2.3 human digestive system

Sistem Penghadaman Manusia

Alimentary canal

Mouth

Esophagus

Stomach

Duodenum

Small intestine

Large intestine

Rectum

Anus

Food (Rice) in mouth is chewed + Saliva

Food bolus move along esophagus

Arrived stomach-hold food, secretes gastric jus

Liver, released bile to emulsify fat

Duodenum-receive bile and pancreas jus

Small intestine-secretes intestinal juice-absorbed food into blood

Large intestine-formation faeces

Anus-remove faeces from body

Rectum-stored faeces

Process of Digestion

1. The digestive process involves breakdown of food from complex to simple form in the alimentary canal

2. Sequence in the digestive process:

Food

Ingestion

Physical and chemical digestion

Defecation

Absorption

Assimilation

Outside the body

Alimentary canal

Body cells and tissues

IngestionThe process of intake of food in solid/liquid forms into the alimentary canal.

DigestionPhysically and chemically in the digestive system.

Defecation Undigested food will be disposed

Absorption a.blood circulatory system b.lymphatic system

Assimilation In body cells :a.growth b.cellular respiration (to

release energy)

Process of digestion

Physical digestion Chemical digestion

-mechanical process -breaking down food into smaller particles

-using the teeth

-Action of various enzymes -The end products are simpler molecules which are soluble.

Digestion of carbohydrates starts in the mouth

Digestion of proteins starts in the stomach

Digestion of fats starts in the small intestine

Digestion of carbohydrates, proteins and fats ends in the small intestine

Amylase enzyme

Mouth

Starch molecules

Enzymes break down starch molecules

Glucose molecules

1. Digestion begins in the mouth.

2. The teeth chew and grind food into smaller particles

Saliva contains

amylase enzymemaltose, a type of sugar.

Starch

Enzyme amylase

maltoseAlkaline medium

Peristalsis

Inside esofhagus, no food digestion occurs

Peristalsis

Inside esophagus, no food digestion occurs

Peristalsis

Inside esophagus, no food digestion occurs

Peristalsis

Inside esophagus, no food digestion occurs

Peristalsis

Inside esophagus, no food digestion occurs

lumen

Wall constricts

wall dilates Direction of movement of food

food mass

Contraction of the wall of the digestive tract

The digested food is pushed to the stomach by the contraction and relaxation of the walls of the esophagus

The wave-like contraction of the esophagus muscles are known as peristalsis.

Date:

Experiment: 2.4

Aim: To test the action of salivary amylase on

starch

Diagram:

Procedure:

1.My mouth was rinsed with distilled water and

spat out.

2.My mouth was rinsed again with some distilled

and the water was spat into a beaker. The

saliva solution were collected.

3. 5 cm3 of starch solution were poured into a

test tube labeled P.

4. 5 cm3 of saliva solution were added to test

tube P.

5. The mixture was stirred with a glass rod. Test

tube P was placed into a water bath at 370C

and the stopwatch was started.

6. 2 cm3 of the mixture were poured from test

tube P into two separate test tubes immediately

7. The iodine test and Benedict’s test were carried out on the mixtures in the two separate

test tubes.

8. After 30 minutes, 2cm3 of the mixture were

poured from test tube P into two other test tubes and the iodine test and Benedict’s test were carried out on the mixtures again.

9. All my observations were recorded in the table.

Procedure:

1. Rinse your mouth

2. Rinse your mouth again and spit the water into the a beaker.

3. Pour 5cm3 of starch solution into test tube.

4. Add 5 cm3 of saliva solution to test tube.

5. Stir the mixture.

6. Place the test tube into the water bath. Start the stop watch.

7. After 2 minutes, pour 2cm3 of the mixture into two separate test tube.

8. Carry out the iodine test and Benedict’s test.

9. After 30 minutes, repeat steps 6 -7 again.

Food test At the beginning of the activity

At the end of the activity

Observation Inference Observation Inference

Iodine test

Benedict’s test

Observation:

Food test At the beginning of the activity

At the end of the activity

Observation Inference Observation Inference

Iodine test Dark-blue solution

Starch is present

Brown solution

Starch is absent

Benedict’s test

Blue solution

Glucose is absent

Brick-red precipitate

Glucose is present.

Observation:

Conclusion:

The enzyme in saliva breaks down starch to form _________

amylaseStarch maltose

Discussion:

1.Why must you rinse your mouth with distilled water before collecting the saliva solution?

-to ensure that the saliva does not contain sugar

2. Why must you place test tube P into the water bath at 370C?

-The optimum temperature for salivary amylase is 370C.

3. What effect did your saliva have on the starch solution?

- Saliva digested starch by changing it into sugar that gives a positive result to the Benedict’s test.

4. Variables:

i) Fixed : Temperature of water (370C)

ii) manipulated: presence of enzyme

iii) responding : presence of maltose

Digestion of proteins starts in the stomach

Digestion in stomach

1.The stomach - acts as a bag to store food

2. When food enters the stomach, the stomach wall will secrete gastric juice that contains:i) Hydrochloric acid,

ii)Enzyme pepsin

(a form of protease)

Functions of hydrochloric acid:i. Prevent food from decayingii.Kill bacteria that may be found in foodiii.Stop the action of salivary amylaseiv.Prepared an acidic medium

The stomach wall will secrete mucus to protect stomach tissue from corrosion by the hydrochloric acid.

pepsin enzyme

Proteins Polypeptides

Digestion of food in stomach takes about

2 – 4 hours.

Then food is sent from the

stomach to the small intestines in semi-solid form known as chyme.

Date:

Experiment: 2.5

Aim: Action of enzyme in the stomach on proteins

Hypothesis: Enzyme in the stomach can convert proteins into polypeptides (or peptones)

Variables:

i) Fixed : temperature of water bath (370C)

ii)Manipulated: presence of water

iii)Responding: presence of proteins

Procedure:

1.Four test tube were labelled as A, B, C, and D

2.The following mixtures were poured into each test tube:

Test tube Mixtures

A 1cm3 of egg albumin

2cm3 of pepsin solution

2cm3 of dilute hydrochloric acid

B 1cm3 of egg albumin

2cm3 of dilute hydrochloric acid

Test tube

mixtures

C 1cm3 of egg albumin

2cm3 of pepsin solution

2cm3 of distilled water

D 1cm3 of egg albumin

2cm3 of distilled water

3. Four test tube were then immersed in a water

bath at 370C for 2 hours.

4. Then the egg albumin in each test tube was observed.

Observations:

Conclusion:

In acidic state, the enzyme _______ will convert _______to _______(peptones)

-if the temperature of the water bath is too high, the pepsin and protein will be destroyed. This condition is called denaturalisation.

Test tube Observations

A Egg albumin has dissolved

B Egg albumin is still in the test tube

C Egg albumin is still in the test tube

D Egg albumin is still in the test tube