B-3.1: SUMMARIZE PHOTOSYNTHESIS & INTERPRET THE FORMULA

PHOTOSYNTHESIS 1

CHAPTER 8 SECTION 1 Essential Question:

What is the role of ATP in cellular activity?

SC B- 3.3:recognize the overall structure of ATP, namely, adenine, the sugar ribose, & three phosphate groups – and summarize its function(including ATP-ADP cycle

PHOTOSYNTHESIS

AUTOTROPHS HETEROTROPHS Organisms that can

make their own food (energy source) plants some bacteria algae

Organisms that cannot make their own food; they have to consume food (energy source) Animals

have to eat other organisms

Fungi decomposers

AUTOTROPHS HETEROTROPHS

DRAW & LABEL FIGURE 8-3 ON PAGE 203 ONTO TOP ½ 0F PAGE 53 OF NOTEBOOK

ATPAdenosine

Triphosphate is the

principle chemical

compound cells use to store and release energy

ATP ADP + P releasing energy in the 3rd phosphate bond. This is a reversible reaction:

ADP + P ATP

PHOTOSYNTHESIS OVERVIEWCHAPTER 8-2

EQ: How would you describe the relationship between chlorophyll and the color of plants?

Photosynthesis uses the energy in sunlight and carbon dioxide from the air to make glucose and releases oxygen into the air.

Draw, color, label figure 8-4 from page 206 on page 55 of your notebook

Pigments are also a necessary part of photosynthesis.Pigment: any light absorbing moleculeChlorophyll: principle pigment of plants; absorbs light energy

PHOTOSYNTHESIS REACTIONSCHAPTER 8-3

EQ: What happens in the light reactions of photosynthesis?

Inside a Chloroplast:thylakoids: saclike membrane folds; appear like coinsgranum: stack of thylakoidsstroma: space between granum and inner membrane

PHOTOSYSTEMS• clusters of pigments in thylakoid membrane that capture energy from light•Photosystem I & II

NOTICE THIS IS HAPPENING IN THE THYLAKOID MEMBRANE

LIGHT REACTIONS Use energy from light to

excite electrons. Electrons absorb energy from light and go from their ground state to their excited state. These excited electrons then jump out of that atom & move through a series of molecules called the electron transport chain

LIGHT REACTIONS: STEP 1 Photosynthesis begins when photons

of light are absorbed by pigments in Photosystem II

Ground state electron excited electrons enter electron transport chain

The electrons that left must be replaced: Enzymes breakdown 2 water 4H+ + O2 + 4 electrons

LIGHT REACTIONS: STEP 2 The excited electrons move thru the

electron transport chain to Photosystem I Their energy is used to move H+ from

the stroma to inner thylakoid space

Light Reactions: Step 3( in Photosystem I now)

One of the electron carrier molecules is NADP+

NADP+ carries 2 excited electrons with a H+

In the process NADP+ NADPH thus converting some of the light energy into chemical energy

NADPH carries excited electrons to other molecules

LIGHT REACTIONS: STEP 4 Over time the inside of the thylakoid

membrane fills with H+ making the outside of the membrane relatively negative compared to the inside (creating a difference in charge across the membrane)

The difference in charges provides energy to make ATP

LIGHT REACTIONS: STEP 5 The thylakoid membrane is

impermeable to H+ Membrane protein called ATP synthase

allows H+ to pass through membrane As H+ is passing through ATP synthase

changes shape & in the process binds ADP + P ATP

OVERVIEW OF LIGHT REACTIONS Things required

Light Water NADP+ ADP + P

Things produced Oxygen NADPH ATP

LIGHT REACTIONS ANIMATIONS Harvesting Light Photosynthetic Electron Transport and A

TP Synthesis

TIME FOR THOUGHT How would you compare the role of

Photosystem II and Photosystem I

LIGHT-INDEPENDENT REACTIONS aka:

Thermochemical cycle

Calvin Cycle

LIGHT-INDEPENDENT REACTIONS: PART 1

6 carbon dioxide molecules enter chloroplast from atmosphere

Each combines with a 5-carbon sugar which then splits (12) 3-carbon molecules

LIGHT-INDEPENDENTREACTIONS: PART 2

Energy source for Dark reactions is the ATP made in light reactions

H added to carbon molecules is from NADPH made in light reactions

LIGHT-INDEPENDENT REACTIONS: PART 3

2 of the (12) 3-carbon molecules leave the cycle & are used by the plant to make compounds needed by the plant for metabolism and growth

LIGHT-INDEPENDENT REACTIONS: PART 4

(10) C-C-C + 6 ATP (6) C-C-C-C-C + 6 ADP

The remaining (10) 3-carbon molecules are converted back into 5-carbon sugars in a series of reactions powered by 6 ATP

These are used in the next turn of the cycle

LIGHT-INDEPENDENT REACTIONS OVERVIEW

Things required: 6 CO2 18 ATP 12 NADPH

Things produced: 1 glucose (6-

carbon) 18 ADP 12 NADP+

PHOTOSYNTHESIS EQUATION

FACTORS AFFECTING PHOTOSYNTHESIS

availability of water

1. too much2. too little

temperature1. Photosynthesis

enzymes work best 0 ◦C – 35 ◦C

FACTORS AFFECTING RATE OF PHOTOSYNTHESIS-2

3. light intensityas it increases rate of photosynthesis increases but only to a certain point, then it levels off

RAINFORESTS About 2 ½ acres of

Amazon rainforest absorbs 1 ton of CO2 per year

20% of world’s O2 produced in Amazon