Chapter 8 Flashcards
An Introduction to Metabolism
Metabolism
Totality of an organism’s chemical reactions. From the Greek metabole, change. _________ is an emergent property of life that arises from orderly interactions between molecules. The chemical reactions in the body’s cells that change food into energy.
Metabolic pathway
Road map of many chemical reactions, arranged as intersecting ____________. In a _____________, a specific molecule is altered in a series of defined steps, resulting in a certain product.
Catabolic pathways
Some metabolic pathways release energy by breaking down complex molecules to simpler compounds. These degradative processes are called __________________, or breakdown pathways. Opposite of Anabolic pathways.
Anabolic pathways
Consume energy to build complicated molecules from simpler ones. Opposite of catabolic pathways.
Bioenergetics
The study of how energy flows through living organisms.
Types of energies
- Kinetic energy: relative motion of objects
- Heat/thermal energy: Kinetic energy associated with the random movement of atoms or molecules. Thermal energy in transfer from one object to another = heat
- Potential energy: Energy possessed because of location/structure
- Chemical energy: Potential energy available for release in a chemical reaction.
Laws of Thermodynamics
First law: Energy of the universe is constant.
Second law: Every energy transfer/transformation increases the disorder (entropy) of the universe.
Free energy
The portion of a system’s energy that can perform work when the temperature and pressure are uniform throughout the system.
Change in Free Energy
Delta G (change of free energy), can be calculated for a chem. reactions: Delta G = Delta H- T Delta S.
Delta: The change in _____
H: enthalpy = total energy
S: Entropy = measure of disorder
T: Temp. in Kelvin.
In a spontaneous reaction, Delta G must have a ___________ value (decrease in ____________)
negative; delta H
At equilibrium, Delta G = 0 (CELL IS DEAD)
Exergonic vs Endergonic Reactions
Exergonic: Proceeds with a net release of free energy Delta G is negative.
Endergonic: Absorbs free energy from its surroundings. Delta G is positive
ATP power
Adenosine triphosphate. Contains the sugar ribose, the nitrogenous base adenine and a chain of 3 phosphate groups. Loss of a phosphate group = energy.
Three kinds of cellular work
- Chemical: the physical work that is carried out within a cell, due to the energy derived from chemicals
- Transport: the act or the means by which molecules, ions, or substrates are moved across a biological membrane, such as the plasma membrane
- Mechanical: contraction of a muscle
Transport and mechanical work in the cell are nearly always powered by the hydrolysis of ATP.
Energy Coupling
Use of an exergonic process to drive an endergonic one.
How ATP performs work
When ATP is hydrolyzed in a test tube, the release of free energy merely heats the surrounding water. In an organism, this same generation of heat can sometimes be beneficial.
Metabolic Disequilibrium
Cells die at equilibrium.
Regeneration of ATP
The addition of phosphate to ADP. The free energy required to phosphorylate ADP comes from exergonic breakdown reactions (catabolism) in the cell.
The Life of an Enzyme
1-2 days
Catalyst
A chemical agent that speeds up a reaction without being consumed by the reaction.
Enzymes
A macromolecule that acts as a catalyst.
Activation Energy (E_A)
Energy required to contort the reactant molecules so the bonds can break
Substrate
The reactant an enzyme act on. Enzyme binds to its substrate.
Active Site
Typically a pocket or groove on the surface of the enzyme where catalysis occurs. A restricted region of the enzyme molecule actually binds to the substrate.
How Catalysis occurs in the enzyme’s active site
Products -> active site. Active site lowers E_A. Substrates are converted to products. Products released. Active site is available for new substrates.
Effect of Environment on Enzyme Activity
Temperature and pH. Can also be affected by chemicals that specifically influence that enzyme.
Regulation of Enzyme activity helps control metabolism
Enzymes help break down macromolecules like proteins, fats and carbohydrates.
Allosteric Regulation of Enzymes
Term used to describe any case in which a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site. May result in either inhibition or activation. Most enzymes known to be allosterically regulated are constructed from two or more subunits, each composed of a polypeptide chain with its own active site.
Allosteric Activation
Allosteric activator stabilizes the active form of an enzyme. Good image in notes.
Allosteric inhibition
Allosteric inhibitor stabilizes inactive form of an enzyme. Good image in notes.
Allosteric: neither
Inactive form oscillates with the active form when the active form is not stabilized by substrate.
Cooperativity
This mechanism amplifies the response of enzymes to substrates. Is considered allosteric regulation because even though substrate is binding to an active site, its binding affects catalysis in another active site.
Cooperativity is a phenomenon that occurs when a substrate acts as an allosteric activator. In cooperativity, the substrate binds to one active site, which increases the activity of the other active sites. This is considered allosteric regulation because the substrate affects active sites far from its binding site
Feedback Inhibition
A metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway.
a form of negative feedback in which the final product of a series of reactions inhibits an enzyme from an earlier step in the metabolic pathway that produced it.
Specific localization of enzymes within the cell
The cell is not just a bag of chemicals with thousands of different kinds of enzymes and substrates in a random mix. Compartmentalized and cellular structures help bring order to metabolic pathways.
Anabolism
the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy; constructive metabolism.
Delta G of ATP
-7.3 kcal/mol
ATP Energy
When an ATP is broken down via hydrolysis, it releases energy (heat).
Sunlight Energy
Nuclear fusion in the sun. Photosynthesis.
Gradient Energy
Allow cells to control the direction ions move across membranes. In mitochondria and chloroplasts, proton gradients generate a chemiosmotic potential used to synthesize ATP, and the sodium-potassium gradient helps neural synapses quickly transmit information.
When allowed to move with gradient, generate energy!
Reduced molecule energy
When a molecule gains an electron, it gains energy.
Highly ordered system
More unstable
Add a -OH is called:
Hydroxylation
Add a CH4 is called:
Methylation
Sodium/Potassium pump
3 sodium per 2 potassium. Sodiums exit the cell, potassium enter.
Cofactors.
An inorganic enzyme helper of enzymatic activity.
Coenzyme
An organic enzyme helper of enzymatic activity.
