Physiology Flashcards
name the components of the nuclear pore
nuclear basket
nuclear ring
cytoplasmic filaments
cytoplasmic ring
name what enters the nuclear pore and what exits it
enter: ribosomes, materials for DNA/RNA synthesis, molecules used to provide energy
exit: ribosomal sub-units,
what is the NLS and the NES, and what purpose do the serve
nuclear localisation signal is an amino acid sequence that tags proteins for entry
nuclear export signal tags proteins for exit
allows distinct protein populations between nucleus and cytoplasm
the signal amino acid sequence usually contains what sequence of amino acids
Poly A
What is the role of GTP in co-translational translocation?
phosphorilyses the SER when it it binds to its receptor to release the signal amino acid sequence into the trasnlocon
how is the translocon opened and what is the role of signal peptidase?
forms hydrophobic interactions with the translocon, and the peptide kinda just pushes through aswell.
where do O-links occur and what molecule reacts with specific amino acids to form them?
O-links occur exclusively in the golgi
oxygen with serine/threonine
where do N-links occur and what molecule reacts with a specific amino acid to form it?
N-links begin in the ER and finish in the golgi
nitrogen with asparagine
name the phospholipid heads
glycerol choline serine ethanolanine sphingolipids
How does a cis double bond in the fatty acid tail affect overall membrane fluidity?
increases fluidity
What are lipid rafts composed of?
cholesterol and sphingolipids
What can barely diffuse into the nucleus via diffusion in Daltons
50kda
What does the ER store and what is it used for?
Ca2+, cell signalling
What is the structure called when multiple ribosomes are bound to a single mRNA?
polysomes
Name the enzyme that catalyses the transfer of precursor oligosaccharide from dolichol lipid anchor
oligosacharyl transferase enzyme
What is the function of cardiolipin and where is it located?
makes membranes impermeable to ions
located in the inner membrane of the mitochondria
What are granules?
newly synthesised RNA
What oxidative enzymes do peroxisomes contain?
Catalase, urate oxidase
Why does the lysosome not self digest?
highly glycosylated proteins in its membrane
What is the most stable component of the cytoskeleton?
intermediate filaments
Where does alpha actin operate
skeletal muscle, smooth muscle, cardiac muscle
what is the difference between beta and gamma actin
beta actin - only operates in non-muscle tissue
gamma actin - operates in non-muscle tissue and smooth muscle tissue
Function of Arp2/Arp3?
Are forms of actin that cannot polymerise so they act as a primer for actin to bind to
Functions of thymosin/prolifin?
thymosin: binds to actin - inhibiting its polymerisation
prolifin: binds to actin but aids in its polymerisation
function of filamin homodimers
takes microfilaments and cross links them to form a network
Where do microtubules grow from?
gamma rings found on centrosomes
Name the 2 microtubule motors and which direction they travel in
kinesins - plus end
dyenisins - minus end
What does the cell check at the G2/M transition?
DNA
What is checked at the metaphase to anaphase transition?
spindle fibres are correctly attached to kinetichores
Function of CDc25?
dephosphorylises CDK-cyclin complex to activate it
Function of Myt1/wee1?
phosphorylises CDK-cyclin complex to deactivate it
How does CDK-cyclin progress the cell cycle?
CDK-cyclin removes proteins that sit on the promoter region to allow transcription and progression of the cell cycle.
What occurs if damaged DNA is detected in terms of MDm2-P53?
MDm2-P53 is phosphorylised, freeing P53, allowing it to bind to the regulatory region to synthesise CDK-inhibitory regions that destroy the CDK active site, halting the cell cycle
What 2 protiens act to form a chromatin loop?
