Metabolism

What is the yield of the citric acid cycle per molecule of acetyl CoA?

1 ATP/GTP 3 NADH 1 FADH2

What is the net yield from the Embden-Meyerhof pathway?

2 ATP 2 molecules of pyruvate 2 NADH 2 H+

What is the yield of the citric acid cycle for one molecule of acetyl CoA?

2 CO2 molecules 3 NADH molecules 1 FADH2 Either 1 GTP or 1 ATP.

What is the yield of the pentose phosphate glycolytic pathway?

2 NADPH per molecule of glucose (reducing power), erythrose 4-phosphate and ribose 5-phosphate.

What are the two phases of the Embden-Meyerhof pathway?

6-carbon phase and the 3-carbon energy-conserving phase.

What is glycolysis?

A central metabolic pathway that converts glucose into pyruvate.

What is proton motive force? What is it used for?

A force that is generated by the passing of electrons down the ETC while simultaneously pumping hydrogen protons through the membrane. This force is used to synthesize ATP from ADP and inorganic phosphate via ATP synthase.

What is gluconeogenesis?

A glycolytic pathway that runs in reverse (Pyruvate to glucose).

What is ATP?

A molecule that is found within nearly all cells. It supplies energy for many chemical reactions.

What is a fueling reaction? Name the general inputs and outputs. Is this anabolism or catabolism?

A reaction that uses energy, electrons and carbon to generate ATP, Reducing power, and precursor metabolites. This reaction is a catabolic reaction (except CO2 fixation).

What is a precursor metabolite?

A small organic molecule that provides the necessary carbon skeleton for the synthesis of monomers.

What is energy generally conserved as in cells?

ATP.

Describe the steps of the citric acid cycle. Have fun now....

Acetyl CoA condenses with 4C oxaloacetate to form 6C citrate. A series of oxidation reactions occur, generating NADH. The 2 carbons from acetyl CoA are lost as CO2, forming Succincyl-CoA (high energy). Succinyl-CoA is cleaved from CoA; the energy released is used to make GTP/ATP. Further oxidation reactions generate FADH2 and NADH. 4C oxaloacetate is regenerated. Rinse and repeat.

What are the three types of chemoorganotrophic metabolisms? What is the main difference between these types of metabolisms?

Aerobic respiration Anaerobic respiration Fermentation The difference between these metabolisms lies in how they produces the three main products of fueling reactions.

What organisms use the pentose phosphate cycle?

All organisms.

What is a conjugate redox pair?

An electron acceptor its conjugate electron donor.

How are electrons obtained in a chemoorganotrophic fueling reaction?

An organic energy source is oxidized, which releases electrons, which reduce the electron carriers (NAD+ and FAD).

What is a primary producer?

An organism that fixes CO2.

What is a chemotroph?

An organism that oxidizes organic or inorganic compounds to receive its energy.

What is a lithotroph?

An organism that reduces inorganic molecules for electrons.

What is an autotroph?

An organism that uses CO2 as its sole or primary biosynthetic carbon source.

What is a phototroph?

An organism that uses light as its energy source.

What is an organotroph?

An organism that uses organic molecules as its electron source.

What is a heterotroph?

An organism that uses organic molecules sourced from other organisms as its carbon source.

What is the difference between autotrophs and heterotrophs with respect to the generation of precursor metabolites?

Autotrophs: use CO2 fixation to generate precursor metabolites. Heterotrophs: use central metabolic pathways to generate precursor metabolites (TCA cycle and glycolytic pathway

What is the difference between the yield in bacterial and eukaryotic aerobic respiration?

Bacterial aerobic respiration tends to generate less ATP.

What connects the complexes of the ETC?

CoenzymeQ and Cytochrome C.

Where does the citric acid cycle take place in eukaryotes and prokaryotes?

Cytoplasm of prokaryotes. Mitochondrial matrix of eukaryotes.

What are the two electron carriers in chemoorganotrophic fueling reactions? What are their reduced forms?

Electron carriers: NAD+ and FAD Reduced electron carriers: NADH and FADH2

What are the three main glycolytic pathways?

Embden-Meyerhof pathway (most common) Entner-Doudoroff pathway Pentose phosphate pathway

What distinguishes fermentation from respiration?

Endogenous electron acceptors are used (generally intermediates of the catabolic pathway that oxidize the organic energy source). Additionally, the process does not involve an ETC; ATP is only synthesized via substrate-level phosphorylation.

What three things do organisms need for metabolism?

Energy An electron source A carbon source

In what order do you write a nutritional type?

Energy source -> Electron source -> Carbon source

What is the difference between eukaryotic ETCs and bacterial/archaeal ETCs?

Eukaryote ETCs are located in the mitochondrial matrix, whereas archaea and bacteria have an ETC on the plasma membrane (perimplasmic space/outer membrane for some gram-negative bacteria). Different electron carriers are used. Branch ETCs in archaea and bacteria (electrons can enter at separate points and leave through different terminal oxidases). Archaeal and bacterial ETCs are shorter, generate less energy and pump fewer protons across the membrane.

How many protons are required to create one ATP molecule through ATP synthase?

Four

How many complexes are found in the ETC?

Four (three electron carriers and one terminal electron acceptor).

What occurs during the 3C energy-conserving phase of the Embden-Meyerhof pathway?

Fructose 1,6-biphosphate is split into two molecules of glyceraldehyde 3-phosphate. 2 NADH, 4 ATP, 2 molecules of pyruvate and some important precursor metabolites are produced via substrate level phosphorylation.

How is NADH obtained during the 3C energy-conserving phase of the Embden-Meyerhof pathway?

