AP Biology – Cell Respiration & Photosynthesis SGFor review, see AP Biology – Cell Membrane and Mitosis SG

1) Cell Respiration ~occurs in the mitochondria – pyruvate enters the mitochondria and is then altered

in the Krebs cycle*catabolic process (breaks down)

A) Formula~[C6H12O6 + 6 O2 ---(energy)--- 6 CO2 + 6 H2O + ATP]

B) Glycolysis~occurs in the cytoplasm of a cell; anaerobic activity w/ 10 reactions~glucose molecule is split in half creating 2 ATP and 2 pyruvic acids

*makes a total of 4 ATP – uses 2 to start the process; turns into PGAL which creates pyruvates

*2 molecules of NADH are produced after PGAL is turned into pyruvic acids

~4-6% of total energy is available from one glucose moleculeC) Anaerobic Respiration

~occurs when there is no oxygen present in the system1) Lactic Acid Fermentation~yields no additional ATP (net gain is 2 ATP from glycolysis)

*occurs in muscle cells and microorganisms*lactate can be removed from cells and taken to the live; undergoes gluconeogensis converting lactate into glucose

~recycles the needed NAD+ for glycolysis to oxidize PGAL; no CO2 is released*pyruvic acids are turned into lactic acid with the addition of NAD+

2) Alcoholic Fermentation~yields no additional ATP (net gain is 2 ATP from glycolysis)

*occurs in yeasts or bacteria creating ethyl alcohol and CO2

~recycles the needed NAD+ needed for glycolysis to oxidize PGAL~yeasts are considered “facultative anaerobes” – aerobic organisms turned

anaerobic organism*bacteria are “obligate anaerobes” – only anaerobic organism (no O2

acceptance)D) Aerobic Respiration

~occurs in the presence of oxygen~pyruvic acid is oxidized (loses an electron: e-) to an acetyl group combining with “Coenzyme A” (by-product:CO2) to create Acetyl-CoA (a two-carbon molecule)

*forms NADH1) Krebs Cycle (Citric Acid Cycle) (8 steps)~located in the matrix of the mitochondria

*prokaryotes: occurs in the cytoplasm~happens once per pyruvate (a total of 2 pyruvates from glycolysis = 2 cycles)~aka the Tricarboxylic Acid Cycle (TCA Cycle)~Acetyl-CoA combines with oxaloacetate to form citrate (6-carbon molecule)

*citrate donates two hydrogens (H+) to two NAD molecules (now NADH’s) and releases CO2 into the cytoplasm

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*two molecules of NADH are formed; enough energy is released to phosphorylate ADP into ATP via substrate-level phosphorlyation*succinyl-CoA will form after the donation of H+ and formation of CO2; turns into oxaloacetate after donating 2H+ and 2 e- to FAD (creating FADH2’s) and H+ to NAD (now NADH)*the cycle repeats at the end after forming oxaloacetate*H+ and e- will be donated to the ETS; oxygen will accept the particles

~because two pyruvates entered the Krebs cycle, there is total of 6 NADH made and 2 FADH2

~glucose forms CO2, NADH, and FADH2 for a total worth of 24 ATP (makes 2 ATP directly)

*main energy source for organisms*FADH = 2 ATP / NADH = 3 ATP

2) Electron Transport System (or Electron Transport Chain)~final stage of the aerobic respiration occurs in the inner membrane of the

mitochondria (eukaryotes)*NADH and FADH2 enter the system after Krebs cycle

~e- are donated by NADH and FADH2; H+ are released into the inner membrane space to be used by the proton gradient during the synthesis of ATP (via ATP synthase)

*electrons are accepted by proteins the inner membrane and are pulled by O2 down the ETC; hydrogens are expelled into the inner membrane space creating a chemiosmotic gradient

