Lecture 16 Notes
In animals periodic access to food and in plants periodic access to light requires that
special forms of "food" storage. (typically, sugar and fats) i'm assuming that he meant to say that these food storages are made or something. idk
Step 5 (written)
A phosphate molecule from solution displaces the CoA, forming a high energy phosphate linkage to succinate. This phosphate is then passed to GDP to form GTP. (In bacteria and plants, ATP is formed instead.)
Step 1 (written)
After the enzyme removes a proton from the CH3 group on acetyl CoA, the negatively charged CH2- forms a bond to a carbonyl carbon of oxaloacetate. The subsequent loss by hydrolysis of the coenzyme A (CoA) drives the reaction strongly forward
Step 2 (written)
An isomerization reaction, in which water is first removed and then added back, moves the hydroxyl group from one carbon atom to its neighbor
Step 7 Reactants/Intermediate/ Products What's given off Enzyme
Fumarate (add water) ----> malate Enzyme: fumarase
Glycogen can be readily converted to
G1P which is converted to G6P
Step 3 (written)
In the first of four oxidation steps in the cycle, the carbon carrying the hydroxyl group is converted to a carbonyl group. The immediate product is unstable, losing CO2 while still bound to the enzyme
Step 8 (written)
In the last of four oxidation steps in the cycle, the carbon carrying the hydroxyl group is converted to a carbonyl group, regenerating the oxaloacetate needed for step 1
What happens in Aerobic conditions? (long answer) Slide 17
In the presence of oxygen, many organisms convert pyruvate to an activated form of acetate know as acetyl CoA. In this reaction, pyruvate is oxidized (with NAD being reduced to NADH) and decarboxylated (liberation of a carbon atom as CO2). Acetyl CoA then becomes the substrate for aerobic respiration, where NADH is oxidized back to NAD+ by molecular oxygen
Summery of what happens after glycolysis under Aerobic conditions
In the presence of oxygen, many organisms convert pyruvate to an activated form of acetate known as acetyl CoA. In this reaction, pyruvate is both oxidized (with NAD being reduced to NADH) and decarboxylated (liberation of a carbon atom as CO2), Acetyl CoA then becomes the substrate for aerobic respiration, where NADH is oxidized back to NAD+ by molecular oxygen *Slide 8
Step 6 (written)
In the third oxidation step in the cycle, FAD removes two hydrogen atoms from succinate
Two types of Fermentation
Lactate Fermentation Alcohol Fermentation
Step 4 (written)
The a-ketoglutarate dehydrogenase complex closely resembles the large enzyme complex that converts pyruvate to acetyl CoA (pyruvate dehydrogenase). It likewise catalyzes an oxidation that produces NADH, CO2, and a high-energy thioester bond to coenzyme A (CoA)
Step 7 (written)
The addition of water to fumarate places a hydroxyl group next to a carbonyl carbon
Summery of what happens after glycolysis under Anaerobic conditions
When oxygen is absent, pyruvate is reduced so that NADH can be oxidized to NAD, the form of this coenzyme required in reaction Gly-6 glycolysis. Common products of pyruvate reduction are B) lactate (in most animal cells and many bacteria) C) ethanol and CO2 (in many plant cells and in yeast and other microorganisms) *Slide 8
What happens under Anaerobic conditions? (long answer) Slide 17
When oxygen is absent, pyruvate is reduced so that NADH can be oxidized to NAD, the form of this coenzyme required in reaction Gly-6 of glycolysis. Common products of pyruvate reduction are lactate (in animal cells and many bacteria) or ethanol and CO2 (in many plant cells and in yeasts and other microorganisms)
Step 1 Reactants/Intermediate/Products What's given off Enzyme
acetyl CoA + oxaloacetate <-----> S-citryl-CoA intermediate ---> Citrate + HS-CoA + H+ Enzyme: citrate synthase
In organisms that can grow anaerobically, pyruvate is converted to
acetylaldehyde and then into ethanol and CO2. NAD+ is regenerated
Under anaerobic conditions pyruvate is converted to
alternate products such as alcohol + CO2 (e.g., yeast) and lactate (e.g., in muscle) [NADH gives up e-s to make available NAD+ for additional ATP synthesis]
The ATP system serves as a way of ______
conserving and releasing energy in a cell
Seeds often contain large excesses of ____ and ___ to accommodate prolong periods prior to germination (and they make nutrient rich food)
fats and starch
While animals readily convert sugars to ______, they cannot convert FAs to ___; therefore FAs are _____ and converted into ____
fats; sugar; oxidized directly; acetyl-CoA *slide 29
Pyruvate generated via glycolysis may alternatively enter ________ under anaerobic conditions
fermentation pathways
for short term storage, glucose can be stored in the form of ____, which is what.
