Digestion Extended Response

Celiac disease is an immune reaction to eating gluten, a protein found in many cereals. The diagram shows the arrangement of normal villi and villi affected by celiac disease in the small intestine.

(a) Outline the functions of the villi in the small intestine. [2]

No vili, can’t get enough nutrients since not absorbed properly.

   Celiac disease is an immune reaction to eating gluten, a protein found in many cereals. The diagram shows the arrangement of normal villi and villi affected by celiac disease in the small intestine.

(b) Explain the consequences of celiac disease for absorption of digested nutrients. [2]

Eat, chew, saliva breaks it down, then into the stomach, then stomach acids and pepsin breaks down gluten into amino acids.

 Celiac disease is an immune reaction to eating gluten, a protein found in many cereals. The diagram shows the arrangement of normal villi and villi affected by celiac disease in the small intestine.

(c) Wheat, barley and rye all contain gluten. Outline how a protein such as gluten is digested. [2]

   (a) The diagram shows alpha amylase.

Explain the secondary structure of this protein molecule. [3]

(Describe beta pleated sheet and how its mixed with alpha. Held together by hydrogen bonds)

(b.i) State two sites of production of amylase. [1]

1 = Salivary glands

2 = Pancreas

(b.ii) State the function of amylase. [1]

Breaks starch into maltose.

(c) Explain how enzymes catalyse chemical reactions. [3]

(Bind to substrate, change shape, weaken bonds, lower activation energy)

Humans ingest food which provides energy and nutrients to carry out life processes.

(a) Outline how starch in the diet is modified for absorption in humans. [3]

(how is starch digested) Broken down x2, then glucose is absorbed in small intestine.

 Humans ingest food which provides energy and nutrients to carry out life processes.

(b) Describe how the small intestine is adapted for efficient absorption of nutrients. [5]

1. Vili and microvili

2. Each vili has a capillary bed (closer to blood, easier to absorb it)

3. Lacteal absorb lipids 

4. The walls of vili are very thin (1 cell thick) 

5. Cells of SI has a lot of mitochondria - energy to pump the nutrients into the blood vessel.

 Humans rely on carbohydrates for much of their energy. Outline the process of digestion and absorption of starch in the human digestive system. [4]

(how is starch digested) Broken down x2, then glucose is absorbed in small intestine.

 Explain the adaptations of the small intestine to its function. [7]

   Pastry cream or confectioners’ custard is made with a combination of milk (rich in casein and lactose), egg yolks, sugar, starch and a flavouring such as vanilla.

(a) Describe the structure of starch. [5]

Glucose stuck together in long chain.

maltose into starch

(explain how they are put together)

Monomoers (glucose) bind through condensation reaction, water is byproduct

 Pastry cream or confectioners’ custard is made with a combination of milk (rich in casein and lactose), egg yolks, sugar, starch and a flavouring such as vanilla.

b) Explain how amino acids in casein could reach the liver, starting from the moment when the person takes a bite of pastry cream pie. [7]

(Casein is protein = explain how proteins are digested.)

Chew into small pieces, then enter the esophagus, then the stomach mixes with acids and activated pepsin that’s gonna digest casein into individual amino acids. Then it would be absorbed in blood, and take it to anywhere in the body, including the liver.

Proteins are an important group of chemicals found in all living organisms.

Outline how proteins are digested and the products of protein digestion absorbed in humans. [4]

(Describe how proteins are digested)

   Outline the role of amylase in digestion in humans. [4]

In mouth and pancreas breaks down amylose into maltose, then broken down into glucose with maltase then absorbed. 

(in pancreas also because the salivary ones denature in stomach)

 Explain the action of enzymes in digestion and the different roles of at least two named enzymes that are produced in the pancreas. [8]

Lipase and amylase and talk about those

(Can’t talk about pepsin, but can talk about peptidase that digests proteins)

(What it binds to, how it works, what it breaks into, how it speeds up reactions, how it binds to specific substrates, all the details, (how the enzymes work))

 Describe the processes involved in absorbing different nutrients across the cell membrane of villus epithelium cells lining the small intestine. [4]

(Describe digestion)

Enzymes like lipase break down small particles that can be absorbed through the membrane.

Talk about active transport and how not only rely on passive diffusion. Want to build conc. Of nutrients in blood, not digestive track so shouldn’t be equal.