Enzymes and digestion

Question 1

what is digestion?

Answer 1

the breakdown of large complex molecules into simple soluble substances so that they can pass through the walls of the intestine and into the blood by diffusion

Question 2

what are enzymes?

Answer 2

biological catalysts which speed up reactions in plants and animals. made of proteins

Question 3

what are enzymes?

Answer 3

specific - they have a specific shape in which only the substrate can fit. this will then be broken down

Question 4

what is the enzyme-substrate complex also called?

Answer 4

lock and key mechanism

Question 5

what are enzymes sensitive to?

Answer 5

changes in pH and temperature. if conditions are not ideal, enzymes become denatured and stop working as the active site is no longer complementary to the substrate

Question 6

explain food test for starch?

Answer 6

iodine chemical added directly to substance to be tested. look for colour change: blue black if positive orange if negative

Question 7

explain food test for reducing sugar

Answer 7

add benedict’s to solution and heat for two mins in a water basin at boiling temperature and look for colour change. red - high orange - medium green - low blue - none

Question 8

explain food test for protein

Answer 8

add biuret’s solution directly to substance and look for colour change. purple is positive

Question 9

food test for lipids ? emulsion test

Answer 9

emulsion test - add ethanol to solution and shake thoroughly. add water and look for change. turns milky white if positive.

Question 10

food test for lipids? sudan 3 test

Answer 10

add sudan 3 stain to lipid solution in water and shake. the lipid will float to top and be coloured red

Question 11

mouth

Answer 11

mechanical digestion - teeth grind to smaller molecules for larger surface area
salivary amylase: starch + amylase = simple sugar
carbs + carbohydrase + simple sugar
glucose = C₆H₁₂O₆

Question 12

oesophagus

Answer 12

muscular contractions of food - peristalsis

Question 13

stomach

Answer 13

contains hydrochloric acid with pH 1-2 that kills bacteria and provides ideal acidity for enzyme. churns food
digests protein
protein + protease = amino acids
build and repair damage cells + tissue

Question 14

liver

Answer 14

creates bile (not enzyme) that neutralises stomach acid and emulsifies fat, creating large surface area

Question 15

gall bladder

Answer 15

stores bile

Question 16

pancrease

Answer 16

releases all 3 enzymes + all enzymes found in small intestine
lipids + lipase + fatty acids + glycerol
proteins + protease = amino acids
carbs + amylase = sugar

Question 17

small intestine

Answer 17

long, folded, villi + microvilli giving large surface area. villi have good blood supply + thin walls. absorb nutrient from food

Question 18

large intestine

Answer 18

absorbs excess water from food

Question 19

rectum

Answer 19

stores feaces - dead cells + bacteria