Chapter 12 Question

New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________

Structured Questions Core Section |!|EQA01200001|!| Complete the following paragraph with suitable words selected from below: large intestine spleen

small intestine colon

stomach kidney

oral cavity oesophagus

saliva throat

pancreas gastric juice

Digestion begins at the moment food enters the mouth. After chewing by the teeth and moistening by (i)_________________, the food is pushed to the back of the (ii)_________________ by the tongue and swallowed. It is driven down the (iii)_________________ by muscular contractions and into the (iv)_________________, where the digestive juices liquidize it and begin to break it down into simpler compounds. The liquid then passes into the first part of the small intestine, where enzymes from the (v)_________________ and (vi)_________________ break it down further. The process of absorbing the nutrients in digested food into the blood occurs in the small intestine. (3 marks) ## (i)

saliva

(1/2 mark)

(ii)

throat

(1/2 mark)

(iii)

oesophagus

(1/2 mark)

(iv)

stomach

(1/2 mark)

(v)

pancreas

(1/2 mark)

(vi)

small intestine

(1/2 mark) _________ (3 marks)##

|!|EQA01200002|!| The following route shows the processes in the digestion of carbohydrates: Starch (i)

SiteAX

B

Site YC

Site Z

Where is site X? Name the enzyme working at site X.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________

(ii)

Name one test to test for starch and state the expected result.

(2 marks)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (iii)

What is A?

(1 mark)

_______________________________________________________________________________ (iv)

Name a test to test for A. Describe the procedure.

(4 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (v)

Name site Y. State the fluid found in site Y which contains enzymes to digest carbohydrates. (2 marks) _______________________________________________________________________________

(vi)

Is the medium in site Z acidic, neutral or alkaline?

(1 mark)

_______________________________________________________________________________ (vii) Enzyme P is denatured before entering site B. Explain how it happens.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ ## (i)

Site X is the oral cavity;

(1 mark)

the enzyme functioning in X is salivary amylase.

(1 mark)

Iodine test.

(1 mark)

The brown iodine solution turns the tested solution blue-black.

(1 mark)

(iii)

Maltose.

(1 mark)

(iv)

Benedict’s test.

(1 mark)

Equal volumes of solution A and Benedict’s solution are added to a test tube.

(1 mark)

The test tube is boiled in a water bath for 5 minutes.

(1 mark)

The test tube is shaken from time to time and the colour change is noted.

(1 mark)

(v)

Site Y is duodenum and pancreatic juice is found there.

(2 marks)

(vi)

An alkaline medium.

(1 mark)

(ii)

(vii) Enzyme P is denatured due to the acidic medium / by the low pH in the stomach.

(1 mark)

The acidity is caused by the presence of hydrochloric acid in the stomach.

(1 mark) __________ (14 marks)##

|!|EQA01200003|!| Elaine analyzed the data from two cities about the occurrence of tooth decay in children. She constructed a bar chart to show the percentage of children having tooth decay. City X had drinking water containing fluoride at a concentration of 2 ppm while city Y had no fluoride in the drinking water.

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ 50 City X

45

City Y

40

% children

35 30 25 20 15 10 5 0 0

1

2

3

4

5

6

7

8

9

10

11-19

Number of decayed teeth

(i)

For City X, calculate the total percentage of children with less than four decayed teeth. Show your working.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________

(ii)

(1) Draw a conclusion from the analysis.

(1 mark)

_______________________________________________________________________________ (2) Suggest a recommendation to the government of City Y.

(1 mark)

_______________________________________________________________________________

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (iii)

Young children enjoy drinking soft drinks and eating chocolates with a high sugar content. Describe how this habit is related to tooth decay.

(4 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (iv)

Name a mineral which is used for making teeth.

(1 mark)

_______________________________________________________________________________ ##

(i)

Total percentage of children with less than four decayed teeth = 6% + 13% + 12% + 50%(1 mark) = 81%

(ii)

(1 mark)

(1) Adding fluoride to the drinking water can prevent tooth decay.

