2. ENZYMES, DIET AND DIGESTION

biology test on enzymes

What is a biological catalyst?

a substance that speeds up a reaction without being used up

Why does digestion occur?

To break down large, insoluble molecules into small, soluble ones so they can be absorbed into the blood stream

Where does absorption take place?

Small intestine

What is an enzyme?

a protein that speeds up the rate of digestion

What are the three enzymes we have studied?

amylase, protease and lipase

What is a substrate?

a molecule on which enzymes act, forming products

What is the substrate of amylase?

starch

What is the substrate of protease?

protiens

What is the substrate of lipase?

fats

Where are carboydrase enzymes, like amylase, produced?

Salivary glands, pancreas, small intestine

Where are protease enzymes produced?

Stomach, pancreas, small intestine

Where are lipase enzymes produced?

Pancreas, small intestine

What are the products of starch digestion?

Sugars

What are the products of protein digestion?

Amino acids

What are the products of fat digestion?

Fatty acids and glycerol

Where does amylase digestion occur?

Mouth and small intestine

Where does protease digestion occur?

Stomach and small intestine

Where does fat (lipid) digestion occur?

Small intestine

Which organ produces bile?

Liver

Which organ stores bile?

Gall bladder

Describe 2 roles of bile.

• Emulsifies fats creating a larger surface area for lipase enzymes to act

• Is an alkali so neutralises the acidic contents from the stomach providing the optimum pH for lipase

Why does increasing temperature increase the rate of enzyme activity?

Enzyme and substrate molecules have more kinetic energy so move faster and collide more frequently. More enzyme-substrate complexes are formed as a result.

What happens when an enzyme is denatured?

The active site changes shape so that the substrate no longer fits

What is the optimum temperature for enzymes in the human body?

37°C

Which acid is found in the stomach?

Hydrochloric acid

How does hydrochloric acid in the stomach help digestion?

Provides optimum pH for protease enzymes

Which enzyme works best in acidic conditions?

Protease

Which enzyme works best in alkaline conditions?

Lipase

What provides alkaline conditions in the small intestine?

Bile

Describe how to test for starch.

Add iodine solution to sample and it will turn from orange-brown to blue-black if starch is present

Describe how to test for proteins.

Add Biuret solution to the sample and it will turn from blue to lilac if protein is present

Describe how to test for glucose.

Add Benedict's reagent to the sample and heat/boil it. It will turn from blue to brick red if glucose is present

Describe how to test for fats.

Add ethanol to food sample and mix. Then add water and if a white emulsion forms fat is present.

Which organ produces bile?

liver

Which enzyme (A or B) would most likely be found in the small intestine?

B (slightly alkaline optimum pH)

What is the optimum temperature for amylase activity based on the graph?

35C

DEFINITION

Identify organ 10

TERM

Liver

DEFINITION

Identify organ 8

TERM

gall bladder

DEFINITION

identify organ 3

TERM

stomach

DEFINITION

identify organ 4

TERM

small intestine

DEFINITION

identify organ 5

TERM

large intestine

Explain what is meant by the lock and key therory.

substrate has a complementary shape to the enzyme's active site so will bind to it to form an enzyme-substrate complex then the substrate is broken down into products which are then released.

What type of enyzme is amylase?

A carbohydrase enzyme

Why are enzymes described as specific?

Each active site has a specific shape that fits only one type of subtrate

Describe how the villi in the small intestine are adapted for their function.

• Many villi/microvilli which provide a large surface area for absorption

• one cell thick so provide a short diffusion distance

• good blood supply which maintains a steep concentration gradient

• contain many mitochondria to provide energy for active transport.