Answer Key-Digestion.docx

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Answer Key - Digestion

Section A: Multiple Choice Questions

1. D

Explanation: Taste buds contain the receptors for taste as the tongue is the organ for taste.

Taste buds on the tongue allow for us to taste foods that are salty, sweet, bitter or sour.

However taste buds do not in any way, help in the digestion process.

2. C

Explanation: The epiglottis is a flap-like piece of tissue that covers the trachea to prevent

food fro going down the trachea. The trachea is a tube that contains the laryn! or voice bo!

and the glottis. The glottis is sall opening that leads to the laryn!. During swallowing, the

epiglottis oves downwards to cover the glottis so that no food would enter the trachea.

". D

Explanation: The trachea or windpipe is an organ that is part of the respiratory syste. The

trachea branches out for for the bronchi. #n organ is a collection of tissues $oined together

to carry out a function.

%. &

Explanation: &ile salts are contains no en'yes. (nstead these salts physically break down

or eulsify large fat droplets into saller fat droplets so as to increase action of lipase onfats.

). &

Explanation: &ile is produced by the liver via the liver cells. However bile is teporarily

stored in the gall bladder. During digestion, bile flows into the duodenu through the bile

duct.

*. C

Explanation: +ipase fro pancreatic $uices and lipase produced by epithelial cells aids incheically breaking down saller fat olecules that had previously been acted upon by bile

salts to for fatty acids and glycerol.

. #

Explanation: # violet coloured &iurets solution is indicative of proteins. # brick red

precipitate for &enedicts test shows a large aount of reducing sugars present. /hen an

ethanol eulsion test produces a cloudy white solution eans fats are present. 0range $uice

contains virtually no fat and protein. alon does not contain any carbohydrates. Coconut oil

does not contain carbohydrates and proteins, instead it has high aounts of unsaturated fats.

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4gg whites are known to contain the highest aount of proteins and have virtually no fats

and carbohydrates.

5. C

Explanation: Digestion begins in the outh, passes via the oesophagus to enter the stoach,then sall intestine. Digestion ends in the sall intestine. The large intestine absorbs water

and ineral salts fro the undigested food aterials. 6ndigested and unabsorbed atter is

stored teporarily as faeces before the faeces is e!creted via the anus.

7. C

Explanation: Digestion begins in #, the outh and ends at C, the sall intestine.

18. #

Explanation: eristalsis enables food to be i!ed with digestive $uices and also pushes or propels the food along the alientary canal.

11. C

Explanation: The sall intestine begins with the 6-shaped duodenu $ust below the

pancreas, followed by the $e$unu and lastly the ileu that connects the sall intestine to the

caecu of the large intestine.

12. D

Explanation: 9ost of the food ites shown are e!aples of unbalanced diets and are ostly

processed foods that are lacking in vitains but high in sugars and fats.

1". D

Explanation: aller particles of the potato wedges allows for increased surface area for

salivary aylase to act on the identical )8 g portions of potato wedges.

1%. &

Explanation: :rilled fish contains no carbohydrates, let alone starch. tarch are found in

foods derived fro plant sources. tarch can be detected through the iodine test. # few drops

of iodine solution when added to any substance containing starch will produce a blue-black

colour. (n absence of starch, the iodine solution would reain yellow.

1). D

Explanation: alivary aylase is produced by the salivary glands. +ipase is produced by the

pancreas and epithelial cells of the sall intestine. ancreatic aylase as the nae suggests,

is produced by the pancreas. &ile salts are not en'yes, however they are produced by the

liver.

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1*. C

Explanation: The optiu teperature of pepsin is between "8°C to "°C, in an acidic

ediu. #t teperatures below "8°C, the en'ye would be inactivated. #t teperaturesabove "°C, the pepsin would be denatured.

1. &

Explanation: eptidases would act on the polypeptides present in cheese to convert the

into aino acids. /hereas pepsin acts on proteins to convert the into polypeptides. Cheese

does not contain starch so the actions of salivary aylase and pancreatic aylase are

unnecessary.

15. #

Explanation: 0ption # is the colon. 0ne of the ain functions of the colon is to absorb

water. & is the $e$unu. C is the rectu and D is the appendi!.

17. D

Explanation: epsin works best at very low pH, typically between pH values of 1.)-2.

28. #

Explanation: arts , ; and T produce digestive en'yes which are the outh, stoach and

sall intestine respectively. art < is the oesophagus while art is the large intestine and no

digestion occurs in these two parts.

Section B: Short Answer Questions

1. 4nsure spelling of words are correct before full arks can be awarded.

a. Digestion, #bsorption

b. &olus

c. Taste buds

d. 9altose

e. eristalsis

f. #ylase

g. 0esophagus

h. Hydrochloric #cid

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i. Chye

$. roteases

k. +ipase

2ai. #, D, 4 and =.

