112 Flashcards
define prokaryotic cell
Most abundant type of cell on earth
Do not have membrane bound nucleus
Divided into 2 domains; bacteria and archaea
where do archaea live
very extreme conditions usually
shapes of bacteria
cocci- spherical
bacilli- rod
spirochetes- helical
what protein is in prokaryote flagella
flagellin
what are prokaryotic pili composed of
protein pilin and help bacteria stick to their substrate or to each other
what domain contains nuclear envelope
eukarya
what domain contains membane-enclosed organelles
eukarya
what domain contains peptidoglycan in cell wall
bacteria
whats the inititator amino acid for protein synthesis in bacteria
Formyl-methionine
bacteria’s response to the antibiotics streptomycin and chloramphenicol
growth is inhibited
do bacteria have histones associated with DNA
absent
Gram + peptidoglycan layer
thick
gram - peptidoglycan layer
thin layer
gram + cell wall structure
simple, single layer
gram - cell wall structure
complex, double layer
gram + teichoic acid
present
gram - teichoic acids
absent
gram + lipopolysaccharide
absent
gram - lipopolysaccharide
present
gram +, gram stain
purple
gram -, gram stain
pink
gram + antibiotic resistance
susceptible
gram - antibiotic resistant
resistant
gram - examples
chlamydia trachomatis
yersinia pestis
vibrio cholerae
gram + examples
clostridium tetani
clostridium botulinum
streptococcus pnuemoniae
medical uses of bacteria
produce large quantities of proteins cheaply for therapeutic use for example insulin
drug screening tests and diagnostics for example beta amyloid
agricultural uses of bacteria
introduction of a new gene in plant chromosome
e.g. purple tomatoes have high anthocyanin
environmental uses of bacteria
bioremediation- removes pollutants, industrial by-products, oil spills
industrial uses of bacteria
lactic bacteria develop the flavour and colour of foodstuff
improve the storage longevity of wines
photoautotrophs
photosynthesis organisms which us light to synthesize organic compounds from carbon dioxide
chemoautotrophs
use carbon dioxide as a carbon source and obtain their energy by oxidising inorganic substances e.g. from hydrogen sulphide. This mode is unique to certain prokaryotes
photoheterotrophs
use light to generate ATP but must obtain their carbon in an organic form, this type is unique to certain prokaryotes
chemoheterotrophs
use organic molecules to supply both carbon and energy
can viruses self repair
no
do viruses have an energy transduction system
no
how can you view viruses
only visible with the electron microscope
are viruses alive
no
virion
each complete viral particle is called a virion
capsid
protein coat- made up of proteins called capsomers
filamentous viruses
The nucleic acid is arranged in a helix , with the protein sub-units surrounding and stabilizing it. An example is Tobacco mosaic virus
spheroid viruses
The nucleic acid is condensed inside a protein envelope which is usually organized into a multisided geometric shape. An example are adenovirus different types cause illness ranging from Gastroenteritis to keratoconjunctivitis
tailed spheroid virus
This is basically a spheroid virus with a tail. An example is the lambda phage
Enveloped viruses
Have lipid envelopes includes the influenza and coronaviruses viruses
resolution
measure of the minimum distance of 2 distinguishable points
contrast
visible difference in brightness or colour between parts of the sample
how to improve resolution
use a shorter wavelength radiation
advanced light microscopy
- permits observation of transparent living cells
-light phases shifts induced by specimen are used to generate contrast
-phase contrast ( refracted and unrefrected light)
-differential interference contrast ( 2 light beams )
fluorescence microscope
-shows location of specific molecules in the cell
-fluorescent substances absorb short-wavelength, ultraviolet radiation and emit longer-wavelength, visible light
phase contrast microscopy
enhances contrast in unstained cells by amplifying in density within specimen- usually useful for examining living unpigmented cells
differential-interference-contrast (nomarski) microscopy
like phase-contrast- uses optical modification to exaggerate difference in density
confocal microscopy
uses lasers and special optics for ‘optical sectioning’
only those regions within a narrow depth of focus are imaged
regions above and below the selected plane of view appear black rather than blurry.