~Chemiosmosis: the coupling of ATP synthesis to the electron transport through a proton gradient; NADH releases electrons (e–) and hydrogen ions (H+) in the mitochondrial matrix; H+ move into the intermembrane space of the mitochondria while e– the travel on the ETC to the ATP synthase (integral protein) which accepts protons (H+) an creates ATP

*ETS and Chemiosmosis are collectively known as oxidative-phosphorlyation~electrons (e-) are accepted by oxygen molecules, combining with protons (H+)

forming H2O~30–40% efficient; 60% of release energy is captured by heat (esp. endotherms) for temperature maintenance

*34 ATP made by ETS ~Second Law of Thermodynamics (Law of Entropy): living systems move toward randomness/disorganization or entropy

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E) Oxygen Debt~creatine phosphate is stored in muscles (+ ADP = ATP and creatine)

*when creatine phosphate is depleted, muscles and liver are loaded with lactate

*heavy breathing is exhibited to reestablish homeostasis within the bounds of muscles/liver

~lack of oxygen results in anaerobic fermentation (i.e.: exercise and physical conditioning)

*conditioning results in higher glucose storage in muscles, increase in lung capacity (oxygen amount), and heart volume (blood pump-age)

2) Photosynthesis~depends on environment, temperature, sun intensity, and availability of water~endergonic reaction: energy is needed to start the process (i.e.: light)~plants are considered autotrophs (self-feeders or producers)

*specifically: a photoautotroph~50% of the energy is used for plant cells’ respiration

A) Formula~[6 CO2 + 6 H2O --- (ATP) --- C6H12O6 + 6 O2]~uses the products of cellular respiration to create a 6-carbon sugar (glucose) and oxygen

B) Wavelengths~accepts a small amount of energy needed to excite an electron and cause a chemical reaction~plants accept red (700nm/low energy) light to violet (400nm/high energy) light

*green light is reflected = color is not accepted by chlorophyll*black pigments absorb all wavelengths / white pigments reflect all wavelengths

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*the shorter the wavelength, the higher the energyC) Pigments

~located in the thylakoids; absorb photons from the sunlight~“Chlorophyll a” turns light energy into chemical energy w/ the absorption of violet and red light

*the most commonly abundant chlorophyll in plants~“Chlorophyll b” absorbs blue and orange light~Carotenoids are found in the thylakoid membrane; accessory pigments that absorb blue, green, and orange light; absorb/reflect excessive light

D) Light–Dependent Reactions~requires sunlight to produce ATP and NADPH2 for use in the light–

independent reactions~ in the chloroplasts’ grana/grouped thylakoids; absorb light energy and

convert it into chemical energy*created molecules of ATP and NADPH2

~Photosystem I: a cyclic pathway that absorbs red light (p700 is a reaction center)

*the old, simple way to make small amounts of ATP – cannot sustain large photosynthetic plants

*energized electrons enter the ETS powering light reactions in photosynthesis

~Photosystem II: a non-cyclic pathway that absorbs red light (p680 is a reaction center)

*relied on by most plants for energy yielding both ATP and NADPH2

*one-way flow of electrons creates a chemiosmotic differential to reduce NADP+ to NADPH2

* O2 escapes into the atmosphere*2 H2O molecules converge with 2 e- from Chlorophyll a creating H2 which fuses with NADP (from dark reactions) to make NADPH2

*pigment red absorbs photons moving electrons into the ETS and reducing NADP+ to NADPH2

~water is needed to donated H2 to NADP to create NAPH2 which donates said protons to Calvin cycle

E) Light–Independent Reactions OR Calvin–Benson Cycle~occurs mostly in the day but does not need sunlight to occur~cyclic pathway that occurs in the chloroplast’s stroma

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~uses ATP and hydrogen from NADPH2 to make PGAL; CO2 is the carbon source

