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Biology Chapter 6 (AQA) > Enzymes and Digestion > Flashcards

Enzymes and Digestion Flashcards

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1
Q

What is the human digestive system made up of?

A

A long muscular tube and its associated glands

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2
Q

What do the glands in the digestive system produce?

A

Enzymes

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3
Q

What is the role of enzymes in the digestive system?

A

They hydrolyse large molecules into smaller ones ready for absorption

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4
Q

What is the digestive system?

A

An exchange surface through which food substances are absorbed

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5
Q

What are the major parts of the digestive system?

A
  • the oesophagus
  • the stomach
  • the ileum
  • the large intestine
  • the rectum
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6
Q

What is the role of the oesophagus?

A

It carries food from the mouth to the stomach

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7
Q

What is the stomach?

A

A muscular sac with an inner layer that produces enzymes

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8
Q

What is the role of the stomach?

A

It stores and digests food (especially proteins(it has glands which produce enzymes to digest proteins))

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9
Q

What is the ileum?

A

A long muscular tube

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10
Q

What happens in the ileum?

A

Food is further digested by enzymes produced by ts walls and by its glands

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11
Q

What is the purpose of the ileum?

A

Absorbing the products of digestion into the blood stream

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12
Q

How is the ileum adapted to its purpose?

A

The inner walls are folded into villi which gives them a large surface area, the surface area of the villi is then increased by millions of tiny projections called microvili which are on the epithelial cells of each villus

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13
Q

What do the gland in the ileum do with the Secretions they produce?

A

They pour them onto the digesting food

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14
Q

What is the role of the large intestine?

A

Absorbing water

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15
Q

What is most of the water absorbed by the large intestine?

A

Water from the secretions of the many digestive glands

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16
Q

What is the role of the rectum?

A

It is where the faeces are stored before they are periodically removed via the anus in the process of egestion

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17
Q

Where are the salivary glands found?

A

Near the mouth

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18
Q

What do the salivary glands do?

A

They pass on their secretions via a duct in the mouth

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19
Q

What do the secretions from salivary glands contain?

A

The enzyme amylase which hydrolysed starch into maltose

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20
Q

What is the pancreas?

A

A large gland situated below the stomach

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21
Q

What does the pancreas produce?

A

Pancreatic juices

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22
Q

What does the pancreatic juice contain?

A
  • Proteases to hydrolysed proteins
  • Lipase to hydrolyse lipids
  • Amylase to hydrolyse starch
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23
Q

What are the two stages in digestion?

A
  • physical breakdown

- chemical digestion

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24
Q

Why does the physical breakdown of food take place?

A

To make the food possible to ingest and to provide a large surface area for chemical digestion

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25
Q

What are the two ways food can be physically broken down?

A

By the teeth and by the churning of food in the stomach by the muscles in the stomach wall

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26
Q

What does chemical digestion do?

A

It hydrolyses large, insoluble molecules into smaller, soluble ones

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27
Q

How is chemical digestion carried out?

A

By enzymes

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28
Q

How do all digestive enzymes function?

A

By hydrolysis

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29
Q

What is hydrolysis?

A

The splitting up of molecules by adding water to the chemical bonds that hold them together

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30
Q

What are enzymes?

A

Specific

31
Q

What can large molecules require more than one of to be broken down?

A

Type of enzyme

32
Q

How do enzymes usually act upon a large molecule?

A

A large molecule is hydrolysed into editions by one enzyme into sections and these sections can then be hydrolysed into smaller molecules by one or more additional enzyme

33
Q

What is the role of carbohydrases?

A

They hydrolyse carbohydrates, ultimately to monosaccharides

34
Q

What is the role of lipase?

A

They hydrolyse lipids into glycerol and fatty acids

35
Q

What is the role of proteases?

A

They hydrolyse proteins ultimately to amino acids

36
Q

Why is it important that enzymes are added to food in the correct sequence?

A

It usually takes multiple enzymes to completely hydrolyse a large molecule and each enzyme is specific to one substrate

37
Q

How is starch broken down by the body?

A
  • firstly amylase is produced in the mouth and the pancreas which hydrolyses the alternate glycosidic bonds so that the disaccharide maltose is produced
  • maltose is hydrolysed into the monosaccharide alpha glucose by a disaccharidase called maltase which is produced in the lining get of the ileum
38
Q

What is the process of carbohydrate digestion in humans?

