BIO 12: Photosynthesis

3 processes that moves water from soil to leaves. Explain each

1. Root uptake force- when water moving into the roots has a "force" which helps drive the water up the xylem 2. Transpiration - when the loss of water from the stomata of leaves creates a suction to help draw water upward 3. Adhesion/Cohesion Adhesion- refers to the attraction of dissolved minerals in the water Cohesion- refers to the ability of water to stick together and rise up in narrow tubes due to its polarity

what can happen when an electron gets excited?

Once excited, an electron can either... 1. Return to its ground state emitting energy as thermal energy or fluorescence 2. Transfer its energy to an electron in a neighbouring pigment molecule, causing it to be excited 3. Be transferred to a nearby electron accepting molecule (aka. Primary electron acceptor)

explain how the stomata and guard cells work together to allow gas exchange

first, K+ is moved into the guard cell by active transport in the presence of sunlight. this creates a hypotonic solution, causing water to move into the guard cell. As guard cells begin to swell up, the stoma "pops" open which allows CO2/O2 exchange to occur through this opening

HOMEWORK QUESTIONS: Why does PEP carboxylase do a better job than rubisco at fixing CO2 in plants that use the C4 pathway? In what type of environment is PEP carboxylase more effective than rubisco?

this is b/c PEP carboxylase doesn't have an attraction for O2 like rubisco does. Thus, it can prevent the loss of efficiency due to photorespiration when using rubisco. PEP carboxylase works better than rubisco in oxygen-rich environments

HOMEWORK QUESTIONS: What are the thylakoids? Why are they important for photosynthesis?

thylakoids are flat & closed sacs found inside chloroplasts that contain pigments & other molecules that help light-dependent rxns of photosynthesis take place. they're important for photosynthesis b/c the thylakoids is where light energy is absorbed to start photosynthesis

list the 3 types of leaf pigments. Explain each

1. Carotenoids- reflect red and yellow wavelengths and appear orange, 2. Xanthophylls - reflect yellow light 3. Anthocyanins - reflect red wavelengths.

1. what are chloroplast structures? 2. explain the components of the chloroplast structure

1. Chloroplasts are rounded organelles that're responsible for photosynthesis 2. it contain 3 membranes. The outer membrane covers the entire surface while a second inner membrane is found inside the outer one. The aqueous interior is called the stroma and contains the enzymes for the Calvin Cycle. In the stroma, the third membrane called the thylakoid membrane surround the stacks of flattened discs known as grena. The space inside a thylakoid is called the lumen

explain the steps of light-dependent reactions

1. O2 and the protons are released into the Lumen while the electrons are passed to the electron transport chain. When light strikes the antenna complex, the reaction centre (P680) which also contains chlorophyll a, becomes energized, causing the P680 and an electron to be passed to the primary acceptor molecule & forming P680+ which has a high electroneg. and removes an electron from water. (P680+ is the strongest oxidant known in Biology) 2. water splitting complexes oxidizes water by passing an electron to P680+ which becomes neutral while the primary acceptor molecule passes an electron to plastoquinone. Plastoquinone moves the electrons between photosystem II and the cytochrome complex, while allowing a proton to be moved from the stroma & into the lumen 3.The electrons are then sent from the cytochrome c to the photosystem I using plastocyanin. When light strikes P700, the rxn centre becomes energized, causing P700 and an electron to be passed to the primary electron acceptor molecule. This forms P700+ which then is reduced back to P700 by the oxidation of plastocyanin 4.The electron is then transferred to ferredoxin which then transfers an electrons to NADP+ , and reduces it to NADP.A second electron from ferredoxin is transferred to NADP and a proton from the stroma with NADP+ REDUCTASE forms NADPH 5.A concentration gradient allows H+ to use proton motive forces to drive chemiosmosis (caused by a higher H+ concent. In the lumen due to splitting of water, the transport of H+ by plastoquinone from the stroma into the lumen and the decrease in H+ in the stroma when a NADPH forms) is used to create ATP, as the kinetic energy of the H+ moving through ATP synthase allows ADP + Pi----> ATP. Thus, solar energy is trapped in ATP and NADPH

2 types of autotrophs and explain each

1. Prokaryotic cells - have no internal organelles or membranes. Thus, reactions occur in the cytosol and on the folds in cell membrane (ex. cyanobacteria) 2. Eukaryotic Cells - have internal organelles, thus chloroplasts are where rxns occur; the leaves are the primary site for photosynthesis.

