Lecture 8-9 Flashcards
Enzymes
Enzymes:
- speed up the rates of chemical reactions without need for increase in temperature
- difference between uncatalyzed rate and enzyme-catalyzed rate = removal of phosphate group
o In cell, group of enzymes called phosphatases catalyze removal of phosphate group (reversible process)
o This is a central mechanism of intracellular communication in all cells
Without removal of phosphate takes approx. = 10 milliseconds
In aqueous environment like cell, without enzyme, phosphate removal would take over 1 trillion years to occur
o On cold planet, evolution of enzymes = critical for evolution of life
- Key players in metabolic reactions (for characteristics of life eg. Responding to stimuli)
Energy:
2 major types
Energy:
- Capacity to do work or be transferred as heat
- Exists in different forms (chemical, mechanical, electrical)
- Can be transformed from one form to another
- 2 major types of energy:
o Kinetic energy:
Energy possessed by object b/c it is in motion
Light, thermal
• Ex: flow of electrons, moving car
Movement of kinetic energy: can perform work by making objects move
o Potential energy:
Stored energy due to position or chemical structure
• Ex: dropping a rock off a cliff
Chemical
Molecules: potential energy = chemical energy, energy stored in bonds (interaction between negatively charged electrons vs positively charged nuclei)
Thermodynamics:
Thermodynamics:
- Branch of science and how it changes during chemical and physical transformations
- System = objects being studied (atom, cell etc.)
- Outside of system = surroundings
- 1st Law of thermodynamics
- 1st Law of thermodynamics
o Energy can be transformed but not created or destroyed
o Rock falling, possesses high potential energy but as it drops it loses EP and gains EK, EK is then transformed into heat, sound.
- 2nd Law of thermodynamics:
- 2nd Law of thermodynamics:
o Energy moved from being localized to being dispersed
o Entropy of system and surroundings will increase, energy and matter will always become more spread out
o Ex: heating a pan, heat is centralized to the pan but as it gets hotter, it disperses through the kitchen
o Entropy: tendency of energy to disperse (chaos)
Represented by S
Measure of disorder or randomness
Reason why machines aren’t 100 % efficient (energy loss to heat)
Free energy:
-
Free energy:
- Spontaneous process: process that can occur without constant input of energy
- Enthalpy:
- Enthalpy: head content of a system (deltaH)
o Molecule: enthalpy represents kinds of bonds existing between atoms
- Endothermic:
- Endothermic: transformations resulting in a system taking up heat from surroundings
o Products have more thermal energy than reactants
o Overall change in enthalpy: Change in products H – change in reactants H
- Exothermic: process releasing heat
- Exothermic: process releasing heat
o Products have less thermal energy than reactants = - change in H
- Sources of Energy Biological Systems transform energy from:
- Sources of Energy Biological Systems transform energy from: o Light (photosynthesis) o Catabolism (chemical breakdown) of organic and inorganic molecules
- Change in enthalpy of a reaction
- Change in enthalpy of a reaction = important to evaluate likely hood of spontaneous reaction, 2 factors:
o Reactions tend to be spontaneous if they are exothermic (products have less thermal energy than reactants)
o Reactions tend to be spontaneous when entropy of products is greater than entropy of reactants (ex: C6H1206 + 6O2->6CO2 + 6H2O spontaneous reaction because exothermic and products have greater entropy, i.e more molecules exist on one side than the other)
Free energy
portion of a systems energy that can perform work when temp is uniform through system
- Spontaneous reaction:
- Spontaneous reaction: free energy of products is less than free energy of reactants.
o Ex: diffusion of molecule across a membrane b/c of an increase in entropy
- Exergonic process:synonym of spontaneous process
- Exergonic process: synonym of spontaneous process
- Endergonic process:
- Endergonic process: a nonspontaneous reaction (change in G is positive)
o Both exergonic and endergonic require activation energy (on graph seen as initial bump) (higher to lower concentration)
sponteneity of reactions
reactions tend to be more spontaneous if products have less potential energy than reactants
Equilibrium (maximum stability, ΔG=0) is reached when
Equilibrium (maximum stability, ΔG=0) is reached when reactants
are converted to products and products are converted back to
reactants at equal rates (not necessarily when concentrations are
equal)
Life doesn’t go against second law of thermodynamics
- Living systems and surroundings appear to never increase in entropy
Life doesn’t go against second law of thermodynamics
- Living systems and surroundings appear to never increase in entropy
o due to organisms ability to maintain organized state with energy concentrated into complex molecules = this is b/c they are open systems using entropy and matter from surroundings to maintain low entropy state
o due to chemical reactions, organisms give off heat and via products of metabolism that spread out = increase in entropy or surroundings
- Why do living systems keep consuming energy:
- Why do living systems keep consuming energy:
o @ cellular level, tendency of energy to spread out = cellular components constantly break down
o Continued synthesis of proteins acts like maintenance to cell
o Living cells can never reach equilibrium (change in G = 0)
o Light from sun = highly concentrated packs of energy known as photons
o The biosphere is sustained by consumption of various forms of chemical energy produced by photosynthetic organism
Metabolism:
-
Metabolism:
- Collection of all chemical reactions present within a cell
- These reactions result in the break down of molecules that fall into 2 pathways
- These reactions result in the break down of molecules that fall into 2 pathways
o Pathways requiring energy to build molecules
o Those that release energy by breaking down molecules
- Reactions that make up metabolism are…
- Reactions that make up metabolism are grouped into pathways (one reaction at a time)
- Catabolic pathway:
- Catabolic pathway:
a. Energy is released by breakdown of complex molecules to simpler compounds
b. Free energy of final products in pathway is less than free energy of starting molecule
c. Ex: cellular respiration (energy rich molecules converted into lower energy molecules
- Anabolic pathway:
- Anabolic pathway:
a. Consumes energy to build complicated molecules from simpler ones
b. Results in the synthesis of larger more complex molecules from simpler molecules
c. Also known as biosynthetic pathways
d. These pathways require energy b/c free energy of products is greater than free energy of starting molecule
e. Ex: photosynthesis