1. Enzymes
A cell’s toolbox (Ch 6.4)

2. high
activation energy
without catalyst
activation energy
with catalyst
energy
content of
molecules
reactants
products
low
progress of reaction

3. An enzyme is a protein that
catalyzes a chemical reaction in living cells.
is not consumed in the reaction.

4. Enzyme structure
Many enzymes have both
active sites and allosteric
regulatory sites.
allosteric
regulatory site

5. active site
of enzyme
enzyme
1 Substrates enter
active site in a
specific orientation.
3 Substrates, bonded
together, leave enzyme;
enzyme ready for new
set of substrates.
2 Substrates and active
site change shape,
promoting reaction
between substrates.

6. Lactose (milk sugar) is a disaccharide.
Lactase
Lactose (milk sugar) is a disaccharide.
Lactase breaks lactose down into two monosaccharides, which can be absorbed in the small intestine.

7. Why would the genetic “error” causing lactose tolerance (the ability to drink milk all your life) be selected for in some parts of the world and not in others?

8. Amylase breaks ________ (amylose) apart into monosaccharides
Iodine turns black when ______ is present. How does the test in this picture demonstrate amylase activity?

9. Pepsin
Pepsin is a protease which breaks apart _______ chains into smaller chains or single _____ ______.

10. Enzyme regulation Allosteric inhibition Competitive inhibition
regulator
molecule
An allosteric regulator
molecule causes the active
site to change shape, so the
substrate no longer fits.
A competitive inhibitor molecule
occupies the active site and
blocks entry of the substrate.

11. Regulation controls enzyme pathways.
If one enzyme in the chain were missing, could the end product, G, be made?
If Product G came from another source, such as from consumed food, what would be its effect on this system?

12. Regulation may be through competitive or non-competitive inhibition.

13. methylenetetrahydrofolate reductase enzyme.
MTHFR gene:
methylenetetrahydrofolate reductase enzyme.
Located on the p arm of chromosome 1 in humans, this gene codes for an enzyme involved in the methylation of folic acid, a necessary B vitamin. Methylated (folate) and non-methylated (folic acid) forms are found in leafy greens, beans, and whole grains.

14. MTHFR is just one enzyme among many that convert certain nutrients into usable forms and convert waste into non-toxic forms.

15. Lack of the MTHFR enzyme causes buildup of homocysteine and/or folic acid, which can cause damage to the heart, blood vessels, and thyroid over time.
Homocysteine is normally converted to glutathione, one of the body’s chief antioxidants. People with a defective MTHFR enzyme lose the protection of this important antioxidant.
More information on the MTHFR gene on:
com/mthfr/

16. If you ate a lot of antacids, could that affect your digestion? Why?
pH influences enzyme activity
salivary
amylase
pepsin
enzyme
activity
acidic pH
basic
If you ate a lot of antacids, could that affect your digestion? Why?

17. What is one reason why high fevers can be dangerous?
Temperature influences enzyme activity
Maximum activity at
optimal temperature.
Enzyme activity
increases
High temperatures
distort enzyme
structure.
enzyme
activity
temperature
What is one reason why high fevers can be dangerous?

18. Recap
Enzymes are proteins that catalyze chemical reactions in living systems.
Each enzyme does one job, but does that job over and over again. This is referred to as enzyme specificity.