CHAPTER 8: PHOTOSYNTHESIS. 8-1 Energy of Life Energy = Living organisms depend on energy. Living things get energy from _______. The ultimate source of energy is the _____. The ability to do work. food. sun. Autotrophs and Heterotrophs Autotrophs =
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The ability to do work
Organisms that make their own food
Organisms that need to consume
food for energy
Chemical energy (stored in bonds)
The basic energy source (chemical energy) of all cells
3 Phosphate groups
2. Releasing Energy
Small amounts can be stored by adding a
phosphate group to ADP molecules to produce ATP.
The cell can break the high energy bond between
the 2nd and 3rd phosphate group
Figure 8-3 Comparison of ADP and ATP to a Battery
Adenosine diphosphate (ADP) + Phosphate
Adenosine triphosphate (ATP)
Only enough to provide a few seconds of activity.
Carry out active transport
moving organelles throughout the cell
Producing light (ex. fireflys)
Storing large amounts of energy
regenerate ATP when the cell needs it.
through a series of oxidation/reduction reactions.
Process where plants use energy of sunlight
to convert water and carbon dioxide into
and oxygen, a waste product.
6 CO2 + 6H2O + SUNLIGHT→ C6H12O6(SUGAR) + 6O2
6 CO2 + 6H2O + SUNLIGHT → C6H12O6 (SUGAR) + 6O2
LEO: Lose Electrons Oxidation
GER: Gain Electrons Reduction
Oxidation: Lose electrons
Photosynthesis: Reactants and Products
Sugars + O2
CO2 + H2O
“When a tiny seedling grows into
the seedling became a tree.
the mass came from water
“hydrate” in the carbohydrate
portion of photosynthesis
2.3 kg. (5 lb.) plant
90.8 kg (200 lbs). soil
76.8 kg (169 lbs. 3 oz.)
Soil 57 g less
The flame died out.
Flame lasted longer
plants release a substance needed
for candle burning.
plants release oxygen
Light is needed to produce oxygen
carbon’s path to make glucose
and ____ (sun), and ________ (a molecule in chloroplasts).
A mixture of different
Figure 8-5 Chlorophyll Light Absorption
Absorption of Light by
Chlorophyll a and Chlorophyll b
plants appear green)
_________ (in chloroplasts) which makes
QUESTION: So why do plants leaves change color in the fall?
Colorful leaves signal the changes of autumn. As nights grow longer and cooler, the leaves no longer produce chlorophyll, the pigment that makes leaves green and enables the process of photosynthesis. As the green pigment wanes, other pigments take over, producing the brilliant reds, oranges, and yellows of fall foliage.
LEAF CROSS SECTION
Light-dependent reactions (located in thylakoid membranes)
Light-independent reactions (located in stroma)
Figure 8-7 Photosynthesis: An Overview
ADP + P
electrons in chlorophyll.
gain a lot of energy.
a special carrier
Forming an electron transport chain.
Covalent bonds of NADPH are broken to release
the high energy electrons.
Light-Dependent Reactions (Requires Light)· Located in the ___________________________· In the light reaction, ___________ is used to produce _____ and _______http://www.fw.vt.edu/dendro/forestbiology/photosynthesis.swf
Overview of the Light Reaction
Electron Transport Chain
Electron Transport Chain
O2 + 4H+
Electron transport chain
Energy forsynthesis of
Clusters of chlorophyll pigment
ADP and NADP+
Enzyme (protein) that makes ATP
Light Reaction Process:
ELECTRON TRANSPORT CHAIN
A. Photosystem II (PSII) * Absorbs light to 2H2O o e- = o O2 = o H+= B. Electron Transport Chain* The light energy * The electrons get passed
split (break up) water molecules
→ 4H+ + 4e- + O2
Donated to chlorophyll
Released into air providing oxygen for us
Released inside the thylakoid membrane
excites electrons increasing
their energy level.
down an electron transport chain to
photosystem I (PSI)
C. Photosystem I· Light energy energizes electrons.· NADP+ accepts the electrons and an H+ and are used to make _________.D. Hydrogen Ion Movement· When water splits, · The difference in charges http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio05.swf::Proton%20PumpE. ATP Formation· _____ do not cross the membrane directly. It needs the help of a membrane protein.· H+ ions pass through the protein:
H+ ions fill up the inner thylakoid membrane
(making it positively charged). As a result, the
stroma is negatively charged.
Provides the energy to make ATP.
ATP synthase is an enzyme that converts ADP to ATP
PRODUCTS OF THE LIGHT REACTION:·____ : Released in the air· ______________: These contain abundant chemical energy but they are unstable. So, they are used to power the dark reaction to _________________ which can store the energy for longer periods of time.
ATP & NADPH
help build glucose
Section 8-3 D. The Calvin Cycle (dark reaction; light independent) * Occurs in the
Figure 8-11 Calvin Cycle
Stroma with or without light.
CO2 Enters the Cycle
Sugars and other compounds
The Calvin Cycle
(Sugars and other carbohydrates)
6 CO2 combines with 6 5-C compounds
12 3-C compounds
ATP & NADPH (from the light reaction)
convert the 12 3-C compounds into a higher energy form.
PRODUCTS OF THE CALVIN CYCLE (DARK REACTION):*E. Factors Affecting Photosynthesis** Plants often have a ______ coating to protect against ** The greater the _____________, the better photosynthesis functions (up to a point).
High Energy Sugars
Shortage of water can stop/slow down photosynthesis
Very low/high temperatures (damages enzymes) can
stop/slow down photosynthesis (optimal temp.= 0°– 35° C
takes place in
take place in
1a: usable energy is captured from sunlight by chloroplasts and is stored through the synthesis of sugar from carbon dioxide
United Streaming video:
Photosynthesis (13 min)