1. What is nutrition?
2. How the different mode of nutrition be differentiated?
4. What is ingestion?
5. What is digestion?
6. What is absorption?
7. What is assimilation?
8. What is metabolism?
9. What is egestion?
10. The 5 processes above do not work in an entirely continuous manner.
11. What are the two parts that make up the human digestive system?
12. List the names of the structures of the human alimentary canal?
13 What are the digestive glands involved in the digestive system? What are the names of the digestive juice secreted by these glands? What are the locations of which these juices are secreted to?
15. What is the importance of chewing?
16. What are the four types of human teeth? What are their shapes and their functions?
17. How many roots do the four types have human teeth have?
18. What is dentition?
19. What is dental formula?
20. What is the dental formula of human milk teeth?
21. What is the dental formula of human permanent teeth?
22. How can teeth are there for human milk teeth and permanent teeth?
23. What are the external structures of the teeth? How can the location of these external structure be defined?
24. Whart are the internal structure of the teeth?
25. Which part of the tooth consists of dead tissue?
26. Which part of the teeth must the decayed part of the tooth reach before a person will feel pain?
27. Which part of the teeth is the hardest? Why?
28. What structures fix the tooth to the jawbone?
29. What are the features and functions of dentine?
30. What is present in the pulp cavity? What are their functions?
31. What kind of food substances can be absorbed without digestion?
32. What are the two types of digestions?
33. What is physical digestion / mechanical digestion?
34. What is the importance of physical digestion?
35. Which type of digestion, physical or chemical, is more important? Why?
36. What are the three types of digestive enzymes?
37. Which parts of the alimentary canal can secrete mucus?
38. Where can starch in the alimentary canal be first digested?
39. What is contained inside saliva?
40. What is the process of swallowing?
41. How is peristalsis of the alimentary canal carried out? What it the function of peristalsis?
42. What is the importance if peristalsis?
43. What are the muscles at the entrance and the exit of the stomach called?
44. What are the functions and importance of the cardiac and pyloric sphincter respectively?
45. What are contained in the gastric juice secreted by the gatric glands?
46. What are the functions of Hydrochloric acid in the gastric juice?
47. What is the function of protease?
48. Which part of the alimentary canal does protein start being digested?
49 What is the function of mucus in the alimentary canal?
50. What is chyme?
51. Where does lipids start being digested?
52. Theoretically, what is the location at which starch, protein and lipid are completely digested?
53. What is the meaning of emulsification?
54. List the names, site of production and site of action of the enzymes secreted at the alimentary.
55. What should carbohydrates, protein and lipid be digested into until they can be absorbed?
56. What is the function of the stomach?
57. How can pancreatic juice from the pancreas reaches duodenum?
58. What are the materials inside pancreatic juice?
59. What are the differences between the protease at the stomach and pancreatic protease?
60. What is the composition of intestinal juice?
61. What are the digestive juices that will be secreted to the duodenum? Where do they come from?
62. What are the functions of the carbohydrases on the epithelium of the inner wall of the small intestine?
63. If gall stones is blocking the bile duct, the gall bladder may be surgically removed. How would the digestion of lipid be affected if the gall bladder is removed? Explain.
64. What food molecules are brought away by the blood capillaries?
65. What food molecules are brought away by the lacteal?
66. Where is water being absorbed the most?
67. What is the main function of the large intestine?
68. Normally, what substances are there inside faeces? (list at least 7)
69. What are the functions of the liver?
70. How can the liver regulate the blood glucose level?
71. How is defaecation carried out?
1. What is nutrition?
It is the process of which organisms obtain food.
2. How the different modes of nutrition be differentiated?
Autotrophic nutrition is referring to the mode of nutrition of which organisms can make their own food.
Heterotrophic nutrition is referring to the mode of nutrition of which organisms cannot make their own food, it can be differentiated into three different types according to the following principles:
1. Organisms need to digest the food inside their bodies – holozoic nutrition
2. Organisms need to digest the food outside their bodies – saprophytic nutrition
3. Organism do not need to digest food but obtain food of absorbable form from other living things – parasitic
4. What is ingestion?
The process of which food enter the alimentary canal through the mouth cavity.
