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Biology A level > Digestion > Flashcards

Digestion Flashcards

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1
Q

What part of the digestive system is responsible for the secretion of bile?

A

The liver

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2
Q

What is the pancreas’ function in the digestive system?

A

secretion of enzymes into the duodenum
Secretes pancreatic juices

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3
Q

What is the function of the colon in the digestive system

A

Reabsorption of water

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4
Q

What is the function of the rectum in the digestive system?

A

Storages of undigested food prior to removal

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5
Q

What is the function of the stomach in the digestive system?

A

Mechanical and chemical digestion of proteins in low pH

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6
Q

Where is bile stored?

A

The gall bladder

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7
Q

How does bile enter the duodenum?

A

Via the bile duct

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8
Q

How do bile salts help in the digestion of lipids?

A

Emulsification of the lipids turns them into micelles which makes them more soluble so they are easier to transport and increases SA for chemical digestion with lipase

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9
Q

Why are hydrogen Carbonate ions secreted into the duodenum?

A

They neutralise the stomach acids

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10
Q

Where would the villus be found in the human gut?

A

On the epithelial cells in the ileum

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11
Q

Why is is more efficient for the endopeptidases to act before the exopeptidases?

A

Increasing SA for exopeptidases to work on therefore faster hydrolysis of polypeptides

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12
Q

What are the two types of digestion?

A

Mechanical
Chemical

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13
Q

Where does mechanical digestion take place?

A

Teeth and stomach

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14
Q

What does mechanical digestion do?

A

Breaks down large pieces of food into smaller pieces to increases the SA for chemical digestion which overall increases the rate of digestion

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15
Q

Where does chemical digestion take place?

A

mouth
stomach
small intestine

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16
Q

What does chemical digestion do?

A

Speeds up the hydrolysis reactions of bonds breaking
Breaks down large insoluble molecules into smaller soluble ones

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17
Q

Why is it necessary that food needs to be digested to be absorbed?

A

Makes the food smaller and soluble so it can be transported across membrane to be blurbed into the blood plasma

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18
Q

What do glands do in the digestive system?

A

Produce enzymes

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19
Q

What does the oesophagus do?

A

Caries food from the mouth to the stomach

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20
Q

What is the function of the ileum in the digestive system?

A

Food is further digested by enzymes
Absorbs the products of digestion into the bloodstream

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21
Q

What is the function of the salivary glands?

A

Secretes saliva that contains amylase do break down starch

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22
Q

How does the stomach break down food?

A

Churns it by using its muscles in the stomach wall

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23
Q

Where does intracellular digestion take place?

A

In the epithelial cells of the ileum

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24
Q

What are the 3 functions of mucus?

A

Neutralises acid
Provides lubrication
Protects gut wall from acid erosion

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25
Q

Where is amylase produced?

A

The salivary glands and the pancreatic juices

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26
Q

What is the optimum pH of amylase?

A

pH 8

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27
Q

What part of carbohydrate digestion takes place in the mouth and duodenum?

A

Hydrolysis of starch into maltose

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28
Q

What part of carbohydrate digestion takes place in the ileum?

A

Maltese hydrolysing maltose into alpha glucose

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29
Q

Describe carbohydrate digestion

A

Starch is broken down my amylase to produce maltose in the mouth and the duodenum
The amylase hydrolysis the glycosidic bonds
Then in the ileum
Maltase hydrolysis the glycosidic bonds in maltose to alpha glucose

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30
Q

What is an endopeptidase?

A

Hydrolyses the peptide bonds between amino acids in the central region of the protein forming smaller polypeptide chains

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31
Q

What part of protein digestion takes place in the stomach?

A

Endopeptidases hydrolysing proteins into smaller polypeptide chains

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32
Q

What are exopeptidases?

A

Hydrolyses peptide bonds on the terminal amino acids on the end of the polypeptide chain
They release single amino acids and dipeptides

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33
Q

What part of protein digestion takes place in the duodenum?

A

Exopeptidases hydrolysing polypeptide chains into amino acids and dipeptides

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34
Q

What are the 3 types of exopeptidases?

