Chapter 8 I Energy and Life Energy ability

Chapter 8

I. Energy and Life • • • Energy = ability to do work w/o energy life would cease A. Autotrophs and Heterotrophs – Originally most all energy comes from ____ Plants and some other organisms use the sun’s energy to produce______. food sun

– ________make their own food. – _________obtain energy from food they consumer – Some obtain energy as decomposers – There are several forms of energyradiant(light), electrical, chemical, mechanical autotrophs heterotrophs

B. Chemical Energy and ATP – – When electrons in bonds are shifted from higher to lower energy levels, ________is released as heat and light __________is one of the principal chemical compounds used to store and release energy The extra energy Adenosine triphosphate

The 3 Phosphate groups are the key to ATP’s ability to store and release energy

1) Storing energy • ____________is a compound that looks a lot like ATP, except it has 2 phosphate groups and this difference is the key to storing energy. When a cell has energy available it can store small amounts by adding a phosphate to ADP, making ATP (think of ATP like a fully charged battery) Adenosine diphosphate (ADP)

2) Releasing Energy • Energy stored in ATP is released by breaking the bond between the 2 nd and 3 rd phosphates, releasing energy as needed. This can power such things as ________across the membrane of the cell, protein synthesis and muscle contraction Active transport

• ATP is exceptionally useful as the _______________. Basic energy source of all cells

C. Using Biochemical Energy – For active transport---______________that pumps Na+ out of cell and K+ into the cell. ATP keeps the pump working and keep ions balanced A sodium-potassium pumpa membrane protein

• ATP powers synthesis of proteins, _________ and responses to ___________. Nucleic acids Chemical signals @ cell surface

• Cells only have a small amount of ATP, to last seconds…. . not good for long term storage(1 molecule glucose stores 90 x the chemical energy of ATP ). Cells can regenerate ATP from ADP as needed by the energy in foods like glucose

D. Heterotrophs and Autotrophs _______________get s food from eating or ingesting othersmay eat autotrophs or other heterotrophs---includes fungi ____________make their own food/primarily by photosynthesis-which uses light to convert CO 2 and H 2 O into carb’s and O 2 • autotrophs heterotrophs

II. Photosynthesis: An Overview – Plants use the energy of sunlight to convert water and CO 2 into sugars and starches, as well as O 2

A. Investigating Photosynthesis – Centuries ago the simple question was did the increase in tree’s mass come from soil, water or air? • • 1) Van Helmont’s Experiment 1600’s-Belgian physician did an experiment to see if the soil caused plants to grow, by trying to grow w/o soil…. he concluded most of the gain in mass was from water…. . this accounts for ½ the products of photosynthesis.

2) Priestly’s Experiment – – Candle w/jar over it-concluded that air enabled it to burn He put a sprig of a plant under the jar and waited a few days, …The candle could burn briefly under the jar…So he concluded the plant ____________ Produced oxygen

3) Jan Ingenhoutz • —showed the plant produced oxygen only if exposed to light » In conclusion to all 3 experiments, it is concluded that plants exposed to CO 2 and light and water, produce O 2 and carb’s

B. The Photosynthesis Equation light • 6 CO 2 + 6 H 2 O--- C 6 H 12 O 6 + O 2

• Plants use the sugars to produce complex carb’s such as _______ starches

C. Light and pigments • • • Photosynthesis also requires light and Chlorophyll (found in Chloroplasts) White light is a mixture of different wavelengths of light---seen as _____ Plants gather the sun’s energy with light absorbing molecules called______. Color pigments

• The principal plant pigment is_________. -chlorophyll a and b • Chlorophyll absorbs light well in the blue-violet and regions, but not well in the ________region, which is reflected by leaves green Chlorophyll

• Contain red and orange pigments like _________, that absorb light in other regions • When chlorophyll absorbs light, much of the energy is transferred directly to electrons in Chlorophyll , raising _____________which make photosynthesis work!!! carotenes The energy levels

• Chloroplasts contain pigments in membranes called __________/a stack= 1 granum ; plural are grana • Fluid portion of chloroplast is called stroma • A large portion of light absorbed by the chloroplast transfers directly to electrons in the chlorophyll molecule itself. By raising energy levels , light can produce steady supply of high energy electrons---the key to photosynthesis Thylakoids

• D. High Energy Electrons • The high energy electrons produced by chlorophyll are highly reactive and need a special carrier(think of “hot potato “ analogy ) • Electron carriers= compounds that accept a pair of high energy electrons and transfer them/along w/ most of energy to another molecule

Figure 8 -5 Chlorophyll Light Absorption Section 8 -2 Absorption of Light by Chlorophyll a and Chlorophyll b Chlorophyll a V Go to Section: B G YO R

III. The Reactions of Photosynthesis • A. Inside a Chloroplast – Photosynthesis takes place in the _______. – The chloroplasts contain saclike membranes called _________ which are arranged in stacks known as ________ chloroplasts THYLAKOIDS grana

– Proteins in the Thylakoid membrane organize chlorophyll and other pigments into clusters known as __________-These are the light –collecting units of the chloroplast – Light dependent reaction happens in ___________. photosystems Thylakoid membrane

