3. • Photosynthesis is the process by which autotrophic organisms use light
energy to make sugar and oxygen gas from carbon dioxide and water
3
AN OVERVIEW OF PHOTOSYNTHESIS
Carbon
dioxide
Water Glucose Oxygen
gas
PHOTOSYNTHESIS
5. 5
◼ Almost all plants are photosynthetic autotrophs, like some
bacteria and protists
❑ Autotrophs generate their own organic matter through
photosynthesis
❑ Sunlight energy is transformed to energy stored in the form of
chemical bonds
(a) Mosses, ferns, and
flowering plants
(b) Kelp
(c) Euglena (d) Cyanobacteria
THE BASICS OF PHOTOSYNTHESIS
6. 6
Different wavelengths of visible light are seen by the
human eye as different colors.
WHY ARE PLANTS GREEN?
Gamma
rays
X-rays UV Infrared
Micro-
waves
Radio
waves
Visible light
Wavelength (nm)
8. 8
WHY ARE PLANTS GREEN?
Plant Cells have
Green Chloroplasts
The thylakoid
membrane of the
chloroplast is
impregnated with
photosynthetic
pigments (i.e.,
chlorophylls,
carotenoids).
9. • Chloroplasts absorb
light energy and convert
it to chemical energy
9
Light
Reflected
light
Absorbed
light
Transmitted
light
Chloroplast
THE COLOR OF LIGHT SEEN IS THE COLOR NOT ABSORBED
10. The location and structure of chloroplasts
10
LEAF CROSS SECTION MESOPHYLL CELL
LEAF
Chloroplast
Mesophyll
CHLOROPLAST Intermembrane space
Outer
membrane
Inner
membrane
Thylakoid
compartment
Thylakoid
Stroma
Granum
Stroma
Grana
11. Photosynthesis occurs in chloroplasts:
• In most plants, photosynthesis occurs primarily in the leaves, in the
chloroplasts
• A chloroplast contains:
• stroma, a fluid
• grana, stacks of thylakoids
• The thylakoids contain chlorophyll
• Chlorophyll is the green pigment that captures light for photosynthesis
11
13. Light-dependent Reaction (Light
Reaction)
➢Process which occurs in the
presence of light
➢Occurs in the Grana
13
STAGES OF PHOTOSYNTHESIS
Light-independent Reaction
(Dark Reaction)
➢ Process which does not
require light
➢ Occurs in the Stroma
Calvin
cycle
Light
reactions
ADP
+ P
Chloroplast
Light
14. Light-dependent Reaction (Light Reaction)
14
STAGES OF PHOTOSYNTHESIS
❖ Noncyclic Photophosphorylation
Production of ATP in Z-pathway, pathway followed by excited
electrons from photosystem II.
❖ Cyclic Photophosphorylation
Production of ATP in a cyclic manner
Photosystem I
15. Noncyclic Photophosphorylation
❖Photosystem II regains electrons by splitting water, leaving
O2 gas as a by-product
15
Primary
electron acceptor
Primary
electron acceptor
Photons
PHOTOSYSTEM I
PHOTOSYSTEM II
Energy for
synthesis of
by chemiosmosis
17. How the Light Reactions Generate ATP and NADPH
17
2 H+ + 1/2
Water-splitting
photosystem
Reaction-
center
chlorophyll
Light
Primary
electron
acceptor
Energy
to make
Primary
electron
acceptor
Primary
electron
acceptor
NADPH-producing
photosystem
Light
NADP+
1
2
3
19. Review: Photosynthesis uses light energy
to make food molecules
• A summary of the
chemical processes of
photosynthesis
19
Light
Chloroplast
Photosystem II
Electron
transport chains
Photosystem I
CALVIN
CYCLE Stroma
LIGHT REACTIONS CALVIN CYCLE
Cellular
respiration
Cellulose
Starch
Other organic
compounds
35. Metabolic reactions fall into one of
two subtype:
Catabolism is all metabolic reactions
in which large biochemical molecules
are broken down to smaller ones.
Catabolic reactions usually release
energy. The reactions involved in the
oxidation of glucose are catabolic.
36. Metabolic reactions fall into one of
two subtype:
Anabolism is all metabolic reactions in
which small biochemical molecules
are joined together to form larger
ones.
37.
38. A metabolic pathway is a series of
consecutive biochemical reactions used
to convert a starting material into an
end product. Such pathways may be
linear, in which a series of reactions
generates a final product, or cyclic, in
which a series of reactions regenerates
the first reactant.
39.