Note: The process is completed only when the food enters the alimentary canal.
5. What is digestion?
The process of which food is broken down into soluble, absorbable form.
Note: When food is not digested into absorbable form, digestion is still not completed.
6. What is absorption?
The process of which soluble food molecules enters the circulatory system.
7. What is assimilation?
The process of which small and soluble food molecules absorbed such as amino acid,
fats and monosaccharides such as glucose, fructose and galactose in the blood are absorbed into cells and then used in metabolism and converted to the form that is required by the body.
8. What is metabolism?
All chemical reaction inside the cells.
9. What is egestion?
The process of which undigestible substances and unabsorbed substances that are not yet digested are expelled from the body.
Note: Urination and sweat and carbon dioxide are products of excretion and not egestion because excretion by definition is the removal of metabolic waste from the body. Urea (NH3) in urine and sweat, carbon dioxide (CO2) produced in respiration are all metabolic waste.
10. The 5 processes above do not work in an entirely continuous manner.
They work in the following manner.
11. What are the two parts that make up the human digestive system?
(1) alimentary canal
(2) digestive glands
12. List the names of the structures of the human alimentary canal?
Mouth cavity a oesophagus à stomach à small intestine (including duodenum and ileum), large intestine (including caecum, appendix, colon, rectum), and anus.
13 What are the digestive glands involved in the digestive system? What are the names of the digestive juice secreted by these glands? What are the locations of which these juices are secreted to?
(1) Gland: salivary gland,
Digestive juice:__ saliva ______________________ ,
Location:__ mouth cavity ______________________________
(2) Gland: gastric glands
Digestive juice:__ gastric juice __________________________ ,
Location:____ stomach ______________________________
(3) Gland: pancreas
Digestive juice:__ pancreatic juice ________________________ ,
Location:____ duodenum ____________________________
(4) Gland: liver
Digestive juice:__bile _______________________________ ,
Location:____ duodenum ________________________
14. What is chewing?
The process of which food is broken down into small pieces in the mouth cavity.
15. What is the importance of chewing?
(1) helps swallowing
(2) increase the surface area for enzymes to work on food more effectively
16. What are the four types of human teeth? What are their shapes and their functions?
Incisor: Like a chisel with sharp edges. Used for cutting food.
Canine: Pointed and curved. Used for tearing food.
Premolar: Broad top with cusps. Used for crushing and grinding food.
Molar: Broad top with cusps. Larger than premolars. Used for crushing and grinding food.
17. How many roots do the four types have human teeth have?
(1) Incisor: 1
(2) Canine: 1
(3) Premolar: 1 or 2
(4) Molar: 2 or 3
18. What is dentition?
It is the number of different types of mammalian teeth and their arrangement on the jaw.
19. What is dental formula?
It shows the numbers and types of teeth on each side of the upper and lower jaw.
20. What is the dental formula of human milk teeth?
2102/2102
21. What is the dental formula of human permanent teeth?
2123/2123
22. How can teeth are there for human milk teeth and permanent teeth?
Milk teeth: 20
Permanent teeth: 32
23. What are the external structures of the teeth? How can the location of these external structure be defined?
(1) crown: the visible region above the gum
(2) neck: the part of the tooth enclosed by the gum
(3) root: the part of the tooth embedded in the jaw bone.
24. Whart are the internal structure of the teeth?
Enamel, dentine, pulp cavity, periodontal membrane, nerve fibre, blood vessels, cement
25. Which part of the tooth consists of dead tissue?
Enamel
Note: Dentine contains living cells.
26. Which part of the teeth must the decayed part of the tooth reach before a person will feel pain?
Dentine
27. Which part of the teeth is the hardest? Why?
Enamel
Because it composes mainly of calcium salt.
28. What structures fix the tooth to the jawbone?
Cementum and periodontal membrane
29. What are the features and functions of dentine?
Its composition is similar to bones. Its hardness is lesser than enamel. There is living cytoplasm inside it.
