unit 3, the digestive system and absorbtion

Question 1

what is digestion?

Answer 1

large biological molecules that are hydrolysed into smaller molecules that can be absorbed across cell membranes

Question 2

what enzymes hydrolyse carbohydrates?

Answer 2

-amylases
-membrande bound disacharides

Question 3

where does the process start and finish in the carbohydrates digestion?

Answer 3

starts at the mouth
goes to duodenum
finishes in ileum

Question 4

where is amylase produced and what does it hydrolyse?

Answer 4

-it is produced in the pancreas and the salivary glands
-it hydrolyses polysacharides into the diasacharide maltose by hydrolysing the gylcosidic bond

Question 5

what are the membrane bound diasacharides and what do they hydrolyse into?

Answer 5

sucrase hydrolyses sucrose into glucose and fructose
lactase hydrolyses lactose into glucose and galactose

Question 6

what are large polymers hydrolysed by?

Answer 6

-endopeptidases
-exopeptidases
-dipeptidases

Question 7

what are endopeptidases?

Answer 7

they are in the middle of the peptide chain, hydrolysing the amino acids

Question 8

what are exopeptidases?

Answer 8

they are at the end of the peptide chain, hydrolysing the bond at the end

Question 9

what are dipeptidases?

Answer 9

hydrolyse between 2 amino acids

Question 10

where does the process start and finish in the proteins digestion?

Answer 10

• begins in the stomach
  -to the duodenum
  -finishes in the ileum

Question 11

what are lipids sigested by?

Answer 11

-lipase
-action of bile salts

Question 12

where is lipase produced and what does it hydrolyse?

Answer 12

-produced in the pancreas
-hydrolyses ester bond in triglycerides, to form monogylcerides and fatty acids
-goes into duodenum

Question 13

where is bile salts produced and what do they do?

Answer 13

-produced in liver
-they are before lipase, and they emulsify lipids to form tiny droplets called micelles
-they increase the surface are for the lipase to act on
-goes into duodenum

Question 14

what is the physical reaction?

Answer 14

-lipids get coated in bile salts to create an emulsion
-many small droplets of lipids that are formed crete a large surface area to enable faster action of hydrolysis by lipase

Question 15

what is the chemical reaction?

Answer 15

lipase hydrolyses lipids into gylcerol, fatty acids and some monoglycerides

Question 16

what is a micelle and what do they do?

Answer 16

-water soluble vesicles formed from fatty acids, gylcerol, monogylcerides and bile salts
-they deliver fatty acids, gylcerol, monoglycerides to the epithelial cells of the ileum for absorbtion
-make lipids more soluble in water

Question 17

where does absorbtion occur?

Answer 17

cells lining the ileum

Question 18

what advanatgeous structures does the ileum have?

Answer 18

• covered in villi, to increase surface area
  -thin walls, for a shorter diffusion pathway
  -surrounded by capillaries to maintain concentration gradient.

Question 19

where does amino acid and monosacharide absorbtion start and end up?

Answer 19

from lumen to the gut

Question 20

when would facilitated diffusion be needed and when would a co transporter be needed for amino acid and monosacharide absorbtion?

Answer 20

facilitated diffusion- if there is higher concentration in the lumen than eptiehlial cell
co- transporter- higher cocentration in the epithelial cell than the lumen, this is usually the case

Question 21

in lipid absorbtion, what do micelles deliver and where to?

Answer 21

-micelles deliver fatty acid and monogylcerides to epithelial cell which they diffuse across due to their non polar nature leaving behind the micelles
-lipids can simple diffuse in phospholipid bilayer (as phospholipid is a lipid)

Question 22

what happens in the golgi apparatus and the endoplasmic reticulum?

Answer 22

triglycerides reform to be used in the body

Question 23

how are chylomicrons formed?

Answer 23

fatty globules combine with proteins to form chylomicrons, inside the golgi apparatus

Question 24

how are chlyomicrons transported away?

Answer 24

the lymph in the lacteal transports chylomicrons away from the intestine

Question 25

Describe how digested lipids are absorbed and then transported to the ileum and lymphatic system ? [5]

Answer 25

-micelles are made up of bile salts, monoglycerides an fatty acids
-micelles Carry fatty acids to the epithelial cells of the ileum
-fatty acids are absorbed into the cells of the ileum by simple diffusion
-triglycerides or chylomicrons are formed
-vesicles are removed by exocytosis

Question 26

Describe the importance of micelles in absorbing the lipids into the epithelial cells of the ileum. [3]

Answer 26

-micelles are made of fatty acids, monoglycerides, bile salts
-micelles make fatty acids more soluble in water
-micelles carry fatty acids to the epithelial cells of the ileum
-fatty acids are released by micelles and absorbed into the cell by simple diffusion

Question 27

When lipids are digested, they form smaller droplets and then micelles are formed. Explain the advantages of these two stages [3]

Answer 27

-lipid droplets increase surface area for lipase
-speeds up hydrolysis/digestion
-micelles bring fatty acids, monoglycerides and bile salts to the epithelial cell

Question 28

How is the Golgi apparatus involved in absorption of lipids? [3]

Answer 28

-modify, reform triglycerides
-combine proteins with triglycerides to form chylomicrons
-package into vesicles

Question 29

What is peristalsis?

Answer 29

The oesophagus is a muscular tube between the stomach and the mouth. Muscles contract in waves to push the food down. This is an involuntary reaction.