Studied by 6 people
photosynthesis
a biochemical process for building carbohydrates using energy from sunlight and carbon dioxide (CO2) taken from the air
photosynthesis formula
Energy + Carbon dioxide (6CO2) + Water (6H2O) —> Glucose (C6H12O6) + Oxygen (6O2)
reduction reactions
reactions in which a molecule gains both electrons and energy
oxidation reactions
reactions in which a molecule loses electrons and releases energy
NADPH (nicotinamide adenine dinucleotide phosphate)
an electron carrier in many biochemical reactions; the reducing agent used in the Calvin Cycle during photosynthesis; exists in two forms, NADP+ (oxidized form), and NADPH (reduced form)
light reactions
chemical reaction during photosynthesis where energy from sunlight is used to synthesize NADPH and ATP
calvin cycle
the process in which carbon dioxide is reduced to synthesize carbohydrates, with ATP and NADPH as the energy sources
photosynthetic electron transport chain
a series of redox reactions in which light energy absorbed by chlorophyll is used to power the movement of electrons; in oxygenic photosynthesis, the electrons ultimately come from water, and the terminal electron acceptor is NADP+
inputs of the light dependent reaction
sunlight, NADP+, ADP, and water
outputs of the light-dependent reaction
NADPH, ATP, and oxygen gas
inputs of the Calvin cycle
NADPH, ATP, and carbon dioxide (CO2)
outputs of the Calvin cycle
carbohydrates, as well as NADP+ and ADP
thylakoid
highly folded structures that are made up of stacks of pancake-like grana; folding of thylakoid membrane greatly increases its surface area, allowing for the production of high levels of NADPH and ATP
stroma
region of the chloroplast that surrounds the thylakoid, where the Calvin cycle takes place
visible light
the portion of the electromagnetic spectrum apparent to our eyes
how coloring in pigements work
pigments look colored because they reflect light enriched in the wavelengths that they do not absorb
chlorophyll
the major photosynthetic pigment; the major entry point for light energy in photosynthesis; has a large, light-absorbing head that contains magnesium atom at its center and a long hydrocarbon tail
reaction center
specially configured chlorophyll molecules where light energy is converted into electron transport
photosystems
a protein-pigment complex that absorbs light energy and uses it to drive electron transport
photosystem II
accepts electrons from water, with oxygen given off as a by-product; passes electrons to photosystem I
photosystem I
captures energy which allows electrons to be transferred to NADP+ to form NADPH; photosystem I transfers electrons given by photosystem II to NADP+, forming NADPH
Z scheme
the use of water as an electron donor requires input of light energy at two places in the photosynthetic electron transport chain. Absorption of light energy by photosystem II allows electrons pulled from water to enter the photosynthetic electron transport chain. A second input of light energy by photosystem I produces electron donor molecules capable of reducing NADP+ to NADPH. As a result, energy levels increase, decrease, and increase again, resembling the letter Z on its side.
Two features of the photosynthetic electron transport chain
first, the oxidation of water (H2O) by photosystem II releases protons (H+) and oxygen (O2) directly into the thylakoid space; second, as electrons are transferred along the photosynthetic electron transport chain, protons are pumped from the outside (stroma) to the inside (thylakoid space) of the thylakoid
FIGURE 16.9 Electron transport, proton accumulation, and ATP synthesis
As electrons are passed along the photosynthetic electron transport chain, protons (H+) accumulate in the thylakoid space due to the oxidation of water and the pumping of protons. These protons then pass through an enzyme called ATP synthase, which uses the energy stored in the proton gradient to synthesize ATP from ADP and Pi
proton gradient
a difference in proton concentration across the thylakoid membrane
ATP synthase
a transmembrane protein that provides a channel for protons to move down their electrochemical gradient from the thylakoid space to stroma; as the protons move down the gradient, ATP synthase harnesses the kinetic energy of proton movement and uses it to synthesize ATP from ADP by phosphorylation
phosphorylation
the process in which a phosphate is added to a molecule
photophosphorylation
the process by which phosphorylation is powered by the energy of sunlight
Calvin cycle
series of enzymatic reactions that synthesize carbohydrates from carbon dioxide; uses ATP and NADPH produced in the light reactions to incorporate carbon dioxide into carbohydrates
fixation
1st step of the Calvin cycle; process where carbon dioxide (CO2) is added to a 5 carbon sugar to make a 6 carbon molecule
reduction
2nd step of the Calvin cycle in which energy inputs from ATP and NADPH lead to the synthesis of triose phosphate, which are carbohydrates
regeneration
third step of the Calvin cycle in which the 5-carbon sugar is regenerated from the 3-carbon triose phosphates; requires ATP
starch
a storage form of carbohydrates that does not lead to osmosis
rubisco
catalyzes the first set of reactions in the Calvin cycle; uses CO2 as a substrate and adds it to a 5-carbon molecule in a process called carbon fixation
