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Amy Gaskin

07/11/2014

ADH role in
Osmoregulation
 ADH is secreted by the hypothalamus in the brain
when the blood becomes more concentrated with
solutes and the water potential becomes more
negative
...
This
binds to ADH
...

 This 2nd internal enzyme changes the protein
structure of the vesicles containing aquaporins
causing the conformational changes of the
epithelial cell
...

 Therefore, as aquaporins are protein channels that
let water through, more water is able to leave the
cell by osmosis
...

Glucocorticoids are responsible for the metabolism of glucose (including carbohydrates)
and proteins in the liver
...

Dilated pupils allow more light to enter the eyes and therefore vision improves
...

Increased awareness allows reaction times to things that the body wouldn’t normally
respond to is increased
...

The dilation of bronchioles allows more oxygen to get to the lungs which allows more
gaseous exchange to take place
...
(However, less
blood is able to get to the heart)
If more glycogen is converted to more glucose, then more of it can be used for an
increased rate of aerobic respiration in the cells
...

Raised hair not only makes an animal look scarier, but it increases the sensitivity of the
body’s response to touch
...

These are endocrine glands, which are ductless
...

-cells make a peptide hormone called glucagon
-cells make a peptide hormone called insulin
...


And even more facts…
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The endocrine glands only make up 5% of the pancreas’ total function omfg
95% of the pancreas’ function is exocrine gland instead
...

The fluid released in the pancreas is alkaline because the enzymes’ optimum p( is about
8
...
This fluid is sodium hydrogen carbonate!
Sodium hydrogen carbonate is used for more digestion in the small intestine, as it lowers
the pH if the conditions get too close to being neutral or acidic
...
Relatively
speaking, protein molecules are too big to fit
through the plasma membrane
...
This
triggers, with the catalysis of adenyl cyclase, the
conversion of adenine triphosphate (ATP) into
cAMP- the second messenger
...

When the cAMP levels increase, enzymes known
as protein kinases are activated
...

This process can be put into context
...


Anaerobic Respiration in Mammals


Fate of lactate
Anaerobic respiration in diving mammals (e
...
seal)

Lactate -> Liver -> Pyruvate, Glycogen, Glucose
blood

O2

Test: what happens if you constantly clench your fist when your
arm is extended vertically?
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Too much lactate is produced, which causes the muscles to become too acidic
(since lactate is a carboxylic acid)
The pH therefore drops due to an accumulation of H+ ions
...

H+ ions disrupt the tertiary structure of a protein because the charged particles
interfere with the hydrogen bonds and ionic bonds within the tertiary structure
...

Therefore you have less energy which makes it harder to keep clenching your fists
...
However, it cannot do this for long which explains why
anaerobic respiration can provide energy in the short-term
...

This is because there is less oxygen underwater
...
Therefore,
the H+ ions can be mopped up quicker so they can quickly be used for more chemisosmosis
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Amy Gaskin

05/11/2014

Anaerobic Respiration
Fates of pyruvate in anaerobic respiration
Alcoholic Fermentation (Plants and Fungi)


Yeast converts pyruvate into ethanol



Carbon dioxide is removed from pyruvate by decarboxylation to produce ethanol
(acetalaldehyde)



The enzyme alcohol dehydrogenase converts ethanal to ethanol by adding the
hydrogen atom that was lost by oxidising the reduced NAD
...


Lactate dehydrogenase

Amy Gaskin

05/11/2014

Exam Question:
In anaerobic conditions pyruvate does not proceed to the link
reaction
...
[5] (OCR
F214 Jan 2010)
IMPORTANT INFORMATION:


It’s an animal cell, so I’ll talk about lactic fermentation



Pyruvate ends up as lactate



Explain the significance of anaerobic respiration

Mark scheme:


Pyruvate converted to lactate
...




Hydrogen from reduced NAD is catalysed by the enzyme lactate dehydrogenase
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

Therefore the link reaction, Krebs cycle, oxidative phosphorylation cannot take
place
...




