6.1 digestion and absorption

Question 1

why do we need to eat?

Answer 1

to provide our bodies with chemical energy, which can be converted to ATP to power processes in the body

Question 2

what are essential nutrients and why do we need them?

Answer 2

they are nutrients not made by the animal and thus must be obtained from dietary sources

Question 3

in digestion, assimilation is the….

Answer 3

synthesis of molecules in the body from the absorbed small molecular nutrients

Question 4

label a diagram of the digestive system

Answer 4

-

Question 5

the alimentary canal consists of organs in which food ____________ ________.

Answer 5

passes through

Question 6

accessory organs are…

Answer 6

organs that aid in digestion but do not actually transfer food

Question 7

what is the function of the mouth?

Answer 7

• ingestion and chewing to break down food to smaller pieces -> incr SA:VR
• salivary amylase secreted for the digestion of starch to maltose
• alkaline medium of saliva for enzymatic activity

Question 8

what organs have peristalsis in the alimentary canal?

Answer 8

esophagus, stomach, small intestine, large intestine

Question 9

which part of the esophagus prevents acid and food reflux?

Answer 9

the sphincter muscle

Question 10

what is the function of the esophagus?

Answer 10

• transports food from mouth to stomach by peristalsis
• prevents food and acid reflux through the contraction of sphincter muscle

Question 11

which organ produces and secretes bile into the gall bladder?

Answer 11

the liver

Question 12

the gall bladder stores ______ which functions to aid digestion by…

Answer 12

• bile
• helping to emulsify fats for incr SA:VR for more efficient digestion by pancreatic lipase

Question 13

what is the function of the stomach? (3)

Answer 13

• secretes HCl and pepsinogen
• acidic medium kills pathogens in food
• pepsinogen converted to pepsin due to HCl and digests proteins into amino acids

Question 14

what does the pancreas do to aid digestion? (2)

Answer 14

• secretes digestive enzymes for proteins, fats and carbohydrates
• alkaline medium due to HCO3 ions for enzymatic activity

Question 15

what happens in the small intestine? (2)

Answer 15

• further digestion of food into monomers
• absorption of monomers facilitated by intestinal folds to incr SA

Question 16

what is the function of the small intestine? (3)

Answer 16

• digests food into monomers
• absorbs monomers across a 1-cell epithelium for quick movement into capillaries and lacteals
• intestinal folds e.g. villi, microvilli incr SA for absorption

Question 17

the three sections of the small intestine are…
1. duodenum
2. jejunum
3. ???

Answer 17

ileum

Question 18

what is the function of the large intestine? (3)

Answer 18

• absorption of water, vitamins and mineral ions
• house beneficial bacteria
• fermentation of undigested waste

Question 19

the part of the body involved in egestion of undigested food is…

Answer 19

the anus

Question 20

what part of the body stores undigested food?

Answer 20

the rectum

Question 21

why are enzymes needed in digestion?

Answer 21

they are biological catalysts, meaning they speed up the rate of reaction at body temperature by lowering the activation energy of the catabolic reactions

Question 22

intestinal enzymes are _______ ________ while pancreatic enzymes are _______________________ (ref to movement)

Answer 22

membrane-bound, carried along w food

Question 23

what is peristalsis?

Answer 23

the rhythmic contraction of antagonistic circular and longitudinal muscles

Question 24

how does peristalsis aid digestion

Answer 24

• it mixes chyme (semi-digested food) with enzymes
• it moves it along the gut

Question 25

how is food moved along the gut? (3)

Answer 25

- through peristalsis; the alternate contraction of the longitudinal and circular muscles - behind the food, the C muscle contracts and L muscle relaxes - gut wall constricts to become narrow and longer - prevents food from being pushed back while pushing food forward - at the food, the C muscle relaxes and L muscles contract - gut wall becomes wider and shorter - relaxation of C dilates gut wall and enables food to be pushed forward - contraction of L muscles shorten the distance to be travelled

Question 26

what takes place at the duodenum, jejunum and ileum respectively?

