Week 5
Bioenergetics ppt
Basically, Applied thermodynamics.
Cells have 4 essentials:
molecular building blocks
Chemical catalysts (enzymes)
Information to guide activities (DNA/RNA)
Energy to drive reactions and processes essential for life
All living systems require an ongoing supply of energy
Energy is defined as the capacity to cause specific chemical or physical changes (work)
Categories of Change that Require Energy: Synthetic work, Mechanical work, Concentration work, Electrical work, and generation of Heat
Synthetic work
Is the formation of new chemical bonds and the synthesis of new molecules
Biosynthesis is required for growth and maintenance of cells and cellular structures
Process uses energy to create energy -rich organic molecules and incorporates them into macromolecules
Mechanical work
Uses energy to cause a physical Change in the position or orientation of a cell or some part of it
Muscle contraction
Movement of chromosomes
Movement f organelles
Translation of a ribosome along a strand of mRNA
The movement of a cell from one place to another
Flagella
Moves a cell
Sperm cells
Bacteria
Cilia
Move substance over the surface of the cell
Respiratory system moving Mucous
Concentration work
Before we can describe it, we have to discuss the movement of substances form one side of a barrier to another
Like a lake (high concentration) going through a dam to the river (lower concentration)
A passive process. Does not require energy
To move it the other way, you need a high-powered energy
In biological systems, substances occur at the molecular level
The natural tendency of ions and molecules is to disperse evenly through the environment
Diffusion: a passive biological process in which ions and molecules disperse from an area of high concentration to an area of low concentration
Will continue until the ions and molecules are evenly distributes through the environment
Cells must concentrate ions, molecule, and enzymes on one side of a plasma membrane
The process that allows cells to concentrate substances within a cell or organelle is called Active Transport
Opposes Diffusion
Differs from diffusion in 2 ways
Requires energy
Movement of ions and molecules is going against the gradient
Used to create and maintain conditions required for electrical work
These conditions result by pumping specific ions into the cell while pumping other ions out of the cell
Electric work
The pumping of ions creates both concentration and electrical differences on both sides of a membrane
Creates an electrical gradient
To perform electric work, channels open in the membrane allowing ions to travel down the electrochemical gradient
Na+ and K+ travel from high to low concentration, but they are also attracted by electrical charge
This is how nerve impulses work
The movement of ions down the electrochemical gradient allows an electrical impulse to travel along a membrane
Every cellular membrane has a characteristic electrical potential
Generation of Heat
Living organisms do not use heat as a form of energy
However, producing heat is a major use of energy in homeotherms
Homeotherms are animals that regulate their body temperature independent of the environment
Organisms can be Phototrophs or Chemotrophs depending on source of energy
Autotrophs or heterotrophs depending on source of carbon
Chemoheterotrophs ingest ad use chemical compounds for energy
Oxidation-reduction reactions
Oxidation is the removal of one or more electrons from an atom or molecule
When an electron is removed a hydrogen atom is usually removed as well
Oxidation reactions are exothermic (they release energy)
Reduction is the addition of one or more electrons to an atom or meloecule
A hydrogen atom is usually aed as well
Reduction reactions are endothermic (they require an input of energy)
Glucose Oxidation:
C6H12O6 + 60 2 → CO2 + 6H2O + energy
Carbon Dioxide reduction
Opposite of glucose oxidation
What plants do
Energy + 6CO2 +6H2O. → C6H12O6 +60 2
Energy is governed by the principles of thermodynamics
Thermodynamics concerns the laws governing energy transactions that accompany most physical and chemical processes.