1. what is a stomata? 2.what is a guard cell?

1. an opening or pore in a plants epidermis, that allows co2 to enter and O2 to leave 2. cell that can open the stomata to take in or release oxygen, carbon dioxide and water,

HOMEWORK QUESTIONS: 1. in what organelles do light and dark reactions occur in? 2. compare the structure of mitochondria vs chloroplasts

1. inside the chloroplasts 2. MITOCHONDRIA- has up to 1000 per cell, has a diameter of 0.5-1 micrometer, & produces energy from food CHLOROPLASTS- has 20-50 per cell & has a length of 5-10 micrometers & reduces food from energy & carbon compounds

HOMEWORK QUESTIONS: 1. why are dark rxns referred to dark reactions? 2. what is used to build carbohydrates molecules from carbon dioxide? 3. how are carbohydrates(sugar) used in plant cells?

1. they're referred to dark rxns because they don't require light energy to produce energy 2.ATP & NADPH builds carbohydrates molecules from CO2 3. carbohydrates can be used for fuel or can become glucose, cellulose,starch and sucrose

3 phases of the Calvin cycle and explain each

1.Carbon Fixation - RuBP takes CO2 from the air to form two molecules of 3-phosphoglycerate. 2.Reduction reaction- the 3-phosphoglycerate gains a Pi as ATP→ ADP. It is then reduced by the electrons from NADPH to form glyceraldehyde 3-phosphate. 3.Regeneration of RuBP- One of the glyceraldehyde 3-phosphates leaves the reactions, and the other 5 molecules of glyceraldehyde 3-phosphate are rearranged into RuBP again. The G3P that leaves the reaction combines with another G3P to make glucose. Thus, the Calvin Cycle must occur twice to make one sugar

factors affecting photosynthesis

1.Light 2.Carbon Dioxide 3.Tempurature 4.Colour of Light

3 reasons why is photosynthesis important

1.plants and bacteria use the sun to produce their own fuel & biosynthetic molecules 2.all energy used to sustain life comes from the sun and it starts off with the process of photosynthesis 3.animals depend on photosynthesis of plants to release O2, while animals release CO2 to plants for photosynthesis

state equation for photosynthesis

6 H2O + 6O2 --> C6H12O6 + 6O2 + 18 ATP + 12 NADPH

explain what autotrophs and heterotrophs are

Autotrophs are organisms that can produce their own food from the substances available in their surroundings. Example is a plant b/c it uses photosynthesis to create energy. Heterotrophs are organisms that cannot make their own food and rely/consume other organisms for energy. ex. animals or humans

what are C3 plants? state environment its found in and give examples

C3 plants are plants that undergo normal photosynthesis (also called C3 metabolism) with the presence of light-dependent rxn and Calvin cycle. It does so with the production of a 3c sugar (3-phosphoglycerate). ENVIRON: cool, wet climates. ex. beans, rice, wheat, potatoes

HOMEWORK QUESTIONS: compare and contrast oxidative phosphorylation & photosynthesis

COMPARE: they both have the electron transport chain CONTRAST: 1. Photophosphorylation occurs during photosynthesis and oxidative phosphorylation during cellular respiration. 2. they're are the reverse of each other. In photosynthesis we use water & electrons to produce NADPH while oxidative phosphorylation requires NADH to produce water and energy.

explain the absorption spectrum of Chlorophyll a and Chlorophyll b.

Chloroplast structure become unstable at low temp. and break apart. This means no new chlorophyll can be made. This leads to other pigments being revealed. These accessory pigments become visible allowing fall foliage to exhibit yellow,orange and red colours.

what are the fates/pathways of Glyceraldehyde 3-phosphate?

It can become... 1. Glucose that enters cellular respiration 2. Starch stored in roots and stems 3. Cellulose used in cell walls 4. Sucrose which is sent to other parts of the plant to circulate from cell to cell or may be used for storage

whats the difference between noncyclic phosphorylation and cyclic phosphorylation?

