Transcript Photosynthesis

Photosynthesis
Section 1: Energy and Life
Botany is the study
of plants.
What characteristics
would define a
plant?
8.1 Energy and Life
Energy – the ability to do work
All living things need chemical
energy to survive.
The most important molecule cells
use to store and release energy is ATP
(adenosine triphosphate)
Chemical Energy and ATP
• When an organism uses the energy
from ATP, the ATP is converted into
ADP
– ADP (Adenosine Diphosphate ) has
only 2 phosphate groups.
– Cells can add a phosphate to ADP to
make ATP to store energy.
(This requires energy)
– How is ATP and ADP similar to
rechargeable batteries?
– Where do YOUR cells get the energy
to convert ADP into ATP?
Chemical Energy and ATP
How could a small seed gain
enough energy to grow into
seed a giant tree?
Autotroph – uses energy
from the sun to produce food
Heterotroph – obtains energy
from food it consumes
Chemical Energy and ATP
Chemical Energy and ATP
Overall Photosynthesis Equation
6CO2 + 6H2O
Carbon
Dioxide
Water
LIGHT
C6H12O6 + 6O2
Glucose
Oxygen
Photosynthesis: the process where plants convert energy
from the sun into chemical energy stored in the bonds of
carbohydrates.
Light and Pigments
Light Speed, c = 2.9979 x 108 m/s
Or 670.6 million mph
How are the two types of
light different? How are
they similar?
Light and Pigments
Electromagnetic Spectrum
Wave length and energy are
inversely proportional
The smaller the wave length,
the more energy
Which type of light has more
energy, the blue or the red?
Explain.
Light and Pigments
• What colors of light
are being absorbed?
• What colors of light
are being reflected?
• What color would
the object appear if
there was no blue
light?
• Why are plants
usually green?
Spectroscope
Lab
Light and Pigments
• Pigments – light absorbing
molecules
• Chlorophyll – the most
abundant pigment in
plants, that absorbs blue
and red light.
– Chlorophyll a - a blue-green
pigment
– Chlorophyll b - a yellowgreen pigment
Light and Pigments
• Accessory Pigments: pigments
other than chlorophyll.
– Carotene: orange
– Xanthophyll: yellow
– Anthocyanin: red
• Why do plants need accessory
pigments?
– They absorb light in other
regions of the spectrum
• The accessory pigments are
always present in most plants
but masked by the chlorophyll.
Light and Pigments
Why do leaves change
color in the fall?
Answer: Shorter day
lengths stop chlorophyll
production, and expose
accessory pigments
Photosynthesis:
An Overview
• Photosynthesis takes place in the
chloroplast
– Thylakoids – saclike photosynthetic
membrane in the chloroplast
– Grana – stacks of thylakoids
– Stroma - the region outside of the
thylakoid membranes
High Energy Electrons
• High energy electrons produced
by the chlorophyll are highly
reactive and need a special
carrier
• NADP+ accepts a pair of high
energy electrons and a hydrogen
ion (H+) and carriers them to a
chemical reactions elsewhere in
the cells.
• NADP+
NADPH
Photosynthesis: An Overview
Photosynthesis is a complex process that can be broken
down into 2 steps:
Light-Dependent Reactions
• Occurs in the thylakoid
membranes of the
chloroplast.
• Light energy breaks apart a
molecule of H2O
– Electrons are energized
and used to convert
NAD+ into NADH.
– Hydrogen ions are used
to convert ADP into ATP.
– Oxygen is released as a
waste product.
Light-Independent Reactions
• The NADH and ATP from
the light reaction move to
the stroma.
• The leaf absorbs CO2
from the atmosphere.
• The energy from the
NADH and ATP is used to
convert CO2 into
carbohydrates.
• What is the main function
of carbohydrates?
Light-Independent
Reactions
• Each molecule of glucose
contains enough energy to
produce 36 ATP’s.
• Plants produce starch when
they need to store energy.
• Starch is a long chain of glucose.
Photosynthesis and Cell Respiration
• Cell Respiration is the opposite of
photosynthesis.
– What is the equation for
photosynthesis?
– What is the equation for
respiration.
– Respiration breaks down
carbohydrates into ATP.
Photosynthesis and Cell Respiration
• Plants perform both
photosynthesis and respiration.
– Think: It would pointless to
make carbohydrates if you did
not break them down into
energy.
Factors Affecting Photosynthesis
• Water
– No enough water means that their will
not be enough electrons and H+ to make
ATP and NADPH.
– Can too much water harm a plant?
• Temperature
– Too cold: photosynthesis occurs slowly
– Too hot: the enzyme that control
photosynthesis break down.
• Light Intensity
– Light is needed to energize the electron
from the H2O molecule.
– Light that is the wrong color or not
intense will slow down photosynthesis.
Short Answer Questions
• Explain how the ATP molecule functions similar to
rechargeable batteries? (4 points)
• Write the overall equation for photosynthesis. (2 points)
• Explain why leaves of deciduous trees change color in
the fall? (3 points)
Photosynthesis
converts
includes both
(a)
(b)
(c)
to
in which
chemical
energy
light-excited
electrons of
chlorophyll
H2O is split
in which
CO2 is fixed to
RuBP
and then
and
(d)
reduce
NADP+ to
are passed
down
(h)
using
(f)
(e)
to produce
producing
(g)
by
chemiosmosis
sugar
(G3P)
Green Solar Cells
1. What is responsible for the various shades
of green in plants?
2. What is the function of the stroma
lamellae?
3. What evidence supports the theory that
chloroplast were once invasive cells?
4. How is excess food stored?
5. How does the author define
photosynthesis?