(1 mark)

(2) The government of City Y should add fluoride to the drinking water to prevent tooth decay. (1 mark) (iii)

(iv)

The sugar in oral cavity is broken down to an acid by bacteria.

(2 marks)

The acid attacks the enamel of the teeth.

(1 mark)

The chance of having tooth decay increases.

(1 mark)

calcium

(1 mark) _________ (9 marks)##

|!|EQB01200004|!| *

The diagram below shows a liver and the associated blood vessels: K

liver O

N P

J L

M small intestine

Q

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (i)

What is structure L? Structure L stores a fluid which is important to digestion. State a function of this fluid.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

(ii)

Name vessels J, K, O and P.

(4 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (iii)

Which vessel contains blood with the highest concentration of glucose during starvation? Explain in relation to the hormone(s) involved.

(5 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (iv)

Suggest and explain whether N or P is an artery.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (v)

Two pathways are involved in blood circulation in this region. State their sequences.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (vi)

Which vessel contains blood with the highest concentration of carbon dioxide? Suggest another substance that is present at the highest concentration in blood carried by this vessel.

(2 marks)

_______________________________________________________________________________ ## (i)

L is the gall bladder.

(1 mark)

The bile salt present in the fluid emulsify fats into oil droplets for more efficient digestion of fats. / The sodium hydrogencarbonate provides an alkaline medium for the enzymes in the small intestine to work. (1 mark) (ii) (iii)

O is the hepatic artery; P is the hepatic portal vein;

(2 marks)

K is the hepatic vein; J is the posterior vena cava.

(2 marks)

K. During starvation, the blood glucose level is low.

(2 marks)

Less insulin is secreted from the pancreas

(1 mark)

so less glucose is oxidized by the liver cells/converted into glycogen for storage in the liver. (1 mark) ________________________________________________________________________________________ © Aristo Educational Press Ltd 2007 180

New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ Meanwhile, glycogen is converted back into glucose in the liver.

(1 mark)

Thus, K, a vessel coming out from the liver, contains blood with the highest concentration of glucose. (iv) (v)

N is an artery.

(1 mark)

The wall of N is thicker/ the lumen of N is narrower than that of K.

(1 mark)

N → O → K → J;

(1 mark)

N →Q →P →K →J

(1 mark)

(vi) J; urea

(2 marks) __________ (17 marks)##

|!|EQA01200005|!| Ann got four samples as listed below: A B C D

D

C

A small piece of grasshopper gut A drop of human saliva Half a germinating maize grain A small piece of rat colon

A

B Starch agar in petri dish

Ann put the samples on a starch agar as shown in the diagram. After 5 hours, she poured iodine solution onto the starch agar. Part of the agar showed positive results and brown zones were formed around three samples. Only one sample did not show a brown zone.

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (i)

Describe the positive results of iodine test.

(1 mark)

_______________________________________________________________________________

(ii)

What does the presence of a brown zone indicate?

(1 mark)

_______________________________________________________________________________ (iii)

Using the letters given, state the sample which did not showed a brown zone.

(1 mark)

_______________________________________________________________________________ (iv)

Explain the formation of brown zones around the three samples.

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (v)

State and explain the difference in the results if Ann had boiled the human saliva sample at the beginning of the experiment.

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ ## (i)

Iodine solution turns from brown to blue black in the presence of starch.

(1 mark)

(ii)

The brown zone indicates that there is no starch.

(1 mark)

(iii)

D

(1 mark)

(iv)

The three samples A, B and C have amylase which

(1 mark)

breaks down the starch in the agar to maltose.

(2 marks)

There would be no brown zone formed

(1 mark)

because amylase is denatured at high temperatures.

(2 marks)

(v)

_________ (9 marks)##

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ |!|EQA01200006|!| Tracy performed an experiment with a sample of an enzyme to find out its activity at different pH values. The following graph shows the results: enzyme activity

1

(i)

2

3

4

pH

State the optimal pH for the enzyme sample.

(1 mark)

_______________________________________________________________________________

(ii)

Name the enzyme.

(1 mark)

_______________________________________________________________________________ (iii)

Name the organ where the enzyme works in the human body.