Cohesin and CTFC
what happens during prometaphase
nuclear envelope breaks down
spindle fibres attach to kinetichores
how do spindle fibres connect to kinetichores
the microtubule’s plus end is facing the kinetichore
the kinetichore contains connecting proteins which form a collar around the microtubule
what happens to securin once all kinetichores are correctly attached to a spindle fibre and what does this mean for seperase
securin degrades which frees seperase, activating it
what is the function of seperase
cleaves cohesin which allows the cell to enter anaphase
what is the function of APC/C
ubiquinates cyclin B1, which degrades it, leaving only CDK1 - triggering mitotic exit
Ubiquitinates Securin
function of mitogens?
triggers a wave of G/S-Cdk activity that removes cell cycle inhibitors
purpose of a synaptonemal complex
binds 2 homologous chromosomes to form a bi-valent structure
where is the synaptonemal complex formed
the zygotene
where is the synaptonemal complex fully completed
pachytene
where does the disassembly of the synaptonemal complex occur
diplotene
what is chiasmata and when is it visible
crossing over of sections of chromatids along their locus
visible after synaptonemal complex disassembly
what is a proplastid
a pre-cursor of all plastids
what are chromoplasts
non-photosynthetic plastids
what is amyloplast
starch storage plastid
Difference between leucoplast and elaioplast?
leucoplast is involved in lipid synthesis whereas elaioplast stores mostly sterol esters
what percentage of chloroplast protein is encoded by the chloroplast itself?
10%
function of N-terminal transit peptides
target proteins encoded by the nucleus into the chloroplast.
What is functional syncitia and whats the purpose of it?
when cells are are fused together with gap junctions
allows cascading signal to affect the neighbouring cell
What is functional syncitia and whats the purpose of it?
when cells are are fused together with gap junctions
allows cascading signal to affect the neighbouring cell
What creates the impermeable seal of tight junctions?
occludin/claudin create seals with the neighbouring cell’s occludin/claudin
What are cadherins dependent on?
Ca2+
How do cadherins form anchoring junctions?
the bind to cadherins of the same type on the cell surface of a neighbouring cell which forms a dimer
How do proteoglycans provide a compressive strenght?
water absorption, the protein contains highly negatively charged sugars - draws in water
What does the high charge of proteoglycans give them as an extra function
acts as a binding site for many signalling molecules
where is laminin located and what does it form?
forms the basement layer in Bowman’s Capsule
Catecholamines are derived from what 2 amino acid residues?
tyrosin and tryptophan
Most hormones can be expressed as a 1:1 ratio, outline the equation demonstrating this
Kd = [H][R]/[HR]
What does Kd stand for?
concentration of hormone when half of the receptors are bound
What is the slope on a Scatchard’s plot?
1/Kd
inverse of Kd
How is maximum biokogical response achieved for insulin when only 2-3% of receptors are bound (nowhere near the Bmax)?
very potent amplification system
what is the difference between a tropic and a trophic hormone?
tropic hormones target endocrine glands - anterior pituitary
trophic hormones target non-endocrine glands - insulin
Where do nerves carry tropic hormones from and to?
hypothalamus to the anterior pituitary
What 2 receptors are involved in ADH regulation?
baroreceptors and osmoreceptors
Where are barorecptors located and how do they detect changes in blood pressure?
located in the aorta and detect change in plasma volume
Function of angiotensin II
regulates aldosterone synthase
What does zona glomerulosa release?
aldosterone
What does zona fasciculata/reticulata release?
cortisol
corticosterone
androstenedione
What does the Medulla release?
catecholamines
Function of ACTH
regulates 17alpha-hydroxylase
converts cholesterol into pregnenolone
What does 17 alpha-hydroxylase do to pregnenolone/progesterone
adds an OH group
hydroxypregnenolone/hydroxyprogesterone
Where is 17 alpha-hydroxylase located?
zona reticulata/fasciculata
Which product does not require 17 alpha-hydroxylase?
corticosterone
Since 17 alpha-hydroxylase is not present in the glomerulosa, it can only produce corticosterone, but what is this converted into?
aldosterone
How does a low filtration pressure in the Bowaman’s capsule lead to the release of renin?
low Na+/K+ detected due to low filtration pressure, leads to activation of juxta-glomelular cells to release renin.