Bioenergetics (applied thermodynamics) applies principles of thermodynamics to the biological world
Organisms are open systems, capable of uptake and release of energy
Heat and Work:
the exchange of energy between a system and its surroundings occurs as either heat or work
Work is the use of energy to drive a process other than heat flow
Quantify energy change: 1 kcal= 1000 calories
the units for quantifying the energy changes during chemical reactions are calories (cal)
Calorie: the amount of energy required to raise one gram of water by one degree centigrade at one atmosphere of pressure
Thermodynamics:
1st Law: The law of conversion of energy:
energy cannot be created nor destroyed
Ex. On earth, the sun provides most energy
Conservation of energy in Biological Systems
in bio systems the energy that leaves a system must equal that high entered is plus the amount remaining (stores) int he systems
Total energy stored within a system is called internal energy, or E
Delta E is the change in internal energy that occurs during some process
2nd law of Thermodynamics:
In every physical or chemical change, the universe tends toward greater disorder or randomness (entropy)
Chemical reactions have directionality, and we can predict the direction a reaction will proceed under specific conditions, how much energy will be released, and how changes in conditions will affect it
A thermodynamic ally spontaneous reaction is one that is favorable
Equilibrium Reactions:
In a chemical reaction, chemical equilibrium is the tat in which both term reactants and products are present in concentrations which have no future tendency to change with time, so that there is no observable change in the properties of the totem
At equilibrium there is no net change in the conversations o reactance o products. This reaction will remain at equilibrium if conditions don’t change
The chemical reactions will always do their best in your cells to try and maintain equilibrium
It will always shift one way or another depending on what the system needs to maintain equilibrium
When you hyperventilate, you need the paper bag to breathe into, because your CO2 is getting too low
The Equilibrium constant is a measure of directionality
The equilibrium constant Keq, is the ratio of product concentration to reactant concentration at equilibrium
Can be calculated mathematically
If you know the equilibrium constant for a reaction, you can tell whether a particular mixture of products and reactants is in equilibrium
The tendency toward equilibrium provides the driving force for every chemical reaction
The concentration ration is less than Keq means that the reactions will proceed to the right to generate more product
A concentration ratio greater than Keq means that the reaction will proceed to the left to generate more reactants
Free Energy
Free energy is the amount of energy in a system that can do useful work
Measure of the spontaneity for a system
The free energy change (DeltaG’) is dependent of the free energies of the products and reactant
Change DeltaG:
In ENDERGONIC reactions the products have more energy than the reactants
Positive DeltaG
In EXERGONIC reactions, the reactants have more energy than the products
Negative DeltaG
In an exergonic reaction, energy is released to the surrounding. The bonds being formed are stronger than the bonds being broken
In an Endergonic reaction, energy is absorbed form the surroundings. The bonds being formed are weaker than the bonds being broken.
Life in the Steady State: reactions that move towards equilibrium without ever getting there
Never get to equilibrium because the molecules are always shifting
Forward and reverse reactions are at the same rate
No net flow
Living cells are characterized by continuous reactions an maintain themselves in states far from equilibrium
Standard conditions
standard pH= 7.0 (neutral) therefore the concentration of H+ and OH- is equal
In a beaker of distilled water, each water molecule exists as H2O, but many of the molecules dislocate into OH- and H+
Concentration of each remains equal though
OH- = Strong Base (alkaline solutions) raises pH
H+ = Strong Acid (acidic solutions) lowers pH
Adding chemicals that change the concentrations of OH- or H+ will change he pH of the solution if they are no longer equal
PH scale is 0-14
[H+] scale = 10^0 - 10^-14
[OH-] scale = 10^-14 - 10^0
Too acidic or too alkaline solutions will both damage tissues
Examples of household substances on pH scale 0-14:
Battery acid
Stomach acid
Lemon juice
Soda
Tomato juice
Black coffee
Urine (average)
Pure water
Seawater
Baking soda
Antacid tablets (Tums)
Soap
Ammonia
Bleach
Drain Cleaner
Enzymes ppt
All chemical bonds contain stored energy
During a chemical reaction, stored energy is released due to the breaking of these bonds
The amount of energy released during a chemical reaction is related to the number of bonds broken during the event
In order to break a chemical bond, energy has to be added to the system
The amount of energy required depends on the type of bonds being broken
It takes energy (like a spark or flame) to break the triple bond in a molecule of Acetylene, which results in the release of a huge amount of energy
The amount of energy needed to break the bond is called “The activation energy” (Ea)
The amount of energy release from a broken bond is more than what was needed to cause the bond to break
Every chemical reaction has a specific (Ea)
Outer Phosphoanhydride bond is a high-energy bond, but when ATP breaks that bond it become ADP. When the next Phosphoanhydride bond is broken, ADP becomes AMP. When the Phosphate groups are broken from the molecule, AMP becomes just Adenosine
When Ea is added to reactants, the energy contain by these molecules is elevated about that of their resting state.
The higher state of energy is called the transition state
Metastable State:
At normal cellular temperatures, the number of biologically important chemical reactions is optimally low
This is because reactant is very stable
Overcoming the activation energy barrier:
The activation energy requirement is a barrier that must be overcome if desirable reactions are to proceed at reasonable rates
The only way a reaction involve int metastable reactants would proceed at an appropriate rate would be to increase the energy, or to lower the Ea
A fever will increase the amount of energy in the reactants of biological reactions
A Chemical CATALYST lowers the activation energy requirements of reactants, and will increase the rate at high reactions occur
Catalysts can be inorganic (metals), or organic (proteins), the latter of which is much more common in biological systems
Catalysts: Have 3 basic properties
increase the rate of reaction by lowering the activation energy requirement
Act by forming transient reversible complexes with substrate molecules
The catalyst is not permanently changed or consumed
Changes the rate at the which equilibrium is achieved, but have no effect on the position of equilibrium
Makes the amount of energy needed for a reaction much lower
Enzymes as biological catalysts: most biological catalysts
protein catalysts are ENZYMES
Some are RNA molecules called RIBOZYMES
Since these types of catalysts are organic molecules with a specific shape, they are much more specific than inorganic catalysts
Organic and inorganic catalysts increase reaction rates by 10^7-10^17, and 10³ - 10^4, respectively