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semester 2 biology test revision - Coggle Diagram
semester 2 biology test revision
microbiology
Structure and fucntion of prokaryotic cells
capsule
outermost protective layer outside of the cell wall of a prokaryotic cell. often sticky to help the cell adhere to other cells and surfaces
cell wall
an outer layer of the cell surrounding and containing all components of the cell (often surrounded by a capsule in prokaryotes)
cell membrane
a thin membrane surrounding the cell inside of the cell wall
fimbriae
shorter bristle hair like structures on the outside of the cell, helping the cell stick to surfaces and produce biofilm
pili
longer hair-like appendages on the outside of the cell that assist in movement of the cell and transfer of genetic information during conjugation. many genes such as antibiotic resistance may be transferred via pili
plasmid
extra-chromosomal non essential DNA formed in a ring. carries genetic modifications such as antibiotic resistance
nucleoid
irregular shaped region containing chromosomal DNA from the cell. unlike the nucleus, it is not surrounded by a membrane
transfer of genetic material
transduction
the transfer of chunks of chromosomal dna from one cell to another via bacteriophages
bacteriophages- viruses that infect bacteria and use the cell's resources to multiply
transformation
taking in of genetic information from the bacterium's external environment, usually shed by other bacteria. if the dna is incorporated into the plasmid, this dna may be passed on to descendants
conjugation
the transfer of dna via a plasmid or hybrid of chromosomal dna and plasmid dna via the pili. the pili allow two cells to pull each other closer and transfer the F+ inheritance gene to the recipient cell. This allows the recipient to be able to grow its own pili and transfer genetic information
pathogenic vs non pathogenic bacteria
pathogenic: causes disease symptoms, symbiotic relationship it forms with the host is harmful
non-pathogenic: not inherently disease causing but may become pathogenic when host's immunity is low or secondary infection occurs
methods of transmission
airborne: certain pathogens may be transferred via air from the host through actions such as coughing or sneezing
vectors: pathogens may be transmitted through intermediary organisms that don't develop symptoms themselves but are still capable of transferring the virus e.g. insects
contamination: ingestion of pathogens growing in or on edible food sources
direct contact: transfer of pathogens via physical contact or exchange of bodily fluids
conjugation in the assistance of antibiotic resistance
conjugation allows traits such as antibiotic resistance to be shared between bacteria via gene transfer, allowing them to evolve and pass this trait on to [descendants]
antimicrobial agents and aspetic technique purpose
aseptic technique use in the classroom
examples: washing/sanitising equipment and bench surfaces before and after use, wearing ppe such as gloves, sanitising and washing hands
antimicrobial agents are chemicals that work to restrict the growth of or destroy bacteria
aseptic technique refers to methods used to avoid contamination when working with bacteria to keep ourselves and others safe from potentially harmful bacteria
quantifying agar: zone of inhibition
the zone of inhibition is the circular area around an antimicrobial agent that inhibits the growth of bacteria and can be measured to find susceptibility of bacteria to antimicrobial agents
DNA
functions
protein synthesis
translation
anticodons are carried by tRNA (transfer RNA) and are covalently linked to specific amino acids
codons
carried by mRNA, correspond to specific anticodons on tRNA
the reading frame refers to the arrangement of nucleotides into codons to be read for protein synthesis
1) the mRNA enters the ribosome, the small ribosomal unit binds to the mRNA and a corresponding tRNA, which will be covalently linked to methionine, which signifies the start of protein synthesis
2) the large ribosomal unit joins to complete the translation initiation complex, the next codon is read and the corresponding tRNA enters the ribosome, while the last used tRNA leaves to make room. however, the amino acid on the new tRNA links to the starting methionine, even when that tRNA leaves the ribosome the amino acid is linked so it creates a growing polypeptide chain of amino acids as tRNAs enter and exit the ribosome until a stop codon is reached
3) this chain then leaves the ribosome and may go to another cell organelle for further modifications or use
transcription
occurs in the nucleus
4) the product is mRNA, which is small enough to fit through the pores of the nucleus and enter the cytoplasm and then a ribosome, where translation will occur
1) RNA polymerase attaches itself to a specific sequence on the DNA chain called the promoter and begins elongation, untwisting and unzipping the DNA strand
RNA polymerase does not require a primer
2) it then works its way down the DNA strand, synthesizing mRNA by attaching corresponding nucleotides and simultaneously unzipping and then rezipping the strand back up as it goes, ensuring only 10- 20 base pairs are exposed at one time. the RNA polymerase reads the anti-sense strand or template strand in the 3'-5' direction, constructing mRNA in the 5'-3' direction.