Function of renin?
renin cleaves angiotensinogen into angiotensin I
what is the function of ACE
converts angiotensin I into angiotensin II
What detects the high blood pressure and what does it release
atrial muscle
ANF
function of ANF
inhibits renin formation
Function of aldosterone?
increases Na+ - increases water absorbtion - increases blood pressure
decreases K+/H+
ionic balance
When starving (low blood-glucose levels), what does the liver convert triglycerides into?
acetyl CoA then into:
acetoacetate or beta-hydroxybutyrate
Why does the liver then convert acetyl CoA into ketone bodies?
to be transported into other cells
acetyl CoA can’t
is converted back into acetyl CoA in the target tissue
How is glucose released from the body when when blood-glucose levels are too high?
in the urine
causes dehydration because water is then absorbed into the urine
What do both insulin and glucagon do?
they both induce uptake of amino acids by the liver
insulin for protein synthesis
glucagon for energy
If glucose does not enter cells in type 2 diabetes, what else is used as fuel?
lipids and amino acids
What is metabolic acidosis?
lipid conversion into ketone bodies - they are acidic
causes acetone breath
What hormone does the hypothalamus send to the anterior pituitary for hormonal action in males?
GnRH
What does the anterior pituitary send to steroli cells and leydig cells?
Function of leydig cells?
steroli cells - FSH
leydig cells - LH
leydig cells - convert androstenedione into testosterone
What produces dihydrotestosterone?
steroli cells
Where is FSH and LH sent to in female hormonal action from the anterior pituitary?
FSH - granulosa cells
LH - thecal cells
Function of FSH in females?
converts androgen into 17beta-estradiol
What phases of the cycle does ovulation occur
follicular and proliferative phase
What cycle stages does menses occur
luteal and secretory phase
Function of 17beta-estradiol?
promotes cell division of granulosa cells - uterus growth
promotes a positive feedback loop
What is the localised positive feedback loop in the granulosa cells?
17beta-estradiol increases the amount of FSH receptors on the granulosa cell, increasing the amount of androgen converted into 17beta-estradiol
What happens when FSH receptors are converted into LH receptors in the corpus luteum?
corpus luteum mass produces progesterone which is released in the blood and causes a negative feedback loop back at the hypothalamus - decreasing the amount of FSH/LH being released - leads to corpus luteum death
What is the placenta formed from
syncytiotrophoblast/cytotrophoblast
What forms the yolk sac
hypobast
What forms the embryo?
epiblast
What does syncytistrophoblast secrete.
hCG - human Chrionic Ganadotropin
What does hCG do?
performs many of the same functions as LH, also binds to LH receptors
The corpus luteum decreases the levels of LH so it will eventually die, but since human chrionic ganadotropin is released by the embryo, what does it mean if the corpus luteum is still alive?
pregnancy
congratulations
how long are fatty acids in terms of carbon
14-24 carbons
what is sphingomyelin derived from
sphingosine
which is the only phospholipid to carry a negative charge
phosphoatidylserine
do bacteria contain cholesterol and what do plants contain instead of cholesterol
no
related sterol compounds
what happens to membrane at low temperatures
less kinetic energy, so decreased fluidity
cholesterol increases spacing between phospholipids to increase fluidity
what happens to membranes at high temperature
increase fluidity due to increased kinetic energy
cholesterol pulls hydrocarbon tails (fatty acid tails) together to decrease fluidity
what does the endomembrane system include
vesicles golgi apparatus nuclear envelope plasma membrane endoplasmic reticulum
what are the 2 pathways through the Golgi apparatus
cisternal maturation
vesicle transport
how is the vesicular tubular cluster formed
COP II sheds to form a COP II coat which fuses to form the vesicular tubular cluster
function of KDEL receptors?
retrieve proteins back to the ER
what occurs at the cis golgi network
phosphorylisation of olligosaccharides on lysosomal proteins
what happens at the golgi stack?
