Compare (or draw) the chemiosmotic synthesis of ATP in mitochondria and chloroplasts
the mitochondrion structure has an intermembrance space, membrane, matrix, electron transport chain, and an HTP synthase
Compare chemiosmosis and electron transport in mitochondrea and chloroplasts. In each case, a) where do the electrons come from? b) where do the electrons get their energy? c) what picks up the electrons at the end of the chain? d) how is the energy given up by the electrons used?
In chemiosmosis in mitochondrea: a) electrons come from splitting of water b) Electrons get their energy from the chemical energy of bonds in organic molecules c) electrons are passed to oxygen, which picks up H+ and forms water
summarize (or draw) photosynthesis
photosynthesis converts LIGHT ENERGY to CHEMICAL ENERGY. Then includes both LIGHT REACTIONS and CALVIN CYCLE. In the light reactions the H2O IS SPLIT and O2 IS RELEASED. Inaddition, the LIGHT EXCITED ELECTRONS OF CHLOROPHYLL are passed down to ELECTRON TRANSPORT CHAIN producing ATP by CHEMIOSMOSIS; in addition the light excited electrons of chlorophyll REDUCE NADP+ TO NADPH. In the Calvin cycle CO2 IS FIXED TO RuBP and then PGA IS REDUCED using NADPH and ATP---also the PGA IS REDUCED and produces SUGAR (G3P)
photosynthesis consumes ______ and produces _________
What is produced by reactions that take place in the thylakoids and consumed by reactions in the stroma?
In photosynthesis, __________ is oxidized and ________ is reduced
water; carbon dioxide
why is it difficult for most plants to carry out photosynthesis in very hot, dry environments such as deserts
the closing of stomata keeps CO2 from entering and O2 from leaving the plant
when light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by...
what is the role of NADP+ in photosynthesis?
it accepts electrons and carries them to the Calvin cycle
the reactions of the Calvin cycle are not directly dependent on light, but they usually do not occur at night.Why?
the calvin cycle depends on products of light reactions; NADPH and ATP from the light reactions are used by the Calvin cycle
how many "turns" of the calvin cycle are required to produce one molecule of glucose?
__________ does not occur during the calvin cycle
release of oxygen
what are the major inputs and outputs of the two stages of photosynghesis
Light reactions: light and water are inputs; ATP, NADPH and O2, are outputs. Calvin cycle: CO2, ATP, AND NADPH are inputs; G3P, ADP, and NADP+ are outputs
what do plants do with the sugar they produce in photosynthesis
Plants can break down the sugar for energy in cellular respiration or use the sugar as a raw material for making other organic molecules. Excess sugar is stored as starch
The process of photosynthesis most likely originated in....
a group of bacteria that had infolded regions of the plasma membrane containing such clusters of enzymees and molecules
_______________ are the producers of the biosphere
Plants produce O2 by _______
The leaves of plants that live in lakes and ponds are ofen covered with_________
bubbles of oxygen gas (O2)
O2 produced from photosynthesis comes from _______ and not from _________
____________ IS A REDOX PROCESS, AS IS CELLULAR RESPIRATION
What actually happens when photosynthesis converts CO2 and water into sugar and O2?
When water molecules are split apart, yielding Ox, they are actually oxidized; that is, they lose electrons, along with hydrogen ions (H+). Meanwhile, CO2 is reduced to sugar as electrons and hydrogen ions are added to it.
_________ and _________ go hand in hand
What happens during the energy releasing part of cellular respiration?
Overall, cellular respiration harvests energy stored in a glucose molecule by oxidizing the sugar and reducing O2 to H2O. This process involves a number of energy releasing redox reactions, with electrons losing potential energy as they travel down an energy "hill" from sugar to O2. Along the way, the mitochondrion uses some of the energy to synthesize ATP
The two stages of photosynthesis are linked by _______ and ______
What are the two stages of photosynthesis?
light reactions; calvin cycle
What exactly do we mean when we say that photosynthesis is powered by light energy from the sun?
sunlight is a type of energy called electromagnetic energy or radiation
________ wavelengths have more energy than _______ wavelengths
light absorbing molecules called ____ built into the thylakoid membranes, absorb some wavelengths of light and reflect or transmit other wavelengths
what are cartenoids?
ba family of pigments in the chloroplasts and are various shades of yellow and orange. they broaden the spectrum of colors that can drive photosynthesis by passing energy to chlorophyll a, as chlorophyll b does. However a more important function of cartenoids is photoprotection
what is photoprotection?
they absorb anddissipate excessive light energy that would otherwise damage chlorophyll or interact with oxygen to form reactive oxidative molecules that can damage cell molecules
why does each type of pigment absorb certain wavelenghts of light?