SIGNIFICANCE MARK: NAD is able to be recycled; this allows glycolysis to
continue
...




YET ANOTHER SIGNIFICANCE MARK: Some ATP can be still be produced as a result
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This message is carried to the pancreas, which is the target
tissue
...
This
triggers glucagon being released by the alpha cells in the
pancreas
...
Glycogenolysis is when stored
glycogen in the liver is converted into glucose needed for when
the blood glucose concentration drops below normal level
...

If the concentration of glucose in the blood is too high, then
a negative feedback system occurs
...
The
message, likewise to when there’s too little glucose in the
blood, is taken to the pancreas through the process of cell
signalling
...
Insulin tells the fat cells to
absorb the glucose, stop breaking down glycogen into glucose, and rather than
1

http://www
...
com/conditions/diabetes/normal-regulation-blood-glucose

Amy Gaskin
using extra glucose, storing it and converting into
glycogen
...


Outline how insulin secretion is controlled, with
reference to potassium channels and calcium channels in
beta cells
Insulin secretion depends on the blood glucose concentration levels
...
The uptake of glucose
causes a rise in the ATP: ADP ratio
...
This release of calcium ions causes insulin to be released
from their storage granules
...


Amy Gaskin

15/09/14

Control of the heartbeat rate
How does the brain increase the heartbeat rate when we exercise?

Receptors
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-

-

Remember, receptors detect the stimuli and send nervous messages around the
central nervous system to the brain
...

The signal reaches one out of two centres
...

These messages either get sent down the parasympathetic nerve (aka vagus or
inhibitor) or the sympathetic nerve which accelerates the amount impulses and
therefore the number of electrical signals to the SAN
...
This initiates the electric signal needed to start a
heartbeat
...


Baroreceptors
Like the word barometer- the device used to measure air pressure- baroreceptors measure
blood pressure, and the cardiovascular centre in the brain needs to detect whether the blood
pressure needs to increase or decrease
...
When we exercise, the effect is that the blood pressure increases, so that the heart
rate increases
...
Ish
...
When we exercise, the amount of acid produced increases, which lowers the pH
...

More of these are produced when we exercise
...
Basically, gaseous
exchange rate increases so more CO2 can be removed from the body which increases the pH
back to normal
...
This is so more energy can be provided to our cells
...
Therefore, the temperature receptors
in our muscles send a nervous message to the cardiovascular centre in the medulla of the
brain so we can cool down when we exercise
...
Cells
die, and enzymes denature
...
As the frequency of muscle contraction and relaxation
increases when we exercise, the heart needs to beat faster
...

However, they didn’t know the mechanism by which ATP was made
...


Peter Mitchell (1961)
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Mitchell realized a build-up of H+ ions is a source of potential energy
...
Mitchell notied that
energy is released not from a high-energy intermediate, but from the electron transport chains
...

The protons flow through protein channels (because protons are charged and therefore can’t
diffuse through the plasma membrane)
...

The kinetic energy from the electrons drive the force of the flow of H+ ions; this is called the
proton motive force
...

Mitchell suffered heavily from gastro-ulcers when he was teaching at the University of
Edinburgh at the age of 43, so he moved to the countryside
...
He needed some experimental results, so he set up homemade
apparatuses with his wife to measure the pH outside and inside the matrix
...
By comparing the pHs, he was able to see there was a flow of H+ ions along an
electrochemical gradient
...


Since Mitchell’s work…



Since Mitchell’s work, scientists have found evidence of stalked particles present, and found
that their function was that ATP synthase catalysed the phosphorylation reaction of ATP
...


Amy Gaskin

06/11/2014

Experimental work


The chemiosmotic theory is supported by substantial experimental evidence
...

3) In mitochondria with blocked electron transport reactions the "artificial" generation of a
proton motive force can drive ATP synthesis
...




