Question

1. The digestion of proteins begins in the ____

   1. Oral cavity

   2. Esophagus

   3. Duodenum

   4. Stomach

   5. colon

2. Partially digested food is usually passed from the stomach to the small intestine about how long after consumption?

   1. 4-8 seconds

   2. 20 minutes

   3. 2-4 hours

   4. 24 hours

   5. 2-3 days

3. Which of the following does not belong with the others, considering the type of substance digested?

   1. Maltase

   2. Sucrase

   3. Lactase

   4. Lipase

   5. amylase

4. Which of the following substances is the most acidic?

   1. Bile

   2. Saliva

   3. Pancreatic juice

   4. Gastric juice

   5. Intestinal juice

5. All of the following are found in pancreatic juice except ____

   1. Pepsin

   2. Trypsin

   3. Carboxypeptidase

   4. Lipase

   5. amylase

Answer 1

1) Digestion of proteins begins in the stomach.

Explaination: proteins are digested by proteolytic enzymes. These enzymes are not present in oral cavity . Proteins start getting digested in stomach due to presence of proteolytic enzyme '' pepsin " in the gastric juice of stomach. Pepsin converts proteins to proteoses + peptones.

After stomach the partially hydrolyzed proteins are acted upon by pancreatic juice and intestinal juice.

Explaination to remaining options

Oral cavity: in oral cavity mastication of food take place.saliva present in mouth contains salivary amylase which hydrolyses starch into disaccharide.

Proteolytic enzyme is not present in oral cavity .so no protein digestion occurs in oral cavity.

Oesophagus : it helps in movement of bolus (masticated food) into stomach through peristaltic movements.

So no digestion of proteins occur here.

Duodenum : it is the first part of small intestine .here digestion of proteins take place .But this is second site for protein digestion.

Colon : it is part of large intestine and here in it only absorption of nutrients take place and no digestion of proteins.

2) partially digested food is usually passed from stomach to small intestine about how long after consumption ?

Answer :2-4 hours

The food which enters the stomach is mixed with gastric juice .Due to strong contractions in stomach food is converted into a thick milky material - chyme.

It takes on about 2- 6 hours to complete this process.

In the options we have 2-4 hours .so it is the correct one.

Explaination to remaining:

24 hours and 2-3 days : food can stay in colon for about 4 hours to 72 hours so these options fall in this category.

4- 8 seconds : food will reach from mouth to pharynx to oesophagus in 4-8 seconds. On an average.

3) which of the following does not belong to others with respect to type of substance being digested

Options are

a) Maltase

b)sucrase

C)lactase

d)lipase

e) amylase

ANSWER : OPTION - D - LIPASE

IT DOES NOT BELONG TO OTHER 4 ENZYMES WITH RESPECT TO TYPE OF SUBSTANCE IT DIGEST.

Lipase acts on fats i.e emulsified fats and covert them into fatty acids and glycerols .Thus lipase digests fats.

Whereas amylase ,Maltase ,sucrase ,lactase acts on carbohydrates .

Amylase covert carbohydrates to maltose +sucrose+lactose

Maltase acts on maltose to give glucose.

While sucrase and lactase acts on sucrose and lactose to give glucose ,fructose and galactose.

4. Which of the following substance is most acidic ?

The given options are

a)Bile

b)saliva

c) pancreatic juice

d) gastric juice

e) intestinal juice.

ANSWER : OPTION - D ( gastric juice)

It has the most acidic pH of about 1.5 -1.8 .

Gastric juice is highly acidic substance secreted in stomach .it contains HCl ,it is responsible for such high acidic pH.

Explaination to remaining

Bile juice has a pH of around 8

Saliva has a pH of 5.4 - 7.4 ( slightly acidic to neutral)

Pancreatic juice has alkaline pH 8.4

Intestinal juice has pH of 7.4 - 8.0 i.e from neutral to alkaline.

5) All of the following are present in pancreatic juice except pepsin

Explaination : pancreatic juice contains the following

Water

Mineral salts

Enzymes : amylase ,lipase

Inactive enzyme precursor like tripsinogen ,chymotripsinogen and procarboxypeptidases.

So pepsin is not present in the pancreatic juice. It is present in the gastric juice only.

Remaining all lipase, amylase,carboxypeptidase ,trypsin are present in pancreatic juice.