid acquisition of antibiotic resistance or virulence factors throughout a colony because other plasmids can also be passed through the bridge
F (fertility) factor
best-studied sex factor
bacteria possessing this plasmid are termed F+, those without are F-
during conjugation, F+ cell replicates this and donates copy to recipient converting it to an F+ cell, which enable the cell to then transfer copies to other cells
transduction
only genetic recombination that requires a vector
vector
virus that carries genetic material from one bacterium to another
viruses
obligate intracellular pathogens = cannot reproduce outside of a host cell
not considered living things because they are acellular, cannot reproduce with the assistance of a host cell, and may contain RNA as their genetic material
bacteriophages
viruses that infect bacteria
contain a tail sheath and tail ribers
simply inject their genetic material, leaving remaining structures outside the infected cell
can accidentally trap a segment of host DNA during assembly
when it infects another bacterium, it can release this trapped DNA into the new host cell, which can integrate into the genome
transposons
genetic elements capable of inserting and removing themselves from the genome
not limited to prokaryotes
if inserted within a coding region of a gene, the gene may be disrupted
lag phase
in new environment, bacteria first adapt to the new local conditions
exponential phase (log phase)
as bacteria adapt, growth increases, causing an exponential increase in number of bacteria in the colony
stationary phase
reduction of resources slows reproduction
death phase
after the bacteria have exceeded the ability of the environment to support the number of bacteria
occurs as resources in the environment have been depleted
capsid
protein coat of virus
sometimes surrounded by envelope of phospholipids and virus-specific proteins (makes viruses easier to kill)
host cell
necessary for viruses to express and replicate genetic information within
virus hijacks machinary, replicates and produces viral progeny (virions) which can be released to infect additional cells
tail sheath
found on bacteriophage
can act like a syringe, injecting genetical material into a bacterium
tail ribers
help the bacteriophage to recognize and connect to the correct host cell
positive sense
some single-stranded RNA viruses
implies that the genome may be directly translated to functional proteins by the ribosomes of the host cell, like mRNA
negative sense
some single-stranded RNA viruses
require synthesis of an RNA strand complimentary to the original, which can then be used as a template for protein synthesis
must carry an RNA replicase in vision to ensure that complementary strand synthesized
retroviruses
enveloped, single-stranded RNA viruses
carry reverse transcriptase which synthesizes DNA from single-stranded RNA
DNA then integrates into host cell genome, replicated and transcribed as if it were the host cell’s own DNA
allows for cell to be infected indefinitely
only way to cure the infection is to kill the infected cell itself
i.e. human immunodeficiency virus (HIV): utilizes this life cycle, which is one of the characteristics that makes it so difficult to treat
extrusion
when virus leaves cell by fusing with its plasma membrane
allows for survival of the host cell, and continued use of host cell by the virus
productive cycle
when virus can leave host cell without destroying it, allowing for further use by the virus
lytic cycle
bacteriophage makes maximal use of the cell’s machinery with little regard for the survival of the host cell
once host is swollen with new visions, the cell lyses, and other bacteria can be infected
virulent
bacteria in the lytic phase
provirus/prophage
when virus does not lyse the bacterium
integrates into host genome
beginning of lysogenic cycle
lysogenic cycle
virus integrates into host genome
will be replicated as bacterium reproduces because it is now part of the host’s genome
environmental factors will cause provirus to leave the genome and revert to a lytic cycle at some point
may be some benefit
superinfection
simultaneous infection with other phages
infection with one strain of phage generally makes bacterium less susceptible to this
prions
infectious proteins
cause disease by triggering misfolding of other proteins, usually involving the conversion of a protein from an α-helical structure to a ß-pleated sheet, drastically reducing the solubility of the protein, as well as the ability of the cell to degrade the misfolded protein
cause mad cow disease, Creutzfeldt-Jakob disease, familial fatal insomnia
viroids
small plant pathogens consisting of a very short circular single-stranded RNA
can bind to a large number of RNA sequences and will silence genes in the plant genome
