2_3 photosynthesis
Under what conditions does each type of photosynthetic plant thrive?
CAM plants do well in arid environments. C3 plants do better in cooler environments. C plants do well in areas with high light intensities, high temperatures and low rainfall
CAM plants
CAM stands for crassulacean-acid metabolism. a family of flowering succulent(water-containing) plants that live in warm, dry regions of the world. these plants open there stomata at night and store up as much carbon dioxide as possible. it uses PEP case to fix carbon dioxide and store as malic acid in large vacuoles of mesophyll cells. During the day the plant closes its stomata, breaks down the malic acid and releases the carbon dioxide to the Calvin cycle within mesophyll cells.
cyclic pathway
In cyclic electron flow, the electron begins in a pigment complex called photosystem I where it is charged. It then leaves the photosystem and is passed to the primary electron carrier to ferredoxin, then to cytochrome b6f (a similar complex to that found in mitochondria), and then to plastocyanin before returning to photosystem I. This transport chain produces a proton-motive force, pumping H+ ions across the membrane; this produces a concentration gradient that can be used to power ATP synthase during chemiosmosis. This pathway is known as cyclic photophosphorylation, and it produces neither O2 nor NADPH. Unlike the non-cyclic pathway, NADP+ does not accept the electrons; they are instead sent back to cytochrome b6f complex.
Where specifically does photosynthesis take place?
In the chloroplast of the palisade mesophyll cells.
photosystem
a photosynthetic unit comprised of a pigment complex and an electron acceptor; solar energy is absorbed & used to charge an electron.
*granum
a stack of thylakoids; grana is plural
what is the absorption spectrum for chlorophyll a & b?
chlorophyll a & b absorb violet-blue-red light range best and reflect/transmit green light.
*thylakoid
flattened disk-like sacs made from a third membrane within the chloroplast;
Which organisms are capable of photosynthesis?
plants, algae, and some bacteria
*chemiosmosis
the production of ATP due to a hydrogen ion electrochemical gradient across a membrane; ATP synthase complex pumps H+ flows from high to low concentration across the membrane. this movement down the concentration gradient provides the energy necessary to produce ATP from ADP and P.
chemiosmosis
the production of ATP due to the movement of hydrogen ions across a membrane according to its electrochemical gradient.
absorption spectrum
the specific wavelengths of light that a pigment absorbs
Where are the carriers of electron transport located in the mitochondria and the chloroplast?
They are located within membranes in each structure. In the mitochondria it is the cristae and for chloroplast it is the thylakoids;
How many G3P are needed to make glucose?
Two
What part of the electromagnetic spectrum is used for photosynthesis?
Visible light is primarily used
photosynthesis
chemical process that converts solar energy into chemical energy by using light to convert carbon dioxide and water into carbohydrates[such as glucose] & oxygen. In plants photosynthesis occurs in the chloroplast and happens in two phases; the light reactions and dark reactions (or Calvin Cycle).
cellular respiration
chemical process that produces energy by converting carbohydrates & oxygen into carbon dioxide, water & energy in the form of ATP. cellular respiration takes place in the mitochondria and has four or three phases.
True or False || In the photosynthesis Oxygen, O2, come from water not carbon dioxide.
TRUE
How does chemiosmosis happen in photosynthesis?
The ETC creates an electrochemical gradient of hydrogen ions on one side of the thylakoid membrane; These hydrogen ions will then flow through the ATP synthase complex across the membrane and ATP is formed;
How are the raw materials of photosynthesis acquired by plants?
carbon dioxide enters the leaf through small openings called stomata; the roots absorb water which then moves up vascular tissue up the stem to a leaf by way of the leaf veins. After entering the leaf carbon dioxide & water enter the chloroplast via diffusion.
C4 plants
plants that have adaptations that allow the plant to survive in hot & dry climate. this means that have mad adaptations to avoid photorespiration like C3 plants.
if the weather is hot and dry, what happens in a C3 plant?
the stomata closes to conserve water. This will cause the carbon dioxide concentration to decrease and the oxygen concentration to increase
what is the function and location of chlorophyll and the other pigments in the chloroplast?
they function to (1) absorb solar energy and (2) energize electrons prior to the reduction of CO2. Located on thylakoid membranes.
What are the parts of photosynthesis? briefly explain each?
(1) LIGHT DEPENDENT REACTION: Light(solar energy) is absorbed via pigment molecules chlorophyll A (which absorbs solar energy of wavelength 665nm) and chlorophyll B (absorbs solar energy of wavelength 640nm). This energy is then used to make ATP, NADPH, and Oxygen Gas via the ETC. (2)LIGHT INDEPENDENT REACTIONS: Carbon dioxide is converted into G3P via the Calvin Cycle (for C3 plants) and then eventually into glucose and other sugars after two turns. The whole purpose of dark reactions is to make G3P from the ATP and NADPH made during the light dependent reactions.
What two parts does photosynthesis have?
