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biomolecules and cells > Regulation of digestion > Flashcards

Regulation of digestion Flashcards

1
Q

What is physical digestion?

A

the physical breakdown of food into small particles by grinding or chewing to increase surface area

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2
Q

What is Enzymatic Digestion?

A

The breakdown of complex food molecules by hydrolytic enzymes usually secreted into the gut lumen
- so that food molecules are broken down into monomers that can be absorbed and utilised by cells

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3
Q

Why is digestion necessary?

A
  • major food nutrients are large macromolecules which cannot pass through the lining of the itestine
  • therefore must be broken down to small molecules via chemical and physical digestion to pass through cell membranes
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4
Q

Incisors

A

required for cutting, chopping or gnawing

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5
Q

Canines

A

For stabbing, ripping and shredding

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6
Q

Molars and Premolars

A

for shearing, crushing and grinding

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7
Q

What is the hard material covering the tooth?

A

Enamel - Calcium Phosphate

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8
Q

What is involved in the enzymatic reaction in the mouth?

A

Enzyme - amylase

Substrate - Starch/glycogen

End product - Maltose (disaccharide)

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9
Q

What is the oesophagus

A

Muscular tube which transports food through the thorax and diaphragm to the stomach

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10
Q

What are the 3 types of secretory cells in the gastric pits of the stomach?

A
  1. chief cells - secrete pepsinogen
  2. parietal cells - produce hydrochloric acid
  3. epithelial cells - secrete mucus which protects the tissues from the acids and enzymes
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11
Q

Stomach

A
  • thick muscular walls to churn food
  • secretes protective mucus from secretory cells
  • gastric glands secrete gastric juice including HCl and pepsin
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12
Q

Describe the enzymatic reaction that occurs in the stomach

A

Enzyme - pepsin

Substrate - proteins

End product - large peptides

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13
Q

What is the small intestine and its function?

A
  • long muscular tube/large SA
  • moves chyme forwards from the stomach
  • continues enzymatic digestion with secretions from cells in its walls and from accessory digestive glands
  • absorbs products of digestion through villi
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14
Q

What are the 3 different regions of the small intestine?

A
  1. duodenum
  2. jejunem
  3. ileum
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15
Q

Where is bile produced and secreted?

A

the liver

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16
Q

Why does the pancreas produce bicarbonate solution?

A

Bicarbonate is required to neutralise the pH of the chyme released from the stomach

17
Q

Where does bile travel?

A
  • bile flows through the hepatic duct to the duodenum

* through the cystic duct to the gallbladder where bile is stored

18
Q

Briefly describe the digestion of fats?

A
  1. dietary fats are emulsified into tiny droplets called micelles - through the action of bile salts
  2. pancreatic lipase hydrolyses fats in micelles to produce fatty acids and monoglycerides
  3. fatty acids and monoglycerides enter the cell by diffusion - resynthesised into triglycerides in the ER
  4. Triglycerides are packaged with cholesterol and phospholipids
19
Q

What happens in the large intestine?

A
  • Absorption of water and inorganic ions

* formation and storage of faeces from undigestible material - periodically excreted through the rectum

20
Q

How do bacteria contribute to digestion?

A
  • they obtain nutrition from passing food
  • prevent harmful microbes from establishing
  • produce vitamins K and biotin
21
Q

Where is pepsin found?

A

Stomach

22
Q

Describe the absorption of carbohydrates in the small intestine

A
  • absorbed as monosaccharides into capillaries of villi
  • glucose is taken up by active transport
  • blood vessels drain into hepatic portal vein which carries blood to liver
  • the liver converts carbohydrates into glycogen which is stored in the liver
23
Q

How are proteins absorbed in the small intestine?

A
  • absorbed into capillaries as amino acids
  • taken up directly by cells which are synthesising proteins
  • excess de-aminated by liver which uses nitrogen to form urea for excretion
24
Q

Absorption of water, salts and alcohol in the small intestine

A
  • may be absorbed directly into underlying blood vessels irrespective of need
  • excess excreted by kidneys
  • alcohol is absorbed directly through the stomach - hence the rapidity of intoxication
25
Q

How are fats absorbed in the small intestine?

A
  • Fats absorbed as glycerol and neutralised fatty acids into lacteals and then via lymphatics back to major veins near the heart
  • excess store in adipose tissue
26
Q

What secretions occur in the stomach and what stimulates these secretions?

A
  • food entering the stomach stimulates the release of the hormone gastrin from the stomach mucosa into the blood
  • this causes the release of HCl and pepsin from the stomach mucosa
27
Q

What hormones are secreted in the duodenum and what stimulates this secretion?

A
  • acid in the duodenum causes the release of the hormone secretin from intestinal mucosa into the blood
  • this causes the pancreas to release HCO3- and the gall bladder to release bile
28
Q

How is the secretion of saliva control?

A

under nervous control

29
Q

What is peristalsis?

A

The involuntary constriction and relaxation of the circular muscles in the oesophagus to push the food bolus to the stomach
(peristalsis can occur in intestine or other canal)

30
Q

What is the phyloric sphincter?

A
  • between the stomach and the duodenum of the small intestine
  • acts as a valve to control the flow of partially digested food from the stomach to the small intestine
31
Q

Where is amylase found?

A

salivary glands and pancreas

32
Q

where is protease found?

A

Pancreas and stomach

33
Q

where is lipase found?

A

pancreas

34
Q

What is the caecum?

A

A large sac like structure that is the first part of the large intestine

35
Q

What is the colon?

A 
• The section in the large intestine after the caecum
• has 3 other sections
- ascending
- transverse (Across the body)
- descending
36
Q

What is the rectum?

A

Last section of the large intestine

• terminates at the anus - a sphincter that control the exit of faeces from the digestive system

37
Q

What are the 3 main sections of the large intestine?

A
  1. caecum
  2. colon (Ascending, transvers, descending)
  3. rectum
38
Q

List the major components of the digestive system in order

A
  1. mouth
  2. oesophagul sphincter
  3. stomach
  4. phyloric sphincter
  5. pancreas
  6. hepato- pancreatic duct
  7. small intestine - dueodenum, ileum
  8. large intestine - caecum, colon , rectum
  9. anus
39
Q

Pepsin formation

A

Pepsinogen is secreted by chief cells in the stomach

• when it comes into contact with stomach acid it is converted to the active form pepsin

biomolecules and cells (32 decks)

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