🧫 Enzymes and Digestion 🧁

Question 1

Enzyme

Answer 1

Enzymes are chemical compounds made from proteins that speed up the rate of reactions – biological catalysts

Question 2

What are the two main types of enzymes?

Answer 2

Catabolic and anabolic enzymes

Question 3

Catabolic enzymes

Answer 3

Break down large molecules into smaller ones

Question 4

Anabolic enzymes

Answer 4

Build up large molecules from smaller ones

Question 5

Catalase

Answer 5

– The fastest enzyme

– contained in liver cells

– speeds up the breakdown of hydrogen peroxide – poisonous substance formed as a product of reactions in cells

Question 6

What is the word equation for hydrogen peroxide and catalase

Answer 6

Catalase
hydrogen peroxide ——> water +
oxygen

Question 7

What are the observations for hydrogen peroxide and catalase?

Answer 7

– Vigourous reaction 🤜
– Lots of gas/bubbles produced – effervescent 🫧
– Oxygen is given off as it relights a glowing splint 🔥
– Catalase is a catabolic enzyme – hydrogen peroxide is broken down into water and oxygen 💧 🫧

Question 8

Substrate

Answer 8

The molecule on which an enzyme acts

Question 9

Product

Answer 9

The molecule formed by the reaction of an enzyme and a substrate

Question 10

How do enzymes work?

Answer 10

– Each enzyme has an active site – the site of the reaction takes place

– they breakdown or build up substrates into products

– each enzyme can only work on a certain type of substrate

– this is because the shape of each enzyme is unique

Question 11

Model gut experiment method

Answer 11

1. Mix 15 cm3 starch + 15cm3 glucose in small beaker
2. Transfer 5 cm3 of mixture to test tube + test for starch – iodine solution
3. Transfer 5 cm3 mixture to 2nd test tube + test for sugar – Benedicts’ reagent
4. Transfer 20 cm3 of mixture to dialysis tubing bag + tie the top of the bag
   – wash outside of bag remove traces of mixture
   – dialysis bag represents gut
5. Transfer bag to boiling tube containing distilled water
   – represents blood surrounding gut
6. leave bag in water – 10 mins
   - test Surrounding water, blood, for starch + sugar

Question 12

Model gut experiment results

Answer 12

Mixture = + starch + glucose

Surrounding water = - starch + glucose

Question 13

Model gut experiment conclusion

Answer 13

Results show digestion is essential to ensure food molecules are small and soluble enough to be digested

Question 14

How do enzymes and substrates work?

Answer 14

• the enzyme has a specific shape and active site
• only a specific substrate will fit into the active site
• the enzyme and substrate together form a substrate complex
• the reaction takes place and new products are released from the enzyme
• the enzyme is ready to react with another substrate

Question 15

Lock and key model

Answer 15

Enzyme substrate –––> enzyme – substrate complex –––> enzyme product

Question 16

Inhibitors

Answer 16

• molecules that fit loosely or partially into the active site of some enzymes

– occupy the active site and proper substrate molecules cannot enter and be broken down

• leads to a reduced (inhibited) rate of reaction

Question 17

What is the effect of temperature on enzymes?

Answer 17

– if enzymes do not have the optimum temperature they work less effectively

– Low temperatures cause reduced kinetic energy of enzymes and substrates
- leads to reduced rates of successful collisions and lower enzyme activity

• Temperatures increase – more kinetic energy, more collisions, enzyme activity increases
• above optimum enzymes become denatured 

Question 18

Denatured 

Answer 18

The shape of the enzymes active site changes irreversibly

Question 19

Optimum

Answer 19

One particular temperature and pH all enzymes work best at/ highest level of activity

Question 20

Kinetic energy

Answer 20

Movement energy

Question 21

What is the effect of pH on enzymes?

Answer 21

• incorrect pH changes the shape of the enzymes active site (denatures enzyme)
  – most enzymes work best in neutral conditions
• some work in acid conditions e.g. protease, stomach

Question 22

What is the effect of concentration on enzymes?

