Biology Flashcards
evolution
process whereby the gene pool of a species changes over time b/c individuals with more desirable genes are selected for by the environment
species
group of organisms which are capable of reproducing with one another and producing viable offspring
natural selection
“survival of the fittest” which demonstrates a relative increase in the reproduction of organisms which have traits that are better suited for their environment, due to 3 principle: variation, inheritance, competition
variation
individuals within a population will have different traits
inheritance
offspring inherit traits from their parents
competition
more offspring are produced than can survive, so offspring with traits better suited to the environment will survived and have more offspring than individuals with less desirable traits
group selection
idea that natural selection sometimes acts on whole groups of organisms, favoring some groups over others leading to the evolution of traits that are advantageous to the group
speciation
Occurs when some kind of barrier prevents successful interbreeding between members of a species
allopatric speciation
occurs when the reproductive barrier is geographic
sympatric speciation
occurs when 2 populations become genetically distinct when living in the same location, b/c they have adapted to different elements of the same location or b/c they have developed unique mating behaviors
adaptation
process by which a population gradually develops traits that are better suited to a particular habitat
genetic diversity is affected by:
mutations, inbreeding, outbreeding, and genetic drift
inbreeding
increases the proportion of individuals with homozygous genotypes, therefore increasing the number of homozygous recessive phenotypes that are harmful
outbreeding
increases genetic diversity by promoting reproductive fitness
genetic drift
random changes in the diversity and/or number of alleles present in a population, usually decreases genetic diversity: can result in bottleneck or founder effect
bottleneck
crisis randomly kills a large portion of a population and decreases genetic diversity
founder effect
few members of a population move to a new habitat and the new population has a smaller gene pool with less diversity
carbohydrates of a plasma membrane
found on the exterior surface of cells and are bound to either proteins (forming glycoproteins) or to lipids (forming glycolipids)
waxes
composed of a long-chain FA bonded to an alcohol group, contribute to rigidity in the cell membrane and provide structure
transbilayer diffusion
when a phospholipid “flip-flops” to the opposite layer
flippase
brings a phospholipid from the outer leaflet to the inner leaflet
floppase
brings a phospholipid from the inner leaflet to the outer leaflet
scramblase
brings a phospholipid from the outer leaflet to the inner leaflet and a phospholipid from the inner leaflet to the outer leaflet
(doesn’t require ATP)
osmolarity
describes the total solute concentration of the solution which gives rise to osmotic pressure
(ex: high osmolarity: fewer water molecules with respect to solutes)
secondary active transport
uses one electrochemical gradient to move different molecules against their own concentration gradients (aka cotransport)
channel proteins
very selective and accept only 1 type of molecule for transport
facilitated diffusion
diffusion for substances that cannot cross the phospholipid bilayer due to their size and/or polarity
acquaporins
channel proteins that allow water to cross the membrane very quickly
cell-surface receptors can be either
ion channel-linked receptors, GPCRs, or enzyme-linked receptors
endocytosis
active transport that moves particles into a cell
phagocytosis
large particles that are taken in by a cell, once the vesicle contain the particle is enclosed, it merges with a lysosome for the breakdown of material
pinocytosis
“cell drinking” process that takes in molecules (including water) which results in a much smaller vesicle than phagocytosis
gap junctions
channels between neighboring cells that allow for the transport of ions, water, and other substances between cells
(formed by connexons)
tight junctions
create a watertight seal between 2 animal cell
desmosomes
act like spot welds between adjacent epithelial cells
- formed by cadherins: specialized adhesion proteins found on the membranes of both cells and interact in the space between them holding the membrane together
- Ensure that cells in organs and tissues that stretch such as skin and cardiac muscle remain unbroken
3 defining characteristics of a eukaryotic cell
- A membrane-bound nucleus
- A number of membrane-bound organelles
- Mitotic division: results in 2 daughter cells each have the same number and kind of chromosomes as the parent cell
prokaryotes DO not have a
mitochondria
mitochondria
- Double-membrane organelles that contain their ribosomes and DNA
- Matrix contains mitochondrial DNA and ribosomes, allowing mitochondria to be self-replicating
lysosomes
- Organelle that contains digestive enzymes for breaking down parts of the cell
- “Garbage disposal”
- Hydrolytic enzymes within the lysosomes aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and worn-out organelles
- Active at a lower pH
RER
ribosomes attached & modify proteins, also makes phospholipids for membranes
SER
synthesis of carbohydrates, lipids, steroid hormones, detoxification, and storage of calcium ions
golfi
Sorts and packages materials before they leave the cell to ensure they arrive at the proper destination
perioxisomes
- Lipid metabolism and chemical detoxification
