I wake up, my debt is all paid off, my bank account is full, my relationships with my family are healthy, and I’m able to travel anywhere in the world.
Right, considering the current state of corporate politics on this site, and that it seems that only those affected seem to be actively speaking on the matter, it is up to I, the only fucking cishet on tumblr, to drag this out to a wider audience.
REBLOG IF YOUR ACCOUNT IS A TRANSFEM SAFE SPACE.
We need to show these higher ups how much we truly value them.
Boo - I said a while ago I was gonna be more active
I really meant it and I wanna and I feel like it looks like I lied
Truth be told, life's been a mess- And I've finally gone ahead to try and address things.
This involves reaching out for an ADHD assessment. Unfortunately this isn't likely to happen until next year - and with the world going crazy and money being a thing needed for living, my time for this space, work, general life and adulting, is a lot to keep up and I unintentionally dropped this ball.
Hope this explains a little and people are okay with this/understand!
Boo - I said a while ago I was gonna be more active
I really meant it and I wanna and I feel like it looks like I lied
Truth be told, life's been a mess- And I've finally gone ahead to try and address things.
This involves reaching out for an ADHD assessment. Unfortunately this isn't likely to happen until next year - and with the world going crazy and money being a thing needed for living, my time for this space, work, general life and adulting, is a lot to keep up and I unintentionally dropped this ball.
Hope this explains a little and people are okay with this/understand!
Had a lot of days of being needed by friends and family - I'm so busy with study, housework, work & then I got ill! But I promise more A level posts are on their way!
The next topics I plan to do are:
Spectrometry (Chemistry)
Lipids (Biology)
Proteins (Biology)
I will add to the list but am trying to not overwhelm myself!
Mass spectrometry is a highly useful form of analysis, with the most commonly used type of mass spectrometry being time of flight (ToF) spectrometry. ToF spectrometry has multiple uses such as:
Finding out the relative atomic mass of an element by finding the mass and abundance of isotopes within the element
Finding out the relative molecular mass of a molecule
THE STAGES
There are multiple steps involved in the process and we need to know all of them (I know - I wish we didn't have to either but the AQA spec says so...)
Ionisation
Acceleration
Ion drift
Detection
1) IONISATION
There are actually two types of ionisation that we need to know that
can happen in a ToF spectrometer. Electron impact ionisation (a.k.a. electron ionisation) and electrospray ionisation.
Electron impact ionisation (a.k.a. electron ionisation)
This process is done by first being vaporised and then bombarded with electrons that are fired from an 'electron gun' (i.e. a hot wire filament with a current that runs through it and emits electrons). This typically results in an electron being knocked off of each sample particle to form a 1+ ion. These 1+ ions are then attracted to a plate with a negative charge (this is where they're accelerated!) - However, this is a rather harsh form of ionisation and frequently results in fragmentation of the molecular ion (this results in fragments being picked up on the mass spectrum) - This is good to know, but also not actually in the specification! :)
Electrospray ionisation (this is a soft ionisation technique)
To start, the sample is mixed with a volatile solvent. This is then pushed through a hypodermic needle at high velocity. The needle has a high voltage held through it to shock the sample particles as they pass through. This results in a cloud of positively charged 1+ ions (they lose an electron because of the high voltage shock!) The ions are then accelerated by a negative plate.
2) ACCELERATION
The positive ions are accelerated using an electric field. This results in them all having the same kinetic energy. (Super important for the next stage!)
3) ION DRIFT
The +1 ions travel through the middle of a negatively charged plate (through a hole) into a tube. This is the stage where the ions drift through a field with no charge. The thing that differentiates these ions is their mass/charge ratio. The higher the mass/charge ratio, the heavier the ion, the slower it goes (and vice versa). This means they hit the detector at different times (thus showing the abundance - but I'll explain that in a moment!)
4) DETECTION
The 1+ ions hit a negatively charged plate. This contact causes the ions to lose their charge as they collect an electron from the plate. This results in a movement of electrons, which produces an electric current that we can measure. The more electrons that hit the plate at once, the larger the current. This then translates on the mass spectrum as a larger spike.
If you've made it this far, well done!! You deserve a cookie (or something... I don't have one for you, but you deserve one!!)
Now that you've looked at all of that, it's time to look at the results! But since this post is already rather long, I will be making another post to cover that! (Sorry!)
Useful AQA resources:
https://filestore.aqa.org.uk/resources/chemistry/AQA-7404-7405-TN-MASS-SPECTROMETRY.PDF - This has pictures etc and is official AQA material :D
As we have covered already, atoms are so teeny tiny, we have no real way to actually weigh them, so we use relative mass!
