1. Unit 4: Energy Flow
ATP, Photosynthesis, and
Cellular Respiration

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

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

7. 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

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

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

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

11. Light-Dependent Rxn

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
(Light Independent Rxn)

12. Light Reaction – Electron
Transport

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

14. Photosynthesis Overview

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

16. Light Reaction

17. Calvin Cycle

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

19. Biochemical Energy

Cells store and release energy using ATP
– Adenosine triphosphate


ATP is the “energy currency” of the cell
Cells release energy by breaking a phosphate bond

20. Overview of Cellular Respiration

21. Cellular Respiration

Energy from glucose is
released
– In the presence of O2
– Energy is stored in ATP
– CO2 is a byproduct
6O2 + C6H12O6  6CO2 + 6H2O + ATP
oxygen + glucose carbon dioxide + water + ATP

22. Overview of Cellular Respiration

3 Stages
– Glycolysis
– Krebs Cycle
– Electron Transport Chain

23. 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


24. 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!!!!

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

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

27. 2
2
32

28. 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