40. Classify each of the following chemical
processes as anabolic or catabolic.
a. Synthesis of a polysaccharide from
monosaccharides
b. Hydrolysis of a pentasaccharide to
monosaccharides
c. Formation of a nucleotide from
phosphate, nitrogenous base, and
pentose sugar
d. Hydrolysis of a triacylglycerol to
glycerol and fatty acids
41. METABOLISM AND CELL STRUCTURE
Prokaryotic cells have no nucleus
and are found only in bacteria. The
DNA that governs the reproduction
of prokaryotic cells is usually a
single circular molecule found near
the center of the cell in a region
called the nucleoid.
42. METABOLISM AND CELL STRUCTURE
A eukaryotic cell is a cell in which
the DNA is found in a membrane
enclosed nucleus. Cells of this
type, which are found in all higher
organisms, are about 1000 times
larger than bacterial cells.
43. METABOLISM AND CELL STRUCTURE
The cytoplasm is the water-based
material of a eukaryotic cell that lies
between the nucleus and the outer
membrane of the cell. Within the
cytoplasm are several kinds of small
structures called organelles
44. METABOLISM AND CELL STRUCTURE
An organelle is a minute structure
within the cytoplasm of a cell that
carries out a specific cellular function.
The organelles are surrounded by the
cytosol. The cytosol is the water-
based fluid part of the cytoplasm of a
cell.
45. METABOLISM AND CELL STRUCTURE
A lysosome is an organelle that contains
hydrolytic enzymes needed for cellular
rebuilding, repair, and degradation. Some
lysosome enzymes hydrolyze proteins to amino
acids; others hydrolyze polysaccharides to
monosaccharides. Bacteria and viruses
“trapped” by the body’s immune system are
degraded and destroyed by enzymes from
lysosomes.
46. METABOLISM AND CELL STRUCTURE
A mitochondrion is an organelle that is
responsible for the generation of most of the
energy for a cell. Mitochondria are sausage-
shaped organelles containing both an outer
membrane and a multifolded inner membrane.
The outer membrane, which is about 50% lipid
and 50% protein, is freely permeable to small
molecules. The inner membrane, which is about
20% lipid and 80% protein, is highly impermeable
to most substances.
47. METABOLISM AND CELL STRUCTURE
The nonpermeable nature of the inner
membrane divides a mitochondrion into
two separate compartments—an interior
region called the matrix and the region
between the inner and outer membranes,
called the intermembrane space. The folds
of the inner membrane that protrude into
the matrix are called cristae.
50. METABOLISM AND CELL STRUCTURE
Identify each of the following structural features
of a mitochondrion.
a. The more permeable of the two mitochondrial
membranes
b. The mitochondrial membrane that has cristae
c. The mitochondrial membrane that determines
the size of the matrix
d. The mitochondrial membrane that is interior
to the intermembrane space
52. IMPORTANT INTERMEDIATE COMPOUNDS
IN METABOLIC PATHWAYS
A phosphoryl group is the functional group
derived from a phosphate ion that is part of
another molecule. A phosphoanhydride
bond is the chemical bond formed when two
phosphate groups react with each other and
a water molecule is produced.
55. Flavin Adenine Dinucleotide (FAD,
FADH2)
Flavin adenine dinucleotide (FAD) is a coenzyme
required in numerous metabolic redox reactions.
Structurally, FAD can be visualized as containing
either three subunits or six subunits.
56. Flavin Adenine Dinucleotide (FAD,
FADH2)
Flavin and ribitol, the two components
attached to the ADP unit, together
constitute the B vitamin riboflavin.
57. Flavin Adenine Dinucleotide (FAD,
FADH2)
This block diagram shows the basis for the name flavin
adenine dinucleotide. Ribitol is a reduced form of ribose;
a -CH2OH group is present in place of the -CHO group.
62. Flavin Adenine Dinucleotide (FAD,
FADH2)
For an enzyme-catalyzed redox reaction
involving removal of two hydrogen atoms, such
as this, each removed hydrogen atom is
equivalent to a hydrogen ion, H, plus an
electron, e.
63. Flavin Adenine Dinucleotide (FAD,
FADH2)
On the basis of this equivalency, the summary
equation relating the oxidized and reduced
forms of flavin adenine dinucleotide is usually
written as
64. Nicotinamide Adenine Dinucleotide
(NAD, NADH)
Several parallels exist between the characteristics
of nicotinamide adenine dinucleotide (NAD) and
those of FAD. Both have coenzyme functions in
metabolic redox pathways, both have a B vitamin
as a structural component, and both can be
represented structurally by using a three-subunit
or a six-subunit formulation.
67. Nicotinamide Adenine Dinucleotide
(NAD, NADH)
The active portion of NAD in metabolic
redox reactions is the nicotinamide
subunit of the molecule. The nicotinamide
is reduced, converting the NAD to NADH,
a molecule with one additional hydrogen
atom and two additional electrons. Thus
NAD is the oxidized form of the molecule,
and NADH is the reduced form.
