Flow of Energy

Energy for Cells, Photosynthesis, and Respiration

Energy for Cells:

Living organisms need energy to function

WHERE DO THEY GET IT?

Free Energy: energy available to do biological work

Ex. Energy required for muscle contraction

Endergonic Reaction: chemical reaction requiring free energy

*Free energy comes from other chemical reactions:

Exergonic Reactions: “Energy releasing”

*Both reactions must be linked (b/c energy can’t just “wait around”)

*Most free energy comes from adenosine triphosphate-- ATP

ATP: A-P-P-P

*the bonds between P (phosphate groups) energy released

Ex. Hydrolysis: (ATP + H20); last P breaks off ADP

ATP + H20 ADP + Pi + energy

Mini Lab Demonstration:

*Can you detect energy released by a biological reaction?

1. Half fill a test tube with 3% hydrogen peroxide.

2. Use a thermometer– take initial temperature.

3. Add a small piece of fresh liver to the tube.

4. Observe what happens. After 1 min., retake temp.

What evidence of a reaction did you observe?

Was the reaction endergonic or exergonic?

Respiration with Oxygen:

*When ATP is used, energy is released.

HOW CAN ATP BE REPLENISHED???

*REJOIN ADP and PHOSPHATE to replenish supply of ATP

(But need energy to do so)

Cellular Respiration: some of energy released by breaking bonds of glucose converts ADP to ATP

*AEROBIC RESPIRATION: requires Oxygen

*Cellular respiration is usually aerobic

EXERGONIC

*First steps occur in cytoplasm; last steps are in mitochondria

C6H12O6 + 6O2 + 38 ADP + 38 Pi 6CO2 + 6H20 + 38 ATP

*Early steps of breaking down glucose require 2 ATP

Thus, a net product of 36 ATP are produced

*What’s this mean? 1 glucose molecule released little by little lots of ATP

ATP is the cell’s currency!!!!

Anaerobic Processes *absence of oxygen

*Some bacteria and muscle cells can switch between aerobic and anerobic processes

1. Lactic Acid Fermentation:

*enzymes break down glucose into 2 lactic acid molecules

C6H12O6 + 4 ADP + 4 Pi 2CH3CHOHCOOH + 4 ATP

Ex. Muscles build up lactic acid during excessive exercise

Alcoholic Fermentation: plants/ microorganisms

*enzymes break down glucose into 2 molecules of ethanol and 2 molecules of CO2

C6H12O6 + 4 ADP + 4 Pi 2C2H5OH + 2CO2 + 4 ATP

Ex. Yeast alcohol, gasoline additives, bubbles dough rises

*PRODUCERS absorb energy from

Creates chemical energy

LIGHT = WAVELENGTHSVISIBLE SPECTRUM= ROY G BIV

Some light is absorbed; some reflected

Ex. White reflects all

*Light energy chemical

energy due to pigments

Ex. Chlorophyll (a) appears green b/c reflects green light

Other pigments: CAROTENOIDS:

Yellow, orange, and red

*absorb other colors/ wavelengths and pass energy to chlorophyll (a)

THIS IS WHY

LEAVES CHANGE COLOR!!

!

PHOTOSYNTHESIS REACTION:6CO2 + 6H20 C6H12O6 + 6O2

* “” involves enzymes, chlorophyll, and light energy

*ENDERGONIC *ultimate source of energy comes from light

1. Place Elodea in two test tubes.

2. Fill test tubes w/ Bromothymol yellow and cover tubes with plastic.

3. Place one tube in direct light and the other in a dark place.

4. Compare in 24 hours.

5. If yellow color is gone, means CO2 is no longer present.

PHOTOSYNTHESIS: 2 PARTS:

1. LIGHT REACTIONS:

Chloroplasts: electrons absorb energy/ move to higher energy levels

3 MAIN EVENTS:

1. Light energy absorbed and converted to chemical energy in bonds of ATP

2. Water splits into H ions, O, and electrons

3. H ions from water attach to carrier coenzymes for later use

2. CALVIN CYCLE:

*Occurs in fluid of chloroplast

*Synthesizing sugars

REVIEW: WHAT ELEMENTS MUST BE PRESENT FOR SUGARS TO BE MADE?

Light reactions provide H ions and ATP + CO2

3 carbon sugars 6 carbon sugars more complex

*PLEASE REFER TO PAGE 160

**Photosynthesis is the opposite of respiration

**These processes are INTERDEPENDENT:

reactants of one are products of the other*Sugars are broken down in cellular respiration (ATP used)

ATP can’t be recycled– some given off as heat as well

Thus, a CONTINUOUS CYCLE is NECESSARY!!