A

Carboxypeptidase
Aminopeptidase
Dipeptidase

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35
Q

Why are peptidases secreted in an inactive form?

A

To protect the gut from harm as they would breakdown the gut

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36
Q

What are dipeptidases?

A

Hydrolyses the bond between two amino acids in a dipeptide
Membrane-bound part of the epithelial cells of the ileum

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37
Q

What part of protein digestion takes place in the ileum?

A

Dipeptidases hydrolysing dipeptides into amino acids

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38
Q

What type of digestion is breaking lipid droplets down to micelles?

A

Mechanical digestion

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39
Q

What are the role of bile salts?

A

Emulsification of lipids into micelles

40
Q

What is the role of sodium hydrogen carbonate in lipid digestion?

A

Neutralises the stomach acid for the optimum pH of lipase - pH 8

41
Q

Why are micelles produced in lipid digestion?

A

To increase SA for lipase to act on fatty acids for faster hydrolysis and digestion of lipids
makes transporting lipids and fatty acids easier to transport and more soluble

42
Q

What is the function of micelles in digestion?

A

Makes lipids more soluble and easier to transport through membranes to the intestinal epithelial cells

43
Q

What are the two sites of secretion for amylase?

A

Salivary glands and pancreas

44
Q

Where are the two sites of action for amylase?

A

Mouth and duodenum

45
Q

Where are the two sites of secretion for endopeptidases?

A

Gastric glands and pancreas

46
Q

What are the two sites of action of endopeptidases?

A

Stomach and duodenum

47
Q

What are the two sites of secretion for exopeptidases?

A

Pancreas and epithelial cells

48
Q

What are the two sites of action of exopeptidases?

A

Duodenum and ileum

49
Q

What is the site of secretion for lipase?

A

Pancreas

50
Q

What is the site of action for lipase?

A

Duodenum

51
Q

What is the site of secretion of disaccharidases?

A

Epithelial cells

52
Q

Where is the site of action for disaccharidases?

A

Ileum

53
Q

What are all the parts of the human digestive system?

A

Mouth
Tongue
Salivary gland
Oesophagus
Stomach
Liver
Gall bladder
Bile duct
Pancreas
Duodenum
Ileum
Appendix
Colon
Rectum
Anus

54
Q

What parts of the digestive system are part of the alimentary canal?

A

Mouth
Oesophagus
Stomach
Duodenum
Ileum
Appendix
Colon
Rectum
Anus

55
Q

How is starch broken down in the mouth by chemical digestion?

A

Chemicals come from salivary glands that secrete saliva that contains amylase and breaks down starch

56
Q

What is in saliva?

A

Amylase
Mucus
Mineral ions

57
Q

What is the role of mineral ions in saliva?

A

Maintains pH

58
Q

What are the two layers of muscle in the oesophagus?

A

Circular and longitudinal muscle

59
Q

What happens when the circular muscles in the oesophagus contract?

A

Contracts to squeeze the gut

60
Q

What happens when the longitudinal muscles contracts in the oesophagus?

A

Contracts to shorten the gut

61
Q

What is the optimum pH in the stomach?

A

pH 2

62
Q

Why is there an extra layer of muscle in the stomach?

A

For mechanical digestion - the muscles contract to churn contents to form acidic chyme

63
Q

What are the 3 types of muscle in the stomach?

A

Longitudinal
Circular
Oblique

64
Q

What is the role of HCl stomach acid?

A

Maintains pH to activate enzymes and to kill bacteria

65
Q

What is bile made of?

A

Bile salts
Sodium hydrogen carbonate

66
Q

What is in pancreatic juices?

A

Amylase
Lipase
Exopeptidases
Endopeptidases
Hydrogen carbonate ions

67
Q

What does the Brunner’s gland do in the gut wall?

A

Releases mucus

68
Q

What substances in the duodenum neutralises the acids from the stomach?

A

Sodium hydrogen carbonate
Mucus
Hydrogen carbonate ions

69
Q

What is the process of carbs and proteins being digestion in the ileum?

A

Hydrolysis of enzymes in the membrane of microvilli
Crosses the membrane with enzymes breaking them down - constant hydrolysis
Digestion occurs as absorption occurs
Diffuses into blood capillary

70
Q

What is assimilation?

