Transcript 3.3_Digestive_System

IB Biology Review
Digestive System
What are the components of the
human digestive system?
Mouth
Salivary glands
Esophagus
Stomach
Small intestine
Liver
Gall bladder
Pancreas
Large intestine
Identify the components of the
human digestive system.
Mouth
Salivary glands
Esophagus
Stomach
Small intestine
Liver
Gall bladder
Pancreas
Large intestine
Be able to draw this schematic.
Bile
Where is bile made?
Liver
What is the role of bile in digestion?
Acts on fats and lipids
Breaks down fat into smaller droplets of fat
Why is this useful for the body?
This creates more surface area on which
enzymes can act
Digestive Enzymes
Fill in the table
Work left to right
Small Intestine and Villi
What is the benefit of villi and
microvilli in the small intestine?
Villi and microvilli increase the surface area of
the small intestine
Why is more surface area good?
It means the small intestine can be more efficient
Can absorb more nutrients, proteins, minerals
1. Draw a diagram of the human
digestive system.
(7 marks)
Must include
Mouth
Esophagus
Stomach
Small intestine
Liver
Gall bladder
Pancreas
Large intestine
2. State where bile is synthesized and
explain its role in digestion. (3 marks)
Synthesized in liver cells;
Acts on fats / lipids;
Emulsifies / breaks down fat into smaller
droplets of fat;
This creates more surface area on which
enzymes can act;
3. Draw a diagram of a villi in
vertical section.
(4 marks)
Must show
Lacteal
Capillary network
Epithelial cells
Microvilli
4. State the source, substrate, products and
optimum pH conditions for one amylase,
one protease and one lipase.
(8 marks)
5. Describe the role of enzymes in the process of
digestion of proteins, carbohydrates, and lipids in
humans.
(6 marks)
protease / trypsin / pepsin digest proteins into
polypeptides / dipeptides / amino acids / peptides;
lipase digests lipids into glycerol / fatty acids;
amylase digests polysaccharides into disaccharides /
monosaccharides;
enzymes must match products;
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;
6. State the sources, substrate, product, and
optimum pH conditions for the enzyme
amylase.
(4 marks)
Sources
salivary glands;
pancreas;
Substrate
starch / glycogen (do not accept carbohydrate)
Product
maltose / disaccharide;
Optimum pH
7-8 / neutral – slightly alkaline;
7. Which organ secrets enzymes
that are active at a low pH? (1 mark)
A.
B.
C.
D.
Mouth
Pancreas
Stomach
Liver
Correct answer: C
8. Describe the role of enzymes in
digestion with reference to two named
examples.
(5 marks)
large food molecules must be broken down;
such as carbohydrates / proteins etc. ;
by hydrolysis of bonds / to form monomers;
rate of reaction at body temperature too slow;
enzymes increase the rate of breakdown / act as
catalysts;
first enzyme example – name, substrate, and
product;
second enzyme example –name, substrate,
product;