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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
Where is amylase produced?
The salivary glands and the pancreatic juices
26
What part of carbohydrate digestion takes place in the mouth and duodenum?
Hydrolysis of starch into maltose
27
What part of carbohydrate digestion takes place in the ileum?
Maltese hydrolysing maltose into alpha glucose
28
Describe carbohydrate digestion
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
29
What is an endopeptidase?
Hydrolyses the peptide bonds between amino acids in the central region of the protein forming smaller polypeptide chains
30
What part of protein digestion takes place in the stomach?
Endopeptidases hydrolysing proteins into smaller polypeptide chains
31
What are exopeptidases?
Hydrolyses peptide bonds on the terminal amino acids on the end of the polypeptide chain They release single amino acids and dipeptides
32
What part of protein digestion takes place in the duodenum?
Exopeptidases hydrolysing polypeptide chains into amino acids and dipeptides
33
Why are peptidases secreted in an inactive form?
To protect the gut from harm as they would breakdown the gut
34
What are dipeptidases?
Hydrolyses the bond between two amino acids in a dipeptide Membrane-bound part of the epithelial cells of the ileum
35
What part of protein digestion takes place in the ileum?
Dipeptidases hydrolysing dipeptides into amino acids
36
What type of digestion is breaking lipid droplets down to micelles?
Mechanical digestion
37
What are the role of bile salts?
Emulsification of lipids into micelles
38
What is the role of micelles in the absorption of fats into the epithelial cells?
To increase SA for lipase to act on fatty acids for faster hydrolysis and digestion of lipids makes fatty acids more soluble in water maintain high conc of fatty acids to the cell fatty acids absorbed by diffusion brings fatty acids to the cell lining of the ileum
39
What is the function of micelles in digestion?
Makes lipids more soluble and easier to transport through membranes to the intestinal epithelial cells
40
What are the two sites of secretion for amylase?
Salivary glands and pancreas
41
Where are the two sites of action for amylase?
Mouth and duodenum
42
Where are the two sites of secretion for endopeptidases?
Gastric glands and pancreas
43
What are the two sites of action of endopeptidases?
Stomach and duodenum
44
What are the two sites of secretion for exopeptidases?
Pancreas and epithelial cells
45
What are the two sites of action of exopeptidases?
Duodenum and ileum
46
What is the site of secretion for lipase?
Pancreas
47
What is the site of action for lipase?
Duodenum
48
What is the site of secretion of disaccharidases?
Epithelial cells
49
Where is the site of action for disaccharidases?
Ileum
50
What are all the parts of the human digestive system?
Mouth Tongue Salivary gland Oesophagus Stomach Liver Gall bladder Bile duct Pancreas Duodenum Ileum Appendix Colon Rectum Anus
51
What parts of the digestive system are part of the alimentary canal?
Mouth Oesophagus Stomach Duodenum Ileum Appendix Colon Rectum Anus
52
How is starch broken down in the mouth by chemical digestion?
Chemicals come from salivary glands that secrete saliva that contains amylase and breaks down starch
53
What is in saliva?
Amylase Mucus Mineral ions
54
What is the role of mineral ions in saliva?
Maintains pH
55
What are the two layers of muscle in the oesophagus?
Circular and longitudinal muscle
56
What happens when the circular muscles in the oesophagus contract?
Contracts to squeeze the gut
57
What happens when the longitudinal muscles contracts in the oesophagus?
Contracts to shorten the gut
58
What is the optimum pH in the stomach?
pH 2
59
Why is there an extra layer of muscle in the stomach?
For mechanical digestion - the muscles contract to churn contents to form acidic chyme
60
What are the 3 types of muscle in the stomach?
Longitudinal Circular Oblique
61
What is the role of HCl stomach acid?
Maintains pH to activate enzymes and to kill bacteria
62
What is bile made of?
Bile salts Sodium hydrogen carbonate
63
What is in pancreatic juices?
Amylase Lipase Exopeptidases Endopeptidases Hydrogen carbonate ions
64
What does the Brunner’s gland do in the gut wall?
Releases mucus
65
What substances in the duodenum neutralises the acids from the stomach?
Sodium hydrogen carbonate Mucus Hydrogen carbonate ions
66
What is the process of carbs and proteins being digestion in the ileum?
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
67
What is assimilation?
How the products of digestion are used by the body cells
68
How are mooglycerides and fatty acids used by cells?
The formation of cell membranes
69
How do villi and microvilli increase absorption efficiency in the ileum?
Larger SA for carrier proteins for facilt. Diff. Increases SA for diffusion
70
How does a thin gut wall increase absorption efficiency in the ileum?
Shorter diffusion pathway for absorption
71
How do muscle layers increase absorption efficiency in the ileum?
Ensures molecules are kept in contact with villi - increases rates of absorption
72
What are all the parts of a villus?
Epithelial cell Goblet cells Lacteal Nerve Capillary Lymphatic vessel Smooth muscle
73
What products does the lacteal absorb?
Products of lipid digestion
74
What products does the capillary network absorb?
Products of carbs and proteins digestion
75
Describe the process of absorption of lipids
Fatty acids and monoglycerides leave the micelles and enter the epithelial ells 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 so that they can enter the bloodstream
76
Why do lipids become chylomicrons?
Makes them soluble in water to be absorbed in the blood plasma and be transported by mass flow
77
Summarise absorption of glucose/amino acids by sodium co-transport?
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
78
Describe the sodium and potassium pump in co-transport.
Sodium ions are pumped out as potassium ions are actively transported in
79
Describe the concentration grad of sodium forming in co-transport.
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
80
Describe the co-transport of sodium ad glucose.
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
81
What protein is the sodium and potassium ion pump?
Anti-port
82
What is indirect active transport in co-transport of glucose?
Uses ATP from the active transport of sodium ions in the pumping out ofte ileum
83
Describe assimilation of glucose in the liver.
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
84
Why doesn’t the liver stored amino acids?
Nitrogen in high conc is toxic to cells
85
What is deamination of amino acids in the liver.
Removes the amino group and the H atom from the central carbon
86
How is the amino group removed in deamination?
Forms ammonia which is toxic to cells Converted into urea which can now bc excreted as urine
87
Where is maltase produced?
In the epithelium of the small intestine
88
What are all the adaptations of intestinal epithelial cells?
microvilli villi one cell thick villus wall blood capillaries lacteal co-transport proteins
89
How do the microvilli and villi increase absorption of nutrients?
increase SA for absorption microvilli = more nutrients come in contact with the cell villi = increase SA of the cells
90
How do blood capillaries increase absorption of nutrients in the intestinal epithelial cells?
transport glucose and amino acids away from small intestine = maintain conc grad
91
How does the lacteal increase absorption of nutrients in the intestinal epithelial cells?
runs through the centre of the villus and transports fatty acids and glycerol away from the small intestine
92
What is a micelle?
water soluble vesicles formed of fatty acids, glycerides, monoglycerides and bile salts
93
Describe the complete digestion of starch by a mammel
amylase breaks down starch into maltose in the mouth by hydrolysing glycosidic bonds Maltase is a membrane-bound disaccharides and breaks down maltose into glucose
94
what is a membrane-bound disaccharides?
enzymes in the cell membrane of the epithelial cells of the ileum they catalyse the hydrolysis of disaccharides into monosaccharides

Biology A level (36 decks)

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