Question

1. Think of a meal. Can you identify the primary source of each macronutrient in that meal?

2. Explain in your own words how the products of protein digestion are absorbed from the gut lumen to the capillaries.

3. Why is the formation of micelles an advantage for lipid digestion?

a. The rate of lipid digestion is decreased.

b. The rate of lipid digestion is increased.

c. The release of bile salts is triggered.

4. Into which of the following vessels does lymphatic fluid enter the blood stream?

a. Hepatic portal vein

b. Intestinal capillaries

c. Subclavian vein

Answer 1

1) primary sources of macronutrients are

a) CARBOHYDRATE : it is obtained from the food items like grains ( rice , bread,cereals) , fruits , vegetables like potato and corn, legumes like beans and dairy items like milk, yogurt

b) PROTEIN : it is obtained primarly from Meat, egg, fish , Mlk ,cheese, yogurt, dhal,Beans

c) Fat: it is obtained from Red meat, sweet potatoes, dry fruits, butter ,Avacado, nuts.

2)proteins are absorbed from the intestine as Amino acid ( protein is digested in to the simpler unit called amino acid by the help of protease enxyme)

absorption of amino acids is more in the jejunum,compared to the ileum.

Amino acids are absorbed by a co-transport with sodium ions. Both sodium ion and amino acid combine with a cell surface protein receptor on the intestinal membrane

some amino acids may have its own specific transporter e.g. proline amino acid . The receptor then conveys both molecules to the inside of the cell. The energy for this transport is obtained from the concentration gradient for sodium across the cell membrane. Na-K ATPase transporters actively andwithout delay pump sodium ions outwards to maintain the gradient.

After absorption into an intestinal cell , amino acids can have one of two route:

• some particularly glutamate, are oxidized to liberate energy
• the majority amino acid are passed to the portal circulation

The movement of sodium into the cell is accompanied by chloride and water movement into the intercellular space and eventually the bloodstream.

There can be a small amount of absorption of amino acids as di- and tripeptides. These are mainly digested within the cell to amino acids.

3)Option B - The rate of lipid digestion is increased.

Fat molecules after digestion form michelle with the help of the bile salt secreted from the gall bladder. this help the complicated fat molecules to absorb in to the enterocyte. michelle formation also help in the basorption of fat soluble vitamins like A , D, E, K .

4) Option C - subclavian Vein

the largest lymphatic vessel is the thoracic duct ,

the right thoracic duct drain in to the junction of right subclavian vein and internal jugular vein

left thoracic duct drain in to the junction of left internal jugular and left subclavian vein.