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New Senior Secondary Mastering Biology Oxford University Press 2014 (Second Edition)

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6 Nutrition in humans

6.1 The human digestive system (Book 1A, p. 6-3)

� (1) _______________ (營養) in humans consists of five main processes:

� Nutrition in humans takes place in the (12) _______________ system (消化系統), which

consists of the (13) _______________ _______________ (消化道) and its associated

(14) _______________ _______________ (消化腺).

� (2) _______________ (攝食):

Food is taken in through the

(3) _______________.

� (4) _______________ (消化):

Food is broken down into

(5) _______________ and simple

molecules.

� (6) _______________ (吸收):

The soluble and simple food molecules

enter the (7) _______________ system.

� (8) _______________ (同化):

The absorbed food molecules are taken

up by cells for (9) _______________.

� (10) _______________ (排遺):

The undigested and unabsorbed

materials are removed from the body as

(11) _______________ (糞便).

digested food

undigested food


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� The human digestive system:

� The alimentary canal receives (26) _______________ _______________ (消化液) secreted

from a number of digestive glands, e.g. the salivary glands, the pancreas and the liver.

� Go to

Practical 6.1 Examination of the mammalian digestive system

(Book 1A, p. 6-5; Practical Workbook for SBA 1A, p. 6-1)

tooth

tongue

(15) _______________

_______________ (唾腺)

liver (肝)

(16) _______________

_______________ (膽囊)

bile duct (膽管)

mouth cavity (口腔)

small intestine (小腸)

(17) _______________

(十二指腸)

(18) _______________

(迴腸)

(19) _______________

(肛門)

(20) _______________ (咽)

(21) _____________ (食道)

(22) _______________ (胃)

(23) _______________ (胰)

large intestine (大腸)

(24) _______________

(結腸)

caecum (盲腸)

appendix (闌尾)

(25) _______________

(直腸)

pancreatic duct (胰管)


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6.2 Ingestion (Book 1A, p. 6-6)

� In the mouth cavity, food is cut up into small pieces by the (1) _______________. The process

of chewing food into small pieces is called (2) _______________ (咀嚼).

A What types of teeth do we have? (Book 1A, p. 6-6)

Type of tooth Shape Function

(3) _______________

(門齒)

� (4) _______________-shaped

(鑿形的), with flat sharp edges

� Has one root

Biting and

(5) _______________

food

(6) _______________

(犬齒)

� (7) _______________ and

curved

� Has one root

(8) _______________

flesh

(9) _______________

(前臼齒)

� Broad top with

(10) _______________ (尖突)

� Has one or two roots

(11) _______________

(臼齒)

� Similar to premolars but

(12) _______________

(larger / smaller)

� Has two or three roots

(13) ______________ and

(14) ______________

food

B What is the dentition of humans? (Book 1A, p. 6-7)

� (15) _______________ (齒系) refers to the numbers and arrangement of different types of teeth

in a mammal. It can be represented by a (16) _______________ _______________ (齒式).

� Humans have two sets of teeth:

(17) ______________ ______________ (乳齒) (19) ______________ ______________ (恆齒)

� Appear during the first two years of life

� Dentition: (18) _______________

� Replace the milk teeth between the ages of

6 and 12

� Dentition: (20) _______________


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C What is the structure of a tooth? (Book 1A, p. 6-8)

� Each tooth consists of three layers:

Layer Feature

Enamel

� The outermost, hardest part of the crown

� Non-living, made mainly of (29) _______________ salts

� Protects the tooth from wearing down

� Replaced by (30) _______________ around the roots. The cement and the

(31) _______________ _______________ fix the tooth to the jawbone

Dentine

� The middle region of the tooth

� A (32) _______________-like substance; not as hard as the enamel

� With strands of living (33) _______________ running through

Pulp cavity

� Contains (34) _______________ (living / non-living) cells

� Contains (35) _______________ _______________ to supply oxygen and

nutrients to the tooth, and remove wastes from it

� Contains (36) _______________ _______________ which detect

temperature and pressure

(21) _______________

(齒冠)

(22) _______________

(齒頸)

(23) _______________

(齒根)

(24) _______________ (琺瑯質)

(25) _______________ (牙本質)

(26) _______________

_______________ (髓腔)

(27) _______________

_______________ (牙周膜)

(28) _______________ (牙骨質)

gum (齒齦)

jawbone (顎骨)

▲ Structure of a canine


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6.3 Digestion (Book 1A, p. 6-11)

A Why is digestion necessary? (Book 1A, p. 6-11)

� The wall of the alimentary canal is (1) _______________ permeable. Large, complex food

molecules must be broken down into small, (2) _______________ molecules so that they can

pass through the wall and enter the blood.

