Bioenergetics Flashcards
What is Energy?
Capacity to do work (or heat or anything that can be transformed into heat)
What are some forms that energy exists in?
heat, light, electric, mechanical, chemical, nuclear
etc.
What is Kinetic Energy?
the energy of motion, or the form of energy that is actually doing work.
Ex. Kinetic energy in heating due to movement of molecules in matter
Ex. Falling water from a waterfall has kinetic energy because of the mass of water in motion.
What is Potential Energy?
a form of stored energy, the capacity to perform work.
Ex. Water behind a dam has potential energy due to position at a higher level.
Ex. Fossil fuels (hydrocarbons like gasoline or carbon like coal) also have stored potential energy (chemical energy) which is released when they are burned in a combustion engine
What is Chemical Energy?
all chemical molecules store energy
The different molecules have various potential energy due to the arrangement of their atoms.
Potential energy due to particular arrangement of atoms in energy rich food like sugars and fats can be released by allowing certain chemical reactions to rearrange those atoms to a lower energy configuration like CO2 and H2O.
What is the First Law of Thermodynamics? The law of Energy Conservation.
the total amount of energy in the universe remains constant.
➢ Energy can be changed from one form to another.
➢ However, energy is neither created not destroyed in a closed system.
What is the Second Law of Thermodynamics? The law of energy conversion.
reducing the order of the universe, increasing its entropy (randomness - the
amount of disorder in a system).
➢ The spontaneous direction of energy flow is from forms organized (rich energy) to less organized (less energy).
➢ The amount of ‘lower quality’ energy in the universe is increasing.
➢ Energy changes are not 100% efficient.
➢ Some energy is always lost as heat.
➢ Without energy input, any organized system tends to get disorganized over time.
What is cellular metabolism?
the sum of chemical activities within a living cell.
What are metabolic pathways?
sequences of enzyme-catalyzed reactions.
What is anabolism?
refers to the various pathways in which complex molecules are synthesized
from simple substrates.
What is catabolism?
includes the pathways in which larger molecules are broken down into smaller ones
What is free energy?
(ΔG)is the amount of a system’s energy that can perform work when temperature and
pressure are uniform throughout the system, as in a living cell
What is a spontaneous reaction?
a chemical reaction which will proceed on its own, without any outside influence
What is an exergonic reaction?
an energy-releasing chemical reaction yielding products that contain less potential
energy than their reactants.
What is an endergonic reaction?
an energy-requiring chemical reaction yielding products rich in potential energy.
What is an energy coupling reaction?
the use of energy released from exergonic reactions to drive essential endergonic reaction.
What is the energy of activation?
the amount of energy that reactants must absorb before a chemical reaction will start. This represents the energy barrier that prevents molecules from breaking down spontaneously.
What is the role of enzymes?
They lower the activation energy of specific biochemical reactions
What is an enzyme?
a protein that serves as a biological catalyst
What is a catalyst?
any substance which can lower the energy of activation
What is the ATP cycle?
Continued breakdown and resynthesis of ATP
What is the active site?
the region on the surface of an enzyme where the substrate binds, and where catalysis occurs.
What are cofactors?
inorganic ions such as iron, copper or zinc that bind to certain enzymes.
What are coenzymes?
small carbon-containing molecules such as Coenzyme A (CoA), NAD, FAD or
ATP which are not permanently bound to the enzyme, and must collide with the enzyme and bind
to its active site before the catalytic reaction occurs.
What is a prosthetic group?
distinctive molecular groups that are permanently bound to their enzymes such as heme or flavin.
What regulates enzyme activity?
inhibitors, pH, temperature, etc.
What is competitive inhibition?
Inhibition of an enzyme reaction by an inhibitor molecule that resembles the normal substrate closely enough that it fits into the active site of the enzyme.
What is ATP
Adenosine triphosphate - The energy currency of the living cell.
How do living cells store energy?
in chemical bonds of lipid, starch and glycogen
What do cells use for immediate energy?
ATP. It gets used and must be replaced immediately
What is the structure of ATP?
a nucleotide consisting of 3 parts
- Adenine - a nitrogen containing organic base
- Ribose - a five carbon sugar
- three phosphate groups.
What is the function of ATP?
Exergonic reaction (hydrolysis)
ΔG = -7.6 kcal/mole.
➢ Energy liberated can drive a variety of cellular processes.
➢ When the terminal phosphate is removed from
ATP, the remaining molecule is adenosine
diphosphate (ADP).ATP + H2O ADP + Pi + ∆G (= -7.6 kcal/mol)
➢ If the phosphate group is not transferred to
another molecule, it is released as inorganic
phosphate, which is an exergonic reaction.
What are the 2 ways ATP can be generated?
Substrate-Level Phosporylation
Chemiosmosis
What is substrate-level phosporylation?