usually used with fluorescently stained specimens
transmission microscope
electron gun- tungsten filament
beam passes through specimen
focused and magnified by magnetic objective and projector lenses
visible image by a fluorescent screen
photographs taken using digital camera
high vacuum
scanning microscope
electrons scanned across specimen
electrons reflected and collected by electron detector and converted into an electronic signal which is displayed on a screen
gives 3D appearance
transmission preparation
-Whole mounts: Bacteria and viruses can be examined directly Tissue sections
-Fixation: Usually in Glutaraldehyde (protein crosslinking) followed by a second fixation step in Osmium Tetroxide (lipid crosslinking)
-Dehydration: In an ethanol series
-Embedding: Specimens for TEM are embedded in plastic resins such as Epoxy resins.
-Sectioning: 50nm thick sections are cut using a ultramicrotome.
-Staining: Biological tissue has little contrast under the electron beam, so heavy metal stains such as lead are used to improve contrast
scanning preparation
-Biological samples must be fixed and dried before being examined in the SEM under vacuum
-Fixation: The same fixatives are used as with TEM preparation
-Dehydration: The water is replaced with Ethanol
-Critical Point Drying: This technique allows all of the ethanol to be removed from the sample in a way that minimises shrinkage
-Coating Specimens are coated with a thin layer of gold to protect them from electron beam damage
nucleus
Largest organelle, contains most genes which control cell, nuclear membrane encloses the nucleus separating it from the cytoplasm which is doubled membraned and contain pores about 100nm in diameter, within nucleus also have the DNA organised into chromatin
plasma membrane overview
contains cell- separating the cell from its external environment and controls the entry and exit of nutrients/ waste products
impermeable barrier to most water-soluble molecules
how are lipid and protein molecules held together in plasma membrane
non-covalent interactions (fluid mosaic)
Lipids are amphipathic molecules which will spontaneously form bilayers in an aqueous environment- true or false
true
if damaged the lipid bilayer isn’t able to repair itself- true or false
false- it can repair itself
lipids constitute about half of the mas of biological membranes - true or false
true
3 major types of lipids in cell membrane
phospholipids
cholesterol
glycolipids
what does cholesterol in plasma membrane do
increase stability of membrane
at warm temperatures it restrains movement of phospholipids
without it PM cannot function properly
freeze fracture electron microscopy
observes the shape and distribution of proteins
studies the PM supported the fluid mosaic model
is a specialised preparation technique that splits a membrane along the middle of the phospholipid bilayer
receptor sites
the exterior region of transmembrane protein may act as a receptor for chemical messenger such as a hormone or growth factor
structural roles of membrane proteins
membrane proteins called integrins allow the cell to attach to the extracellular matrix
cystic fibrosis
-Caused by a defective chloride ion channel
-Autosomal recessive disease
-Failure of this chloride channel results in build up of viscous mucus within lungs making it hard to breath and prone to infections
-Appears to be ideal disease to treat with gene therapy but progress has been much slower than expected
forms of carbohydrates in PM
oligo and polysaccharides bound to membrane proteins as glycolipids
what % of membrane mass do carbs take up
10%
whats glycocalyx
Glycocalyx consisting of thin layer of carbohydrate is present on the outside of the plasma membrane of most cells
The ABO blood types are determined by carbohydrates in the surface of the red blood cells
true or false
true
Membrane glycoproteins are not involved in infection mechanisms
true or false
false
they are involved- e.g. with HIV
endocytosis
material taken into cell
pinocytosis
cells pinch their PM to take up extracellular fluid in small vesicles, non specific
receptor mediated endocytosis
binding of macromolecules to specific cell surface receptors which triggers endocytosis. clatherin is the protein that forms cage-like structures to allow endocytosis
clatherin
the protein that forms cage-like structures to allow receptor mediated endocytosis
what is the endomembrane system composed of
nuclear membrane, the endoplasmic reticulum, golgi apparatus and the lysosomes
most cells have relatively little SER
true or false
true
where is SR found
in muscle cells
SER- functions
Phospholipid, fat and steroid manufacture
carbohydrate metabolism
in hepatocytes, breaks down stored glycogen to release glucose
detoxifies lipid- soluble drugs such as barbiturates
in SR (sarcoplasmic reticulum) what does the level of calcium regulate
muscle contraction in muscle cells
SR overview
-Network of tubular sacs
-Sequesters calcium ions from cytosol
SR leading to muscle contraction
-Action potential triggers SR to release ca into cytosol
-Ca ions bind to tropomysin and troponin leading to a conformational change
-Myosin now interacts with actin and the muscle contracts
what does the N-terminus contain on ribosomes that are attached to RER
contains a signal peptide usually 20-30 amino acids long
SRP ?
