1. Energy for Cells, Photosynthesis, and Respiration
Flow of Energy
Energy for Cells, Photosynthesis, and Respiration

2. Energy for Cells: Living organisms need energy to function
WHERE DO THEY GET IT?
Free Energy: energy available to do biological work
Ex. Energy required for muscle contraction
Endergonic Reaction: chemical reaction requiring free energy

3. *Free energy comes from other chemical reactions:
Exergonic Reactions: “Energy releasing”
*Both reactions must be linked (b/c energy can’t just “wait around”)
*Most free energy comes from adenosine triphosphate-- ATP
ATP: A-P-P-P
*the bonds between P (phosphate groups)  energy released
Ex. Hydrolysis: (ATP + H20); last P breaks off  ADP
ATP + H20  ADP + Pi + energy

4. Mini Lab Demonstration:
*Can you detect energy released by a biological reaction?
Half fill a test tube with 3% hydrogen peroxide.
Use a thermometer– take initial temperature.
Add a small piece of fresh liver to the tube.
Observe what happens. After 1 min., retake temp.
What evidence of a reaction did you observe?
Was the reaction endergonic or exergonic?

5. Respiration with Oxygen:
*When ATP is used, energy is released.
HOW CAN ATP BE REPLENISHED???
*REJOIN ADP and PHOSPHATE to replenish supply of ATP
(But need energy to do so)
Cellular Respiration: some of energy released by breaking bonds of glucose converts ADP to ATP

6. *AEROBIC RESPIRATION: requires Oxygen
*Cellular respiration is usually aerobic
EXERGONIC
*First steps occur in cytoplasm; last steps are in mitochondria
C6H12O6 + 6O ADP + 38 Pi 6CO2 + 6H ATP
*Early steps of breaking down glucose require 2 ATP
Thus, a net product of 36 ATP are produced
*What’s this mean? 1 glucose molecule  released little by little  lots of ATP

7. ATP is the cell’s currency!!!!

8. Anaerobic Processes *absence of oxygen
*Some bacteria and muscle cells can switch between aerobic and anerobic processes
Lactic Acid Fermentation:
*enzymes break down glucose into 2 lactic acid molecules
C6H12O6 + 4 ADP + 4 Pi  2CH3CHOHCOOH + 4 ATP
Ex. Muscles build up lactic acid during excessive exercise

9. C6H12O6 + 4 ADP + 4 Pi  2C2H5OH + 2CO2 + 4 ATP
Alcoholic Fermentation: plants/ microorganisms
*enzymes break down glucose into 2 molecules of ethanol and 2 molecules of CO2
C6H12O6 + 4 ADP + 4 Pi  2C2H5OH + 2CO2 + 4 ATP
Ex. Yeast  alcohol, gasoline additives, bubbles  dough rises

10. Both types
use 2 ATP
during process--
net product
is only
2 ATP!!!

11. PHOTOSYNTHESIS REVIEW: Producers = plants, algae, & some bacteria
*PRODUCERS  absorb energy from
Creates chemical energy
REVIEW: Producers =
plants, algae,
& some bacteria

12. Some light is absorbed; some reflected
REVIEW:
LIGHT = WAVELENGTHS
VISIBLE SPECTRUM= ROY G BIV
Some light is absorbed; some reflected
Ex. White reflects all

13. *Light energy  chemical energy due to pigments
Ex. Chlorophyll (a) appears green b/c reflects green light
Other pigments: CAROTENOIDS:
Yellow, orange, and red
*absorb other colors/ wavelengths and pass energy to chlorophyll (a)
THIS IS WHY LEAVES CHANGE COLOR!!!

14. PHOTOSYNTHESIS REACTION:
6CO2 + 6H20  C6H12O6 + 6O2
* “” involves enzymes, chlorophyll, and light energy
*ENDERGONIC
*ultimate source of energy comes from light
Place Elodea in two test tubes.
Fill test tubes w/ Bromothymol yellow and cover tubes with plastic.
Place one tube in direct light and the other in a dark place.
Compare in 24 hours.
If yellow color is gone, means CO2 is no longer present.
MINI LAB 2:

15. PHOTOSYNTHESIS: 2 PARTS:
1. LIGHT REACTIONS:
Chloroplasts: electrons absorb energy/ move to higher energy levels
3 MAIN EVENTS:
1. Light energy absorbed and converted to chemical energy in bonds of ATP
Water splits into H ions, O, and electrons
H ions from water  attach to carrier coenzymes for later use

16. 2. CALVIN CYCLE: *Occurs in fluid of chloroplast *Synthesizing sugars
REVIEW: WHAT ELEMENTS MUST BE PRESENT FOR SUGARS TO BE MADE?
Light reactions provide H ions and ATP + CO2 
3 carbon sugars  6 carbon sugars  more complex

17. ENERGY RELATIONSHIPS Thus, a CONTINUOUS CYCLE is NECESSARY!!
*PLEASE REFER TO PAGE 160
**Photosynthesis is the opposite of respiration
**These processes are INTERDEPENDENT:
reactants of one are products of the other
*Sugars are broken down in cellular respiration (ATP used)
ATP can’t be recycled– some given off as heat as well
Thus, a CONTINUOUS CYCLE is NECESSARY!!

18. THE END!