A
  • saliva enters the mouth from salivary glands and contains salivary amylase which is mixed with the food during chewing to start hydrolysing starch to maltose ]
  • food is swallowed where is can enter the acidic conditions of the stomach
  • the food is then passed to the small intestine where it mixes wit pancreatic juices that contain pancreatic amylase which can continue the hydrolysis of any remaining starch to maltose
  • Muscles in the intestinal walls push the food along the ileum and the epithelial lining produces the membrane bound maltase which hydrolyses maltose into alpha glucose
39
Q

What does saliva contain?

A

Salivary amylase

40
Q

What is the optimum pH of saliva?

A

Around neutral

41
Q

How is salivary amylase optimum pH maintained?

A

By mineral salts in the saliva

42
Q

What happens to the salivary amylase when it reaches the stomach?

A

It is denatured by the acidic conditions preventing the further hydrolysis of starch

43
Q

What does the pancreatic juice contain for the digestion of carbohydrates?

A

Pancreatic amylase

44
Q

What does pancreatic amylase continue?

A

The hydrolysis of any remaining starch into maltose

45
Q

What is the optimum pH of pancreatic amylase??

A

Around neutral

46
Q

How is the optimum pH of pancreatic amylase maintained?

A

By alkaline salts produced by both the pancreas and the intestinal walls

47
Q

Where is maltase produced?

A

In the epithelial lining of the intestinal wall

48
Q

Where is maltase not released to?

A

The lumen of the ileum

49
Q

Why is maltase not released to the lumen of the ileum?

A

It is part of the cell-surface membrane of the epithelial cells that line the ileum

50
Q

What is maltase known as?

A

A membrane bound disaccharide

51
Q

What does maltase hydrolyse maltose into?

A

Alpha-glucose

52
Q

Aside from maltose, what are the two other common disaccharides in the diet that are hydrolysed in carbohydrate digestion?

A

Sucrose and lactose

53
Q

Where is sucrose found?

A

In many natural foods especially fruits

54
Q

Where is lactose found?

A

In milk and therefore in milk products such as yogurt an d cheese

55
Q

What is each disaccharide hydrolysed by in carbohydrate digestion?

A

A membrane bound disaccharide

56
Q

How does sucrase hydrolyse sucrose?

A

It hydrolyses the single glycosidic bond in the sucrose molecule to produce glucose and fructose

57
Q

How does lactase hydrolyse lactose?

A

It hydrolyses the single glycosidic bond in the lactose molecule to produce glucose and galactose

58
Q

What enzymes hydrolyse lipids?

A

Lipases

59
Q

What are lipases?

A

Enzymes produced in the pancreas that hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides

60
Q

What is a monoglyceride?

A

A glyceride is a glycerol molecule with a single fatty acid molecule attached

61
Q

What are lipids first split up into?

A

Tiny droplets called micelles

62
Q

How are lipids split into micelles?

A

By bile salts

63
Q

Where ate bile salts produced?

A

The liver

64
Q

What is the process of lipids being split into micelles called?

A

Emulsification

65
Q

What is the purpose of emulsification?

A

To increase the surface area of lipids so that the action of lipases is sped up

66
Q

What is the name of the group of enzymes that hydrolyse proteins?

A

Peptidases (proteases)

67
Q

What do endopeptidases hydrolyse?

A

The peptide bonds between amino acids in the central region of a protein molecule forming a series of peptide molecules

68
Q

What do exopeptidases hydrolyse?

A

The peptide bonds on the terminal amino acids of the peptide molecules formed by endopeptidases to progressively release dipeptides and single amino acids

69
Q

What do dipeptidases hydrolyse?

A

The bond between the two amino acids of a dipeptide

70
Q

What are dipeptidases?

A

Membrane bound

71
Q

Where are dipeptidases found?

A

In the cell surface membrane of the epithelial cells lining the ileum

72
Q

What happens to lactase levels as humans age?

A

Lactase levels naturally decrease as humans age due to milk forming a less significant role in our diets and some peoples lactase levels diminish entirely leading to lactose intolerance

73
Q

What happens to undigested lactose in lactose intolerant humans?

A

The undigested lactose will reach the large intestines where microorganisms hydrolyse it giving rise to mall soluble molecules and a large volume of gas

74
Q

Why does lactose intolerance result in diarrhoea?

A

Because the soluble molecules lower the water potential of the material in the colon

Biology Chapter 6 (AQA) (14 decks)

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