Biology1-2 Mrs. Hennings

 The Sun is the ultimate source of energy.  Photosynthesis is the process in which plants capture light energy and change it into chemical energy.  Organisms are classified to how the obtain energy.

 Autotrophic organisms- “self feeders” make their own food. Producers of ecosystems Photoautotroph Chemoautotroph  Heterotrophic organisms- can’t make their own food. They live on compounds made by other living organisms. Consumers of ecosystems. That is really important !

 Organisms are endergonic systems  What do we need energy for? synthesis building biomolecules reproduction movement active transport temperature regulation

 Work of life is done by energy coupling  use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions ++ energy + + digestion synthesis

ATP  Fueling the body’s economy  eat high energy organic molecules food = carbohydrates, lipids, proteins, nucleic acids  break them down digest = catabolism  capture released energy in a form the cell can use  Need an energy currency  a way to pass energy around  need a short term energy storage molecule Whoa! Hot stuff!

high energy bonds How efficient! Build once, use many ways  Adenosine TriPhosphate  modified nucleotide nucleotide = adenine + ribose + P i  AMP AMP + P i  ADP ADP + P i  ATP  adding phosphates is endergonic

P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O  Each negative PO 4 more difficult to add  a lot of stored energy in each bond most energy stored in 3rd P i 3rd P i is hardest group to keep bonded to molecule  Bonding of negative P i groups is unstable  spring-loaded  P i groups “pop” off easily & release energy Instability of its P bonds makes ATP an excellent energy donor I think he’s a bit unstable… don’t you? AMP ADPATP

P O–O– O–O– O –O–O P O–O– O–O– O –O–O P O–O– O–O– O –O–O 7.3 energy + P O–O– O–O– O –O–O  ATP  ADP  releases energy ∆G = -7.3 kcal/mole  Fuel other reactions  Phosphorylation  released P i can transfer to other molecules destabilizing the other molecules  enzyme that phosphorylates = “kinase” ADPATP

It’s never that simple!  Building polymers from monomers  need to destabilize the monomers  phosphorylate! C H OH H HOHO C C H O H C + H2OH2O kcal/mol C H OH C H P + ATP + ADP H HOHO C + C H O H CC H P + PiPi “kinase” enzyme -7.3 kcal/mol -3.1 kcal/mol enzyme H OH C H HOHO C synthesis

Can’t store ATP  good energy donor, not good energy storage too reactive transfers P i too easily only short term energy storage  carbohydrates & fats are long term energy storage A working muscle recycles over 10 million ATPs per second Whoa! Pass me the glucose (and O 2 )! ATP ADP PiPi kcal/mole cellular respiration

Think about how the structure of this organelle determines its function!

 Organelles in plants.  All green parts of plants have chloroplasts  Leaves is the major place where photosynthesis happens.  Contains chlorophyll- a green pigment that is used to absorb light energy and drive photosynthesis.  Mainly in spongy mesophyll cells- also in palisade mesophyll cells.  1.5 million chloroplasts per 1 sq meter of leaf surface.

Chloroplasts in Elodea leaves!

It has a phospholipid bilayer membrane around the thylakoid!

Where does it come from? How does it get into plants? What is it used for? Where does it come from? How does it get into plants? What is it used for? What provided the building blocks to make it? How is it made? What is it used for? Where does it go? Where does it come from? How does it get out of plants? What is it used for?

 Light Dependent: Light Reactions: Change solar energy into chemical energy. Happens in the thylakoid membrane.  Light Independent: Calvin Cycle: Takes carbon dioxide from air and “fixes” into Calvin cycle. Changes carbon dioxide into sugar. Happens in the stroma.

 The spectrum of color ROYGBIV

 When light comes into contact with matter it can be:  Reflected  Transmitted  Absorbed- substances that absorb light are called pigments. Different pigments absorb different wavelengths of light.

 Photosynthesis gets energy by absorbing wavelengths of light  chlorophyll a absorbs best in red & blue wavelengths & least in green  other pigments with different structures absorb light of different wavelengths Why are plants green?

O2O2 H2OH2O Energy Building Reactions ATP  produces ATP  produces NADPH  releases O 2 as a waste product sunlight H2OH2O ATP O2O2 light energy  +++ NADPH

ETC of Photosynthesis  Chloroplasts transform light energy into chemical energy of ATP  use electron carrier NADP +

 ETC produces from light energy  ATP & NADPH go to Calvin cycle  PS II absorbs light  excited electron passes from chlorophyll to “primary electron acceptor”  need to replace electron in chlorophyll  enzyme extracts electrons from H 2 O & supplies them to chlorophyll splits H 2 O O combines with another O to form O 2 O 2 released to atmosphere and we breathe easier!

