which pathways do cells primarily use to make adenosine triphosphate?

Question

oxidative or glycolytic fibers

Answer 1

Here you go!

Answer 2

Synthesis
ATP can be produced by various cellular processes: Under aerobic conditions, the majority of the synthesis occurs in mitochondria during oxidative phosphorylation and is catalyzed by ATP synthase and, to a lesser degree, under anaerobic conditions by fermentation.


Space filling image of ATP
3D model of ATPThe main fuels for ATP synthesis are glucose and triglycerides. The fuels that result from the breakdown of triglycerides are glycerol and fatty acids.

First, glucose and glycerol are metabolised to pyruvate in the cytosol using the glycolyitic pathway. This generates some ATP through substrate phosphorylation catalyzed by two enzymes: PGK and Pyruvate kinase. Pyruvate is then oxidized further in the mitochondrion.

In the mitochondrion, pyruvate is oxidized by pyruvate dehydrogenase to acetyl-CoA, which is fully oxidized to carbon dioxide by the Krebs cycle. Fatty acids are also broken down to acetyl CoA by beta-oxidation and metabolised by the Krebs cycle. Every turn of the Krebs cycle produces an ATP equivalent (GTP) through substrate phosphorylation catalyzed by Succinyl-CoA synthetase as well as reducing power as NADH. The electrons from NADH are used by the electron transport chain to generate a large amount of ATP by oxidative phosphorylation coupled with ATP synthase.

The whole process of oxidizing glucose to carbon dioxide is known as cellular respiration and is more than 40% efficient at transferring the chemical energy in glucose to the more useful form of ATP.

ATP is also synthesized through several so-called "replenishment" reactions catalyzed by the enzyme families of NDKs (nucleoside diphosphate kinases), which use other nucleoside triphosphates as a high-energy phosphate donor, and the ATP:guanido-phosphotransferase family, which uses creatine.

ADP + GTP ATP + GDP
In plants, ATP is synthesized in chloroplasts during the light reactions of photosynthesis. Some of this ATP is then used to power the Calvin cycle, which synthesizes triose sugars.

If a clot causes a decrease in oxygen delivery to the cell, the amount of ATP produced in the mitochondria will decrease.

Answer 3

ATP as you know stands for Adenosine TriPhosphate.The main role of ATP in a cell is that it acts as a transporter to carry chemical energy within the cell.ATP is also used as signalling molecule.

Answer 4

The glycolytic pathway?... the Krebbs cycle? ... I've forgotten the process since freshman year college bio two years ago

Answer 5

http://www.memorial.ecasd.k12.wi.us/Departments/Science/MAllen/Private_Docs/A&P/PowerPoints/Unit1/Chapter%204a%20(Sec%204.1-4.5)-print.pdf


OR

I. Principles of Energy Conversion
As an open system, cells require outside energy sources to perform cellular work (chemical
transport, & mechanical).
Energy as sunlight flows into ecosystems ---> Photosynthesis (light E to organic molecules)
---> Cells use chemical E to make ATP-the E source for cellular work---> E leaving
organisms as heat.

A. Cellular respiration & fermentation are catabolic (E yielding) pathways
1. Fermentation = An ATP-producing catabolic pathways in which both electron donors
& acceptors are organic compounds.
a. Anaerobic process & results in a partial degradation of sugars.
2. Cellular Respiration = An ATP-producing catabolic process in which the ultimate
electron acceptor is an inorganic molecule, such as oxygen.
a. Catabolic pathway
b. Exergonic process (Free energy change of -686 Kcal/mol)
c. C6H12O6 + 6O2 ---> 6CO2 + 6H2O + E (ATP + heat)

B. Cells recycle the ATP they use for work
1. ATP (adenosine triphosphate)= instability of bonds in three negatively charged phosphate
a. ATP ---> ADP + Pi (cells hydrolyze for energy to drive endergonic reaction)
b. ADP + Pi ---> ATP (cellular reactions regenerate ATP)

C. Redox reactions release energy when electron move closer to electronegative atoms
1. Chemical reactions which involves a partial or complete transfer of electrons from one
reactant to another.
2. Oxidation=loss of electrons (reducing agent=electron donor)
3. Reduction=gain of electrons (oxidizing agent=electron acceptor)
4. Coupled reaction
5. Oxygen is a powerful oxidizing agent= shift of electron sharing in covalent bonds.

