Copyright Pearson Prentice Hall
8-1 Energy and Life
Copyright Pearson Prentice Hall
Living things need energy to survive.
This energy comes from food. The energy in most food comes from the sun.
Plants are able to use light energy from the sun to produce food.
Copyright Pearson Prentice Hall
autotrophs –Organisms that make their own food, such as plants.
heterotrophs must get energy from the foods they consume. Ex. Animals
I can make my
own food!!
I will eat you!!
Copyright Pearson Prentice Hall
Chemical Energy and ATP
Energy comes in many forms including light, heat, and electricity. Energy can be stored in chemical compounds, too.
Chemical Energy and ATP
An important chemical compound that cells use to store and release energy is adenosine triphosphate, abbreviated ATP.
Adenosine triphosphate or ATP is used by all types of cells as their basic energy source.
ATPMovie
ATP consists of:•adenine•ribose (a 5-carbon sugar)•3 phosphate groups
Adenine
ATP
Ribose 3 Phosphate groups
Chemical Energy and ATP
The three phosphate groups are the key to ATP's ability to store and release energy.
Copyright Pearson Prentice Hall
Storing EnergyADP has two phosphate groups instead of three.A cell can store small amounts of energy by adding a phosphate group to ADP.
ADP ATP
Energy
Energy
Partiallycharged battery
Fullycharged battery
+
Adenosine Diphosphate (ADP) + Phosphate
Adenosine Triphosphate (ATP)
Copyright Pearson Prentice Hall
Chemical Energy and ATP
Releasing Energy
Energy stored in ATP is released by breaking off the third phosphate.
P
ADP
2 Phosphate groups
Copyright Pearson Prentice Hall
Chemical Energy and ATP
The energy from ATP is needed for many cellular activities, including active transport across cell membranes, protein synthesis and muscle contraction.
ATP’s characteristics make it exceptionally useful as the basic energy source of all cells.
Copyright Pearson Prentice Hall
Using Biochemical Energy
Using Biochemical Energy
Most cells have only a small amount of ATP, because it is not a good way to store large amounts of energy.Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose.
Copyright Pearson Prentice Hall
8-1
Organisms that make their own food are called
a. autotrophs.
b. heterotrophs.
c. decomposers.
d. consumers.
Copyright Pearson Prentice Hall
8-1
Most autotrophs obtain their energy from
a. chemicals in the environment.
b. sunlight.
c. carbon dioxide in the air.
d. other producers.
Copyright Pearson Prentice Hall
8-1
How is energy released from ATP?
a. A phosphate is added.
b. An adenine is added.
c. A phosphate is removed.
d. A ribose is removed.
Copyright Pearson Prentice Hall
8-1
How is it possible for most cells to function with only a small amount of ATP?
a. Cells do not require ATP for energy.
b. ATP can be quickly regenerated from ADP and P.
c. Cells use very small amounts of energy.
d. ATP stores large amounts of energy.
Copyright Pearson Prentice Hall
8-1
Compared to the energy stored in a molecule of glucose, ATP stores
a. much more energy.
b. much less energy.
c. about the same amount of energy.
d. more energy sometimes and less at others.
Copyright Pearson Prentice Hall
8-2 Photosynthesis: An Overview
Copyright Pearson Prentice Hall
8-2 Photosynthesis:
An Overvie
w
The key cellular process identified with energy production is photosynthesis.
Photosynthesis is the process in which green plants use the energy of sunlight to convert water and carbon dioxide into sugar and oxygen.
Van Helmont’s Experiment
a. In the 1600s, Jan van Helmont wanted to find out if plants grew by taking material out of the soil.
b. He determined the mass of a pot of dry soil and a small seedling, planted the seedling in the pot, and watered it regularly.
c. After five years, the seedling was a small tree and had gained 75 kg, but the soil’s mass was almost unchanged.
Investigating PhotosynthesisResearch into photosynthesis began centuries ago.
Copyright Pearson Prentice Hall
Investigatin
g Photosynth
a.Van Helmont concluded that the gain in a plants’ mass comes from water because water was the only thing he had added.
b. His experiment accounts for the “hydrate,” or water, portion of the carbohydrate produced by photosynthesis.
Copyright Pearson Prentice Hall
Investigatin
g Photosynth a. Although van Helmont did not realize it,
carbon dioxide in the air also made a major contribution to the mass of his tree.
b. In photosynthesis, the carbon in carbon dioxide is used to make sugars and other carbohydrates.
c. Van Helmont had only part of the story, but he had made a major contribution to science.
