Topic 2 Flashcards
(36 cards)
prokaryotes cell walls
murein
gram positive
structure
stain
example
thick layer of peptidoglycan in cell wall
stained purple/ blue
Staphyloccocus releases exotoxins
gram positive antibiotics
Beta-lactam antibiotics are effective as they inhibit enzymes involved in peptidoglycan layer formation e.g. penicillin
gram negative
structure
stain
example
thin layer of peptidoglycan between two layers of membrane
stain red
Salmonella releases endotoxins
gram negative antibiotics
Polypeptide antibiotics are effective as they interact with the phospholipid membrane and unable to cross thick peptidoglycan layer so not effective on gram positive
cigarette smoke damages cell membrane structure
made up of phospholipid, channel proteins and carrier proteins
affects transport of non-polar molecules e.g. O2
affects endocytosis and exocytosis
damage to channel/ carrier proteins alters shape and affects facilitated diffusion, transport of ions, polar molecules
damage to carrier proteins affects active transport
allows lysozymes to escape
measuring cells
calibrate an eye piece graticule using a stage micrometer
measure length
more than one measurement taken
DNA virus
example
DNA template for new DNA and mRNA
E.g. λ phage
RNA virus
Both have a helical capsid
Positive ssRNA with helix structure
Sense strand can translated directly and templates for mRNA forming new viral protein
E.g. tobacco mosaic virus
Negative ssRNA with helix structure, envelope
Antisense strand must be transcribed to a sense strand before being able to translated to template for mRNA forming new viral proteins
E.g. ebola virus
RNA retrovirus
Envelope
RNA synthesises the enzyme reverse transcriptase to convert DNA into RNA and new viral proteins which leaves the host cell by exocytosis
E.g. HIV
Lytic cycle (4)
- Bacteriophage ATTACHES TO A BACTERIAL and its DNA is injected into the host cell, stimulating the synthesis of viral enzymes
- Phage DNA inactivates the host DNA and takes over the cell biochemistry to REPLICATE PHAGE DNA
- Protein coats form around phage DNA to form NEW PHAGE PARTICLES
- Lysozyme is synthesised and released causing the bacterial cell to burst (LYSIS) and release many bacteriophages to infect other bacteria
Lysogenic pathway (latency) (4)
- Bacteriophage attaches to a bacterial cell and its DNA is injected into the host cell, stimulating the synthesis of viral enzymes
- Viral DNA is incorporated with host cell DNA so it divides when the host cell DNA divides
- Protein coats form around phage DNA to form new phage particles
- Lysozyme is synthesised and released causing the bacterial cell to burst and release many bacteriophages to infect other bacteria
how do antivirals work (2)
inhibiting virus replication
Target receptors of virus used to recognise host cells
Target enzymes involved in translation and replication of new viral DNA/ RNA
how do viruses work
Lysis of host cells
Protein coat can act as a toxin
Some virus cause host cells to make toxins
why is mitosis useful
for growth/ repair of cells
requires genetically identical cells
interphase
G1: Time between cytokinesis and chromosome duplication
S: DNA synthesis so amount of chromatin doubles forms new chromatids (same number of chromosomes) and spindle proteins are synthesised
G2: Organelles and other materials double (by protein synthesis)
prophase
Chromosomes become visible as they shorten and thicken
Centrioles move to opposite poles of the cell and spindle fibres develop
Nuclear envelope breaks down leaving chromosomes free in the cytoplasm
metaphase
Spindle fibres attach to the centromere of every chromosome so they line up across the equator of the spindle
anaphase
Centromere splits so sister chromatids divide, spindle fibres contract and pull chromatids to opposite poles
telophase
Chromosomes group together at each pole and a nuclear envelop forms around each group so nuclei are present
Chromosomes decondense to form chromatin, spindle fibres break down
cytokinesis
cytoplasm splits to form two genetically identical daughter cells
advantage of meiosis
genetic variation enables species to survive changes to the environment
enables contribution of alleles from two individuals
independent segregation
in metaphase I, random arrangement of maternal and paternal chromosomes from homologous pair go to either two new cells forms new combinations of maternal and paternal chromosomes
crossing over
in prophase I, exchange of alleles between non-sister chromatids forms new combinations of alleles
homologous chromosomes pair up, chiasmata form, break in chromatid, genetic information exchanged between chromatids
