Chapter 4 - Energy Transfers And Transformations

Question 1

Photosynthesis

1. Define
2. What organisms is chlorophyll found?
3. Chlorophyll pigments mainly absorbs what wavelengths?

Answer 1

1. The process in which light energy is transformed into chemical energy.
2. Plants, algae, purple and green bacteria and Cyanobacteria.
3. Red and blue/violet wavelengths.

Question 2

Photosynthesis: balanced equation

Answer 2

6CO2 + 6H2O —> C6H12O6 + 6O2

• above arrow = sunlight
• below arrow = chlorophyll

Question 3

Bacterial origins of chloroplasts

Answer 3

Evidence seems to indicate that chloroplasts of plant and algae cells were once free-living photosynthetic microbial cells that were engulfed eons ago by another microbial cell - endosymbiosis - one organism takes up permanent residence inside another to benefit both.

Question 4

2 stages of photosynthesis

Answer 4

1. Light-dependent reactions
   • occurs in the thylakoid membrane
   • chlorophyll traps light energy and uses it to split water molecules into hydrogen ions (which are taken up by hydrogen acceptor molecules. I.e. NADP+ to form NADPH) and oxygen gas to create ATP molecules.
   • only NADPH and ATP molecules take part in the second stage.
2. Light-independent reactions (the Calvin cycle)
   • occurs in the stroma (fluid matrix of the chloroplast)
   • the hydrogen ions from the NADPH are combined with carbon dioxide (that diffuses into the chloroplast from the atmosphere) to form glucose. The ATP produced during the light reaction provides the energy required for this process.

Question 5

5 factors affecting photosynthesis

Answer 5

1. CO2 levels
2. Light intensity
3. Temperature
4. Water
5. Chlorophyll - lack of magnesium, nitrogen

Question 6

Cellular respiration: balanced chemical equation

Answer 6

C6H12O6 + 6O2 —> 6CO2 + 6H2O

*seconary arrow = 36 ATP

Question 7

Three stages of cellular respiration

*diagrams

Answer 7

1. Glycolysis:
   • occurs in the cytosol
   • does NOT require oxygen
   • involves the splitting of one glucose molecule into 2 pyruvate molecules and the energy released produces 2 ATP molecules, which is used to form 2 NADH molecules.
   • two possible pathways: no oxygen = anaerobic respiration/fermentation, oxygen = aerobic respiration.
   - anaerobic pathway: animals = end product is lactate (lactic acid), plants/yeast/microorganisms = end product is alcohol and CO2c stays in the cytosol and no further ATP harvester from the glucose molecule.
   - aerobic pathway: involves two more stages.
2. Krebs cycle (the citric acid cycle)
   • occurs in the matrix of mitochondrion.
   • pyruvate is converted into acetyl-coA which enters the Krebs cycle. The 2 pyruvate molecules are broken down, CO2 molecules are formed and the energy released produces ATP, CO2c NADH, FADH2.
   • NADH and FADH2 are electron carriers.
3. Electron transport chain:
   • system of electron carriers (cytochromes) are embedded into their inner membrane of the mitochondrion - cristae.
   • electrons donated by NADH and FADH2 molecules formed during the Krebs cycle, are passed along a series of cytochromes until they are finally accepted by oxygen.
   • donating electrons causes an energy transfer which creates enough energy for ADP to be converted to ATP.
   • the hydrogen ions (protons) combine with the oxygen and the electrons to form water.
   • for every 2 pyruvate = 1 glucose.
   • the energy released from the transport chain produces >30 ATP molecules.

Question 8

1. Where
2. Inputs
3. Outputs

Photosynthesis:
• Light dependent reactions
• Light-independent reactions (the Calvin cycle)

Cellular respiration
• Glycolysis
• Krebs cycle (the Citric Acid Cycle)
• Electron transport chain

Answer 8

• light-dependent reactions
1. Thylakoid membrane
2. H2O, light energy, NADP+, ADP+, P
3. O2, NADPH, ATP
• Light-independent reactions (the Calvin cycle)
1. Stroma
2. CO2, ATP, NADPH
3. ADP, P, NADP+, C6H12O6

• Glycolysis 
1. Cytosol
2. C6H12O6, ADP, P, NAD+
3. 2 pyruvate, 2 ATP, NADH
• Krebs cycle
1. Matrix of mitochondria
2. Pyruvate, ADP, P, NAD+, FAD+
3. ATP, NADH, FADH2, CO2
• Electron transport chain
1. Mitochondrion cristae (membrane)
2. NADH, FADH2, ADP, P, O2
3. >30 ATP, NAD+, FAD+, H2O

Question 9

Cristae

Answer 9

A fold in the inner membrane of a mitochondrion.

• wrinkled shape
• provides a large surface area