Answer 26

duodenum, jejunum: digestion ileum: absorption

Question 27

identify the small intestine tissue layers

Answer 27

-

Question 28

what is one feature of the serosa

Answer 28

it is a membrane coated with mucus to reduce friction with other organs

Question 29

in the small intestine, the large blood and lymph vessels and nerves are contained in the...

Answer 29

submucosa

Question 30

how does villi enhance the rate of absorption in the small intestine?

Answer 30

microvilli and villi increases the SA of the epithelium with numerous folds

Question 31

what are 6 features of villi (mnemonic: MRS LIM)

Answer 31

- microvilli - numerous folds increases SA - rich blood supply - rich supply of capillaries maintain conc gradient for diffusion - single layer epithelium - minimises diffusion dist btw lumen + blood - lacteals - absorbs lipids into lymphatic system - intestinal glands - exocrine pits release digestive juices - membrane proteins - facilitates transport of digested materials into epithelial cells

Question 32

why does the villus epithelium have a lot of mitochondria?

Answer 32

to provide ATP for AT

Question 33

fill in the list of membrane transport mechanisms: 1. ???? 2. facilitated diffusion 3. ??? 4. simple diffusion

Answer 33

1. secondary active transport (co-transport) 3. osmosis

Question 34

what monomers undergoes secondary AT?

Answer 34

glucose and amino acids

Question 35

how does glucose and amino acids enter the epithelial cell by secondary AT?

Answer 35

glucose and amino acids are co-transported across the epithelial membrane by the active translocation of Na+

Question 36

where do amino acids and glucose go and by what vessel after being absorbed into the bloodstream?

Answer 36

to the liver by the hepatic portal vein

Question 37

which monosaccharides enter by AT?

Answer 37

glucose and galatose

Question 38

which molecules enter by simple diffusion?

Answer 38

fatty acids, monoglycerides

Question 39

fructose enters by...

Answer 39

facilitated diffusion

Question 40

how are peptides absorbed?

Answer 40

co-transport by active translocation of H+

Question 41

fats enter the lacteal as...

Answer 41

chlyomicrons

Question 42

how does facilitated diffusion work?

Answer 42

- through channel proteins - channel proteins help hydrophilic food molecules pass through hydrophobic part of plasma membrane

Question 43

what enters the epithelial cell by facilitated diffusion?

Answer 43

fructose, vitamins and some minerals

Question 44

what molecules enter the epithelial cells by osmosis and what is this in response to?

Answer 44

water molecules, in response to the movement of ions and hydrophilic monomers

Question 45

what type of materials can enter epithelial cells by simple diffusion?

Answer 45

hydrophobic materials

Question 46

lipids enter the epithelial cell by _______

Answer 46

simple diffusion

Question 47

what is linear-chain starch called?

Answer 47

amylose

Question 48

what is branched starch called?

Answer 48

amylopectin

Question 49

where is starch digested?

Answer 49

mouth and small intestines

Question 50

what enzyme breaks down amylose and amylopectin?

Answer 50

amylase

Question 51

what is the products of digestion of amylose and amylopectin?

Answer 51

- amylose: maltose - amylopectin: limit dextrin

Question 52

where is maltose and limit dextrin digested?

Answer 52

at the membrane of microvilli

Question 53

what enzymes digest maltose and limit dextrin?

Answer 53

maltase and dextrinase

Question 54

maltase and dextrinase are ____________ (ref to position and mobility)

Answer 54

membrane-bound

Question 55

the hydrolysis of maltose and dextrin produce...

Answer 55

glucose monomers

Question 56

how is glucose absorbed? (6)

Answer 56

- glucose is co-transported across the epithelial membrane by secondary AT - uses energy from the movement of Na+ ions down their electrochemical gradient at the apical side of the epithelial cell to transport gluc against its concentration gradient - glucose is transported out of epithelial cell from basolateral side by facilitated diffusion to the blood in villus capillaries - blood from villus capillaries then drain into venules in submucosa layer - glucose in venules will be brought to liver via hepatic portal vein - excess is converted to glycogen for storage