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Students are required to read the textbook for the instructor to be able to teach the concepts the course encompasses. (From FOUNDATION SKILLS in the Biology Department Master Syllabus.)Students, do not just read these notes, to succeed in this class -- at least if you wish to have a high grade, you MUST use your textbook as a LEARNING TOOL!
MAIN TOPICS OUTLINE
6.1 ENERGY IN LIVING SYSTEMS
6.11 Major Metabolic Energy-Transforming Pathways6.12 Energy Converting Organelles6.13 Combustion vs. Electron Fall6.14 Cellular Respiration / Photosynthesis Relationship 6.2 PHOTOSYNTHESIS
6.21 Photosynthesis Overview6.22 Nature of Sunlight (Electromagnetic spectrum / Chlorophyll)6.23 Photosynthesis: Light Dependent Reaction (“light reaction”)6.24 Photosynthesis: Light Independent Reaction (“dark reaction”)LECTURE OBJECTIVES:
AT THE END OF THIS LECTURE, YOU SHOULD BE ABLE TO:
1. Give the overall equation for photosynthesis and contrast it to that for cellular respiration, recognize that photosynthesis and cellular respiration are linked in a chemical cycle. (Note that the photosynthesis is the reverse of cellular respiration.)
2. Associate the major parts of photosynthesis with the structure of the chloroplast.
3. Understand that pigments capture wavelengths of light and energize electrons.
4. List the raw materials and products of photosynthesis: know the steps of the Light Dependent and Light Independent reactions, know the raw material needed to start each phase and know the products made by each phase.
5. Explain how autotrophs use the intermediates as well as the products of photosynthesis in their own metabolism.
6. Define selected key terms.
Key Termsdef. Absorption spectrum: A pigment's ability to absorb various wavelengths of light.
def. ATP(Adenosine Triphosphate): An adenine containing molecule with triphosphate chain that releases energy when its phosphate bond is broken.
def. Autotrophs: Organisms capable of producing its own food from inorganic materials and using sunlight as energy source to do so.
def. Carbon dioxide fixation: The first enzyme mediated step in the Calvin Cycle of the photosynthesis.
def. Chlorophyll: Green pigment located in the chloroplasts associated with trapping light energy.
def. Chloroplast: An sac-like membranous energy transforming organelle in plants and certain protistans, containing chlorophyll, that serves as the site of photosynthesis.
def. Electromagnetic spectrum: The entire spectrum of radiation, ranging in wavelengths from less than a nanometer to more than a kilometer. (Including, but not all, in order of decreasing frequency gamma rays, x-rays, UV-rays, visible light, infrared rays, microwaves, radio waves, and heat.)
def. Energy: the capacity to do work (something an object has that enables it to do work).
def. Granum (pl. grana): Stack of chlorophyll containing thylakoids in a chloroplast.
def. Heterotrophs: Organisms incapable of producing its own food, and therefore depend directly or indirectly on producers to meet their food requirements.
def. Light-dependent reaction (Light reaction, Light-energy conversion stage): The first of the two stages of photosynthesis, during which light energy is converted to chemical-bond energy.
def. Light-independent reaction (Dark reaction, Calvin Cycle, Carbon dioxide conversion stage): The second of the two stages of photosynthesis, during which inorganic carbon from carbon dioxide in the atmosphere becomes incorporated into a sugar molecule.
def. Mitochondrion: An membranous energy converting organelle in all eukaryotic cells, resembling a small bag with a larger bag inside that is folded back on itself, that serves as the site of aerobic cellular respiration.
def. Photon: Light energy, regarded as a discrete particle having zero mass, and no electrical charge.
def. Photosynthesis: The conversion of light energy to chemical energy (stored in the glucose produced by the chemical reaction) from carbon dioxide and water.
def. Stroma: Inner fluid filled compartment in a chloroplast containing enzymes used in photosynthesis.
def. Thylakoid: Sac in a granum whose membranes contains chlorophyll and where the light-dependent reactions of photosynthesis occur.
def. Visible light: The portion of the electromagnetic spectrum detected as various colors by the human eye, ranging in wavelengths from about 400nm to about 700nm.
6.1 ENERGY IN LIVING SYSTEMS (Intro. to Metabolic Pathways)
• 6.11 Major Metabolic Energy-transforming Pathways
• All living organisms require energy to function and survive.
• Energy in living things = ATP.
