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8.2 Photosynthesis
How do plants get energy?
What factors affect photosynthesis?
Objectives12a) I can describe the role of ATP in cellular activities.
12b) I can explain where plants get the energy they need to produce food.
13a) I can explain the role of light, pigments, and electron carrier molecules in
photosynthesis.
13b) I can state the overall equation for photosynthesis.
14a) I can describe what happens during the light-dependent and light-independent
reactions.
14b) I can identify factors that affect the rate at which photosynthesis occurs.
15a) I can explain where organisms get the energy they need for life processes.
15b) I can define cellular respiration and compare it to photosynthesis.
16a) I can describe what happens during glycolysis and the Krebs cycle.
16b) I can explain how high energy electrons are used by the electron transport chain
An Overview of Photosynthesis
Photosynthesis uses the energy of sunlight to convert water and carbon
dioxide into high-energy sugars and oxygen.
Overview of Cellular Respiration
If oxygen is available, organisms can obtain energy from food
by a process called cellular respiration. The summary of
cellular respiration is presented below.
In symbols:
6 O2 + C6H12O6 → 6 CO2 + 6 H2O + Energy
In words:
Oxygen + Glucose → Carbon dioxide + Water +
Energy
Lactic Acid Fermentation
● A breakdown of glucose
that creates ATP. Does not
need oxygen.
Ways to break down energy ● Aerobic Respiration- the process of producing cellular
energy involving oxygen.
● Anaerobic Respiration- the process of producing cellular
energy without oxygen.
● Fermentation- a partial breakdown of organic molecules to
produce energy, usually without oxygen.
Lesson Overview Leaves
Stomata - small openings that allow carbon dioxide, water, and oxygen exchange.
Photosynthesis
Lesson Overview Leaves
Guard cells - regulate the movement of gases into and out of leaf tissues.
Chloroplasts
● Chloroplast - organelle where photosynthesis occurs.
● Thylakoid - a photosynthetic structure within the chloroplast.
● Grana - stacks of thylakoids
● Stroma - fluid portion outside of thylakoid
High-Energy Electrons
● NADP+ (nicotinamide adenine
dinucleotide phosphate) is an
energy carrier molecule.
● NADP+ accepts and holds two
high-energy electrons, along with
a hydrogen ion (H+). In this way, it
is converted into NADPH.
● NADPH can then carry the high-
energy electrons to chemical
reactions elsewhere in the cell.
Lets Draw!What is really going on in a chloroplast? (p. 111)
Energy Collection
Because light is a form of energy, any compound that absorbs light absorbs
energy. Chlorophyll absorbs visible light especially well.
When chlorophyll absorbs light, a large fraction of the light energy is transferred
to electrons. These high-energy electrons make photosynthesis work.
Light-Dependent Reactions
● Photosynthesis involves two sets of reactions.
● The first set of reactions is known as the light-dependent reactions
because they require the direct involvement of light and light-absorbing
pigments.
Light-Dependent Reactions
● Light-dependent reactions use energy from sunlight to produce ATP and NADPH.
● These reactions take place within the thylakoid membranes of the chloroplast.
● Water is required as a source of electrons and hydrogen ions. Oxygen is released
as a byproduct.
Light-Independent Reactions
Plants absorb carbon dioxide from the atmosphere and complete the process of
photosynthesis by producing sugars and other carbohydrates.
● Light-independent reactions - ATP and NADPH molecules produced in
the light-dependent reactions are used to produce high-energy sugars from
carbon dioxide.
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