Chapter 10 - Photosynthesis

Question 1

What are heterotrophs?

Answer 1

They do not create their own foods and rely on compounds made by other organisms.

Question 2

What are autotrophs?

Answer 2

Create their own food “self feeders”.

They can sustain themselves without eating anything that comes from other organisms.

Question 3

What is photosynthesis?

Answer 3

A process where energy from the sun is converted into sugar and other organic molecules.

Question 4

How is the exchange of CO2 and O2 created?

Answer 4

Plants have small openings called stomata where it lets carbon dioxide come in and oxygen will be released. Chloroplasts are the green pigmented thing on the inside.

Question 5

What is the anatomy of a chloroplast?

Answer 5

https://image.slidesharecdn.com/10lecture-141019171226-conversion-gate01/95/10-lecture-gillette-college-biol-101030-13-638.jpg?cb=1413738884

Outer membrane
Inter-membrane space
Inner membrane
Granum (stacks of green pancakes)
Thylakoids (single pancake in the stack)
Thylakoids space (space inside of thylakoids)
Stroma (space inside the inner membrane where all the granum are)

Question 6

What is the light reaction?

Answer 6

The steps of photosynthesis that convert solar energy to chemical energy.

Question 7

What happens in a light reaction?

Answer 7

Water is split into hydrogen molecules and oxygen molecules, this cause oxygen to be released. The light that is absorbed by the chlorophyll will drive the transfer of the electrons and hydrogen ions (that came from water) and will transfer to an acceptor called NADP+ (close to NAD+ it just has one extra phosphate group). The solar energy reduces NADP+ to NADPH because of additions of a pair of electrons.
Light reaction will also generate ATP by adding a phosphate group to ADP.

Question 8

What order do the photosystems come in? Why?

Answer 8

Photo system II comes first
Photo system I comes next

Because they were named in the order of discovery, but photosystem II functions first in the light reactions.

Question 9

What happens in photo system II?

Answer 9

1. Light will excite the pigment molecules which will boost one of the electrons to a higher energy level. The excited state will move on to other molecules until it reaches and excites the P680 molecule. This will cause the P680 to run at a higher energy state.
2. The electron that is transferred from the pigment molecules are then moved from P680 to the primary electron acceptor. (P680 will turn to P680+ after electron is transferred.)
3. An enzyme catalyzes the splitting of water molecules into two electrons. This will help to supply and replace the P680 after one is transferred to the primary acceptor.

Question 10

What happens in the electron transport chain?

Answer 10

4. The electrons will then be transferred from photosystem II to photosystem I by the electron transport chain. This will also aid in the creation of ATP.
5. The exergonic “fall” (release of energy) of electrons to a lower energy level provides energy for the synthesis of ATP.
   - as electrons pass through the cytochrome complex, H+ are pumped into the thylakoids space that will help the proton gradient that is used in chemiosmosis.

Question 11

What happens in photosystem I?

Answer 11

6. While the electron transport chain is moving the light that goes into photosystem I causes the same reaction as the pigment molecules in photosystem II. It will excite each molecule and then ultimately excite the P700 molecule. The electron is transported to the primary acceptor and now the P700+ molecule needs more electrons which will be taken from the electron transport chain.

Question 12

What happens after photosystem I?

Answer 12

There is another electron transport chain where the electrons sent to the primary acceptor. Goes through ferredoxin protein and then the NADP+ reeducate changes NADP+ to NADPH. Two electrons are required to change the to NADPH.

Question 13

What is the Calvin cycle?

Answer 13

It’s similar to the citric acid cycle but it builds carbohydrates from smaller molecules and consumes energy.

The Calvin Cycle uses the chemical energy of ATP and NADPH to reduce CO2 to sugar.

Question 14

What is phase 1 of the Calvin Cycle?

Answer 14

Called carbon fixation.

3 CO2 molecules are inputted in. A CO2 molecule is taken one at a time and attached to a five carbon sugar. Done by the enzyme rubisco. The now 6 carbon molecule is split into two because it is so energetically unstable.

Question 15

What is phase 2 of the Calvin Cycle?

Answer 15

Called the Reduction phase
6 ATP come and add another phosphate group to each 3-phosphoglycerate. Then 6 NADPH , with a pair of electrons, will reduce a Carboxyl group to make the G3P molecule (it will also lose a phosphate group) G3P (a sugar) is then released and is used for other compounds and glucose.

*Important thing to remember is only 1 G3P is outputted not all 6 because the rest of them need to be used to complete the cycle.

Question 16

What is phase 3 of the Calvin Cycle?

Answer 16

The regeneration of the CO2 acceptor

Now the 5 G3P are rearranged to make 3 RuBP which is done by using 3 molecules of ATP. Now the RuBP is ready to get more CO2 and start the process over again.

Question 17

What is all of the inputs and outputs of the Calvin cycle?

Answer 17

3 CO2 to start process (enters one at a time)
6 ATP in phase 2
6 NADPH in phase 2
3 ATP in phase 3

Outputs:
6 ADP in phase 2
6 NADP+ in phase 2
1 G3P in phase 2 
3 ADP in phase 3

Question 18

What is the difference between a C3 plant, C4 plant and a CAM plant?

Answer 18

When the Calvin cycle enzyme adds CO2 to RuBP (ribulose bisphosphate) and make a 3 carbon compound as its first organic product are C3 plants.
C4 plants have higher CO2 concentration which means that the stomata doesn’t need to open up to get more so less water is lost. It also creates a four carbon compounds as its first organic product. These plants seem to do better in high oxygen environments.
CAM plants are more for arid conditions. They are more succulent (water storing plants). The difference is that carbon fixation and the Calvin cycle happen in the same cell but at different times of the day. Calvin Cycle happens in the day and carbon fixation happens at night.