Noncyclic Phosphorylation 2e → P680 → P.Q → cytochrome complex → P.C → P700 → Fd → NADP+ reductase BUT IN CYCLIC PHOSPHORYLATION... ferredoxin donates electrons back to plastoquinone (instead of NADP+ reductase) which makes more H+ into the lumen. This process plays an important role in overall photosynthesis, since it allows more production of ATP due to high conc. Of H+ in lumen vs low conc. Outside cell, so H+ passes through ATP synthase to make more ATP for the Calvin Cycle to occur

EXPLAIN THE FOLLOWING FACTOR THAT AFFECTS PHOTOSYNTHESIS: colour of light

Plants reflect green wavelengths. Thus, the rate of photosynthesis slows with green light while high rate of photosynthesis is achieved using red,blue and violet wavelengths of light

what are CAM plants? State the environ. it is found in & give examples

Plants that use the Calvin Cycle and the C4 cycles at different times of the day. The Stomata opens at night to release O2 & allows CO2 to enter by the C4 pathway, into malate and then is stored in vacuoles. As tempuratures increase during the day, the stoma closes to reduce water loss which stops gas exchange Malate turns into pyruvate & releases CO2 for the Calvin cycle. This pyruvate is then converted back into malate at night using ATP as the stoma opens. Opening stoma at night prevents dehydration & provides CO2 during the day. ENVIRON: Occurs in places with hot,dry days and cool nights ex. cacti, pineapples, succulent plants

How can using rubisco become a problem?

The active site of rubisco can also bind with oxygen due to oxygen's high concentration. This leads to Photorespiration. Photorespiration is the process that reduces the products of photosynthesis, because the active site of rubisco accepts O2 in place of CO2 and generates no ATP. This occurs at higher temps since the solubility of CO2 decreases faster than the solubility of O2. Thus, in hot climates a plant may waste 50% of energy on photorespiration.

HOMEWORK QUESTIONS: Analysis of a plant's leaf showed an unusually high amount of ATP, but relatively little NADPH. Which electron transport method is probably working much more predominantly in this leaf? Which photosystem is probably absorbing more light energy? Explain your answer

The cyclic phosphorylation is worker harder in a leaf B/C of the high ATP and low NADPH compared to the ETC. This makes sense b/c cyclic phosphorylation creates ATP but not NADPH. Photosystem I is absorbing more light than Photosystem II since cyclic acid cycle occurs in Photosystem I.

HOMEWORK QUESTIONS: Diuron (DCMU) is a herbicide that is no longer registered for use in Canada. It is a photosystem II inhibitor. What does this mean for a plant?

This means that since DCMU is a photosystem II inhibitor, it prevents electrons from being transferred from P.S II through plastoquinone & the ETC. Since the non-cyclic ETC is blocked, it means that the DCMU is stopping photosynthesis. Thus it kills the plant

what are the 2 structures that helps water move to the leaves and to remove the sugars (sap) from the leaves? Explain each

Xylem - is made of vessel elements and tracheids (VET) and have cytoplasm when mature. There are holes/pits in the cell walls and an end-on-end orientation as the end walls dissolve at death. The xylem forms a continuous non-living duct for the movement of water and minerals upward in the stem. Phloem- made of sieve tubes and companion cells which forms a tube. The phloem transports sugar from the production source (leaves) to the storage site (roots,stem or fruit). The cells are alive but the sieve tube cells lose a nucleus when mature. The cells have holes on cell walls which form sieve plates.

HOMEWORK QUESTIONS: Heterotrophs need autotrophs to survive, but do autotrophs need heterotrophs to survive? Explain and justify your answer.

Yes, autotrophs need heterotrophs to survive. This is b/c when autotrophs die, their carbon will be trapped in dirt, soil etc. Thus autotrophs need heterotrophs to decompose and recycle the carbon needed for photosynthesis

HOMEWORK QUESTIONS: Would a green plant grow better under a green light or a red light? Explain your answer.

a green plant would grow better under red light b/c since the plant is green, it means that it will reflect light that is green while absorbing other light colours (red, purple etc). Thus, since it reflects green light, it can't obtain the energy in the light for photosynthesis. Thus, red light is more effective

HOMEWORK QUESTIONS: Which type of plant (C3, C4, or CAM) would you expect to grow most e ciently in each environment? Explain your reasoning. (a) a hot, wet tropical environment (b) an environment with extremely hot days but cool nights (c) a cool, damp environment (d) an environment with a moderate climate but nutrient-poor soil

a) C4 plants will grow more effectively in hot, wet, tropical environ. b/c since its in a wet environ. it means it doesn't need to conserve water b) CAM plants will grow effectively in extremely hot days but cool nights b/c CAM plants are adapted to conserving water during the day with the help of its stomata opening at night c) C3 plants will grow better in cool, damp environment b/c since photorespiration & water loss isn't a problem for C3 plants, it can then live in this enviro. to save ATP d) C4 plants will grow better in moderate climate but nutrient-poor soil b/c since C4 plants use less rubisco it means it doesn't require a lot of nitrogen from the soil.

