Digestion

Question 1

What does amylase do?

Answer 1

Catalyses the conversion of starch into maltose
Involves the hydrolysis of the glycosidic bonds in starch

Question 2

Where is amylase produced?

Answer 2

Salivary glands
Or the pancreas

Question 3

What enzymes are attached to the cell membranes of epithelial cells lining the ileum?

Answer 3

Membrane- bound enzymes to break down maltose’s into glucose
Help to breakdown disaccharides e.g. sucrose, maltose, lactose into glucose, fructose and galactose
Involves hydrolysis of glycosidic bonds

Question 4

What does lipase do?

Answer 4

Catalyses the breakdown of lipids into monglycerides and fatty acids
Hydrolyses the ester bonds in triglycerides to form the monoglycerides and fatty acids

Question 5

Where are lipases made?

Answer 5

Pancreas

Question 6

Where are bile salts produced?

Answer 6

In the liver

Question 7

What do bile salts do?

Answer 7

Emulsify lipids
Cause the lipids to form smaller droplets (micelles)

Question 8

Why are small droplets better?

Answer 8

Several small droplets have a bigger surface area than a single large droplet - increases the surface area of lipid that’s available for lipase to work on

Question 9

What happens once the lipid is broken down?

Answer 9

The monoglycerides and fatty acids stick with the bile salts to form micelles

Question 10

What are proteins broken down into?

Answer 10

Peptidases

Question 11

What do proteases do?

Answer 11

Catalyse the conversion of proteins into amino acids by hydrolysing the peptide bonds between amino acids

Question 12

What do endopeptidases hydrolyse?

Answer 12

Peptide bonds between amino acids in the middle of a polymer chain creating shorter polypeptide chains

Question 13

2 examples of endopeptidases?

Answer 13

Trypsin and chemo trypsin- synthesised in the pancreas and secreted into the small intestine

Question 14

Where is pepsin released?

Answer 14

In the stomach by cells in the stomach lining

Question 15

What conditions does pepsin work in?

Answer 15

Acidic conditions- provided by HCL in the stomach

Question 16

What do exopeptidases do>

Answer 16

Hydrolsyes peptide bonds between amino acids at the end of a polymer chain

Question 17

What do membrane bound dipeptides do?

Answer 17

Hydrolyse peptide bonds between 2 amino acids

Question 18

Where does protein digestion start?

Answer 18

In the stomach then continues in the duodenum and is fully digested in the ileum

Question 19

How are lipids digested?

Answer 19

by lipase and the action of bile salts

Question 20

What is the physical digestion for lipid digestion?

Answer 20

Emulsification and micelle formation
Lipids are coated in bile salts to create an emulsion
Many small droplets of lipids provides a larger SA for faster hydrolysis by lipase

Question 21

What is the chemical part of lipid digestion?

Answer 21

Lipase hydrolyses lipids into glycerol and fatty acids

Question 22

What are micelles?

Answer 22

Water soluble vesicles formed of the fatty acids, glycerol, monoglycerides and bile salts

Question 23

What do micelles deliver to the epithelial cells of the ileum for absorption?

Answer 23

Fatty acids, glycerol and monoglycerides

Question 24

Where are the products of digestion absorbed?

Answer 24

Across the cells lining the ileum

Question 25

What is the ileum wall covered in?

Answer 25

Villi- they have thin walls surrounded by a network of capillaries and epithelial cells have even smaller microvilli

Question 26

How are monosaccharides and amino acids absorbed?

Answer 26

Co-transport

Question 27

How do micelles enter the epithelial cells from the ileum epithelial cells?

Answer 27

Simple diffusion as the fatty acids and monoglycerides are non-polar

Question 28

What happens once the micelles are in the cell?

Answer 28

They will be modified back into triglycerides inside of the ER and Golgi body

Question 29

What are fatty globules combined with proteins called?

Answer 29

Chylomicrons

Question 30

where is the chylomicron released inside?

Answer 30

inside of a Golgi vesicle

Question 31

What is the golgi vesicle released by?

Answer 31

Exocytosis

Question 32

What do micelles do to the fatty acids?

Answer 32

make them more soluble in water

Question 33

What do micelles maintain a higher concentration of?

Answer 33

Fatty acids to the cell lining of the ileum

Question 34

What happens to the lipids/chylomicrons after exocytosis?

Answer 34

Absorbed inside the lacteal and transported around in the lymph That drains into the capillary system

Question 35

Amino acid absorption by co-transport?

Answer 35

Co-transporter proteins are found in the epithelial cells CSM in the small intestine 1) Na+ ions are actively transported from the epithelial cell into the blood via the Na/K+ pump. This decreases the concentration of Na+ ions in the epithelial cells- creates a Na+ ion gradient 2) Na+ ions move down the conc gradient from the intestine into the epithelial cell carrying an amino acid with the co-transporter protein- facilitated diffusion 3) concentration of amino acids in the epithelial cells increase and amino acids diffuse down the concentration gradient into the blood

Question 36

Definition of absorption?

Answer 36

The transport of soluble molecules across cell membranes into the blood

Question 37

Definition of “gland” in the context of digestion?

Answer 37

An organ that releases enzymes. Secreted substances are added to food to aid physical digestion

Question 38

3 features inside the stomach to enable chemical and physical digestion?

Answer 38

Acidic conditions- low pH Digestive enzymes like protease Churning to mix contents.

Question 39

2 main roles of bile in digestion?

Answer 39

Neutralises stomach acids Emulsifying fats

Question 40

How do lipid droplets and micelles aid digestion and/or absorption?

Answer 40

Droplets increase surface area for lipase enzymes Increased surface area results in faster hydrolysis Micelles carry the fatty acids and glycerol across the cell surface membrane

Question 41

What do exopeptidases do?

Answer 41

Hydrolyse peptide bonds at the end of protein molecules- remove single amino acids from proteins

Question 42

Describe the role that enzymes play in the digestion and complete breakdown of starch

Answer 42

Starch is broken down into maltose via amylase. Maltose is broken down into 2 glucose molecules via maltase. Enzymes break the glycosidic bonds. The reaction is a hydrolysis reaction.

Question 43

Micelles role in absorption?

Answer 43

Combine with bile salts Making them more soluble in water Break down close to cells Contents diffuse across cell membrane into cells/ileum

Question 44

Micelles (3 mark mark scheme question)?

Answer 44

Micelles include bile salts and fatty acids Make the fatty acid more soluble in water Bring to cell lining of ileum Maintain high conc of fatty acids to cell of ileum Fatty acids absorbed by digestion

Question 45

Absorption of lipids?

Answer 45

Micelles carry the products of digestion to the cell surface membrane of the epithelial cell- break down near the CSM, releasing the products The products can now simply diffuse (as they are lipid soluble) Go to the smooth endoplasmic reticulum and triglycerides are reformed, then moved to the Golgi apparatus At the Golgi, triglycerides associate with cholesterol and proteins to form chylomicrons Leave via exocytosis and enter a lacteal