because it is able to absorb the specific amounts of energy in those photons
What happens when a pigment molecule absorbs a photon?
one of the pigment's electrons jumps to an energy level farther from the nucleus. In this location, the electron has more potential energy, and we say that the electron has been raised from a ground state to an excited state. The excited state is ver unstable. Generally, when isolated pigment molecules absorb light, their expected electrons drop back down to the ground state in a billionth of a second, releasing their excess energy as heat. This conversion of light energy to heat is what makes a black car so hot on a sunny day (black pigments absorb all wavelengths of light).
some isolated pigments, including chlorophyll, emit __________ as well as _____ after absorbing photons
The light harvesting complexes (a photosystem) consits of what?
pigment molecules (which may include chlorophyll a, chlorophyll b, and carotenoids) bound to proteins.
how does the photosystem function?
as a light gathering antenna, the pigments absorb photons and pass the energy from molecule to molecule until it reaches the reaction center. The reaction center complex contains a pair of chlorophyll a molecules and a molecule called the primary electron acceptor, which is capable of accepting electrons and becoming reduced. The solar powered transfer of an electron from the reaction center chlorophyll a to the primary electron acceptor is the first step of the light reactions
What are the two types of photosystems that have been identified?
Photosystem II-the first function despite it being labeled as II. the chlorophyll a of the reaction center is called P680 because the light it absorbs best is red light with a wavelength of 680 nm.
Photosystem I-the second function--the reaction center is called P700 because the wavelength of light it absorbs best is 700 nm(in the far red part of the spectrum)
Explain the flow of electrons between the two photosystems embedded in a thylakoid membrane
1-a pigment molecule in a light harvesting complex absorbs a photon of light. The energy is passed to other pigment molecules and finally to the reaction center of photosystem II, where it excites an electron of chlorophyll P680 to a higher energy state.
2-This electron is captured by the primary electron acceptor
3-water is split, and its electrons are supplied one by one to P680, each replacing an electron lost to the primary electron acceptor. The oxygen atom combines with an oxygen from another split water molecule to form a molecule of O2
4-Each photoexcited electron passes from photosystem II to photosystem I via an electron transport chein. The exergonic "fall" of electrons provides energy for the synthesis of ATP by pumping H+ across the membrane
5-Meanwhile, light energy excites an electron of chlorophyll P700 in the reaction center of photosystem I. The primary electron acceptor captures the electron, and an electron from the bottom of the electron transport chain reeplaces the lost electron in P7010
6-The excited electron of photosystem I is passed through a short electron transport chain to NADP+, reducing it to NADPH
What are the 3 products of the photosystems (light reactions)
ATP, NADPH, O2
_____________ powers ATP sysnthesis in the light reactions in the chloroplasts
As photoexcited electrons are passed down the electron transport chain connecting the two photosystems, _______________ are pumped across the membrane from the stroma into the thylakoid space and generates a concentration gradient across the membrane
how does photophosphorylation compare with oxidative phosphorylation?
in cellular respiration, the high energy electrons passed down the electron transport chain come from the ooxidation of food molecules. In photosynthesis, light energy is used to drive electrons to the top of the transport chain. Mitochondria transfer chemical energy from food to ATP; chloroplasts transform light energy into chemical energy of ATP. The light driven flow of electrons throught the two photosystems, the final electron acceptor is NADP+, not Ox as in cellular respiration. Electrons do not end up at a low energy level in H2O, as they do in respiration. Instead, they are stored at a high state of potential energy in NADPH
______ and _____ power sugar synthesis in the Calvin cycle
What are the steps of the Calvin cycle?
carbon fixation; reduction; release of one molecule of G3P; regeneration RuBP
What does the chloroplast make while integrating the two stages of photosynthesis?
sugar from CO2
all but a few microscopic organisms depend on the food making machinery of ________
plants make more food than they actually need and stockpile it as _______ in roots, tubers, and fruits
In hot climates, plant ___ close to reduce water loss so oxygen builds up
Unlike photosynthesis, photorespiration produces no ___, and unlike respiration, it produces no _____
Some plants have evolved a means of _________ that saves water during photosynthesis
Examples of the CAM plants are
pineapples and cacti
The ________- results from solar energy warming our planet
The rise in CO2 is mostly due to the combustion of ________
carbon based fossil fuels
The consequences of continued rise of green house gases will be...
melting of polar ice, changing weather patterns, and spread of tropical disease
_______ provides a protective layer (the ozone layer) in our atmosphere to filter out powerful ultraviolet radiation
________ showed that industrial chemicals called _________ or CFC's, deplete the ozone layer
Dr Molina; chlorofluorocarbons