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AQA A level Biology > 3.3 Digestion > Flashcards

3.3 Digestion Flashcards

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1
Q

What are the 2 types of digestion

A
  • Mechanical/ physical
  • Chemical
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2
Q

What 2 structures in the body are involved in physical digestion

A
  • Teeth and stomach
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3
Q

Why is physical digestion important

A

-To break larger pieces into smaller ones
- Providing a large surface area for chemical digestion
- Increasing the rate of digestion

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4
Q

What does chemical digestion do

A

It hydrolyses large, insoluble molecules into smaller soluble ones

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5
Q

Explain why it is necessary for food to be digested, in order to be absorbed into our body

A

To make it smaller and soluble so that it can be transported across the membrane to be absorbed into the blood plasma

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6
Q

What are the 3 functions of mucus

A
  • Lubricant
  • Neutralises acids
  • Protects gut wall from acid erosion
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7
Q

Where is amylase secreted from

A
  • Salivary glands
  • Pancreas
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8
Q

What does amylase hydrolyse

A

Starch

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9
Q

What are the products of amylase when starch is hydrolysed

A

Maltose

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10
Q

Where are the sites of action for amylase

A

-Mouth (salivary glands)
- Duodenum (pancreatic juices)

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11
Q

Roughly what is the optimum pH of amylase

A

About 8

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12
Q

What type of bond does amylase hydrolyse

A

Glycosidic bonds

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13
Q

Where is maltase found

A

In the ileum

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14
Q

What is the substrate for endopeptidase

A

Proteins/ polypeptides

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15
Q

What is the product from endopeptidase

A

Shorter polypeptides

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16
Q

Where are endopeptidases secreted from

A
  • Gastric glands
  • Pancreas
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17
Q

Where are the sites of action for endopeptidases

A
  • Stomach
  • Duodenum
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18
Q

What are the substrates for exopeptidases

A

Short polypeptides

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19
Q

What are the products from exopeptidases

A
  • Amino acids
  • Dipeptides
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20
Q

Where are exopeptidases secreted from

A
  • Pancreas
  • Epithelial cells
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21
Q

Where are the sites of action of exopeptidases

A

Duodenum
Ileum

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22
Q

What is the substrate for lipase

A

Lipids

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23
Q

What are the products from lipase

A
  • Monoglycerides
  • Fatty acids
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24
Q

Where are lipase secreted from

A

Pancreas

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25
Q

Where is the site of action for lipase

A

Duodenum

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26
Q

What is the substrate for disaccharidases

A

Disaccharides

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27
Q

What is the product from disaccharidases

A

Monosaccharides

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28
Q

Where are disaccharidases secreted from

A

Epithelial cells

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29
Q

Where is the site of action for disaccharidases

A

Ileum

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30
Q

Do endopeptidases or exopeptidases hydrolyse the bonds at the end of the chain

A

Exopeptidases

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31
Q

Why are endopeptidases secreted inactive

A

So they don’t digest the gut wall before they reach the stomach or the duodenum

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32
Q

Where is bile produced

A

Liver

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33
Q

Where is bile stored

A

Gallbladder

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34
Q

What is the name of tube where bile travels from the gallbladder to the duodenum

A

Bile duct

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35
Q

What are the 2 components of bile

A
  • Bile salts
  • Sodium hydrogen carbonate
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36
Q

What is the name of the process from which lipid droplets become micelles

A

Emulsification

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37
Q

What does sodium hydrogen carbonate do

A

Neutralises stomach acid

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38
Q

Micelles make the lipids more _______ so therefore easier to _______

A
  1. Soluble
  2. Transport
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39
Q

What is the pH range in the mouth

A

6.5-7.5

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40
Q

What types of digestion happen in the mouth

A
  • Physical/ mechanical
  • Chemical
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41
Q

What feature in the mouth carries out physical digestion

A

Teeth - increase the SA for chemical digestion

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42
Q

What is digested by chemical digestion in the mouth

A

Starch only

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43
Q

What are the 3 components of saliva

A
  • Amylase
  • Mucus
  • Mineral ions
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44
Q