� The process of breaking down food into small molecules is called (3) _______________.

B Physical digestion and chemical digestion (Book 1A, p. 6-11)

1 Physical digestion (機械消化)

� It is the breaking down of food into smaller pieces by physical actions.

� It increases the (4) _______________ _______________ of food in contact with the digestive

juices.

� It is brought about by:

- Chewing in the mouth cavity, i.e. (5) _______________

- (6) _______________ (劇烈攪動) in the stomach

- (7) _______________ along the alimentary canal

- (8) _______________ (乳化) of lipids by bile salts (膽鹽) in the small intestine.

2 Chemical digestion (化學消化)

� It involves (9) _______________ reactions in which large, complex food molecules are

broken down into small, simpler forms. The reactions are catalysed by (10) _______________

_______________ (消化酶).

� Three main types of digestive enzymes in our digestive system:

Type of enzyme Function

I Carbohydrases (碳水化合物酶) a Break down proteins into polypeptides,

peptides and amino acids

II Proteases (蛋白酶) b Break down lipids into fatty acids and

glycerol

III Lipases (脂肪酶) c Break down complex carbohydrates into

simpler sugars

I: (11) _____________ II: (12) ____________ III: (13) ____________


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C Digestion in the mouth cavity (Book 1A, p. 6-12)

� In the mouth cavity, food is chewed into smaller pieces by the teeth and mixed with

(14) _____________ (唾液), which contains:

Component Function

(15) _______________

_______________

(唾液澱粉酶)

� Catalyses the breakdown of starch into (16) ____________

(17) _______________

(黏液)

� Helps bind food particles together

� Moistens and (18) _______________ the food

Water � (19) _______________ soluble substances in the food

� After chewing, the tongue rolls the food into a (20) _______________ (食團), which is then

swallowed down the oesophagus through the pharynx.

� When the bolus enters the oesophagus, it is pushed down the oesophagus to the stomach by

(23) _______________, which is produced by the alternate contraction and relaxation of

the (24) _______________ muscles (縱肌) and (25) _______________ muscles (環肌) in the

wall of the alimentary canal.

� Peristalsis has the following importance:

- It pushes food along the oesophagus and other parts of the alimentary canal.

- It helps (26) _______________ the food with the digestive juices.

- It increases the (27) _______________ between the wall of the alimentary canal and

digested food to facilitate (28) _______________.

nasal cavity

trachea

▲ The swallowing process

1 The tongue rises to push the bolus towards the pharynx.

2 The soft palate (軟腭) moves up to prevent the bolus from

entering the (21) ______________ ______________.

3 The larynx rises so that the epiglottis (會厭) covers the

opening to the trachea. This prevents the bolus from entering

the (22) _______________.

4 The bolus enters the oesophagus.


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D Digestion in the stomach (Book 1A, p. 6-13)

� The entrance of the stomach is guarded by the (29) _______________ _______________

(賁門括約肌). The exit is guarded by the (30) _______________ ______________ (幽門括約肌).

� Gastric glands (胃腺) on the stomach wall produce (31) ____________ _____________ (胃液),

which contains:

Component Function

(32) _______________

(胃蛋白酶)

� Catalyses the breakdown of proteins into (33) ______________

� Works best in an (34) _______________ (acidic / alkaline)

medium

(35) _______________

_____________ (氫氯酸)

� Provides an acidic medium for the action of pepsin

� Kills most (36) _______________ in food

Mucus

� Protects the stomach wall from being digested by the

(37) _______________ and being damaged by the

(38) _______________ _______________

� Muscles in the stomach lining contract to churn the food into (39) _______________ (食糜),

which is then released into the duodenum.