I. Some organisms -- autotrophs, can trap sunlight in the process of photosynthesis to:
a. manufacture (synthesize) ATP.
b. use ATP to:
perform necessary chemical reactions in the plant cells for:
i. growth (make plant building blocks = mostly carbohydrates -- "glucose")
ii. maintenance ( " )
iii. reproduction
1. Photosynthesis
Light energy + 6CO2 + 6H2O ---> C6H12O6 + 6O2
II. Other organisms -- heterotrophs, must "eat food" and rely on a chemical process called cellular respiration, to:
a. transfer energy from chemical bonds in organic compounds -- "glucose"
b. produce ATP, which can be used for cellular work.
(At each energy transfer some energy is lost as heat.)
2. Cellular Respiration
C6H12O6 + 6O2 ---> 6CO2 + 6H2O + 36ATP
• 6.12 Energy Converting Organelles
-- in plants: mitochondria and chloroplasts
-- in animals: mitochondria
--- Mitochondrion
-- site of aerobic cellular respiration
(series of reactions releasing usable energy from food)
--- Chloroplast
-- site of photosynthesis
(contains the pigment chlorophyll)
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• 6.13 Combustion vs Electron fall
• Cellular respiration does not break down glucose in a single step -- as a car with gasoline.
-- broken down gradually in a series of steps
-- each step is catalyzed by a specific enzyme
• Combustion vs. electron fall
1. Gasoline oxidation (combustion)
EXPLOSIVE ONE STEP
• Car engine
Gasoline + oxygen ---> CO2 + H2O + Energy (75% Heat)
= 25% efficiency
2. Glucose oxidation (cellular respiration)
MANY STEPS, ENZYME MEDIATED, ELECTRON FALL
• Living cells
Glucose + oxygen ---> 6CO2 + 6H2O + 36ATP (+ heat 60%)
= 40% efficiency
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• 6.14. Cellular Respiration / Photosynthesis relationship
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6.2 PHOTOSYNTHESIS
• 6.21 Nature of Sunlight (Electromagnetic Spectrum / Chlorophyll)
• Electromagnetic spectrum: the entire range of radiation
-- gamma rays, x rays, UV light, visible light, infrared light, microwaves, radio waves
• Visible light: the range of radiation most important to life, detected as various colors by the human eye
-- wavelengths: 380 - 750 nm
-- colors: violet - red
Electromagnetic spectrum:
Gamma rays (0.001nm)
X-rays (1nm)
Ultra-violet (invisible) (10nm)
Visible light (380nm): Violet (380nm) - Blue (450nm) - Blue-green (500nm) - Green (550nm) - Yellow (600nm) - Orange (650nm) - Light red (700nm) - Dark red (750nm)
Infra-red (invisible) (800nm)
Microwaves (0.01 cm)
Radio waves (above 1 cm)
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-- because green pigment chlorophyll contained in the chloroplasts.
-- because green light reflected.
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-- blue & red light (Englemann's experiment with Spirogyra)
• Most of the chlorophyll is found in the leaves
-- the photosynthetic center.
• 6.22 Photosynthesis Overview
• Autotrophs, can trap sunlight in the process of photosynthesis.
• For most plants, photosynthesis takes place in the leaf -- in the chloroplasts in the leaf cells.
Sunlight + 6CO2 + 6H2O ---> C6H12O6 + 6O2
Sunlight + 6CO2 + 12H2O ---> C6H12O6 + 6O2 + 6H2O
1. Capturing light energy (kinetic energy)
2. Converting light energy to chemical bond energy (potential energy)
3. Use chemical bond energy by 'plants' to 'grow' (=build itself with 'glucose')
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• Photosynthesis is not a single process
I. Light Reaction -- in the thylakoids of the chloroplasts
II. Dark reaction -- in the stroma (matrix) of the chloroplasts
• 6.23 Light-dependent reaction
(Light Reaction, "the photo part")
1. H2O & Light energy Kinetic energy of light photons -- captured
(by the green pigment chlorophyll)
2. Energy transformed
-- Converted to kinetic energy of moving electrons -- NADPH2
-- Converted to chemical bond energy of ATP
3. O2 released (from water -- given off as a by-product to the atmosphere)
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• 6.24 Light-independent Reactions
(Dark Reaction, Calvin Cycle, "the synthesis part")
4. CO2 converted to carbohydrate (carbon fixation) "glucose"
-- ATP used to combine hydrogen (from water)with CO2 (from the atmosphere)
-- Carbon into longer organic compounds (carbon dioxide to glucose)
--- used by the plant to "grow"
-- they need energy (ATP and NADPH2) to grow
-- in most plants the dark reaction occurs during daylight
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