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Biology S3 > Ch.12.3 > Flashcards

Ch.12.3 Flashcards

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1
Q

Name the 5 processes of nutrition in our body.

A

Ingestion, digestion, absorption, assimilation, egestion

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2
Q

Describe ingestion. Where does it occur?

A

Food is taken in through the mouth. It only occurs in the mouth cavity.

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3
Q

Describe digestion.

A

Food is broken down into soluble and simple molecules.

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4
Q

Describe absorption.

A

The digested, soluble and simple food molecules enter the circulatory system from the alimentary canal.

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5
Q

Describe assimilation.

A

The absorbed food molecules are taken up by all cells for metabolism / for energy, growth and maintaining health.

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6
Q

Describe egestion.

A

The undigested materials are removed from the alimentary canal.

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7
Q

Egestion is not to be mistaken with excretion. What does excretion refer to?

A

The removal of metabolic waste.

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8
Q

The digestive system is where ______________________________________, including the ____________________________ of food.

A

food is processed in our body, digestion and absorption

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9
Q

The digestive system consists of many ___________ working together in a ____________________ way. It consists of the _______________________________ and some _______________________________. As food passes through it, the various food substances are _______________________ in __________________________.

A

organs, coordinated, alimentary canal, digestive glands; gradually digested, different parts of the system

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10
Q

What is the the alimentary canal? What is its use?

A

It is a long tube and consists of many parts for food processing. Food is digested as it travels through the alimentary canal.

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11
Q

What is the function of digestive glands?

A

They secrete digestive juice for digestion.

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12
Q

Name the three digestive glands found in the digestive system.

A

Salivary glands, liver, pancreas.

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13
Q

Name the organs found in the alimentary canal in the order that food travels through.

A

Mouth cavity (tongue, teeth), oesophagus, stomach, small intestine, large intestine, anus

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14
Q

Name the organ that is found in the digestive system but is neither a digestive gland nor part of the alimentary canal.

A

The gall bladder.

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15
Q

What is the purpose of digestion?

A

The food taken in by mammals is too large to pass through the wall of the alimentary canal, which is differentially permeable, into blood capillaries. Digestion makes the food soluble and simple for absorption.l

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16
Q

What do we mean when we say that the wall of the alimentary canal is differentially permeable?

A

This means that it allows some substances to pass through it, eg small and simple food substances, vitamins, waters and minerals, while blocking others, eg large and complex food substances such as polysaccharides, disaccharides.

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17
Q

Food in the alimentary canal is ______________________________________________________ by physical digestion. Then the ______________________________________________________ by chemical digestion.

A

broken down into smaller pieces without changing its chemical structure, complex food substances are broken down into simple food substances by chemical reactions

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18
Q

Physical digestion in our bodies is mainly brought about by:
1.
2.
3.

A
  1. Chewing by the teeth in the mouth cavity
  2. Churning in the stomach
  3. Peristalsis along the alimentary canal
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19
Q

What is the purpose of physical digestion?

A

Physical digestion increases the surface area of food, hence allowing more surfaces to react with digestive enzymes later on and increasing the rate of chemical digestion.

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20
Q

Chemical digestion involves _________________________ in the food molecules. The reactions are catalysed by ___________________________ which are ____________________________________.

A

chemical changes, digestive enzymes, present in the digestive juices

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21
Q

Chemical digestion takes place in ___________________________________________.

A

the mouth cavity, stomach and small intestine

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22
Q

Where does all digestion end? What is carried out in the digestive system from then on?

A

The small intestine. Absorption and egestion.

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23
Q

Enzymes are __________________ that can _________________________, ie __________________________________________________________________________________________. What does this mean?

A

biological catalysts, catalyse reactions, increasing the rate of reactions without themselves being changed or used up in the reactions. This means that they can bind to more substrates and be reused.

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24
Q

Name two indicators of higher rate of reaction.

A

More products formed

Reactants used up more quickly

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25
Q

Enzymes are specific in _____________. Why?

A

actions; this is because the different specific shapes of enzymes allows them to only be able to bind with a certain type of substrate.

