1. Enzymes

2. What is an Enzyme? Most enzymes are proteins
Act as a catalyst to speed up a chemical reaction by helping molecules react with each other faster

3. Enzymes are… Reusable! Specific for what they catalyze (speed up)
End in “-ase”
Named for the reaction they help. For example…
Sucrase breaks down sucrose
Proteases break down proteins
Lipases break down lipids
DNA polymerase builds DNA

4. Case Study: Lactose Intolerance
Lactase breaks down lactose, a common component of dairy products (like milk)
People lacking the enzyme lactase are considered “lactose intolerant”-they can’t digest large amounts of milk!!

5. Enzymes are not used up!
Re-used again for the same reaction with other molecules
Very little enzyme is needed to help in many reactions!
Substrate
Active Site
Products
Enzyme

6. Enzyme + Substrate  Enzyme + Product REACTANTS PRODUCTS
Lock and Key Model
Remember, enzymes are specific!
Lock and Key Model: Shape of enzyme allows substrate to fit
Specific enzyme for each specific reaction
Chemical Reaction
Enzyme + Substrate  Enzyme + Product
REACTANTS PRODUCTS

7. So…How Do Enzymes Work?
Enzymes work by weakening bonds, which lowers ACTIVATION ENERGY
Activation Energy=energy needed for the chemical reaction to occur (energy needed to activate!)
By lowering the activation energy, the reaction can occur faster!
Reactions can occur without the help…but not at the speed our bodies need!

9. What Effects Enzyme Activity?
Temperature
High temperatures can cause enzymes to denature (unfold and lose shape), while low temperatures slow molecules down pH
Changes in pH changes protein shape (most human proteins sit at a pH of 6-8)
Denaturing=extreme temperature and pH can change enzyme shape, rendering it useless!

10. Why are Enzymes Important?
Every reaction in your body is helped by an enzyme. They are necessary for all biological reactions!

11. Photosynthesis
Energy in the cell

12. What is photosynthesis?
Process that uses the sun’s energy to make glucose (food for the plant)
Performed in: Green plants and some bacteria
Occurs in the chloroplasts of the plant cell

13. PHOTOSYNTHESIS formula
6CO2 + 6H2O  C6H12O6 + 6O2
Carbon dioxide water glucose oxygen

14. Rate of photosynthesis
The rate (speed) at which a plant performs photosynthesis is based on a number of things:
# of reactants
More reactants yields more products
Temperature and pH
Recall that enzymes are directly impacted by these factors!
Light
No light=no photosynthesis

15. Cellular respiration
Energy in the Cell

16. What is cellular respiration?
Process where molecules of glucose are broken down to make CO2, water, and ATP
Occurs in the mitochondria of eukaryotes

17. C6H12O6 + 6O2 6CO2 + 6H2O + ATP Respiration formula
glucose oxygen carbon dioxide water energy

18. Cellular Respiration The point of cellular respiration is to make ATP!
ATP is ENERGY
All organisms require energy to live (movement, cell division, active transport, etc…)
Adenine
Three phosphates
Ribose

19. Photosynthesis and Respiration
What do you notice about the relationship between the two processes?

20. Aerobic vs. anaerobic respiration
Comparing Energy Processes

21. Aerobic Respiration
Aerobic respiration takes place in the presence of oxygen
This is most efficient-can produce up to 38 ATP per glucose!
Carried out in the mitochondria

22. But what if oxygen isn’t available?

23. Anaerobic Respiration
Anaerobic Respiration (fermentation) occurs when oxygen is NOT present
Less efficient-only 2 ATP produced!
Occurs in anaerobic bacteria, yeast, and muscle cells
Carried out in the cytoplasm

24. What is fermentation? Alcoholic Fermentation Lactic Acid Fermentation
Occurs in bacteria, yeast
Makes Ethanol (alcohol)
Used in making bread, wine, and beer
Occurs in muscle cells, bacteria
Makes Lactic Acid

25. Case study: muscle cramps
Anaerobic respiration can occur in muscle cells during vigorous physical activity
Once your cells begin to lack sufficient oxygen, they will switch to lactic acid fermentation
Lactic acid buildup and muscle fatigue leads to cramping!

26. Aerobic vs. anaerobic

27. Which of the following is true of enzymes?
They act on nonspecific, randomly chosen substrates
After a reaction, they cannot be reused
They can speed up metabolic processes in the body
They cannot change the shape

28. At which site on an enzyme do substrates bind and react?
Reaction site
Regulatory site
Active site
Catalysis site

29. Cellular respiration uses one molecule of glucose to produce:
2 ATP
34 ATP
36 ATP
38 ATP

30. To which class of organic compounds do enzymes belong?
Proteins
Fatty acids
Nucleic acids
Monosaccharides

31. Which is a difference between aerobic respiration and anaerobic respiration?
Anaerobic respiration requires oxygen
Anaerobic respiration does not require oxygen
Anaerobic respiration occurs only at the cellular level
Anaerobic respiration only occurs outside of the cell

32. How does an enzyme speed up chemical reactions?
By absorbing energy
By releasing energy
By decreasing the energy needed
By increasing the energy needed

33. Enzymes become hormones Enzymes become denatured
Many enzymes in the human body function best at 37 degrees Celsius. What is the most likely result of a great increase in body temp?
Enzymes become hormones
Enzymes become denatured
Enzymes become more active
Enzymes become more sluggish

34. Aerobic respiration results in less energy
How does the amount of energy resulting from fermentation compare with that of aerobic respiration?
Aerobic respiration results in less energy
Aerobic respiration results in more energy
Each process results in equal energy
Each process results in variable amounts of energy

35. Which most directly controls the rate at which food is broken down to release energy?
Enzymes
Hormones
Nucleic acids
Vitamins

36. Which of these is a product of photosynthesis and a requirement for cellular respiration?
Carbon dioxide
Glucose
Water
Sunlight

37. Which is a waste product of photosynthesis?
Carbon dioxide
Glucose
Oxygen
Water