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Photosynthesis
Energy & LifePhotosynthesis is the process of capturing and transforming the energy of sunlight into chemical energy. (What type of organisms can make their own food?)
a. Autotrophs – organisms that can make their own food
b. Heterotrophs – organisms that obtain energy from the food they
consume
Energy & LifeChemical Energy and ATP
a. ATP – energy molecule used by cells (Fig. 8-2)
b. Energy is stored in the bonds between phosphate
c. When these bonds are broken energy is released
Energy & Life
Energy & LifeUsing Biochemical Energy
a. Active Transporthttp://www.dnatube.com/video/359/Active-Transport
b. Motor proteins move organelles throughout the cellhttps://www.youtube.com/watch?v=y-uuk4Pr2i8c. Synthesize various molecules
Photosynthesis: An OverviewI. Understand the
significance of Helmont’s,
Priestley’s, and Ingenhousz’s experiments.
II. 6CO2 + 6H2 O C6 H12 O6 + 6O2
Photosynthesis: An OverviewIII.Light and Pigments (Fig. 8-5)
A. Wavelength – distance between crests; shorter wavelengths have higher energy than longer wavelengths
Photosynthesis: An Overviewhttps://www.youtube.com/watch?v=
wJDlxp17rY4
Photosynthesis: An OverviewIII.Light and Pigments (Fig. 8-5)
B. Photon – a particle of lightC. In photosynthetic organisms,
absorbed energy is used to make chemical energy (glucose)D. Photosynthetic pigment – molecule that absorbs light (color you see is the color being reflected)
1. chlorophyll a - primary pigment; converts light energy to chemical energy
Photosynthesis: An OverviewIII.Light and Pigments (Fig. 8-5)
D. Photosynthetic pigment (con’t)
1. chlorophyll a - (con’t)a. reflects green lightb. absorbs red & blue
lightc. normally hides other pigments
2. Chlorophyll b – accessory pigment; absorbs light
andtransfers the energy tochlorophyll a
Photosynthesis: An OverviewIII.Light and Pigments (Fig. 8-5)
D. Photosynthetic pigment (con’t)
3. carotenes & xanthophylls –
accessory pigment; colors
can be seen in autumn when
chlorophylls start to break
downE. Absorption spectrum – the different
colors (wavelengths) of lightabsorbed by each pigment
Reactions of PhotosynthesisI. Inside a chloroplast – organelle
in which photosynthesis occurs
Reactions of PhotosynthesisI. Inside a chloroplast
A. Thylakoids – flattened sacs of photosynthetic membranes; pigments and proteins are organized into photosystems in order for light energy to be captured & stored as chemical energyB. grana – stacks of thylakoidsC. stroma – region between grana
Reactions of PhotosynthesisII. Electron Carriers – molecules
that can accept a pair of high-energy electrons and protons and transfer them to another molecule (NADP+)
Reactions of PhotosynthesisThere are two sets of reactions that take
place within the chloroplasts: The light dependent reactions & the Calvin Cycle (also know as the light independent or the dark cycle)
Reactions of PhotosynthesisIII.Light Dependent Reactions
A. Takes place only in the presence of lightB. Occurs on membranes of thylakoidsC. Produces high energy compounds that are used in the dark reaction: ATP and NADPHD. Photosystem II
1. pigments absorb light energy and electrons are boosted to a higher energy level
Reactions of PhotosynthesisIII.Light Dependent Reactions
D. Photosystem II (con’t)2. lost electrons are
replaced by the splitting of H2O into 2 e- ,2 p+, and O2
a. electrons are picked up by NADP
b. protons (H+) are pumped into inner thylakoid space
Reactions of PhotosynthesisIII.Light Dependent Reactions
D. Photosystem II (con’t) c. Flow of hydrogen
ions down their gradient provides the energy necessary to synthesize ATP: ATP is used to
power the Calvin cycle
Reactions of PhotosynthesisIII.Light Dependent Reactions
E. Photosystem I1. pigments use energy
from light to re-energize the elctrons from photosystem II
2. produces NADPH which also powers the Calvin Cycle
Reactions of PhotosynthesisIII.Light Dependent Reactions
https://www.youtube.com/watch?v=hj_WKgnL6MI
Reactions of PhotosynthesisIV.The Calvin Cycle – (light
independent, dark reaction) – uses ATP and NADPH from the light dependent reactions to produce high energy sugars (Fig. 8-11)
A. Takes place with or without the presence of light as long as ATP and NADPH are availableB. Occurs in the stroma chloroplastC. 6CO2 molecules enter the cycle from the atmosphere and combine with 6 five carbon
molecules
Reactions of PhotosynthesisIV.The Calvin Cycle (con’t)
D. The resulting 12 three carbon molecules use the energy from ATP and NADPH to produce 12 high energy three carbon
moleculesE. 2 of these molecules are used to synthesize sugar and other compoundsF. The remaining 10 molecules are used to produce more of the “starting” 6 carbon molecule of the cycle
The Calvin Cyclehttps://www.youtube.com/watch?v=wJDlxp17rY4
Reactions of PhotosynthesisV. Factors Affecting
PhotosynthesisA. Light intensity – as intensity
increases the rate of photosynthesis increases (up to a point)B. Temperature – photosynthesis occurs rapidly at specific temp.; extreme temps. are damaging to enzymesC. H2O – decrease in water slows rate of photosynthesisD. Minerals – must be present in certain amounts