Botany12

Chp 7 – The Energy of Life

In order to perform the work of living an organism needs to extract energy from its environment.

The chemical processes used by living organisms to conduct the biochemical reactions that are life use energy. Energy cannot simply be created by the orgsanism, organisms convert energy fromone form to another by means of their metabolisms, that is through controlled chemical reactions.

Energy, like nutrients is cycled through the environment. As energy is ised by the organism, some of the energy is lost as heat.

Heat is mneasured by calories - a CALORIE is the amount of energy required to raise one gram of water one degree Celsisus. When you speak of Calories in food you are generally speaking of Kilocaloires (1000 calories) expresseed with a captial C.

FIRST LAW OF THERMODYNAMICS

(also known as the Law of tConservation of Energy) Energy cannot be created or destroyed but uit can ber changed from one form to anohter. All the enrgy that ewver existed in the universe is all there will ever be.

SECOND LAW OF THERMODYNAMICS

When energy is converted from one form to another some usable energy is degraded into a nonusable form, usually as waste heat. As a result the amount of energy available to do work in the universe decreases over time.

Energy is not destroyed in this conversion but simp[ly lost to the ability to do work, it is in a less usable form or more disorgainzed. Entropy is the measure of disorder or randomness in a system. Usable energy has a low order of entropy, disorganized systems has a high order of entropy. You book mentions that as the universe tends toward a more diordered form it will reach a point where there is a constant temprature (no extremes) and no motion.

No process involving the converison of energy can be 100% efficient. Your conversion of food to energy is about 50% efficient.

These laws are inportant in individual organisms and in the considersation of ecosystems.

The opposite of entropy is FREE ENERGY, the amount of energy available to do work. As the universe heads toward a condition of maximum entropy it could also be viewed as heading toward a condition of zero free energy.

Chemical reactions may be either exerggonic or endergonic. Exergonic reactions are those that release energy…therefore the products produced by the reactions option less energy than the materials which reacted. Likewise, endogonic reactions are those that require a net input of energy and the reaction products contain more energy than the reractants.

Some chemical reactions are able to be reversed!

The smaller the rection in terms of energy exchange the easier it is to reverse. This enable cells and organisms to regulate the release of energy. Dynamic Equilibrium describes a condition where although reactions are taking place there is no net change, that is the amount of change in one direction equals the amount of change in the other (example people moving in and out of a city balance and the population stays the same.) In dynamic equilibrium the net energy between the reactions is zero.

HOW DOES ATP WORK?

Remember adenosine triphosphate? (ATP) ATP is the means of energy in cells.

ATP is a modified nucleotide (related to DNA and RNA) with 3 inorganic phosphate groups. The 3 phosphate groups are attached in a series at the end of the molecule. The chemical bonds which attached are readily attached or detached. They are easily detached by hydrolysis (addition of water). The removal of a phosphate group is exergonic (energy releasing) . To add a phosphate group to the molecule is endergonic (energy added). These additions and subtractions either give up or require energy.

Chemical enzymes are biological catalysts., they increase the rate of a chemical reaction but are not consumed during the process. Most enzymes are proteins. Enzymes are specific, that is they work on certain materials, in certain conditions and in certain orders. Enzymes are usually named after the substance they act on …with the suffix -ase. They act to increase the rate of a reaction by lowering the amount of energy necessary to initiate the reaction: to form new bonds in a chemical reaction old bonds must be overcome. The energy required to start this action is called activation energy. An enzyme acts to lower the amount of the activation energy.

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Chp 9 Capturing Energy: Photosynthesis

Directly or indirectly most organism depend on photosynthesis. Can you think of one group that does not?

Light: A portion of the radiation spectrum; at one end are gamma rays at the other are radio waves. Light acts as if it is comprised of both waves and particles (called photons). Color is associated with the wavelength. The shorter the wavelength the more energy in a photon of light.

Chlorophyll is the green pigment that absorbs light in the first step of photosynthesis. Though there are different kinds of chlorophyll, most plants have chlorophyll a and chorophyll b. Other photosynthetic pigments include carotenoids (orange/yellow). Chlorophyll and other photosynthetic pigments are located in the thylakoids, which are tiny sacs located in the chloropplasts of eukaryotic cells. The chloroplast is within an envelope of a double membrane. Within the interioir of the chloroplast are stacked thylakoids called grana. SEE PAGE 172 GO TO PAGE

Light Dependent Reactions (from page 173)

  1. Chlorophyll absorbs light energy, which triggers a flow of excited, or energized electrons from the chlorophyll molecule.
  2. Some energy is transferred from the the energized electrons to chemical energy and used to phosphorylate adenosine diphosphate (ADP) to form adenosine triphosphate (ATP)
  3. Some of the energy is used to split water with oxygen being released
  4. Hydrogenb combines with the electron carrier molecule nicotinamide adenine dinnucleotide phosphate (NADP+)

The Dark Reactions… Energy is from the sun is used to make ADP and to reduce NADP+. Carbon dioxide is not used in light dependent operations and glucose is not produced. These activities are not depenedent on light. The products of the light reactions are used to form glucose from the energy stored in the ATP and the locked up hydrogen. This phase is known as the Calvin Cycle. Most of the glucose is stored by the plant as a starch for later use.

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