ANFF topic 1 part 3

Question 1

What are the steps in obtaining nutrition and energy from food?

Answer 1

• ingestion
• digestion
• absorption
• elimination

Question 2

What is ingestion?

Answer 2

• process of taking in food through the mouth

Question 3

Define digestion.

Answer 3

• the mechanical and chemical break down of food into small organic fragments that is a suitable size for absorption across the digestive epithelium
• large, complex molecules of proteins, polysaccharides and lipids must be reduced to simpler particles

Question 4

What digestion happens in the mouth?

Answer 4

• beginning of digestion

- the salivary enzyme amylase begins the breakdown of food starches into maltose (disaccharide)

Question 5

What occurs in the oesophagus?

Answer 5

• no significant digestion of carbs take place
• no digestive enzymes present
• produce mucous for lubrication

Question 6

What do monosaccharides make up the disaccharides?

Answer 6

• maltose –> glucose + glucose
• sucrose –> glucose + fructose
• lactose –> glucose + galactose

Question 7

What enzymes are present in the small intestinal wall?

Answer 7

• maltase
• sucrase
• lactase

Question 8

Where is amylase from and what does it break down?

Answer 8

• from pancreatic juice

- breakdown of starch and glycogen into maltose

Question 9

What happens to glucose after it has been broken down?

Answer 9

• absorbed and can be used in metabolic pathways to harness energy
• transported through the intestinal epithelium into the bloodstream to be transported to the different cells in the body

Question 10

What takes place in the stomach?

Answer 10

• protein digestion

Question 11

What breaks down protein in the stomach?

Answer 11

• pepsin

- protein to peptides

Question 12

What enzymes in the duodenum break down peptides into smaller peptides?

Answer 12

• trypsin
• elastase
• chymotrypsin

Question 13

What is pepsin produced by?

Answer 13

• stomach chief cells

Question 14

What enzymes break down proteins into peptides?

Answer 14

• pepsin
• trypsin
• elastase
• chymotrypsin

Question 15

What enzymes break down peptides into smaller peptides and amino acids?

Answer 15

• carboxypeptidase
• aminopeptidase
• dipeptidase

Question 16

Where does lipid digestion begin?

Answer 16

• in the stomach

Question 17

What enzymes break down lipid in the stomach?

Answer 17

• lingual lipase

- gastric lipase

Question 18

Where does the bulk of lipid digestion occur?

Answer 18

• in the duodenum

Question 19

What triggers the release of bile?

Answer 19

• when the chyme enters the duodenum, hormonal responses trigger the release of bile

Question 20

Define emulsification.

Answer 20

• Large lipid globules are broken down into several small lipid globules

Question 21

What is the function of bile?

Answer 21

• digestion of lipids by emulsification

Question 22

What happens when there is water around lipids?

Answer 22

• hydrophobic substances

- they will aggregate to form globules to minimize exposure to water

Question 23

How does bile emulsify large lipid globules?

Answer 23

• bile contains bile salts which are amphipathic

- hydrophilic side of bile salts interact with water on one side and the hydrophobic side interacts with lipids

Question 24

Why is emulsification important for digestion of lipids?

Answer 24

• if there is no emulsification, the lipid in the chyme would still be in the form of large globules, there is very little surface area of the lipids for the lipase to act on
• emulsification of lipid globules would increase the available surface area of lipids and pancreatic lipases can then act on the lipids more efficiently and digest

Question 25

How are lipids absorbed in the small intestine?

Answer 25

• bile salts will surround long-chain fatty acids and monoglycerides forming tiny spheres (micelles)
• micelles move into the small intestine absorptive cells where the long-chain fatty acids and monoglycerides diffuse out of the micelles into the absorptive cells leaving the micelles behind in the chyme
• these large spheres are called chylomicrons
• chylomicrons contain triglycerides, cholesterol, and other lipids and they have proteins on their surface
• together, they enable the chylomicron to move in an aqueous environment without exposing lipids to water
• chylomicrons leave the absorptive cells via exocytosis
• chylomicrons enter the lymphatic vessels then enter the blood in the subclavian vein

Question 26

How are fat-soluble vitamins absorbed?

Answer 26

• same as lipids

Question 27

How are water-soluble vitamins absorbed?

Answer 27

• directly absorbed into the bloodstream from the intestine

Question 28

What happens to undigested food?

Answer 28

• enters the colon where water is reabsorbed

Question 29

What happens in the colon?

Answer 29

• colon has microflora called “intestinal flora” that aid in the digestion process
• semi-solid waste is moved through the colon by peristaltic movements of the muscle

Question 30

Where is undigested food material stored?

Answer 30

• the rectum
• the rectum expands in response to storage of fecal matter
• triggers neural signals required to set up the urge to eliminate

Question 31

How is waste eliminated from the body?

Answer 31

• through the anus

- peristaltic movements of the rectum