Dear Shirley, Earth Angel:

I noticed it a long time ago and didn’t let you know: I like the way you explain science. You use a word and in parenthesis you shortly explain what it is. This is very helpful. Your presentation of the subject matter is very clear. It reminds me of a microbiologist teacher I had long ago. She seemed to know a whole lot about microbiology. Seemed to be very confident about her knowledge. But I couldn’t follow what she was saying. She talked so fast, used all kinds of words, names of micro-organisms and it was all a jumbled mess- didn’t reach my brain as anything decipherable. I can still see, in my mind’s eye, what I saw then: her mouth, talking and talking and nothing coming out, not for me.

So, I appreciate orderly presentation of a subject matter when I see it and you do it well.

And now to what you wrote, my comments/ suggestions of adding the sentences I am adding are in double parentheses (( )) so to differentiate from your single parentheses, my comments are limited to my understanding and information processing abilities:

“kinase enzymes are enzymes that transfer phosphate molecules from one substance to another. should i also include photosynthesis’s production of atp as well? ((depending on the topic of the essay and instructions from the teacher- can you ask the teacher if the instructions are unclear? If the topic is “atp’s form, components, structure and mechanism” I would include photosynthesis, at least in a short enough paragraph. I don’t think up to a half page overall explanation of atp production in photosynthesis ca hurt))

“do you think i accurately demonstrate an understanding of atp and my content and sentences make sense? this essay is out of 40 points and it is due in 10 days, can you give me a grade you think it would receive? i think i might receive a 30/40. ((Can’t give you a grade because I am not familiar with the grading structure that you are using and don’t feel I am qualified to grade))

“Substrate level phosphorylation occurs when a kinase enzyme transfers a phosphate group from a substance to ADP producing ATP during glycolysis and the Krebs cycle.” ((reads perfectly clear to me, as clear as such complicated process can be presented!))

“…The ATP molecule consists of a sugar molecule (ribose) attached to a base that is composed of carbon and nitrogen atoms (adenine). Attached to the other side of the ribose are three phosphate groups (a phosphate group consists of one phosphorus atom bonded to 4 oxygen atoms). ((perfect, says I.
ATP Hydrolysis Powers Cellular Work

“The phosphate bonds in ATP (adenosine triphosphate) can be broken down by water. When ATP loses a phosphate group in water, this releases energy and creates the products ADP (adenosine diphosphate with two phosphate groups) and an inorganic phosphate. This is an exergonic reaction meaning energy is released and the reactants (ATP + Water) have a higher energy than the products ((add here the products in parentheses, like you did following the word “reactants)).

The hydrolysis (breakdown in water) of ATP releases energy because all three phosphate groups ((of ATP)) are negatively charged and the like charges repel each other creating an instability in the ATP molecule. ((This instability causes the ATP molecule to break down.))

The energy released from ATP hydrolysis can be used to power endergonic reactions (absorb energy to start reaction) ((“absorb energy to start reaction”- fix this one as it doesn’t define “endergonic reactions” well enough))by the transfer of a phosphate group from ATP to some other molecule such as the reactant in the reaction.

ATP hydrolysis powers cellular work since ATP hydrolysis leads to a change in a protein’s shape and its ability to bind to another molecule. When ATP is bonded noncovalently to a motor protein ((a few words defining “motor protein”?)), the ATP hydrolysis releases ADP and an inorganic phosphate allowing another ATP molecule to bond ((with What?)).

At each step, the motor protein changes shape and its ability to bind to the cytoskeleton (framework of the cell) resulting in the protein’s movement along the cytoskeletal track. From the exergonic breakdown of ATP, the energy released can be used to power the endergonic reaction of regenerating ATP when a phosphate is added to ADP. The ATP cycle results in the exergonic reaction of breaking apart ATP and using the energy released to power the endergonic reaction of regenerating ATP. ((seems good enough to me))

ATP in Cellular Respiration
Cellular respiration is a metabolic reaction that takes place in cells to convert energy from nutrients (such as food) ((isn’t it always from glucose? If so, I would write instead “to convert energy from glucose and eliminate “such as food”)) into ATP and release waste products. Aerobic Respiration requires oxygen to produce ATP.