What is the role of amylase in saliva

A

To breakdown starch

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45
Q

What is the role of mucus in saliva

A

Lubricant

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46
Q

What is the role of mineral ions in saliva

A

Maintain pH

47
Q

What is the name given to the process where there is co-ordinated contractions

A

Peristalsis

48
Q

What is the role of goblet cells

A

To secrete mucus

49
Q

What are the general 2 muscles in the digestive system

A
  • Circular muscle
  • Longitudinal muscle
50
Q

What does the contraction of circular muscles do to the gut

A

Squeeze the gut

51
Q

What does the contraction of the longitudinal muscles do to the gut

A

Shorten the gut

52
Q

What is the name given to the ball of food that travels down the oesophagus

A

Food bolus

53
Q

What is the role of mucus in the oesophagus

A

Lubrication

54
Q

What is the pH in the stomach

A

pH 2

55
Q

What is the name of the soupy consistancy product formed from the stomach churning

A

Acidic chyme

56
Q

What biological molecule is chemically digested in the stomach

A

Proteins only

57
Q

What does the gastric gland secrete

A

Gastric juice

58
Q

What are the 3 components of gastric juice

A
  • Endopeptidase
  • Mucus
  • HCl
59
Q

What are the functions of mucus in the stomach

A
  • Lubricant
  • Protect the lining from acid erosion
60
Q

What are the functions of HCl in the stomach

A
  • Maintains pH to activate enzymes
  • Kill bacteria
61
Q

What part of the digestive system is the main site of chemical digestion

A

Duodenum

62
Q

What are the 2 external glands to the duodenum

A
  • Liver
  • Pancreas
63
Q

What does the liver secrete

A

Bile

64
Q

What are the 4 components of pancreatic juice

A
  • Amylase
  • Endo and Exopeptidases
  • Lipase
  • Hydrogen carbonate ions
65
Q

What is the name of the gland in the gut wall of the duodenum

A

Brunner’s gland

66
Q

What is secreted from the Brunner’s gland, and what is its function

A

Mucus
- Neutralise stomach acid
- Protect the lining from acidic erosion

67
Q

Where is the final region of chemical digestion

A

The ileum

68
Q

Where are the enzymes in the ileum

A

In the microvilli, so the wall before the lumen

69
Q

What is absorbed in the colon

A
  • Water
  • Vitamins
70
Q

Why is water absorbed in the colon

A

To produce solidified faeces

71
Q

Why do we need to have solidified faeces

A

In order to stimulate peristalsis

72
Q

What synthesises the vitamins in the colon

A

The bacteria

73
Q

Why is cellulose needed in the diet if it cannot be digested

A

It provides bulk since the fibres provide the solidity to the faeces

74
Q

How do bile salts help the digestion of lipids

A

They emulsify them which increases the surface area for lipase

75
Q

Why are hydrogen carbonate ions secreted into the duodenum

A

To neutralise the stomach acid

76
Q

What is assimilation

A

How molecules are used by the cell, used for their relative process

77
Q

What are amino acids used for by the cell

A

Protein synthesis

78
Q

What are fatty acids and monoglycerides used for by the cell

A

Formation of cell membrane

79
Q

What type of surface is the ileum

A

Exchange surface

80
Q

What are the 4 features of the ileum that increase absorption efficiency

A

-Villi and microvilli
- Thin gut wall
- Muscle layer
- Blood flow carries the products away

81
Q

How do villi and microvilli increase absorption efficiency in the ileum

A

They increase the surface area, so more carrier proteins therefore more molecules can pass through the membrane at one time

82
Q

How does the ileum having a thin gut wall increase absorption efficiency

A

Shorter diffusion pathway, so increased rate of absorption

83
Q

How do the muscle layers in the ileum increase absorption efficiency

A

They ensures that the molecules are in contact with the villi, so a concentration gradient is maintained

84
Q

Why does blood flow carrying products away in the ileum increase absorption efficiency

A

It maintains the concentration gradient

85
Q

Once molecules are absorbed into the lumen of the ileum, which 2 ‘tubes’ can the be absorbed into

A
  • Capillary
  • Lacteal
86
Q

What product of digestion is absorbed into the lacteal

A

Products of lipid digestion

87
Q

What products of digestion are absorbed into capillaries

A

Products of protein and carbohydrates digestion

88
Q

Before lipids are absorbed into the epithelial cells of the ileum, what do the fatty acids and monoglycerides leave first

A

The micelle

89
Q

Once inside the epithelial cell of the ileum, what happens to the fatty acids and the monoglycerides

A

The reform as triglycerides

90
Q

Once triglycerides have been formed in the epithelial cells of the ileum, what happens to them- what are they combined with, what is the new name of them

A
  • The triglycerides are chemically modified in the golgi body
  • Triglycerides are combined with proteins
  • Forming chlyomicrons
91
Q

