Bioenergetics (Wei) Flashcards
What is energy?
capacity to do work; or heat or anything that can be transformed into heat
What is the first law of thermodynamics?
the total amount of energy in the universe remains constant; energy is neither created or destroyed
what is the second law of thermodynamics?
as energy is transferred or transformed, more and more of it is wasted and there is a natural tendency of any isolated system to degenerate into a more disordered state.
Describe metabolic pathways and compare anabolism and catabolism.
Sequences of enzyme-catalyzed reactions
Anabolism refers to the various pathways in which complex molecules are synthesized from simple substrates, catabolism is larger molecules broken down
What is a spontaneous reaction?
chemical reaction that proceeds on its own without any outside influence
Describe an energy coupling reaction.
the use of energy released from exergonic reactions to drive an essential endergonic reaction
Describe the structure and function of ATP.
Made up of Adenine, Ribose, and three phosphate groups
Hydrolysis of ATP provides energy for cellular functions by donating a phosphate group
What is the definition of cellular respiration?
the process by which cells generate ATP through a series of redox reactions; electrons are removed from various molecules such as glucose and passed through intermediate electron carriers to a final electron acceptor.
What is aerobic respiration and what are its four stages?
When this acceptor molecule is oxygen, the process is called aerobic respiration.
(1) Glycolysis
(2) Formation of acetyl-CoA
(3) Krebs cycle
(4) The electron transport chain/chemiosmosis
Describe glycolysis.
the multistep chemical breakdown of a 6-C glucose molecule into two, 3-C molecules of pyruvate
The first stage of cellular respiration in all organisms.
Occurs in the cytoplasmic fluid–does not require oxygen.
Starting materials: glucose, ADP+Pi, NAD+, ATP and enzymes; Produces 2 pyruvate, 2 ATP and 2 NADH.
Consists of a series of reactions divided into two major phases with 10 steps, each of which is catalyzed by a specific enzymes:
the first phase includes endergonic reactions requiring an investment of ATP.
The second phase includes exergonic reactions yielding ATP and NADH
Describe acetyl-CoA formation.
(1) Occurs in mitochondria
(2) A carbon atom in pyruvate is removed and released in CO2 .
(3) A molecular of NAD+ is reduced to NADH (total 2 NADH).
(4) A coenzyme-A (CoA) is attached
(5) An acetyl-CoA is produced.
(6) The reaction is catalyzed by pyruvate dehydrogenase
Describe Kreb’s cycle.
(citric acid cycle; tricarboxylic acid cycle)
Occurs in the matrix of mitochondria.
The four-carbon molecule oxaloacetate accepts two-carbon acetyl group from acetyl-CoA.
The first product as citric acid (6 carbon sugar)
Includes eight steps each of which is catalyzed by a specific enzyme.
The cycle completely disassembles acetyl-CoA, stripping away its electrons and producing CO2 .
At the end of each cycle, the oxaloacetate has been regenerated.
High energy extraction steps produce 2 ATP, 6 NADH and 2 FADH2 per a glucose molecule.
Explain electron transport chains.
a sequence of electron-carrier molecules that shuttle electrons during redox reactions, with the release of energy.
NADH and FADH2 are the primary electron donors
O2 is the final electron acceptor
As redox occurs, the electron carriers use some of the energy released as electrons pass down the electron transport chain to actively transport proton (hydrogen ion, H+) from one side of the inner mitochondrial membrane to the other, which results in an H+ gradient.
Describe chemiosmosis in cellular respiration
the production of ATP using the energy of proton gradient across membranes to phosphorylate ADP; it powers the most ATP synthesis in cells.
Diffusion of protons from the intermembrane space through the inner mitochondrial membrane to the matrix is through specific channels formed by an enzyme complex, ATP synthase.
Diffusion of the protons down their gradient, through the ATP synthase complex, is an exergonic process.
This exergonic process drives the endergonic reaction, in which ATP is produced by phosphorylating ADP (oxidative phosphorylation).
What are the functions of fermentation?
It is an inefficient way to use fuel.
It allows organisms to survive without oxygen
It removes toxic excess NADH in the cytosol.
It replenishes the supply of NAD+.
What is a photosystem?
a light-harvesting unit of a chloroplast thylakoid membrane, containing a reaction center plus antenna complexes
The function of a photosystem is to trap photons of light and use the energy to oxidize a reaction center chlorophyll and enable the electron being transferred to the primary electron acceptor.
What are the two types of photosystems?
Photosystem I (PS I), also called P700 because the reaction center associated with PS I has an absorption peak at 700 nm (red light). Photosystem II (PS II), called P680 made up of a reaction center with an absorption peak of about 680 nm (a more orange shade of red).
What is electron transport?
The synthesis of ATP, and NADPH by the concerted action of photosystems II and I via noncyclic electron transport
- a series of electron carrier molecules in the thylakoid membrane
- carries the flow of electrons extracted from H2O to NADP+.
Describe electron transport in the photosystem.
When PS II (P680) is activated by absorbing photons, it (chlorophyll a) gives energized electrons to a primary electron acceptor, which are passed along the electron transport chain and eventually donated to PS I.
The final electron acceptor is NADP+, (not O2 ), forming NADPH
The synthesis of ATP is driven by _____________ (____________)
chemiosmosis (photophosphorylation)
Describe chemiosmosis in photosynthesis
the production of ATP using the energy of H+ gradient across membranes to phosphorylate ADP, powers most ATP synthesis in cells.
Because the synthesis of ATP is coupled to the transport of electrons that have been energized by photons of light, the process is called photophosphorylation
ATP is released into the _____ after chemiosmosis in photosynthesis
ATP is released into stroma
What is noncyclic electron flow and what is cyclic electron flow?
Noncyclic electron flow involves both Photosystems I & II and produces ATP and NADPH.
Cyclic electron flow uses only Photosystem I and produces only ATP
What is carbon fixation?
the second of two stages of photosynthesis; the Calvin cycle is a cyclic series of chemical reactions that occur in the stroma of a chloroplast, using the carbon in CO2 and the ATP and NADHP produced by the light reactions to make the energy-rich sugar molecular glyceraldehyde 3-phosphate (G3P).