((new paragraph here?))During cellular respiration shown in the equation here: C6H12O6+ 6O2 ——> CO2 + H2O, glucose (C6H12O6) is oxidized (loses electrons) to oxygen, while oxygen is reduced (gains electrons) and the products carbon dioxide (CO2) and H2O (water) are released.

((Another new paragraph?))The first step of cellular respiration, glycolysis which is the splitting of glucose sugar can occur with or without oxygen. The first half of glycolysis is endergonic since it requires energy in the form of two ATP molecules, while the second half is exergonic since four ATP molecules are produced (energy is released. ((no need here for “energy is released” since you already explained “exergonic” and one explanation for each term per essay is enough))

In glycolysis, a hexokinase enzyme transfers a phosphate group to ATP making it more reactive; this process uses 1 ATP molecule and produces Glucose 6-phosphate. During metabolism, glucose 6-phosphate is converted to Fructose 6-phosphate. Another ATP molecule is used when phosphofructokinase enzyme transfers a phosphate group to fructose 6-phosphate making it Fructose 1,6 biphosphate. Fructose 1,6 biphosphate splits into two different three-carbon sugars which later breaks down into pyruvate.

Although glycolysis produces 4 ATP molecules in the second half of its reaction (breakdown of Fructose 1,6 biphosphate to 2 pyruvate molecules), it only produces a net of 2 ATP molecules since 2 were used to start the glycolysis process. The end products of glycolysis are 2 pyruvate molecules, 2 ATP molecules and 1 NADH.

If oxygen is present pyruvate enters the mitochondria of eukaryotic cells and is converted to acetyl coenzyme A (acetyl coA); this releases one molecule of CO2 and NAD (coenzyme in living cells that functions as an electron acceptor). When oxygen is not present, fermentation of the pyruvic molecule will occur.

((I am starting new paragraphs for clarity of presentation)) When oxygen is present acetyl coA enters into the Krebs/ Citric Acid Cycle inside the mitochondrial matrix and is oxidized to CO2 while reducing NAD to NADH. With each turn of the Krebs cycle, a pyruvate is used and one turn of the cycle produces 3NADHs, 1 ATP, 1 FADH2 and CO2. The Krebs cycle also produces water when NADH and FADH2 shuttle electrons down the electron transport chain to oxygen, which is the last electron acceptor; while at the same time protons are being pumped from the mitochondrial matrix to the intermembrane space and oxygen is reduced to water.

NADH and FADH2 can be used in the electron transport chain to create ATP by oxidative phosphorylation. During oxidative phosphorylation which takes place in the inner mitochondrial membrane, NADH and FADH2 are used to pump hydrogen ions across the membrane against proton gradients (chemiosmosis process). A protein complex, ATP synthase which is in the membrane and enables protons to pass in different directions, enables ATP production when the protons move down the gradient. It takes ATP to pump a proton against a gradient and since protons have already been pumped against the gradient (done by NADH and FADH2), they can flow back into the mitochondrial matrix producing ATP in the process.((I think your description is excellent, as clear as can be is my impression as I am not following all the details, being removed from those by so many years since studied it, but my… Clarity Instinct says: as clear as can be, good job!))

NAD and FAD
NAD and FAD are important to cellular respiration since they are coenzymes that carry protons or electrons from glycolysis and the Krebs Cycle to the electron transport chain. FAD is the oxidized (loses electrons) ((I think it is okay to repeat explanation here “loses electrons” even though you already did because it’s been a while- in the essay- since you did and it is such a short definition, only a couple of words)) form while FADH2 is the reduced (gains electrons) form. NAD+ is the oxidized form, while NADH is the reduced form.

Anaerobic Respiration (without oxygen)
Fermentation occurs without oxygen and the electron transport chain. It turns NADH and pyruvate produced in glycolysis into NAD+ and an organic molecule such as lactate in lactic acid fermentation and ethyl alcohol & CO2. Fermentation can produce ATP as long as there is an adequate supply of NAD+ to accept electrons during glycolysis. However, in the presence of oxygen (aerobic respiration), NADH and pyruvate can generate more ATP than glycolysis alone.

((I think this is excellent, very clear. I am quite impressed you can present such a complicated process as clearly as you have. Make sure your essay fulfills the specified requirements for the essay for quantity and quality, that is length and content)).

anita

anita