chap 9-11 outline

8/7/2019 Chap 9-11 Outline

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Chapters 9-11 AP Bio OutlineA) Cellular Respiration

1) Respiration is a redox reaction: the fuel is oxidized and oxygen is reduced to release energy.(a) Glucose, the fuel most commonly used by the cell, releases about 686 kcal/mol of energy.

(b) NAD+, nicotinamide adenine dinucleoside, a derivative of niacin, functions as an oxidizing agent

2) Glycolysis. Net yield (per glucose): 2 ATP, 2 NADH, 2 Pyruvate (C3H3O3-)

(a) Glycolysis takes place in the cytoplasm of the cell

(b) Pyruvate is moved into the mitochondria, where it is chemically groomed for the Krebs cycle

i Ths COO- group is given off as CO2ii The molecule is oxidized to form acetate, and NADH are formed.iii Coenyze A, a suflur-containing compound, is attached to acetate by an unstable bond

3) Krebs Cycle completes the oxidation of pyruvate.

(a) Products (per glucose): 6 NADH, 2 FADH2, 2 ATP, 3 CO24) During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis


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(a) The electron transport chain harnesses the energy of electrons to move protons across the inner

mitochondrial membrane.

(b) Order of electron carriers:

Flavoprotein (FMN) [Contains

a flavin mononucleotide group],

iron-sulfur protein (FeS),

ubiquinone (Q), cytochrome b(Cyt b), FeS, Cyt C1, Cyt c, Cyt

a, Cyt a3, O2.

(c) FADH2 deposits its electrons incomplex 2, a lower-energy state

than complex 1.

(d) The movement of protons into the intermembrane space generates an electrochemical potentialacross in the inner membrane, harnessed by ATP synthase to produce ATP.

(e) For each molecule of glucose that goes into cellular respiration, 32-34 ATP are produced.

5) Fermentation can produce ATP without oxygen available.(a) Alcohol fermentation: pyruvate is reduced to alcohol in two steps, with release of CO2

(b) Lactic Acid fermentation: pyruvate is reduced to lactic acid with no release of CO26) Glycolysis and the Citric Acid Cycle connect to many other metabolic pathways

(a) Glycolysis can accept a wide range of carbohydrates for catabolism.(b) Proteins have their amino groups removed and are then inserted where appropriate.

(c) Fats are broken into glycerol (enters at middle of glycolysis) and two-carbon chunks of fatty

acids (enter directly into the Krebs cycle)7) Phosphofructokinase is allosterically inhibited by ATP and citrate, but stimulated by AMP.

B) Photosynthesis.

1) Photosynthesis occurs in the chloroplast of plant cells.(a) Chloroplasts contain chlorophyll, a green pigment.

(b) Most found in the cells of the mesophyll, the tissue in the interior of the leaf.

(c) Two membranes enclose the stroma, the dense fluid within the chloroplast.i Membraneous sacs called thylakoids segregate the stroma from another environment, the

thylakoid space.

2) Photosynthesis uses an electron source and carbon dioxide to produce sugars.

(a) 6 CO2 + 6 H2O = C6H12O6 + 6 O2(b) The electron donor in photosynthesis is water, which is oxidized. CO2 is

reduced.

(c) Hypothesis confirmed using an 18O isotope to track the oxygens.3) The light reactions take place in the membrane of the thylakoids

(a) Absorption spectra show that chlorophyll a is most effective at orange and

far violet wavelengths and chlorophyll b is most effect at blue and orange.

Carotenoids are effective at violet to green.(b) Photosystems are composed of several light-harvesting centers arranged

around a reaction center,

i The light-harvesting complexes have arrays of pigments bound toproteins which funnel the energy they absorb to the reaction center.

ii The reaction center is composed of two special chlorophyll a molecules

and a primary electron acceptor. The chlorophyll a sends an energizedelectron to the primary electron acceptor.


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iii The cytochrome uses the energy of the electrons to pump H+ into the thylakoid space to

produce ATP; cyclic electron flow uses only photosystem 1 to produce more ATP than

NADPH.

