PHOTOSYNTHESIS

How do organisms get energy?

• Autotrophs and Heterotrophs–Autotrophs – organisms that

can capture energy from sunlight or chemicals and use it to produce its own food.

How do organisms get energy?

• Autotrophs and Heterotrophs–Heterotrophs – organism that

obtains energy from the foods it consumes

Chemical Energy and ATP ATP (adenosine triphosphate) = The

principal chemical compound that living things use to store energyo ATP = 3 Phosphate groups

ADP (adenosine diphosphate) has a very similar structure to ATP, but with only two phosphate groups. o ADP = 2 Phosphate groups

Chemical Energy and ATP• The energy stored in ATP is released

when ATP is converted to ADP. The breaking of the bond between the second and third phosphate group releases this energy.

Chemical Energy and ATPATP ADP

Fully charged battery

Partially charged battery

   

Investigating Photosynthesis• When a tiny seedling grown into a tall tree

with a mass of several tons, where does the tree’s increase in mass come from? From soil? From water? From air?

Investigating Photosynthesis Van Helmont – 1600s

oWanted to know if plants grew by taking material out of the soil.

oWeighed a pot of dry soil and a small seedling. He watered it regularly and at the end of five years the seedling had gained 75 kg. The mass of the soil was exactly the same.

oHelmont concluded that the mass gain came from water

oHE WAS WRONG

Investigating Photosynthesis Priestly – 1700soPut a candle under a bell jar, the

fire went out. Added a small plant and the fire continued to burn for a few days.

Through the work of all these scientists it was discovered that…..

• In the presence of light, plants transform carbon dioxide and water into carbohydrates and

release oxygen

Investigating Photosynthesis Ingenhousz

o Showed that Priestly’s results were only valid if the plant was exposed to light.

Photosynthesis 6CO2 + 12H2O + light → C6H12O6 + 6O2

Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into oxygen and high-energy sugars

Light and Pigments Plants gather the sun’s energy with light-

absorbing molecules called pigments. The plant’s principal pigment is

chlorophyll

Inside a Chloroplast Photosynthesis takes place inside the

chloroplastoChloroplasts contain saclike membranes

called thylakoids (looks like a pancake)oA stack of thylakoids is known as grana

(looks like a stack of pancakes)oThe area outside of the grana, but inside

the chloroplast is known as stroma (kind of like the syrup on the pancakes)

Inside a Chloroplast

The Chemical Reactions of Photosynthesis

•NADPH Like ATP, the molecule

NADPH can also store energy.oNADP+ + Energy NADPHo So when an organism

breaks down NADPH energy it gets NADP+ and energy

NADPH NADP+

Fully charged battery

Partially charged battery

   

The Chemical Reactions of Photosynthesis

•Light-Dependent Reactions REQUIRE LIGHT Light-dependent reactions

produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH

Harvests the sun’s energy and charges the battery

The Chemical Reactions of Photosynthesis

•Calvin Cycle Because the Calvin Cycle does not require

light, it is also called light-independent reactions

The Calvin cycle uses ATP and NADPH form the light-dependent reactions to produce sugarUses the energy stored in

the light-dependent reactions to create food.

Factors Affecting Photosynthesis

Weather oAmount of rainoTemperatureoIntensity of light