Presentation on theme: "PHOTOSYNTHESIS 6.1. The main form of energy from the sun is in the form of electromagnetic radiation Visible radiation (white light) used for."— Presentation transcript:
The main form of energy from the sun is in the form of electromagnetic radiation Visible radiation (white light) used for photosynthesis Remember : ROY G. BIV?
The electromagnetic spectrum
A Red Object absorbs the blue and green wavelengths and reflects the red wavelengths
Why are plants green?
pigment a compound that absorbs light different pigments absorb different wavelengths of white light. chlorophyll is a pigment that absorbs red & blue light (photons) so green is reflected or transmitted. Chlorophyll is located in the thylakoid membranes So, Plants are green because the green wavelength is reflected, not absorbed.
2 types of chlorophyll Chlorophyll a – involved in light reactions Chlorophyll b – assists in capturing light energy – accessory pigment Carotenoids – accessory pigments – captures more light energy Red, orange & yellow
The electromagnetic wavelengths and the wavelengths that are absorbed by the chlorophyll
During the fall, what causes the leaves to change colors?
Fall Colors In addition to the chlorophyll pigments, there are other pigments present During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments Carotenoids are pigments that are either red, orange, or yellow
Photosynthesis is - conversion of light energy into chemical energy that is stored in organic compounds (carbohydrates > glucose) Used by autotrophs such as: Plants Algae Some bacteria (prokaryotes)
glucose - energy-rich chemical produced through photosynthesis C 6 H 12 O 6 Biochemical pathway – series of reactions where the product of one reaction is consumed in the next E.g. photosynthesis product is glucose which is used in cellular respiration to make ATP (carbohydrate)
Remember Redox Reaction reduction/oxidation The transfer of one or more electrons from one reactant to another Two types: 1.Oxidation is the loss of e - 2.Reduction is the gain of e -
Oxidation Reaction The loss of electrons from a substance or the gain of oxygen. glucose 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Oxidation Carbon dioxide Water Oxygen
Reduction Reaction The gain of electrons to a substance or the loss of oxygen. glucose 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Reduction
Photosynthesis equation Light energy 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Chlorophyll Reactants: Carbon dioxide and water : glucose and oxygen which is a byproduct Products: glucose and oxygen which is a byproduct
Where does photosynthesis take place?
Plants Mainly occurs in the leaves: a.stoma - pores b.mesophyll cells Stoma Mesophyll Cell Chloroplast
Mesophyll Cell of Leaf Cell Wall Nucleus Chloroplast Central Vacuole Photosynthesis occurs in these cells!
Stomata (stoma) Pores in a plant’s cuticle through which water vapor and gases (CO 2 & O 2 ) are exchanged between the plant and the atmosphere. Guard Cell Carbon Dioxide (CO 2 ) Oxygen (O 2 ) Found on the underside of leaves Stoma
Chloroplast Organelle where photosynthesis takes place. Granum Thylakoid Stroma Outer Membrane Inner Membrane Thylakoid stacks are connected together
Parts chloroplasts – dbl membrane organelle that absorbs light energy Thylakoids – flattened sacs contain pigment - chlorophyll Grana (pl: granum) – layered thylakoids (like pancakes) Stroma – solution around thylakoids Stomata – pore on underside of leaf where O 2 is released and CO 2 enters Stroma : chloroplast :: cytosol : cytoplasm
Thylakoid Thylakoid Membrane Thylakoid Space Granum Grana make up the inner membrane
What do cells use for energy?