PS II H20 e e e e e PS I NADP + O O H+ P ADP ATP H+ NADPH

 CO 2 has very little chemical energy  fully oxidized  C 6 H 12 O 6 contains a lot of chemical energy  reduced  endergonic  Reduction of CO 2  C 6 H 12 O 6 proceeds in many small uphill steps  each catalyzed by specific enzyme  using energy stored in ATP & NADPH

 Calvin cycle  chloroplast stroma  Need products of light reactions to drive synthesis reactions  ATP  NADPH

sugars C 6 H 12 O 6 CO 2 Sugar Building Reactions ADP  builds sugars  uses ATP & NADPH  recycles ADP & NADP back to make more ATP & NADPH ATP NADPH NADP CO 2 C 6 H 12 O 6  +++ NADPATP + NADPHADP

 Glyceraldehyde-3-P  end product of Calvin cycle  energy rich 3 carbon sugar  “C3 photosynthesis”  G-3-P = important intermediate  G-3-P   glucose   carbohydrates   lipids   amino acids   nucleic acids

 Light reactions  produced ATP  produced NADPH  consumed H 2 O  produced O 2 as byproduct  Calvin cycle  consumed CO 2  produced G3P (sugar)  regenerated ADP  regenerated NADP NADPADP

 Where did the CO 2 come from?  Where did the CO 2 go?  Where did the H 2 O come from?  Where did the H 2 O go?  Where did the energy come from?  What’s the energy used for?  What will the C 6 H 12 O 6 be used for?  Where did the O 2 come from?  Where will the O 2 go?  What else is involved…not listed in this equation? 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++

 Rate: activity per unit of time.  Photosynthesis can be measured by:  How much carbon dioxide is consumed.  How much oxygen is produced.  How much glucose is produced.  There are 3 main factors that affect the rate: Light intensity Temperature Concentrations of Carbon Dioxide and/or Oxygen

 Rubisco in Calvin cycle  carbon fixation enzyme normally bonds C to RuBP reduction of RuBP building sugars  when O 2 concentration is high Rubisco bonds O to RuBP O 2 is alternative substrate oxidation of RuBP breakdown sugars photosynthesis photorespiration

 Oxidation of RuBP  short circuit of Calvin cycle  loss of carbons to CO 2 can lose 50% of carbons fixed by Calvin cycle  reduces production of photosynthesis no ATP (energy) produced no C 6 H 12 O 6 (food) produced  if photorespiration could be reduced, plant would become 50% more efficient strong selection pressure to evolve alternative systems

 Separate carbon fixation from Calvin cycle  C4 plants physically separate carbon fixation from actual Calvin cycle different enzyme to capture CO 2 PEP carboxylase stores carbon in 4C compounds different leaf structure  CAM plants separate carbon fixation from actual Calvin cycle by time of day fix carbon (capture CO 2 ) during night store carbon in organic acids perform Calvin cycle during day

 A better way to capture CO 2  1st step before Calvin cycle, fix carbon with enzyme PEP carboxylase store as 4C compound  adaptation to hot, dry climates have to close stomates a lot different leaf anatomy  sugar cane, corn, other grasses…

 Separate reactions in different cells  light reactions  carbon fixation  Calvin cycle C3C4

CO 2 O2O2 O2O2  Outer cells  light reaction & carbon fixation  pumps CO 2 to inner cells  keeps O 2 away from inner cells  away from Rubisco  Inner cells  Calvin cycle  glucose to veins Physically separated C fixation from Calvin cycle

 Different adaptation to hot, dry climates  separate carbon fixation from Calvin cycle by time  close stomates during day  open stomates during night  at night, open stomates & fix carbon in “storage” compounds  organic acids: malic acid, isocitric acid  in day, close stomates & release CO 2 from “storage” compounds to Calvin cycle  increases concentration of CO 2 in cells  succulents, some cacti, pineapple

C4 plants separate 2 steps of C fixation anatomically in 2 different cells CAM plants separate 2 steps of C fixation temporally at 2 different times solves CO 2 / O 2 gas exchange vs. H 2 O loss challenge

 On global scale, photosynthesis is the most important process for the continuation of life on Earth  each year photosynthesis synthesizes 160 billion tons of carbohydrate  heterotrophs are dependent on plants as food source for fuel & raw materials

CO 2 H2OH2O C 6 H 12 O 6 O2O2 light energy  +++ Sugar Building Reactions Energy Building Reactions Plants make both:  energy  ATP & NADPH  sugars sunlight O2O2 H2OH2O sugars C 6 H 12 O 6 CO 2 ADP ATP NADPH NADP

glucose + oxygen  carbon + water + energy dioxide C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ Heterotrophs + water + energy  glucose + oxygen carbon dioxide 6CO 2 6H 2 O C 6 H 12 O 6 6O 2 light energy  +++ Autotrophs making energy & organic molecules from light energy making energy & organic molecules from ingesting organic molecules exergonic endergonic

H2OH2O Photosynthesis Cellular Respiration sun glucose O2O2 CO 2 plants animals, plants ATP