Chapter 8- bioenergetics Flashcards
Exam 2
What is the reactions of energy extraction and energy use called?
Metabolism
How are molecules degraded or synthesized stepwise in a series of linked reactions?
Through metabolic pathways
What is the energy currency of life?
ATP
How can ATP be formed?
By the oxidation of carbon fuels
True/False: Metabolic pathways are not regulated
False
They are highly regulated
What does metabolism do?
Convert one biomolecule into another required molecule
What do catabolic reactions do?
Convert energy from fuels into useful cellular energy (ATP or ion gradients)
Breaks things down
What do anabolic reactions do?
They require energy to generate complex structures from simple precursors
(polysaccharides, phospholipids, DNA)
What are amphibolic pathways?
They are metabolic pathways that can function anabolically (build up) or catabollically (break down)
What two criteria must be met in order to construct a metabolic pathway?
Individual reactions must be specific
(facilitated by enzymes to yield only a specific product)
The overall pathway must be thermodynamically favorable
What determines if a reaction is thermodynamically favorable or not?
If the free energy is negative = favorable
If the free energy is positive = not favorable
What is the first law of thermodynamics?
Energy cannot be created or destroyed
only be converted from one form to another but total energy of system remains constant
What is the second law of thermodynamics?
Entropy of any isolated system always increases
disorder must increase when transforming energy
What is the free energy equation?
What is the equation for standard free-energy change?
What determines the speed of the reaction?
Enzymes
What does the change in free energy indicate?
The direction in which a reaction will proceed
Do you need to add energy for a spontaneous reaction to occur?
no
What will the change of free energy be for spontaneous reactions?
It will be negative since it is exergonic (giving off energy)
How would a reaction happen if it requires energy?
If they are coupled to energy releasing reactions
they have a positive change of free energy and are endergonic
How are endergonic reactions influenced?
Allosteric effectors, removing product and using it as a substrate for a subsequent reaction in the pathway
____ ____ changes of individual enzymatic reactions are additive.
Free energy
What provides energy to do work in the cells?
Hydrolysis of ATP to ADP
______ _______ requires O2 to generate ATP.
Oxidative phosphorylation
What are the bonds between phosphate groups in ATP?
Phosphoanhydride bonds
True/False: ADP and Pi are more stable than ATP
True
This is why ATP has such a high energy bond
What does hydrolysis of ATP decrease?
Electrostatic repulsion (the phosphates and oxygens all have negative charges that push away from each other so when the phosphoanhydride bond is cleaved, a lot of potential energy is released)
Why is a free phosphate group more stable than it is in ATP?
Resonance (the ability of charges to move around the molecule)
What happens to entropy when ADP is phosphorylated to ATP?
Entropy is decreased (there is a loss in resonance-stablized phosphate ion)
True/False: The hydrolysis of ATP is exergonic
True it releases a lot of energy due to the breaking of an unstable phosphoanhydride bond
What drives highly unfavorable reactions forward?
The high-energy bonds of ATP
How is energy from ATP transfered to reactions?
Through phosphorylation by kinases (OH of one group attaches to the P of the phosphate)
What does the standard free energy of ATP hydrolysis depend upon?
Mg2+ in order to stabilize the negative charges on the oxygens in phosphate groups
How do unfavorable endergonic reactions proceed in metabolic pathways?
They are coupled with favorable exergonic reactions such as hydrolysis of ATP
What is a high energy bond?
Any bond that can be hydrolyzed to release more or the same amount of energy as ATP
What are 4 different activated intermediates used to facilitate energy transfers in biochemical reactions?
GTP-protein synthesis
CTP-lipid synthesis
UTP-combining sugars
ATP-transport and mechanical work
How is ATP converted back to ADP?
Oxidative phosphorylation by adenylate kinase
ADP+ADP->ATP+AMP
True/False: All high energy bonds are stable.
False they are all unstable
What does generation of reduced enzymes do?
Provide energy for bodily processes through fuel oxidation
What are 3 reduced enzymes used in fuel oxidation?
NADH
NADPH
FADH2
What is used to generate ATP through aerobic glycolysis?
Carbohydrates
What are used to generate ATP in oxidative phosphorylation?
NADH and FADH2
What is fuel oxidation?
Means of transferring energy from chemical bonds to cellular processes
What does cellular respiration do?
Transforms energy from chemical bonds of fuels into the reduction state of electron accepting coenzymes (NAD+ and FAD)
What do reduced coenzymes do?
They transfer electrons to O2 in the electron transport chain
(Energy rich)
What happens during oxidation?
Electrons are lost
What happens during reduction?
Electrons are gained
What is oxidation of a substance always accompanied with?
The reduction of another substance
If a carbon is reduced, what happens when it is oxidized?
The more it is reduced the more free energy is released upon oxidation
Why are fats a more efficient fuel source than glucose?
Fats are more reduced (Many CHs while glucose has many COs)
Where do fuels donate electrons when being oxidized?
To the NAD+ and FAD
What is NAD+ derived from?
Niacin (Vitamin B3)
What is a coenzyme?
Non protein substance that takes part in an enzymatic reaction (regenerated at the end of the reaction)
How many electrons does NAD+ accept? How many protons?
2 electrons and 1 proton
What is NADH used for?
A source of electrons for ATP synthesis
What is FAD derived from?
Riboflavin (B2)
How many hydrogen atoms does FAD Accept?
2 Hydrogen atoms
What is contained in Coenzyme A?
Vitamin B5 and sulfhydral group
What kind of linkages form between carboxylic acids and sulfhydral groups?
Thioester linkages
What does coenzyme A do?
Acts as a carrier of acetyl groups
What is the metabolically active form of carboxylic acid?
Acyl-CoA
What does having a more negative reduction potential mean?
The greater the tendency of the reductant member to lose electrons
What does a more positive reduction potential mean?
The stronger the oxidant is more willing to accept electrons
What are the stages of extracting energy from food?
Stage 1: large molecules in food are broken down into smaller units
Stage 2: small molecules are converted into acetyl-CoA
Stage 3: ATP is produced from oxidation of acetyl-CoA/ NADH and FADH2 are oxidized and transfer electrons to O2