But in order to use relative mass, you have to be able to relate one thing to another (otherwise, how can it be relative, ya know?)
So relative mass is based on a scale where carbon 12 has a mass of exactly 12 (pictured below)
The reason for this is because there is no other isotope that has an exact whole mass number - so scientists believe it must have an exact mass of 12 :)
Relative Atomic Mass
This is the average mass of an atom of an element on a scale where C-12 = 12 (This number is not commonly a whole number because it is the mean average of all of the isotopes and their abundance!)
Relative Isotopic mass
This is the relative mass of an isotope on a scale where C-12 = 12
Relative Molecular mass
This is the relative mass of a molecule on a scale where C-12 = 12. This is worked out by adding up the atomic mass of each and every atom within the molecule (e.g. Water has 2 hydrogen atoms (atomic mass: 1) and 1 oxygen atom (atomic mass: 16) so the relative molecular mass would be 1 + 1 + 16 = 18)
Relative formula mass
This is very similar to relative molecular mass - it is even worked out the same! However, this is used when dealing with ionic (or giant covalent) compounds! This is still based on a scale where C-12 = 12
These are all important to understand! This will make a lot of chemistry make a lot more sense (and everyone wants an easier time right?) - I will put up a post shortly regarding Mass Spectrometry (Time of Flight spectrometry to be specific)
Long ago, in a land before time - okay maybe not that long a go but still! The model of atomic structure used to look a lot more different than the one commonly used today (some people had some pretty interesting ideas on what atoms were and what they looked like!)
What we know about the atom is that it is the most basic unit of any chemical element - it is also super tiny (you can't really go smaller than an atom without splitting it, and I really don't recommend doing that!)
(QUICK NOTE: This isn't 100% conclusive, but it is as much as we need to know. There have been a tone of different proposals and ideas over the years, and the model has evolved significantly over time!)
First up to propose an accepted model was John Dalton (1803)
This was called the solid sphere model and basically stated that atoms are invisible (since the Greek word 'atomos' means invisible). The idea was that there were different types of atom which were responsible for different compounds - but all of them were invisible!
Next up was J.J. Thomson (1904)
Over 100 years after the solid sphere theory was adopted, Thomson discovered something awesome: electrons! The model he suggested was called the plum pudding model - a sphere of positive charge studded with negatively charged electrons! (the positive sphere represents the pudding and the electrons represent the raisins in the plum pudding - hence the name!)
Following closely behind was Ernest Rutherford (1911)
The plum pudding model was disproved when Ernest Rutherford and his team conducted the gold foil experiment. This consisted of firing positively charged alpha particles at a thin gold foil sheet. They expected to see alpha particles to go straight through the sheet, and they did for the most part - some however, were deflected at sharp, big angles! Rutherford quickly realised this would only be possible if the atom mostly consisted of empty space (where the electrons freely existed) with a concentrated positive charged middle (aka the nucleus!) - He called this model the nuclear model.
This was touched up on by Niels Bohr (1913)
For the most part, what Rutherford had suggested did make sense - however there were a few problems. The main issue was that there had to be something holding the electrons away from the nucleus. If there wasn't, the entire atom would collapse in on itself (which would be bad and also wasn't the case). So Niels Bohr fixed it by suggesting that the electrons were in orbits of fixed energies and sizes where they orbited the nucleus. He also stated that in this model, electrons could not be found between these orbits! The model is called the planetary model
There is one model that has since been developed (it's called the quantum model by Erwin Schrödinger in 1926 for anyone who wants to look further into it) and it is seen as more accurate - However, whilst we now know that electrons don't orbit the nucleus the same way as planets orbit the sun, the model is accurate enough to still be widely used in teaching :)
Love them or hate them, they're important to know... As I covered in a previous post, a neutral atom (that is, an atom with no charge) has an equal amount of protons and electrons. However, there exists a thing where the number of electrons differs to the number of protons - The ion!
Ions come in two forms:
Positive ions
These are ions that have 1 or more electrons fewer than protons (so 1 or more negative charge has been removed, leaving the positive protons, thus making the ion positively charged!)
Negative ions
These are ions that have 1 or more electrons more than protons (so 1 or more negative charge has been added, resulting in the ion being negatively charged!)
~ It is essential to note that the number of protons does not change!! Only the number of electrons change! ~
ISOTOPES
These are atoms with a differing number of neutrons to electrons. They can be naturally occurring and have different physical properties to one another. A notable element is hydrogen, with 3 naturally occurring isotopes!
Protium is by far the most abundant and commonly found hydrogen isotope.
Deuterium is also a stable isotope. This isotope is sometimes referred to as "heavy hydrogen" because it has an atomic mass that is double that of protium.
Tritium is incredibly unstable (it's radioactive!)