(1 mark)

_______________________________________________________________________________ (iv)

Name the substrate of the enzyme.

(1 mark)

_______________________________________________________________________________

(v)

Describe how the pH of the juice in the organ named in (iii) is kept at the optimal value. (1 mark) _______________________________________________________________________________

(vi)

Write a word equation to show the enzymatic action.

(2 marks)

_______________________________________________________________________________

(vii) Would the enzyme work as it leaves the organ named in (iii) to the next part of the human gut? (2 marks) _______________________________________________________________________________ _______________________________________________________________________________ ## (i)

pH 2

(1 mark)

(ii)

protease

(1 mark)

(iii)

stomach

(1 mark)

(iv)

protein

(1 mark)

(v)

Gastric juice in the stomach is kept acidic due to the presence of hydrochloric acid. (1 mark)

(vi)

protease ________________________________________________________________________________________ © Aristo Educational Press Ltd 2007 183

New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________

protein

peptides

pH 2

(2 marks)

(vii) No, (1 mark) because the juice in the next part of the human gut is alkaline.

(1 mark) _________ (9 marks)##

|!|EQA01200007|!| Tom examined a figure which showed villi in the ileum:

(i)

Name the first organ to which blood flows from the ileum.

(1 mark)

_______________________________________________________________________________ (ii)

Name ONE substance that could be present at a lower concentration in the venous blood than in the arterial blood.

(1 mark)

_______________________________________________________________________________

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (iii)

State and explain ONE feature of A which increased the efficiency of food absorption.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________

(iv) (1) Name B.

(1 mark)

_______________________________________________________________________________ (2) Describe how B is involved in food absorption.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (v)

Describe the function of C.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ ## (i)

Liver.

(1 mark)

(ii)

Oxygen.

(1 mark)

(iii)

The epithelium is one-cell-thick

(1 mark)

to shorten the distance for diffusion of digested food

(1 mark)

(1) Lacteal.

(1 mark)

(iv)

(2) Fatty acids and glycerol enters the epithelial cells and recombine to form fat in the form of oil

(v)

droplets.

(1 mark)

The droplets then enter part B for transport.

(1 mark)

The muscles in C contract and relax alternatively

(1 mark)

in peristalsis to push the food along the ileum.

(1 mark) _________ (9 marks)##

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ |!|EQB01200008|!| STS Connections *

The diagram below shows the changes of pH in the mouth cavities of Leo and Nicole within a day:

Leo

pH of mouth cavity

Nicole

7

6

5 time breakfast

(i)

lunch

afternoon tea

dinner

(1) The pH value is restored to around 7 after the meal. How is the restoration brought about? (2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (2) A chewing gum advertisement claims that its product can help speed up the pH restoration after meals. Explain how chewing gum can do so.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

(ii)

(1) Describe how the pH changes in the mouth cavity of Nicole differ from those of Leo. (2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (2) Explain the difference in (1).

(1 mark)

_______________________________________________________________________________ _______________________________________________________________________________ (iii)

Describe the occurrence of tooth decay.

(4 marks)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

(iv)

Who has a higher chance of getting tooth decay? Why?

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

(v)

Nicole says, ‘Drink fluoridated water helps reduce the rate of tooth decay since fluoridated water neutralizes the acidity in the mouth cavity.’ Comment on her statement.

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ ##

(i)

(1) Saliva is alkaline and therefore it neutralizes the acidity in the mouth cavity.

(2 marks)

(2) Chewing gum stimulates salivary glands to secrete more saliva to neutralize the acidity. (2 marks)

(ii)

(1) The pH in the mouth cavity of Nicole shows more fluctuation. The pH falls not only at meal times, but also between meal times. (2) Nicole has snacks between meal times, while Leo does not. (iii)

The bacteria in the mouth cavity/ on the plaque

(2 marks) (1 mark) (1 mark)

break down sugars in the food debris

(1 mark)

into an acid.

(1 mark)

The acid dissolves the calcium salts in enamel

(1 mark)

and causes tooth decay. (iv)

(v)

Nicole.

(no mark if explanation is not given)

(1 mark)

The cumulative time of experiencing acidity in Nicole’s mouth cavity is longer.