ATP is formed when a phosphate group is transferred to ADP from a phosphorylated intermediate.
What is chemiosmosis?
process by which
phosphorylation of ADP to form ATP is coupled to the transfer of electrons down an electron transport chain.
What is oxidative phosphorylation?
ATP synthesis driven by electron transfer to oxygen.
What is Photophosphorylation?
ATP synthesis driven by light
What is oxidation?
the chemical process in which a substance loses electrons
The substance that becomes oxidized gives up energy as it release electrons
What is reduction?
the chemical process in which a substance gains electrons
The substance that becomes reduced receives energy as it gains electrons
What are the most common encountered acceptor molecules in a living cell?
[NAD+ - NADH] - Nicotinamide adenine dinucleotide
[NADP+ - NADPH] - Nicotinamide adenine dinucleotide phosphate
[FAD+ - FADH2] - Flavin adenine dinucleotide
[Cytochromes (FeIII) - Cytochromes (FeII)]
[Quinone (Q) - Quinone (QH2)]
What are the two important structures (organelles)
involved in cellular energy conversions?
Chloroplast
Mitochondrion
What is an aerobe?
organism that grows or metabolizes only in the presence of molecular oxygen
Plants & Animals
What is an anaerobe?
organism that grows only in the absence of oxygen
Sulphate-reducing bacteria
What is a facultative anaerobe?
organism capable of carrying out aerobic respiration but able to switch to fermentation when oxygen is unavailable
E. Coli & Yeast
What is 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?
A type of cellular respiration where the final electron acceptor molecule is oxygen.
What is anaerobic respiration?
A type of cellular respiration where the final electron acceptor molecule is a chemical substance (inorganic molecule) in the absence of oxygen.
What is fermentation?
A type of cellular respiration where the final electron acceptor molecule is an organic molecule.
Where does cellular respiration (ATP Synthesis) take place in eukaryotic cells?
The Mitochondrion
Aerobic respiration involves which 4 stages?
Glycolysis
Formation of acetyl-CoA
Krebs Cycle
Electron Transport Chain (Chemiosmosis)
What is Glycolysis?
The multistep chemical breakdown of a 6-C glucose molecule into two, 3-C molecules of pyruvate.
The first step in cellular respiration
Where does glycolysis occur?
In the cytoplasmic fluid of the cell.
Does glycolysis require oxygen?
No
What are the starting materials of glycolysis?
glucose, ADP+Pi, NAD+, ATP and enzymes
What are the products of glycolysis?
2 pyruvate, 2 ATP and 2 NADH
How many phases and steps are involved with glycolysis?
two major phases with 10 steps, each of which is
catalyzed by a specific enzymes:
o The first phase includes endergonic reactions requiring an investment of ATP.
o The second phase includes exergonic reactions yielding
ATP and NADH.
The second step of cellular respiration (formation of Acetyl-CoA) occurs where?
The mitochondria
How does the pyruvate enter the mitochondria?
Through a channel in the outer membrane and an H+/Pyruvate symporter in the inner mitochondrial membrane
What are the steps of the formation of Acetyl-CoA?
➢ A carbon atom in pyruvate is removed and
released in CO2.
➢ A molecular of NAD+ is reduced to NADH
(total 2 NADH).
➢ A coenzyme-A (CoA) is attached
➢ An acetyl-CoA is produced.
What catalyst is involved with the formation of CoA?
pyruvate
dehydrogenase
Where does the Kreb’s Cycle occur?
In the matrix of the mitochondria
What else is the Kreb’s cycles known as?
The Citric Acid cycle
or
Tricarboxylic Acid (TCA) cycle
What is the outcome of the Kreb’s Cycle?
completes the metabolic breakdown of glucose molecules to CO2
produces 2 ATP, 6 NADH and 2 FADH2 per a glucose molecule
What are the steps of the Kreb’s Cycle?
➢ The four-carbon molecule oxaloacetate accepts two-carbon acetyl group from acetyl-CoA.
➢ The first product as citric acid.
➢ 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.
the oxidation of food molecules occurs in the presence of a group of enzymes called ___________?
dehydrogenases
What do dehydrogenases do?
They facilitate the transfer of electrons from food to a molecule and act as an energy carrier or shuttle
What is the most common dehydrogenase?
the coenzyme nicotinamide adenine dinucleotide
(NAD+, oxidized; NADH, reduced
Why is the cellular respiration considered a controlled combustion?
the potential energy of glucose is not liberated suddenly, producing only heat and light, but is slowly released in a stepwise fashion, with much of the energy being transferred to other molecules.
In the respiratory breakdown of glucose, what gets oxidized and what gets reduced?
During respiration, the dehydrogenases remove two hydrogen atoms from a substrate molecule and transfer the two electrons—but only one of the protons—to NAD+, reducing it to NADH.