(c) The Calvin cycle (dark reactions) fix CO2 to produce sugarsi The enzyme Rubisco catalyses the carboxylation of ribulose-1,5-bisphosphate, RuBP, a 5-carbon

compound, by carbon dioxide (a total of 6 carbons) in a two-step reaction. The product of thefirst step is enediol-enzyme complex that can capture CO2 or O2. Thus, enediol-enzyme complex

is the real carboxylase/oxygenase. The CO2 that is captured by enediol in second step produces asix-carbon intermediate initially that immediately splits in half, forming two molecules of 3-

phosphoglycerate, or PGA, a 3-carbon compound (also: 3-phosphoglycerate, 3-phosphoglycericacid, 3PGA).

ii The enzyme phosphoglycerate kinase catalyses the phosphorylation of 3PGA by ATP (which

was produced in the light-dependent stage). 1,3-Bisphosphoglycerate (glycerate-1,3-bisphosphate) and ADP are the products. (However, note that two PGAs are produced for everyCO2 that enters the cycle, so this step utilizes two ATP per CO2 fixed.)


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1. Triose phosphate isomerase conveall of the G3P reversibly intodihydroxyacetone phosphate (DHAP), a 3-carbon molecule.

2. Aldolase and fructose-1,6-bisphosphatase convert a G3P and a Dinto fructose 6-phosphate (6C). Aphosphate ion is lost into solution.

3. Then fixation of another CO2generates two more G3P.

4. F6P has two carbons removed bytransketolase, giving erythrose-4-phosphate. The two carbons ontransketolase are added to a G3P, givinthe ketose xylulose-5-phosphate (Xu5P

5. E4P and a DHAP (formed from onthe G3P from the second CO2 fixationconverted into sedoheptulose-1,7-bisphosphate (7C) by aldolase enzyme

6. Sedoheptulose-1,7-bisphosphatase

(one of only three enzymes of the Calvcycle that are unique to plants) cleavessedoheptulose-1,7-bisphosphate intosedoheptulose-7-phosphate, releasing ainorganic phosphate ion into solution.

7. Fixation of a third CO2 generates more G3P. The ketose S7P has twocarbons removed by transketolase, giviribose-5-phosphate (R5P), and the twocarbons remaining on transketolase aretransferred to one of the G3P, givinganother Xu5P. This leaves one G3P as product of fixation of 3 CO2, withgeneration of three pentoses that can beconverted to Ru5P.

8. R5P is converted into ribulose-5-

phosphate (Ru5P, RuP) by phosphopenisomerase. Xu5P is converted into RuPphosphopentose epimerase.

9. Finally, phosphoribulokinase (anoplant-unique enzyme of the pathway)phosphorylates RuP into RuBP, ribulo1,5-bisphosphate, completing the Calvcycle. This requires the input of one A

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iii The enzyme G3P dehydrogenase catalyses the reduction of 1,3 BPGA by NADPH (which isanother product of the light-dependent stage). Glyceraldehyde 3-phosphate (also G3P, GP, TP,PGAL) is produced, and the NADPH itself was oxidized and becomes NADP+. Again, two

NADPH are utilized per CO2 fixed.

iv The cycle must turn three times in order to produce 1 G3P.

v Net consumption for 1 G3P: 9 ATP, 6 NADPH, 3 CO2(d) Photorespiration is an evolutionary relic:

i Occurs when O2 concentration is high and is mostlyrestricted to C3 plants.

ii Photorespiration occurs when rubisco adds an O2 group toRuBP instead of a CO2.

iii Splits to produce produces phosphoglycerate andphosphoglycolate (PPG), PGA re-enters the Calvin cycle andis simply converted back to RuBP. PPG must be moved to

the peroxisomes/mitochondria to be reintegrated.

(e) C4 and CAM plants evolved to combat photorespiration in arid orhot environments by separating fixation and the Calvin Cycle.

i C4 plants have tightly arranged mesophyll cells (site of

fixation) around bundle-sheath cells (site of Calvin Cycle) Carbon fixation carried out by Phosphoenolpyruvate

carboxylase, (PEP Carboxylase), which attaches CO2 toPEP to form oxaloacetate, a 4-carbon sugar.

Oxaloacetate is converted to malate, which is moved to the bundle-sheath cells.

In the bundle-sheath cells, malate is split into CO2 and pyruvate, which is converted back into

PEP. The CO2 enters the Calvin Cycle.ii CAM (crassulacean acid metabolism) plants separate the steps in time.

Use malate manufactured during the night to run Calvin Cycle during the day.

C) Mechanisms of Cell Communication

1) Reception: a signal molecule binds to a receptor molecule, initiating a respone.


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chap 9-11 outline

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