3 & 4Food energy and Digestion

Question 1

Name the enzyme found in saliva

Answer 1

Amylase

Question 2

Define enzyme

Answer 2

Protein molecules that act as biological catalysts, increasing the rate of biological reactions without being used up

Question 3

Enzymes operate through the use of a mechanism called the ……?

Answer 3

Lock and key model

Question 4

Each enzyme is ….. to 1 particular molecule

Answer 4

Specific

Question 5

The molecule to which the enzyme reacts with is called the ….

Answer 5

Substrate

Question 6

Why are enzymes specific?

Answer 6

Due to the presence of a uniquely shaped pocket on the surface of the enzyme known as the active site

Question 7

Why are chemical reactions affect by temperature?

Answer 7

Due to kinetic theory

Question 8

What part of the enzyme is changed in high temperatures

Answer 8

The active site

Question 9

What happens to enzymes when exposed to high temperatures?

Answer 9

They become denatured

Question 10

Maximum enzyme activity occurs at the optimum temperature of ….

Answer 10

36-40 degrees Celsius

Question 11

Pepsin (protease) acts in …. …. in the …..

Answer 11

Acidic conditions … stomach

Question 12

Inhibitors definition

Answer 12

inhibitors are molecules that fit the active site but are not broken down

Question 13

Give the substrate and products of the following enzyme:
Amylase-
Protease-
Lipase-

Answer 13

Amylase substrate: starch
Products: simple sugars, glucose
Protease substrate: proteins
Products : amino acids
Lipase substrate: lipids
Products : Glycerol and fatty acids

Question 14

Give a commercial use of enzymes (2)

Answer 14

• Many biological washing powders have enzymes for breaking down difficult to remove stains.
• These enzymes are thermostable - they can work at a wide range of temperatures and they break the complex, large and insoluble stains down into small, soluble molecules that dissolve in the water

Question 15

Certain molecules have a shape that is similar to the substrate, allow them to … into the …. … of the enzyme but are not …. …..

Answer 15

Fit , active site , broken down

Question 16

What is pepsin’s optimum pH ?

Answer 16

Around 3

Question 17

Digestion continues in the upper parts of the small intestine (the ….. and ….. ) and is complete in the …..

Answer 17

Duodenum and jejenum .., ileum

Question 18

During digestion the large insoluble biomolecules (….., ….. and …. ) have all been broken down into small soluble molecules that can enter the bloodstream through a process known as ….. .

Answer 18

proteins, lipids and starch

Absorption

Question 19

Name five features of the ileum which increase the efficiency of absorption and explain them

Answer 19

• Approximately 3m long, increases the surface area
• highly folded form along its length, increases the surface area
• excellent blood supply, maintains the concentration gradient required
• thin (1 cell thick), highly permeable walls, reduces the diffusion distance
• presence of villi, further increases the surface area

Question 20

What do villi contain and what are they responsible for ?

Answer 20

They contain lacteals and these are responsible for the absorption of fatty acids and glycerol. These molecules then travel through the lymphatic system and join the blood steam in another part of the body

Question 21

The walls of villi are made of a single layer specialised cells. What are they called?

Answer 21

Epithelial cells

Question 22

Amylase acts in neutral slightly ….. conditions in the mouth

Answer 22

alkaline

Question 23

Equation for the energy released from food per gram (J)

Answer 23

mass of water (g) x temp. rise x 4.2
———————————————
mass of food sample (g)

Question 24

How does low temperature affect an enzyme?

Answer 24

Low temperature causes reduced rates of collision between substrate and enzyme

Question 25

When does denaturing of the enzyme occur ?

Answer 25

It occurs increasingly at levels above the optimum

Question 26

What chemical elements make up carbohydrates and fats/lipids

Answer 26

All carbohydrates contain the chemical elements carbon (C), hydrogen (H) and oxygen (O).

Question 27

How are villi adapted to absorption?

Answer 27

• villi aid absorption due to their excellent blood supply

Question 28

How do the surface epithelium cells aid absorption?

Answer 28

They are a single layer of cells that reduce the number of cells between the lumen of the gut and the capillaries and lacteals

Question 29

Define digestion

Answer 29

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