Thursday, November 29, 2007
Thurs-Day 2
Bio- we explained the two major parts of photosynthesis:
1. the light-DEPENDENT steps that occur in each GRANUM/stack of thylakoids during which water is "split" into hydrogen and oxygen; also, ATP is formed as the light energy absorbed by the photosynthetic pigments is converted into chemical potential energy in the bonds of ATP.
The hydrogen becomes part of a "hydrogen carrying molecule" (NADPH) and eventually becomes part of the glucose molecule that is synthesized in the STROMA region of the chloroplast (outside of the granum). The ATP that is formed in this first step is then transferred to the stroma to supply the energy required for the synthesis of glucose from inorganic carbon dioxide.
2. the light-INDEPENDENT steps occur in the STROMA; the reason that these steps occur whether or not light is available is that the light energy from step 1 is already stored in the bonds of ATP. However, if there is no light energy to be incorporated into ATP in step 1, there will be no ATP to drive the glucose-producing "Calvin cycle" in step 2.
In step 2, the hydrogen (of NADPH) from step 1 and the CO2 are synthesized into glucose in an energy(ATP)-requiring cyclic process known as the Calvin cycle.
The glucose that is made in the stroma via these two steps is ultimately:
1. used as an energy source in plant cellular respiration
2. synthesized into a complex carbohydrate such as cellulose or starch
3. used as a reactant with other compounds to form fats/oils, proteins, or nucleic acids.
We then looked at plant physiology to see how plants maintain homeostasis by regulating the amount of water and carbon dioxide that is available to be used in photosynthesis. When there is adequate water available, the "guard cells" on the underside of the plant leaf will swell and form a "mouth/opening" called a STOMATE. With the stomates open, more CO2 can enter the cells that make up the plant leaf.
However, under arid/dry conditions, the guard cells shrivel (due to the lack of water) and the stomate/opening shrinks and eventually closes; this closing of the stomate/mouth PREVENTS further water loss from the leaf so that photosynthesis can continue although at a slower rate due to the reduction of CO2 that can diffuse into the leaf that has closed stomates.
The outline of text section 9.2 is due on Monday.
Chem 7/8- THE HW PACKET IS NOT DUE UNTIL MONDAY.
We did a lab showing two different methods of seeing the unique photon/color emission spectrum of each element. We looked at the emission spectra of excited samples of H, He, and Kr. We also saw "flame tests" which are used to identify the presence of certain metal ions in various salt solutions because different metals have electrons that must undergo different energy transitions for the reasons explained yesterday.
We then looked at the two main problems with the Bohr Model of the atom:
there were some emission lines for every element (except for H) that were not predicted or accounted for by Bohr's calculations/model.
Also, in an astonishing experiment, JJ Thomson's son, showed that electrons have a "wave nature" in addition to their particle nature. Thus, any model that treats the electron solely as a particle is incomplete and not as accurate as it could be.
These problems led to a mathematical solution to finding all of the allowed specific energies of each electron in each element; the mathematical solutions resulted in the development of the quantum/wave mechanical model of the atom. This model accounts for all of the bright line spectra emission lines because it takes into account both the wave and particle natures of the electron as well as the electron to electron repulsions that occur in all atoms except for H. The repulsions between electrons and the wave nature of the electron causes the electron to exist in energy SUBLEVELS that are associated with an electron being in a specific region of probability/ORBITAL around the nucleus.
We will draw out the electron configurations of the first 20 elements using both the Bohr model and the quantum mechanical model.
Chem 9- THE HW PACKET IS NOT DUE UNTIL MONDAY.
We focused on the Bohr model and drew out electron configurations of several different atoms and ions. We defined the terms "ground state", "excited state", and "valence electrons".
Valence electrons, which are typically the electrons that are gained, lost, or shared in a chemical reaction, are, BY DEFINITION, the electrons in the HIGHEST NUMBER/OUTERMOST principal energy level. ONLY THOSE ELECTRONS are considered to be valence electrons!
We looked at the two main problems with the Bohr Model of the atom:
there were some emission lines for every element (except for H) that were not predicted or accounted for by Bohr's calculations/model.
The other problem involved the picture that I showed at the end of class. We will discuss that tomorrow.
