Download Ch. 8 - Photosynthesis

Chapter 8
photosynthesis rap
8-1
Autotrophs – make their
own food
Heterotrophs – consume
their food

Forms of energy:
◦ Light, heat, sound, electrical, chemical…


The form of energy used by living things is
chemical.
The principal chemical compound that stores
and releases energy in cells is ATP
◦ Adenosine triphosphate
ATP
Section 8-1
Adenine
ATP
Ribose
3 Phosphate groups



ATP stores energy in the bonds between the
phosphates.
To store energy, ADP adds on a third
phosphate to become ATP.
To release energy, ATP gives up the third
phosphate to become ADP
ATP charging
Figure 8-3 Comparison of ADP and
ATP to a Battery
Section 8-1
ADP
ATP
Energy
Adenosine diphosphate (ADP) + Phosphate
Partially
charged
battery
Energy
Adenosine triphosphate (ATP)
Fully
charged
battery






Active transport
Charging nerve cells
Movement
Protein synthesis
Cell division
ALL chemical reactions!
 Everything!
8-2
1643


Jan van Helmont
After careful
measurements of a
plant’s water intake
and mass increase,
van Helmont
concluded that trees
gain most of their
mass from water.
1771


Joseph Priestley
Using a bell jar, a
candle and a plant,
Priestley finds that a
plant releases oxygen.


Jan Ingenhousz
Ingenhousz finds that
aquatic plants produce
oxygen bubbles in the
light but not in the
dark. He concludes
that plants need
sunlight to produce
oxygen.


Julius Robert Mayer
Mayer proposes that
plants convert light
energy into chemical
energy.


Melvin Calvin
Calvin traces the
chemical path that
carbon follows to form
glucose. These
reactions are known as
the Calvin Cycle.


Rudolph Marcus
Marcus wins the Nobel
prize in chemistry for
describing the process
by which electrons are
transferred from one
molecule to another in
the electron transport
chain.


Are they made by a single scientist?
Or are they the work of many scientists over
many years?

Photosynthesis uses the energy of sunlight to
convert water and carbon dioxide into highenergy sugars and oxygen.
Carbon dioxide + water + light  glucose + oxygen
6CO2 + 6H2O + light  C6H12O6 + 6O2

Photosynthesis requires the presence of
light- absorbing molecules called pigments.
◦ Chlorophyll is the principal pigment.
◦ This pigment is located in the chloroplasts.
Photosynthesis: Reactants and Products
Light Energy
Chloroplast
CO2 + H2O
Sugars + O2

Chlorophyll a absorbs violet and red light the
best.
◦ It does NOT absorb green or yellow well.

Chlorophyll b absorbs mainly blue and red
wavelengths of light.
◦ It does NOT absorb green or yellow either.

There are two other photosynthetic pigments,
carotene (orange) and xanthophyll (yellow).
◦ They absorb other wavelengths of light and transfer
the energy to chlorophyll.
Photosynthetic Pigments
Absorption of Light by
Chlorophyll a and Chlorophyll b
Chlorophyll b
Chlorophyll a
V
B
G
YO
R
8-3
Photosynthesis overview



Stacks of internal membranes called
thylakoids contain photosystems.
Photosystems carry out the reactions of
photosynthesis involving light (“light
reactions”).
In between the thylakoids the stroma carries
out more reactions that do not require light
(“dark reactions”).
Figure 8-7 Photosynthesis: An Overview
Section 8-3
Light
H20
Chloroplast
CO2
NADP+
ADP + P
LightDependent
Reactions
Calvin
Cycle
ATP
NADPH
O2
Sugars
Chloroplast
Takes place in the thylakoids.
Chlorophyll absorbs light.
Light energy is used to do two things:



1. Split water into hydrogen and oxygen gas.


Oxygen is released to the environment.
Hydrogen is carried to the stroma for the next set of
reactions.
2. Produce high energy carriers ATP and NADPH



Both are used in the dark reactions.
http://vcell.ndsu.nodak.edu/animations/
http://www.youtube.com/watch?feature=playe
r_embedded&v=BK_cjd6Evcw
Figure 8-10 Light-Dependent Reactions
Section 8-3
Photosystem II
Hydrogen
Ion Movement
ATP synthase
Inner
Thylakoid
Space
Thylakoid
Membrane
Stroma
Electron
Transport Chain
Photosystem I
ATP Formation
Chloroplast





Take place in the stroma
Don’t require light
Carbon dioxide is combined with hydrogen to
make glucose.
Energy (ATP) from the light reactions runs the
dark reactions.
Also known as the “Calvin Cycle” and “carbon
fixation”.
Figure 8-11 Calvin Cycle
Section 8-3
CO2 Enters the Cycle
Energy Input
ChloropIast
5-Carbon
Molecules
Regenerated
6-Carbon Sugar
Produced
Sugars and other compounds





Availability of water
Temperature
Light intensity
Availability of minerals
Concentration of carbon dioxide


How does water get to the leaves for
photosynthesis?
“Transpiration pull” brings water up to the
leaves.
◦ Transpiration is the loss of water vapor out the
leaves through openings called stomates.
Section 23-5
A
B
Evaporation of water
molecules out of leaves.
Pull of water molecules
upward from the roots.
Section 23-5
A
B
Evaporation of water
molecules out of leaves.
Pull of water molecules
upward from the roots.

What regulates water loss from the leaves?
◦ Guard cells open and close the stomates to regulate
water loss.
 In dry conditions guard cells close the stomates.
 In wet conditions guard cells open the stomates.
Section 23-4
Cuticle
Veins
Epidermis
Palisade
mesophyll
Xylem
Phloem
Vein
Spongy
mesophyll
Epidermis
Stoma
Guard
cells
Section 23-4
Guard cells
Guard cells
Inner cell
wall
Inner cell
wall
Stoma
Stoma Open
Stoma Closed

What else does a plant need from the soil
besides water?
Section 23-2
Nutrient
Role in Plant
Result of Deficiency
Nitrogen
Proper leaf growth and color; synthesis
of amino acids, proteins, nucleic acids,
and chlorophyll
Stunted plant growth; pale yellow leaves
Phosphorus
Synthesis of DNA; development of roots,
stems, flowers, and seeds
Poor flowering; stunted growth
Potassium
Synthesis of proteins and carbohydrates;
development of roots, stems, and
flowers; resistance to cold and disease
Weak stems and stunted roots; edges of
leaves turn brown
Magnesium
Synthesis of chlorophyll
Thin stems; mottled, pale leaves
Calcium
Cell growth and division; cell wall
structure; cellular transport; enzyme
action
Stunted growth; curled leaves