5. Digestion Flashcards

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1
Q

What is digestion

A

The process by which the larger molecules in the food are hydrolysed into smaller more soluble molecules that can be absorbed by the body

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2
Q

What is the function of the salivary glands

A

Secrete saliva - a mixture of amylase and water and ions
To digest starch into maltose

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3
Q

What is the function of the pancrease

A

Produces pancreatic juice - a mixture of enzymes in an alkaline solution, including amylase for release into small intestine

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4
Q

What is the function of the small intestine

A

Main area of secretion of digestive enzymes and absorption of products

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5
Q

What happens to carbohydrates during starch digestion

A

Carbohydrase breaks starch up into maltose and then glucose

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6
Q

What happens in starch digestion in the mouth

A

Begins in the mouth
Salivary glands secret saliva - contains amylase
Catalyses the hydrolysis of starch into maltose

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7
Q

What happens in starch digestion in the small intestine lumen

A

Duodenum
Pancreatic amylase secreted from the pancreas
Catalyses the hydrolysis of any undigested starch molecules into maltose

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8
Q

What happens to starch digestion on the small intestine membrane

A

Maltase in the cell membrane of small intestine cells hydrolyse maltose to glucose which is small enough to absorb through the small intestine

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9
Q

How are proteins digestied

A

Peptidase enzymes hydrolyse proteins into amino acids. Starts in the stomach and then the small intestine

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10
Q

What do exopeptidases do

A

Hydrolyse peptide bonds between the terminal amino acids to release dipeptides or single amino acids.
Some are produced by the pancreas and some by the small intestine wall

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11
Q

What do endopeptidases do

A

Hydolyse peptide bonds between amino acids in the central region of the protein forming smaller peptide molecules
Enzymes produced by stomach and pancreas

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12
Q

What do dipeptidases do

A

Hydolyse peptide bonds holding two amino acids.
Enzymes are membrane bound on the small intestine membrane

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13
Q

What happens in lipid digestion

A

Starts at duodenum and ends in ileum
Hydrolysed by lipase enzymes produced in pancreas
Hydolyses ester bonds in triglycerides to form fatty acids and glycerol and sometimes monoglycerides

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14
Q

What is the process of lipid digestion

A

Lipids combine with bile salts produced by the liver = emulsification
Increases surface area so digestion of lipase increases

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15
Q

What is co-transport

A

Amino acids and glucose are absorbed with Na+ ions.
Specific co-transport carrier proteins take both molecules into the cytoplasm together.
Na+ and glucose have a complementary shape to the binding site on the protein.
Sodium ions then activley pumped through into blood

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16
Q

How can co-transport occur

A

Pumping sodium ions into the blood maintains a low conc of sodium ions in the epithelial cells
Provides a conc gradient fow continuous absorption

17
Q

How are amino acids absorbed

A

Co-transport with sodium ions

18
Q

How is glucose absorbed into the blood

A

Co-transport with sodium ions

19
Q

How are lipids absorbed

A

Fatty acids, glycerol and monoglycerides stay associated with bile salts
All come together to form a droplet called a micelle
Micelles are soluble in water and transport their contents to the epithelial cells.
Micelles break down at the gut cell and release the content into the cell.
Glycerol and fatty acids are non-polar so simply diffuse across into the cell
Triglycerides reform inside the cell forming chylomicrons (attached to a proetin by the golgi body)
Chylomicrons transported out of the cell by exocytosis
First absorbed into a lacteal but then the blood