PHOTOSYNTHESISPhotos (light) + synthesis (put together or manufature)

Harness energy from the sun through chloroplasts

Then store the energy converted into carbohydrate molecules in the cell wall and vacuoles

Undergo PHOTOSYNTHESIS - the process by which plants convert energy from the sun to provide energy for themselves and almost all life forms

Plants…

Photosynthesis…

Allows plants to create organic molecules they use as fuel.

Basis of all food chains Occurs mostly in LEAVES, which

are the main organs for photosynthesis

Photosynthesis

Chloroplasts Organelles specialized for

photosynthesis Have two membranes

surrounding the liquid in its interior called the STROMA

Inside the inner membrane are series of flattened interconnected sacs called GRANA

Each of these flattened sacs is called a THYLAKOID

A closer look at the thylakoid will reveal its membrane separating it with the stroma or the liquid part of the chloroplast – it is in this membrane that light trapping molecules are located

LIGHT DEPENDENT REACTION of photosynthesis – aka PHOTOCHEMICAL STAGE occurs in thylakoid membrane (because of the

light trapping molecules) LIGHT INDEPENDENT REACTION of

photosynthesis – aka DARK REACTION/CALVIN CYCLE occurs in the stroma

Chloroplasts (cont’d)

Photosynthesis LIGHT and WATER are needed to

perform this process (sun heats water in plant leaves)

Chlorophyll in chloroplasts (scattered throughout each plant cell), absorb energy in the form of light from the sun

Plants take in carbon dioxide – obtained through tiny openings known as stomata

Plants absorb water and nutrients dissolved in the soil through their root system and its network of conducting cells called xylem vessels

ATP - Adenosine TriphosphateADP - Adenosine DiphosphateNADPH- Nicotinamide Adenine

Dinucleotide Phosphate(Hydrogen acceptor)

Reactant - substances that undergo chemical reaction

Product - outcome of the reaction

Words to Know: Photosynthesis

Photosynthesis Equation

Photosynthesis Is the reverse of the reactions

that occur in animals during cellular respiration

CELLULAR RESPIRATION – the splitting apart of glucose by water to produce carbon dioxide and energy

PHOTOSYNTHESIS – the splitting apart of water by energy to produce glucose from carbon dioxide, with oxygen given off

Occurs in thylakoid membrane Energy from the sun (light energy) is

absorbed by the chlorophyll and then converted into chemical energy.

Light energy is needed to split the water molecules into hydrogen and oxygen.

Oxygen is released as a waste product. These reactions are called

photochemical light reactions because they require light to occur.

Two Stages of Photosynthesis: Light Dependent Stage

Light Dependent Stage Involves two groups of light

absorbing molecules found in the thylakoid membranes: Photosystem I and Photosystem II

Both capture solar energy to energize electrons.

Both cooperate in the light reactions.

Photosystem II functions first.

When excited by light from the sun, chlorophylls release energized electrons. The photosystems transfer the energized electrons to electron transport chains.

Electrons in Photosystems II that were shuttled to Photosystem I provide energy to make ATP.

Electrons from Photosystem I reduce the coenzyme NADP+ (NAD = Nicotinamide adenine dinucleotide) to NADPH.

Photosystem II regains electrons by splitting water and releasing oxygen.

Light Dependent Stage

Steps: Light Dependent Reaction

Light energy

Chlorophyll A (becomes an energy carrier)

that becomes Energized chlorophyll

split

water

ATP

ADP

OH2

phosphate

combine

into

that are trapped by

NADP

NADPH2

(H acceptor)forms

to be used for dark reaction

withto form

to be used for dark reaction

1

2

3

4 4

5

7

6

5 is released56

is absorbed by

supplies energy to

Light Independent Stage Second stage of photosynthesis Formation of glucose from

carbon dioxide doesn’t directly require light.

Aka Calvin Cycle for Melvin Calvin

Occurs in stroma Consists of cyclical series of

reactions that assembles sugar molecules from carbon dioxide and the energy-containing products of the light-dependent reaction with the aid of enzymes.

In the stroma, the enzymes combine carbon dioxide with ribulose phosphate (RuBP) which is a five-carbon sugar and produce glyceraldehydes-three-phosphate (G-3-P), an energy-rich, three-carbon sugar formed by the splitting of sugar.

G-3-P can be used by a plant cell to make glucose and other organic molecules.

The glucose produced during photosynthesis is used by plans as fuel for cellular respiration, and starting material to make cellulose.

Excess sugar is combined with a large carbohydrate molecule and stored as starch in their roots, tubers or fruits.

Light Independent Stage

Steps : Light Independent Reaction

6 CO2 molecules

combines with

RuDP (CO2 acceptor)

forms

6-C sugar (unstable sugar)

splits to form2 molecules of PGA (3- C compound)

combines with2 H (from light reaction (NADPH))

forms

RuDP

H2O2 molecules of PGAL

by-product used in light reaction

is converted into

Glucose to be reusedto combine with CO2

1

2

5

3

4

66

7

-called:Biochemical Pathway

Comparison of the two

Reaction Light DarkSite of Occurence

Thylakoid-grana

stroma

Initial Requirement (Reactants)

Light Energy, water, and chlorophyll A

ATP, NADPH, and CO2,

End Product ATP, NADPH, Oxygen

Glucose, water, NADP, ADP and inorganic phosphate

Both reactions thus form a cycle in which the reactants: water and carbon dioxide produce oxygen and sugar (glucose) as products

Plants need: Carbon dioxide Water Oxygen (for cellular respiration) Hydrogen Nitrogen Potassium Phosphorus Calcium Magnesium Sulfur Boron Copper Iron Molybdenum Zinc