The efficiency of the enzyme-catalyzed transfer of energy between food molecules and NAD+ is very high because the free energy difference between the reactant (food) and the product (NADH) is small. This means much of that energy is available to downstream reactions.
What is the primary goal of cellular respiration?
to transform the potential energy found in food molecules into ATP, the energy currency that is used for almost all energy-requiring metabolic processes.
Cellular respiration occurs in three stages, beginning with _________?
glycolysis
What is the end result of glycolysis?
glucose is converted to two molecules of pyruvate and some ATP and NADH are synthesized.
Pyruvate enters the next cycle of cellular respiration which is the ________________?
citric acid cycle
What is the result of the citric acid cycle?
The pyruvate gets completely oxidized to CO2 and some ATP and NADH are synthesized.
After the citric acid cycle, high-energy electrons of reduced coenzymes NADH and FADH2 enter the respiratory ______________________?
Electron transport chain
The last stage of cellular respiration
Both glycolysis and the citric acid cycle produce ATP through _______________ phosphorylation.
substrate-level
The final stage of cellular respiration is _______________ phosphorylation.
oxidative
What is the result of the electron transport chain?
the NADH is oxidized, the liberated electrons are transferred to oxygen producing water.
The free energy released generates a proton gradient across a membrane which then is used to synthesize more ATP
The electron transport chain happens in the final stage of cellular respiration which is called __________________?
oxidative phosphorylation
What are the membranes and compartments of the mitochondrion?
Outer mitochondrial membrane
Inner mitochondrial membrane
Matrix
Intermembrane compartment
In animal cells, glycolysis produces ATP only by substrate-level phosphorylation.
TRUE or FALSE
TRUE
Where does glycolysis occur?
The cytosol of all cells
Why is Glycolysis the most fundamental and probably most ancient of all metabolic pathways?
Glycolysis is universal, being found in all three domains of life: Archaea, Bacteria, and Eukarya
Glycolysis does not depend upon the presence of O2
Glycolysis uses soluble enzymes and occurs in the cytosol of all cells. It therefore does not require more sophisticated electron transport chains (ETCs) and internal membrane systems to function.
The diagram and summary of glycolysis
What are the 3 major components of glycolysis?
Energy investment followed by payoff
2 ATP required but 4 ATP produced
No carbon is lost
converts the glucose (a six-carbon molecule) into two molecules of three-carbon pyruvate
ATP is generated by substrate-level phosphorylation
involves the transfer of a phosphate group from a high-energy substrate molecule to ADP to produce ATP.
Pyruvate enters the mitochondrion by simple diffusion?
TRUE or FALSE
FALSE
Pyruvate crosses the outer mitochondrial membrane by diffusion but must be transported across the inner mitochondrial membrane by transport proteins.
Where does the citric acid cycle take place?
the mitochondrial matrix
What happens in the first step of the citric acid cycle?
Pyruvate (three carbons) is oxidized to an acetyl group (two carbons), which is carried to the citric acid cycle by CoA. The third carbon is released as CO2. Accepts two electrons and one proton removed in the oxidation
How many enzyme-catalyzed reactions are there in the citric acid cycle.
7 of them are soluble enzymes located in the mitochondrial matrix and 1 of them is bound to the matrix side of the inner mitochondrial membrane
What does each turn of the citric acid cycle produce?
three NADH
one FADH2 ,
one ATP,
two CO2 molecules
three H+
one CoA
What is the purpose of the citric acid cycle?
The citric acid cycle is the stage of respiration where the remaining carbon atoms that were originally in glucose at the start of glycolysis are converted into carbon dioxide.
What happens in the 3rd stage of cellular respiration?
electrons from the reduced coenzymes NADH and FADH2 are transferred through an electron transport chain
Where is the electron transport chain located?
within the mitochondrial inner membrane
How does movement through the chain happen?
Each electron transfer is exergonic , meaning that free energy is released, so movement through the chain is spontaneous . The free energy that is released is used to generate a proton gradient across the membrane, the so-called proton-motive force .
What are the 4 protein complexes in the electron transport chain?
Complex I = NADH dehydrogenase
Complex II = succinate dehydrogenase
Complex III = cytochrome complex
Complex IV = cytochrome oxidase
What drives electron transport?
the prosthetic groups and other electron carriers are organized in a very specific way: from high to low free energy. NADH has high potential energy because it contains high-energy electrons and thus can be readily oxidized.
Where does this energy go during electron transport?
The energy that is released during electron transport is used to do work, specifically the work of transporting protons across the inner mitochondrial membrane, from the matrix to the intermembrane space.
How does oxidative phosphorylation differ from substrate-level phosphorylation?
oxidative phosphorylation relies on the action of a large multiprotein complex that spans the inner mitochondrial membrane called ATP synthase
