what happens when molecules react?
they collide and exchange parts, their atoms and bonds are rearranged. Reactants are rearranged to form products. Reactant and product molecules store potential energy in the arrangements of their atoms and bonds
involve changes in bonding and changes in energy
energy is released to the surroundings as the reactants are rearranged to form products. The potential energy of the molecules drops so products have less potential energy than the reactants. "downhill" occur spontaneously, no energy easier than endergonic
the product molecules have more potential energy than the reactants. The reactants must absorb energy for this reaction to occur. "uphill"- absorb energy from surroundings
how do cells undergo endergonic reactions?
energy coupling-- obtaining chemical energy from an exergonic reaction and then using the energy to drive an endergonic reaction. In an exergonic reaction, ATP becomes ADP as a phosphate is removed; a reactant molecule acquires the phosphate from ATP and gains energy. Now the reaction can proceed.
In cells, what is usually the immediate source of energy for an endergonic reaction?
The hydrolysis of ATP provides the energy needed for an endergonic reaction.
What is the fate of the phosphate group that is removed when ATP is converted to ADP?
By acquiring the phosphate group the reactant acquires energy.
adenosine triphosphate, an organic molecule that acts as the main energy source for cell processes; composed of a nitrogenous base, a ribose, and three phosphate groups
how energy is stored and released during cellular respiration
glucose releases energy. This energy is stored when a phosphate group is added to ADP , forming ATP (adenosine triphosphate). ATP releases energy when the covalent bond between phosphate groups breaks during hydrolysis. This energy is used to drive other biochemical reactions.
where do stages of cellular repiration take place?
glycolysis in cytosol, Krebs and oxidative phosphorylation in mitochondria
electrons are transferred from glucose to coenzymes such as NAD+ and finally to oxygen; the energy released by this relocation of electrons is used to make ATP. Carbon dioxide and water are given off as byproducts
series of steps in which a glucose molecule is broken down into two molecules of pyruvate. As the chemical bonds in glucose are broken, electrons (and hydrogen ions) are picked up by NAD+, forming NADH. Glucose is oxidized and NAD+ is reduced. A net output of two ATP molecules and 2 NADH are also produced. Most of the energy released by the breakdown of glucose is carried by the electrons attached to NADH.
citric acid cycle
The pyruvate molecules are modified as they enter the mitochondrion, releasing carbon dioxide. The altered molecules enter a series of reactions called the citric acid cycle. More carbon dioxide is released as the citric acid cycle completes the oxidation of glucose. Two ATPs are formed per glucose, but most of the energy released by the oxidation of glucose is carried by NADH and FADH2.
Almost all of the ATP produced by cellular respiration is banked in the final phase— oxidative phosphorylation. The NADH and FADH2 molecules produced in glycolysis and the citric acid cycle donate their electrons to the electron transport chain. At the end of the chain, oxygen exerts a strong pull on the electrons, and combines with them and hydrogen ions (protons) to form water. The electron transport chain converts chemical energy of moving electrons to a form that can be used to drive oxidative phosphorylation, which produces about 34 ATP molecules for each glucose molecule consumed.
a chemical reaction in which electrons are lost from one molecule (oxidation) and added to another (reduction). ex: NaCl the atoms went through oxidation (sodium- cation) and reduction (chlourine-anion) to become cation and anion.
types of redox reactions
covalent bond- shift positions ex: 2 reactants of methane combustion (CH4 and O2) have electrons at equal distance from atoms' nuclei: nonpolar
ionic bond- electrons can be transferred completely from one molecule/ atom to another ex: products CO2 and H2O share electrons unequally: polar (O holds electrons more so C has been oxidized and H also O reduced)
atomic nuclei of exergonic
because atomic nuclei of products holds electrons closer than reactant it has lower potential energy and tends to release free energy spontaneously
Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?
anion and cation
Which of the following statements is true of the bonds in a water molecule?
Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero. The oxygen and hydrogen atoms in water have partial charges, but the molecule has a net charge of zero.
H proton in redox reactions
A hydrogen atom (proton, or H+) is often transferred to the atom that gains an electron.
2H2 + O2 → 2H2 O + energy
Which molecule is oxidized and what kind of bond is formed?
hydrogen is oxidized and water has polar bond
In glycolysis, ATP molecules are produced by _____.
substrate level phosphorylation (A phosphate group is transferred from glyceraldehyde phosphate to ADP.)
In glycolysis, what starts the process of glucose oxidation?
ATP for energy
how does fermentation start after glycolysis?
By oxidizing the NADH produced in glycolysis, fermentation regenerates NAD+, which can take part in glycolysis once again to produce more ATP. The net energy gain in fermentation is 2 ATP molecules per molecule of glucose. Fermentation complements glycolysis and makes it possible for ATP to be continually produced in the absence of oxygen.
in yeast, results in the production of ethanol and carbon dioxide.
lactic acid fermentation
occurs in muscle, results in the production of lactate (lactic acid)
why oxygen or fermentation needed
Glycolysis produces NADH, ATP, and pyruvate (pyruvic acid). If oxygen is not present, NADH cannot be oxidized in the electron transport chain. Without fermentation, the cell would run out of NAD+, bringing glycolysis to a halt.
how does alcahol fermentation make ethanol
the pyruvate (pyruvic acid) from glycolysis loses one carbon in the form of carbon dioxide and the product is then reduced to ethanol by NADH. With the formation of ethanol, NADH is oxidized and becomes NAD+
In fermentation _____ is reduced and _____ is oxidized.
