Enzymes

Question 1

Enzymes are ___ ___ that speed up ___ reactions in ___ cells.

Answer 1

biological, catalysts, chemical, living

Question 2

Enzymes are ___ because only one type of ___ fits into their ___.

Answer 2

specific, substrate, active site

Question 3

___ complexes are formed when the lock (___) finds a key (___).

Answer 3

Enzyme-substrate, enzyme, substrate

Question 4

Enzymes work best at the ___ temperature and pH, and the ___ substrate concentration as long as they can keep up.

Answer 4

optimum, highest

Question 5

Enzymes can become ___, irreversibly deactivating them by ___.

Answer 5

denatured, misshaping the active site

Question 6

___ break down ___ into ___ in the ___ as part of digestion.

Answer 6

• Carbohydrases (such as amylase in saliva in the mouth) break down carbohydrates into glucose in the mouth, stomach and small intestine.
• Proteases (such as pepsin in the stomach and trypsin in the small intestine) break down proteins into amino acids in the stomach and small intestine.
• Lipases break down fats and lipids into fatty acids and glycerol in the small intestine.

Question 7

Testing for starch with reagent ___:

Answer 7

reagent = iodine
1. Add a drop of iodine
2. If blue-black, starch is present

Question 8

Testing for reducing sugars with reagent ___:

Answer 8

reagent = Benedict’s solution
1. Mix with equal volume of B’s sol
2. Place in a 75°Cwater bath for a few minutes
3. Blue - none
4. Green or yellow - traces
5. Orangered - moderate amount
6. Brick red - large amount
7. Precipitate forms - very large amount

Question 9

Testing for proteins with reagent ___:

Answer 9

reagent = biurets
1. Add about 1 ml of water
2. Add an equal volume of potassium hydroxide
3. Add two drops of copper sulphate solution
4. Purple - protein present

Question 10

Testing for lipids with reagent ___:

Answer 10

reagent = ethanol
1. Shake mixture with ethanol
2. Add water and shake again
3. Emulsion, eventual seperation - lipids present