(1 mark)

The pH in Nicole’s mouth cavity is lower.

(1 mark)

Her statement is wrong.

(1 mark)

(no mark if explanation is not given)

Drinking fluoridated water helps reduce the rate of tooth decay since fluoride ions combine with the enamel to form a more resistant layer

(1 mark)

to protect the enamel against attack of acids.

(1 mark) __________ (17 marks)##

|!|EQB01200009|!| ________________________________________________________________________________________ © Aristo Educational Press Ltd 2007 187

New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ *

The following diagram shows the percentage of digestion of different food substances along different regions of the alimentary canal of a man. The food substances are carbohydrate, protein and fat.

100 P Q R % of digestion

0 (i)

stomach

X

Y

Name the regions X and Y.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (ii)

Which food substances do P, Q and R represent, respectively?

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (iii)

Describe and explain curve Q.

(6 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (iv)

Name the secretion(s) present at X. State its/their source(s) and components involved in digestion. (6 marks) _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

(v)

Are the digestion products of R in the stomach and that in region Y the same? Explain your answer. (3 marks) _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

## (i) (ii)

X: duodenum

(1 mark)

Y: ileum

(1 mark)

P: fat

(1 mark)

Q: carbohydrate

(1 mark)

R: protein

(1 mark)

(iii) Some digestion of carbohydrate has taken place before food enters the stomach

(1 mark)

since digestion starts in the mouth cavity where salivary amylase digests starch to maltose.

(1

mark) The digestion of carbohydrate stops in the stomach

(1 mark)

since there is no carbohydrase./ the salivary amylase is inactivated.

(1 mark)

The digestion of carbohydrate resumes in the duodenum and the digestion continues in both duodenum and ileum, where carbohydrases are present to digest carbohydrate ultimately to monosaccharides such as glucose.

(1 mark)

The digestion reaches 100% /is completed within the ileum.

(1 mark)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (iv) Secretion pancreatic juice

Source pancreas

(1 mark)

Components amylase protease

(1/2 mark) lipase

(1/2 mark)

intestinal juice intestinal glands carbohydrases (1 mark) (1/2 mark) protease (1/2 mark) bile

(1 mark)

liver

(1/2 mark)

bile salts

(1/2 mark) (6 marks)

(v)

The products are not identical.

(no mark if explanation is not given)

(1 mark)

The products in the stomach are mainly peptides;

(1 mark)

while the products in region Y are mainly amino acids.

(1 mark) __________ (20 marks)##

|!|EQA01200010|!| Susan had lunch in a fast-food restaurant today. The table below shows the nutritional value of her meal: foodstuff fried chicken sausage and egg burger (i)

energy (kcal) 290 440

carbohydrate (g) 15 27

(1) Which food substance did Susan take in most in this meal?

fat (g) 17 28

protein (g) 18 19 (1 mark)

_______________________________________________________________________________ (2) Describe, in detail, how this food substance enters her bloodstream.

(9 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

(ii)

Susan’s daily protein requirement is 45g. She had obtained 11g from her breakfast. The total amount of protein she obtained from breakfast and lunch has already exceeded the amount required. Describe the fate of the excess protein in her body.

(6 marks)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ ##

(i)

(1) fat

(1 mark)

(2) The digestion of fats starts at the duodenum.

(1 mark)

Fat molecules are emulsified by bile salts in the bile to become oil droplets,

(1 mark)

which have a greater surface area for lipase to act on.

(1 mark)

The lipase in the pancreatic juice secreted by the pancreas

(1 mark)

digests fat molecules into fatty acids and glycerol.

(1 mark)

They are then absorbed by the epithelial cells of the villi

(1 mark)

and recombine to form fat molecules again in the cells

(1 mark)

The fat molecules diffuse into the lacteal.

(1 mark)

They are carried in lymph travelling along the lymph vessels.

(1 mark)

The lymph is finally drained into the bloodstream and the fat molecules follow.

(ii)

Amino acids from the excess protein cannot be stored in the body

(1 mark)

and therefore are broken down by deamination in the liver.

