Unit 2

Question 1

what is photosynthesis?

Answer 1

Photosynthesis is a process that occurs in plant cells, some bacteria (such as cyanobacteria), and some protists

Used to convert energy from sunlight into chemical energy (stored in sugars) to be used by the organism

Plant cells have specialized structures called chloroplasts to facilitate this process
Chloroplasts contain chlorophyll, a photosynthetic pigment

Question 2

what is the general equation of photosynthesis?

Answer 2

6CO2 + 6H2O —-> C6H12O6 + 6O2

Question 3

what are pigments?

Answer 3

Pigments are chemicals that absorb certain wavelengths of electromagnetic energy, in this case light.

Question 4

where does photosynthesis occur?

Answer 4

In eukaryotic cells, photosynthesis is confined to the chloroplast, an organelle highly adapted to the process.

Light capture occurs on the thylakoid membrane and the energy is collected in the stroma where carbon fixation & sugar manufacture happens.

Question 5

where does LDR occur?

Answer 5

In the thylakoid membrane

LDR captures light energy & fixes it as chemical energy in the form of ATP & NADPH.

Question 6

Describe the components of cholorplasts

Answer 6

• Double membrane
• The fluid in the chloroplast is called stroma
• Thylakoids ( the circular discs )
• Granum is stack of thylakoids
• Lumen is the fluid inside the Thylakoids

Question 7

What happens in the 1st step of LDR?

Answer 7

A photon of light is absorbed by the pigments in photosystem II and transferred to electrons. These electrons transfer their energy to the reaction centre of chlorophyll P680 & when enough energy builds up, a high energy electron is ejected from the photosystem.

The Z protein attached to PSII splits a water molecule (photolysis) to release replacement electrons generating oxygen gas and hydrogen ions.

Question 8

What happens in the 2nd step of LDR?

Answer 8

Electron Transport System (ETS) is a series of high energy electron carriers & a cytochrome proton pump.

Plastoquinone & plastocyanin are free floating in the membrane but are confined to the area between the photosystems & the cytochrome b6-f proton pump.

The pump moves protons into the lumen via active transport to strengthen the H+ gradient forming from photolysis. This gradient will be used by the ATP synthase transport enzyme to manufacture ATP in the stroma.

Question 9

what happens in the 3 rd step of LDR?

Answer 9

Light photons are absorbed in the same way as PSII and passed to the reaction centre. This centre is chlorophyll P700 & when charged will liberate another high energy electron. The electron is replaced by the one transferred from PSII.

The electrons are passed through the free floating high energy electron carrier ferredoxin to the enzyme NADP Reductase which fixes the electrons & their energy onto NADP+ in the stroma.

Question 10

what is ATP synthase?

Answer 10

The H+ diffuses through the ATP synthase & that motion is used to power the creation of ATP in the stroma. The ATP is vital to the fixation of carbon to make carbohydrates so the gradient must be constantly generated or the chloroplast runs out of energy.
This enzyme-transport protein is highly conserved across life and is almost genetically identical to the one in the mitochondria. That indicates that it evolved very early on in the evolutionary history of life.

Question 11

what happens in PHASE 1 of the Calvin cycle?

Answer 11

CO2 Fixation is the process done by RuBisCo of adding CO2 to RuBP (5C) to form the intermediate which splits immediately into PGA.

Question 12

what happens in PHASE 2 of the calvin cycle?

Answer 12

CO2 Reduction is where ATP & NADPH are used to convert the PGA into BPG and then G3P via the addition of high energy electrons. It is the G3P that is used to manufacture carbohydrates but most has to be recycled.

Question 13

what happens in PHASE 3 of the calvin cycle?

Answer 13

RuBP Regeneration uses the bulk of the G3P and additional ATP so that the cycle can be restarted.

Question 14

what are the 2 phases of cellular respiration?

Answer 14

1) Glycolsis

2) Anaerobic Respiration

Question 15

why is the purpose of cellular respiration?

Answer 15

In order for a cell to do work it needs to free ATP from the food it ingests (heterotroph) or produces (autotroph).

All food is ultimately converted into glucose which is used to power the cell.

The glucose must be processed to recoup the solar energy that was captured to fuel its manufacture.

The energy in the glucose is converted directly into ATP and into high energy electron carriers that can power production of more ATP.

Question 16

what is the general equation of cellular respiration?

Answer 16

C6H12O6 + 6O2 —–> 6CO2 + 6H2O + ATP

Question 17

Glycolysis

Answer 17

Glycolysis occurs in the cytoplasm of all cells and is an organised series of reactions to split glucose. If it stops, the cell runs out of ATP quickly.