E Digestion in the small intestine (Book 1A, p. 6-16)

1 Bile

� (40) _______________ (膽汁) is produced by the (41) _______________. It is temporarily

stored in the (42) _______________ _______________ and is released through the bile duct

into the (43) _______________. Bile contains:

Component Function

Bile salts � (44) _______________ lipids into small droplets to

facilitate the chemical digestion of lipids

(45) _______________

_______________ (膽色素) � Do not take part in digestion

(46) _______________

_______________ (碳酸氫鈉)

� (47) _______________ the acidic chyme

� Provides an (48) _______________ (acidic / alkaline)

medium for the action of enzymes in the small intestine


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2 Pancreatic juice

� Pancreatic juice is produced by the (49) _______________. It is carried along the

(50) _______________ _______________ to the duodenum. Pancreatic juice contains:

Component Function

Pancreatic amylase � Catalyses the breakdown of the remaining starch into maltose

(51) _______________ � Catalyse the breakdown of some proteins into peptides, and

some peptides into amino acids

Pancreatic lipase � Catalyses the breakdown of the emulsified lipids into

(52) _____________ _______________ and glycerol

Sodium

hydrogencarbonate

� Neutralizes the acidic chyme

� Provides an (53) _______________ (acidic / alkaline) medium

for the action of the enzymes in the small intestine

3 Intestinal juice

� Intestinal juice is produced by some glands in the wall of the small intestine. It is slightly

(54) _______________ (acidic / alkaline).

� It mainly contains water, mucus and sodium hydrogencarbonate.

� The (55) _______________ of the small intestine has specialized cells that have various

enzymes on their cell membranes. These enzymes include:

Enzyme Function

(56) _______________ Catalyse the breakdown of disaccharides into monosaccharides

(57) _______________ Catalyse the breakdown of some peptides into amino acids

� Go to

Practical 6.2 Investigation of the action of pepsin


Practical 6.3 Demonstration of the effect of bile salts on oil



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6.4 Absorption (Book 1A, p. 6-20)

� Absorption of food molecules mainly takes place in the (1) ______________.

A How is the small intestine adapted for absorption? (Book 1A, p. 6-20)

Feature Adaptation for absorption

� Being very long

� Inner wall highly-(2) ______________

with numerous (3) ______________

� Numerous (4) ______________ on the

epithelial cells of villi

Increase the (5) _____________ _____________

for absorption

Thin (6) ______________ Reduces the (7) ______________ for diffusion

of food molecules into the blood

Presence of lacteals and a network of

(8) ______________

Allow the absorbed food molecules to be carried

away rapidly, thus keeping a steep

(9) ______________ ______________ of food

molecules across the wall of the small intestine to

increase the rate of (10) ______________

Movement of the villi caused by

(11) ______________

Keeps a steep concentration gradient of food

molecules across the wall of the small intestine

small intestine

villi (絨毛) a villus

lacteal (乳糜管)

capillaries

epithelial cell of villus

mircovilli (微絨毛)

mitochondria

▲ Structure of the small intestine showing the villi


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B How is digested food absorbed? (Book 1A, p. 6-21)

1 Absorption into the blood

� Water-soluble food molecules, e.g. monosaccharides, amino acids, minerals and water-

soluble vitamins, can be absorbed into the capillaries by (12) ______________ and

(13) ______________ ______________.

� As the absorption of digest food into the blood (14) ______________ (increases / decreases)

the water potential of the content in the small intestine, water is drawn into the blood by

(15) ______________.

2 Absorption into the lymph

� Fatty acids and glycerol enter the epithelium of the villi by (16) ______________. In the

epithelial cells, they recombine into fine (17) ______________ ______________, which then

enter the lacteals of the lymphatic system. (18) ______________-______________ vitamins

are also absorbed into the lacteals.

� The lipids and lipid-soluble vitamins in the lacteals are transported to the main

(19) ______________ ______________ (淋巴管), and eventually to the bloodstream near the

neck region.

� Go to

Practical 6.4 Simulation of digestion and absorption in the small intestine using dialysis tubing


capillary

lacteal

epithelial cell

monosaccharides

amino acids minerals,

water-soluble vitamins

fine lipid droplets

fatty acids

glycerol lipid-soluble vitamins


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6.5 Assimilation of the absorbed food (Book 1A, p. 6-26)

� Assimilation is the uptake and use of absorbed food molecules by cells for (1) ______________.

A How is the absorbed food transported to other parts of the body? (Book 1A, p. 6-26)

� Transport of absorbed food from the villus to other parts of the body through different vessels:

a aorta (大動脈) b hepatic portal vein (肝門靜脈) c hepatic vein (肝靜脈)

d lymph vessel e vena cava (腔靜脈)

(2): ________ (3): ________ (4): ________ (5): ________ (6): ________

B What are the fates of the absorbed food? (Book 1A, p. 6-27)