- Carry out redox reactions that break down FA and amino acids
- Neutralize positions like free radicals that enter the body via H202
3 protein fibers that make up the cytoskeleton
- microfilaments
- intermediate filaments
- microtubules
microfilaments
used for cellular movement and give shape to the cell as well as support its internal parts
microtubules
(largest) : help cell resist compression, provide a track along which vesicles move through the cell and pull replicated chromosomes to opposite ends of a dividing cell
- composed of tubulin, make up the structures of flagella and cilia
intermediate filaments
contribute to cellular structural elements and are often crucial in holding together tissues like skin
-only found in certain animal cells, no roles in movement or transport
in eukaryotes, cilia and flagella structure have this arrangement:
9+2 array, Motor proteins known as dyneins are attached to each of the 9 doublets, making the possible bending movement of flagella and cilia possible
centrioles
2 form a centrosome, play a role in organizing the microtubules that separate chromosomes during cell division
squamous epithelial cells are found to
Facilitate diffusion in tissues such as lungs or blood capillaries
cuboidal epithelial cells are found in
glandular tissues throughout the body which they secrete glandular material
columnar cells are found in the
respiratory tract they appear to be stratified but each cell is really attached to the basal membrane making it pseudostratified
transition cells are found in
urinary system, arranged in a stratified layer but have the capability to pile up on top of each other in a relaxed, empty bladder
domain: bacteria
composed of prokaryotes who have no membrane-bound organelles and make up a large proportion of living organism
domain: archaea
prokaryotes who are similar to bacteria but contain genes and metabolic pathways that are more similar to eukaryotes than bacteria
They inhabit extreme environments
prokaryotes lack a _ and instead have a
nucleus, circular chromosome located in a nucleoid
bacteria cell wall is composed of
thick, rigid peptidoglycan that maintains the cell’s shape, protects the interior and prevents bursting during osmosis
hypertonic solution
solution has a higher solute concentration than another solution
Leads to crenation (shriveling)
hypotonic solution
solution that has a lower solute concentration
Leads to cell expansion and lysing
pencillin
can be used to break down the peptidoglycan wall as it inhibits the construction of the bacterial cell wall, making it more likely to burst
basic structure of a bacterial flagella
consists of a basal body, hook, and filament
-composed of flagellin protein that spin in solution
binary fission
no genetic recombination or genetic diversity: the chromosome is replicated and the 2 resulting copies separate from one another due to the growth of the cell
transformation
prokaryote takes in DNA found in its environment that is shed by other prokaryotes
transduction
used bacteriophages to integrate viral/host DNA into other cells
conjugation
DNA is transferred from one prokaryote to another using a sex pilus which allows DNA to be transferred in the form of a plasmid
facultative anaerobes
toggle between aerobic and anaerobic metabolism
microaerophiles
need oxygen to grow, but high concentrations of it can poison them
aerotolerant anaerobes
oxygen tolerant: cannot use O2 for metabolism but the presence of oxygen doesn’t harm them
thioglycolate broth
enriched, differential medium used to determine the oxygen requirements of microorganisms
mutualistic
both species benefit from the interactions (ex: lichens have a good relationship with algae)
commensalism
one organism benefits while the other neither benefits nor suffers (ex: birds in trees)
parastism
parasite benefits while it harms the host
Obligate parasite: cannot reproduce or grow without a host
chemotaxis
Ability of a bacterial cell to detect chemical stimuli and move toward food or away from toxins
negative chemotaxis
arises to avoid places with high levels of toxins
plasmid
Piece of extragenomic DNA that exists and replicates independently from the chromosomal DNA within a cell (circular usually)
transposons
- Segments of DNA that can move and allow genes to be transferred to a host organism’s chromosomes, interrupting or modifying the function of a gene
- Designed to interrupt a gene in such a way that it causes maximal genetic widespread destruction (method is used to identify oncogenes)
virus structure
- Have genetic material made of nucleic acids
- Capsid proteins are encoded by the virus genome (RNA/DNA) and encloses the genetic material
virus reproduction
Must infect a host cell to hijack their reproductive machinery to replicate
retroviruses
(like HIV) have an RNA genome that must be reverse transcribed into DNA which is then incorporated into the host cell genome
generalized virus life cycle
- Attachment: virus recognizes and binds to a host cell via a receptor molecule on the cell surface
- Entry: virus of its genetic material enters the cell
- Genome replication & Gene expression: viral genome is copied and its genes are expressed to make viral proteins
- Assembly: new viral particles are assembled from the genome copies and viral proteins using the host cell ribosomes
- Release: completed viral particles exit the cell and can infect others
prions
proteins with a defective structure that also trigger other proteins to adopt this faulty structure
viroids
plant pathogens that consist of a small, circular, ssRNA particle