(1 mark)

The amino groups are removed from amino acids and turned into ammonia.

(1 mark)

The poisonous ammonia is converted to urea

(1 mark)

which is finally excreted in the urine by the kidneys.

(1 mark)

The remaining parts of amino acids are changed into carbohydrates or fats.

(1 mark) __________ (16 marks)##

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ |!|EQA01200011|!| The following diagram shows two similar models of a region of the mammalian alimentary canal. The water in the test tubes surrounding the dialysis tubings was tested with standard food test reagents at the beginning of the experiment and again after one hour. The results showed that neither starch nor reducing sugar was present in the water surrounding tube A and B at the beginning of the experiment. test tubes

water bath at 37℃ A

B

starch + amylase + water

starch + water

dialysis tubing (i)

What results would be expected after one hour when water surrounding the dialysis tubing was tested for starch and reducing sugar?

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (ii)

Name a suitable chemical for testing reducing sugar.

(1 mark)

_______________________________________________________________________________ (iii)

What structure in the human body does the liquid surrounding the dialysis tubing represent? (1 mark) _______________________________________________________________________________

(iv)

If the experiment were repeated, with the two test tubes placed in a refrigerator instead of a water bath, how would you expect the results to differ? Explain your answer.

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ ## (i)

Only reducing sugars could be found in the water surrounding dialysis tubing A.

(1 mark)

No starch could be found in either test tube.

(1 mark)

(ii)

Benedict's solution.

(1 mark)

(iii)

Bloodstream

(1 mark)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (iv)

Reducing sugars would be absent in the water surrounding dialysis tubing A. Since amylase was inactive at low temperatures, it failed to digest starch into reducing sugars.

(3 marks) _________ (7 marks)##

|!|EQB01200012|!| *

The following diagram shows a certain region of the human digestive system:

(i)

Name structures A, B, C and D.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (ii)

Name the fluid secreted by glands in the stomach wall.

(1 mark)

_______________________________________________________________________________ (iii)

Name THREE substances in the secretion mentioned in (ii).

(11/2marks)

_______________________________________________________________________________ (iv)

(1) Name the exocrine and endocrine secretions of structure C.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (2) By what means do these secretions reach the places where they exert their actions? (2 marks) _______________________________________________________________________________ _______________________________________________________________________________ (3) Name the enzymes present in the exocrine secretion of structure C.

(11/2marks)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (4) What are the functions of these enzymes?

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (v)

(1) Name the secretion of the liver that assists in digestion.

(1 mark)

_______________________________________________________________________________ (2) Where is this secretion stored before entering structure B?

(1 mark)

_______________________________________________________________________________ (3) State the functions of this secretion.

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (vi)

(1) Name the secretion of structure B.

(1 mark)

_______________________________________________________________________________ (2) What are the functions of this secretion?

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (3) What are the end products of digestion in B?

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ ## (i)

A - bile duct B - duodenum C – pancreas D - pancreatic duct

(ii) (iii) (iv) (1)

(1/2 mark each)

(2 marks)

gastric juice hydrochloric acid, proteases and mucus

(1 mark) (1/2 mark each)

Exocrine secretion – pancreatic juice Endocrine secretion – insulin/ glucagon

(2) Exocrine secretion – via the pancreatic duct to the duodenum Endocrine secretion – via the bloodstream to all parts of the body

(11/2marks) (1 mark) (1 mark) (1 mark) (1 mark)

(3) amylase, lipase and protease (1/2 mark each)

(11/2 marks)

(4) Amylase digests starch to maltose.

(1 mark)

Lipase digests fats to glycerol and fatty acids.

(1 mark)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ Protease digests protein to peptides/ digests peptides to amino acids. (v)

(1 mark)

(1) bile

(1 mark)

(2) gall bladder

(1 mark)

(3) - to neutralize the acidic medium,

(1 mark)

- to activate the pancreatic and intestinal enzymes and

(1 mark)

- to lower the surface tension of / emulsify fats so that fats are broken down into small droplets more easily. (vi)

(1 mark)

(1) intestinal juice

(1 mark)

(2) Carbohydrase digests disaccharides into monosaccharides.