*CO2 from the cytoplasm reacts with RuBP (5-carbon sugar) to make 2 PGA (two 3-carbon sugars); 2 ATP molecules become ADP donating 2 phosphates (phosphorlyation) and energy along with H2 from NADPH2 (light reactions) to make 2 PGAL (two 3-carbon sugars)*2 PGAL molecules are then converted into glucose of RDP (aka RuBP) to repeat the cycle*RuBp or RDP stands for Rubsico; an enzyme that is the most abundant protein on Earth and in chloroplasts

~called the Calvin-Benson Cycle or C3 Plant Cycle*produces PGAL (6 cycles = glucose) and RDP (RuBP)*6 CO2 are used to form one sugar molecule (glucose = C6H1206)*exhibited in C3 Plants (PGA molecules are a 3-carbon molecule)*PGAL can be used to make sugar (glucose), fatty acids, starches, glycerol, or amino acids; can also produce ATP in mitochondria through cell respiration

~Calvin-Benson Cycle is 38% efficient storing carbohydrates as starch (stems), tubers (potatoes) or sucrose in onions, beets, and sugar cane

*used for growth and reproductionF) The Photosynthesis A.P. Lab

~DPIP tests whether light and chloroplasts are needed for photosynthetic light reactions to occur

*in the presence of light, DPIP will change from the blue to colorless*substitutes the NADP+ electron

acceptor~Chromatography paper showed the solubility relationships between the solute and chlorophylls (a, b, and Carotenoids)

*pigmentation lines will rise depending on the attraction of solute to the chlorophyll*higher the solubility = further the distance on the chromatography paper

3) CAM Plants Overview~water-conserving pathway in plants located in arid conditions

*plant’s stomata close during the day and open during the night~plants gather CO2 into organic acids at night; during the day CO2 is released into chloroplast

*lose less water than C3 and C4 plants by closing the stomata – no H2O escapes

*occurs at different times in the same cells~reverse of C3 and C4 plants

4) C4 Plants OverviewA) Hatch-Slack Pathway

~occurs before the Calvin-Benson Cycle~CO2 is turned into a 4-carbon compound rather than a three-carbon

compound (C3 Plants)

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*a carbon fixation pathway; CO2 combines with phosphoenolpyruvate (PEP) and creates oxaloacetate (4-carbon molecule) which is then transferred to the Calvin Cycle*take advantage of sunlight by performing photosynthesis at full speed;

~occurs in plants that are located in hot, dry climates (does go through the Calvin Cycle)

*use more ATP to create glucose, but they perform photosynthesis at a higher rate

~pathway reduces photorespiration and enhances sugar production*occurs in different cells at the same time

5) Photorespiration Overview~uses O2 and releases CO2

*reduces the net productivity of a plant*a 2-carbon sugar (O2 + RuBP) enters peroxisomes, which use the O2 and make intermediates to be used in the mitochondria; becomes CO2

~when CO2 is scarce, O2 is used instead*consumes ATP producing zero ATP*neutralizes harmful light effects that are considered excessive to plants

6) Vocabulary Aa) Glycolysis: splitting glucose into two molecules of pyruvic acid; occurring in

the cytoplasm b) Cell Respiration: takes sugar (glucose) and oxygen into the mitochondria to

make ATPc) Krebs Cycle: (citric acid cycle) a series of reactions that break down glucose

by oxidating the pyruvic acid to CO2 creating the 6-carbon molecule citrated) Electron Transport: makes a total of 34 ATP and H2O; occurs in the

mitochondria where an electron carrier molecule shuttles electrons during redox reactions releasing energy used to make ATP*Redox Reactions: a chemical reaction where an electron is lost and an electron is gained

e) Fermentation: the partial degradation of sugars in the body that occur w/ the lack of oxygen; lactic acid fermentation and alcoholic fermentation occur as anaerobic respirations; no yield of ATP

f) Matrix: a compartment in the mitochondria where enzymes are located for the ETS to make ATP; location of a mitochondria’s DNA and ribosomes

g) Electron Transport System: third stage of cell respiration; produces 34 ATP; a collection of molecules embedded in the inner membrane of the mitochondria (matrix) – in eukaryotes

