2. PHOTOSYNTHESIS
-process by which green plants
and certain other organisms use
the energy of light to convert
carbon dioxide and water into the
simple sugar glucose
-provides the basic energy source
for virtually all organisms
-occurs in green plants,
seaweeds, algae, and certain
bacteria
3. PHOTOSYNTHESIS
-Plants use much of this
glucose, a carbohydrate, as an
energy source to build
leaves, flowers, fruits, and
seeds
-They also convert glucose to
cellulose, the structural
material used in their cell walls
-Most plants produce more glucose
than they use, however, and they
store it in the form of starch
and other carbohydrates in
roots, stems, and leaves
4. PHOTOSYNTHESIS
-humans and other animals depend
on glucose as an energy source,
but they are unable to produce it
on their own and must rely
ultimately on the glucose
produced by plants
-the oxygen humans and other
animals breathe is the oxygen
released during photosynthesis
5. PHOTOSYNTHESIS
-The pigment chlorophyll is
responsible for the green color
of plants as well as their
ability to photosynthesize
-In common terrestrial plants
photosynthesis is usually carried
out in the leaves, although it
can also occur in the stem or
other parts of the plant
6.
7. WHERE PHOTOSYNTHESIS
OCCURS?
-Plant photosynthesis occurs in
leaves and green stems within
specialized cell structures
called chloroplasts
-One plant leaf is composed of
tens of thousands of cells, and
each cell contains 40 to 50
chloroplasts
8. WHERE PHOTOSYNTHESIS
OCCURS?
-The chloroplast, an oval-shaped
structure, is divided by
membranes into numerous diskshaped compartments called
thylakoids
-A stack of thylakoids is called
a granum or grana which lie
suspended in a fluid known as
stroma
9. WHERE PHOTOSYNTHESIS
OCCURS?
-Embedded in the membranes of the
thylakoids are hundreds of
molecules of chlorophyll, a
light-trapping pigment required
for photosynthesis
-REMEMBER THE CARBON CYCLE.
10.
11.
12. HOW PHOTOSYNTHESIS
OCCURS?
-It is divided into two stages:
a. LIGHT DEPENDENT REACTION
- the chloroplast traps light
energy and converts it into
chemical energy contained in
nicotinamide adenine
dinucleotide phosphate (NADPH)
and adenosine triphosphate
(ATP), used in the second
stage of photosynthesis
13. HOW PHOTOSYNTHESIS
OCCURS?
- Light energy causes the
electrons in chlorophyll and
other light-trapping pigments
to boost up and out of their
orbit
- Certain red and blue
wavelengths are most
effective. They have the right
amount of energy to energize
chlorophyll electrons and
boost them out of their orbits
to a higher energy level
14. HOW PHOTOSYNTHESIS
OCCURS?
- Other pigments, called
accessory pigments, enhance
the light-absorption capacity
of the leaf by capturing a
broader spectrum of blue and
red wavelengths, along with
yellow and orange wavelengths
- None of the photosynthetic
pigments absorb green light;
as a result, green wavelengths
are reflected, which is why
plants appear green
15. HOW PHOTOSYNTHESIS
OCCURS?
- The electrons are then
passed down a chain of carrier
molecules, called an electron
transport chain
- The electrons are passed
from one carrier molecule to
another in a downhill
direction because electrons
release energy as they move
down the chain
16. HOW PHOTOSYNTHESIS
OCCURS?
- At the end of the electron
transport chain lies the
molecule nicotine adenine
dinucleotide (NADP+)
- Using the energy released by
the flow of electrons, two
electrons from the electron
transport chain combine with a
hydrogen ion and NADP+ to form
NADPH
17. HOW PHOTOSYNTHESIS
OCCURS?
- the electrons are then
transferred and passed through
a different electron transport
chain
- As they pass along the
cascade of electron carrier
molecules, the electrons give
up some of their energy to
fuel the production of
ATP, formed by the addition of
one phosphorus atom to
adenosine diphosphate (ADP)
18. HOW PHOTOSYNTHESIS
OCCURS?
- electrons are replenished by
the water that has been
absorbed by the plant roots
and transported to the
chloroplasts in the leaves
- The movement of electrons
and the action of an enzyme
split the water into oxygen,
hydrogen ions, and electrons
19. HOW PHOTOSYNTHESIS
OCCURS?
- Some of the hydrogen ions
may be used to produce NADPH
at the end of the electron
transport chain, and the
oxygen from the water diffuses
out of the chloroplast and is
released into the atmosphere
through pores in the leaf
20. HOW PHOTOSYNTHESIS
OCCURS?