VERYTHING that is chemistry comes down to atoms. these are the fundamental particles that make up absolutely everything (energy not included) - Which is really cool if you allow yourself to think about it!
This means it is super important that we can fully understand and appreciate what an atom is!
An atoms structure in its most basic sense, is a nucleus (made up of protons and neutrons) orbited by electrons in shells.
When you look at an element on a periodic table, you will see a nuclear symbol, an atomic mass number, and an atomic number.
Atomic mass number: The number of protons and neutrons combined.
Atomic number: Can also be called the proton number and is the number of protons in the atom
A neutral atom will have an equal number of electrons to protons (the charges must cancel each other out otherwise the atom can't be neutral!)
Another thing about protons, neutrons and electrons: Because they are tiny, we have no real way of actually weighing them. As a result, we use "relative" mass (i.e. the relative weight of the subatomic particles).
They also have individual relative charges
Protons: Are said to have a +1 charge (so they are positively charged!)
Neutrons: Have 0 charge (they are neutral!)
Electrons: Have a charge of -1 (so they are negatively charged!)
There is more to cover, like ions and isotopes.
I also plan to do a post on the history of the model of atomic structure since it is in the spec (and also pretty interesting too!)
1) Place the sample solution being tested into the clean test tube.
2) Add potassium iodine solution to the sample in the test tube
The solution will be a brown-yellow colour (this is the colour of the potassium iodine solution)
3) Mix the solutions together by giving it a gentle shake :)
Make sure you specify that it is potassium iodine solution and not just iodine solution! (The potassium iodine mix results in iodine ions needed for the test to actually work - plus the exam people are very specific, so we need to be too!)
If starch is present in the sample, the colour will change from being yellow-brown to blue-black.
If no starch is present in the sample, no colour change will occur.
I have said it before, I will say it again: Make sure to specify that the iodine solution is potassium iodine solution - The AQA exam gods are very particular and it would be a shame to potentially lose marks for not specifying!
The exams are heavily focused on making sure people understand the practical's, so I wanted to cover them properly in their own post :)
BENEDICT'S TEST - For detecting reducing sugars
For this test you will need:
A clean test tube
A sample (for testing) - needs to be a solution
Benedict's reagent (copper (II) sulphate)
A heated water bath
Method
1) Take 2ml of the solution being used for testing and add it to the clean test tube
2) Add 2ml of Benedict's reagent (copper (II) sulphate) to the same test tube (you must use equal amounts of the reagent and testing solution)
- by this stage, the mixture will be blue in colour as that is the colour of the reagent.
3) Take the test tube and partially submerge it in the heated water bath (the water should be at about 100°C) for about 3-5 minutes - the goal is to heat it through.
If a reducing sugar is present, then the solution will gradually go from the original blue colour to a brick red precipitation.
The reducing sugar would donate 1 electron to the Cu(2+) ions in the copper (II) sulphate. The result of this would be Cu+ ions, which would form the orange-red precipitate copper (I) oxide. - (i.e. the reducing sugar would reduce the Copper (II) sulphate to form copper (I) oxide).
This colour change goes in this order: blue - green - yellow - orange - red - This colour change happens as the copper (I) oxide is created! (If no colour change happens, there is no sugar).
If there is only a small amount of reducing sugar present, the amount of precipitate created would be less and so the reaction may appear more green or yellow. This just means that not all of the Benedict's reagent has been used up in the reaction.
Any colour change indicates the presence of a reducing sugar. It's the concentration that determines how far along the colour scale the solution will turn. (Even if the solution looks green, there has to be copper (I) oxide present since it is being turned green by the red precipitate being formed!) - This means that the test can also be used to get an idea of how much reducing sugar is in the solution.
Non-Reducing Sugars
A negative test doesn't definitively mean that there's no reducing sugars present - It just means you might have to break down the sample into monosaccharides and repeat the test. This can be done like so:
1) Get a new sample of the test solution in a clean test tube and add dilute hydrochloric acid to the mixture.
2) Carefully heat the sample in the heated water bath (heated to 100°C)
3) Neutralise the sample with sodium hydrogen carbonate (baking powder!)
4) Carry out the test like you did the first time!
If the test forms a coloured precipitate, the test has come back as positive. If the test stays blue, the test is negative
REAGENT TEST STRIPS
There's another test that you can do called the Reagent test strip. This is literally a commercial test strip that can be used to identify the presence of reducing sugars.
The test is carried out by dipping the strip into the test sample and comparing the colour it turns to a chart (the chart helps to estimate the reducing sugar concentration.
For a real world application of the reagent test strips - These are often used to test for the presence of sugar in urine (useful if diabetes is suspected!)
