Digestion

Question 1

What is digestion?

Answer 1

The process which large (insoluble) molecules are hydrolysed by enzymes into small, soluble molecules which can be absorbed

Question 2

Which organs are involved in digestion?

Answer 2

Mouth
Salivary glands
Oesphagus
Stomach
Liver
Gall bladder
Pancreas
Small intestine (ileum)
Large intestine
Rectum
Anus

Question 3

What is the function of the mouth?

Answer 3

Food is ingested and teeth physically/mechanically digest the food

Question 4

What is the function of the salivary glands?

Answer 4

Produces salivary amylase which begins the chemical digestion of starch

Question 5

What is the function of the oesophagus?

Answer 5

Tube connecting the mouth to the stomach

Question 6

What’s the function of the stomach?

Answer 6

A muscular bag that churns food (mechanical/physical break down) adds acid and pepsin to start the digestion process

Question 7

What’s the function of the ileum?

Answer 7

A long tube with villi, site of final stages of digestion and absorption of monomers

Question 8

What’s the function of the liver?

Answer 8

Produces bile (for emulsification of fats) that is stored in the gall bladder

Question 9

What’s the function of the pancreas?

Answer 9

Produces many digestive enzymes which are released into the duodenum

Question 10

What is the function of the large intestine?

Answer 10

Where water and ions are absorbed

Question 11

What is the function of the rectum?

Answer 11

Storage of faeces before being expelled from the anus

Question 12

What is ingestion?

Answer 12

When food is taken in through the mouth

Question 13

What is absorption?

Answer 13

Where small soluble molecules are absorbed through the ileum into the blood

Question 14

What is egestion?

Answer 14

Any food that can’t be digested is eliminated from the body (eg, cellulose, aka fibre -plant cell walls)

Question 15

What are proteins broken down into?

Answer 15

Protestases hydrolyse the peptide bonds to form AMINO ACIDs

Question 16

What are the different types of peptidases?

Answer 16

Endopeptidase
Exopeptidase
Dipeptidase

Question 17

What is the purpose of ENDOpeptidases?

Answer 17

Work in the stomach along the chain to produce MULTIPLE SHORTER POLYPEPTIDES

Question 18

What is the purpose of EXOpeptidases?

Answer 18

Removal terminal (ends of chain) amino acids to form DIPEPTIDES AND AMINO ACIDS

Question 19

What is the purpose of DIpeptidases?

Answer 19

They are membrane bound in the duodenum and ileum and the hydrolyse the peptide bonds between dipeptides to produce amino acids which can be absorbed via contransport

Question 20

How are carbohydrates broken down into monosaccharides?
Give an example

Answer 20

Starch is hydrolysed by amylase to form Maltose
Maltose is hydrolysed by Maltase to form alpha glucose - which can be absorbed

Question 21

Which enzymes hydrolysed lactose?

Answer 21

LactASE

Question 22

Which enzyme hydrolysed sucrose?

Answer 22

SucrASE

Question 23

How are lipids digested?

Answer 23

Lipases hydrolyse the ester bond in triglycerides to form glycerol, fatty acid and monoglycerides

Question 24

What is peristalsis?

Answer 24

Waves of muscular contractions which move food boluses into the stomach

Question 25

Give an example of an endopeptidase?

Answer 25

Pepsin Tripsin

Question 26

What is the purpose of bile?

Answer 26

Emulsifies large lipid droplets into micelles to increase its surface area for lipases to work on

Question 27

How is the ileum adapted to increase the efficiency of absorption?

Answer 27

- Lining of ileum folded into villi - increase the surface area - Villi have thin walls for short diffusion pathway - Epithelial cells have micro Lili - Inside is a rich blood supply which can carry away absorbed molecules to maintain the concentration gradient - Villi waft/move so we can ,is food to maintain the concentration gardient

Question 28

How are monosaccharides and amino acids absorbed into the blood?

Answer 28

Co-transport

Question 29

Describe the process of co-transport?

Answer 29

Na+/K+ pump is used on the basal membrane of epithelial cells Na+ actively pumped out of epithelial cells into blood by active transport Simultaneous K+ transported into epithelial cells This creates a low Na+ ion concentration in epithelial cells Low concentration of glucose in the lumen of the intestine compared to epithelial cell (much smaller) Na+ diffuses down its concentration gradient by facilitated diffusion taking glucose with it This provides energy and drives transport of glucose into the cell with it - against its concent gradient by co-transport The glucose then moves out of epithelial cells into the blood by facilitated diffusion (using a carrier protein)

Question 30

Lipids are digested by which two chemicals?

Answer 30

Lipase Bile salts

Question 31

Where are bile salts produced?

Answer 31

In the liver

Question 32

What is the purpose of bile salts?

Answer 32

Emulsify lipids to form tiny droplets called micelles

Question 33

What is the purpose of micelles?

Answer 33

Increase the surface area of lipids for lipase to act on

Question 34

What is a micelle?

Answer 34

A vesicle that contain fatty acids, glycerol, monoglycerides and bile salts

Question 35

How do micelles aid lipid absorption?

Answer 35

Make fatty acids more soluble in water (allows simple diffusion - lipid soluble molecules ) They carry the fatty acids to epithelial cells of the ileum They help to maintain a higher concentration of fatty acids compared to the epithelial cells of the ileum

Question 36

What happens to fatty acids (micelles) once they enter cells?

Answer 36

Fatty acids and monoglycerides are modified into triglycerides inside the endoplasmic reticulum and Golgi body If a protein is added to the lipid it makes chylomicron

Question 37

How do modified lipid leave the epithelial cells?

Answer 37

Vesicle containing the chylomicron are released and move towards the cell membrane They are released by exocytosis They are absorbed/enter the lacteal (lymphatic system)