Energy for Life on Earth Sunlight is the ULTIMATE energy for all life on Earth Plants store energy in the chemical bonds of sugars Chemical energy is released as ATP during cellular respiration
Structure of ATP ATP stands for adenosine triphosphate It is composed of the nitrogen base ADENINE, the pentose (5C) sugar RIBOSE, and three PHOSPHATE groups The LAST phosphate group is bonded with a HIGH ENERGY chemical bond This bond can be BROKEN to release ENERGY for CELLS to use
Removing a Phosphate from ATP Breaking the LAST PHOSPHATE bond from ATP, will --- Release ENERGY for cells to use Form ADP (adenosine diphosphate) Produce a FREE PHOSPHATE GROUP
High Energy Phosphate Bond
FREE PHOSPHATE can be re-attached to ADP reforming ATP Process called Phosphorylation
Photosynthesis 1. Light Reaction - Produces energy from solar power (photons) in the form of ATP and NADPH. 2. Calvin Cycle Also called Carbon Fixation or Carbon Cycle, Uses energy (ATP and NADPH) from light reaction to make sugar (glucose). SUN
3 stages of photosynthesis-
Stages: STAGE 1 - LIGHT REACTIONS - energy from sun is used to split water into H+ an O2 STAGE 2 – energy is converted to chemical energy & stored in ATP & NADPH in stroma STAGE 3 - CALVIN CYCLE where carbon is fixed into glucose
Light Reaction (Electron Flow) Occurs in the Thylakoid membranes 2 possible routes for electron flow: Use Photosystem I and Electron Transport Chain (ETC) and generate ATP only OR use Photosystem II and Photosystem I with ETC and generate O 2, ATP and NADPH
ELECTRON TRANSPORT - LIGHT REACTIONS in 5 steps
Photosystem I and II Step 1 – light excites e- in photosystem II Step 2 – e- move to primary e- acceptor Step 3 – e- move along electron transport chain (etc) Step 4 – light excites e- in photosystem I Step 5 – e- move along 2 nd (etc) End – NADP+ combine H+ to make NADPH
Electron transport chain song Play the "Come On Down (The Electron Transport Chain)" song performed by Sam Reid. Play the "Come On Down (The Electron Transport Chain)" song performed by Sam Reid. Come On Down (The Electron Transport Chain)Come On Down (The Electron Transport Chain)
Photolysis –photo-chemical splitting of water (restoring photosystem II)
Chemiosmosis – synthesis of ATP Powers ATP synthesis Takes place across the thylakoid membrane Uses ETC and ATP synthase H+ move down their concentration gradient forming ATP from ADP Concentration of protons is greater in thylakoid than stroma
The Calvin Cycle 6.2
Calvin Cycle - Biochemical pathway in photosynthesis that produces organic compounds using ATP & NADPH Carbon fixation – carbon atoms from CO 2 are bonded or ‘fixed’ into carbohydrates occurs in stroma
Calvin Cycle Carbon Fixation C 3 plants (80% of plants on earth) Occurs in the stroma Uses ATP and NADPH from light reaction as energy Uses CO 2 To produce glucose: it takes 6 turns and uses 18 ATP and 12 NADPH.
Step 1 - CO 2 diffuses fr cytosol & combines with RuBP which splits into pair of PGA
Step 2 - PGA gets phosphate gr fr ATP gets proton fr NADPH to become PGAL Reaction produces: ADP, NADP+ & phosphate to be used again
Step 3 - PGAL converts back to RuBP Allows Calvin cycle to continue
Alternates: C 3 plants – use Calvin cycle exclusively Form 3-carbon compounds C 4 pathway – evolved in hot, dry climate Form 4-carbon compounds Partially close stomata E.g. Corn, sugar cane, crabgrass CAM – open stomata at night, close in day Grow slow, lose less water E.g. cactus, pineapple
C 4 Plants Mesophyll Cell CO 2 C-C-C PEP C-C-C-C Malate-4C sugar ATP Bundle Sheath Cell C-C-C Pyruvic Acid C-C-C-C CO 2 C3C3 Malate Transported glucose Vascular Tissue
CAM Plants Hot, dry environments 5% of plants (cactus and ice plants) Stomates closed during day Stomates open during the night Light reaction - occurs during the day Calvin Cycle - occurs when CO 2 is present
CAM Plants Night (Stomates Open)Day (Stomates Closed) Vacuole C-C-C-C Malate C-C-C-C Malate C-C-C-C CO 2 C3C3 C-C-C Pyruvic acid ATP C-C-C PEP glucose
Rate of photosynthesis is effected by - light intensity, CO 2 or temperature High intensity or high CO 2 = high rate Growth graph levels off (plateau) High temp = initial high rate but peaks Rate drops when stomata closes
Recap Photosynthesis converts light energy into chemical energy thru series of biochemical pathways Electrons excite in photosystem II – move along ETC to photosystem I electrons are replaced when water is split oxygen is byproduct ATP synthesized across thylakoid Calvin cycle – carbon is fixed & sugar produced 3 turns produce PGAL (PGAL keeps cycle going Other pathways – C 3, C 4, CAM