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NME > Macro and micronutrients: digestion > Flashcards

Macro and micronutrients: digestion Flashcards

1
Q

What are the three major macronutrients?

A

Carbohydrate, fat, and protein.

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2
Q

What is hydrolysis?

A

Hydrolysis is a decomposition reaction where water is used to break down the chemical bonds within food substances.

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3
Q

Name the stages of digestion for carbohydrates, fats, and proteins.

A

The stages of digestion for carbohydrates, fats, and proteins occur in the oral cavity, the stomach, and the small intestine.

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4
Q

Which substance is subject to hydrolysis during digestion?

A

Carbohydrates, fats, and proteins are all subject to hydrolysis during digestion.

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5
Q

Where does the digestion of carbohydrates, fats, and proteins occur?

A

The digestion of carbohydrates, fats, and proteins occurs in the oral cavity, the stomach, and the small intestine.

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6
Q

What are the two forms of glucose polymers found in CHO?

A

The two forms of glucose polymers found in CHO are amylose and amylopectin.

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7
Q

How is starch digested in the oral cavity?

A

: In the oral cavity, the enzyme salivary α-amylase hydrolyzes α1-4 glycosidic bonds in starch, forming maltose, maltotriose, and α-dextrins.

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8
Q

Does starch digestion occur in the stomach?

A

No, starch digestion does not occur in the stomach as the salivary amylase is inactivated by the acidic nature of gastric secretions.

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9
Q

Where does further digestion of starch occur?

A

Further digestion of starch occurs in the small intestine.

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10
Q

What enzymes are involved in starch digestion in the small intestine?

A

In the small intestine, pancreatic α-amylase and enterocyte brush border enzymes (maltase and sucrase) are involved in starch digestion.

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11
Q

What is the end product of CHO digestion?

A

The progressive hydrolysis of CHO leads to the conversion of carbohydrates into glucose molecules.

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12
Q

How are glucose molecules absorbed into enterocytes?

A

Glucose molecules are absorbed into enterocytes via the sodium-glucose co-transporter on the apical surface of the enterocytes (using 2 sodium ions and 1 glucose molecule).

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13
Q

How is glucose transported out of enterocytes into the bloodstream?

A

Glucose is transported out of enterocytes into the bloodstream using the GLUT2 transporter on the basolateral membrane.

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14
Q

What are fats or lipids?

A

Fats or lipids are macronutrients that provide a medium for the absorption of fat-soluble vitamins and play other important roles in the body.

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15
Q

Are fats generally soluble in water?

A

No, fats are generally not soluble in water.

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16
Q

Where does fat digestion commence?

A

Fat digestion commences in the oral cavity.

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17
Q

How does fat digestion occur in the oral cavity?

A

Fat digestion in the oral cavity involves mechanical digestion through mastication (chewing) and the formation of a bolus, as well as chemical digestion through the action of lingual lipase.

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18
Q

What is the role of lingual lipase in fat digestion?

A

Lingual lipase, secreted by the dispersed salivary glands of the tongue, is responsible for the hydrolysis of lipid triglycerides into fatty acids and diglycerides.

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19
Q

What are the products of fat hydrolysis in the oral cavity?

A

The products of fat hydrolysis in the oral cavity are fatty acids and diglycerides.

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20
Q

What enzymes are involved in fat digestion in the stomach?

A

In the stomach, lingual lipase and gastric lipase are involved in fat digestion.

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21
Q

What is the role of lingual lipase in the stomach?

A

Lingual lipase hydrolyzes triglycerides to free fatty acids and partial glyceride in the stomach.

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22
Q

Which cells secrete gastric lipase in the stomach?

A

Gastric lipase is secreted by chief cells, which are exocrine cells in the stomach.

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23
Q

What are the products of fat hydrolysis by gastric lipase?

A

Gastric lipase converts triglycerides into diglycerides and fatty acids.

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24
Q

How do stomach contractions assist in fat digestion?

A

The contractions of the stomach help disperse fat molecules, aiding in the digestion process.

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25
Q

What is the function of diglycerides in fat digestion?

A

Diglycerides derived during fat digestion in the stomach act as emulsifiers, further aiding in the breakdown of fats.

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26
Q

What are the component parts of triglycerides after hydrolysis in the stomach?

A

Triglycerides are hydrolyzed into fatty acid and glycerol molecules by lipase enzymes.

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27
Q

What happens to gastric contents in the duodenum during fat digestion?

A

In the duodenum, gastric contents are emulsified by bile, leading to the conversion of larger fat globules into small droplets.

28
Q

How do small fat droplets pass through the microvilli?

A

Small fat droplets, arranged as micelles, pass through the microvilli in the small intestine.

29
Q

How do fatty acids and monoglyceride enter the enterocyte?

A

Fatty acids and monoglyceride cross the apical membrane of microvilli through passive diffusion and lipid protein transporter mechanisms, such as the fatty acid transporter protein.

30
Q

What happens to fatty acids and monoglyceride inside the enterocyte?

A

Inside the enterocyte, fatty acids and monoglyceride are transported into the endoplasmic reticulum and Golgi, where they are used to synthesize triglyceride.

31
Q

What are chylomicrons?

A

Chylomicrons are particles formed in the enterocyte, containing triglyceride, cholesterol, and lipoproteins. They transport dietary fats through the lymphatic system.

32
Q

How are chylomicrons transported out of the enterocyte?

A

Chylomicrons are subject to exocytosis via Golgi exocytotic vesicles, which transport them to the basolateral aspect of the enterocyte.

33
Q

Where do chylomicrons enter after exocytosis?

A

Chylomicrons are transported into the lacteal, which are lymphatic vessels of the small intestine.

