Chapter 7-Photosynthesis: using light to make food (biology 1050) 10/26/20
In photosynthesis, what happens in a redox process
*H20 is oxidized and CO2 is reduced -the water molecule is split and the carbon dioxide is gonna pick up the hydrogens to form carbohydrates when it becomes reduced
what is the Calvin cycle?
It is a cyclic series of reactions that assembles sugar molecules using CO2 and the energy-rich products of the light reactions(ATP and NADPH) to make the sugar molecule G3P
Photons
a fixed quantity of light energy
Different pigments absorb light of different wavelengths, and chloroplasts contain more than one type of ... What are they?
pigment -chlorophyll a and b
Photophosphorylation
the production of ATP by chemiosmosis during the light reactions of photosynthesis
Thylakoids purpose:
used to convert light energy to chemical energy.
7.13 Rising atmospheric levels of carbon dioxide may affect plants in various ways- How do scientists study the effects of rising CO2 levels?
using laboratory growth chambers and field studies
A light-harvesting complex consists of ...
various pigment molecules bound to proteins
The _______ occur on and inside the thylakoids, producing ____ and ______ for the ________, which takes place in the stroma.
*-light reactions -ATP -NADPH -Calvin cycle
Chloroplasts are surrounded by a double membrane and contain stacks of _______ and a thick fluid called _______
*-thylakoids -stroma
PROCESS: The light reactions take place within the thylakoid membrane:
*Look at. 7.9 for the picture* Photosystem II gets energized by chlorophyll's capturing the light energy from the sun and that energy is used to split water molecules and this reaction is called a oxidation reaction-the water molecule gets oxidized, splits the protons from the oxygen, releases the oxygen and the electrons build up and transported through an electron transport chain -In the process of these electrons being transported through the electron transport chain, protons are pumped into the lumen (or inside of the thylakoid as electrons get passed down the transport chain -the protons that build up inside the thylakoid are gonna generate a concentration gradient -these protons are gonna wanna get out of the thylakoid so there's an integral protein present inside the thylakoid membrane called ATP synthase and the protons are going to go through ATP synthase -as the proteins go through ATP synthase, ADP + P is going to combine to ATP -the ATP that is generated from the buildup of proteins is going to be used in the Calvin cycle that occurs in the stroma -the electrons are also going to be transferred to a second photosystem called photosystem I. The electrons are going to be re-energized by light energy as well but this time, the energy that builds up in photosystem I is going to be used to drive the reduction of NADP + H+ to reduce it to NADPH -The NADPH and the ATP are going to be used in the Calvin cycle -this reaction occurs in the thylakoid membrane
Photoautotrophs
*Organism that obtains energy from sunlight and carbon from CO2 using the process of photosynthesis -plants, algae, and some photosynthetic protists and bacteria are this -producers of food consumed by heterotrophic organisms
Carbon fixation
*The incorporation of carbon into organic compounds.
7.2 Photosynthesis occurs in chloroplasts in plant cells- Chlorophyll:
*a light-absorbing pigment in the chloroplasts that plays a central role in converting solar energy to chemical energy -A leaf's green color comes from chlorophyll
7.4 Photosynthesis is a redox process- Both photosynthesis and cellular respiration involve...
*oxidation-reduction reactions
Using a heavy isotope of oxygen, O-18, scientists were able to follow the fate of _________
*oxygen atoms during photosynthesis.
a primary electron acceptor receives
*photoexcited electrons from reaction-center chlorophyll a
In living cells, solar energy is converted to the chemical energy of sugar through the process of...
*photosynthesis
7.7 Photosystems capture solar energy- In the thylakoid membrane, chlorophyll molecules are organized into clusters called .....
*photosystems
What were the results of the O-18 experiment?
*plants produced O2 containing O-18 only when supplied with labeled H2O, never when provided with labeled CO2
How do electrons get shuttled from photosystem 2 to photosystem 1?