Once the chlyomicrons are formed in the epithelial cells of the ileum, what is the name of the process by which they leave the epithelial cell

A

Exocytosis

92
Q

Once chlyomicrons leave the epithelial cell of the ileum, where do they go

A

Into the lacteal

93
Q

What is the name of the duct that the chlyomicrons are transported to once in the lacteal

A

Thoracic duct - then into the blood stream

94
Q

Why do chlyomicrons have to go through the lacteal and the lymphatic system instead of diffusing directly into the blood stream

A

Because its too large to fit through the fenestrations of the capillary

95
Q

What is the name of the pump which starts the absorption process of glucose or amino acids

A

Sodium, potassium pump

96
Q

When absorbing glucose/ amino acids, what is the 1st step of the process, bonus points if you can name the type of co-transporter protein it is

A

Sodium ions are actively out of the ileum into the tissue fluid through a antiporter while potassium ions are actively transported into the ileum

97
Q

When absorbing glucose/amino acids, what happens after the sodium ions have been pumped out of the ileum

A

This sets up a concentration gradient for sodium between the lumen of the ileum and the ileum wall

98
Q

When absorbing glucose/ amino acids, what happens once a sodium concentration gradient has been set up, bonus points for the name of the co-transporter protein

A

Sodium is transported down it’s concentration gradient through a symport protein, while pulling glucose/ amino acids into the ileum wall too- by indirect active transport

99
Q

When absorbing glucose/ amino acids, how does the glucose/ amino acids enter the tissue fluid from the ileum wall

A

A concentration gradient has been set up so glucose/ amino acids can now facilitated diffuse down their own gradient into the tissue fluid

100
Q

When there is excess glucose/ amino acids what is the name of the vein that takes it away from the ileum, and where does this vein take it

A
  • Hepatic portal vein
  • From ileum to liver
101
Q

What is excess glucose converted into at the liver, and why is it converted to this

A

Into glycogen so it can be stored in the liver

102
Q

What is the name of the process that happens to excess amino acids in the liver

A

Deamination

103
Q

What is deamination

A

Where the liver removes the amino group and the hydrogen on the amino acid

104
Q

Why does deamination occur

A

Because amino acids in high concentrations are toxic, so removing the ammonia from the amino acid and converting into urea to excrete is beneficial

105
Q

Explain why it is more efficient for the endopeptidase enzymes to act before the exopeptidases

A
  • Endopeptidases hydrolyse the internal peptide bonds
  • Therefore increasing the surface area
  • For exopeptidases to act on
  • So a faster rate of break down
106
Q

What is ingestion

A

The taking in of food

107
Q

What does the epiglottus do

A

Blocks the trachea when swallowing food

108
Q

Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels (5 marks)

A
  • Micelles contain bile salts and fatty acids/ monoglycerides
  • Make fatty acids/ monoglycerides more soluble in water
  • Fatty acids/ monoglycerides absorbed by diffusion
  • Triglycerides reformed in cells
  • Vesicles move to cell membrane
109
Q

The movement of Na+ ions out of the cell allows the absorption of glucose into the cell lining the ileum. Explain how. (2 marks)

A
  • Generates a concentration gradient for Na+ ions
  • Na+ ions moving in by facilitated diffusion, brings glucose with it
110
Q

Describe the role of micelles in the absorption of fats into the cells lining the ileum. (3 marks)

A
  • Micelles include bile salts and fatty acids
  • Make the fatty acids more soluble in water
  • Brings fatty acids to the lining of the ileum
  • Maintain higher concentration of fatty acids to the lining of the ileum
  • Fatty acids absorbed by diffusion
111
Q

Describe the role of enzymes in the digestion of proteins in a mammal (4 marks)

A
  • Hydrolysis of peptide bonds
  • Endopeptidase act in the middle of protein/ polypeptide
  • Exopeptidases act at end of protein/ polypeptide
  • Dipeptidases acts on dipeptides/ between 2 amino acids
112
Q

Explain the advantages of lipid droplet and micelle formation (3 marks)

A
  • Droplets increase surface area for lipase action
  • So faster hydrolysis of lipids/ triglycerides
  • Micelles carry fatty acids and glycerol through membrane to cells
113
Q

Cell lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. Explain how. (3 marks)

A
  • Sodium ions actively transported from ileum cell to blood
  • Forms diffusion gradient fro sodium ions to enter cells from guy and with it glucose
  • Glucose enters by facilitated diffusion with sodium ions

AQA A level Biology (32 decks)

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