Polysaccharides are carbohydrate polymers made up of many monosaccharides bonded together via condensation reaction (are you sick of that line yet... I know I am!)
Technically speaking, a true polysaccharide is made up of more than ten monosaccharides - so if you have a chain that is smaller than this (so about 3 - 10 monosaccharides bonded together), you've got what's called an oligosaccharide!
Now that we know what a polysaccharide is, I just want to quickly go over what a polysaccharide is NOT.
Sweet in taste
Soluble
Because of these factors, polysaccharides don't actually class as sugars! (Even though they are made of sugar).
The main ones we will be looking at in this post are starch, glycogen and cellulose.
STARCH
Starch, which is found in plants and is made up of alpha glucose molecules. It is used as an energy store and can usually be found in
leaves (in the leaf chloroplasts) and in tubers and grains (in amyloplasts).
Starch can be broken down further into two types of polysaccharide:
Amylose
This structure is long and made entirely of 1,4 glycosidic bonds. This has a spiral structure as the long chains curl around one another to keep the hydroxyl (-OH) groups of the glucose monomers on the inside of the spiral.
Amylopectin
This structure is long and branched. It is made up of both 1,4 glycosidic bonds and 1,6 glycosidic bonds (the 1,6 glycosidic bonds are responsible for the branches)
The benefit of storing glucose as starch in plants is that it doesn't impact the cells water potential (can't diffuse out of the cell). Also, most of it can be stored away in small places (which makes it a good energy store!) - Starch is relatively insoluble.
GLYCOGEN
Glycogen is the main energy store in mammals. Just like starch, it is made up of alpha glucose monomers. The structure is very similar to amylopectin in starch, but is more branched.
As a final note regarding alpha glucose: There are multiple factors that make it a good energy store.
These polysaccharides have no impact on the osmotic balance of the cell (the cells water potential) because of their insoluble nature. This prevents them from drawing water into the cell via osmosis.
If a cell takes on too much water, a process called cytolysis occurs (the cell bursts open and dies as a result) so storing it in an insoluble form is very handy!
They don't diffuse out of the cell (unlike individual alpha glucose molecules) thanks to their large size.
Although they are large molecules, they are also very compact (i.e. a lot of energy can be stored in a small amount of space!)
They can easily be hydrolysed for quick energy release
When energy demand increases and the cells need more energy to continue normal function, the enzymes can go along the branches and hydrolyse sections to be broken down into alpha glucose to meet energy demands) - these glucose molecules would then be used for respiration by the cells.
CELLULOSE
Cellulose is made up of condensed beta glucose molecules and plays a role in plant structure. The cell walls are made up of this polysaccharide - without it, the plant would lack rigidity and be more at risk of having its cells burst open if too much water enters (via osmosis). Instead, the cell swells, pushes towards the cell wall and the wall holds the cells shape. The cell is referred to as being turgid when it is like this!
This turgidity is actually really important because it means the cells each have enough strength to support the whole cell (so plants like to be in this state, which is why they usually enjoy moist soil!) - If there is not enough turgidity, cellulose or water, the plant loses rigidity and begins to wilt (Sorry mr. houseplant :/ ).
Cellulose has a very long, straight structure, which makes it very good for layering. These chains lay parallel to lots and lots of other cellulose strands and form hydrogen bonds between the hydroxyl (-OH) groups that sit in close proximity. This leads to a cross-linking between the chains.
(Remember, beta glucose will alternate itself by inverting itself 180°). This is important because it is what stops the chain from coiling!
As a result of the layering and hydrogen bonding (literally thousands of hydrogen bonds!), strong strands are created. These strands are known as microfibrils (lots of cellulose chains bundled together essentially) - As more microfibrils are created, these too begin to bundle together and form even larger fibres called macrofibrils. (I will just be calling these fibres because it's easier!)
These fibres basically add strength to the plant cells by wrapping around them. It does this at multiple different angles and builds up multiple layers, allowing for that turgidity the plant needs so much to actually take place.
Since cellulose is such a big component in plant cell walls, it is one of the most abundant organic materials we have. (This doesn't mean it is a good food source though - It is very hard to break down by hydrolysis and as a result, is super hard to digest!)
The enzyme cellulase is needed for cellulose to be digested - something most animals do not produce. (This enzyme acts by breaking down the 1,4 beta glycosidic bonds between the beta glucose molecules.)
There are symbiotic bacteria that produce cellulase and can be found in the guts of some herbivores. Ruminants (like cows, sheep, deer etc) are much more efficient at this than herbivores that undergo monogastric digestion - This allows them to obtain energy from cellulose that most other creatures cannot.
Although we cannot digest cellulose, we still need fibre for good gut health!
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