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26
Q

What is the general word equation of a hydrolysis process?

A

substrate + water —enzyme—> product

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27
Q

Define a substrate.

A

It is a reactant that is being observed in a chemical reaction.

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28
Q

Why are enzymes shown on top of the arrow of a word equation of an enzymatic reaction?

A

This is because they aren’t created nor used up.

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29
Q

The __________________ of an enzyme binds to the __________________ in an enzymatic reaction. This complex formed is called the _______________________________. What is the use of forming this complex in the case of a hydrolysis process?

A

active site, substrate; enzyme-substrate complex;
The formation of this bond, especially a complete one, increases the surface area of the substrate that the enzyme can work on, which increases the rate of reaction and hence facilitates the breaking down of the bond within the substrate.

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30
Q

Name the three main types of digestive enzymes.

A

Carbohydrases, proteases, lipases.

31
Q

What is the function of carbohydrases? Name two examples of carbohydrases, the enzymatic reactions that they catalyse and the corresponding word equations respectively.

A

Carbohydrases catalyse the breaking down of complex carbohydrates into simpler ones.
Amylase catalyses the hydrolysis of starch; starch + water —amylase—> maltose
Maltase catalyses the hydrolysis of maltose; maltose + water —maltase—> glucose

32
Q

How do we know that cellulase cannot be found in the human body?

A

This is because cellulose is an important source of dietary fibre in our bodies, and we cannot digest nor absorb dietary fibre.

33
Q

What is the function of proteases?

A

Proteases catalyse the breaking down of proteins into peptides and peptides into amino acids.

34
Q

What is the function of lipases?

A

Lipases catalyse the breaking down of fats into fatty acids and glycerol.

35
Q

Name the activities involving digestion found in the mouth cavity.

A

Food is chewed into small pieces by teeth and mixed with saliva. The digested food is then shaped into a bonus and swallowed.

36
Q

What is a bolus?

A

It is a shape that can be swallowed easily.

37
Q

What is the digestive juice found in the mouth cavity? Which organ is it secreted by?

A

Saliva. It is secreted by the salivary glands.

38
Q

The pH of saliva is about _____, ie ____________________. Why?

A
  1. 5, slightly alkaline
  2. Amylase, the enzyme found in saliva, functions in slightly alkaline conditions
  3. To neutralise harmful acids produced by the action of bacteria in our mouth cavity to protect our teeth.
39
Q

Different enzymes have a ____________ range of ____________ ________, ie they work better in different ____ environments, eg ____________, ____________. Why?

A

narrow, optimal pH, pH, neutral, acidic
This is because enzymes are proteins, which are sensitive to pH. This means that they may lose structure and functions in unsuitable pH.

40
Q

What does saliva consist of? Name the respective functions of these components.

A

Salivary amylase — catalyses the breaking down of starch into maltose (polysaccharide —> disaccharide); called SALIVARY amylase because amylase can also be found in other digestive juices
Mucus — moistens and lubricates the food for easy chewing and swallowing
Water — dissolves soluble materials in the food

41
Q

Name the activities involving digestion found in the oesophagus.

A

Food is pushed down to the stomach through peristalsis of the oesophagus, which also breaks food down into smaller pieces.

42
Q

Name the activities involving digestion found in the stomach.

A

Food is churned, mixed with gastric juice, and digested into a semi-solid paste called chyme.

43
Q

How is food churned in the stomach? Why is churning forms of both physical and chemical digestion?

A

Through the contraction and relaxation of the muscles of the stomach wall.
This is because it mixes gastric juice with food inside the stomach AND breaks food down into smaller pieces at the same time.

44
Q

What is the digestive juice found in the stomach? What is it secreted by? Name and describe the pH of this digestive juice.

A

Gastric juice. It is secreted by the gastric glands that are present in the stomach wall. 2.0, which is highly acidic.

45
Q

What does gastric juice contain? Name the respective functions of these components.

