Chapter 8
Photosynthesis
&
Chapter 9
Respiration
Section 8-1
Energy and Life
I. Energy – the ability to do work
A. Many types of energy, mechanical, electrical,
chemical, light, and heat, etc.
B. Most organisms ultimately use the sun’s energy
II. Autotrophs v Heterotrophs
A. Autotrophs are organisms that
make their own food, usually powered
by the sun’s energy
B.Heterotrophs feed on other organisms
for their direct source of energy, but
they ultimately depend on the sun’s
energy too.
How is this?
III. ATP (Adenosine Triphosphate)
A. ATP is considered the
energy currency of the cell.
ADP = Adenosine Diphosphate
ATP
B. ATP provides the
energy that powers
cellular processes.
Such as?
ADP + Phosphate
-------
Energy stored
Energy Released
Section 9-1
Chemical Pathways
I. Overview of Cellular Respiration
A. The first step in respiration is always glycolysis.
B. If Oxygen is present glycolysis proceeds
to the Krebs cycle and the electron transport
chain.
1. This is known as aerobic respiration and can be written as:
6O2 + C6H12O6 ---- 6CO2 + 6H2O + Energy
Oxygen + glucose ---- carbon dioxide + water + Energy
C. If oxygen is not present then fermentation may occur.
II. Glycolysis
A. In glycolysis 1 6-carbon glucose is
broken down into 2 3-carbon pyruvic acid
molecules.
B. A Net gain of 2 ATPs and 2 NADH
1. NADH is an electron carrier that carries 2 electrons
(each) to the Electron Transport Chain
2 ATP
Glucose
2 ADP
4 ADP
4 ATP
2 G3P
2 Pyruvic Acid
2 NAD+
2 NADH
III. Fermentation
A. Keeps Glycolysis going under anaerobic
(oxygen-less) conditions by producing NAD+
B. Two Major Types
1. Alcoholic Fermentation
Pyruvic acid + NADH  alcohol + CO2 + NAD+
2. Lactic Acid Fermentation
Pyruvic acid + NADH  lactic acid + NAD+
Formation of acetyl coenzyme A includes formation of citric acid.
The Citric Acid cycle is also known as the Krebs cycle.
Section 9-2
The Krebs Cycle
&
Electron Transport
I.
The Krebs Cycle (an overview)
A. Pyruvic acid (from glycolysis) is broken
down into carbon dioxide in a series of
energy-extracting reactions
B. Takes place in the mitochondria
C. The Process
1. Acetyl-CoA is formed as
a CO2 and an NADH are produced
2. Two carbons of acetyl-CoA are added to a 4-carbon
compound forming a 6-carbon Citric Acid
3. A 5-carbon Compound is created as another CO2 and
NADH are given off.
4. The 4-carbon compound mentioned in step 2 is
recreated, as a CO2, an NADH, and an ATP are produced.
5. Lastly before another Acetyl CoA enters the cycle an FADH2
and an NADH are released.
Totals:
Per Pyruvic Acid
3 CO2 (exhaled)
1 ATP (used by cells)
1 FADH2 (to electron
4 NADH
transport)
In glycolysis two pyruvic
acids are produced, so to
get the number of these
products per glucose we
must multiply by two.
II. The Electron Transport Chain (ETC)
A. The electron carriers (FADH2 and NADH)
generated in the Krebs cycle pass their electrons
through the ETC
B. This generates ATP from ADP
C. Occurs in the mitochondria
D. As electrons are passed through the proteins
of the ETC, hydrogen ions (H+) are pumped from
the matrix to the intermembrane space.
1. H+ builds up in the intermembrane space,
creating a reservoir of H+
2. This reservoir “turns a turbine” called ATP
synthase which makes ADP into ATP
E. After the electrons have passed through
the ETC they are passed on to OXYGEN and
paired with H+ to form H2O.
III. Grand Totals of ATP produced aerobically
Vocabulary Review:
Aerobically- in the presence of oxygen
Per Glucose
Glycolysis
Citric Acid Production
2 NADH
2 ATP
4 ATP
2 NADH x3 ATP each
6 ATP
6 NADH x3 ATP each
2 FADH2 x2 ATP each
2 ATP
18 ATP
4 ATP
36 ATP
Krebs Cycle
Section 8-2
Photosynthesis: An Overview
I. The Photosynthesis Equation
A. Photosynthesis uses the energy of sunlight
to convert water and carbon dioxide into high
energy sugars and oxygen
B.
6CO2 + 6H2O + light energy  C6H12O6 + O2
Carbon dioxide + water + light energy  sugars
+ oxygen
C. Equation is reverse of that for respiration.
II. Light and Pigments
A. Photosynthesis requires, in addition to carbon
dioxide and water, light and chlorophyll
B. Chlorophyll absorbs violet and blue and
red light strongly, reflects green light and
thus leaves appear green.
C.When light hits chlorophyll high energy
electrons are created.
These high energy electrons power
photosynthesis.
Section 8-3 Part One
The Reactions of Photosynthesis
I. Inside a Chloroplast
A. Thylakoids – saclike photosynthetic
membranes in the chloroplast
B. Grana – a stack of thylakoids
C. Photosystems1. organized proteins, chlorophyll and other pigments
2. located in the thylakoid membrane
3. light collecting units of the chloroplast
D. Stroma – region outside the thykaloid
membrane
II. Light Dependent Reactions
A.The light dependent reactions produce oxygen
gas and convert ADP and NADP+ into energy
carriers ATP (chemical) and NADPH (electron)
B. The Process (pp. 210 -211) (A =1, B=2 . . . )
1. Light hits photosystem II electrons become
higher in energy as H2O is broken down into H+
and O2, the electrons enter the photosynthetic ETC
2. Electrons move from photosystem II to photosystem I,
causing H+ to be pumped from the stroma to the inner
Thylakoid space.
3. In photosystem I electrons are reenergized by light.
NADP+ picks up electrons and H+ generating NADPH.
4. During steps 2 and 3 H+ builds up in inner
thylakoid space making it positively charged and the
stroma negatively charged. Creates a reservoir of H+.
5. H+ passes to stroma through ATP synthase generating
ATP from ADP
Section 8-3 Part 2
The Reactions of Photosynthesis
III. Calvin Cycle
A. ATP and NADPH are only stable for a few
minutes
B. The Calvin cycle uses ATP and NADPH from the
light dependent reactions to produce high-energy
sugars which are stable
C. The Process
1. Six CO2 combine with six 5-carbon molecules,
ultimately resulting in 12 3-carbon molecules
2. The twelve 3-carbon molecules are “energized”
by ATP and NADPH
3. Two of the 3-carbon molecules are removed
from the cycle for use by the plant
4. The remaining ten 3-carbon molecules are
converted back to six 5-carbon molecules to repeat
the cycle
D. 6 CO2 molecules enter the Calvin cycle and a
single 6-carbon sugar is produced
IV. Factors that Affect Photosynthesis
A. Availability of water
B. Temperature
C. Light intensity