Topic 22: Digestion

Question 1

How do heterotrophs get food?

Answer 1

must ingest food - cannot fix carbon

Question 2

What are the 4 stages of food processing?

Answer 2

ingestion
digestion
absorption
elimination

Question 3

What happens during ingestion?

Answer 3

food enters digestive cavity

Question 4

What happens during digestion?

Answer 4

macromolecules -> monomers that can be absorbed

mechanical, chemical

Question 5

What happens during absorption?

Answer 5

cells take up small molecules?

Question 6

What happens during elimination?

Answer 6

undigested material passed out of digestive system

Question 7

What are the 2 methods of digestion?

Answer 7

intracellular digestion

extracellular digestion

Question 8

What happens during intracellular digestion?

Answer 8

food vacuoles fuse with lysosomes

Question 9

What happens during extracellular digestion?

Answer 9

digestion in specialized extracellular compartments

Question 10

What is the alimentary canal?

Answer 10

the complete digestive tract continuous with the outside

Question 11

What do the accessory glands do?

Answer 11

secrete digestive juices via ducts (exocrine)
salivary glands
pancreas
liver
gall bladder

Question 12

What is peristalsis?

Answer 12

waves of contractions in smooth muscle - moves food

Question 13

What are sphincters? What do they do?

Answer 13

ring-like, muscular valves (circular muscles)

regulate passage between compartments

Question 14

What happens before ingestion?

Answer 14

digestive process triggered in NS

stimulation of salivary glands

Question 15

What controls mechanical digestion? Example?

Answer 15

done by teeth

chewing

Question 16

What assists in chemical digestion?

Answer 16

salivary amylase

Question 17

What does starch and glycogen break down into during digestion?

Answer 17

smaller polysaccharides, maltose

Question 18

What does mucus contain?

Answer 18

contains mucins

slipper glycoproteins

Question 19

What is the function of the tongue? What does it form?

Answer 19

moves food

forms bolus - ball of food

Question 20

What is the pharynx?

Answer 20

passage to digestive and respiratory systems

Question 21

Sequence swallowing

Answer 21

bolus -> esophageal sphincter -> esophagus

Question 22

What is the esophagus?

Answer 22

muscular tube from pharynx to stomach

Question 23

Where is the cardiac sphincter and what is it controlled by?

Answer 23

junction with stomach

controlled by smooth muscle ring

Question 24

Why does heartburn occur?

Answer 24

when cardiac sphincter doesn’t always function properly

-> gastric juices move up into esphagus

Question 25

What are some characteristics of the stomach?

Answer 25

highly elastic about 2L capacity can store meal - don't need to eat constantly acidic - lining replaced about every 3 days

Question 26

What is the stomach lining made of?

Answer 26

many pits - gastric glands | contain 3 cell types that produce and secrete gastric juices

Question 27

What do mucous cells do?

Answer 27

secrete mucus

Question 28

What do chief cells do?

Answer 28

secrete pepsinogen - inactive precursor of pepsin

Question 29

What do parietal cells do?

Answer 29

pump H+ into lumen, Cl- diffuses out -> HCl

Question 30

What is the function of HCl?

Answer 30

pH of stomach remains at about 2 antimicrobial denatures proteins - easier to absorb low pH: pepsinogen -> pepsin: main digestive enzyme endopeptidase: protein -> smaller polypeptides

Question 31

What develops in the stomach that leaves?

Answer 31

chyme

Question 32

What is the consistency of chyme? pH? What is it a mixture of? SEQ pathway of chyme

Answer 32

``` consistency of thick soup pH about 2 mixture of: - partially digestive carbs - small polypeptides - undigested material stomach -> pyloric sphincter -> small intestine ```

Question 33

How long is the small intestine?

Answer 33

about 6m long

Question 34

What are the 3 divisions of the small intestines?

Answer 34

duodenum jujunium Ileum

Question 35

How do polysaccharides break down?

Answer 35

poly,disaccharides -> monosaccharides

Question 36

Where are carbohydrates digested?

Answer 36

oral cavity - salivary amylase: large polysaccharides -> small polysaccharides small intestines - pancreatic amylase: small polysacchs -> disacchs; disaccharidases: disacchs -> monosacchs

Question 37

polypeptides are broken down into ...

Answer 37

amnio acids

Question 38

What parts of the digestive system are proteins broken down in?

Answer 38

stomach | small intestines

Question 39

How are proteins broken down in the stomach?

Answer 39

pepsin -> small polypeps

Question 40

How are proteins broken down in the small intestines?

Answer 40

pancreatic trypsin -> smaller polypeps | peptidases -> amino acids

Question 41

Where in the digestive systems are nucleic acids broken down?

Answer 41

small intestines

Question 42

What happens when nucleic acids are broken down in the small intestines?

Answer 42

pancreatic nucleases -> nucleotides nucleotidases -> nucleosides nucleosidases and phosphatases -> nitrogenous bases, sugars, phosphates

Question 43

How are lipids broken down?

Answer 43

triglycerides -> glycerol, fatty acids, monoglycerides

Question 44

What is the problem with breaking down lipids in the digestive system?

Answer 44

enzymes are water soluble while lipids are hydrophobic

Question 45

What breaks up the lipids into smaller pieces?

Answer 45

bile salts from liver emulsify the fats | -> increase SA so enzymes can break them down

Question 46

What produces bile salts and where do they go?

Answer 46

liver produces bile salts and sends it to gall bladder for storage

Question 47

Where does lipid digestion occur?

Answer 47

in small intestines

Question 48

What happens to lipids in the small intestines?

Answer 48

pancreatic lipases | -> glycerol, fatty acids, monoglycerides

Question 49

How does absorption occur in the small intestines?

Answer 49

villi on the folds of the small intestines have microvilli

Question 50

SEQ nutrient absorption

Answer 50

nutrients in lumen of SI -> villi -> blood capillaries -> heaptic portal vein -> liver

Question 51

How does lipid apsorption occur?

Answer 51

free fatty acids, monoglycerides - diffusion -> form triglycerides -> packaged as water soluble chylomicrons -> enter lacteal -> lymph -> blood

Question 52

What is the entry from the small intestine to the large intestine regulated by?

Answer 52

the ilecocecal valve

Question 53

What are the 4 divisions of the large intestine?

Answer 53

ascending, transverse, descending, sigmoid

Question 54

What happens during diarrhea in the small intestine?

Answer 54

lining irritated -> not enough water recovery

Question 55

What happens during constipation?

Answer 55

feces move too slowly -> too much water recovery

Question 56

What do bacteria do in large intestines?

Answer 56

beneficial bacteria present produce vitamins, outcompete pathogens

Question 57

Why are feces eliminated?

Answer 57

they are undigestible material, undigested nutrients

Question 58

What is feces made of?

Answer 58

75% water, 25% solid

Question 59

What is the function of the liver?

Answer 59

``` hepatic portal vein transports blood to liver excess glucose removed -> glycogen nutrients converted -synthesize proteins -excess calories stored as fat modify, detoxify - alcohol, other drugs ```