ATP produced in the mitochondrial matrix by oxidative phosphorylation is exported into the
cell cytoplasm by a transporter protein located in the inner membrane
...
The total pool of ATP + ADP
in each cell is small and may turn over hundreds of times a day
...
Many species of bacteria (including Escherichia coli)
have respiratory chains and ATP synthases in their cytoplasmic membrane (which lies just
inside their outer membrane/cell wall)
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Amy Gaskin

06/11/2014

More evidence

 Found
mitoch
and el
inner m
 Found
when
presen
 Oligom
the flo
channe

 The pot
inner m
more ne
the inte
 The pH
matrix w
higher c
the out

Amy Gaskin

06/11/2014

Amy Gaskin

29/09/14

Explain the myelination on the rate of
transmission (6 + 1)
Perfect answer!

1
...

2
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3
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4
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5
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6
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7
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Hairpin Counter-Current Multiplier
Mechanism
Hairpin: Referring to the shape of the loop of Henle
...


Multiplier: The water potential becomes more negative as the flow descends because water leaves
...


Mechanism



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The ascending limb is permeable to the Na+ ions and Cl- ions, and impermeable to water
...
Therefore,
the Na+ and Cl- diffuse from a higher concentration to a lower concentration into the tissue
fluid surrounding the medulla, making it hypertonic
...

Meanwhile, the descending limb is permeable to water but impermeable to ions
...
Urea also
moves out
...

As the water moves out due to osmosis, the water potential of the solution becomes more
negative as more solutes are concentrated (hypertonic)
...

As the solution moves through the distal convoluted tubule towards the collecting duct,
even more water moves out by osmosis into the blood in order to make the solution even
more concentrated (more negative water potential) so as much water as possible is
reabsorbed back into the blood
...


Note: Hyper fro the Greek ea i g o er
Hypo fro the Greek ea i g u der
The length of the loop of Henle largely depends on the temperature of the climate where the animal
lives
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Amy Gaskin

July 10, 2015

How is insulin se reted out of eta ells?
Beta cells are cells within the islets of Langerhans in the pancreas, which are
responsible for secreting insulin into the blood in order to lower glucose
concentration
...
In a normal
situation, the potassium ion channels are open, whereas the calcium ion channels
are shut
...

However, when you eat, and your blood glucose concentration increases, there
are more molecules of glucose outside of the beta cell than those of the inside
...

Once inside the cell, the glucose molecules undergo cellular aerobic respiration,
and ATP is therefore synthesised
...
This increase in ATP concentration causes the potassium ion
channels to shut (due to the caused conformational changes of the protein
channels), thus making K+ ions impermeable to the membrane
...

This change in potential difference causes the voltage gated calcium ion channels
to suddenly open, allowing free Ca2+ ions to start diffusing into the cell down
their concentration gradient
...
This means that the vesicles will move up to the cell surface
membrane, fuse to it, and release the insulin molecules into the blood by
exocytosis
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Amy Gaskin

July 10, 2015

Amy Gaskin

Nerve Impulses
Resting Potentials
A resting potential is where the potential difference of the axon membrane is -70mV
...
K+ ions can pass easily into the cell
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Anions within the axon membrane cannot cross the
membrane
...
This difference in voltage causes a potential difference across the
membrane, and this is the resting potential
...
The cell membrane has potassium and calcium ion
voltage dependent channels
...
Normally, the potassium channels are open, so the
potassium ions can flow out by simple diffusion
...
When the blood glucose concentration is too high, the
glucose moves into the cell via the GLUT2 protein
...

4
...
More and more ATP is
made which causes the ATP: ADP ratio to increase
...
When there is more ATP present, the potassium ions
close, because the potassium channels are ATPsensitive
...
Outside of the cell, the higher concentration of
potassium ions (as they’re positively charged) alters
the potential difference across the cell membrane
...
This is called depolarisation, and it causes calcium
channels to open because they’re voltage dependent
...
The accumulation of calcium ions, by various cell
signalling, causes the vesicles of insulin to fuse with
the cell membrane, which releases the insulin into the
bloodstream by exocytosis

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