D. Electrons fall from organic molecules to oxygen during cellular respiration
1. Valence electrons of carbon & hydrogen lose potential E as they shift toward
electronegative oxygen.
2. Released E is used by cells to produce ATP.
3. Carbohydrates & fats are excellent E source (rich in C to H bonds).

E. The fall of electrons during respiration is stepwise, via NAD+ & an electron transport chain
1. Hydrogens stripped from glucose are not transferred directly to oxygen, but are first
passed to a special electron acceptor-NAD+ .
2. NAD+= Nicotinamide adenine dinucleotide; functions as a coenzyme in the redox
reactions.
a. Found in all cells
b. Assists enzymes in electron transfer during redox reactions.
c. Coenzymes=small nonprotein organic molecule that is required for certain enzymes to
function.
d. During the oxidation of glucose, NAD+ functions as an oxidizing agent by trapping
energy-rich electrons from glucose by dehydragenases.
a) Remove a pair of hydrogen atoms (two electrons & two protons) from substrate.
b) Deliver the two electrons & one protons to NAD+.
c) Release the remaining proton into the surrounding solution.
e. NAD+=oxidized coenzyme (net positive charge)
NADH=reduced coenzyme (electrically neutral)
3. The high E electrons transferred from substrate to NAD+ are then passed down the
electron transport chain to oxygen, powering ATP synthesis (oxidative phosphorylation).
4. Electron transport chains are composed of electron-carrier molecules built into the inner
mitochondrial membrane.

II. The Process of Cellular Respiration
A. Overview
1. In respiration (oxidation of glucose), energy is released as electrons go from higher to
lower energy levels (they lose potential energy).
2. Living systems are experts at energy conversion. 40% of the energy released by
oxidation of glucose is trapped in the form of ATP. The other 60% is given off as heat.
3. Breakdown of glucose takes place in three major sets of reactions:
glycolysis, Kreb's cycle & electron transport system.
a. Glycolysis
a) splitting glucose to pyruvate
b) occurs in cytoplasm
c) produce a little ATP (substrate level phosphrylation)
d) anaerobic - no O2 needed
b. Kreb's cycle
a) complete oxidation of pyruvate to carbon dioxide
b) occurs in mitochondrial matrix
c) produces little ATP (substrate level phosphorylation)
d) yields NADH & FADH2
e) oxygen must be present but not actually used
c. Electron transport system
a) takes place in mitochondria inner membrane
b) chemiosmotic phosphrylation
c) lots of ATP produced
d) needs oxygen as the final electron acceptor
d. There is only a limited amount of ATP generated directly from glycolysis & Krebs.
These stages are primarily a source of high energy electrons which are passed to an
electron carrier: NAD+ or FADH. When electrons are transferred from glucose to
these electron carriers, they lose very little potential energy.

B. Glycolysis harvests chemical energy by oxidizing glucose to pyruvate.
1. One molecule of glucose is split into two molecules of pyruvic acid.
2. Requires an input of 2 ATP molecules.
3. High energy H are removed & passed to NAD+.
4. Substrate gives up phosphate to ADP --> ATP (substrate level phosphorylation).
5. Most organisms use oxygen & carry out aerobic respiration (chemiosmotic
phosphorylation). Some organisms (some bacteria) also use chemiosmotic
phosphorylation but use an electron acceptor other than oxygen
(i.e. sulfate, nitrate, CO2).