h) Oxidative – Phosphorylation: oxidizes (adds an oxygen molecule) nutrients and phosphorylates (adds a phosphate) ADP to make ATP

i) Enzymes: makes energy by catabolic reactions or starts chemical reactions through anabolic means; lowers the activation energy; a globular protein and chemical catalyst

j) Glucose: a 6-carbon sugar used in Glycolysis to make 2 ATP and 2 pyruvic acids

k) Lactic Acid Fermentation: occurs w/o the availability of oxygen; anaerobic effect after Glycolysis that converts the pryuvates into lactic acid (lactate) w/o the release of CO2

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l) NAD+: (nicotinamide adenine dinucleotide) a coenzyme that accepts an electron and acts as an electron carrier in the ETS; used in creating a proton gradient (chemiosmosis); the most versatile electron carrier/acceptor in cellular respiration

m) NADH: made in Glycolysis; worth 3 ATP in the ETSn) FADH2: (flavin adenine dinucleotide) two are made in the Krebs Cycle and are

worth 2 ATP individually in the ETSo) ATP: (adenosine triphosphate) an energy molecule that is produced by the

mitochondria; used by cells as an energy source; 38 are made total in cell respiration; used in photosynthesis to create glucose*[adenine + 5-carbon sugar (ribose) + 3 phosphates]

p) Crista: (plural: Cristae) inner membrane of the mitochondria that houses the electron transport chains and molecules of the enzyme catalyzing the synthesis of ATP (ATP synthase)

7) Vocabulary Baa) Photons: a discrete amount of light energy that behaves as if it were a particlebb) Absorption Spectrum: the range of a pigment’s ability to absorb various

wavelengths of lightcc) Thylakoid: a flattened membranous sac inside a chloroplast; exist in an

interconnected system in the chloroplasts and contain the molecule “machinery” used to convert light into chemical energy

dd) Stroma: located in the chloroplast, the dense fluid surrounds thylakoid membranes; involved in the synthesis of organic molecules from CO2 to H2O

ee) Grana: (singular: Granum) a stack of thylakoids in chloroplast; function in the light–dependent reactions of photosynthesis

ff) Fixation of Carbon: the initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism

gg) Photophosphorlyation: the process of generating ATP from ADP and a phosphate by means of a proton-motive force generated across the thylakoid membrane of chloroplast during light-reactions of photosynthesis

hh) Cyclic Electron Flow: a route of electron flow during the light reactions of photosynthesis that involve only Photosystem I; produces ATP but not NADPH or O2

ii) Stomata: a microscopic pore surrounded by guard cells in the epidermis of leaves and stems; allows gas exchanges between the environment and interior of the plant

jj) Hatch-Slack Pathway: occurs before the Calvin cycle; converts CO2 into a four-carbon sugar before releasing it into the Calvin Cycle; uses more ATP to create glucose but photosynthesis occurs at a faster, more direct, rate

kk) NADPH2: [NADP+ + H = NAPH2] temporarily stores energized electrons produced during light reactions

ll) Calvin Cycle: the second phase of photosynthesis – after light–dependent reactions – involves the fixation of CO2 from the atmosphere and reduction of fixed carbon into a carbohydrate (redox reaction)

mm) Photorespiration: consumes O2 and ATP releasing CO2 and decreasing photosynthetic output; usually occurs on hot, dry, bright days when a plant’s stomata closes *[O2 concentration is > than the CO2 concentration]

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nn) CAM Plants: plants that adapt for photosynthesis by means of crassulacean acid metabolism – acidic conditions; CO2 enters the stomata at night and is converted into organic acids releasing CO2 for the Calvin cycle in the day

oo) C4 Plants: a plant in which the Calvin Cycle is preceded (skipped) by reaction that incorporate the CO2 into a 4-carbon compound; the end product of the reaction supplies CO2 for the Calvin cycle

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