photorespiration
occurs when rubisco uses oxygen rather than carbon dioxide as a substrate; ATP is consumes and carbon dioxide is produced
free energy
energy available to do work
redox reactions
reactions involving electron transfers; oxidation-reduction reactions
cellular respiration
in cellular respiration, glucose is oxidized to carbon dioxide, and at the same time, oxygen is reduced to water; main function is to synthesize ATP for use by the cell
ATP Production
two ways: 1 way is where an organic molecule transfers a phosphate group directly to ADP aka substrate-level phosphorylation; 2nd way is from oxidative phosphorylation
substrate-level phosphorylation
a way of generating ATP in which a phosphate group is transferred to ADP from an organic molecule, which acts as a phosphate donor or substrate; a single enzyme carries out two reactions: the hydrolysis of an organic molecule to produce a phosphate group, and the addition of that phosphate group to ADP creating ATP
oxidative phosphorylation
where most of the ATP in cellular respiration comes from; the process by which the chemical energy of organic molecules is transferred first to electron carriers and these electron carriers carry electrons (energy) from one set of reactions to another; electron carriers in cellular respiration are NADH and FADH2
process of oxidative phosphorylation
NAD+ and FAD accept electrons and energy, and are converted to their reduced forms NADH and FADH2. In their reduced forms, NADH and FADH2 transport electrons and energy to the respiratory electron transport chain
respiratory electron transport chain
a series of membrane-associated proteins in the inner membrane of mitochondria that transfers electrons to a final electron acceptor
oxidative phosphorylation (again)
A set of chemical reactions that occurs by passing electrons along an electron transport chain to a final electron acceptor, oxygen, pumping protons across a membrane, and using the proton electrochemical gradient to drive the synthesis of ATP
four stages of cellular respiration
glycolysis, pyruvate oxidation, krebs cycle, oxidative phosphorylation
glycolysis
the partial breakdown of glucose to pyruvate, producing ATP and reduced electron carriers by substrate-level phosphorylation; the first stage of cellular respiration; takes place in the cytoplasm; anaerobic process; begins with a 6-carbon molecule of glucose and produces two 3-carbon molecules of pyruvate and a net total of 2 molecules of ATP and 2 molecules of NADH (electron carrier)
pyruvate oxidation
the second stage of cellular respiration which takes place in the mitochondria in eukaryotes; process where pyruvate is oxidized to another molecule called acetyl-coenzyme A (acetyl CoA), producing reduced electron carriers and releasing carbon dioxide
Krebs cycle/Citric acid cycle
the 3rd stage of cellular respiration which takes place in the mitochondria in eukaryotes; process where the acetyl-CoA is completely oxidized to carbon dioxide, and free energy is transferred to ATP by substrate-level phosphorylation and reduced electron carriers
oxidative phosphorylation
the 4th stage of cellular respiration where reduced electron carriers generated in stages 1-3 donate electrons to the respiratory electron transport chain; generates a large amount of ATP
storage forms of glucose
stored in two major forms: glycogen in animals, and starch in plants
glycogen
a large, branched chain of glucose molecules attached to a central protein; storage form of glucose in animal cells
starch
a large branched chain of glucose molecules found in plants such as potatoes, wheat, and corn; storage form of glucose in plant cells
other fuel molecules
sugars other than glucose, fats such as triacylglycerol, and proteins are all fuel molecules that are broken down and enter the cellular respiration pathway at different places. Some enter glycolysis; others are converted to acetyl-CoA; and still others enter the Krebs cycle
respiratory electron transport chain
The respiratory electron transport chain consists of four complexes (I to IV) in the inner mitochondrial membrane. Electrons flow from electron carriers to oxygen, the final electron acceptor. The proton gradient formed from the electron transport chain has potential energy that is used to synthesize ATP
ATP synthase
protons move down their electrochemical gradient from high concentration to low concentration through a channel in ATP synthase, causing it to rotate and leading to the formation of ATP from ADP and Pi by means of an electrochemical proton gradient
chemiosmosis
the movement of ions, such as hydrogen ions (protons), from a region of high concentration to a region of low concentration across a selectively permeable membrane; chemiosmosis powers the synthesis of ATP by ATP synthase
fermentation
a process that extracts energy from fuel molecules without using oxygen or an electron transport chain; important for anaerobic organisms, sometimes used by aerobic organisms when oxygen cannot be delivered quickly enough
early atmosphere of earth
little to no oxygen gas so earliest organisms probably used fermentation pathways to generate ATP, environment was likely acidic
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