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A protein molecules consists of one or more polypeptide chains made up from amino acids

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Chemical elements are joined together to form biological compounds - Blended Learning

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Protein-digesting enzymes are proteases that break the peptide bonds that join the amino acids together.

There are two main types of proteases secreted by the intestines:

Endopeptidases break peptide bonds between specific amino acids in the middle of polypeptide chains.

Exopeptidases break peptide bonds at the ends of polypeptide chains

Proteases are generally secreted in an inactive form to prevent them from digesting the protein within the cells which produce them

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Pepsinogen is the inactive form of the enzyme pepsin.

Pepsin is an endopeptidase which hydrolyses proteins to shorter - chain polypeptides.

pH optimum of about 1.5 - 2.0

Produced by specialised cells within the stomach walls.

It is a substance in gastric juice which is secreted into the stomach. The hydrochloric acid in the juice begins its activation, then the small amount of pepsin formed quickly concerts the remaining pepsinogen into active pepsin by a process called autocatalysis

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Trypsinogen is an inactive form of the enzyme trypsin and is secreted by the exocrine glands in the pancreas.

It is activated by an enzyme enterokinase secreted by epithelial cells of the villi

Once formed, trypsin can autocatalyse the activation of more trypsinogen. Like pepsin, trypsin is an endopeptidase which hydrolyses proteins to shorter - chain polypeptides. It has a pH optimum of about 7.5 - 8.8; this is provided by alkaline salts present in bile and in pancreatic and intestinal juices.

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Digestion of protein involves breaking long polypeptide chains into amino acids and dipeptides that can be absorbed into the blood.

1. proteins --> polypeptides + peptides

2. peptides --> amino acids + dipeptides

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Peptidases are exopeptidases which complete the digestion of proteins by releasing amino acids from the ends of the polypeptides produced by the action of pepsin and trypsin.

Found within the cell membranes of the microvilli found on the surface of intestinal epithelium cells, or in the cytoplasm of the epithelial cells.

They may be classified as:

aminopeptidases if they work at the end of the chain that has an amino acid with a free amino group or carboxypeptidases if they work at the opposite end where the amino acid has a free carboxyl group.

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digestion of proteins clip: 3.06-4.28

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Digestion and Absorption for A-level Biology: Carbohydrates, proteins and lipids (micelles)

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Wordwall - Create better lessons quicker

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Complete the sentence - A cloze activity where you drag and drop words into blank spaces within a text.

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https://www.bbc.co.uk/bitesize/topics/z7c72v4/articles/zr84g7h#zm327yc

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https://quizlet.com/hk/483280766/digestion-of-proteins-flash-cards/