Ch. 1 - The Cell Flashcards
bacteriophage
a virus that infects bacteria, typically it injects nucleic acids into the host cell through its tail after viral enzymes have digested a hole in the cell wall - a bacterial virus carrying its own DNA
virulent virus
capable of causing a disease
temperate virus
a virus in the lysogenic cycle; host may show no symptoms of infection. Virus is said to be latent, or dorment, and is called a provirus
viral envelopes
only some viruses have these - they are formed as they undergo exocytosis from the cell. The envelopes are pinched off pieces of the host cellular membrane. It protects the enveloped virus from detection by the immune system. The receptors on the envelope allow it to find new host cells and start the process all over again.
unenveloped viruses
typically lyse a cell and cause cell death on their release
how do most animal viruses enter a host cell?
Most animal viruses (not bacteriophages) don’t leave capsids outside the cell, but rather enter the cell through receptor mediated endocytosis - so most viruses inject eukaryotes are engulfed by an endocytotic process, meaning that the cell membrane surrounds the virus and brings it into the cell.
retroviruses
single-stranded RNA viruses that are able to transcribe RNA into dsDNA (which is reverse of what it usually is) and uses reverse transcriptase to do it (the enzyme is carried by the virus). The DNA made then can integrate into the host DNA, making it SUPER hard to eradicate the virus (ex. HIV). Retroviruses use reverse transcriptase.
viroid
small rings of naked RNA without capsids that only infect plants (1 of 2 subviral particles)
prion
naked proteins, causes infections in animals. They are capable of reproducing themselves without RNA or DNA (2 of 2 subviral particles- infectious agents related to viruses). Prions, as opposed to viruses, do not contain any genetic material.
how do prokaryotes differ from eukaryotes?
Proks lack a nucleus (they have a single circular, double stranded DNA instead and combines with RNA and proteins to for the nucleoid). They have no complex, membrane bound organelles. They have some organelles like ribosomes (proks are smaller than euks tho) but not COMPLEX ones like ER or golgi.
evolution of the mitochondria
may have evolved from a symbiotic (mutually beneficial) relationship between aerobic prokaryotes and eukaryotes. Now only found in euks.
what is the difference between gram positive bacteria and gram negative bacteria (structurally)?
the peptidoglycan (which makes up the cell wall and is the layer between plasma membrane and bacterial envelope) is copious and on the outside for gram positive, whereas gram negative the cell wall is thinner and on the inside of the plasma membrane (has 2 plasma membranes). The cell envelopes of gram-negative bacteria have more layers than those of gram-positive bacteria (Lipopolysaccharide is found in an outer membrane layer which is only in gram negative).
what is gram staining for bacteria?
Bacteria are tested for Gram-positive / negative through a series of two dyes – first purple, then pink. Gram-positive bacteria will hold on to the first stain, staining the organism purple. Gram negative will wash off and be stained pink.
Archaea
Archaea are the most common extremophiles (organisms capable of surviving in extreme environments such as increased heat or lack of oxygen)
Which of the following is NOT found in both prokaryotes and eukaryotes? Ribosomes, nucleous, cytoskeleton, double-stranded DNA?
nucleolus. A nucleolus, while not a membrane-bound organelle itself, is a region within a nucleus responsible for ribosome production. It is only found in eukaryotic cells.
Why are the systemic effects of gram negative bacterial cells considered worse than gram positive?
Gram-negative bacteria are considered to be more dangerous, because components of the outer membrane make them more resistant to antibiotics and the host’s immune system. Additionally, the lipopolysaccharide found in its outer membrane is an endotoxin that damages the host.
Genetic recombination
Genetic recombination leads to the creation of an organism with DNA that differs from its parent organism.
Binary fission
Binary fission is a form of asexual reproduction, which creates two cells identical to the original. Binary fission is not a genetic recombination technique employed by bacteria.
Lactose
dimer of galactose and glucose
Conjugation
Conjugation is a method of genetic recombination employed by bacteria to help transfer genes that can confer some sort of advantage, like antibiotic resistance. This means that there is a selective advantage to the original cell retaining the advantageous DNA.
Where does energy production take place in bacteria that can perform aerobic metabolism?
Bacteria, like eukaryotes, rely on a concentration gradient to drive an ATP synthase molecule. Energy production in bacteria takes place across the plasma membrane, with the gradient between the extra- and intracellular environment providing the appropriate concentration gradient.
Pili
Pili are primarily used to transfer DNA between bacteria during conjugation, but do have a small amount of motile function.
Lysogenic viruses
Lysogenic viruses have a dormant period. This means that although they are being replicated by the host, their virulence will not be expressed for some time. Because their virulence is temporarily repressed, a lysogenic virus would not act so quickly upon infection.
Lytic Viruses
Lytic viruses do not have a dormant or latent phase. In other words, they are fast-acting and cause immediate damage to the host cells. All lytic viruses destroy the cell while lysogenic viruses may be replicated with the cell.
what is the order of the layers on bacteria separating cytosol from external environment ?
cytosol–>plasma membrane–> cell wall –> (another plasma membrane if it’s gram - bacteria)–> capsule
lipopolysaccharides
long chain of CHO that protrudes outwards from the cell in gram (-) bacteria. They form a protective barrier from antibodies and many antiobiotics. It’s located between outer plasma membrane and capsule.
chemotaxis
the directed movement towards substances that will promote the survival and growth of the bacterium. The flagellum does this using a proton gradient (not ATP like euks)
binary fission
how bacteria reproduce, a form of cell division/asexual reproduction. It results in two genetically identical daughter cells.
3 forms of genetic recombination for bacteria (alternative to sexual reproduction)
conjugation, transformation, and transduction
binary fission steps and result
2 DNA polymerases begin on the circular DNA at the same point (origin of replication) and move in opp directions making complimentary single strands that combine with their template to form two complete DNA double stranded circles. The cell then divides, ending with one circular chromosome in each daughter cell that are genetically identical.
exponential growth of bacteria
each organism produces two offspring, which then each produce two offspring. They produce with little to no parental care until essential nutrients of the environment are gone.
how are mitochondria similar to what type of bacteria?
mitochrondria are similar to gram - bacteria cuz they have both have two membranes and protons in their intermembrane space
conjugation
transfer of a plasmid only by some bacteria (which are small circles of extragenomic DNA, meaning they exist and replicate independently from the bacterial chromosome and aren’t essential to the life of bacteria that carry them - looks like another circle inside the cell but separate from the circular dna. a plasmid can insert into the chromosome to become an episome). Conjugation transfers genetic material (one strand of the plasmid, which is then replicated once in the new cell) from one bacteria to another by direct contact. Conjugation always goes from F+ –> F- bacteria. So conjugation gives the F- bacteria the fertility factor, aka after “mating” with F+ it has the genes to encode the F+/ sex pilus.
why can only some bacteria with plasmids conjugate and not all?
the bacterium needs to have a conjugative plasmid (basically the genes that make the sex pilus)
sex pilus
hollow protein tube that connects two bacteria to allow the transfer of a plasmid from one bacterium to the other
two types of bacterium plasmids
F plasmid (fertility factor, or f factor) and R Plasmid (for resistance to antibiotics)
F plasmid
Fertility plasmid codes for the sex pilus (if bacteria has this, then it’s F+; if bacteria doesn’t have f factor, then it’s F-)