*provide energy to make ATP, and then reduce NADP+ to NADPH
7.0 Sunlight can provide renewable fuel for our cars: Biofuels-
*renewable energy sources obtained from living material -this living material is primarily plant material
When we obtain energy from biofuels..
*we are tapping into the energy of the sun
_________ is used as an energy source and _________ provides high-energy electrons for reducing CO2 to sugar
-ATP -NADPH
C4 and CAM plants first fix ____ into _____________ and that provides CO2 to the Calvin cycle even when stomata close on hot, dry days
-CO2 -four-carbon compounds
What happens in a CAM plant?
-adapted to very dry climates. -A CAM plant conserves water by opening its stomata and admitting CO2 only at night. CO2 is fixed into a four-carbon compound, which banks CO2 at night and releases it during the day. Thus, the Calvin cycle can operate, even with the leaf's stomata closed during the day.
Journey inside a leaf process:
-chloroplasts are concentrated in the cells of the mesophyll, the green tissue in the interior of the leaf. CO2 enters the leaf, and O2 exits, by way of tiny pores called stomata. Water absorbed by the roots is delivered to the leaves in veins.
In C3 plants, a ____ in CO2 and _____ in O2 when stomata close divert the Calvin cycle to _________
-drop -rise -photorespiration
Photosystem Ⅱ regains _____ as water is _____ and O2 released.
-electrons -split
What molecules are linked together to make cellulose? What is cellulose the main component of?
-glucose -the main component of cell walls.
7.8 Two photosystems connected by an electron transport chain convert light energy to the chemical energy of ATP and NADPH- A mechanical analogy of the light reactions
. Starting on the left, you see that the large yellow photon mallet provides the energy to boost an electron from photosystem II to a higher energy level, where it is caught by the primary electron acceptor standing on the platform. The electron is loaded onto an electron transport chain "ramp" leading to photosystem I. As electrons roll down the ramp, they release energy that is used for the production of ATP. When an electron reaches photosystem I, another photon mallet pumps it up to a higher energy level, where it is caught by a primary electron acceptor on the photosystem I platform. From there, the photoexcited electrons are thrown into a bucket to produce NADPH.
Classes of photosynthetic organisms:
1) terrestrial plants: tropical forest plants 2) aquatic plants: kelp plants present in salt water-forms extensive underwater "forests" 3) -bacteria that contain chloroplasts-important producers in freshwater and marine ecosystems.
Steps of the Calvin Cycle
1. carbon fixation-the enzyme rubisco attaches CO2 to RuBP -gaseous carbon dioxide is captured and is incorporated into sugar molecules that will be formed 2. reduction-ATP and NADPH are used to reduce the three-carbon molecule to G3P. -gain of an electron 3. release of G3P-for every three CO2 molecules fixed, one G3P molecule leaves the cycle as product. 4. Regeneration of RuBP-the remaining five G3P molecules are rearranged, using energy from ATP, to regenerate three molecules of RuBP.
7.12 Photosynthesis provides food and O2 for almost all living organisms- Cellular respiration in the mitochondria of plant cells uses about...
50% of the carbohydrates made by photosynthesis
CHECKPOINT: For chloroplasts to produce sugar from carbon dioxide in the dark, they would need to be supplied with _________ and _________ .
ATP . . . NADPH
CHECKPOINT: Why would you expect photorespiration on a hot, dry day to occur less in C4 and CAM plants than in C3 plants?
Because of their initial fixing of carbon, both C4 and CAM plants can supply rubisco with CO2. When a C3 plant closes its stomata, CO2 levels drop and O2 rises, making it more likely that rubisco will add O2 to RuBP.
The burning of the fossil products of photosynthesis and the destruction of vast swaths of forests pour enormous quantities of ___ into the atmosphere.
CO2
CHECKPOINT: How do the reactant molecules of photosynthesis reach the chloroplasts in leaves?
CO2 enters leaves through stomata, and H2O enters the roots and is carried to leaves through veins.