(1) light reactions (2) dark (or Calvin cycle) reactions
In photosynthesis Carbon dioxide is________ to produce glucose. While glucose is ____________ to produce ATP during cellular respiration.
(1) reduced (2) oxidized
Compare and contrast C3 & C4 plants.
(1)In C3 plants, only the mesophyll cells contain chloroplast. In C4 plants, both the mesophyll and bundle sheath cells contain chloroplast. (2) In C3 plants, mesophyll cells are arranged in parallel layers while the mesophyll cells are arranged concentrically around the bundle sheath cells in C4 plants. (3) C3 plants use Rubisco to fix carbon dioxide. It makes three carbon PGA. C4 plants use PEP carboxylase (PEPCase) to fix carbon dioxide. The carbon dioxide is fixed to PEP (phosphoenolpyruvate) and this results in the production of a 4 carbon molecule called oxolacetate. (4) In C3 plants, carbon dioxide is taken up and enters the Calvin cycle in mesophyll cells. In C4 plants, carbon dioxide is taken up in mesophyll cells but enters the Calvin cycle after being pumped into the bundle sheath cells as oxolacetate (or in a reduced form called malate). (5) In hot dry climates, the photosynthetic rate of C4 plants(like corn) is 2-3 times higher than C3 plants. (6) in these climates photorespiration does not happen because PEPCase, unlike rubisco. (7) even when the stomatas are closed, carbon dioxide is still delivered to the bundle sheath cells of C4 plants. (8) when the weather is moderate C3 plants have the photosynthetic advantage over C4 plants. when it is hot and dry, vice versa.
NADP+
(Nicotineamide adenine dinucleotide phosphate) a coenzyme that accepts electrons and hydrogen ions derived from water during photosynthesis; since NADP+ gains electrons it undergoes reduction and is the oxidizing agent. Later this molecule( in the form of NADPH) will pass its electron and hydrogen ion to carbon dioxide which will form the high energy molecule glucose. NADP+ is often referred to as an electron carrier.
NAD+
(nicotine adenine dinucleotide) is a coenzyme molecule that accepts(or removes) electrons and hydrogen ions from the glucose during cellular respiration(unlike NADP+ in photosynthesis, each NAD+ excepts 2 electrons and 1 hydrogen ion each time);. Since it accepts electrons it undergoes reduction and is an oxidizing agent;
During photosynthesis what happens to water?
During the light reactions, electrons from water are removed and charged by photosytem 2 when the photosytem cleaves[splits || or breaks down] water splitting it into hydrogen ions(H+) ions & oxygen. Eventually the electrons & hydrogen ions will be transferred to carbon dioxide to form glucose.
What happens to the other portions of the electromagnetic spectrum not used in photosynthesis?
Energy with wavelengths higher than visible light are screened out by the ozone layer and lower energy wavelengths are screened out by carbon dioxide and water vapor before they reach the earth's surface.
What happens to H+ ions during the ETC?
H+ ions or protons collect on one side of the membrane. This creates an electrochemical gradient across the membrane.
How is oxidation-reduction involved in photosynthesis?
In photosynthesis, carbon dioxide undergoes reduction & water undergoes oxidation. It takes hydrogen atoms, electrons and energy to reduce the carbon dioxide. For this process solar energy is not directly used as the source of energy. It is converted to ATP and then ATP provides the requisite energy. the electrons needed to reduce carbon dioxide are carried by the coenzyme NADP+ but originate from the splitting of water
photorespiration
It is a process where a plant fixes oxygen gas to ribulose bisphosphate(RuBp) instead of carbon dioxide; photorespiration results in the eventual release of carbon dioxide and the production of only one PGA molecule instead of two. this process is not what a plant wants to do and happens when the weather is hot & dry.
Explain what happens to grass in terms of C3 vs C4 plants.
Kentucky bluegrass (C3) dominates lawns early in summer where crabgrass (C4) takes over in the hot midsummer.
electron transport chain
a series of membrane bound carrier proteins that will pass electrons from one carrier to another. each time an electron is passed on to the next to carrier protein, energy is released and used to pump a hydrogen ion into the thylakoids space. a gradient of hydrogen ions is created and will later be used by ATP synthatase complex to produce ATP in the stroma; ATP synthesis is coupled to the ETC;high energy electrons are delivered to the chain and low energy energy electrons leave it
spectrophotometer
an instrument that measures the amount of light that passes through a sample.
Compare and contrast autotrophs and heterotrophs.
autotrophs and heterotrophs differ in that autotrophs are organisms that produce their own food, while heterotrophs do not. Heterotrophs (also called consumers) must intake pre-formed organic molecules for nourishment. They are similar in that both use organic molecules produced by photosynthesis as a source of building blocks for growth, repair, and energy.
why do leaves turn yellow-orange in the fall?
because the chlorophyll pigments breakdown and the yellow-orange pigments show through
How does chemiosmosis happen in cellular respiration?
glucose breakdown provides energy for an electrochemical gradient of hydrogen ions to build up on one side of the inner mitochondrial membrane. These hydrogen ions will then flow through the ATP synthase complex across the membrane and ATP is formed;
photosynthesis take place mostly in_____________________.
in the chloroplast located in palisade mesophyll cells.
what structures are necessary for light reactions to take place?
light gathering units Photosystems I & II.
