1. Unit 4: Energy

2. Energy – What is it?
 The ability to do work
 Energy can not be created or destroyed
– Energy is TRANSFORMED
 Forms of energy
– Light, electric, chemical
 Chemical energy is stored in the
electrons of chemical bonds

3. Biochemical Energy
 Cells store and release energy using the
chemical ATP
– Adenosine triphosphate
 ATP is the “energy currency” of the cell
– MANY cellular processes use ATP
 Cells release energy by breaking a phosphate
bond

4. Photosynthesis
 Plants convert light energy into chemical
energy
 Energy is stored in the bonds of
carbohydrates

5. Light and Pigments
 Light travels in waves
 Colors have different wavelengths
 “White” light is a mixture of all colors in the
visible spectrum
 Red – longest wavelength, lowest energy

6. Light and Pigments
 Plant pigments absorb sunlight
 Chlorophyll – green pigment needed for
photosynthesis
– Reflects green light
– Absorbs other light

8. Photosynthesis Overview
 Reactants: CO2, H2O, light energy
 Products: O2, C6H12O6 (glucose)
 Two reactions
– Light reaction
– Calvin Cycle (light-independent reaction)

9. Chloroplast Structure
 Thylakoid sacs contain chlorophyll
 Granum – stacks of thylakoids
– Light rxn
 Stroma – open space
– Calvin cycle

10. Photosynthesis Overview

11. Electron Carriers
 Light energy “excites” electrons in
chlorophyll
 High energy electrons need special
carriers
– ie: NADP+ and NAD+

12. Light Reaction
 Chlorophyll absorbs light, and electrons
become energized
 Water splits to produce H+ and O2
 Electron loses energy to form ATP
– ATP goes to Calvin Cycle
 H+ and NADP forms
NADPH
– Carries energy to
Calvin Cycle

13. Light Reaction – Electron
Transport

14. Light Reaction

15. Light Independent Rxn
 CO2 is added to a 5 carbon sugar
 Energy from NADPH & ATP are used to
carry out reactions
 Produces sugar
(glucose)

16. Calvin Cycle

17. ATP Revisited
 How do living things use ATP for
energy?
 Where does ATP come from?

18. Overview of Cellular Respiration
6O2 + C6H12O6  6CO2 + 6H2O + ATP

19. Overview of Cellular Respiration
 Energy from glucose is released
– In the presence of O2
– Energy is stored in ATP
– CO2 is a byproduct
 3 Stages
– Glycolysis
– Krebs Cycle
– Electron Transport Chain

20. Glycolysis
 In the cytoplasm
 Glucose breaks into 2 molecules of pyruvic
acid (3C)
 Uses 2 ATP, produces 4 ATP
– Net gain of 2 ATP
 2 NADH produced
 Pyruvic acid is used
for respiration OR
fermentation

21. Krebs Cycle
 In the mitochondria
 Pyruvic acid breaks down
 Series of 9 rxns which
produce:
– CO2
– FADH2 and NADH
– 2 ATP
 FADH2 and NADH go on
to the ETC to….
– MAKE MORE ATP!!!!

22. Electron Transport Chain
 Occurs in mitochondria
 Uses high energy
electrons from FADH2
and NADH to make ATP
 O2 accepts the final
electron forming H2O

23. Page 229
The Totals
Electron carriers
which go on the
electron transport
chain to generate
ATP!

24. 2 2 32

25. Fermentation
 Releases energy from food in the
absence of O2
 2 Types
– Alcoholic – produces ethanol and CO2
• Yeast, bacteria
– Lactic Acid – produces lactic acid
• Muscle cells, bacteria