Download Chapter 5 Notes:

Chapter 5 Notes:
Photosynthesis:
A. Facts
A. Photosynthesis Transforms Solar Energy into the chemical bond
energy of Glucose
B. Organic molecules built by photosynthesis provide both the building
blocks and energy for cells.
C. Plants use the raw materials: carbon dioxide and water
D. Chloroplasts carry out photosynthesis
E. Chlorophylls and other pigments involved in absorption of solar
energy reside within thylakoid membranes of chloroplasts
F. Enzymes are specialized proteins that are necessary for metabolic
processes like PHOTOSYNTHESIS because they lower the activation
energy needed and control the rate of reaction.
B. Plants as Solar Energy Converters
A. Solar Radiation - Only 42% of solar radiation that hits the earth’s
atmosphere reaches surface; most is visible light.
B. Photosynthetic Pigments - Pigments found in chlorophyll absorb
various portions of visible light; absorption spectrum.
1. Two major photosynthetic pigments are chlorophyll a and chlorophyll
b.
2. Both chlorophylls absorb violet, blue, and red wavelengths best.
3. Very little green light is absorbed; most is reflected back; this is why
leaves appear green.
4. Carotenoids are yellow-orange pigments which absorb light in violet,
blue, and green regions.
5. In the fall the plant ceases production of chlorophyll, the chlorophyll
then breaks down and the yellow-orange pigments (that were there all
the time in leaves, but the chlorophylls masked them) now show
through.
C. Absorption and action spectrum - A spectrophotometer measures
the amount of light that passes through a sample of pigments.
1) As different wavelengths are passed through, some are absorbed.
2) Graph of percent of light absorbed at each wavelength is absorption
spectrum.
3) Photosynthesis produces oxygen; production of oxygen is used to
measure the rate of photosynthesis.
4) Oxygen production and, therefore, photosynthetic activity is
measured for plants under each specific wavelength; plotted on a graph,
this produces an action spectrum.
5) Since the action spectrum resembles absorption spectrum, this
indicates that chlorophylls contribute to photosynthesis
D. Photosynthetic Reaction
1. In 1930 C. B. van Niel showed that O2 given off by photosynthesis
comes from water and not from CO2.
2. The net equation reads:
.
E. Three Sets of Reactions in Photosynthesis
Light Dependent (Light Reaction) & Light Independent(Dark Reaction)
Stage 1—
1. Light reactions cannot take place unless light is present. They are the
energy-capturing reactions.
b. Chlorophyl within thylakoid membranes absorbs solar energy and
energizes electrons.
Stage 1 part 2— Light energy is converted to chemical energy.
a. The Energized electrons move down the electron transport system;
energy is captured from the breakdown of H2O into Hs and Os and is
used for the production of 2 ATP.
b. Energized electrons are also taken up by NADP+ which bonds to the
lose H+ ions, becoming NADPH.
c. Net Result of Light Reaction is 2 ATP and a molecule of NADPH and
Oxygen gas is released to the atmosphere.
Stage 2—Carbon Fixation or Calvin Cycle Reactions
a. These reactions take place in the stroma; can occur in either the light
or the dark, therefore light independent reaction.
b. These are synthesis reactions that use the energy stored in the
molecules of NADPH and ATP to reduce CO2 then combine it with
RuBP to yield PGA and then the Hs from the NADPH molecule to
assemble a molecule of glucose.
c. The end results of photosynthesis is to manufacture glucose which
can be used by the plant or by other organisms(heterotrophs) and the
release of Oxygen into the atmosphere.
F. Summary of Photosynthesis
Aerobic Cellular Respiration: There are 3 Stages
*the respiratory system is used by the body for gas exchange, then the
circulatory transports oxygen to the cells and removes carbon dioxide in
the process.
1.Glycolysis:
a) 6 carbon glucose is split into two 3 carbon pyruvates(pyruvic acids)
b) anaerobic - proceeds whether or not O2 is present ; O2 is not required
d) net yield of 2 ATP per glucose molecule
e) net yield of 2 NADH per glucose ---> sent to the ETC in mitochondria
The pyruvic acid diffuses into the inner compartment of the
mitochondrion where a transition reaction occurs that serves to
prepare pyruvic acid for entry into the next stage of respiration, this
converts them an acetyl CoA which enters the Kreb's cycle.
If oxygen is not present, the pyruvate(pyruvic acid) is converted to lactic
acid in the cytoplasm of animal cells or to alcohol in yeast cells -anaerobic respiration
2. Citric Acid or Krebs Cycle
a)occurs in the inner mitochondrial matrix
b) an aerobic process; will proceed only in the presence of O2
c) net yield of 2 ATP per glucose molecule
d) net yield of 6 NADH and 2 FADH2 (NAD+ is reduced to NADH, FAD+
is reduced to FADH)
e) in this stage of cellular respiration, the oxidation of glucose to CO2 is
completed
3. Electron Transport System:
a) consists of a series of enzymes on the inner mitochondrial membrane
b) electrons are released from NADH and from FADH2 and as they are
passed along the series of enzymes, they give up energy which is used
to fuel a process called chemiosmosis, which drives the process of
ATP synthesis using an enzyme called ATPase.
c) net yield of 32 ATP per glucose molecule
d) 6 H2O are formed when the electrons unite with O2* at the end of
electron transport chain.
* Note: This is the function of oxygen in living organisms!
Summary of Cellular Respiration
34 ATP
Anaerobic Respiration
-if Oxygen is not available after Glycolysis then the Pyruvic
Acids(Pyruvates) produced at the end of Glycolysis will
undergo Alcoholic Fermentation if in a Yeast Cell or Lactic
Acid Fermentation if in a Muscle Cell and in some bacteria—
resulting in no more ATP being produced so therefore the
net result of fermentation is the 2 ATP produced during
Glycolysis.
Know the function and location of the Stoma, Guard Cells, Cuticle, Xylem, Phloem and
the Mesophyll Layer.