*chloroplast
membranous organelle that serves as the site of photosynthesis; chloroplast is bound by a double membrane; within the chloroplast are stacks of thylakoids( or granum) suspended in a semifluid(stroma) containing enzymes and other organic substances necessary for photosynthesis; they have their own DNA and ribosomes(which proof that the endosymbiotic theory is true;
what is the absorption spectrum for carotenoids?
pigment molecule carotenoid absorbs violet-blue-green range and reflect/transmit yellow and orange.
how do pigments work?
pigments absorb specific wavelengths of light and reflect/transmit others. the wavelength(s) that are reflected by the pigment is/are the color the pigment appears. For example, both chlorophyll a & b absorb violet, blue, and red, but reflect/transmit green which is why plant leaves appear green.
In general terms, describe light reactions.
reactions that take place only in the presence of light(solar energy); (1) chlorophyll within thylakoid membranes absorb solar energy and energize electrons obtained from the splitting of water. the splitting of water also results in the release of oxygen (2) the electrons move down an electron transport chain. as the electrons move down the ETC energy is released and captured for the production of ATP molecules. (3) the energized electrons are also taken up by NADP+ which becomes NADPH.
**thylakoid space
semifluid mixture inside the thylakoids; all thylakoids are connected together and form an inner compartment. This compartment is called the thylakoid space
*stroma
semifluid mixture within the chloroplast where thylakoids are suspended. it contains enzymes and pigments(which absorb solar energy) necessary for photosynthesis.
stomata
small openings through which water can leave and carbon dioxide can enter;
ATP synthase complexes
the enzymes and proteins that span the membrane of the ETC. Each complex contains a channel that allows hydrogen ions to flow down their electrochemical gradient; the flow of electrons through this channel protein produces ATP from ADP and a phosphate group.
reduction
the gain of electrons;
oxidation
the loss of electrons;
C3 plants
the majority of land plants that carry out normal photosynthesis where carbon dioxide gets fixed directly and the first molecule following carbon dioxide fixation is PGA.
In general terms, describe dark reactions or Calvin cycle reactions.
the reactions of photosynthesis that take place in the stroma and can happen in either the presence or absence of light. In the Calvin cycle reactions carbon dioxide is absorbed and gets reduced to a carbohydrate (that can later be converted into glucose) by utilizing the ATP and NADPH produced during the light reactions.
photolysis
the splitting of water which produces oxygen gas and hydrogen ions. this process is commonly used by photosystems II to get replenish its supply of electrons electrons?
non-cyclic pathway
this is the pathway that electrons usually follow in light reactions; the non-cyclic pathway begins with photosystem II. (1) this pigment complex(photosystem II) absorbs solar energy and charges an electron located in the reaction center(a pair of chlorophyll a molecules). (2) the highly charged electron leaves the reaction center and moves through the Electron Transport Chain via a series of electron carriers. Photosystem II replaces the electron it just lost by splitting water (splitting water results in oxygen gas and hydrogen ions. the oxygen gas gets released while the hydrogen ions remain in the thylakoid space) (3) In the ETC, the electron moves from one carrier to another. Each time the electron is transferred to a new carrier, energy is used to move protons in the stroma (not the ones already inside the inner compartment of thylakoids) to the thylakoid space. This adds to the already developing electrochemical gradient of H+ ions. (4) the ATP synthase complex will use this proton gradient to make ATP and pump the H+ ions across the thylakoid membrane into the stroma(this is called chemiosmosis). (5) the low-energy electron leaves the ETC and is delivered to photosystem I. (6) Photosystem I absorb solar energy and recharges the electron. (7) the recharged electron is then passed to electron carrier NADP+. NADP+ then waits for another electron and combines with an H+ ion to form NADPH which will be used(along with ATP) in the dark reactions.
How exactly does coenzyme NADP+ "carry" electrons?
when water splits during photosynthesis, NADP+ takes up the electrons and hydrogen while the oxygen is released. Since NADP+ accepted the electrons we say that it was reduced (or underwent reduction reaction) forming NADPH. Later in its NADPH form, it will give up its electrons and hydrogen to carbon dioxide(thus reducing the carbon dioxide to form carbohydrates). when it gives it electrons to carbon dioxide NADPH is undergoes oxidation(or we say is oxidized) because it is losing electrons to carbon dioxide.
What is the alternative description for the function of NADP+ as an electron carrier?
when water splits during photosynthesis, we say that NADP+ oxidized water or that NADP+ is the oxidizing agent. As for NADPH, we say that it reduced carbon dioxide or it is the reducing agent.
