IBDP Biology- Enzymes in Digestion

Enzymes in digestion 

Enzymes: Globular proteins that are biological catalysts which increase the rate of a reaction by lowering the activation energy

• Digestive enzymes are released into the gut from 

glands and are used in catabolic reactions that break down large molecules

• Lowering the activation energy 

high temperatures are not needed because it would cause damage to cells and proteins

• An enzyme allows for a reaction to occur 

more quickly at body temperature

• Large food molecules must be digested before the nutrients can be absorbed

By digesting larger molecules the products are:

• Soluble
• Small

 enough for absorption into blood and assimilation into tissues

Large molecules are unable to diffuse across cell membranes into the blood by:

• Digestion 
• Absorption

One process of making large molecules smaller is chemical digestion

Proteins: Proteins - Amino acids done by Protease

Lipids: Trigylcerides - Glycerol and Fatty acids done by Lipase

Carbs: Mono/di/polysaccharides - Monosaccharides done by Carbohydrase example (Amylase)

Main enzymes in Human Digestion 

Amylases break down carbohydrates

• Example: 
• Salivary Amylase
• Substrate: 
• Starch 
• Product: Maltose
• Source: Salivary glands in mouth
• Optimum pH: 7 - 7.8

Proteases break down polypeptides

• Example: 
• Pepsin
• Substrate: Polypeptides   
• Product: 
• Amino acids
• Source: 

Stomach

• Optimum pH: 2  

Lipases break down fats and lipids

• Example: Pancreatic 
• lipase
• Substrate: Triglycerides          
• Product: 
• Fatty acids and glycerol
• Source: Pancreas delivered into 

small intestine

• Optimum: 7.2 -7.5 

Organs and digestive enzymes  

Mouth: Amylase

• Amylase is secreted by the salivary glands starts to break down 

starch into maltose

Stomach: Pepsin

• Pepsin is a Protase enzyme that works in an optimum pH of 2
• Hydrochloric acid kills bacteria and provides 

acidic conditions

Pancreas: Lipase

• Pancreas secretes Pancreatic juice which has enzymes (carbohydrase, protase and lipase) which digest starch, proteins and lipids
• Alkaline to 

neutralize stomach content

Enzymes 

• Allow digestive processes to occur at body temperature and at the necessary speed to meed organisms survival requirements
• Specific for a given substrate this allows digestion of certain molecules  

The Pancreas 

Pancreatic juice has enzymes:

• Carbohydrase
• Endopeptidase
• Trypsin
• Protease
• Lipase

which digests starch, lipids and proteins

Alkaline to neutralize stomach content

The Pancreas also produces Insulin and Glucagon for Glucose Metabolism

Endopeptidase hydrolyses long polypeptides into smaller polypeptides. Other protein-digesting enzymes hydrolyze smaller polypeptides into amino acids  

And that's the end! Yay!

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References:

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.macmillan.org.uk%2Fcancer-information-and-support%2Fpancreatic-cancer%2Fthe-pancreas&psig=AOvVaw07YVMNVWT2RfWBrbyvOAmb&ust=1625292937337000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCLC5wZnew_ECFQAAAAAdAAAAABAQ

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pinterest.com%2Fpin%2F701294973219612257%2F&psig=AOvVaw1tt9jMPhJKWokjqD5hKgQn&ust=1625293092045000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCKjqkOXew_ECFQAAAAAdAAAAABAN

Drafted by Venetia (Biology)