Ch. 4 Cellular

Energy Production &

Harvest

Energy

• =

• First law of thermodynamics = energy cannot be created or destroyed. It can be converted to different forms

• Energy is lost as heat with each conversion process

•Photosynthesis converts the energy from the sun into ATP, which drives formation of simple sugars•Cells metabolize the sugars to harness the energy for cellular work.

Fig 6.3

ATP: Adenosine

Triphosphate

ATP: Adenosine Triphosphate

• The cell’s energy carrier

• Can be regenerated:

Fig 5.7

How is ATP generated?

• Electron transfer chains:

Energy released at each step is used to make ATP

PhotosynthesisPhotosynthesis

Photosynthesis - overview• = conversion of light energy (from the sun)

into chemical energy (stored in sugar & organic molecules

• Plants, algae (protists), cyanobacteria, phytoplankton

• .

– They are the bottom of the terrestrial food chain– All complex organisms on land depend on plants

(ultimately) for food & O2.

Photosynthesis occurs in the chloroplast

Fig 7.3

Chloroplast anatomy

• Thylakoid membranes –

• Stroma –

Photosynthesis - overview

• 6CO2 + 6H20 C6H12O6 + 6O2

• O2 is released as a by-product from the splitting of water

• 2 interdependent pathways:

1. Light reactions –

2. Calvin cycle – carbon fixation (creation of glucose from CO2 gas)

Figure 10.4 An overview of photosynthesis: cooperation of the light reactions and the Calvin cycle (Layer 3)

Fig 7.4

Pigments

• =

• Chlorophyll – main PSN pigment, absorbs light (reflects green) to initiate the light reactions

Photosystems • =

• “Kick” electrons to an excited state (high energy)

Fig 7.9

Steps of the light reactions

1. Photosystem absorbs light, splitting water into H+, electrons, and O2.

2. Further light absorption by the photosystem kicks the electrons up to an excited state.

3. Excited electrons are passed along an electron transport chain (proteins in the thylakoid membrane)

4. Energy released at every step of electron transport used to drive ATP synthesis

5. Further light absorption by a second photosystem kicks the electrons up to another excited state, passing the electrons off to generate NADPH.

Fig 7.12

Fig 7.11

The Calvin Cycle

• = the use of ATP & NADPH to convert CO2 to carbohydrates

Cellular Respiration

Figs. 6.5&6.6

Fig 6.4

Aerobic Respiration• =

• Summary equation: C6H12O6 + 6O2 6CO2 + 6H2O• 3 Steps:

1. Glycolysis Occurs in the cytoplasm Glucose converted to pyruvate

Steps 2 & 3 occur in the mitochondria

Fig. 6.7

2. Krebs cycle

• Electrons and protons (H+) are released in the reactions & carried to step 3

3. Electron transfer chain & ATP formation

• electrons transferred along a series of trans-membrane proteins in the inner mitochondrial membrane

• O2 accepts spent electrons and H+s to produce H2O

Fig 6.12