Digestion 1

Question 1

what are the 3 parts of the small intestine?

Answer 1

duodenum
jejunum
ileum

Question 2

the villi of the small intestine is covered by? 2

Answer 2

mature cells - enterocytes
mucus secreting goblet cells

Question 3

what shape of cell are enterocytes?

Answer 3

columnar epithelial cells

Question 4

what are present on the luminal surface of enterocytes? why?

Answer 4

microvilli
to increase SA for absorption

Question 5

enterocytes are responsible for? 2

Answer 5

absorption
some digestion

Question 6

each villus of the small intestine contains? 2

Answer 6

a capillary network
a lacteal/lymph vessel

Question 7

do enterocytes and goblet cells have a short or long life?

Answer 7

short

Question 8

enterocytes are replaced by?

Answer 8

stem cells that migrate from the crypts (pits between vili)

Question 9

what is primary active transport?

Answer 9

movement is directly linked to energy use

Question 10

what is secondary active transport?

Answer 10

indirectly linked to an electrochemical gradient set up using energy

Question 11

what is receptor mediated endocytosis?

Answer 11

movement into the cell via a specific receptor

Question 12

what is pinocytosis?

Answer 12

‘cell drinking’
cell takes in extracellular fluid and soluble molecules

Question 13

what does an antiporter integral membrane protein do?

Answer 13

transports two different molecules/ions across a membrane in different directions

Question 14

what does a symporter integral membrane protein do?

Answer 14

transports two different molecules/ions across a membrane in the same direction

Question 15

what does a uniporter integral membrane protein do?

Answer 15

moves one type of molecules across a membrane in both directions

Question 16

what must happen to fat before digestion can occur?

Answer 16

emulsification

Question 17

what enzyme hydrolyses lipids in the stomach?

Answer 17

gastric lipase

Question 18

the triacylglycerides are hydrolised, the released fatty acids act as surfactants. what do surfactants do?

Answer 18

reduce surface tension

Question 19

what does the hormone cholecystokinin do? 2

Answer 19

stimulates the release of pancreatic digestive enzymes and bile into the small intestine

Question 20

lipases secreted by the pancreas are? 3

Answer 20

pancreatic lipase
carboxyl ester lipase
phospholipase A2

Question 21

how are fat globules exposure to enzymes maximised?

Answer 21

mixed with bile salts and pancreatic juice containing lipases to form an aqueous suspension of fatty droplets

Question 22

bile acids/salts are made in the ? from?

Answer 22

liver from cholesterol

Question 23

bile acids/salts are stored where?

Answer 23

gall bladder

Question 24

bile salts are composed of? 2

Answer 24

cholic acid
glycine or taurine

Question 25

what does a micelle do?

Answer 25

allows transport of lipids to the brush border of the enterocyte where they are absorbed by diffusion

Question 26

what is the structure of a micelle?

Answer 26

hydrophilic cholic acid face outward
hydrophobic glycine/taurine face inwards

bile salts emulsify fats by forming micelles

Question 27

inside the cell TAGs triglycerides are?

Answer 27

resynthesised at the ER by acyltransferases

Question 28

inside the cell phospholipids are? 2

Answer 28

acylated to form phosphatidic acid
converted to TAGs

Question 29

in the cell cholesterol is?

Answer 29

acylated to form cholesterol esters

Question 30

chylomicrons enter circulation through the lymph, they are formed from? 3

Answer 30

TAGs, cholesterol esters and apolipoprotein B

Question 31

understand the absorption of lipids

Question 32

where are chylomicrons assembled?

Answer 32

within enterocytes one the RER

Question 33

how do chylomicrons leave the enterocyte cells into the lymphatic system?

Answer 33

exocytosis

Question 34

disaccharides are broken down by what?

Answer 34

disaccharidases

Question 35

starch and glycogen require what to digest them? 2

Answer 35

salivary and pancreatic amylases

Question 36

how is glucose absorbed? 2

Answer 36

sodium potassium pump - Na+ out, K+ in using ATP

symport of glucose and Na+

Question 37

how is glucose and galactose absorbed? 3

Answer 37

sodium potassium pump - Na+ out, K+ in using ATP

symport of glucose and Na+

glucose leaves cell via uniporter into the blood

Question 38

how is fructose absorbed? 2

Answer 38

by GLUT5 sodium-independent facilitated diffusion into enterocyte

may be exported by GLUT2

Question 39

absorbed nutrients from the intestine go where? 2

Answer 39

portal vein (circulatory system)
thoracic duct (lymphatic system)