Glucose is a very stable molecule so an input of energy is required to destabilize the molecule so that the energy can be harvested.

The energy from glucose is used to directly build ATP through substrate level phosphorylation and to build the high energy electron carrier, NADH.

Question 18

What are the 2 phases of Glycolysis?

Answer 18

1) The prep phase destabilizes and splits the glucose
( Step 1-5)
2) The payoff phase of glycolysis allows for energy to be made (more than what was used in the prep phase)

( step 6-10)

Question 19

Describe the prephase

Answer 19

The prep phase destabilizes and splits the glucose into two molecules of G3P.

1) Step 1: Add phosphate to destabilize glucose. ( ATP is used)
- ( Glucose ——> Glucose 6 Phosphate)

2) Step 2: Isomerase to rearrange molecule to further destabilize.
- ( Glucose 6 Phosphate —-> Fructose 6 phosphate )

3) Step 3: Add phosphate to destabilize molecule for split.

(ATP is used)

• ( Fructose 6 phosphate ——-> Fructose 1, biphosphate)
  4) Step 4: split into two separate three carbon molecules.
• ( Fructose 1, biphosphate —–> DHAP + G3P )
  5) Step 5: Isomerize to change DHAP to G3P for further processing.
• ( DHAP ——> G3P )

End Result of Part 1:
2-ATP are USED
2 G3P molecules created

Question 20

Describe pay off phase

Answer 20

The payoff phase of glycolysis allows for energy to be harvested, making back what was invested & more.

Step 6: Add phosphate & make NADH.This harvests some of the usable energy.
*redox reaction

( G3P + NAD(+) + Phosphate ——-> 1,3 bisphosphoglycerate + NAHDH + H(+) )

Step 7:
Make ATP & harvest more
of the energy.
*substrate-level phosphorylation

( 1,3 bisphosphoglycerate + ADP —–> 3 phosphoglycerate + ATP)

Step 8:
Rearrange molecule to destabilize so more energy can be harvested.

( 3 phosphoglycerate —-> 2 phosphoglycerate )

Step 9:
Remove water to destabilize
molecule further.

( 2 phosphoglycerate —> Phosphoelpyruvate + H2O )

Step 10:
Make ATP by
harvesting energy.
*substrate-level phosphorylation

(Phosphoelpyruvate + ADP + H (+) —–> pyruvate + ATP )

End Result of Part 2:
For 1 G3P: 
1-NADH created 
2-ATP created 
1 pyruvate created

End Result of Part 2:
For 1 glucose (2 G3P): 
2-NADH created 
4-ATP created 
2 pyruvate created

Question 21

what is the net result of glycolsis?

Answer 21

NET Result of Glycolysis: for every molecule of glucose,
2 net ATP
2 NADH
2 pyruvate molecules

Costs two ATP but you produce four ATP along with two NADH.

Pyruvate is toxic to the cell & must be removed quickly.

Question 22

ANAEROBIC RESPIRATION- Fermentation

Answer 22

A common anaerobic process is fermentation.

Fermentation is not an efficient process and results in the formation of far fewer ATP molecules than aerobic respiration.

Fermentation is a short sequence of reactions that uses the energy trapped in NADH to process the pyruvate into a form that can be disposed of. This process does not create any additional energy from the molecule and in fact, uses up the high energy electron carrier molecules produced by glycolysis.

There are two primary fermentation processes:
Lactic Acid Fermentation
Alcohol Fermentation

Question 23

Lactic Acid Fermentation

Answer 23

Occurs when oxygen is not available.

For example, in muscle tissues during rapid and vigorous exercise, muscle cells may be depleted of oxygen. They then switch from respiration to fermentation.

The pyruvate formed during glycolysis is broken down to lactic acid and energy is released

Glucose → Pyruvic acid → Lactic acid + energy

Question 24

Lactic acid fermentation in Animal cells

Answer 24

Eukaryotic animal cells deal with pyruvate when there is an increased energy demand coupled with a limited oxygen supply.

Animal muscle cells produce lactic acid during exercise and export the acid into the bloodstream.
When oxygen is available, lactic acid goes through a series of reactions in the liver and is converted into glucose again.

Question 25

Alcohol Fermentation

Answer 25

occurs in yeasts and some bacteria.

Pyruvate formed during glycolysis and is broken down to produce alcohol (ethanol) and carbon dioxide and is released.

Pyruvate → alcohol + carbon dioxide + energy