Photosynthesis & Respiration

What is Photosynthesis?

The process of photosynthesis is a chemical reaction.

It is the most important

chemical reaction on our planet.

What is the equation for the chemical reaction of

photosynthesis?

What is the equation for the chemical reaction of

photosynthesis?

Six molecules of carbon dioxide react with six molecules of water

to form 1 molecule of glucose and six molecules of oxygen.

Describe Photosynthesis

• The process of changing light energy to chemical energy

• Energy stored as sugar

• Occurs in plants and some algae

• Plants need light energy, CO2, and H2O

• Takes place in the chloroplasts, using chlorophyll, the green pigment in plants

What are the two parts two parts of photosynthesisphotosynthesis?

• the light reactionthe light reaction

requires light requires light and must be firstmust be first

• the light-independent reactionthe light-independent reaction

does not require light does not require light

but must followfollow the light reaction

TRIVIA: This used to be called the dark reaction. Why is not used today?

What happens during photosynthesis?

• Plants capture light energy and use that energy to make glucose

• Sunlight provides the energy needed by chlorophyll to change molecules of carbon dioxide and water into glucose

• Oxygen is also released in this reaction

The Light Reaction

1.1. Chlorophyll is energized Chlorophyll is energized by sunlight

2. The energy splitssplits a waterwater molecule

3. A. The oxygenoxygen is released

B. EnergyEnergy is stored by hydrogen(NADPH)

and ATP

The Light-Independent Reaction

1. Carbon dioxide combines with RuBP to form PGA

2. PGA is converted to PGAL (G3P)

3. PGAL (G3P) can be:a. used as a nutrient for the plant

b. converted back to RuBP (recycled)

c. converted to GLUCOSEGLUCOSE

Who first figured out this process?

Melvin CalvinMelvin Calvin

Because of his work, the light independent reaction is known more commonly as the “CALVIN CYCLECALVIN CYCLE”

It is also known as “carbon fixationcarbon fixation” because carbon is converted to a usable and organic molecule.

Melvin Calvin1911 – 1997

Nobel Laureate

Calvin worked with Benson so

the cycle is also calledthe Calvin – Benson cycle

What happens during photosynthesis?

• Carbon dioxide enters the leaf through holes called stomata

• CO2 combines with the stored energy in the chloroplasts through a chemical reaction to make glucose

• The sugar is moved through tubes in the leaf to the roots, stems and fruits of the plants

• Some of the sugar is used right away by the plant for energy; some is stored as starch; and some is built into plant tissue (example: cellulose)

Why is this important to us?

1. Because we cannot make our own food

(glucose, energy),

we must get our food from plants.

Plants are the first step in the food chain.

Why is this important to us?

2. The oxygen released during photosynthesis is necessary for all living things.

Why do we need oxygen?

For energy . . .We “burn up” our food. (OXIDATION REACTION)

Summary

• Location: Location: chloroplasts of green plant cells

• Reactants: Reactants: CO2 and H2O

• Catalysts: Catalysts: light energy and chloroplasts

• Main Product: Main Product: glucose

• By-product: By-product: oxygen

• Includes: Includes: light reaction and

light-independent reaction (Calvin cycle)

Chemosynthesis

• Bacterial process

• Uses chemicals as energy source instead of light to make food (carbohydrates)

• Occurs in such places as bottom of the ocean around vents

What is Cellular Respiration?

Once the energy that was in sunlight is changed into chemical energy by photosynthesis, an organism has to transform the chemical energy into a form that can be used by the organism.

This process is cellular respiration.

What is Cellular Respiration?

The release of chemical energy for use by cells.

In what cell part does this occur in eukaryotic cells?

The mitochondria

Describe Cellular Respiration

• The breakdown of glucose molecules to release energy

• Takes place in all living things

• Is a step by step process

What is the chemical equation for cellular respiration?

What two processes make up cellular respiration?

• The anaerobic phaseanaerobic phase

takes place first in the cytoplasm

• The aerobic phaseaerobic phase

follows the anaerobic phase and takes place in the mitochondriamitochondria

The Anaerobic Phase

• First step occurs in the cytoplasm

• Glucose breaks down into pyruvate

(two 3 carbon sugars)

• This is called “GLYCOLYSIS”

• 2 ATPs produced (net gain)

The Aerobic Phase

• Pyruvate enters the mitochondria

• Includes a series of reactions called the Krebs cycle

• Another part of this process is the “electron transport chain” - a series of reactions that end with oxygen

• 34 ATPs produced

Summary

• Location: Location: mitochondriamitochondria of all eukaryoticeukaryotic cells

• Reactants: Reactants: glucoseglucose and oxygenoxygen

• Catalysts: Catalysts: enzymesenzymes

• Main Product: Main Product: energy (ATPs)energy (ATPs)

• By-products: By-products: COCO22 and HH22OO

• Includes: Includes: anaerobic anaerobic and and aerobic phasesaerobic phases

Together, what do photosynthesis and respiration

form???

THE CARBON CYCLETHE CARBON CYCLE

So what happens in bacteria and yeast?

What is FERMENTATION?

Fermentation

• Two types:– Alcoholic fermentation:

• Yeast - 2 ATPs

• C6H12O6 -> CO2 + ethyl alcohol + energy(2ATPs)

• Lactic Acid fermentation

bacteria and muscle cells (without O2) - 2 ATPs

C6H12O6 -> lactic acid + energy (2 ATPs)

Photosynthesis Photosynthesis &&

RespirationRespiration

THE ENDTHE END