signal recognition particle
it attaches to signal peptide and stops translation in the cytosol
to start translation again the SRP docks to a SRP receptor on the ER membrane
hows the RER membrane cleaved of
The hydrophobic signal peptide passes through the membrane and loops back through the membrane and is cleaved off . The rest of the peptide passes through the membrane and into the ER lumen
The signal sequence is cleaved off with the enzyme signal peptidase
polyribosome
an mrna molecule translated simultaneously by several ribosomes in clusters
what does golgi apparatus do
modifies and sorts proteins,
Golgi also mediates the flow of proteins from the RER to destinations
- Principle modification which occur to proteins
- Essential for their function e.g. mucin produced by glycoproteins with long highly oligosaccharide chains are essential to produce hydrated gel like material
default pathway for golgi and stuff
= protein synthesis in RER = through the golgi = then to plasma membrane
Some proteins are tagged in golgi for certain destinations, a mannose 6-phosphate receptor then binds these proteins in the trans golgi reticulum and directs transfer to the lysosomes
how many hydrolytic enzymes does the lysosomal system have
- Contain 60 hydrolytic enzymes which biodegrade almost all biomolecules (made in RER)
where do primary lysosomes originate from
trans face of the golgi
what happens when lysosomes fuse with target
-When lysosomes fuses with a target, H+ pumped into the secondary lysosome to bring down the pH and activate the enzymes
-Lysosomes carry out phagocytosis
-Carry out autolysis during apoptosis
what did Yoshinori Ohsumi win
The Noble Prize medicine award in 2016 went to Japanese biologist Yoshinori Ohsumi for discoveries on autophagy, the process by which a cell breaks down and recycles content
lysosomal storage diseases
-Partially degraded insoluble metabolites can accumulate within lysosomes if a particular lysosomal enzymes is defective
-The resulting material results in enlarged lysosomes that compromise cell function in over 50 different lysosomal storage diseases
Tays- Sachs disease
in Tay hexosaminidase A enzyme deficiency results in the accumulation of the lipid ganglioside, clinical symptoms are due to this ganglioside in nerve cells, death usually occurs by 2-3 years of age
outer membrane of mitochondria
-Very similar to other eukaryotic membranes
-Major protein component is porin- large aqueous channels
inner membrane of mitochondria
-Contain 3 membrane complexes
ETC
ATP synthase
Specific transporters of metabolites which vary according to cell/tissue type
cristae
-Increase membrane surface area energy
-Energy transducing membrane
-Impermeable to most small ions
matrix mitochondria
-Enzymes which catalyse Krebs cycle and fatty acid oxidation
-Ribosomes
-Mitochondrial DNA
Electrons in C-H bonds are higher energy than those in C-O or H-O bonds
true or false
true
how does cellular respiration release energy to surrounding
The reaction releases energy to the surroundings because the electrons lose potential energy when they end up being shared unequally, spending more time near electronegative atoms such as oxygen
glycolysis overview
During glycolysis each glucose is broken into 2 molecules of pyruvate, pyruvate then enters the mitochondrion, takes place in cytosol and only releases little energy stored in glucose (through substrate level phosphorylation) and most of the energy remains in the 2 pyruvate molecules
ATP produced in 2 steps but also used up at 2 steps
High energy electrons passed onto electron carrier NAD+ to generate NADH
where does glycolysis occur
cytosol
how much ATP produced in glycolysis
