The history of the atom

The science of the atom
The word atom comes from the latin word " atomos " meaning indivisible , an atom is the smallest particle of an element that can exist and still contain the properties of that element . There has been found , particles smaller than the atom that make up the atom , these are called sub-atomic particles and consist of protons , neutrons and electrons , even smaller are particles known as quarks , these are too complex to be discussed here and also too , my knowledge of this area of physics is little , there are 6 types of quarks , these shall only be named and not discussed further , they are : up , down , left , right , strange , charm , this is not a joke ppl , I guess the scientist who discovered them was a cool guy . Now we shall discuss how the structure of the atom was formulated , pretty boring if you asked me , but hey , I had to learn it so no harm in telling the story .
The concept of the atom was first conjured in the mind of an old guy called J . J . Thompson in 1902/1907 or so . He thought of the atom as a pudding representing a large ball of postive charge with currants of negative charge arranged randomly but enough to equalize the positve charge , this model was called the , " plum pudding model . " This model I find is stupid but was accepted , later , Ernest Rutherford observed alpha particles passing through a sheet of mica , he thought it solid enough and there were no holes made by this , this made him think . He then instructed his 2 male students , Geiger and Mardsen to investigate this effect , they used a thin sheet of gold foil . Why gold foil you may ask ? Well as I was told by my lessons instructor, it's since gold foil is so malleable that it can be hammered into a very thin sheet without breaking , so thin is this sheet that it's only a few atoms thick , it was not since they were rich and wanted to use gold instead of aluminium foil but because of this reason . They used an apparatus consisting of an evacuated metal sphere , evacuated cause they din't want the air molecules affecting the motion of the alpha particles . They placed a source of alpha particles at a point , then used a thin sheet of gold foil to place in front of the source , they then used a telescope with a zinc sulphide screen which could detect when an alpha particle collided with it as it showed as a flash of light . From this apparatus they observed the deflection of the alpha particles as angles, they found that only 1 in 8000 of these particles was deflected at an angle greater than 90 degrees . This intrigued them , a small few were deflected at 180 degrees , Rutherford once said that it was credible as if you shot a piece of tissue paper and it came back and hit you . An explanation for this is that this proved that the nucleus had a positive charge , the alpha particles are positively charged , being helium nuclei , they would thus be repelled from the nucleus when it came too close to it . There would be an attraction of the alpha particles to the electrons of the atom , but the nucleus , having such a large atomic number would contain a ratio of protons to electron too large to affect the alpha particle . Occasionally the alpha particle came so close to the nucleus that it was repelled from it at a large angle , even more rarely is the head on collision with the nucleus causing a 180 degree deflection .
Another guy called Neils Bohr , connected the quantum theory , Rutherford's model of the atom and some other thing I can't remember now . He said that electrons were situated in shells or orbitals orbiting the nucleus which had a positive charge , the electrons had a negative charge . Later , in 1932 , a fella called J . Chadwick discovered an uncharged particle called the neutron , and suggested it was to have a mass slightly greater than that of the proton , later when it was measured , it was found that this was so , the neutron was slightly heavier than the proton , each is assigned a mass of 1 a.m.u. = 1 u = 1.67 * 10^-27 kg , pretty small if you asked me!
Much of what we think an atom is today was formulated by Neils Bohr , electrons are situated in regions called orbitals , clouds around the nucleus .
Points to note : the diameter of a nucleus - 10^-14m
The diameter of a molecule- 10^-10m
One of my physics teachers once said we'll never be able to see an atom , however there is evidence that when a thin sheet of copper was observed at the highest magnification of an electron microscope, small spheres were seen , equidistant from one another , are these atoms ? I guess they are .

