Light Absorption Sun gives off visible (white) light White light is actually a mixture of ROY G BIV –Red, Orange, Yellow, Green, Blue, Indigo, Violet These colors are either reflected or absorbed by objects We see reflected light –Green leaves = reflect green light

Which color(s) reflects? Yellow Which color(s) absorb? All the others I see yellow bananas.

Which color(s) reflects? Blue Which color(s) absorb? All the others I see a blue balloon.

Most plants have green leaves, which means they: –Reflect green light –Absorb other colors Energy in red and blue light most stimulates photosynthesis Light & Photosynthesis

Defined: process that converts solar energy into glucose Who: Autotrophs (Plants, algae, some bacteria) What: Endergonic chemical reaction –Requires energy End Result: 1.Sugar (glucose) 2.oxygen waste reactantsproducts Photosynthesis O2O2 CO 2

Plants gather the sun’s energy with light absorbing molecules called pigments. The plants’ principal pigment is Chorophyll.

When chlorophyll is struck by sunlight the electrons in the chlorophyll molecule become energized.

Photosynthesis takes place in the chloroplast. Inside the chlorplast are sac like membranes called thylakoids A stack of thylakoids is called a grana

Thylakoids contain clusters of chlorophyll and proteins known as photosystems Photosystems absorb sunlight and generate high energy electrons

ELECTRON CARRIER MOLECULES A compound that can transfer high energy electrons to other molecules. High energy electrons produced by chlorophyll require special carriers called NADP+

NADP+(electron carrier) NADP+ holds 2 high energy electrons along with a hydrogen ion H+ Converts to NADPH (trapped in chemical form) These help build glucose

Where: Thylakoid membranes of chloroplast(pigments located here) What happens? Electrons in chlorophyll become energized 1)Sunlight & enzymes bond ADP with P to make… ATP 2)Water (H 2 O) broken apart Hydrogen kept for later use; Oxygen is released as a waste End result: ATP, NADPH, Oxygen Stage 1: Light Dependent (Light Reactions) H2H2 O H2H2 O H2H2 O H2H2 O Stroma enzymes ADP P P ATP Thylakoids

30 seconds: Discuss with your neighbor 1)Are the products of photosynthesis on the left or right of the arrow? 2)Which reactant(s) are used during the light dependent stage? 3)Which product(s) are created during the light dependent stage? reactants products #2 #3

Stroma Where: Stroma (fluid interior) of chloroplast What happens? A)CO 2 taken in B)ATP & enzymes break apart CO 2 + H2 C)C’s, O’s, and H’s recombine into C 6 H 12 O 6 (Glucose) Stage 2: Light Independent (Dark Reactions) H2H2 H2H2 H2H2 H2H2 ATP CO2 H2H2 H2H2 COO CO O COO C OO COO CO O enzymes HH HHHH HH HH HH What’s the formula for glucose? C6C6 H 12 O6O6

30 seconds: Discuss with your neighbor 1)Which reactant(s) are used during the light independent stage? 2)Which product(s) are created during the light independent stage? reactants products #1 #2

The End Results The 2 sets of photosynthetic reactions work together – The light dependent reactions trap the energy of sun in chemical form and the light independent reactions use that chemical energy to produce stable, high energy sugars from CO2 and water

Factors Affecting Photosynthesis High light intensity increases the rate of photosynthesis. After the light intensity reaches a certain level, however, the plant reaches its maximum rate of photosynthesis, as is seen in the graph.

Water Because water is one the raw materials in photosynthesis, a shortage of water can slow or even stop photosynthesis Water loss can also damage plant tissues

Temperature The reaction of photosynthesis are made possible by enzymes that function best between 0 degrees and 35 degrees C. Temperature above or below may affect those enzymes.

Connection between photosynthesis & respiration Plants –Create glucose through photosynthesis –Glucose is used to make ATP through cellular respiration Plant Cell glucose chloroplast ATP mitochondria

Connection between photosynthesis & respiration Animals –Plants create glucose through photosynthesis –Animals eat the plants –Glucose is used to make ATP through cellular respiration Glucose mitochondria ATP Glucose (from food)

review 1)What is used during the light dependent reactions? 2)What created during the light dependent reactions? 3)What is used during the light independent reactions? 4)What created during the light independent reactions? 5)True or False: Plants are the only photosynthetic organisms.