Copyright Pearson Prentice Hall
Joseph Priestley discovered oxygen and that plants release it.More than 100 years after van Helmont’s experiment-- a. Priestley took a candle, placed a glass jar over
it, and watched as the flame gradually died out.
b. He reasoned that the flame needed something in the air to keep burning and when it was used up, the flame went out. That substance was oxygen.
Copyright Pearson Prentice Hall
a. Priestley then placed a live sprig of mint under the jar and allowed a few days to pass.
b. He found that the candle could be relighted and would remain lighted for a while.
c. The mint plant had produced the substance required for burning. In other words, it had released oxygen.
Copyright Pearson Prentice Hall
Jan Ingenhousz
a.Later, Jan Ingenhousz showed that the effect observed by Priestley occurred only when the plant was exposed to light.
b. The results of both Priestley’s and Ingenhousz’s experiments showed that light is necessary for plants to produce oxygen.
Copyright Pearson Prentice Hall
Investigatin
g Photosynth
The experiments performed by van Helmont, Priestley, and Ingenhousz led to work by other scientists who finally discovered that, in the presence of light, plants transform carbon dioxide and water into carbohydrates, and they also release oxygen.
The equation for photosynthesis is
6CO2 + 6H2O C6H12O6 + 6O2carbon water sugars oxygendioxide
Light
Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen.
Photosynthesis activity
Copyright Pearson Prentice Hall
O2
CO2+
H20Sugar
ADPNADP+
Light-Dependent Reactions
(thylakoids)
H2O
ATPNADPH
Calvin Cycle
(stroma)
Light energy
Copyright Pearson Prentice Hall
Light and
Pigments
In addition to water and carbon dioxide, photosynthesis requires light and chlorophyll.
Copyright Pearson Prentice Hall
Plants gather the sun's energy with light-absorbing molecules called pigments.
The main light-absorbing pigment in plants is chlorophyll.
There are two main types of chlorophyll: chlorophyll a chlorophyll b
Copyright Pearson Prentice Hall
Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum.
Wavelength (nm)
100
80
60
40
20
0
400 450 500 550 600 650 700 750Wavelength (nm)
Estim
ated
Abs
orpt
ion
(%)
Copyright Pearson Prentice Hall
Chlorophyll does not absorb light well in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green.
Wavelength (nm)
100
80
60
40
20
0
400 450 500 550 600 650 700 750Wavelength (nm)
Estim
ated
Abs
orpt
ion
(%)
Copyright Pearson Prentice Hall
Light is a form of energy, so any compound that absorbs light also absorbs energy from that light.
When chlorophyll absorbs light, much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons.
These high-energy electrons are what make photosynthesis work.
Copyright Pearson Prentice Hall
8-2
In van Helmont's experiment, most of the added mass of the tree came from
a. soil and carbon dioxide.
b. water and carbon dioxide.
c. oxygen and carbon dioxide.
d. soil and oxygen.
Copyright Pearson Prentice Hall
8-2
Plants use the sugars produced in photosynthesis to make
a. oxygen.
b. starches.
c. carbon dioxide.
d. protein.
Copyright Pearson Prentice Hall
8-2
The raw materials required for plants to carry out photosynthesis are
a. carbon dioxide and oxygen.
b. oxygen and sugars.
c. carbon dioxide and water.
d. oxygen and water.
Copyright Pearson Prentice Hall
8-2
The principal pigment in plants is
a. chloroplast.
b. chlorophyll.
c. carotene.
d. carbohydrate.
Copyright Pearson Prentice Hall
8-2
The colors of light that are absorbed by chlorophylls are
a. green and yellow.
b. green, blue, and violet.
c. blue, violet, and red.
d. red and yellow.
Copyright Pearson Prentice Hall
8-3 The Reactions of Photosynthesis
Copyright Pearson Prentice Hall
Inside a Chloroplast
In plants, photosynthesis takes place inside chloroplasts.
Plant
Plant cells
Chloroplast
Chloroplast movie
Copyright Pearson Prentice Hall
Chloroplasts contain thylakoids—saclike photosynthetic membranes.
Chloroplast
Singlethylakoid
Copyright Pearson Prentice Hall
Inside a
ChloroplastThylakoids are arranged in stacks known as
grana. A singular stack is called a granum.