Digestion of food

The digestion of food - The digestion of food

Food contains many different substances , carbohydrates , fats , proteins as we all know are the main ones but there are many others . Here , I shall use a meal of steak and fries , the steak is the source of protein and some fat , and the fries are the carbohydrate .
Ingestion of food- Ingestion of food
You ingest food using the teeth , lips and tongue , the food is placed into the mouth and through the first process of mechanical digestion , the teeth break the food into smaller pieces so that there is a larger surface area for the action of enzymes on the food . The food is broken up into these smaller pieces , then saliva is secreted from the 3 pairs of salivary glands situated in the mouth , under the tongue . Saliva contains three substances : water , mucus and the enzyme amylase . Amylase serves to digest starch in the food in the mouth , however since the food stays in the mouth for a very short while , the enzyme does not usually have enough time to do this . Mucus is nothing new , it is found throughout the alimentary canal . There is no chemical digestion , that is the action of enzymes on the food being used yet , since only amylase is found here and very rarely can it begin digestion . After the food has been broken up enough mechanically , the tongue presses the bolus of food against the soft palate at the roof of the mouth , a reflex action then takes place where a flap of cartilage , called the epiglottis , covers the opening to the trachea , so that food does not go down the wrong passage . The bolus of food then travels down the oesophagus where by peristalisis , a process involving the contraction of the muscles of the alimentary canal to the bottom of the oesophagus before the stomach . There is a sphincter muscle located here , these muscles can close of the tube completely in certain places . The muscle gradually lets the food at intervals into the stomach .
Digestion of food - Digestion of food
In the stomach are gastric pits which are located in the stomach lining , these secrete hydrochloric acid which is necessary to produce an acid pH for the action of the stomach enzymes . The acid is also used to kill any bacteria in the food . There is only one enzyme present in the stomach , it is called pepsin and requires an acid environment . Pepsin is responsible for the breakdown of proteins into polypeptides , in the stomach of young mammals there is also an enzyme called rennin which is needed to clot the milk from the mothers so that it can be then broken down by pepsin . Mechanical digestion of the food also takes place here , where the stomach walls churn the food so that it can mix together with the gastric juice in the stomach . The food stays in the stomach for a varying period of time , this meal would stay for longer than an hour due to the high protein content . The stomach wall also contains mucous membranes to prevent the gastric juice eating away at the wall . After the time period , a sphincter muscle at the end of the stomach lets the chyme at intervals into the duodenum , the first part of the small intestine .
In the duodenum , two digestive juices are secreted , one is pancreatic juice which travels via the pancreatic duct , from a cream coloured gland situated just below the stomach . It contains three enzymes , lipase to digest fats (lipids) , amylase to digest starch and proteases to digest proteins . The other juice is bile , it is contains no enzymes and is a green coloured liquid formed as a bi product of the deamination of old red blood cells , the extra haemoglobin is used in the liver to make bile which is stored in the gall bladder , the bile travels to the duodenum via the bile duct . The bile contains sodium hydrogen carbonate which is used to neutralize the gastric juice so that the enzymes of the pancreatic juice can work properly . The proteins in the beef which were not digested into polypeptides in the stomach are broken down by the proteases to more polypeptides . The starch in the potato of the fries is now broken down to maltose by the amylase . Enzymes are biological catalysts , the substance at the beginning of the reaction is called the substrate and is broken down to a product at the end of the reaction , e.g. :
starch ----------> maltose
amylase
There are three parts of the small intestine , the duodenum , jejunum and ileum . The function of the bile is to digest fats , it breaks large drops of fat into smaller ones in a process known as emulsification . The fat in the steak is broken up like this , the food then travels through the jejunum where it is further broken down and then to the ileum where more enzymes are secreted. The enzymes secreted after the duodenum are , lipases , to break down the fats to fatty acids and glycerol , maltase to break down the maltose to glucose and fructose and trypsin to break down the polypeptides to amino acids . The definition of digestion is - the breakdown of large , complex , insoluble molecules to smaller , simple , soluble ones . The molecules are now small and simple and can now enter the blood , they can now pass through the walls of the alimentary canal. This is done via small (1mm) projections of the alimentary lining called villi which absorb fats , amino acids , glucose , vitamins , minerals etc..
Absorption of food - Absorption of food
There are lacteals in the villi who serve to absorb fats , and blood capillaries to pass the glucose etc.. to the liver to be processed , via the hepatic portal vein . If there is too much protein already in the blood , then the protein from the steak would be excess , it would be wasteful to excrete it as it is , so the excess protein is broken down , in a process known as deamination . The amino acid is broken down , the useful portion , containing energy , stored , as carbohydrate or fat and the part containing urea sent to the kidneys to be excreted . After the liver has processed the food, reabsorbing any excess glucose etc. the substances now enter the blood . The amino acids now enter the blood and are used for growth and repair , making enzymes , energy , making cell membranes , making antibodies and the glucose used for energy .
Only indigestible food is egested , since there was no plant material in the food , it is not egested and all substances are assimilated .