HOMEWORK QUESTIONS: Scientists routinely create knockout organisms to determine the function of a gene. Suppose that a plant has the gene responsible for NADP+ reductase enzyme "knocked out." What effect would this have on the cells of the plant, in terms of their ability to perform each of the following processes? (a) non-cyclic ATP synthesis (b) cyclic ATP synthesis (c) Calvin cycle

a) The knocking out of genes for NADP+ will be a neg. effect for non-cyclic ATP synthesis b/c the non-cyclic ATP will stop due to zero electrons being donated from ferredoxin to NADP+ using the NADP+ reductase. This forces the plant to only go through cyclic ATP synthesis b) This will be a positive effect on cyclic ATP synthesis b/c electrons from ferredoxin can now only travel to plastoquinone, causing H+ to move across the cell w/o photosystem II. This allows only ATP to be produced c) this will be a neg. effect cuz Calvin cycle will shut down

HOMEWORK QUESTIONS: a) when light energy is absorbed by photosynthetic pigments, what des the light excite? b)what happens after the excitation? c)is there any light or heat given off? d)is this a productive process?

a) The lights will excite an electron b) after the electron gets excited, the electron will move to a higher energy level c) yes it will release light and heat as it moves to higher energy level d)no this is not a productive process since it loses its energized state by releasing light & heat

HOMEWORK QUESTIONS: a) once an electron from chlorophyll a is excited, what molecule grabs the electron? b) once the electron leaves chlorophyll a, is chlorophyll a reduced or oxidized

a) the primary acceptor molecule grabs it b) chlorophyll a gets oxidized since it loses the electron while the primary acceptor molecule gets reduced since it gained an electron

HOMEWORK QUESTIONS: a) what are the 2 rxns in photosynthesis? b) how are ATP & NADPH formed? c) what does light rxns use to move the excited electrons around? d) what process is this the reverse of?

a) the two rxns are light-dependent reactions and light-independent reactions (Calvin cycle/dark rxn) b)ATP and NADPH are formed with the movement of electrons in the light rxns. c) light rxns use the electron transport chain/ photosystem due to its electronegativity d) this is the reverse of oxidative phosphorylation

what is rubisco?

an enzyme present in the Calvin cycle that is responsible for joining RuBP and CO2. It's the most abundant protein on earth since it makes up 50% of protein mass in a leaf. Its function is to help CO2 combine with RuBP but its active site can also bind it to oxygen since oxygen has a higher concentration in the atmosphere. thus, this creates problem

HOMEWORK QUESTIONS: Rubisco is the world's most abundant protein, yet it is not found inside any animal cells. Suggest a reason why animals do not need or use this protein.

animals don't use rubisco b/c since animals already obtain oxygen & energy by consuming organisms, they don't need rubisco to obtain more oxygen. Rubisco is mainly used for photosynthesis in plants. Thus since animals don't require photosynthesis, we don't need rubisco

what are plasmodesmata?

are located in the phloem & connect sieve tube cells to companion cells, and control the action of the sieve tube cells.

what is chlorophyll?

is a pigment in plants capable of trapping solar energy. There are 2 main types (chlorophyll a & b) and appear green since it absorbs all colours but reflects green wavelengths. Thus, since it reflects green light, it means that green light isn't really helpful for plant growth. When temperatures become cold, chlorophyll degrades and other pigments become visible that reflect colours other than green.

explain the process of how plants capture light energy

it starts off with pigment molecules absorbing photons of light energy. This excites electrons from its ground state (orig.energy level) to its excited state (higher energy level). The difference in energy between the ground and excited states must equal the energy of the photon absorbed, or else the photon cannot be absorbed.

HOMEWORK QUESTIONS: Why is light energy essential for photosynthesis to occur?

light energy is essential b/c electrons need a boost of energy from light/photons during photosystem II and I and allowing electron transport to occur.

