SI Worksheet 13
1. Describe The Light Cycle. (Noncyclic and Cyclic)
PS are embedded in the thylakoid membrane
Light enters Photosystem 2 first.. Light is collected bounced around from Pigment molecule
to pigment molecule… It is funneled into the P680 chlorophyll.. the electrons are then
bumped up from ground state from the P680 to the primary acceptor… The primary
acceptor passes down the electron transport chain to the Photosystem 1. While the
electron was passes down the cytochromes an ATP was made… The electron transport is
gonna take it to P700 chlorophyll in Photosystem 1. Gonna take that electron and bump it
into the primary acceptor…. Run it down the second electron transport chain and a NADPH
is created.
 The 2 electrons in photosystem are replaced by the splitting of water. This results in 2
H+ and ½ O2….
 The electrons in photosystem are replaced from the electrons from the electron
transport chain
 This process is a form of NONcyclic Phosphorylation.
Don’t forget there is also CYCLIC PHOSPHORYLATION which only involves PS1
-Cyclic only involves the creation of ATP… DOES not produce 02, or NADPH, or consume
water
Primary Electron Acceptor funnels electrons back to the first electron transport chain
instead of the 2nd electron transport chain.
Because it does not produce 02 it is considered more primitive.
2. Describe the Calvin Cycle.
This process happens in the Stroma of chloroplast
3 C02 molecules each respectively attach to their own molecule of Rubisco which is a 5
carbon molecule with 2 phosphate groups…. The 3-6 carbon 2 phosphate molecules are
then split into 6 molecules with 3 carbons and 1 phosphates…. These 6 molecules are then
phosphorylated turning 6 ATPs into 6 ADPs… 6 NADPHs are made and one phosphate
group is lost from each molecule resulting in 6 3 carbon molecules with one phosphate
group which is G3P…. One out of these 6 G3Ps are used towards the creation of Glucose….
The 5 remaining G3Ps are then converted back into the 5 carbon beast Rubisco.. This
process converts 3 more molecules of ATP into ADP.
9 ATPS -- 9ADPs
6 NADPH - 6 NADP+
In order to create one molecule of Glucose, you need to use 18 ATP and 12 NADPH..
3. Compare and Contrast Cell Respiration and Photosynthesis
Compare – Both have an ETC
Have ATP synthesized
Involve electron carriers
Involve multiple memebranes and H+ gradients
In organelles with multiple compartments
Both have mitochondria
ContrastPhoto
Creates and fixes energy (Endergonic)
(Exergonic)
Chloroplast
Makes NADpH
Cell Rep
Requires and releases energy
Makes NADH
4. Describe photorespiration
When the concentration of Oxygen is higher than the concentration of CO2 in a plant
cell, this is a real problem…. This is because RUBISCO will start to bind O2 instead of CO2
because it has a higher affinity for 02…. When 02 binds instead of a CO2 you get a five
carbon beast instead of a 6 carbon beast. This beast then splits into a 2C molecule and a 3
C molecule, as opposed to the 2 3C molecules that would have been created if a Co2 was
fixed. This 2 carbon molecule is waste and leaves the chloroplast. This cuts the number of
3 carbon molecules down by 50%! Photorespiration makes NO ATP and NO GLUCOSE!!! It
uses ATP and NADPH and is bad for the plant. The 5 remaining G3Ps are used to
regenerate the Calvin cycle (remember we generated 1 of the 6 G3Ps we made to making
glucose.. we only have 5 here so they all go towards the regeneration of the cycle.
5. Describe C4 mechanism
This is a mechanism used to get around photorespiration
The very first time they fix CO2 it creates a 4 carbon molecule instead of a 3 carbon
C4 has spatial separation (Mesophyll and Bundle Sheath Cell)… C02 comes in the
mesophyll cell and it reacts with PEP which is a 3 carbon chain by way of PEP carboxylate
which prevents photorespiration in that it CAN ONLY FIX CARBON NOT OXYGEN… making
a 4 carbon beast (hence C4) oxaloacetate. Oxaloacetate gets turned into malate and exits
the mesophyll cell and enters the bundle sheath cell by way of the plasmadesmata. THIS IS
THE KEY… malate is converted back into C02 and also Pyruvate.. the reason this prevents
photorespiration is because you have created an environment in the BUNDLE SHEATH cell
that contains only CO2 and NO OXYGEN…. Therefore Rubisco will not be allowed to bind
with O2 because it is not present… it will only bind with CO2 which will effectively produce
sugar!!
6. Describe CAM mechanism
In CAM plants they close their stomata during the day. This helps these plants conserve
water, however it also prevents C02 from entering the cell. During the night, these plants
stomata opens and they take in CO2 and fix CO2 into organic acids. They store this CO2 in
their vacuoles until the morning when the stomata are closed.. During the day when the
light reaction can supply ATP and NADPH, CO2 is released from the organic acids made the
night before and are turned into sugar by way of the calvin cycle.
CAM differs from C4 because it has TEMPORAL SEPARATION
1. How many pairs of chromosomes does a human have? How many pairs are autosomes?
How many are sex chromosomes? What combination of sex chromosomes constitute
male and female?
23… 22…. 1 ….. XX female…. XY male…
2. Describe the DNA of a bacteria… how does it divide?
Single circular chromosome that does binary fission which is formed by the replication
of the single chromosome, the separation of the chromosome copies, and finally the
pinching of the cytoplasm which results in 2 identical daughter cells.
3. What are the 3 reasons to do mitiosis?
1. Mitosis as a form of reproduction
2. Growth and development
3. Tissue Renewal
4. Define sister chromatids.. What are they held together by?
Sister chromatids are identical copies of the same genetic material that are held by a
centromere.
5. What are the 3 parts of interphase?
1. G1
2. S – Synthesizes DNA, copies itself.
3. G2 – cant see anything visible, but the cell has already replicated its DNA.
6. What are the 4 main parts of Mitosis… Describe each..
a. Prophase- Start to see chromosomes (centromeres connecting sister chromatids),
nuclear envelope breaks, nucleolus goes away, One centriole moves toward the pole
while the other stays in its original position.
b. Metaphase – Chromosome pairs line up at the equator of the cell and make the
metaphase plate, There are 2 types of spindle fibers- 1. Kinetichore- These connect
directly to chromosomes by way of the kinetochore protein. 2. Nonkinetichore proteins –
run pole to pole don’t attatch to the chromosomes. 46 chromosomes are lined up at the
metaphase plate… these 46 chromosomes contain 92 sister chromatids.
C . Anaphase – The sister chromatids are pulled apart by way of the shortening of the
atatched kinetochore proteins. The non kinetochore proteins lengthen causing the
entire cell to elongate. Important motor molecule of microtubules is DYENIN.
d. Telophase – the nuclear envelope comes back and also the nucleolus… Cytokinesis
or the formation of a cleavage furrow begins which is facilitated by microfilaments and
the cell begins to split into 2 cells each with the original amount of genetic material.
7. Describe the G1 , M, G0 and G2 checkpoints…
G1- The checkpoint is crossed when growth factors tell the cell that it needs to begin
copying its DNA
G2 – After all the genetic material has been copied the cell passes G2 which tells the
cell everything is good to go to begin mitosis
M – Tells the cell it is ready to finish mitosis.
G0 – these cells are also called post-mitotic because they do not have the ability to do
mitosis. Muscle and brain cells are in this category.. these cells literally come Out of the
cell cycle.
8. CDK – Cyclin – MPK overview
9. Introduction to Meiosis