PHOTOSYNTHESISPhotos (light) + synthesis (put together ormanufature)
Plants… 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
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
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
Chloroplasts (cont’d) 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
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
Words to Know: PhotosynthesisATP - Adenosine TriphosphateADP - Adenosine DiphosphateNADPH- Nicotinamide Adenine Dinucleotide Phosphate (Hydrogen acceptor)Reactant - substances that undergo chemical reactionProduct - outcome of the reaction
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
Two Stages of Photosynthesis:Light Dependent Stage 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.
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.
Light Dependent Stage 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.
Steps: Light Dependent Reaction 1 Light energy is absorbed by 2 Chlorophyll A (becomes an energy carrier) that becomes 3 Energized chlorophyll supplies energy to split combine 4 water 4 phosphate into with 5 ADP to form5 H2 5 O is released that are trapped by 6 ATP6 NADP (H acceptor) forms to be used for dark reaction7 NADPH2 to be used for dark reaction
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.
Light Independent Stage 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.
Steps : Light Independent Reaction 1 6 CO2 molecules combines with 2 RuDP (CO2 acceptor) forms 3 6-C sugar (unstable sugar) splits to form 4 2 molecules of PGA (3- C compound)-called: combines withBiochemical Pathway 5 2H (from light reaction (NADPH)) forms 6 2 molecules of PGAL 6 H2O is converted into by-product used 7 in light reaction RuDP to be reused Glucose to combine with CO2
Comparison of the twoReaction Light DarkSite of Occurence Thylakoid-grana stromaInitial Requirement Light Energy, ATP, NADPH, and(Reactants) water, and CO2, chlorophyll AEnd Product ATP, NADPH, Glucose, water, Oxygen NADP, ADP and inorganic phosphateBoth reactions thus form a cycle in which the reactants:water and carbon dioxide produce oxygen and sugar