PHOTOSYNTHESIS Photos (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 Triphosphate ADP - Adenosine Diphosphate NADPH-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 O H2H2 phosphate combine into that are trapped by NADP NADPH 2 (H acceptor) forms to be used for dark reaction with to form to be used for dark reaction is released 5 6 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 molecules 6 CO 2 molecules combines with RuDP (CO 2 acceptor) forms 6-C sugar (unstablesugar) (unstable sugar) splits to form 2 molecules of PGA (3-Ccompound) (3- C compound) combines with 2 H (from light reaction (NADPH)) forms RuDP H2OH2O 2 molecules of PGAL by-product used in light reaction is converted into Glucose to be reused to be reused to combine with CO called: -called: Biochemical Pathway

Comparison of the two Reaction LightDark Site of Occurence Thylakoid-granastroma Initial Requirement (Reactants) Light Energy, water, and chlorophyll A ATP, NADPH, and CO 2, 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