1. Cell Energetics:
Photosynthesis & Respiration

2. Carbon
• Carbon forms millions of compounds, both simple
and complex
• All living things contain carbon
• Living things cycle carbon from the air (inorganic gas
form) to the solid form (organic) and back to the air
• Light from the sun provides the energy for
photosynthesis, the process of making organic
compounds such as sugar
• The sun’s energy is stored the chemical bonds of
sugars and other carbohydrates
• Carbohydrates are used by most living things to
provide energy for LIVING

3. What is the Global Carbon Cycle?
• The movement of carbon between the atmosphere, soil,
ocean, living things, and fossil fuels
• Carbon exists primarily as:
- Gas, carbon dioxide (CO2), in Earth’s atmosphere
- Organic carbon in living and dead organisms.
• Atmospheric carbon is constantly recycled, mostly by
green plants and algae, to produce oxygen

4. The Global
Carbon Cycle
CO2 & other
greenhouse
gases
Dissolved carbon
Fossil fuel
Green plants
Algae & cyanobacteria
Emissions
from
burning
fossil fuel

5. Photosynthesis and Respiration in the
Global Carbon Cycle
Carbohydrates
&
Oxygen
Carbon dioxide
&
Water
Photosynthesis
Respiration
Creates stored
Energy-ATP

6. A few types of organisms do not
need sunlight and photosynthesis as
a source of energy.
• Some organisms live in places
that never get sunlight.
• In chemosynthesis, chemical
energy is used to build
carbon-based molecules.
– similar to photosynthesis
– uses chemical energy
instead of light energy
– occurs where light cannot
penetrate-deep ocean Biology-McDougal Littell 2008

7. A cell has some remarkable
organelles!!! Is this plant or animal?
Chloroplasts
Mitochondrion
Nucleus

8. The Chloroplast is Remarkable Organelle
Stroma
Thylakoid
Stroma = space/matrix inside the chloroplast where carbohydrate is
synthesized
Thylakoid = structures with chlorophyll and light reaction center

9. The Basic Process of
Photosynthesis
CO2 + H2O [C6H12O6] + O2
carbon dioxide water carbohydrate
(glucose)
oxygen
light energy

10. The Light Reactions-
Light Dependent
The Dark Reactions-
Light Independent
Photosynthesis in chloroplast is divided into…

11. The Light Reactions-
Light Dependent
The Dark Reactions-
Light Independent
MUST occur in the
presence of light
CAN occur in the
presence of light,
but works better
in the dark

12. Keeping track of the oxygen atom in photosynthesis
CO2 + H2O [CH2O] + O2
carbon dioxide water carbohydrates oxygen
light energy
Cornelius van Niel (1897-1985)
Standford University
Used radioactive-labeled oxygen in water and
unlabeled carbon dioxide in photosynthesis
experiments
Found that oxygen gas produced comes from water
Postulated that the oxygen atom in carbohydrates
must be from carbon dioxide

13. The Light Reactions
The Dark Reactions
ADP NADP+ NADPH
Carbohydrates CO2 + H2O
H2O O2
ATP

14. Where do the reactions happen inside the chloroplast?
Light reaction
Dark reaction
H2O
O2
CO2
Carbohydrates
Light reaction
occurs on
thylakoid
membranes
Dark reaction
occurs in the
stroma
MC.3.B.4