NADPH temporarily stores electrons and provides "reducing power" to the _______
Calvin cycle.
In cellular respiration, what happens in a redox reaction?
Cellular respiration harvests energy stored in a glucose molecule
_______ is the most abundant organic molecule in a plant—and probably on the surface of the planet.
Cellulose
CHECKPOINT: A key characteristic of science is the use of multiple lines of evidence in the testing of hypotheses. Describe three research methods that scientists use to test the hypothesis that increasing CO2 levels will affect the growth of plants.
Laboratory growth chambers, field studies in areas where CO2 levels vary naturally, and large-scale field studies in which CO2 levels are manipulated
CHECKPOINT: What do "self-feeding" photoautotrophs require from the environment to make their own food?
Light, CO2, and H2O. (Minerals are also required)
CHECKPOINT: Photosynthesis produces billions of tons of carbohydrate a year. Where does most of the mass of this huge amount of organic matter come from?
Mostly from CO2 in the air, which provides both the carbon and oxygen in carbohydrate. Water supplies only the hydrogen.
CHECKPOINT: Looking at the model of the light reactions in Figure 7.8, explain why two photons of light are required in the movement of electrons from water to NADPH.
One photon excites an electron from photosystem II, which is passed down an electron transfer chain to photosystem I. A second photon excites an electron from photosystem I, which is then used in the reduction of NADP+ to NADPH.
autotrophs
Organisms that make their own food -primarily plants make their own food
CHECKPOINT: Explain this statement: No process is more important to the welfare of life on Earth than photosynthesis.
Photosynthesis is the ultimate source of the food for almost all organisms and the O2 they need for cellular respiration.
What happens in the process of photosynthesis?
Plants, algae, and some protists and prokaryotes convert light energy to chemical energy that is stored in sugars made from carbon dioxide and water
What also serves as starting material for making other organic molecules?
Sugars, such as plants proteins and lipids
CHECKPOINT: Explain the greenhouse effect.
Sunlight warms Earth's surface, which radiates heat to the atmosphere. CO2 and other greenhouse gases absorb and radiate some heat back to Earth.
NADP+
Temporarily stores energized electrons produced during the light reactions -an electron acceptor -functions as a universal electron carrier, accepting electrons and hydrogen atoms to form NADPH
greenhouse effect
The warming of Earth due to the atmospheric accumulation of carbon dioxide and certain other gases -Solar radiation passes through the atmosphere and warms Earth's surface
Climate change
a long-term directional change to the global climate that lasts for three decades or more -Increase in temperature and change in weather patterns all around the planet
The reaction-center complex contains ...
a pair of special chlorophyll a molecules and a molecule called the primary electron acceptor
photosystems consists of
a reaction-center complex surrounded by a number of light-harvesting complexes.
Chlorophyll b
absorbs mainly blue and orange light -broadens the range of light that a plant can use by conveying absorbed energy to chlorophyll a
Chloroplasts also contain pigments called...
carotenoids -various shades of yellow and orange.
7.10 ATP and NADPH power sugar synthesis in the Calvin cycle- The Calvin cycle function within the...
chloroplast
All green parts of a plant have ________ in their cells
chloroplasts
Photosynthesis, the subject of this chapter, can be thought of as both a cause and a potential solution to ...
climate change
The ongoing global warming is a major aspect of...
climate change
Photoautotrophs not only feed us; they also ....
clothe us (think cotton), house us (think wood), and provide energy for warmth, light, transport, and manufacturing.
The Light Reactions: Converting Solar Energy to Chemical Energy 7.6 Visible radiation absorbed by pigments drives the light reactions- Sunlight is a type of energy called ...
electromagnetic energy or radiation.