69. Nicotinamide Adenine Dinucleotide
(NAD, NADH)
A typical cellular reaction in which NAD serves as
the oxidizing agent is the oxidation of a
secondary alcohol to give a ketone.
71. Coenzyme A (CoA–SH)
Another important coenzyme in metabolic
pathways is coenzyme A, a derivative of the B
vitamin pantothenic acid. The three-subunit and
six-subunit block diagrams for coenzyme A are
73. Coenzyme A (CoA–SH)
Coenzyme A as refl ecting a general metabolic
function of this substance; it is the transfer of
acetyl groups in metabolic pathways. An acetyl
group is the portion of an acetic acid molecule
(CH3–COOH) that remains after the —OH group
is removed from the carboxyl carbon atom. An
acetyl group bonds to CoA–SH through a
thioester bond to give acetyl CoA.
74. Classification of Metabolic Intermediate
Compounds
The metabolic intermediate compounds
considered in this section can be classified into
three groups based on function. The
classifications are:
1. Intermediates for the storage of energy and
transfer of phosphate groups
2. Intermediates for the transfer of electrons in
metabolic redox reactions
3. Intermediates for the transfer of acetyl
groups
75.
76. Give the abbreviated formula for the
following metabolic intermediate
compounds.
a. The intermediate produced when FAD is
reduced
b. The intermediate produced when FADH2
is oxidized
c. The intermediate produced when ATP
loses two phosphoryl groups as a PPi
d. The intermediate produced when acetyl–
S–CoA transfers an acetyl group
77. HIGH-ENERGY PHOSPHATE COMPOUNDS
A high-energy compound is a compound that has
a greater free energy of hydrolysis than that of a
typical compound. High energy compounds differ
from other compounds in that they contain one
or more very reactive bonds, often called
strained bonds. The energy required to break
these strained bonds during hydrolysis is less
than that generally required to break a chemical
bond.
81. AN OVERVIEW OF BIOCHEMICAL ENERGY
PRODUCTION
Stage 1: The first stage, digestion, begins in the
mouth (saliva contains starch-digesting enzymes),
continues in the stomach (gastric juices), and is
completed in the small intestine (the majority of
digestive enzymes and bile salts). The end
products of digestion—glucose and other
monosaccharides from carbohydrates, amino
acids from proteins, and fatty acids and glycerol
from fats and oils—are small enough to pass
across intestinal membranes and into the blood,
where they are transported to the body’s cells.
82. AN OVERVIEW OF BIOCHEMICAL
ENERGY PRODUCTION
Stage 2: The second stage, acetyl group
formation, involves numerous reactions,
some of which occur in the cytosol of cells
and some in cellular mitochondria. The small
molecules from digestion are further
oxidized during this stage. Primary products
include two-carbon acetyl units (which
become attached to coenzyme A to give
acetyl CoA) and the reduced coenzyme
NADH.
83. AN OVERVIEW OF BIOCHEMICAL ENERGY
PRODUCTION
Stage 3: The third stage, the citric acid cycle,
occurs inside mitochondria. Here acetyl
groups are oxidized to produce CO2 and
energy. Some of the energy released by
these reactions is lost as heat, and some is
carried by the reduced coenzymes NADH
and FADH2 to the fourth stage. The CO2
that we exhale as part of the breathing
process comes primarily from this stage.
84. AN OVERVIEW OF BIOCHEMICAL ENERGY
PRODUCTION
Stage 4: The fourth stage, the electron
transport chain and oxidative
phosphorylation, also occurs inside
mitochondria. NADH and FADH2 supply the
“fuel” (hydrogen ions and electrons) needed
for the production of ATP molecules, the
primary energy carriers in metabolic
pathways. Molecular O2, inhaled via
breathing, is converted to H2O in this stage.
85. AN OVERVIEW OF BIOCHEMICAL ENERGY
PRODUCTION
The common metabolic pathway is
the sum total of the biochemical
reactions of the citric acid cycle, the
electron transport chain, and
oxidative phosphorylation.
86. THE CITRIC ACID CYCLE
The citric acid cycle is the series of
biochemical reactions in which the acetyl
portion of acetyl CoA is oxidized to carbon
dioxide and the reduced coenzymes FADH2
and NADH are produced. It is also known as
the Krebs cycle, after its discoverer Hans
Adolf Krebs, and as the tricarboxylic acid
cycle, in reference to the three carboxylate
groups present in citric acid.
100. Regulation of the Citric Acid Cycle
The rate at which the citric acid cycle
operates is controlled by the body’s
need for energy (ATP). When the body’s
ATP supply is high, the ATP present
inhibits the activity of citrate synthase,
the enzyme in Step 1 of the cycle.