Granum
Chloroplast
Copyright Pearson Prentice Hall
Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast.
Chloroplast
Photosystems
Copyright Pearson Prentice Hall
The long chain of photosynthesis reactions is divided into two parts
The light-dependent reactions take place within the thylakoid membranes.
The Calvin cycle takes place in the stroma, which is the region outside the thylakoid membranes.
Copyright Pearson Prentice HallPHOTOSYNTHESIS
Chloroplast
LightH2O
O2
CO2
Sugars
NADP+
ADP + PLight-
dependent reactions
Calvin cycle
Copyright Pearson Prentice Hall
Electron
Carriers
When electrons in chlorophyll absorb sunlight, the electrons gain a great deal of energy.
Cells use electron carriers to transport these high-energy electrons from chlorophyll to other molecules.
Copyright Pearson Prentice Hall
Electron
Carriers
One carrier molecule is NADP+.Electron carriers, such as NADP+,
transport electrons.NADP+ accepts and holds 2 high-energy
electrons along with a hydrogen ion (H+). This converts the NADP+ into NADPH.
Copyright Pearson Prentice Hall
Electron
Carriers
The conversion of NADP+ into NADPH is one way some of the energy of sunlight can be trapped in chemical form.
The NADPH carries high-energy electrons to chemical reactions elsewhere in the cell.
These high-energy electrons are used to help build a variety of molecules the cell needs, including carbohydrates like glucose.
Copyright Pearson Prentice Hall
The light-dependent reactions require light.
The light-dependent reactions produce oxygen gas and convert ADP and NADP+ into the energy carriers ATP and NADPH.
Light-dependent
movie
Copyright Pearson Prentice Hall
Light-Depen
dent Reacti
onsPhotosystems I and II carry out the light-dependent reactions and are in the thylakoid membrane.
Copyright Pearson Prentice Hall
Photosystem II
Light-Depen
dent Reacti
onsPhotosynthesis begins when pigments in
photosystem II absorb light, increasing their energy level.
Photosystem II
These high-energy electrons are passed on to the electron transport chain.
Electroncarriers
High-energy electron
Copyright Pearson Prentice Hall
Photosystem II
2H2O
Enzymes on the thylakoid membrane break water molecules into:
Electroncarriers
High-energy electron
Copyright Pearson Prentice Hall
Photosystem II
2H2O
hydrogen ionsoxygen atomsenergized electrons
+ O2
Electroncarriers
High-energy electron
Copyright Pearson Prentice Hall
Photosystem II
2H2O+ O2
The energized electrons from water replace the high-energy electrons that chlorophyll lost to the electron transport chain.
High-energy electron
Copyright Pearson Prentice Hall
Photosystem II
2H2O
As plants remove electrons from water, oxygen is left behind and is released into the air.
+ O2
High-energy electron
Copyright Pearson Prentice Hall
Photosystem II
2H2O
The hydrogen ions left behind when water is broken apart are released inside the thylakoid membrane.
+ O2
High-energy electron
Copyright Pearson Prentice Hall
Photosystem II
2H2O
Energy from the electrons is used to transport H+ ions from the stroma into the inner thylakoid space.
+ O2
Copyright Pearson Prentice Hall
Photosystem II
2H2O
High-energy electrons move through the electron transport chain from photosystem II to photosystem I.
+ O2
Photosystem I
Copyright Pearson Prentice Hall
2H2O
Pigments in photosystem I use energy from light to re-energize the electrons.
+ O2
Photosystem I
Copyright Pearson Prentice Hall
2H2O
NADP+ then picks up these high-energy electrons, along with H+ ions, and becomes NADPH.
+ O2
2 NADP+
2 NADPH2
Copyright Pearson Prentice Hall
2H2O
As electrons are passed from chlorophyll to NADP+, more H+ ions are pumped across the membrane.
+ O2
2 NADP+
2 NADPH2
Copyright Pearson Prentice Hall
2H2O
Soon, the inside of the membrane fills up with positively charged hydrogen ions, which makes the outside of the membrane negatively charged.
+ O2
2 NADP+
2 NADPH2
Copyright Pearson Prentice Hall
2H2O
The difference in charges across the membrane provides the energy to make ATP
+ O2
2 NADP+
2 NADPH2
Copyright Pearson Prentice Hall
2H2O
H+ ions cannot cross the membrane directly.
