Ib Biology Hl2 - 6.1 (Digestion)

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6.1.1 Explain why digestion of large food molecules is essential. There are two reasons why the digestion of large food molecules is vital. Firstly, the food we eat is made up of many compounds made by other organisms which are not all suitable for human tissues and therefore these have to be broken down and reassembled so that our bodies can use them. Secondly, the food molecules have to be small enough to be absorbed by the villi in the intestine through diffusion, facilitated diffusion or active transport and so large food molecules need to be broken down into smaller ones for absorption to occur. Summary: 


1.Food needs to be broken down and reassembled.
2.Large food molecules need to be broken down into smaller ones.

6.1.2 Explain the need for enzymes in digestion.
Enzymes are needed in the process of digestion as they are the biological catalysts which break down the large food molecules into smaller ones so that these can eventually be absorbed. Digestion can occur naturally at body temperature, however this process takes a very long time as it happens at such a slow rate. For digestion to increase in these circumstances, body temperature would have to increase as well. However this is not possible as it would interfere with other body functions.This is why enzymes are vital as they speed up this process by lowering the activation energy required for the reaction to occur and they do so at body temperature. Summary: 


3.Enzymes break down large food molecules into smaller ones. 4.Speed up the process of digestion by lowering the activation energy for the reaction. 5.Work at body temperature.

6.1.3 State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase.
AmylaseProteaseLipase
EnzymeSalivary AmylasePepsinPancreatic Lipase
SourceSalivary GlandsChief cells in stomach liningPancreas SubstrateStarchProteinsTriglycerides such as fats and oils Products...
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