(1 mark)

Protease digests peptides into amino acids. (3) glucose and other monosaccharides amino acids

(1 mark) (1 mark) (1 mark) __________ (23 marks)##

|!|EQB01200013|!| *

The following diagram shows the structure of the posterior region of the human gut:

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (i)

Name parts A, B, C, D, E and F.

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (ii)

Explain the differences in structure and function between structure B of a human and that of a rabbit? (4 marks) _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

(iii)

Name the substance in our diet that assists in the passage of food along the large intestine. (1 mark) _______________________________________________________________________________

(iv)

State the function of (1) D.

(1 mark)

__________________________________________________________________ (2) E.

(1 mark)

_______________________________________________________________________________ ## (i)

A - ileum/ small intestine B - caecum C - appendix D - colon E – rectum F - anus

(1/2 mark each)

(3 marks)

(ii) Difference Explanation longer/ larger/ better developed in a rabbit can store more cellulose for digestion bacteria present to secrete cellulase to digest cellulose (vice versa)

(iii) roughage/ dietary fibres (iv) (1) to absorb water (2) temporarily store faeces/ egestion

(4 marks) (1 mark) (1 mark) (1 mark) __________ (10 marks)##

|!|EQA01200014|!| The diagram below shows the anterior region of the alimentary canal of a man: ________________________________________________________________________________________ © Aristo Educational Press Ltd 2007 196

New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________

(i)

(1) What is the name of the fluid produced by A?

(1 mark)

_______________________________________________________________________________ (2) Name the enzyme found in the above fluid and describes its function.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (3) Can we call A an endocrine gland? Explain your answer.

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (ii)

Give TWO functions of structure B.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (iii)

(1) Name structure D.

(1 mark)

_______________________________________________________________________________ (2) State the function of D.

(1 mark)

_______________________________________________________________________________ _______________________________________________________________________________ (iv)

Where do structures E and F lead to, respectively?

(2 marks)

_______________________________________________________________________________ (v)

Name the process by which food is passed along the intestine.

(1 mark)

_______________________________________________________________________________ ## (i)

(1) saliva

(1 mark)

(2) Salivary amylase digests starch to maltose.

(2 marks)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (3) No. Its product is not a hormone and it is discharged via a duct to the mouth cavity. (ii)

(1 mark) (2 marks)

It contains taste buds to detect taste.

(1 mark)

It mixes the saliva with food to form a bolus to facilitate swallowing.

(1 mark)

(1) epiglottis

(1 mark)

(2) It prevents the food from entering the trachea during swallowing.

(1 mark)

(iv)

E leads to the lungs and F leads to the stomach.

(2 mark)

(v)

peristalsis

(1 mark)

(iii)

__________ (13 marks)## |!|EQA01200015|!| The diagram below shows the structure of the wall of the mammalian small intestine:

(i)

Name A, B and C.

(11/2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (ii)

(1) What is the function of structure C?

(1 mark)

_______________________________________________________________________________ (2) State and explain how structure C is adapted to perform its functions.

(4 marks)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (iii)

What is the function of A?

(1 mark)

_______________________________________________________________________________ (iv)

(1) What is the function of B?

(1 mark)

_______________________________________________________________________________ (2) State the transport system to which B belongs.

(1 mark)

_______________________________________________________________________________ (v)

List the structures (in correct order) by which food absorbed by A is transported to the kidney. (5 marks) _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

(vi)

D and E are circular and longitudinal muscles, respectively. What is their function?

(1 mark)

_______________________________________________________________________________ _______________________________________________________________________________ ## (i)

A - blood capillaries B - lacteal C – villus (1/2 mark each)

(11/2 marks)

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (ii)

(1) absorption of food

(1 mark)

(2) Adaptation

Explanation

with thin-walled epithelium folded/ with microvilli

to facilitate diffusion to increase the surface area

with lacteals/ capillaries

to transport the absorbed products (any two pairs)

(4 marks)

(iii)

to transport or absorb glucose and amino acids

(1 mark)

(iv)

(1) to transport or absorb oil droplets

(1 mark)

(2) lymphatic system

(1 mark)

(v) (vi)

hepatic portal vein → liver → hepatic vein → heart → pulmonary artery→ lung → pulmonary vein → heart → dorsal aorta → renal artery→ kidney (1/2 mark each)

(5 marks)

Their alternate contraction and relaxation bring about peristalsis.