It replenishes worn out enamel. (But in human, the dentine does not bear this function)
30. What is present in the pulp cavity? What are their functions?
(1) living cells: nourishes the dentine
(2) blood vessels: supply nutrients to the teeth and bring away wastes.
(3) nerve fibers: detect temperature and pressure
31. What kind of food substances can be absorbed without digestion?
Water, vitamins and minerals
32. What are the two types of digestions?
(1) Chemical digestion
(2) Physical digestion / mechanical digestion
33. What is physical digestion / mechanical digestion?
(1) The mechanical movement of the alimentary canal including
- chewing in the mouth cavity
- churning of the stomach
- Peristalsis of the alimentary canal
(2) Emulsification of lipids by bile salt from the small intestine.
34. What is the importance of physical digestion?
It can increase the surface area of food to facilitate chemical digestion by enzymes.
35. Which type of digestion, physical or chemical, is more important? Why?
Chemical digestion. This is because physical digestion cannot digest food into absorbable form.
36. What are the three types of digestive enzymes?
(1) carbohydrases
(2) proteases
(4) lipases
Note:
(1) Enzymes catalyse / speed up the breakdown of food substances.
(2) Most enzymes have suffix ( -ase)
37. Which parts of the alimentary canal can secrete mucus?
All parts of the whole alimentary canal.
38. Where can starch in the alimentary canal be first digested?
Mouth cavity (starch à maltose)
39. What is contained inside saliva?
(1) salivary amylase
(2) mucus
(3) water
40. What is the process of swallowing?
(1) The tongue rises and pushes the bolus towards the pharynx.
(2) Soft palate moves up to prevent the bolus from entering the nasal cavity.
(3) The larynx rises and the epiglottis covers the opening of the trachea.
(4) Food bolus enters the oesophagus.
41. How is peristalsis of the alimentary canal carried out? What it the function of peristalsis?
By the alternate contraction and relaxation of the longitudinal muscles and circular muscles in the wall of the alimentary canal.
Function: to push the bolus(better answer) / food (acceptable answer) forward.
42. What is the importance if peristalsis?
(1) It pushes food along the alimentary canal
(2) It helps mix the food with the digestive juices
(3) It increases the contact between the wall of the alimentary canal and digested food to facilitate absorption.
43. What are the muscles at the entrance and the exit of the stomach called?
Entrance: cardiac sphincter
Exit: pyloric sphincter
44. What are the functions and importance of the cardiac and pyloric sphincter respectively?
Cardiac sphincter can contract to prevent back flow of food into the oesophagus.
Pyloric sphincter can contract to control the release of food into the duodenum.
45. What are contained in the gastric juice secreted by the gastric glands?
(1) Pepsin (A kind of protease)
(2) Hydrochloric acid (HCl)
(3) mucus
46. What are the functions of Hydrochloric acid in the gastric juice?
(1) Kill most bacteria in the food.
(2) Provide an acidic environment for pepsin to work best.
47. What is the function of protease?
It catalyzes the break down of protein into peptides (still cannot be absorbed)
48. Which part of the alimentary canal does protein start being digested?
Stomach (proteinàpeptide)
49 What is the function of mucus in the alimentary canal?
It protects the wall of the alimentary canal, preventing it from being digested by digestive enzymes.
50. What is chyme?
After passing through the stomach, the food is being churned into a creamy liquid. In this state, it is called chyme.
51. Where does lipids start being digested?
Duodenum
52. Theoretically, what is the location at which starch, protein and lipid are completely digested?
ileum
53. What is the meaning of emulsification?
The breaking down of large lip globules in the small intestine into smaller oil droplets by the action of bile salts.
Note: No enzyme is involved.
54. List the names, site of production and site of action of the enzymes secreted at the alimentary.
Salivary amylase (mouth cavity, mouth cavity)
Protease (stomach, stomach)
Pancreatic amylase (pancreas, duodenum)
Pancreatic protease (pancreas, duodenum)
Pancreatic lipase (pancreas, duodenum)
Carbohydrases including maltase, sucrase and lactase (small intestine, small intestine - i.e. both duodenum and ileum)
Protease (small intestine, small intestine)
Note:
(1) Carbohydrases is a common name, there are three different kinds of this type of enzymes to digest disaccharides into monosaccharides.