removal of Man - manose
addition of Gal - galacatose
addition of NANA - N-acetylineuraminic acid/
addition of GlcNAc - N-acetylgloseamine
what happens at the trans-golgi network
sulfation of tyrosines and carbohydrates
what are the products when pyruvate is oxidised
CO2
H20
15ATP
where does NADH carry electrons to
inner membrane
in most organisms is mtDNA paternally or maternally inherited
maternally inherited
what is the difference between a type I and type II ribosome inactivating protein
type I cannot cross the cell membrane - non-cytotoxic
type II can cross the cell membrane due to a binding domain
what C-terminal amino acids form the peroxisome form its signal sequence
lysine, serine, leucine
what type of enzymes are the ones within a lysosome
acid hydrolases
function of endosomes
sort and deliver material to the lysosome/vacuole
what are the different protein sub-units of vault complexes
TEP1
VPARP
MVP
what are the potential functions of vault complexes
associated with nuclear pore complexes nuclear-cytoplasmic transport cell signalling mRNA localisation drug resistance
what is the structure of proteosomes
central hollow cylinder
4 stacked heptameric rings
core particle in between 2 regulatory particles
what happens when glomelular actin (G-actin) is phophsorylised
filamentous actin (F-actin) is formed
what is an actin filament comprised of
2 twisted F-actins
what frees gelsolin and what does this lead to?
PIP2
produces negative free positive ends for rapid actin polymerisation
what is the difference between alpha and beta tubulin
alpha-tubulin - has a bound molecule of GTP that does not hydrolyse
beta-tubulin - may have bound GTP or GDP
function of stathmin and why
binds 2 alpha/beta tubulin dimers together
thus reduces the pool of tubulin able to polymerise
allows GTP-hydrolysis to catch up
causes the microtubule to shrink
function of Microtubule Associated Proteins (MAP’s)
allow crosslinking of microtubules
what is the diameter of an intermediate filament
8-10nm
how is the length of intermediate filaments regulated
proteases are able to degrade specific classes of intermediate filaments
what is saltatory movement
movement of mitochondria/lysosomes along a track in the cytoskeleton
how are motor proteins able to walk along the microtubule?
2 conformational changes
1 conformation stabilised by bound ATP
another conformation from ADP after hydrolyses
in terms of motor proteins what is the function of the globular head regions and the tail region
globular head - engages with the filament and moves along it
tail - point of attachment for the motor protein and its cargo
what is the function of myosin difference between myosin XI and myosin V
myosin XI - cytoplasmic streaming
myosin V - vesicle and organelle transport
what does movement/migration of cells require
anchorage and an active cytoskeleton
how does cilium (cilia) move
Dynein movements cause microtubules to slide of each other
causes the cilium to bend
whats the difference between ABP type I/II/III
type I - binds to membrane via lipid interactions
type II - is an integral membrane protein
type III - binds to an integral membrane protein
whats the difference between ABP type I/II/III
type I - binds to membrane via lipid interactions
type II - is an integral membrane protein
type III - binds to an integral membrane protein
what are the structural units of a chromatin are and what are the structural sub-units of that
nucleosomes
histone octamer
what is spectral karyotyping
technique to paint chromosomes using multi-coloured FISH
helps visualise entire chromosomes
What are the functions of E1, E2 and E3 in terms of ubiquitin
E1 - ubiquitin activating enzyme - activates ubiquitin
E2 - is a ubiquitin conjugating enzyme
E3 - is a ubiquitin ligase - attaches ubiquitin to the target protein
when is APC/C and its substrates active in the cell cycle
when is SCF and its substrates active in the cell cycle
APC/C+substrates - mid M to late G1
SCF+substrates - late G1 to early M
what frequently contacts the cell cortex in terms of microtubules
astral microtubules
function of colchicine
binds to alpha-beta microtubules preventing polymerisation
prevents spindle fibre attachment to kinetichores
triggers SAC response
what can P53 cause
cell cycle arrest
senescence
apoptosis
what do thylakoids form and what do they form and what holds it together
granum disc
granum stack
stroma lamella
what is the function of FNR in PS I
reduces NADP to NADPH
what is the function of Rubisco
converts ribulose-1,5-bisphosphate into 3-phosphoglycerate
up to 50% of the proteins in the stroma