- The transfer of electrons in
a step-by-step fashion
releases energy and heat
slowly, thus protecting the
chloroplast and cell from a
harmful temperature increase
- It also provides time for
the plant to form NADPH and
ATP
21. HOW PHOTOSYNTHESIS
OCCURS?
b. LIGHT INDEPENDENT REACTION
- The chemical energy required
for the light-independent
reaction is supplied by the
ATP and NADPH molecules
produced in the lightdependent reaction
- is cyclic, that is, it
begins with a molecule that
must be regenerated at the end
of the reaction in order for
the process to continue
22. HOW PHOTOSYNTHESIS
OCCURS?
- Termed the Calvin cycle after
the American chemist Melvin
Calvin who discovered it
- use the electrons and
hydrogen ions associated with
NADPH and the phosphorus
associated with ATP to produce
glucose
23. HOW PHOTOSYNTHESIS
OCCURS?
- These reactions occur in the
stroma, the fluid in the
chloroplast surrounding the
thylakoids, and each step is
controlled by a different
enzyme
- requires the presence of
carbon dioxide molecules, which
enter the plant through pores
in the leaf, diffuse through
the cell to the chloroplast,
and disperse in the stroma
24. HOW PHOTOSYNTHESIS
OCCURS?
- begins in the stroma when
these carbon dioxide molecules
link to sugar molecules called
ribulose bisphosphate (RuBP) in
a process known as carbon
fixation
- With the help of an enzyme,
six molecules of carbon dioxide
bond to six molecules of RuBP
to create six new molecules
25. HOW PHOTOSYNTHESIS
OCCURS?
- Several intermediate
steps, which require
ATP, NADPH, and additional
enzymes, rearrange the position
of the carbon, hydrogen, and
oxygen atoms in these six
molecules
- when the reactions are
complete, one new molecule of
glucose has been constructed
and five molecules of RuBP have
been reconstructed
26. HOW PHOTOSYNTHESIS
OCCURS?
- This process occurs
repeatedly in each chloroplast
as long as carbon dioxide, ATP,
and NADPH are available
- The thousands of glucose
molecules produced in this
reaction are processed by the
plant to produce energy in the
process known as aerobic
respiration, used as structural
materials, or stored
27. PHOTOSYNTHESIS
VARIATIONS
- On hot days, they partially
close the pores in their leaves
to prevent the escape of water.
With the pores only slightly
open, adequate amounts of
carbon dioxide cannot enter the
leaf, and the Calvin cycle
comes to a halt
28. PHOTOSYNTHESIS
VARIATIONS
- To get around this problem,
certain hot-weather plants have
developed a way to keep carbon
dioxide flowing to the stroma
without capturing it directly
from the air
- They open their pores
slightly, take in carbon
dioxide, and transport it deep
within the leaves
29. PHOTOSYNTHESIS
VARIATIONS
- Here they stockpile it in a
chemical form that releases the
carbon dioxide slowly and
steadily into the Calvin cycle
- With this system, these
plants can continue
photosynthesis on hot days,
even with their pores almost
completely closed
30. PHOTOSYNTHESIS
VARIATIONS
- Bacteria lack
chloroplasts, and instead use
structures called
chromatophores or membranes
formed by numerous foldings of
the plasma membrane or
cytoplasm
- The chromatophores house
thylakoids similar to plant
thylakoids, which in some
bacteria contain chlorophyll
31. PHOTOSYNTHESIS
VARIATIONS
- Bacteria lack chloroplasts,
and instead use structures
called chromatophores or
membranes formed by numerous
foldings of the plasma membrane
or cytoplasm
- The chromatophores house
thylakoids similar to plant
thylakoids, which in some
bacteria contain chlorophyll
32. Cactus
Many cacti, such as
the prickly pear
cactus shown here,
carry out
photosynthesis in
enlarged stems
rather than leaves.
The stems also
serve to store water,
essential for
photosynthesis.
33. CELLULAR RESPIRATION
- process in which cells produce
the energy they need to survive
- cells use oxygen to break down
the sugar glucose and store its
energy in molecules of
adenosine triphosphate (ATP)
- critical for the survival of
most organisms because the
energy in glucose cannot be
used by cells until it is
stored in ATP
34. CELLULAR RESPIRATION
- occurs within a cell
constantly, day and night, and
if it ceases, the cell—and
ultimately the organism—dies
- Two critical ingredients
required for cellular
respiration are glucose and
oxygen
- cells must have a steady supply
of glucose so that ATP
production is continuous
35.