(2) For proteases that turns peptides into amino acids, they are actually called peptidases. (but all are called proteases in HKDSE)
55. What should carbohydrates, protein and lipid be digested into until they can be absorbed?
Carbohydrate (monosaccharides)
Protein (amino acids)
Lipids (glycerol and fatty acids)
56. What is the function of the stomach?
(1) digest protein
(2) carry out physical digestion by churning
(3) kill bacteria
(4) mix up food
(5) store food when it is being digested
57. How can pancreatic juice from the pancreas reaches duodenum?
Pancreatic duct
58. What are the materials inside pancreatic juice?
(1) pancreatic amylase
(2) pancreatic protease
(3) pancreatic lipase
(4) sodium hydrogencarbonate (an alkaline)
59. What are the differences between the protease at the stomach and pancreatic protease?
The optimum pH (pH of which the enzyme works best) for pancreatic protease is around 8 and that for protease at the stomach is around 2.
Pancreatic proteases can catalyze the breakdown of protease into peptide and amino acids. Proteases at the stomach can only catalyze protein into peptides.
60. What is the composition of intestinal juice?
(1) water
(2) mucus
(3) sodium hydrogencarbonate
Note: There are no enzymes in intestinal juice. The enzymes maltase, sucrase, lactase and proteases are found embedded in the cell membrane of specialized cells on the inner surface (epithelium / epithelial tissue) of the small intestine.
61. What are the digestive juices that will be secreted to the duodenum? Where do they come from?
Pancreatic juice, from the pancreas
Bile, from the gall bladder, actually should be produced and secreted by the liver and temporarily stored in the gall bladder
Intestinal juice, from the wall of the small intestine.
62. What are the functions of the carbohydrases on the epithelium of the inner wall of the small intestine?
Catalyze the breakdown of disaccharides into monosaccharides
Maltose breaks down into glucose
Sucrose breaks down into glucose and fructose
Lactose breaks down into glucose and galactose
Note: Therefore there are at least three types of carbohydrases on the epithelium of the inner wall of the small intestine.
63. If gall stones is blocking the bile duct, the gall bladder may be surgically removed. How would the digestion of lipid be affected if the gall bladder is removed? Explain.
Gall bladder stores bile juice which is released when fatty food is present in the small intestine.
Bile juice contains bile salts for emulsification of fat to provide a large surface area for action of lipases/enzymes.
If the gall bladder is removed, bile will still be secreted, but not stored. This will slow down lipid digestion,
since the small amount of bile may not be enough for digestion of lipids in
our diets.
64. What food molecules are brought away by the blood capillaries?
Basically all materials soluble in water including
Monosaccharides, amino acids, minerals, water soluble vitamins (e.g. vitamin C)
65. What food molecules are brought away by the lacteal?
fat, fat soluble vitamins (A & D)
Note: fat/lipid will be reformed when fatty acids and glycerols enters the epithelial cells.
66. Where is water being absorbed the most?
Small intestine.
Actually all food molecules are absorbed the most here.
67. What is the main function of the large intestine?
(1) absorb some of the remaining water
(2) absorb some of the remaining minerals and vitamins
68. Normally, what substances are there inside faeces? (list at least 7)
Undigested food, indigestible food (e.g. dietary fibre), digested but unabsorbed food, mucus, bile pigment (the reason for the brown colour of faeces), secretions from the alimentary canal, water, sloughed off cells from the canal wall.
69. What are the functions of the liver?
(1) Regulate blood glucose level
(2) Deamination of excess amino acids
(3) Assist digestion by producing bile
(4) Store glycogen, iron and fat-soluble vitamins
(5) Produce vitamin A from carotene
(6) Detoxification
(7) Convert excess carbohydrates and amino acids into lipids
70. How can the liver regulate the blood glucose level?
When the blood glucose level increase, the liver will change the excess glucose into glycogen and store in the liver.
When the blood glucose level decrease, the liver will change the glycogen into glucose.
71. How is defaecation carried out?
Anal sphincter relax
Muscles of rectum contract
Faeces are pushed out through the anus