+ O2
ATP synthase
2 NADP+
2 NADPH2
Copyright Pearson Prentice Hall
2H2O
The cell membrane contains a protein called ATP synthase that allows H+ ions to pass through it
+ O2
ATP synthase
2 NADP+
2 NADPH2
Copyright Pearson Prentice Hall
2H2O
As H+ ions pass through ATP synthase, the protein rotates.
+ O2
ATP synthase
2 NADP+
2 NADPH2
Copyright Pearson Prentice Hall
2H2O
As it rotates, ATP synthase binds ADP and a phosphate group together to produce ATP.
+ O2
2 NADP+
2 NADPH2
ATP synthase
ADP
Copyright Pearson Prentice Hall
2H2O
Because of this system, light-dependent electron transport produces not only high-energy electrons but ATP as well.
+ O2
ATP synthase
ADP2 NADP+
2 NADPH2
Copyright Pearson Prentice Hall
The light-dependent reactions use water, ADP, and NADP+.
The light-dependent reactions produce oxygen, ATP, and NADPH.These compounds provide the energy to build energy-containing sugars from low-energy compounds.
Copyright Pearson Prentice Hall
The Calvin Cycle ATP and NADPH formed by the light-
dependent reactions contain an abundance of chemical energy, but they are not stable enough to store that energy for more than a few minutes.
During the Calvin cycle plants use the energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time.
Copyright Pearson Prentice Hall
The Calvin cycle uses ATP and NADPH from the light-dependent reactions to produce high-energy sugars.
Because the Calvin cycle does not require light, these reactions are also called the light-independent reactions.
Calvin Cycle Movie
Copyright Pearson Prentice Hall
Six carbon dioxide molecules enter the cycle from the atmosphere and combine with six 5-carbon molecules.
CO2 Enters the Cycle
Copyright Pearson Prentice Hall
The result is twelve 3-carbon molecules, which are then converted into higher-energy forms.
Copyright Pearson Prentice Hall
The energy for this conversion comes from ATP and high-energy electrons from NADPH.
Energy Input
12 NADPH
12
12 ADP
12 NADP+
Copyright Pearson Prentice Hall
Two of twelve 3-carbon molecules are removed from the cycle.
Energy Input
12 NADPH
12
12 ADP
12 NADP+
Copyright Pearson Prentice Hall
The Calvin Cycle
The molecules are used to produce sugars, lipids, amino acids and other compounds.
6-Carbon sugar produced
Sugars and other compounds
12 NADPH
12
12 ADP
12 NADP+
Copyright Pearson Prentice Hall
The 10 remaining 3-carbon molecules are converted back into six 5-carbon molecules, which are used to begin the next cycle.
5-Carbon MoleculesRegenerated
Sugars and other compounds
6
6 ADP12 NADPH
12
12 ADP
12 NADP+
Copyright Pearson Prentice Hall
The two sets of photosynthetic reactions work together.The light-dependent reactions trap
sunlight energy in chemical form. The light-independent reactions use that
chemical energy to produce stable, high-energy sugars from carbon dioxide and water.
Copyright Pearson Prentice Hall
Many factors affect the rate of photosynthesis, including:• Water• Temperature• Intensity of light
Photosynthesis overview movie
Copyright Pearson Prentice Hall
8-3
In plants, photosynthesis takes place inside the
a. thylakoids.
b. chloroplasts.
c. photosystems.
d. chlorophyll.
Copyright Pearson Prentice Hall
8-3
Energy to make ATP in the chloroplast comes most directly from
a. hydrogen ions flowing through an enzyme in the thylakoid membrane.
b. transfer of a phosphate from ADP.
c. electrons moving through the electron transport chain.
d. electrons transferred directly from NADPH.
Copyright Pearson Prentice Hall
8-3
NADPH is produced in light-dependent reactions and carries energy in the form ofa. ATP. b. high-energy electrons. c. low-energy electrons. d. ADP.
Copyright Pearson Prentice Hall
8-3
What is another name for the Calvin cycle?
a. light-dependent reactions
b. light-independent reactions
c. electron transport chain
d. photosynthesis
Copyright Pearson Prentice Hall
8-3
Which of the following factors does NOT directly affect photosynthesis?
a. wind
b. water supply
c. temperature
d. light intensity
Recommended