Inside the digestive system
The purpose of the digestive system is to break food down from being large insoluble molecules to smaller soluble molecules that can be transported in the body.
To break food down two techniques are used.
To break food down two techniques are used.
Mechanical Breakdown
This is when the food is physical broken into smaller pieces by the body. This is most obvious in the mouth where the teeth break the food up.
It is not only the teeth that are involved though. The tongue helps in breaking the food up and so does peristalsis (the muscular movement that moves food through the system). In particular the movement of the stomach will 'squash' the food further mechanically digesting it.
It is not only the teeth that are involved though. The tongue helps in breaking the food up and so does peristalsis (the muscular movement that moves food through the system). In particular the movement of the stomach will 'squash' the food further mechanically digesting it.
Chemical breakdown
This is when the food is broken down into smaller molecules using chemicals - hence the name. Infact, the chemicals that do it are enzymes. You should be familiar with what these are - they are biological catalysts. In other words they occur naturally and speed up chemical reactions without being used up themselves.
There are 3 key groups of enzymes involved in digestion.
Amylase = This breaks carbohydrates into glucose molecules. It is made in the mouth, pancreas and small intestine.
Protease = This breaks protein down into its amino acid building blocks. It is found most importantly in the stomach (it is unusually because it works best in acidic conditions). It is also made by the pancreas and the small intestine.
Lipase = This breaks down fats (think liposuction). This is made in the pancreas and the small intestine.
There are 3 key groups of enzymes involved in digestion.
Amylase = This breaks carbohydrates into glucose molecules. It is made in the mouth, pancreas and small intestine.
Protease = This breaks protein down into its amino acid building blocks. It is found most importantly in the stomach (it is unusually because it works best in acidic conditions). It is also made by the pancreas and the small intestine.
Lipase = This breaks down fats (think liposuction). This is made in the pancreas and the small intestine.
Conditions
Chemical digestion requires the right conditions. As you now know about enzymes you should be aware that they have an optimum temperature and pH at which they work.
All digestive enzymes work best at around 40degrees C, not surprisingly. So they work very well at body temperature (37degrees C). Mostly they work best at a neutral pH. Protease is an exception to this. Protease works best in the acidic conditions found in the stomach. This mean that stomach acid not only kills any living things you may eat but also provides the optimum conditions for protein digestion.
Because other enzymes require neutral conditions for leaving the stomach must be neutralised. This is one of the key functions of a substance called Bile. It is an alkaline solution made by the Liver and stored in the Gall Bladder. It also emulsified fats (breaks them into smaller blobs). This increases the surface area for the enzymes to work on.
Hope this helps - click on the next button for a nice, retro, video!!
All digestive enzymes work best at around 40degrees C, not surprisingly. So they work very well at body temperature (37degrees C). Mostly they work best at a neutral pH. Protease is an exception to this. Protease works best in the acidic conditions found in the stomach. This mean that stomach acid not only kills any living things you may eat but also provides the optimum conditions for protein digestion.
Because other enzymes require neutral conditions for leaving the stomach must be neutralised. This is one of the key functions of a substance called Bile. It is an alkaline solution made by the Liver and stored in the Gall Bladder. It also emulsified fats (breaks them into smaller blobs). This increases the surface area for the enzymes to work on.
Hope this helps - click on the next button for a nice, retro, video!!