Digestion

Question 1

Draw a labeled diagram of the human digestive system.

5 mark

Answer 1

mouth/ teeth/ tongue
esophagus
stomach
small intestine
large intestine/colon
anus
rectum
sphincters
salivary glands
liver
pancreas
gall bladder

Question 2

Describe the role of enzymes in the digestion of proteins, carbohydrates and lipids in humans.

6 marks

Answer 2

• protease/trypsin/pepsin/chumotrypsin/other named - - protease digest proteins into polypeptides/ dipeptides/ amino acids/ peptides
• lipase digest lipids into glycerol/ fatty acids
• amylase digest polysaccharides into disaccharides/ monosaccharides
• speed up/ catalyze reactions/ increased efficiency
• lower the (activation) energy required for digestive reactions to occur
• occurs at body temperature
• require optimum pH
• enzymes are specific
• digestive enzymes carry out hydrolytic processes

Question 3

Draw a diagram of a villus in vertical section.

5 marks SL

Answer 3

lymph vessel
arteriole
venule
(central) lacteal
capillary network
epithelial layer/ lining/ epithelium
microvilli
goblet cells

Question 4

State the sources, substrate, product, and optimum pH conditions for the enzyme amylase.

Answer 4

sources: salivary glands and pancrease
substrate: starch (glycogen)
product: maltose
optimum pH: 7-8 (slightly alkaline)

Question 5

Explain how the structure of the villi in the small intestine are related to absorption of digested food.

3 marks

Answer 5

Microvilli
Rich capillary system (short transport path)
Singla layer epithelium
Lacteal
Intersital glands
Membrane proteins

• large surface area by microvilli / protrusion of exposed parts
• epithelium only one layer thick
• protein channels allow facilitated diffusion and active transport
• mitochondria provide ATP
• blood capillaries close to epithelium/ surface
• absorption of glucose/ amino acids
• lacteal / lymphatic vessel in center to absorb fats
• tight junctions assist in controlling absorption