relationship between glycolysis and lactic acid fermentation
the pyruvate (pyruvic acid) from glycolysis is reduced to lactate (lactic acid) by NADH. With the formation of lactate (lactic acid), NADH is oxidized and becomes NAD+.
all the chemical reactions that occur in living cells
perform cellular work like pumping ions, transporting vesicles within the cell and making macromolecules
after pyruvate is made
if oxygen is present pyruvate is transported into the mitochondrial matrix where it is stripped of a carbon atom (CO2 released) and combined with the molecule coenzyme A to make acetyl CoA (has 2 remaining carbon atoms of pyruvate). 2 NADH also produced from reduction NAD+. pyruvate (a product of glycolysis) is oxidized to acetyl CoA, with the reduction of NAD+ to NADH and the release of one molecule of CO2.
remaining carbon atoms from acetyl CoA incorporated into molecules of 2 CO2/ pyruvate carbon dioxide. Produces 2 molecules of ATP and series of electron carriers (6 NADH and 2 FAdH2) that transport energy from glucose to electron transport chain. 1 molecule ATP for every pyruvate & 2 for every glucose
The 2-carbon fragment of acetyl CoA attaches to the 4-carbon molecule oxaloacetate in the first reaction of the cycle. This forms citrate. In a series of steps, bonds break and reform. Two carbon atoms are released, one at a time, in molecules of carbon dioxide.
electron transport chain
uses the donated energy of the electron carriers to pump protons into the intermembrane space and form a concentration gradient of protons across the membranes. an array of molecules— mostly proteins— built into the inner membrane of the mitochondrion. NADH gives up its high-energy electrons to the first complex in the electron transport chain. The electrons move from one member of the chain to the next, giving up their energy as they are pulled from NADH toward highly electronegative oxygen. The energy given up by the flow of electrons is used to pump hydrogen ions from the mitochondrial matrix into the intermembrane space. Oxygen captures the electrons in the very last step in electron transport. The last complex adds a pair of electrons to an oxygen atom and two hydrogen ions, forming water.
membrane protein that protons flow through down their gradient. It uses the energy released from the proton flow to produce ATP. from this process is produced around 26 ATP so total of cellular respiration about 30 molecules
energy investment to energy payoff
use 2 ATP for glucose to fructose bisphosphate then to G3P (glyceraldehyde 3 phosphate) into pyruvate (2 NaDPH and 4 ATP)
Two molecules are formed as pyruvate is converted to acetyl CoA, and four molecules are formed during the Krebs cycle.
where does the potential energy of ATP derive from
The three phosphate groups in an ATP molecule carry negative charges that strongly repel each other and give ATP a large amount of potential energy
ATP in citric acid cyce produced by
substrate level phosphorylation GDP to ATP
For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.
In cellular respiration, most ATP molecules are produced by _____.
oxidative phosphorylation (electron transport)
The proximate (immediate) source of energy for oxidative phosphorylation is _____.
kinetic energy that is released as hydrogen ions diffuse down their concentration gradient
input and output citric acid cycle
inputs: ADP+ NAD+ acetyl COA output: ATP NaDH coenzyme A CO2 FAdH2
input and output oxidative phosphorylation
In oxidative phosphorylation, the NADH and FADH2 produced by the first three stages of cellular respiration are oxidized in the electron transport chain, reducing O2 to water and recycling NAD+ and FAD back to the first three stages of cellular respiration. The electron transport reactions supply the energy to drive most of a cell's ATP production. (input: 02 FADH2 ADP NADH output: NAD+ H2O ATP)
role of O2 in cellular respiration
Without O2, mitochondria are unable to oxidize the NADH and FADH2 produced in the first three steps of cellular respiration, and thus cannot make any ATP via oxidative phosphorylation. In addition, without O2 the mitochondria cannot oxidize the NADH and FADH2 back to NAD+ and FAD, which are needed as inputs to the first three stages of cellular respiration.
Which statement best explains why more ATP is made per molecule of NADH than per molecule of FADH2?
(more protons pumped by NADH) Electrons derived from the oxidation of FADH2 enter the electron transport chain at Complex II, farther down the chain than electrons from NADH (which enter at Complex I). This results in fewer H+ ions being pumped across the membrane for FADH2 compared to NADH, as this diagram shows. Thus, more ATP can be produced per NADH than FADH2.
Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops.
In the absence of oxygen, electron transport stops. NADH is no longer converted to NAD+, which is needed for the first three stages of cellular respiration.
Which statement correctly describes how this increased demand would lead to an increased rate of ATP production?
ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production.
During strenuous exercise, anaerobic conditions can result if the cardiovascular system cannot supply oxygen fast enough to meet the demands of muscle cells. Assume that a muscle cell's demand for ATP under anaerobic conditions remains the same as it was under aerobic conditions.
glucose use increase a lot
Why are NASA scientists researching plants as a life support system for long-term space flight?
packaged food takes up much space
The electrons stripped from glucose in cellular respiration end up in which compound?
eventually all go to O2 to become H2O
Which one of the following statements about the chemiosmotic synthesis of ATP is correct?
chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane
Which one of the following statements about the redox reactions of the electron transport chain is correct?
The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane.
In most cells, not all of the carbon compounds that participate in glycolysis and the citric acid cycle are converted to carbon dioxide by cellular respiration. What happens to the carbon in these compounds that does not end up as CO2?
The carbon compounds are removed from these processes to serve as building blocks for other complex molecules.
Cells do not catabolize carbon dioxide because
CO2 is already completely oxidized
When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?
pH of matrix increases
In mitochondria, exergonic redox reactions
provide the energy that establishes the proton gradient.
What is the reducing agent in the following reaction? pyruvate + NADH + H+ --> lactate + NAD+