Absorbed food Fate

Glucose � Used by body cells for releasing (7) ______________

� Converted to (8) ______________ or lipids for storage if in excess

Amino acids � Used by cells to make (9) ______________

� (10) ______________ in the liver if in excess

Lipids

� Used by cells to make cell membranes and some hormones

� As energy (11) ______________

� Deposited around the internal organs or build up in (12) _____________

tissue if in excess

(3)

liver

(2)

villus

heart

(6)

all parts of the body

lipids and lipid-soluble vitamins monosaccharides,

amino acids, minerals and

water-soluble vitamins

(4) (5)


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C What are the roles of the liver? (Book 1A, p. 6-27)

The liver has the following functions:

� Regulation of the blood (13) ______________ level by converting excess glucose to

(14) ______________, which is stored in the liver, and converting the stored glycogen to

glucose, which is released into the (15) ______________

� Storage of glycogen, iron and (16) ______________-______________ vitamins

� Production of bile

� Production of vitamin A from (17) ______________

� (18) ______________ (脫氨作用): breaking down excess amino acids and converting the amino

groups into (19) ______________ (尿素)

� (20) ______________ (解毒)

6.6 Egestion (Book 1A, p. 6-30)

� In the large intestine, the undigested and unabsorbed materials form the (1) ______________.

� Faeces contain dietary fibre, bacteria, secretions from the alimentary canal, dead cells from

the intestinal wall and a small amount of water. They are brown in colour because of the

presence of (2) ______________ ______________.

� Faeces are temporarily stored in the (3) ______________.

� When the (4) ______________ ______________ (肛門括約肌) relaxes and the muscles of the

rectum contract, faeces are pushed out through the anus. The process of expelling faeces from

the body is called egestion or (5) ______________ (排糞).


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Answers

Ch 6 Nutrition in humans

6.1 1 Nutrition 2 Ingestion 3 mouth 4 Digestion 5 soluble

6 Absorption 7 circulatory 8 Assimilation 9 metabolism 10 Egestion

11 faeces 12 digestive 13 alimentary canal 14 digestive glands 15 salivary glands

16 gall bladder 17 duodenum 18 ileum 19 anus 20 pharynx

21 oesophagus 22 stomach 23 pancreas 24 colon 25 rectum

26 digestive juices

6.2 1 teeth 2 mastication 3 Incisor 4 Chisel 5 cutting

6 Canine 7 Pointed 8 Tearing 9 Premolar 10 cusps

11 Molar 12 larger 13 Grinding / Crushing 14 crushing / grinding

15 Dentition 16 dental formula 17 Milk teeth 18 2102/2102 19 Permanent teeth

20 2123/2123 21 crown 22 neck 23 root 24 enamel

25 dentine 26 pulp cavity 27 periodontal membrane 28 cement

29 calcium 30 cement 31 periodontal membrane 32 bone

33 cytoplasm 34 living 35 blood vessels 36 nerve fibres

6.3 1 differentially 2 soluble 3 digestion 4 surface area 5 mastication

6 Churning 7 Peristalsis 8 Emulsification 9 chemical 10 digestive enzymes

11 c 12 a 13 b 14 saliva 15 Salivary amylase

16 maltose 17 Mucus 18 lubricates 19 Dissolves 20 bolus

21 nasal cavity 22 trachea 23 peristalsis 24 longitudinal / circular

25 circular / longitudinal 26 mix 27 contact 28 absorption

29 cardiac sphincter 30 pyloric sphincter 31 gastric juice 32 Pepsin 33 peptides

34 acidic 35 Hydrochloric acid 36 bacteria 37 pepsin 38 hydrochloric acid

39 chyme 40 Bile 41 liver 42 gall bladder 43 duodenum

44 Emulsify 45 Bile pigments 46 Sodium hydrogencarbonate 47 Neutralizes

48 alkaline 49 pancreas 50 pancreatic duct 51 Proteases 52 fatty acids

53 alkaline 54 alkaline 55 epithelium 56 Carbohydrases 57 Proteases


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6.4 1 ileum 2 folded 3 villi 4 microvilli 5 surface area

6 epithelium 7 distance 8 capillaries 9 concentration gradient

10 diffusion 11 peristalsis 12 diffusion 13 active transport 14 increases

15 osmosis 16 diffusion 17 lipid droplets 18 Lipid-soluble 19 lymph vessels

6.5 1 metabolism 2 b 3 c 4 e 5 a

6 d 7 energy 8 glycogen 9 proteins 10 Deaminated

11 reserves 12 adipose 13 glucose 14 glycogen 15 blood

16 lipid-soluble 17 carotene 18 Deamination 19 urea 20 Detoxification

6.6

1 faeces 2 bile pigments 3 rectum 4 anal sphincter 5 defaecation

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