B3 - Organisation and the Digestive System

Question 1

How is the stomach adapted to its function?

Answer 1

• Musclar t- churns food mechanically -
  faster digestion
• Glandular t - produces enzyme which catalyses
  the reaction of proteins into amino
  acids
  produces hydrochloric acid that
  provides suitable PH for the enzyme
  and kills bacteria
• Epithealial t: covers the stomach and protects
  the wall of the stomach from the
  acid

Question 2

What is the function of the glands?

Answer 2

produce enzymes, e.g Salivary gland, pancreas

Question 3

What are enzymes?

Answer 3

Large proteins
Catalyse the reactions in metabolism

Question 4

Explain the lock and key model.

Answer 4

Enzyme is the lock, and substrate the key; the enzyme will only bind to a specific and complementary substrate.
If the substrate is not complementary to the enzyme’s active site , there is no reaction.

Question 5

Explain the affect of temperature on enzyme-controlled reactions:

Answer 5

Increasing the temperature increases the rate of the reaction
Until it gets too hot, bonds in enzyme break, the active site change shape and the substrate no longer fits the active site, the enzyme is denatured.

Question 6

What are the variables in the Enzyme practical?

Answer 6

ID - PH (using the buffers)
DP - time it takes for amylase to digest starch (using iodine solution to test the presence of starch, stopwatch)
CV - Starting concentration of starch, temperature, concentration of amylase

Question 7

Write a method for the enzyme practical.

Answer 7

• Put a test tube of amylase and test tube of starch in a water bath until the are the same temperature.
• Add the amylase to the starch.
• Every 30s remove a drop and add to a spotting tile containing iodine solution.
• Record how long it takes for the starch to be completely digested - when it turns blue-black
• Repeat this at different pH values using different buffer solutions.

Question 8

Why do you need a water bath?

Answer 8

To maintain the temperature, because temperature affects the rate of reaction

Question 9

If you test at pH 3, 4, 5, 6, 7, 8, 9 and 10, Why don’t we know the exact optimum pH?

Answer 9

Although 2 PHs may both show quick reactions, the optimum could be in between the PHs.
So you would need to repeat the test at smaller intervals between the PHs to determine the optimum more accurately

Question 10

How do you calculate the rate of an enzyme-controlled reaction?

Answer 10

1 / time (in seconds)

Question 11

What are sugars used for?

Answer 11

releasing energy quickly

Question 12

What are proteins used for?

Answer 12

Growth and repairment of cells

Question 13

Where are carbohydrases produced?

Answer 13

Salivary glands,
pancreas, small intestine

Question 14

Where do carbohydrases act?

Answer 14

Mouth,
Small intestine

Question 15

Where are proteases produced?

Answer 15

Stomach,
pancreas, small intestine

Question 16

Where do proteases act?

Answer 16

Stomach,
small intestine

Question 17

Where are lipases produced?

Answer 17

Pancreas, small intestine

Question 18

Where do lipases act?

Answer 18

Small intestine

Question 19

Function of bile, and where is it produced and released?

Answer 19

Produced : liver
Released : small intestine
- emulsifies fat - increases surface area for faster absorption
- nuetralises stomach acid

Question 20

Test for the presence of sugars

Answer 20

Benedict’s solution, turns blue to brick-red
the B solution needs heating

Question 21

Test for the presence of starch

Answer 21

Iodine solution, turns orange to blue-black

Question 22

Test for protein

Answer 22

Biuret solution, blue to purple