The Digestive System 1.2

Question 0

What are the monomers called in carbohydrates?

Answer 0

Monosaccharides

They contain carbon, oxygen and hydrogen.

Question 1

What is digestion?

Answer 1

The breaking down of larger molecules into smaller molecules.

Question 2

What are the monomers called in proteins?

Answer 2

Amino acids

They contain hydrogen, carbon, oxygen and nitrogen.

Question 3

Explain how the oesophagus takes food into the stomach.

Answer 3

It uses waves of muscle contractions called peristalsis. Mucus is also secreted from tissues in the walls, to Lubricate the foods passage.

Question 4

Describe and explain the stomachs role in digestion.

Answer 4

The stomach has lots of folds so that it can expand. The entrance and exit to the stomach are controlled by the sphincter muscles.gastric juice is produced from the cell walls to break down the food. Pepsin hydrolyses proteins into shorter polypeptide chains. Peristalsis of the stomach turns the food into acidic fluid called chyme.

Question 5

What does gastric juice consist of?

Answer 5

Hydrochloric acid, pepsin and mucus.

Question 6

Describe and explain the role of the small intestine in digestion.

Answer 6

It has two main parts the duodenum and the ileum. Chyme is moved along the small intestine by peristalsis. In the duodenum bile and pancreatic juice neutralise the acidity of the chyme and beak down the smaller molecules. In the ileum, the smaller, soluble molecules are absorbed through villi.

Question 7

Describe and explain the role of the large intestine in digestion.

Answer 7

The large intestine absorbs water, salts and minerals. It has folded walls which provides a large surface area for absorption.

Question 8

Describe and explain the role of the rectum in digestion.

Answer 8

Faeces are stored in the rectum and then pass through the sphincter muscles at the anus, during defecation.

Question 9

Which bond is formed when two amino acids join together?

Answer 9

Dipeptide

Question 10

Name the similarities and differences between amino acids.

Answer 10

They have different variable groups.

They all have the same COOH and NH2 group.

Question 11

What reaction forms a polypeptide bond?

Answer 11

Condensation reaction.

Question 12

What does amylase hydrolyse?

Answer 12

Starch into maltose

Question 13

Where is amylase secreted?

Answer 13

The salivary glands and the pancreas.

Question 14

What does pepsin hydrolyse?

Answer 14

Protein to peptides.

Question 15

What does the pancreas secrete?

Answer 15

Amylase, trypsin, chymotrypsin, carboxypeptidase, lipase

Question 16

What does maltase hydrolyse?

Answer 16

Maltose to glucose.

Question 17

What does sucrase hydrolyse?

Answer 17

Sucrose into glucose and fructose.

Question 18

What does lactase hydrolyse?

Answer 18

Lactose into glucose and galactose.

Question 19

What does peptidase hydrolyse?

Answer 19

Peptides to amino acids.

Question 20

What bond is formed when two monosaccharides join together?

Answer 20

Glycosidic bond

Question 21

Outline the buiret test for proteins.

Answer 21

1. Solution must be alkaline so add sodium hydroxide.
2. Add copper(II) sulphate
   Turns purple in the presence of proteins.

Question 22

How does lactose intolerance cause diarrhoea?

Answer 22

Undigested lactose is fermented by bacteria, or lactose travels to the small intestine where it lowers the water potential in the lumen, water travels into the small intestine by osmosis and causes diarrhoea.

Question 23

Outline the non reducing sugars test.

Answer 23

1. First you have to break them down into monosaccharides by boiling with HCL.
2. Then neutralise it with sodium hydrogen carbonate.
3. Then carry out the Benedict’s test.
4. Then carry the Benedict’s test again to rule out it being a reducing sugar.

Question 24

When Benedict’s reagent is added to a reducing sugar what would you expect to see?

Answer 24

The solution would turn brick red with a red precipitate.

Question 25

Which two polysaccharides make up starch?

Answer 25

Amylose and amylopectin

Question 26

What test do you carry out to test for starch?

Answer 26

Add iodine dissolved in potassium iodide solution to the sample. If starch is present the sample changes from brown to blue/black.