bacteria Flashcards
model organism for bacteria
E. coli
gram negative
rod shaped
properties of prokaryotes
do not contain nucleus
1-5 microns in length, but various shapes
complex cell wall = tough protective coat
organotrophic
can utilise any type of molecule as food (sugars, amino acids, hydrocarbons etc)
phototrophic species
harvest light energy in various ways
lithotrophic species
inorganic nutrients
fixes C from CO2
relies of H2S to fuel energy needs
two families of prokaryotes
archaea
bacteria
where is DNA located in prokaryotes?
in the cytoplasm, typically as a single haploid circular chromosome, enclosed by the plasma membrane
also contains RNA/proteins and other small molecules
what is a plasmid?
an additional piece of circular DNA that is separate from the chromosomes
can be lost if no longer needed
eg. for genes that confer advantages like antibiotic resistance
flagella vs pili
flagella for movement by helical rotation
pili = short protein appendages, smaller than flagella, for adhesion, but some can generate force
both anchored to cell surface by multi protein complexes
define pathogenic
causing disease
how do pathogens differ from other bacteria species?
they have additional virulence genes that confer their pathogenicity, either on a separate plasmid or integrated into the chromosome
features of a gram positive cell wall
single membrane
thick cell wall made of cross linked peptidoglycan
features of a gram negative cell wall
two membranes (inner/outer) separated by a periplamic space
thin peptidoglycan wall
inner membrane = phospholipid bilayer
outer membrane = LPS (lipopolysaccharide), can be fever-causing
a gram staining procedure will dye which type of bacteria?
gram POSITIVE bacteria - thick peptidoglycan cell wall retains violet dye
examples of gram positive and negative bacteria
positive: staph, strep
negative: E coli, Salmonella
describe the capsule / slime layer
glycocalyx
= polysaccharide external layer
prevents phagocytosis (complement can’t penetrate sugars)
helps bacteria adhere to surfaces
what are endospores?
intracellular spores - highly resistant structure
some gram positive bacteria produce this as a survival mechanism
define the microbiome
The collection of all microbes, such as bacteria, fungi, viruses, and their genes, that naturally live on our bodies and inside us
3 key functions of the microbiome
- digesting fibre
- protect against pathogens
- immune response
plant cells: three major differences from animal cells
tough cell wall
chloroplasts
vacuoles
define choloplasts + basic structure
organelles that capture energy of sunlight in plant cells
highly folded system of internal membranes containing chlorophyll molecules which absorb light
origin of chloroplasts
endosymbiotic event (similar to mitochondria)
early eukaryotic cell engulfed photosynthetic bacteria and retained it in symbiosis
products of photosynthesis
ATP and NADPH
how are the products of photosynthesis used by chloroplasts?
ATP and NADPH used in electron transport chain for the carbon fixation cycle (this stage is known as the Calvin Cycle)
(note this is the light cycle - chloroplasts also have a dark cycle)
what makes up most of plant cell walls?
cellulose, a polysaccharide
long fibres oriented along lines of stress
hence the cell wall is tough but not rigid
structure of the plant cell wall
cellulose forms microfibrils, which are interwoven with other structural proteins (eg. in wood, lignin)
primary cell walls can expand to accomodate growth
what is turgour pressure?
a swelling pressure that develops as the result of an osmotic imbalance between the interior of the plant cell and its surroundings
(keeps lettuce leaf crisp)