glycogen - a granular branched polysaccharide in cytoplasm (e.g., liver, muscle)
Other primary inputs (e.g., sugars and glycerol) may enter the ______ and are typically converted into ______
glycolysis pathway; converted into an intermediate in the main pathway *slide 4 and 5
ATP may be generated not only via ______ but also through _____
glycolysis; fermentation or oxidative phosphorylation *slide 6
Step 3 Reactants/Intermediate/ Products What's given off Enzyme
isocitrate ---->oxalosuccinate ---> a-ketoglutarate Given off: NADH + H+, CO2 Enzyme: isocitrate dehydrogenase
If oxygen is present, what happens to pyruvate?
it will become acetyl CoA and proceed to aerobic respiration
In fermentation regeneration of NAD+ yields ____ energy than complete oxidation
less
Step 8 Reactants/Intermediate/ Products What's given off Enzyme
malate ----> oxaloacetate given off: NADH + H+ Enzyme: malate dehydrogenase
In aerobes which use molecular oxygen O2 for growth and reproduction, pyruvate formed during glycolysis is transported into the _____ and then converted
mitochondria converted to CO2 and acetyl- CoA (which is oxidized to H2O + CO2)
Fermentation yields only
modest amounts of energy due to the absence of an external electron acceptor
Sugars and fats are major energy sources for most _________; however, the most useful energy from the oxidation of both kinds of foodstuffs remains stored in______, in which the acetyl group is oxidized to _____(and enters the citric acid cycle).
non-photosynthetic organisms the acetyl-CoA CO2 and H2O *slide 30 also look at slides 31-33
In plants NADPH and ATP are produced by _____ within the cholorplasts; however, the chloroplast membrane is impermeable to both of these carrier molecules.
photosynthesis
Most of the free energy of the glucose molecules is still ____
present in the two molecules of lactate or ethanol molecules
During excess photosynthetic capacity (during the day), chloroplasts convert some of the sugars generated to ____
starch, a polymer of glucose analogous to glycogen in animals
Step 6 Reactants/Intermediate/ Products What's given off Enzyme
succinate ----> fumarate given off: FADH2 Enzyme: succinate dehydrogenase
Step 5 Reactants/Intermediate/ Products What's given off Enzyme
succinyl-CoA ---> succinate + HS-CoA given off: GTP enzyme: succinyl-CoA synthetase
Plants rely heavily on the export of __________ through the same oxidative breakdown of sugars as occurs in animals
sugars from the chloroplasts to mitochondria to generate ATP
Aerobic respiration is
the complete oxidation of glucose to produce carbon dioxide and water in the presence of oxygen (the e- receptor) C6H12O6 + 6O2 ---> 6CO2 + 6H20
Alcohol Fermentation
the end product is ethanol; occur in most plant cells and in microorganisms in yeast
Lactate Fermentaion
the end-product is lactate; occur in some animal cells and many bacteria
In anaerobes, which do not use molecular oxygen, glycolysis is the ______ This is also true for
the main source of the cell's ATP and pyruvate and NADH e-s stay in the cytosol certain tissues in multicellular organisms in which an anaerobic environment may occur (i.e., muscle tissue) *this doesn't make sense but its what's on the slide
Why is fat more important than glycogen for energy storage in animals?
the oxidation of a gram of fat releases ~2X energy as the oxidation of a gram of glycogen. Moreover, there is a 6X difference in the actual mass of glycogen required to store the same amount of energy as fat due to glycogen binding water mass
Fermentation is
the process of energy production in a cell under anaerobic conditions (without oxygen)
Oxygen may be used at a rate greater than _______; the fermentation reactions regenerates _____
the supply in muscle tissue; NAD+ (From step 6 of glycolysis) *slide 11
TAGs stored in fat are hydrolyzed _______
to produce glycerol and fatty acids. FAs are released into the bloodstream
Plants also produce _____
triacylglycerols with varying types and proportions of the class of fatty acid that predominate when compared to animals
Fermentation often results in the accumulation of
waste products such as lactate or ethanol that can be toxic to the cells *picture slide 15
Fat cells (i.e., adiopocytes) store fatty acids in the form of
water insoluble triacylglycerols
____ and ___ are both stored in chloroplasts and serve as reservoirs of energy during periods of darkness
Fat and Starch
the Citric Acid Cycle is also called what?
Tricarboxylic Acid (TCA) Cycle or Kreb's Cycle
Step 4 Reactants/Intermediate/ Products What's given off Enzyme
a-ketoglutarate + HS-CoA ----> succinyl CoA given off: NADH + H+, CO2 Enzyme: a-ketoglutarate dehydrogenase complex
The anaerobic energy-yielding pathways are called
fermentation
One turn of the Citric Acid Cycle produces: and releases:
3 NADH 1 GTP 1 FADH2 releases 2 CO2 molecules *Slide 19 and 20
In fermentation, only about ____% of the free energy potentially available from glucose was obtained
7%
How many steps in the Citric Acid Cycle?
8
Prepare for the Citric Acid Cycle
8 steps you got this doing it twice Slides 20-25
Great Oxygenation Event (GOE) occurred when?
900 million yr or 2.5-2.4 billion years ago
Step 2 Reactants/Intermediate/ Products What's given off Enzyme
Citrate <---> cis-aconitateisocitrate --> isocitrate Enzyme: aconitase