3) termination then occurs, the enzyme detaches from the DNA and it is returned to its former state.
replication
1) the enzyme DNA helicase pries apart the two strands from each other like a zipper- a leading strand (5'-3') and a lagging strand (3'-5')
2)
RNA/DNA primase then goes along both strands and creates a starting point for DNA polymerase to go along the strand and attach matching nucleotides to each strand. RNA primase is only needed once on the leading strand as DNA polymerase and the leading strand run in the same direction, meaning it can smoothly go along the strand in one go. However, RNA primase must create several starting points on the lagging strand as it goes in the opposite direction to DNA polymerase, meaning the lagging strand must be synthesized in short burst, creating segments called okazaki fragments
3) another polymerase goes along the strands and replaces all the RNA primase
4) an enzyme called DNA ligase goes along and joins all the okazaki fragments together
structure- double helix
complementary base pairs
adenine & thymine, cytosine & guanine
joined by hyrdogen bonds- A& T form two bonds, C & G form 3
repeating polymer- nucleotides
three components of a nucleotide- phosphate group, pentose sugar, nitrogenous base
stable arrangement- the arrangement of the two strands running in opposite directions to each other (5'-3' and 3'-5')
genes definition- genes are long portions of chromosomal DNA generally 10, 000-50, 000 base pairs long that code for specific traits or proteins/groups of proteins
chromosomes- entire chains of DNA with a group of stabilizing proteins, wrapped around a protein called histones to form a bundle. chromosomes generally exist in an unravelled state inside the nucleus and only condense to make transfer during cell replication easier
type of nucleic acid- deoxyribose nucleic acid
other type- ribose nucleic acid (RNA)
RNA- single stranded structure, shorter and smaller, able to slip out the pores of the nucleus after transcription
RNA base pairs- adenine & uracil, cytosine & guanine
cell division
binary fission
replication of DNA
cell elongates, separating the DNA
cross wall starts to form, membrane invaginates, forming a septum
cross wall forms completely
daughter cells are genetically identical
mitosis
plant cells
plant cells do not change shape before undergoing mitosis, and do not contain centrioles to assist the mitotic spindle, which does not contain asters either.
cytokinesis in animal cells occurs by the formation of a cell plate down the middle of the cell, which consists of plasma membrane and other cell wall parts, separating two daughter cells
animal cells
animal cells become more rounded before mitosis
cytokinesis occurs in animal cells as contractile cytokinesis, a ring-like filament structure called the contractile ring pinches the cell in two, producing an indentation called the cleavage furrow to produce two new daughter cells
prophase
chromosomes start to condense, mitotic spindle begins to form
mitotic spindle- a structure composed of microtubules that forms between centrosomes as they move apart to opposite ends of the cell. microtubules can bind to the centromere on chromosomes on the kinetochore- a patch of protein on each side of the centromere. microtubules that don't bind to kinetochores grab onto microtubules from the opposite side to stabilise. more microtubules extends towards the edge of the cell, forming the aster
prometaphase
mitotic spindle captures chromosomes and starts to organise them, nuclear envelope breaks down and releases chromosomes
metaphase
chromosomes are all captured and aligned at the metaphase plate. the spindle checkpoint occurs, checking all kinetochores are attached to microtubules from opposite poles of the cell
anaphase
sister chromatids are separated and pulled to opposite poles of the cell, the microtubules not attached to chromosomes elongate, making the cell longer
telophase
cell starts to re-establish structures, mitotic spindle breaks down, nucleus and nuclear membrane starts to reform for the two new daughter cells, chromosomes start to de-condense cytokinesis begins
eukaryotic vs prokaryotic cell replication
eukaryotic cells divided through either mitosis for all somatic cells or meiosis for sex cells, which are both asexual reproductive processes
prokaryotic cells divide through binary fission, asexual reproduction
experimental skills
independent variable on x axis