A

Pepsin — a protease that catalyses the breaking down of proteins into peptides (peptides are not yet broken down into amino acids here, happens in small intestines)
Hydrochloric acid — provides a highly acidic medium for the enzymes to work properly, kills most bacteria in the food to prevent pathogens from harming our body
Mucus — protects the stomach against proteases and hydrochloric acid

46
Q

Name the activities involving mechanical digestion found in the small intestine.

A

Food is mechanically digested by the action of bile and peristalsis.

47
Q

Name the activities involving chemical digestion found in the small intestine.

A

Food is chemically digested by the enzymes in pancreatic juice and intestinal juice; peristalsis also helps mix the food with digestive juices.

48
Q

Name an activity not involving digestion found in the small intestine.

A

Peristalsis, which pushes food along the small intestine.

49
Q

________________________________________________________ is completed in the small intestine. Food is now __________________________________________.

A

Digestion of all carbohydrates, lipids and proteins; broken down into small and simple substances

50
Q

Name the three digestive juices found in the small intestine, and the things that they are produced and stored in / secreted by.

A

Bile — produced in liver, stored in gall bladder
Pancreatic juice — secreted by pancreas
Intestinal juice — secreted by the glands in the walls of the small intestine

51
Q

What does bile contain? Describe and name the respective functions of these components.

A

Bile salt — emulsification: emulsifies lipids into small droplets to facilitate the chemical digestion of lipids; no chemical change of lipids occurs
Sodium hydrogencarbonate — an alkali with a pH slightly > 7 (8.3); neutralises the acidic chyme, provides an alkaline medium for the action of enzymes in the small intestine

52
Q

Why is chyme highly acidic?

A

This is because it is mixed with gastric juice.

53
Q

What is the use of emulsification?

A

With emulsification, smaller lipid droplets are created, increasing the surface area of lipids for enzymes to work on and hence the rate of chemical digestion of lipids catalysed by enzymes.

54
Q

Describe the pH of pancreatic juice and intestinal juice. What do we know from this?

A

They are both slightly alkaline. From this, we know that enzymes found in these juices show high activity in slightly alkaline environments.

54
Q

What does pancreatic juice contain? Describe and name the respective functions of these components.

A

Pancreatic amylase — catalyses the breakdown of the remaining starch into maltose
Proteases — catalyses the breakdown of some proteins into peptides, and some peptides into amino acids
Pancreatic lipase — catalyses the breakdown of the emulsified lipids into fatty acids and glycerol
Sodium hydrogencarbonate — neutralises acidic chyme, provides an alkaline medium for the action of the enzymes in the small intestine

55
Q

Where does the chemical digestion of lipids start and end?

A

The small intestine.

56
Q

What does intestinal juice contain? Name the respective functions of some of these components.

A

It contains water, mucus, enzymes and sodium hydrogencarbonate.
Carbohydrases — catalyses the breakdown of the disaccharides into monosaccharides; including lactase, maltase, sucrase
Proteases — catalyses the breakdown of some peptides into amino acids
Sodium hydrogencarbonate — neutralises the acidic chyme, provides an alkaline medium for the action of enzymes in the small intestine

57
Q

Where does absorption take place?

A

In the small intestine, large intestine and stomach.

58
Q

Which substances can pass through the wall of the intestine and enter the blood?

A

Water, vitamins, minerals, small and simple food substances.

59
Q

After digestion along the __________________________, food is fully digested into _____________________________________. These substances and ______________________ can then pass through ___________________________________________ and __________________________. The absorbed food substances are then _________________________________________________________________, and these substances are _________________________.

A

alimentary canal; small, simple and soluble molecules; most of the water; the wall of the small intestine; enter the blood capillaries; carried to all parts of the body via the transport system; used by body cells

60
Q

Absorption takes place mostly in the __________________________. _________ of the water in food is absorbed here.

A

small intestine, > 90%

61
Q

Name and explain two adaptations of the small intestine for absorption.