36. CELLULAR RESPIRATION
- Cellular respiration sometimes
is referred to as aerobic
respiration, meaning that it
occurs in the presence of
oxygen
- transfers about 40 percent of
the energy of glucose to ATP
- The rest of the energy is
released as heat, which warmblooded organisms use to
maintain body temperature, and
cold-blooded organisms release
to the atmosphere
37. CELLULAR RESPIRATION
- The process of cellular
respiration occurs in four
stages: glycolysis; the
transition stage; the Krebs
cycle, also known as the citric
acid cycle; and the electron
transport chain. Each stage
accomplishes different tasks
38. GLYCOLYSIS
- the first stage of cellular
respiration wherein glucose is
the primary fuel
- glucose is broken down with the
help of enzymes and other
molecules found in the
cytoplasm
- Enzymes first attach two
phosphate groups to glucose to
make it more reactive (A
phosphate group is a cluster of
one phosphorus and four oxygen
atoms)
39. GLYCOLYSIS
- The addition of the two
phosphate groups prepares
glucose for the action of
another enzyme
- This enzyme splits glucose in
half to produce two threecarbon molecules, each with one
phosphate group attached
- In the next step, an enzyme
removes one hydrogen atom and
two electrons from each threecarbon molecule
40. GLYCOLYSIS
- Both hydrogen atoms are
modified to hydrogen ions,
positively charged particles
- A hydrogen ion and two
electrons from each threecarbon molecule are transferred
as a unit to a large molecule
called nicotinamide adenine
dinucleotide (NAD+) to form two
molecules of NADH
41. GLYCOLYSIS
- The hydrogen ions and electrons
stored in each molecule of NADH
are used to make ATP in later
stages of cellular respiration
- In the final steps of
glycolysis, two hydrogen atoms
are removed from each threecarbon compound
- These hydrogen atoms bond to
free-floating oxygen atoms in
the cytoplasm to form water
42. GLYCOLYSIS
- This step prepares the two
three-carbon compounds for
action by the next enzyme in
the pathway
- This enzyme removes the
phosphate group from each
three-carbon compound
- Each phosphate group then bonds
to a single molecule of
adenosine diphosphate (ADP)
43. GLYCOLYSIS
- ADP is composed of three
carbon-based rings and a tail
of two phosphate groups. The
addition of the third phosphate
group to the tail forms ATP
- In this step, two new ATP
molecules are produced
- When cells require
energy, another enzyme breaks
off the third phosphate
group, releasing energy that
powers the cell
44. GLYCOLYSIS
- The removal of the third
phosphate from ATP converts ATP
back to ADP, which is used
again in cellular respiration
to make more ATP
- When the two three-carbon
compounds are separated from
the phosphate groups, the
three-carbon compounds are
converted to two molecules of
pyruvate, each composed of
three carbon, three oxygen, and
three hydrogen atoms
45. TRANSITION STAGE
- The transition stage is a short
biochemical pathway that links
glycolysis with the Krebs cycle
- The pyruvate molecules move
from the cytoplasm to the
mitochondria, where the
remaining steps of cellular
respiration are carried out
- Each mitochondrion contains a
membrane that is folded back
and forth many times
46. TRANSITION STAGE
- This extensive membrane is
studded with hundreds of
thousands of enzymes that
direct cellular respiration
- The numerous enzymes enable
great quantities of ATP to be
produced simultaneously in one
mitochondrion
- Without mitochondria or a
similar structure, most cells
could not generate enough ATP
to survive
47. TRANSITION STAGE
- In this brief stage, enzymes
transfer hydrogens and
electrons from the two pyruvate
molecules to two molecules of
NAD+ to form two more molecules
of NADH
- Another enzyme breaks off one
carbon and two oxygen atoms
from each pyruvate molecule
48. TRANSITION STAGE
- These atoms combine to form
carbon dioxide, the primary
waste product of cellular
respiration, which diffuses out
of the cell
- As a result of these reactions,
each pyruvate molecule is
transformed into a two-carbon
compound called an acetyl group
49. TRANSITION STAGE
- The two acetyl groups unite
with two molecules of coenzyme
A to form two acetyl coenzyme A
molecules
- The acetyl coenzyme A molecules
are the molecules that enter
the Krebs cycle
52. KREB’S CYCLE
- During the Krebs cycle, the
acetyl coenzyme A molecules are
processed
- As this complex pathway
progresses, six molecules of
NADH are formed
- Additional carbon dioxide is
created, and this process
releases energy that is used to
build two molecules of ATP from
a pool of ADP and phosphate
groups in the mitochondria
53. KREB’S CYCLE
- Hydrogens and electrons then
are transferred to a molecule
of flavin adenine dinucleotide
(FAD++)to form FADH2, a
molecule like NADH that
temporarily stores hydrogen and
electrons for later use
54. KREB’S CYCLE
- By the end of the Krebs cycle,
most of the usable energy from
the original glucose molecule
has been transferred to ten
molecules of NADH (two from
glycolysis, two from the
transition stage, and six from
the Krebs cycle); two molecules
of FADH2; and four molecules of
ATP, two of which were formed
in glycolysis
55.