CHECKPOINT: Which redox process, photosynthesis or cellular respiration, is exergonic? Is endergonic?
exergonic: cellular respiration endergonic: photosynthesis
What happens in C4 plants?
fix CO2 into a four-carbon compound -When the weather is hot and dry, a C4 plant keeps its stomata mostly closed, thus conserving water. -It continues making sugars by photosynthesis
In many places, thylakoids are concentrated in stacks called
grana(granum)
CO2 and other gases in the atmosphere create the ...
greenhouse effect
7.3 Scientists traced the process of photosynthesis using isotopes- Experiments using both __________ helped determine the details of the process of photosynthesis
heavy and radioactive isotopes
Bioethanol is commonly added to gasoline to ...
increase fuel efficiency while decreasing vehicle emissions
Some scientists are studying the long-term field studies of what?
long-term field studies enable scientists to assess the effects of CO2 levels on natural ecosystems
7.5 Photosynthesis occurs in two stages, which are linked by ATP and NADPH- Light reactions:
occur on and inside the thylakoids that include the steps in which solar energy is absorbed and converted to the chemical energy of ATP and NADPH, releasing oxygen in the process
Humans and other animals make none of their own food and are totally dependent on the ...
organic matter made by photosynthesizers
Heterotrophs
organisms that cannot make their own food *-consumers that feed on plants or animals or decompose organic material
Chlorophyll a
participates directly in the light reactions -absorbs mainly blue-violet and red light.
Light also behaves as discrete packets of energy called ....
photons
Most important function of carotenoids
photoprotection from excessive light
As O2 builds in a C3 plant, what happens?
photorespiration happens -this is when rubisco consumes O2 and releases CO2 -it yields no sugar
7.14 Reducing both fossil fuel use and deforestation may moderate climate change- Greenhouses are used to grow plants when ...
the weather outside is too cold.
Suspended in the stroma is a system of interconnected membranous sacs, called ______
thylakoids
True or false: poison ivy is predicted to become both more abundant and more toxic ("itchy") as atmospheric CO2 levels rise.
true
Wavelength
The distance between the crests of electromagnetic waves
Using carbon from CO2, electrons from NADPH, and energy from ATP, the cycle constructs ....
G3P, which is used to build glucose and other organic molecules
CHECKPOINT: Explain why the large number of ATP and NADPH molecules used during the Calvin cycle is consistent with the value of glucose as an energy source.
Glucose is a highly reduced molecule, storing lots of potential energy in its electrons. To reduce CO2 to glucose, much energy and reducing power is required.
CHECKPOINT: What color of light is least effective at driving photosynthesis? Explain.
Green, because it is mostly transmitted and reflected—not absorbed—by photosynthetic pigments.
CHECKPOINT: Compared with a solution of isolated chlorophyll, why do intact chloroplasts not release heat and light when illuminated?
In the chloroplasts, a light-excited electron from the reaction-center chlorophyll molecules is passed to a primary electron acceptor before it can fall back to the ground state.
How is ATP powered?
The concentration gradient drives H+ back through ATP synthase
An international agreement reached at the Paris climate conference of 2015 seeks to ...
reduce greenhouse gas emissions and limit global warming
What did van Niel's hypothesis prove that the scientists experimented?
showed that the O2 released during photosynthesis comes from water and not from CO2.
An Introduction to Photosynthesis 7.1 Photosynthesis powers most life on Earth: Life on Earth is __________.
solar powered
In the chloroplast, an envelope of two membranes encloses an inner compartment, which is filled with a thick fluid called _____
stroma
The Calvin cycle occurs in the .....
stroma of the chloroplast
all life on the planet is dependent on the ...
sun
7.9 VISUALIZING THE CONCEPT: The light reactions take place within the thylakoid membranes- What happens in photophosphorylation?
the electron transport chain pumps H+ into the thylakoid space
electromagnetic spectrum
the full range of electromagnetic wavelengths from very short gamma rays to very long-wavelength radio waves.
7.11 Other methods of carbon fixation have evolved in hot, dry climates- What happens in C3 plants?
the plants close their stomata due to the hot, dry weather (this adaptation reduces water loss and helps prevent dehydration) -there is also a drop in CO2 and rise in O2
