digestion

Question 1

what is digestion?

Answer 1

the hydrolysis of large molecules into smaller molecules that can be absorbed across cell membranes

Question 2

where does physical digestion occur?

Answer 2

mouth (teeth) and stomach (churning)

Question 3

where does chemical digestion occur

Answer 3

mouth stomach and ileum

Question 4

what is the pancreas’ role in digestion

Answer 4

makes digestive enzymes but doesnt do any digesting and squirts its enzymes into small intestine

Question 5

what is food digested by

Answer 5

extracellular enzymes

Question 6

what are extra cellular enzymes

Answer 6

enzymes produced by epithelial cells

Question 7

what is ingestion

Answer 7

taking in food

Question 8

what is egestion

Answer 8

passing of food as faeces

Question 9

what is excretion

Answer 9

the removal of metabolic waste

Question 10

how are carbohydrates digested into their products

Answer 10

by the hydrolysis of glycosidic bonds

Question 11

how is starch broken down

Answer 11

broken down by amylase (either in mouth or pancreas) into maltose

Question 12

how is maltose broken down

Answer 12

maltose is broken down by enzyme maltase which is membrane-bound in ileum into two glucose molecules

Question 13

how is lactose broken down

Answer 13

broken down by lactase into glucose and galactose

Question 14

how is sucrose broken down

Answer 14

by enzyme sucrase into glucose and fructose

Question 15

what enzymes digest proteins

Answer 15

peptidases

Question 16

how are proteins digested

Answer 16

by hydrolysis of peptide bonds

Question 17

what do endopeptidases do

Answer 17

break peptide bonds inside protein

Question 18

what do exopeptidases do

Answer 18

break peptide bonds at ends of protein to form a dipeptide and two amino acids

Question 19

what do dipeptidases do

Answer 19

break peptide bond in a dipeptide forming two amino acids

Question 20

what is co transport

Answer 20

Co-transport is the coupled movement of substances across a cell membrane via a carrier protein. It involves a combination of facilitated diffusion and active transport.

Question 21

how are glucose/amino acids absorbed

Answer 21

1) Na+ actively transported out of cell into blood therefore forming diffusion gradient between lumen and cell
2) Na+ and glucose/amino acid enter cell from lumen via a co transporter protein
3) glucose enters cell via facilitated diffusion

Question 22

what is bile

Answer 22

Bile salts made by the liver, emulsify lipids in order to increase the surface area of the lipids, for greater access to lipases

Question 23

what are micelles

Answer 23

the combination of fatty acids and monoglycerides to form a structure

Question 24

what is the first step in digesting lipids

Answer 24

large lipid droplets are emulsified by bile into small lipid droplets

Question 25

what is the second step in digesting lipids

Answer 25

small lipid droplets are hydrolysed by lipases which are made in the pancreas into fatty acids and monoglycerides

Question 26

how are lipids absorbed

Answer 26

1. micelles move to cell surface membrane of epithelial cells and breakdown into monoglycerides and fatty acids
2. monoglycerides and fatty acids move across cell surface membrane by simple diffusion
3. via the endoplasmic reticulumn and golgi, triglycerides are reformed and made into specialised vesicles called chylomicrons
4. chylomicrons releases triglycerides by exocytosis out of cell and into lymph

Question 27

why do monoglycerides and fatty acids move across cell surface membrane via simple diffusion

Answer 27

because they are lipid soluble substances

Question 28

why do lipids need to be emulsified

Answer 28

emulsification of lipid droplets greatly increases surface area for lipase enzymes to work on