101. Regulation of the Citric Acid Cycle
When energy is being used at a high rate, a
state of low ATP and high ADP
concentrations, the ADP activates citrate
synthase and the cycle speeds up. A similar
control mechanism exists at Step 3, which
involves isocitrate dehydrogenase; here
NADH acts as an inhibitor and ADP as an
activator.
102.
103. THE ELECTRON TRANSPORT CHAIN
The NADH and FADH2 produced in the
citric acid cycle pass to the electron
transport chain. The electron transport
chain is a series of biochemical reactions
in which electrons and hydrogen ions
from NADH and FADH2 are passed to
intermediate carriers and then
ultimately react with molecular oxygen
to produce water.
105. THE ELECTRON TRANSPORT CHAIN
The electrons that pass through the various steps of
the electron transport chain (ETC) lose some energy
with each transfer along the chain. Some of this
“lost” energy is used to make ATP from ADP
(oxidative phosphorylation),
106. THE ELECTRON TRANSPORT CHAIN
The enzymes and electron carriers
needed for the ETC are located along
the inner mitochondrial membrane.
Within this membrane are four
distinct protein complexes, each
containing some of the molecules
needed for the ETC process to occur.
107. THE ELECTRON TRANSPORT CHAIN
These four protein complexes, which are tightly
bound to the membrane, are
Complex I: NADH–coenzyme Q reductase
Complex II: Succinate–coenzyme Q reductase
Complex III: Coenzyme Q–cytochrome c reductase
Complex IV: Cytochrome c oxidase
120. Oxidative phosphorylation is the
biochemical process by which ATP is
synthesized from ADP as a result of the
transfer of electrons and hydrogen ions
from NADH or FADH2 to O2 through the
electron carriers involved in the electron
transport chain.
OXIDATIVE PHOSPHORYLATION
121. OXIDATIVE PHOSPHORYLATION
Coupled reactions are pairs of
biochemical reactions that occur
concurrently in which energy released
by one reaction is used in the other
reaction. Oxidative phosphorylation
and the oxidation reactions of the
electron transport chain are coupled
systems.
123. OXIDATIVE PHOSPHORYLATION
Chemiosmotic coupling is an
explanation for the coupling of ATP
synthesis with electron transport
chain reactions that requires a
proton gradient across the inner
mitochondrial membrane.
126. ATP PRODUCTION FOR THE COMMON
METABOLIC PATHWAY
For each mole of NADH oxidized in the ETC,
2.5 moles of ATP are formed. FADH2, which
does not enter the ETC at its start, produces
only 1.5 moles of ATP per mole of FADH2
oxidized. FADH2’s entrance point into the
chain, complex II, is beyond the first “proton-
pumping” site, complex I. Hence fewer ATP
molecules are produced from FADH2 than
from NADH.
127. ATP PRODUCTION FOR THE COMMON
METABOLIC PATHWAY
The energy yield, in terms of ATP production,
can now be totaled for the common
metabolic pathway. Every acetyl CoA
entering the citric acid cycle (CAC) produces
three NADH, one FADH2, and one GTP (which
is equivalent in energy ATP. Thus 10
molecules of ATP are produced for each
acetyl CoA catabolized.
129. THE IMPORTANCE OF ATP
The energy derived from ATP hydrolysis is a
biochemically useful amount of energy. It is
larger than the amount of energy needed by
compounds to which ATP donates energy, and
yet it is smaller than that available in
compounds used to form ATP.
130. NON-ETC OXYGEN-CONSUMING
REACTIONS
The electron transport chain/oxidative
phosphorylation phase of metabolism consumes
more than 90% of the oxygen taken into the human
body via respiration. As a normal part of metabolic
chemistry, significant amounts of this remaining O2
are converted into several highly reactive oxygen
species (ROS). Among these ROSs are hydrogen
peroxide (H2O2), superoxide ion (O2), and hydroxyl
radical (OH). The latter two of these substances are
free radicals, substances that contain an unpaired
electron.
131. NON-ETC OXYGEN-CONSUMING
REACTIONS
Reactive oxygen species have beneficial functions
within the body, but they can also cause problems
if they are not eliminated when they are no longer
needed. White blood cells have a significant
concentration of superoxide free radicals. Here,
these free radicals aid in the destruction of
invading bacteria and viruses. Their formation
reaction is
133. B VITAMINS AND THE COMMON
METABOLIC PATHWAY
1.Niacin-as NAD+ and NADH
2.Riboflavin-as FAD, FADH2 and FMN
3.Thiamin-as TPP
4.Panthothenic acid-as CoA
