Chapter 6- Digestion And Absoprtion

Question 1

What prevents food being pushed back toward the mouth?

Answer 1

Constructions of circular muscles behind the food constricts the gut to prevent it from being pushed back towards the mouth

Question 2

What controls the contraction along the small intestine?

Answer 2

The enteric nervous system

Question 3

What is the main function of peristalsis ?

Answer 3

Is churning up of of the semi- digested food to mix it with enzymes and thus speed up the process of digestion

Question 4

What does the pancreas secrets?

Answer 4

enzymes into the lumen of the small intestine

Question 5

Pancreas contains 2 types of gland tissues- what’s the first?

Answer 5

1) small groups of cells secret the hormones insulin and glucagon into the blood

Question 6

Pancreas contains 2 types of gland tissues- what’s the second?

Answer 6

Secrets digestive enzymes into the gut in response to eating a meal

Question 7

Where are digestive enzymes synthesized?

Answer 7

In pancreatic gland cells on ribosomes on the rough endoplasmic reticulum- they are then processed in the Golgi apparatus and secreted by exocytosis

Question 8

Pancreatic juice contains enzymes that digest all 3 main types of macromolecules found in food what are they?

Answer 8

1) amylase to digest stArch
2) lipases to digest triglyceride, phospholipids
3) protease to digest proteins and prep tides

Question 9

What do enzymes do in digestion?

Answer 9

Enzymes digest most macromolecules in food into monomers in the small intestine

Question 10

What 4 reaction do enzymes carry out by the pancreas ?

Answer 10

By hydrolysis reactions:

1) starch is digested to maltose by amylase
2) phospholipids are digested to fatty acids and glycerol and phosphates by phospholipase
3) triglycerides are digested to fatty acids and glycerol or fatty acids and monoglycerides by lipase
4) proteins and polypeptides are digested to shorter peptides by protease

Question 11

What do villi do?

Answer 11

Increase the surface area of epithelium over which absorption is carried out

Question 12

What do villi absorb? (Overview)

Answer 12

Absorb monomers formed by digestion as well as mineral ions and vitamins

Question 13

What do villi absorb ? (6)

Answer 13

Absorb products of digestion of macromolecules in food

1) glucose, fructose, galactose- other monosaccharides
2) any of the twenty amino acids used to make proteins
3) fatty acids, monoglycerides and glycerol
4) bases from digestion of nucleotides
5) mineral ions such as calcium, potassium and sodium
6) vitamins such as ascorbic acids (vitamin c)

Question 14

How do nutrients get absorbed in the body?

Answer 14

Nutrients must pass from lumen of the small intestine to the capillaries of lacteals in the villi

Question 15

How do triglycerides get absorbed by simple diffusion? Step 1

Answer 15

1) must be digested before they can be absorbed- products of digestion are fatty acids and monoglycerides which can by absorbed into villus epithelium cells by simple diffusion

Question 16

How are fatty acids absorbed by facilitated transport? Step 2

Answer 16

2) fatty acids are also absorbed by facilitated diffusion as there are fatty acid transporters which are proteins in the membrane
3) once inside epithelium cells, fatty acids combine with monoglycerides to produce triglycerides which can’t diffuse back to lumen

Question 17

How are triglycerides get to exocytosis ? Step 3

Answer 17

1) triglycerides coalesce with cholesterol to form droplets which become coated in phospholipids and protein
2) these lipoprotein particles are released by exocytosis through the plasma membrane on the inner side of the villus epithelium cells- either enter lacteals and are carried away by lymph or enter the blood capillaries in the villi

Question 18

How does glucose pass through plasma membrane? Step 1

Answer 18

1) glucose cannot pass through plasma membrane by simple diffusion because it is polar and therefore hydrophilic
2) sodium-potassium pumps are used- they pump sodium ions by active transport from cytoplasm to villus and potassium ions in opposite direction
3) sodium glucose co transporter proteins in the micro villi transfer a sodium ion and a glucose molecule together from lumen to cytoplasm - this is facilitated diffusion and its passive
4) glucose channels allow glucose to move my facilitated diffusion from cytoplasm to villus

Question 19

What is peristalsis?

Answer 19

The contraction of circular and longitudinal muscle layers of the small intestine mixes the food with enzymes and moves it along the gut