A

Very long — around 7 metres; provides sufficient time for absorption and digestion, as food takes about 5 to 12 hours to travel down the small intestine to the colon.
Highly-folded inner wall (which is the wall that is facing the lumen) — provides a large surface area for absorption, which increases the rate of absorption of molecules (large surface area also caused by villi found on the walls of the intestine)

62
Q

Small amount of __________________________ takes place in the __________________________ and stomach.

A

water absorption, large intestine

63
Q

Describe the processes of absorption and egestion in the large intestine.

A

After the undigested food (eg dietary fibre) enters the large intestine, it absorbs minerals and most of the remaining water, leaving a semi-solid waste called faeces. This substance is temporarily stored in the large intestine, until they are passed out of the boy through the anus.

64
Q

What is faeces made up of?

A

Undigested and unabsorbed substances.

65
Q

The human transport system consists of the ______________________________ and the ______________________________. The former contains _________________________________________________, while the latter contains _________________.

A

circulatory system, lymphatic system; blood, blood vessels, heart, lymph

66
Q

Water soluble substances (eg ___________________, _______________________, ____________________________, ________________) are ______________________________________________ and ______________________________________________.

A

monosaccharides, amino acids, water-soluble vitamins, minerals, directly absorbed into blood, transported via the circulatory system

67
Q

________________, which are not water soluble, (eg __________________, __________________ and _________________) are absorbed into ___________, enter the _______________________ and are __________________________________________, which later __________________________________________, and these substances would _______________________.

A

Lipids, fatty acids, glycerol, lipid-soluble vitamins, lymph, lymphatic capillaries, transported via the lymphatic system, joins the circulatory system near the heart, enter the blood streaming

68
Q

The digestive system is _______________________ to the transport system. What does this allow?

A

closely connected; it allows the digested substances to be absorbed quickly and carried to all parts of the body.

69
Q

Describe the procedure for studying the chemical digestion of starch by enzymes.

A
  1. Add 2 cm³ of starch solution to each of two test tubes. Label them A and B.
  2. Add 2 cm³ of distilled water and amylase solution to test tube A and B respectively and mix the respective test tubes gently. (mix: shake side to side gently / tap bottom of the test tube)
  3. Put the test tube in a beaker of warm water at 37°C for 15 minutes.
  4. Add two drops of iodine solution to each test tube and mix gently. Observe any colour change in the iodine solution.
    —When iodine solution is added to test tube A, its colour changes to blue-black. This shows that starch is present.
    —When iodine solution is added to test tube B, its colour doesn’t change/ remains brown in colour. This shows that starch is not present.
70
Q

Name the safety precaution for studying the chemical digestion of starch by enzymes.

A

Iodine is harmful, avoid contact with skin.

71
Q

What is the purpose of setting up test tube A (test tube containing starch solution and distilled water) in the experiment of studying the chemical digestion of starch by enzymes?

A

It acts as a control set-up to ensure that the presence of starch is affected only by the respective liquids added to the starch solution and not any other variable in the experiment.

72
Q

Is there any difference between the observations in test tubes A and B in the experiment of studying the chemical digestion of starch by enzymes? If so, explain what causes this difference.

A

Yes. The action of amylase in test tube B breaks down the starch present in it; therefore when iodine solution is added to it, it doesn’t detect any presence of starch and remains brown in colour. Conversely, the lack of the action of amylase in test tube A means that starch is still present and the iodine solution will change to blue-black in colour.

73
Q

Read the following reminders for the question type: describing chemical digestion.

A
  • template
    • ENZYME [ in the DIGESTIVE JUICE produced by the DIGESTIVE GLAND ] catalyses the hydrolysis of SUBSTRATE into PRODUCT [ in the ORGAN OF ALIMENTARY CANAL ]
  • examples
    • AMYLASE in the SALIVA produced by the SALIVARY GLANDS catalyses the hydrolysis of STARCH into MALTOSE in the MOUTH CAVITY
    • PEPSIN in the GASTRIC JUICE produced by the GASTRIC GLANDS PRESENT IN THE STOMACH WALL catalyses the hydrolysis of PROTEINS into PEPTIDES in the STOMACH

Biology S3 (3 decks)

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