what is a paracrine signal and give some examples
when a signal affects cells in its immediate vicinity
neuronal synapses/immune cells
name paracrine siganl mediators released into the interstitial fluid
histamine
TGF-beta
cytokines
growth factors
what type of signals have the lowest concentration of its mediators in interstitial fluid and why
hormone signals
hormone receptors usually have a high affinity, and the induce potent amplification responses
what are the types of fatty acid derivatives external meesengers
eicosanoid
thromboxanes
leukotrienes
PAF
what type of signalling produces slower responses related to changes in gene activity
lipophilic (hydrophobic)
function of cyclic AMP
activates protein kinases
mainly PKA
binds to ion channels
function of cyclic GMP
activates protein kinases
mainly PKG
function of IP3
releases Ca2+ from intracellular stores
function of DAG
activates protein kinase C
function of acetyl cholinesterase
breaks down acetylcholine at the synapse
what is receptor-ligand internalisation and give examples
as a way to stop signalling, the receptor and its ligands are taken into the cell
LH
somatostatin
what is the function of neostigmine and what does it treat
blacks acetylcholine esterase
increases effectivity of acetylcholine
myasthenia gravis
function of fluoxetine (prozac) and what does it treat
blocks serotonin uptake
used to treat depression
what are the 3 forms of NO synthase and where do they occur
eNOS - blood vessel endothelial cells
nNOS - neuronal cells
iNOS - inducible isoform occurring in immune cells
what does NO target and what does the product of this cause
gaunylate cyclase
forms cGMP
causes relaxations
how does phosphodiesterase stop the NO signal
converts cGMP back into GMP
what is the function of phospholipase C and how is it activated
cleaves PIP2 into IP3 and DAG
activated by G-alpha subunit
give an example of an enzyme-linked receptor
receptor serine/threonine-kinases
how is a tyrosine kinase domain activated
binding of a receptor in the form of a dimer which dimerises 2 inactive tyrosine kinase domains into an active piece
what are the failures of tight junctions
related to auto-immune diseases
chronic inflammation
IBD
what enters the Wnt pathway and what is it used for
beta-catenin
regulates cell division
how does the whole notch thing work
notch binds to delta-ligand receptor on the cell membrane of a different cell
notch is then cleaved at site 2, allowing it to fuck off
notch is then cleaved at site 3 allowing it to enter the nucleus
acts as a transcription factor
what gives regulated breakdown of collagenous breakdown
MMP’s
function and properties of elastin
gives elastic properties in tissues
highly hydrophobic - gives it a random structure and function
what does integrin act as
acts as a nucleation site for actin polymerisation
function of hemidesmosomes
binds epithelial cells to the basement layer
what do parathyroid hormones activate in the kidney and bone tissue
kidney - increases Ca2+ uptake by the distal convoluted tubule
bone - activates osteocytes and octeoclasts
function of nuclear translocation signals
target the receptor-hormone complex to the nucleus
what does is cortisol bound to in blood plasma
transcortin
what is Cushing’s disease caused by
hyper secretion of glucocorticoids by the adrenal glands
what causes Addison’s disease
reduced aldosterone
loss of Na+ in urine
K+ build up
what enzymes are needed to convert beta-hydroxybutyrate into acetone
hydroxybutyrate dehydrogenase into acetoacetate
acetoacetate decarboxylase into acetone
whats the difference between a type 1 and type 2 receptor tyrosine kinase and give an example of a class 2 receptor tyrosine kinase
class 1 - the receptors come together upon ligand binding class 2 - are permanently linked disulphide-linked tetramers insulin receptor
what is the function of GLUT4 and AA, and what cells don’t need them and why
make the cell membrane permeable to glucose and amino acids
beta-pancreatic cells as they always need glucose
what are adipocytes
lipid storage - stops lipid breakdown
what is fibrosis and glycation cuased by
long-term hbyperglycemia
what is Maillard’s reaction and what does it cause
when reducing sugars bind to a protein
causes glycated proteins to cross-link
where is retinoic acid formed from
steroli cells
what do steroli cells convert testosterone into
dihydrotestosterone
how does testosterone in the blood affect GnRH levels
decreases it - negative feedback
what enzyme converts androstenedione and testosterone into 17-beta estradiol
aromatase
what does the luteinisation of granulosa cell cause
converts it to a corpus luteum