produced in 2 steps but also used up in 2 steps
link reaction overview
Pyruvate is transported into the mitochondrial matrix through a transport protein
Looses CO2
NAD+»_space; NADH + H+
Coenzyme A
Produces Acetyl CoA
what does link reaction produce
acetyl CoA
NADH
ETC overview
*High energy electrons passed into electron transport chain
*Stepwise extraction of energy from high energy electrons
*Each component of the chain is slightly more electronegative than the previous
*Passed onto oxygen to generate H2O
*FADH2 passes on electrons at slightly lower stage than NADH
*No ATP is made directly
*Energy used to produce a H+ gradient across the inner mitochondrial membrane
F0 portion of ATP synthase
is a H+ channel
F1 portion of ATP synthase is
head is site of ATP synthesis
what does movement of H+ through F0 cause
- causes rotation of the rotor and central stalk, while the stator keeps the enzymatic F1 stationary
- forces sequential conformational changes in the central stalk and F1
- provides the energy for ATP synthesis
in ATP synthase how many ATP molecules are generated from 10H+ moving back into matrix
around 3
cyanide as a mitochondrial poisen
prevents the passage of electrons from one of the cytochromes thereby blocking the ETC, might be fastest poison known to man
DNP (2,4-dinitrophenol) as mitochondrial poison
make inner membrane leaky to H+ so that a gradient cannot be established for the ATP synthase , ETC still works but energy is released as heat- essential burning victim alive from inside out
MERRF- myoclonic epilepsy and aged-red fibre disease
genetic- mutation in mitochondrially encoded tRNA Lys gene
affects translation of mitochondrially encoded proteins, abnormal morphology, multisystem disease affecting muscles/nerves (hence the epilepsy)
no cure
the cytoskeleton isnt present in every cell
t/f
false- it is present in every cell
the cytoskeleton has - Important vital functions- muscular movement to transport molecules, normal embryonic development]
t/f
true
abnormalities in the cytoskeleton dont always lead to disease affecting every tissue in the body
t/f
false- can result in disease in every tissue in the body
do many current drugs work by targeting the cytoskeleton
yes
microfilaments
about 7nm in diameter and composed of 2 actin chains twisted around each other, have a variety of structural and locomotor functions
microtubules
straight hollow rods 25nm in diameter and up to 20 microns long, and are constructed from globular proteins called tubulins
intermediate filaments
8-12nm in diameter and are made up of diverse group of proteins, tend to be permanent fixtures and important in maintaining cell shape and position of certain organelles
the 3 components of the cytoskeleton
-microfilaments
-microtubules
-intermediate filaments
adherens junction
cadherins
extracellular - transmembrane
connects cells to actin filaments intracellular signalling regulator
focal adhesions
connect ECM to actin filaments
integrins
desmosomes
-Cadherins
-Connect cells to intermediate filaments
-Structural integrity, withstand mechanical stress
-Important in cardiac tissue- interlated discs
hemi-desmosomes
integrins
connect ECM to intermediate filaments
spot-desomosomes
-Spot welds together
-Attached on inside of cell to keratin filament, which serve to spread the stresses from the spot desmosome throughout the cell
tight junction- 2 functions
barrier/gate
fence
barrier/gate function in tight junction
prevent molecules from leaking between adjacent cells
fence function in tight junctions
separate the apical plasma membrane from the basal plasma membrane, allowing different compositions
also gives rise to cellular polarity