56. ELECTRON TRANSPORT CHAIN
- The reactions of the electron
transport chain occur in
several closely spaced
molecules embedded in the
mitochondrial membrane
- the NADH and FADH2 molecules
dump off their load of
electrons and hydrogen ions
near these electron transport
chain molecules
57. ELECTRON TRANSPORT CHAIN
- The first molecule in the chain
has an attraction for electrons
and grabs them, but the
molecule next to it in the
chain has an even stronger
attraction and grabs the
electrons away from the first
molecule
- The electrons are passed down
the chain in this manner, until
they reach oxygen, the final
molecule in the chain
58. ELECTRON TRANSPORT CHAIN
- Oxygen has a stronger appetite
for electrons than any molecule
in the chain, and the electrons
therefore are held by oxygen
- They are joined by the hydrogen
ions that were dropped off by
NADH and FADH2 at the beginning
of the electron transport chain
- The combination of the
electrons, hydrogen ions, and
oxygen forms water, used by the
cell in other biochemical
59. ELECTRON TRANSPORT CHAIN
- As NADH and FADH2 release
hydrogen and electrons in the
electron transport chain, they
are converted back to NAD+ and
FAD++, respectively, providing
the cell with a steady supply
of these molecules so that
cellular respiration can be
carried out over and over again
60. ELECTRON TRANSPORT CHAIN
- As the electrons flow down the
electron transport chain, they
release a veritable windfall of
energy that is used by an
enzyme to make more ATP
- In most cells, the electron
transport chain produces 32
molecules of ATP
61. ELECTRON TRANSPORT CHAIN
- Together with the two ATP
molecules gained in glycolysis
and the four generated in the
Krebs cycle, cellular
respiration produces a grand
total of 38 molecules of ATP
for every molecule of glucose
processed
62. ELECTRON TRANSPORT CHAIN
- Glucose molecules enter the
cell by the hundreds of
thousands and are processed
simultaneously to generate
millions of ATP molecules every
second
- Some of the ATP molecules
remain in the mitochondria to
supply it with energy, but most
stream from the mitochondria to
the cytoplasm, where they fuel
the cell’s activities
63. ELECTRON TRANSPORT CHAIN
- It is estimated that a single
human brain cell uses a
staggering 10 million ATP
molecules per second to carry
out its tasks
- Although glucose is the primary
fuel for cellular respiration,
cells can rely on other
molecules to produce ATP
64. ELECTRON TRANSPORT CHAIN
- The cellular respiration
pathway is connected to other
metabolic pathways that can
donate molecules to cellular
respiration at different steps
along the way
- For example, glycerol, a
breakdown product of fat, can
enter the cellular respiration
pathway in the middle of
glycolysis
65. ELECTRON TRANSPORT CHAIN
- Another product of fat
digestion, fatty acids, can
enter at the transition stage
- Glycerol is modified in
glycolysis to pyruvate, and
fatty acids are modified to
acetyl coenzyme A in the
transition stage. The pyruvate
and acetyl coenzyme A are
processed through the remaining
steps of cellular respiration
to yield ATP
66. ELECTRON TRANSPORT CHAIN
- The cellular respiration
pathway is connected to other
metabolic pathways that can
donate molecules to cellular
respiration at different steps
along the way
- For example, glycerol, a
breakdown product of fat, can
enter the cellular respiration
pathway in the middle of
glycolysis
80. question:
14. What is the process
by which green plants
and certain other
organisms use the
energy of light to
convert carbon dioxide
and water into the
simple sugar glucose?
81. question:
15. What do bacteria
use for photosynthesis
since they do not have
chloroplasts?