Glyceraldehyde 3-phosphate is oxidized and NAD+ is reduced to NADH.

How many ATP are produced in each step of glucose catabolism in eukaryotic aerobic respiration?

Glycolysis: 2 ATP TCA cycle: 0-2 ATP Oxidative phosphorylation: 28 ATP

Where does the Embden-Meyerhof pathway occur?

In the cytoplasm.

Describe the process of the redox reactions that occur in electron transport chains (in general terms).

In these structures, electrons move from an electron donor to an electron acceptor. The donor then becomes oxidized and becomes less energy rich. Simultaneously the acceptor becomes reduced and more energy rich.

Why is acetyl CoA an energy rich molecule?

It contains a high energy bond.

What is the purpose of the pyruvate dehydrogenase complex?

It oxidizes and cleaves pyruvate to form 1 CO2 molecule and one acetyl-CoA molecule.

What does the Embden-Meyerhof pathway produces?

It provides precursor metabolites, NADH and ATP.

What are the six important principles of metabolism?

Life obeys the laws of thermodynamics (requires energy for complexity). Energy is generally conserved as ATP in cells. Redox reactions are generally used in energy conservation (ATP generation). Chemical reactions in a cell are organized into pathways (products can be the substrate for the next). Each reaction in a pathway is catalyzed by an enzyme (or rybozyme). Biochemical reactions are regulated.

What is the phosphorous to oxygen ratio?

Measures the number of ATP molecules generated per oxygen molecule reduced to water as a reducing power is oxidized.

What are electron transport chains?

Membrane structures in cells that are used to perform redox reactions.

How does substrate level phosphorylation generate ATP?

Molecules with high phosphate transfer potential (higher than ATP) are generated. When these molecules are hydrolyzed, they transfer phosphate to ADP.

What are the two different types of carbon sources?

Organic carbon and CO2.

What is the terminal electron acceptor in the aerobic ETC?

Oxygen

What nutritional type are plants defined as? What about humans?

Plants -> Photolithoautotroph Humans -> Chemoorganoheterotroph

Through what mechanism do microbes generate ATP in fermentation?

Substrate level phosphorylation only.

In the ETC, which electron carrier has the lowest (most negative) standard reduction potential? What about the highest?

The 1st electron carrier. Each successive electron carrier has a higher standard reduction potential. The terminal electron acceptor will have the highest standard reduction potential.

What is a standard reduction potential? What does a more negative and a more positive value mean?

The ability for a conjugate redox pair to be reduced by an electron donor. A more negative reduction potential means that the redox pair will be a better electron donor. A more positive reduction potential means that the redox pair will be a better electron acceptor.

Why does anaerobic respiration produce less ATP?

The alternate terminal electron receptors have a less positive reduction potential than oxygen. Therefore, energy yield is directly related to the magnitude of reduction.

Define catabolism.

The breakdown of larger, more complex molecules into smaller and simpler molecules. This process releases energy.

What makes up the proton motive force?

The combined chemical and electrical potential differences across the membrane.

What is oxidative phosphorylation?

The creation of ATP from ADP and inorganic phosphate due to proton motive force.

What is a substrate?

The main input molecule of a pathway that is catabolized.

What does establishing a proton motive force result in (charge and pH)?

The mitochondrial matrix (cytoplasm in bacteria and archaea) becomes more alkaline and negative establishing a charge and pH gradient.

Describe the characteristics of the Embden-Meyerhof pathway.

The most common glycolytic pathway in microbes. This pathway can function in the presence or absence of oxygen. It is also amphibolic in some cases (gluconeogenesis).

Why is the theoretical yield of oxidative phosphorylation not usually reached?

The proton motive force is usually used to perform other cellular work. Additionally, fewer reducing power and ATP molecules are generated when precursor metabolites are being used for biosynthesis.

What is metabolism?

The sum of all chemical reactions that occur in a cell, almost all of which are enzyme catalyzed.

Define anabolism.

The synthesis of complex molecules from smaller, simpler molecules. This is powered by energy and reducing power.

What is the difference between aerobic and anaerobic respiration with regards to the ETC?

The terminal acceptor in the ETC is oxygen for aerobic respiration. Anaerobic respiration uses other molecules.

Define nutritional type.

The way in which an organism acquires the three key components to metabolism.

Where do organisms receive their energy from? (General)

Their external environment.

Why might fermentation occur in a chemoorganotrophic microbe?

They may either lack an ETC or may be repressing the components due to an environmental lack of the necessary terminal electron acceptor.

How do microbes performing fermentation generate proton motive force to do other cellular work?

They reverse the rotation of ATP synthase, pumping protons out of the cytoplasm (fueled by ATP hydrolysis).

What do microbes do to stop respiration and begin fermentation?

They stop the activity in the pyruvate dehydrogenase complex and begin using pyruvate as an endogenous electron acceptor in fermentation.

What is the function of electron carriers in the ETC?

They transfer electrons from donors (NADH and FADH2) to oxygen. The first electron carrier is reduced, which, in turn, reduces the next carrier and so on (reduction potential increases with each sequential carrier) until oxygen is reduced.

What external energy source do chemoorganotrophs use to fuel the glycolytic pathway?

They utilize a diverse range of organic molecules as energy sources (Ie. lactose, amino acids, etc.). These are then broken down into glucose, which is the necessary input for glycolysis.

How many carbons does acetyl CoA contain?

Two

What occurs during the 6C phase of the Embden-Meyerhof pathway?

Two ATP are consumed to phosphorylate a glucose molecule twice, yielding Fructose 1,6-biphosphate, which "Primes the pump."

What is the chemiosmotic hypothesis?

When the ETC establishes a protein and charge gradient.