2aii. They are the salivary glands, stoach, pancreas and sall intestine.

2aiii. #ccept any of the following answers>

art # ?alivary glands@ A alivary aylase

art D ?toach@ A epsin, ;ennin, gastric lipase

art 4 ?ancreas@ A Trypsin, #ylase, +ipase

art = ?all (ntestine@ A ucrase, +actase, 9altase, +ipase, eptidases

2bi. art : is the colon.

2bii. (ts function is to absorb water and ineral salts fro undigested food aterials.

2ci. art C.

2cii. #ccept any of the following answers>

- &ile participates in the physical breakdown of fats hence no new products are adethus it cannot be considered an en'ye. #n en'yatic reaction usually leads to

foration of new products.

- &ile is not a protein however en'yes are.

"a.

A tarch

B eptidase ?epsin not accepted@

C +ipase

P 9altose ?Disaccharide not accepted@

Q #ino #cidsR :lycerol

S =atty #cids

"b. The huan body cannot absorb large food olecules. The purpose of digestion is to break

down these large food olecules through en'yatic action to for saller food olecules

which can be absorbed by our bloodstrea and sent to cells that reBuire these substances.

%ai. illi, epithelial cells of a villus and lacteal ?or lyphatic capillary@ respectively. illus

not accepted as it is singular for@

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%aii. The villi are finger-like pro$ections that help to increase the surface area of the sall

intestine for absorption.

%bi. The sall intestine.

%bii. The lyphatic capillary or lacteal of the villi transport fats away fro the intestine.

%c. 9icrovilli

)a. The test to be done is &iuret test. The biuret test solution is a blue solution ade up of

sodiu hydro!ide and copper ?((@ sulphate. The procedure to carry out the test is as follows>

?1@ #dd the food saple to 2 c" ?any volue between 2 to 18c" is acceptable@ of biuret test

solution and shake it thoroughly.

?2@ hake well and allow the i!ture to stand for ) inutes.

?"@ 0bserve if any colour changes occur.

)b. The biuret solution would change fro blue to violet within ) inutes.

)c. alon, egg white, chicken, any other proteinaceous foods.

*ai. (odine test.

*aii. tarch can be detected using the iodine test. (f starch is present in a food, it will turn the

iodine fro yellow to a blue-black colour. tarch can only be produced by plants, hence the

presence of starch is a good indicator that the food aybe suitable for vegetarians.

*bi.

Tests

Food

Sustan!es

&iurets Test (odine Test &enedicts Test 4thanol

4ulsion Test

+ipid X X X

rotein X X X

tarch X X X

;educing

ugars

X X X

Eon-;educing

ugars

X X X X

*bii@

tarch is not a reducing sugar however altose is. Hence Fohn can obtain eBual aounts of a

purely starchy food like rice ?any siilar food options like tapioca starch powder are

acceptable@. =or one portion of rice, he can chew it and spit it out to allow salivary aylase to

act on it. The other portion of rice reains undisturbed. He will then carry out &enedicts test

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to these rice saples. 0nly the chewed saple will show a change in colour of the &enedicts

test fro blue to for a brick-red precipitate. &enedicts test can only act upon reducing

sugars whilst salivary aylase acts upon starch to convert it to altose.

ection C> =ree ;esponse


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action of sucrose to for glucose and fructose. +actose is broken down by lactase to for

glucose and galactose. /hile altose is broken down by altase to for 2 olecules of

glucose.

1cii. The pharyn! branches out into two tubes known as the laryn! and the oesophagus.

=urther down the laryn! is the trachea or windpipe that enables us to take in o!ygen into our lungs. The oesophagus transports food into the stoach. # piece of flap-like tissue called the

epiglottis is found $ust after the pharyn! and usually prevents food fro entering the laryn!

and obstructing the trachea. Hence the epiglottis is essential in preventing choking when we

swallow.

2a. There are % incisors in each $aw. ince we have 2 $aws, there would be a total of 5

incisors. Therefore, with siple ath, ) of 5 incisors would be 8.) ! 5 I * incisors lost.

2b. ince incisors are used for tearing off and cutting pieces of food during ingestion, Thoas

will need to cut his foods into bite-si'ed pieces or even saller before ingesting the until

the broken incisors are replaced.

2c. Thoas can consue protein shakes to ensure he has optiu protein needed for growth

and aintenance of bodily functions. This is because he is unable to consue eat and fish

which are a$or sources of proteins. He could also consue health suppleents in capsule

for to ensure he has all the reBuired vitains and inerals that he ay have issed out

since he is unable to consue food that reBuires alot of chewing.

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Answer Key-Digestion.docx