C. The Krebs cycle completes the energy-yielding oxidation of organic molecules
(Aerobic Respirations).
1. Oxidation of pyruvate to Acetyl CoA (transition reaction)
a. This reaction links glycolysis to the Kreb's cycle.
b. Occurs in the mitochondria.
Mitochondria: outer membrane (permeable to small molecules & ions)
inner membrane: folded cristae (impermeable to small molecules
& ions; electron transport system embedded in cristae).
c. Pyruvic acid oxidized to acetyl group & one CO2; acetyl group transferred to
coenzyme A (CoA).
2. Krebs cycle (citric acid cycle)
a. Occurs in matrix of mitochondria.
b. Functions in the complete oxidation of fuel molecules.
c. Oxygen must be present but is not actually used in these reactions.

D. The inner mitochondrial membrane couples electron transport to ATP synthesis
1. Electron transport System (ETS)
a. ETS us embedded in the cristae of the mitochondria.
b. ETS is a series of proteins - most with prosthetic groups that act as electron acceptors
& donors.
c. ETS components:
a) FMN - flavin mononucleotide; large transmembranal protein, acts as first proton pump
b) CoQ - coenzyme Q (ubiquinone; actually a lipid); small mobile carrier, proton shuttle
c) cytochromes - all have heme as prosthetic groups
(a) 1st cytochrome complex: cytochromes b & c1
(b) cytochrome c: mobile carrier
(c) 2nd cytochrome complex: cytochromes a & a3
d) Electrons pass down the ETS in a series of oxidation-reduction reactions.
e) The energy released is used to pump protons across the membrane to the inner
membrane space.
f) Oxygen is required for the ETS as the final electron acceptor.

| 2. Chemiosmosis
a. The proton gradient across the membrane is used for the production of ATP to
phosphorylate ATP (chemiosmotic phosphorylation).
b. ATP syntase complexes.

3. Oxidative phosphorylation
a. The process of forming ATP using energy derived from the redox reactions of the
electron transport chain.
E. Cellular respiration generates many ATP molecules by oxidation
1. 40% of energy conversion occurs & the rest is released as heat.

III. Related Metabolic Processes
A. Fermentation
1. Oxidation of glucose in the absence of oxygen
2. Glycolysis produces 2 ATP per glucose under both aerobic & anaerobic conditions.
3. Unless oxygen is present, they can not get into Kreb's cycle or the electron transport
chain reactions.
4. Anaerobic conversion of sugar to some waste product. It includes glycolysis & steps
necessary to regenerate NAD+.
a. alcohol fermentation:
a) pyruvic acid is converted to ethanol, regenerating NAD+.
b) Yeast & many bacteria carry out alcohol fermentation under anaerobic conditions.
c) Alcohol fermentation by yeast is used in backing & brewing.
b. lactic acid fermentation:
a) Pyruvic acid is reduced directly by NADH to form lactic acid.
b) Certain fungi & bacteria are used in the dairy industry to make cheese& yogurt.
c) Human muscle cells behave as facultative anaerobes.
(a) Make ATP by glycolysis & lactic acid when O2 is scarce.

B. Glycolysis & krebs cycle connect to other metabolic pathways
1. Catabolism
a. The primary organic compounds (fats, proteins, & CHO) of cells make up a
metabolic pool for oxidation (obtain energy).
b. Cells oxidize other molecules besides glucose to release energy
a) fat --> fatty acids + glycerol
(a) fatty acids: beta oxidation (e carbon fragmentation to Kreb's cycle as
acetyl CoA)
(b) glycerol: Kreb's cycle
b) proteins --> amino acids --> deamination --> Kerb's cycle
2. Anabolism
a. These molecules can be used for biosynthesis of macromoleucles.
b. Intermediates of glycolysis & Kreb's cycle serve as precursors.
c. The molecules of CHO, fats, & proteins can all be interconverted to provide for
cell's needs.

C. Feedback mechanisms control cellular respiration
1. Negative feedback inhibition
a. The end product of a pathway inhibits an enzyme early in the pathway, providing
proper amounts of substances.
b. The supply of ATP regulates respiration.
c. Allosteric enzymes