8.1b The digestive system (Protein digestion)

• What is the mechanical digestion?

  Breaks down food physically through chewing and stomach churning, increasing surface area for chemical digestion.
• What is chemical digestion?

  Involves the breakdown of food molecules into smaller absorbable nutrients through the action of enzymes and acids in the digestive system.
• What are the conditions for protein digestion?

  Protein digestion requires an acidic environment, primarily in the stomach, where the enzyme pepsin breaks down protein into smaller fragments. Enzymes in the small intestine further break down these fragments into absorbable amino acids.
• What is the protein digestion experiment?

  1. Make observations of the steak pieces then place one in each test tubed labelled A-D.
  2. In test tube A add 2cm(cubed) water
  3. In test tube B add 2cm(cubed) pepsin
  4. In test tube C add 2cm(cubed) hydrochloric acid
  5. In the test tube D add 1cm (cubed) pepsin & 1cm (cubed) hydrochloric acid
  6. Leave for 10 minutes the reaction to occur.
  7. Remove the steak with forceps and observe any differences in texture, colour or size.
• What is the independent variable related to the protein digestion experiment?

  The substance added to the test tubes (water, pepsin, hydrochloric acid, or a combination of pepsin and hydrochloric acid).
• What is the dependent variable related to the protein digestion experiment?

  The differences in texture, colour, or size of the steak after it has been subjected to the different treatments.
• What are the control variables in the protein digestion experiment?

  1. The size and type of steak in each test tube
  2. The volume of substances added : same amount of water, pepsin, hydrochloric acid, or combination of pepsin and hydrochloric acid.
  3. Forceps usage: use the same type of forceps to handle steak pieces in each test tube
• Result of test tube A after the experiment?

  The steak piece may show minimal to no changes in texture, colour, or size. Water alone does not contain any enzymes or acids capable of digesting proteins.
• Results of test tube B after the experiment?

  
  

  The steak piece may appear softened or partially broken down.There might be changes in texture, with some parts of the steak appearing mushy or disintegrating.There may be slight changes in colour due to enzymatic action.
• Results of Test tube C after the experiment?

  
  

  The steak piece may not show significant changes in texture or size, but there could be some changes in colour. Hydrochloric acid alone primarily provides an acidic environment but doesn't digest proteins without an enzyme like pepsin.
• Results of test tube D after the experiment?

  
  

  The steak piece may exhibit more pronounced changes compared to other test tubes. It may appear more broken down, with noticeable softening and disintegration. Changes in colour and texture may be more pronounced compared to other treatments due to the combined action of pepsin and hydrochloric acid.
• Explain why acid helps protein digestion 

  Acids, particularly hydrochloric acid in the stomach, lowers the pH, creating an acidic environment. This acidity activates pepsin, an enzyme responsible for breaking down proteins into smaller fragments, facilitating protein digestion.