34
Q

What are proteins composed of?

A

Proteins are large molecules composed of amino acids joined together by peptide bonds, forming chains of polypeptides.

35
Q

What is the process of breaking down proteins called?

A

The process of breaking down proteins is called proteolysis.

36
Q

What are proteases?

A

Proteases are enzymes that catalyze the breakdown of proteins during digestion.

37
Q

Are dietary proteins typically absorbed as they are?

A

No, with few exceptions, dietary proteins are not absorbed as they are. They need to be digested into smaller peptides.

38
Q

What is the role of pepsinogen in protein digestion?

A

Pepsinogen is released by chief cells in the stomach. In the acidic environment created by hydrochloric acid (HCl) released by parietal cells, pepsinogen is converted to its active form called pepsin, which functions in an environment with a pH of 2-3.

39
Q

What is the pH range in which pepsin is active?

A

Pepsin is active in an acidic environment with a pH of 2-3.

40
Q

What are the two primary pancreatic proteases?

A

The two primary pancreatic proteases are trypsin and chymotrypsin.

41
Q

In what form are trypsin and chymotrypsin synthesized and packaged?

A

Trypsin and chymotrypsin are synthesized and packaged within secretory vesicles as inactive proenzymes: trypsinogen and chymotrypsinogen, respectively.

42
Q

How are the proenzymes trypsinogen and chymotrypsinogen activated?

A

The proenzymes trypsinogen and chymotrypsinogen are activated by enterokinase, which is secreted by the mucosal membrane of the duodenum.

43
Q

What are the active forms of trypsin and chymotrypsin?

A

The activation of trypsinogen and chymotrypsinogen results in the formation of trypsin and chymotrypsin, respectively.

44
Q

What is the role of trypsin and chymotrypsin in protein digestion?

A

Trypsin and chymotrypsin break peptide bonds within the process of protein digestion, aiding in the breakdown of proteins into smaller peptides.

45
Q

What is the dependency for the absorption of amino acids?

A

The absorption of amino acids is dependent on the electrochemical gradient of Na+ across the epithelium.

46
Q

What happens when transporters bind amino acids during absorption?

A

The transporters bind amino acids only after binding sodium. This binding leads to a conformational change in the transporter.

47
Q

What occurs after the conformational change of the transporter during amino acid absorption?

A

The fully loaded transporter undergoes a conformational change that deposits both Na+ and the amino acid into the cytoplasm. The transporter then re-orients back to its original form.

48
Q

How are amino acids transported out of the enterocyte into the blood?

A

The basolateral membrane of the enterocyte contains additional transporters that export amino acids from the cell into the blood. Importantly, these transporters are not dependent on sodium gradients.

49
Q

What is the key role of bile in digestion?

A

Bile plays a key role in the digestion and absorption of fats from the small intestine.

50
Q

What is the function of bile salts in fat digestion?

A

Bile salts emulsify fats, breaking them down into smaller droplets, which enhances their digestion by pancreatic lipase.

51
Q

How do bile salts aid in the absorption of fats?

A

Bile salts solubilize fat digestion products, forming aggregations that can be easily absorbed across the mucosa.

52
Q

What waste products are eliminated through bile?

A

Bile eliminates waste products, including bile pigment bilirubin, which is derived from the breakdown of heme in red blood cells. Stercobilin, a breakdown product of bilirubin, gives feces its brown color.

53
Q

What other substances are present in bile?

A

Bile also contains cholesterol and can help in the elimination of certain drugs from the body.

54
Q

What are micronutrients?

A

Micronutrients are nutrients that are required in small amounts, including vitamins, minerals, and trace elements.

55
Q

Do micronutrients play an important role in the body?

A

Yes, even though they are required in small amounts, micronutrients are not considered unimportant. They have essential roles in various metabolic pathways and cellular mechanisms.

56
Q

What are some examples of micronutrients?

A

Examples of micronutrients include vitamins (such as vitamin C and vitamin D), minerals (such as calcium and iron), and trace elements (such as zinc and selenium).

57
Q

How can we ensure adequate intake of micronutrients?

A

Eating a balanced diet that includes a variety of foods is the best way to ensure adequate intake of micronutrients.

58
Q

What can happen if there is an inadequate or excessive intake of micronutrients?

A

: Inadequate or excessive intakes of micronutrients can have an impact on health and may lead to deficiencies or toxicities.

59
Q

Can the requirements for micronutrients vary based on age and health status?

A

Yes, the requirements for micronutrients can be influenced by factors such as age and health status. Different life stages and health conditions may have specific micronutrient needs.

60
Q

Where does the absorption of micronutrients mostly occur?

A

The absorption of micronutrients mostly occurs within the small intestine.

61
Q

What are the most common micronutrients?

A

The most common micronutrients are vitamins and minerals, such as iron, zinc, and vitamins A, D, E, and K.

62
Q

Where does the absorption of micronutrients primarily occur?

A

The absorption of micronutrients primarily occurs in the small intestine.

63
Q

What are water-soluble vitamins?

A

Water-soluble vitamins are those that are dissolved in water and can be readily absorbed into tissues for immediate use. Examples include the B-vitamins.

64
Q

What are fat-soluble vitamins?

A

Fat-soluble vitamins are dissolved in fat. Excess fat-soluble vitamins are stored in the liver and adipose tissues for future use. Examples include vitamins A, D, E, and K.

65
Q

How can pathology or surgery affecting the small intestine impact the absorption of micronutrients?

A

Pathology or surgery involving the small intestine can have a functional impact on the absorption of micronutrients. It can disrupt the normal absorption process, leading to potential deficiencies or malabsorption of vitamins and minerals.

NME (49 decks)

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