HOMEWORK QUESTIONS: Do the light-dependent reactions and the Calvin cycle occur in the same part of the chloroplasts? Explain your answer.

no, they don't occur at the same part of the chloroplast. The light-dependent rxn occurs in the thylakoid membrane & the Calvin cycle occurs in the stroma

HOMEWORK QUESTIONS: Chlorophyll a is the only pigment that contributes electrons directly to the primary electron acceptor. Knowing this, explain why plants have evolved to contain chlorophyll b and the accessory pigments.

plants evolved to contain chlorophyll b & accessory pigments in order to increase the plants ability to absorb many/more types of wavelengths that chlorophyll a cannot.

what are C4 plants? State the environ. it is found in & give examples

plants that occur in hot, dry climates & have diff. internal leaf structure. In these plants, CO2 combines with a 3c molecule phosphoenolpyruvate (PEP) to form a 4c molecule called malate. Malate is then oxidized into pyruvate releasing CO2 that can then enter in Calvin Cycle. Each turn of the C4 cycle requires ATP to remake phosphoenolpyruvate from pyruvate. This ATP can be made easily due to lots of sunlight. ENVIRON: Since stoma doesn't open as often, these plants can survive the hot climate ex. corn, sugar cane

HOMEWORK QUESTIONS: Why and how do protons move through the thylakoid membrane from the lumen to the stroma?

protons (H+) move through the thylakoid membrane from the lumen to the stroma b/c theres a high conc. of H+ in the lumen than outside. this causes the H+ to move to an area of high conc. to low conc. using ATP synthase.

EXPLAIN THE FOLLOWING FACTOR THAT AFFECTS PHOTOSYNTHESIS: temperature

rate of photosynthesis can only occur over a range of temperature; above this range causes enzyme (rubisco) denatures & below this range causes it to work slower

EXPLAIN THE FOLLOWING FACTOR THAT AFFECTS PHOTOSYNTHESIS: carbon dioxide

rate of photosynthesis increases as the concentration of CO2 increases up to a point and then plateaus as the Calvin cycle reaches a max rate for fixing carbon

EXPLAIN THE FOLLOWING FACTOR THAT AFFECTS PHOTOSYNTHESIS: light

rate of photosynthesis increases with light intensity up to a point and then plateaus (reaches a state of little or no change) as the light-dependent reactions reaches a max. rate

what is a photosystem?

structure in plants where chlorophyll absorbs light energy for photosynthesis. There are two types ( photosystems I and II ) and both contain 250-400 pigment molecule/proteins and antenna complexes at the reaction centre. In the reaction centre the proteins bound to chlorophyll a and the primary acceptor molecule. Light energy absorbed by the antenna complex is transferred to chlorophyll a in the reaction centre which donates an electron to the primary electron acceptor which then, passes the electron to the electron transport chain.

HOMEWORK QUESTIONS: The lowland areas of the Galapagos Islands are very arid and thus are home to many cacti and other succulent species of plants. The highlands of the Galapagos, in contrast, are cool and moist. ey are covered in thick, green vegetation, with few succulents. Use your understanding of photorespiration to account for this pattern of plant distribution

the environ. of lowland areas of Galapagos is a plc for CAM plant. Thats why theres more cacti & succulents; (hot @ day, cool @ night) which are plants that open their stomata to release O2 & absorb CO2 at night. The highlands are cool & moist so C3 plants can grow w/o water loss & allows them to open their stomata & allow gas exchange for photorespiration

HOMEWORK QUESTIONS: What drives the electron transport chain in photosystem I and photosystem II?

the photons drive electrons transport chain by exciting the electrons in P680 and P700

what is photosynthesis?

the process in which light energy (sun) is converted to chemical energy used to assemble organic molecules

what are light-dependent reactions?

the process of creating energy using the reaction of splitting water into 2H+ + 2e + ½ O2. It occurs in the photosystem II and uses light energy.

what is the Calvin cycle?

the process of creating energy without the use of light. It uses ATP and NADP to produce high energy sugars from carbon dioxide, and occurs in the stroma

HOMEWORK QUESTIONS: Explain the significance of the products of the light reactions of photosynthesis, in relation to the Calvin cycle.

the significance is that light rxns can produce oxygen, ATP and NADPH. The Calvin cycle then uses the ATP, NADPH & CO2 to make sugar

HOMEWORK QUESTIONS: do photons that have longer wavelengths contain a lot of energy or little energy?

they contain little energy