(1 mark) ___________ (151/2marks)##

|!|EQA01200016|!| The following diagram shows the arrangement of teeth in the upper jaw of a man:

(i)

Which teeth are the canines and premolars in the diagram?

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (ii)

Suppose the arrangement of the teeth in the lower jaw is the same, write down the dental formula of this person.

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (iii)

Which chemical is added to our drinking water to reduce the incidence of tooth decay?

(1 mark)

_______________________________________________________________________________

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (iv)

Explain why food lodged in the crevices between the teeth may lead to tooth decay.

(3 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (v)

Draw a well-labelled diagram to show a vertical section of tooth H.

(6 marks)

canines - E and J

(1 mark)

## (i)

premolars - C, D, K and L

(2 marks)

(ii)

i /2 c /1 pm /2 m /2

(2 marks)

(iii)

fluoride

(1 mark)

(iv)

Bacteria act on food lodged in the crevices between the teeth and break it down into acids which then

2

1

2

2

attack the teeth.

(3 marks)

(v) enamel crown dentine neck nerve

gum pulp cavity

root

cement

blood vessel

tooth canal jaw bone Vertical section of tooth H Diagram

(2 marks)

Label (1/2 x 7 any seven)

(31/2 marks)

Title

(1/2 mark)

__________ (15 marks)## |!|EQA01200017|!| ________________________________________________________________________________________ © Aristo Educational Press Ltd 2007 201

New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ When fats are digested, they will be broken down into simpler molecules which are acids. The following experiment aimed to investigate the action of lipase on fats. Milk was used as the source of fats, and four test tubes were set up as follows:

4 cm3 milk + 1 cm3 lipase

4 cm3 milk + 1 cm3 boiled lipase

4 cm3 milk + 1 cm3 lipase

4 cm3 milk + 1 cm3 water

+ 1 cm3 water

+ 1 cm3 water

+ 1 cm3 water

+ 1 cm3 sodium

+ 1 cm3 sodium

hydrogencarbonate

hydrogencarbonate

solution

solution

The test tubes were kept in a water trough for 1 hour at a constant temperature, and then the content of each tube was tested to find out if acids had been formed. The results are shown in the following table:

(i)

Test tube

A

B

C

D

Final acidity/basicity

Slightly acidic

neutral

acidic

alkaline

At what temperature was the water trough maintained?

(1 mark)

_______________________________________________________________________________ (ii)

Why was sodium hydrogencarbonate solution added to some of the test tubes?

(1 mark)

_______________________________________________________________________________ _______________________________________________________________________________ (iii)

In which test tube had the breakdown of fat occurred?

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ (iv)

Draw a conclusion of this experiment.

(1 mark)

_______________________________________________________________________________ _______________________________________________________________________________

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New Biology – a modern approach 2 Chapter 12: The human digestive system ________________________________________________________________________________________ (v)

Which test tube(s) served as control(s)?

(2 marks)

_______________________________________________________________________________ (vi)

(1) Where is lipase secreted in the human body? Where does it carry out its function?

(2 marks)

_______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ (2) Do you think that a gland which secretes lipase is an endocrine gland? Explain your answer. (2 marks) _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ ## (i)

optimum temperature for the enzyme

(1 mark)

(ii)

to provide an alkaline conditional / higher pH

(1 mark)

(iii)

A and C

(2 marks)

(iv)

Lipase is active in alkaline condition.

(1 mark)

(v)

B and D

(2 marks)

(vi)

(1) Lipase is secreted by the pancreas.

(1 mark)

It carries out its function in the duodenum.

(1 mark)

(2) It is not an endocrine gland since its secretion is carried away by the pancreatic duct to duodenum/ not carried by bloodstream.

(2 marks) __________ (11 marks)##

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