Section 4-2 : Photosynthesis The SUN provides almost all the energy used by living things!

Plants use energy from the sun to convert CO2 and water into oxygen and sugars- primarily glucose.

Photosynthesis is a 2 stage process: Capture the sun’s energy * occurs in the leaves and other green parts of plant

Chloroplasts in plant cells give them their green color because they contain the green pigment chlorophyll.

Each cell has about 30-40 chloroplasts.

Did You Know ….. Chloroplasts may also contain other yellow and orange pigments. These are usually masked by the large amount of green present- until Fall

The pigments capture the light energy and use it to power the second stage of photosynthesis.

2. Make the Food: The cell uses captured light energy to produce food.

There are 2 raw materials needed:. a There are 2 raw materials needed: a. water (that enters plant cells from roots) b. CO2 that enters through stomata (holes on the bottom side of leaves)

These ingredients move into chloroplasts and become oxygen and glucose when mixed with light energy. The light energy is the catalyst that starts the chemical reaction.

When glucose (a sugar/carbohydrate) is formed, the energy from it is used to carry out the functions of the cell.

This equation explains photosynthesis: CO2 + 6 H2O C6H12O6 + 6 O2 The equation is balanced: C – 6 C – 6 H – 12 H – 12 O – 18 O - 18

Photosynthesis is also essential for the air you breathe! 21% of our atmosphere is oxygen thanks to plants.

Respiration When cells need energy, they “withdraw” energy from glucose through cellular respiration. Most complex organisms, such as animals, obtain energy through cellular respiration.

Glucose molecules are broken into smaller molecules in cytoplasm Respiration is a 2 stage process: Stage 1. Glucose molecules are broken into smaller molecules in cytoplasm (no oxygen yet!)

Stage 2. Small molecules are broken down even more with the addition of oxygen in the mitochondria. Lots of energy is released!

In animals – most of the energy released maintains body temperature. Some of the energy is used to form ATP (adenosine triphosphate). ATP supplies energy that fuels cell activity.

Photosynthesis happens in chloroplasts. Respiration Happens in Mitochondria.

This equation explains respiration: C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy This is also a balanced equation if you count the total atoms of each element on each side of the equation.

Photosynthesis and Respiration are reciprocal equations. They work together to keep the levels of carbon dioxide and oxygen fairly constant in the atmosphere.

Fermentation provides energy for cells without using oxygen. The amount of energy released is lower than in respiration. There are two types of fermentation: 1. Alcoholic Fermentation 2. Lactic Acid Fermentation

Alcoholic Fermentation *Occurs in yeast and some single-celled organisms. Alcohol and carbon dioxide are products made when these organisms break down sugars. These products are important to bakers and brewers. The carbon dioxide produced causes dough to rise and is the source of bubbles in alcoholic drinks.

Lactic Acid Fermentation Used when your muscle cells use up oxygen faster than it could be replaced. Fermentation is used to produce energy in this situation. One product of this is lactic acid that builds up making your muscles feel weak, tired, and sore.