Answer 22

• more enzymes = faster reaction
• more active sites for substrates to attach to
• applies up to a limit, rates level off because there are not enough substrate molecules to react with extra enzymes

Question 23

Commercial enzymes

Answer 23

• manufacturers add enzymes to some washing powders to enhance stain removal
• large complex food molecules in food do not dissolve well in water there often left on clothes after washing
• a variety of enzymes means a variety of food molecules can be broken down e.g. amylase and starch, protease and protein
• biological washing powders

Question 24

Thermostable enzymes

Answer 24

work at a wide range of temperatures

Question 25

Substrate: Carbohydrate

Answer 25

Enzyme: Carbohydrase

Product: Simple sugar/glucose

Question 26

Substrate: starch

Answer 26

Enzyme: amylase

Product: simple sugar/glucose

Question 27

Substrate: protein

Answer 27

Enzyme: protease

Product: amino acids

Question 28

Substrate: fat – lipids

Answer 28

Enzyme: lipase

Product: glycerol and fatty acids

Question 29

Peristalsis

Answer 29

Series of involuntary wave-like muscle contractions which move along the digestive tract

Question 30

Digestion

Answer 30

The breakdown of large complex insoluble molecules in the small, simple, soluble ones

Is necessary to ensure food molecules are small and soluble enough to be absorbed into the bloodstream and cells

Question 31

Why do we need to digest and break down food?

Answer 31

• most of the Food we eat is in the form of large, complex, insoluble molecules

– we need to digest and break time is molecules so they are small and soluble enough to be absorbed into the blood system

• the digestive system is adapted to allow the body to carry out digestion so that it can gain all the nutrients we need from our food

Question 32

Ingestion

Answer 32

Food is taken into the body 

Question 33

Mechanical digestion

Answer 33

Physically breaking food into smaller pieces
e.g. mouth – teeth and tongue physically crush food into smaller pieces
e.g stomach – churning action of stomach muscles physically breaks semi-digested food up

Question 34

Absorption

Answer 34

Digested food goes into the bloodstream

Question 35

Egestion

Answer 35

Food cannot be digested goes out of the anus

Question 36

Assimilation

Answer 36

Process were digested food molecules are absorbed into body cells

Question 37

Chemical digestion

Answer 37

Food molecules are broken down into small soluble molecules by enzymes

Question 38

Digestion in the mouth

Answer 38

enzyme: amylase

substrate: starch

products: glucose/simple sugars

Question 39

Digestion in the stomach

Answer 39

enzyme: protease (pepsin)

substrate: protein

product: amino acids 

Question 40

Digestion in the duodenum

Answer 40

enzymes: amylase, protease, lipase

substrates: starch, protein, fats (lipids)

products: glucose and simple sugars, amino acids, glycerol and fatty acids

Question 41

Digestion in the ileum

Answer 41

enzymes: amylase, carbohydrase, protease, lipase

substrates: starch, protein, fats (lipids)

Products: glucose/simple sugars, amino acids, glycerol and fatty acids

Question 42

How is the ileum adapted for the process of absorption?

Answer 42

• Great length (3m) - increases surface area for absorption
• highly folded surface – greatly increases surface area for digested food
• villi – greatly increase surface area for absorption
• good blood supply - maintains Steep concentration gradient – capillary network in each villus
• thin layer of surface cells – short diffusion distance
• thin permeable membranes - allow digested food molecules to pass through easily

Question 43

Villi

Answer 43

Millions of microscopic outgrowths on the inner surface of the ileum

Question 44

Test for oxygen

Answer 44

Relights a glowing splint

Question 45

Carbohydrase

Answer 45

Group of enzymes that act on carbohydrates

Question 46

Enzyme specificity

Answer 46

each enzyme will only react with one or a small group of substances

Question 47

Digestion

Answer 47

the process by which large, complex, insoluble molecule are broken down into small, simple, soluble ones

Question 48

Ileum

Answer 48

part of the small intestine responsible for the absorption of digested food molecules into the blood

Question 49

Villi

Answer 49

microscopic outgrowths on the inner surface of the ileum which great| increase the surface area for absorption

Question 50

Lacteal

Answer 50

part of each villus that absorb the digested products of fat