A

How the products of digestion are used by the body cells

71
Q

How are mooglycerides and fatty acids used by cells?

A

The formation of cell membranes

72
Q

How do villi and microvilli increase absorption efficiency in the ileum?

A

Larger SA for carrier proteins for facilt. Diff. Increases SA for diffusion

73
Q

How does a thin gut wall increase absorption efficiency in the ileum?

A

Shorter diffusion pathway for absorption

74
Q

How do muscle layers increase absorption efficiency in the ileum?

A

Ensures molecules are kept in contact with villi - increases rates of absorption

75
Q

What are all the parts of a villus?

A

Epithelial cell
Goblet cells
Lacteal
Nerve
Capillary
Lymphatic vessel
Smooth muscle

76
Q

What products does the lacteal absorb?

A

Products of lipid digestion

77
Q

What products does the capillary network absorb?

A

Products of carbs and proteins digestion

78
Q

Describe the process of absorption of lipids

A

Fatty acids and monoglycerides leave the micelles and enter the epithelial cells of mucosa by simple diff

Fatty acids and monoglycerides reform as triglycerides

Chemical modification in the Golgi body - combines with proteins to form chylomicrons

Chylomicrons released from the epithelial cells by exocytosis and enters the lacteal

Chylomicrons in the lymph are transported to the thoracic duct and enter the blood stream

79
Q

Why do lipids become chylomicrons?

A

Makes them soluble in water to be absorbed in the blood plasma and be transported by mass flow

80
Q

Summarise absorption of glucose/amino acids by sodium co-transport?

A
  1. Sodium ions actively pumped out and potassium ions actively transported in
  2. Sodium conc grad forms so sodium ions actively transported out
  3. Co-transport of glucose and sodium ions
  4. Glucose leaves the epithelial cell into the blood by facial.diff
81
Q

Describe the sodium and potassium pump in co-transport.

A

Sodium ions are pumped out as potassium ions are actively transported in

82
Q

Describe the concentration grad of sodium forming in co-transport.

A

The sodium conc falls due to actively pumped out
Sets up a conc grad of sodium ions between the lumen of the ileum and in the ileum wall

83
Q

Describe the co-transport of sodium ad glucose.

A

Sodium ions actively transported from ileum epithelial cell to blood
maintains and forms a grad for sodium to diffuse from the ileum lumen to the epithelial cell
Glucose enters cell by faciliated diff with sodium ions

84
Q

What protein is the sodium and potassium ion pump?

A

Anti-port

85
Q

What is indirect active transport in co-transport of glucose?

A

Uses ATP from the active transport of sodium ions in the pumping out ofte ileum

86
Q

Describe assimilation of glucose in the liver.

A

glucose transported from the ileum to liver
Excess glucose is coveted to glycogen and stores in the liver
Some glucose is transported to other tissues

87
Q

Why doesn’t the liver stored amino acids?

A

Nitrogen in high conc is toxic to cells

88
Q

What is deamination of amino acids in the liver.

A

Removes the amino group and the H atom from the central carbon

89
Q

How is the amino group removed in deamination?

A

Forms ammonia which is toxic to cells
Converted into urea which can now bc excreted as urine

90
Q

Where is maltase produced?

A

In the epithelium of the small intestine

91
Q

What are all the adaptations of intestinal epithelial cells?

A

microvilli
villi
one cell thick villus wall
blood capillaries
lacteal
co-transport proteins

92
Q

How do the microvilli and villi increase absorption of nutrients?

A

increase SA for absorption
microvilli = more nutrients come in contact with the cell
villi = increase SA of the cells

93
Q

How do blood capillaries increase absorption of nutrients in the intestinal epithelial cells?

A

transport glucose and amino acids away from small intestine = maintain conc grad

94
Q

How does the lacteal increase absorption of nutrients in the intestinal epithelial cells?

A

runs through the centre of the villus and transports fatty acids and glycerol away from the small intestine

95
Q

What is a micelle?

A

water soluble vesicles formed of fatty acids, glycerides, monoglycerides and bile salts

Biology A level (27 decks)

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