6.1 Digestion

Question 1

esophagus

Answer 1

hollow tube connecting to the oral cavity (that is separated from the trachea by the epliglottis)
- food is mixed with saliva (salivary amylase) and is then moved in a bolus via action of peristalsis

Question 2

stomach

Answer 2

temporary storage tank where food is mixed by churning (physical) and protein digestion begins - lined by gastric pits that release digestive juices which create an acidic environment

Question 3

small intestines

Answer 3

long, highly folded tube where usable food substances (nutrients) are absorbed - consisting of duodenum, jejunum, ileum - food is broken down by enzymes

Question 4

large intestines

Answer 4

final section of alimentary canal - water and dissolved minerals (ions) are absorbed

Question 5

saliva gland

Answer 5

release saliva to moisten food (it contains amylase enzyme) to initiate starch breakdown
salivary glands include parotid gland, submandibular gland, sublingual gland (collection of different glands)

Question 6

pancreas

Answer 6

produces enzymes that are released into small intestine via duodenum (very first bit of small intestines and secretes hormones (i.e. insulin, glucagon,) which regulate blood sugar concentrations

Question 7

liver

Answer 7

taking raw materials absorbed by small intestines and used to make key chemicals
roles include detoxification, storage, metabolism, bile production, hemaglobin breakdown

Question 8

gallbladder

Answer 8

stores biles produced by the liver (bile salts are used to emulsify fats)
bile is released into small intestines via common bile duct

Question 9

what is peristalsis

Answer 9

muscle contractions that move food through the digestive tract - contractions behind the food, relaxations before it - uses radial muscles (rings of muscles circular and longitudinal muscles)

Question 10

where does mechanical digestion of food occur

Answer 10

chewing (mouth - food is broken down by grinding action of the teeth- tongue moves food t back of the throat as a bolus); churning (stomach - stomach wall contains muscles which physically squeeze and mix food with digestive juices)

Question 11

why is pepsin secreted as an inactive pepsinogen

Answer 11

pepsin is activated by hydrochloric acid and could kill many of the bacteria in food, however, if there is no HCl, the pepsin could self digest the proteins in the stomach wall

Question 12

what is chyme

Answer 12

chyme is the acidic and produced from the mixture of food with digestive juices - acidic white creamy paste!!!!

Question 13

what occurs during chemical digestion

Answer 13

large insoluble molecules are broken down into small soluble particles that can be absorbed by the small intestines

Question 14

what occurs in the duodenum

Answer 14

the acidic chyme (combo of food with digestive juices) is neutralized by the alkaline bile produced from the liver

Question 15

what is bile

Answer 15

a strong alkaline neutralizing chyme that lowers surface tension of large fat globules - making them break into tiny droplets -> emulsification

Question 16

pancreatic juices

Answer 16

secreted by the exocrine glands of the pancreas

Question 17

what does pancreatic juice contain

Answer 17

pancreatic amylase (catalyzes hydrolysis of amylose into maltose) -
water,
trypsin secreted inactive as trypsinogen (helps to digest proteins)
pancreatic lipase - hydrolysis of fats to fatty acids and glycerol
carboxypeptidase (protease) chymotrypsin - hydrogencarbonate ions (helps to neutralize stomach acid)

Question 18

segmentation

Answer 18

process by which all of the enzymes in the pancreatic juice combine with bile and chyme and are mixed together by a form of peristalsis

Question 19

what products are generally absorbed in the small intestines

Answer 19

amino acids, fatty acids, glycerol, monosaccharide sugars, vitamins, mineral ions

Question 20

describe the structure of the small intestines

Answer 20

serosa - outer coat
muscularis (composed of longitudinal muscle fibers and circular muscle fibers - particularly involved in peristalsis)
submucosa - composed of connective tissues, blood vessels, some glands
mucosa - series of finger-like villi which increase surface area of absorption
lumen

Question 21

important features of the small intestines

Answer 21

microvilli - foldings on the epithelial cell membranes further increase surface area
rich blood supply - dense capillary network rapidly absorbs and transports products of chemical digestion - flow of blood helps maintain concentration gradient
single layer epithelium - minimizes diffusion distance between lumen and blood
lacteals - absorbs lipids from the intestine into the lymphatic system
intestinal glands - exocrine pits (crypts of Lieberkuhm) release digestive juices
membrane proteins - faciltates transport of digested materials into epithelial cells

Question 22

what are the four methods of absorption

Answer 22

simple diffusion - occurs when molecules are small and hydrophobic
facilitated diffusion - for hydrophilic monomers to diffuse through protein channels
active transport
pinocytosis (draws in small droplets of liquid surrounded by a small seciton of the phospholipid membrane

Question 23

why is active transport necessary

Answer 23

it is necessary for when concentrations are lower in the lumen of the small intestines than in the blood so movement needs to occur against a concentration gradient - requires ATP - useful in the digestive system because diffusion would not be able to move small amounts against the concentration gradients once equilibrium has been established - therefore, there are lots of mitochondria that can synthesize ATP for this process

Question 24

what is dextrin

Answer 24

disaccharide formed from the digestion of amylopectin - containing 1-4 and 1-6 glycosidic linkages - it is larger a fragment that cannot be hydrolyzed and it remains

Question 25

what does starch breakdown into

Answer 25

maltose and dextrin

Question 26

why does blood from the digestive system always travel to the liver before returning to the circulatory system

Answer 26

the liver detoxifies and toxins that enter into the body via the digestive system could get into the blood - so the liver detoxifies it first - the liver can do so because it will constantly regrow

Question 27

salivary amylase vs pancreatic amylase

Answer 27

salivary amylase - begins to convert starch to maltose by hydrolysis of 1-4 bonds in amylopectin and amylose - WHEREAS
pancreatic amylase - continues conversion of starch to maltose by hydrolysis of 1-4 bonds in both amylose and amylopectin but the 1-6 bonds of amylopectin cannot be hydrolyzed and remain

Question 28

role of pancreas

Answer 28

1, exocrine glands release amylase
2. produces hormones insulin and glucagon which are released from endocrine glands

Question 29

how do insulin and glucagon regulate the glucose levels in the blood

Answer 29

insulin lowers blood glucose levels by increasing glucose uptake and storage as glycogen in the liver and adipose tissues (i.e. produced when blood sugar is high)
glucagon increases blood glucose levels by stimulating breakdown of stored glycogen into glucose (i.e. produced when blood sugar is low)

Question 30

three different types of peptidases

Answer 30

endopeptidase
exopeptidase
dipeptidase

Question 31

endopeptidase

Answer 31

hydrolyzes peptide bonds between amino acids in the central region of a peptide

Question 32

exopeptidase

Answer 32

hydrolyzes peptide bonds between the end amino acids in a peptide

Question 33

dipeptidase (membrane bound in ileum (last part of the small intestines)

Answer 33

hydrolyzes peptide bonds between two amino acids in a dipeptide

Question 34

why are there several types of peptidase

Answer 34

to increase surface area and rate of breakdown of polypeptide chains