Digestion Absorption

Front 1

Methods of membrane transport in the Small Intestine (give examples)

Back 1

Simple diffusion: nutrients pass from high concentration to low (concentration gradient) between phospholipids in the membrane. Ex. hydrophobic nutrients like fatty acids and monoglycerides

Front 2

List the food macromolecules that are digested into monomers in the small intestine by the enzymes amylase, lipase, phospholipase and protease.

Back 2

Monomers: molecules that can be bonded to another identical molecules to form a polymer

Amylase: digests starch

Phospholipase: digests phospholipids into fatty acids, glycerol and phosphate

Lipase: digests triglycerides (fats) into fatty acids and glycerol

Protease: digests proteins and polypeptides into amino acids

Front 3

How does the Small Intestine increase surface area and why is it important?

Back 3

Small intestine (s.i.) is on average 6 meters; food takes hours to pass through and allows for digestion, There are folds on the inner surface which provide a larger surface area (S.A.) for absorption of nutrients. The s.i. also has small finger like projection coming out from the inside wall called villi. These are 0.15 - 1.5 mm long, there can be 40 of them per mm(2). Villi increase S.A. by factor of 10. Microvilli increase the surface area by a further factor of 20.

The length of the small intestine provides a longer time for digestion, and the added S.A. provides greater ability for absorption of digested molecules, giving nutrients (through the bloodstream) to cells around the body.

Front 4

Function of the Pancreas

Back 4

Pancreas contains 2 types of gland tissues that secrete hormones:

-Secrete insulin (lowers blood glucose)

-Secrete glucagon (raises blood glucose)

The pancreas secretes certain digestive enzymes in response to eating a meal. These are synthesized on ribosomes in the rough ER. About a liter of pancreatic juice is secreted per day into the lumen of the s.i.

Contains:

-Amylase - to digest starch

-Phospholipase - digests phospholipids to fatty acids, glycerol and phosphate

-Lipases - digest triglycerides (fats) to fatty acids and glycerol

-Proteases - digest proteins, and polypeptides into amino acids

Front 5

Function of each part of the digestive system

(1-4)

Back 5

1. Mouth (mechanical digestion): saliva moistens food to make a bolus for swallowing. Salivary amylase begins the digestion of starch.

2. Oesophagus: peristalsis pushes the bolus into the stomach.

3. Stomach: muscular contractions continue digestion. Acid kills bacteria. Pepsin begins digestion of proteins.

4. Duodenum: bile from liver and gallbladder neutralizes acids and emulsifies fats. Pancreatic amylase and lipase digest carbohydrates and fats. Trypsin digests polypeptides into amino acids. Duodenum is the upper half of the small intestine.

Front 6

Function of each part of the digestive system

(5-6 and extras)

Back 6

5. Ileum: lower half of the s.i. absorbs nutrients into the blood via villi.

6. Large intestine: water is reclaimed and returned to the blood leaving semi-sold faeces which is stored in the rectum.

Pancreas: secretes digestive enzymes.

Liver and gallbladder: creation (liver) storage, and secretion (gallbladder) of surfactants in bile to break up lipid droplets

Front 7

Digestion of Starch

Back 7

Digestion of starch is completed by enzymes in the membranes of the microvilli on the villus epithelial cells. Maltose and dextrinase digest maltose and dextrins into glucose.

-Starch contains 2 molecules, amylose and amylopectin. Both are polymer of alpha glucose linked by 1,4 bonds, but amylopectin contains some 1,6 bonds causing the molecule to be branched amylase breaks 1,4 bonds, digesting amylase into maltose. It cannot break 1,6 bonds, so the leftover pieces of amylopectin (which are undigested) are called dextrins.

In the membranes of the microvilli are proteins that cause the absorption of glucose produced by starch digestion. Blood carrying glucose and other products of digestion flows through capillaries to venules in the submucosa. Excess glucose can be absorbed by liver cells and convert to glycogen for storage.

Front 8

Define digestion and absorption

Back 8

Digestion: break down large food molecules into smaller molecules.

Absorption: the uptake of these molecules into the blood (to be used by cells around the body)

Front 9

Circular and longitudinal muscles in digestion

Back 9

Longitudinal muscle contraction expand the lumen in front of the food giving it space to move into

Circular muscle contractions behind food propel it forward

Together these functions are called peristalsis. Peristalsis also mixes food with enzymes and forces products of digestion into contract with the wall of the small intestine.

Front 10

Annotate a cross-section of a small intestine

Back 10

Front 11

What is the function of the mouth in digestion

Back 11

Digestion of starch

Front 12

Which parts the digestive system help the digest proteins?

Back 12

Stomach - Yes

Small Intestine - Yes

Large Intestine - No

Front 13

What enzymes can break 1,6 bonds? Which molecules have 1,6 bonds?

Back 13

Dextrinase/Dextrins

Front 14

What muscle types are involved in peristalsis?

Back 14

Longitudinal and Circular

Front 15

What layer of the small intestine is the arrow pointing to?

Back 15

Mucosa

Front 16

What enzymes are secreted by the pancreas?

Back 16

Amylase and lipases

Front 17

Protease digest what?

Back 17

Proteins

Front 18

Lipases digest triglycerides (fats) in what?

Back 18

Glycerol

Front 19

Mineral ions such as sodium, calcium and iron are absorbed into the villus of the small intestine by:

Back 19

Active Transport

Front 20

Monomers of the polysaccharides (carbohydrates) like glucose and fructose are absorbed into the villus of the small intestine by:

Back 20

Facilitated diffusion

Front 21

State the name and function of C and I

Back 21

C

Name: Stomach

Function: muscular contractions continue mechanical digestion. Acid kills bacteria. Pepsin begins digestion of proteins.

I

Name: Large Intestine

Function: Water is reclaimed and returned to the blood, leaving a semi-solid faeces. This is stored in the rectum.

Front 22

Explain how the small intestine increases surface area and why adequate surface area is important.

Back 22

The folds on the inner surface provide a larger surface area for increased absorption. Inside the small intestine (SI) there are lots of villi, little finger-like structures that absorb nutrients. These villi increase the surface area (SA) by a factor of 10. On these villi are microvilli, which increase the SA factor by 20. The larger the SA the more nutrients the SI can absorb. Without the villi and the microvilli inside the small intestine, it would only be able to absorb 30x less nutrients that it would with the villi and the microvilli.