1. the light-DEPENDENT steps that occur in each GRANUM/stack of thylakoids during which water is "split" into hydrogen and oxygen; also, ATP is formed as the light energy absorbed by the photosynthetic pigments is converted into chemical potential energy in the bonds of ATP.
The hydrogen becomes part of a "hydrogen carrying molecule" (NADPH) and eventually becomes part of the glucose molecule that is synthesized in the STROMA region of the chloroplast (outside of the granum). The ATP that is formed in this first step is then transferred to the stroma to supply the energy required for the synthesis of glucose from inorganic carbon dioxide.
2. the light-INDEPENDENT steps occur in the STROMA; the reason that these steps occur whether or not light is available is that the light energy from step 1 is already stored in the bonds of ATP. However, if there is no light energy to be incorporated into ATP in step 1, there will be no ATP to drive the glucose-producing "Calvin cycle" in step 2.
In step 2, the hydrogen (of NADPH) from step 1 and the CO2 are synthesized into glucose in an energy(ATP)-requiring cyclic process known as the Calvin cycle.
The glucose that is made in the stroma via these two steps is ultimately:
1. used as an energy source in plant cellular respiration
2. synthesized into a complex carbohydrate such as cellulose or starch
3. used as a reactant with other compounds to form fats/oils, proteins, or nucleic acids.
We then looked at plant physiology to see how plants maintain homeostasis by regulating the amount of water and carbon dioxide that is available to be used in photosynthesis. When there is adequate water available, the "guard cells" on the underside of the plant leaf will swell and form a "mouth/opening" called a STOMATE. With the stomates open, more CO2 can enter the cells that make up the plant leaf.
However, under arid/dry conditions, the guard cells shrivel (due to the lack of water) and the stomate/opening shrinks and eventually closes; this closing of the stomate/mouth PREVENTS further water loss from the leaf so that photosynthesis can continue although at a slower rate due to the reduction of CO2 that can diffuse into the leaf that has closed stomates.
The outline of text section 9.2 is due on Monday.
Chem 7/8- THE HW PACKET IS NOT DUE UNTIL MONDAY.
We did a lab showing two different methods of seeing the unique photon/color emission spectrum of each element. We looked at the emission spectra of excited samples of H, He, and Kr. We also saw "flame tests" which are used to identify the presence of certain metal ions in various salt solutions because different metals have electrons that must undergo different energy transitions for the reasons explained yesterday.
We then looked at the two main problems with the Bohr Model of the atom:
there were some emission lines for every element (except for H) that were not predicted or accounted for by Bohr's calculations/model.
Also, in an astonishing experiment, JJ Thomson's son, showed that electrons have a "wave nature" in addition to their particle nature. Thus, any model that treats the electron solely as a particle is incomplete and not as accurate as it could be.
These problems led to a mathematical solution to finding all of the allowed specific energies of each electron in each element; the mathematical solutions resulted in the development of the quantum/wave mechanical model of the atom. This model accounts for all of the bright line spectra emission lines because it takes into account both the wave and particle natures of the electron as well as the electron to electron repulsions that occur in all atoms except for H. The repulsions between electrons and the wave nature of the electron causes the electron to exist in energy SUBLEVELS that are associated with an electron being in a specific region of probability/ORBITAL around the nucleus.
We will draw out the electron configurations of the first 20 elements using both the Bohr model and the quantum mechanical model.
Chem 9- THE HW PACKET IS NOT DUE UNTIL MONDAY.
We focused on the Bohr model and drew out electron configurations of several different atoms and ions. We defined the terms "ground state", "excited state", and "valence electrons".
Valence electrons, which are typically the electrons that are gained, lost, or shared in a chemical reaction, are, BY DEFINITION, the electrons in the HIGHEST NUMBER/OUTERMOST principal energy level. ONLY THOSE ELECTRONS are considered to be valence electrons!
We looked at the two main problems with the Bohr Model of the atom:
there were some emission lines for every element (except for H) that were not predicted or accounted for by Bohr's calculations/model.
The other problem involved the picture that I showed at the end of class. We will discuss that tomorrow.
# posted by C @ 2:58 PM 