• Light-independent (Calvin-cycle) reaction happens in _______-region outside thylakoid membranes stroma

Figure 8 -7 Photosynthesis: An Overview Section 8 -3 water CO 2 Light Chloroplast NADP+ ADP + P Light. Dependent Reactions ATP Calvin Cycle NADPH O 2 Go to Section: Sugars

B. Electron Carriers • When sunlight excites electrons in chlorophyll, the electrons gain a great deal of energy…. . They require a carrier---_________by electron transport chain – ____nicotinamide adenine dinucleotide phosphate-accepts 2 high energy electrons along w/ a H+, converting it into _____. This is one way some of energy of sunlight is trapped in chemical form Compound that can accept a pair of high energy electrons and transfer w/ most of the energy to another molecule NADP+ NADPH

• ___________-then becomes an electron carrier NADPH

C. Light –Dependent Reactions – Require light – Light is used to produce ATP and NADPH

Figure 8 -10 Light-Dependent Reactions Section 8 -3 Photosystem II Hydrogen Ion Movement Chloroplast ATP synthase Inner Thylakoid Space Thylakoid Membrane Stroma Electron Transport Chain Go to Section: Photosystem I ATP Formation

– 1 -Photosynthesis begins when pigments in photosystem II absorb light. Energy is absorbed by high energy electrons and passed on to electron transport chain. New electrons come from the water (water is required in these reactions to provide source of electrons and H+ ions), and O 2 is released into air-as a BYPRODUCT – 2 -High –energy electrons move from electron transport chain from photosystem II to photosystem I(simply discovered before photosystem. II). Energy from electrons is used by molecules in electron transport chain to transport H+ ions from stroma into the inner thylakoid space.

– 3 --Pigments in __________use energy from light to regenerate electrons. NADP+ picks up high energy electrons, along w/ H+ ions, at outer surface of thylakoid membrane…+ H+ ion=NADPH/Photosystems are clusters of chlorophyll and protein and are essential to light dependent reaction. They absorb light and make high energy electrons that are passed onto high energy electron carriers in thylakoid membrane. Photosystem I

• 4 - As electrons pass from chlorophyll to NADP+, more________are pumped along the membrane…. Eventually , the inside of the membrane fills w/ H+ ions……outside of membrane is ____________charged…The difference in charges (a gradient)produces energy for ATP…. This is why H+ ions are so important. H+ ions negatively

• 5 --H+ ions cannot cross membrane directly…. . But, the membrane contains a protein called _____that goes across the membrane and allows H+ ions to pass through it. (produced by gradient)As H+ passes through , ATP synthase, the protein rotates, binding w/ ADP and a phosphate group to make_________ So…. . light-dependent part makes high energy electrons and also ATP synthase ATP

• Electron transport chain= series of electron carriers proteins that move electrons during reactions fueled by ATP. At end of chain electrons pass to photosystem I • Pigments in photosystem I use energy from light to reenergize electrons/NADP+ NADPH

D. The Calvin Cycle – – – The ATP and NADPH from light-dependent part are not stable enough to store energy for more than a few moments…. these are used in _______to make high energy compounds that can last a long time----it makes ________. Absorb CO 2 and use ATP and NADPH to make high energy sugars Does not require light so is called ___________ sugars Calvin Cycle Light-independent

Figure 8 -11 Calvin Cycle CO 2 Enters the Cycle Energy Input Chlorop. Iast 5 -Carbon Molecules Regenerated 6 -Carbon Sugar Produced Sugars and other compounds Go to Section:

• • 1) 6 CO 2 molecules enter from the atmosphere. They combine w/ 6 __________. The result is 12 3 -C molecules. 2) 12 3 -C molecules convert to higher energy forms…. The energy for this comes from ATP and __________. 5 -Carbon atoms High energy electrons from NADPH

• 3) 2 3 -C molecules removed from cycle…these are used to produce____________________ needed for plant metabolism and growth Building blocks of Sugars, lipids, amino acids and other compounds-other macromolecules

• • Remaining 10 3 -C are converted back into 6 5 -C molecules. They combine w/ 6 new CO 2 molecules to begin cycle again. ***** 2 sets of photosynthetic reactions work together-light-dependent traps energy of sunlight in ______ and light –independent reactions(Calvin Cycle) use that chemical energy to produce stable, high energy sugars from CO 2 and water…. also O 2 is produced 4) Chemical form

E. Factors affecting Photosynthesis • • • Water supply Temperature---affects enzymes Light intensity----it does reach a maximum-or optimal level of light, depending on plant type--eg. conifers only photosynthesize on _____________. Warm. sunny days

• Photosynthesis Under Extreme Conditions • To conserve water, most plants under bright light close openings in leaves that normally take in CO 2 -keeps plants from drying out, but CO 2 levels fall low and photosynthesis slows down • However, some plants have adapted to such bright light and hot conditions

• C 4 plants-specialized chemical pathway to capture even low amounts of CO 2 for Calvin cycle(1 st compound made has 4 C’s)/requires extra ATP-include crops like corn, sugarcane, and sorghum

• CAM plants-plants adapted to dry climate get CO 2 while minimizing water loss-family CRASSULACEAE(CRASSULACEAEN ACID METABOLISM)-CO 2 becomes part of organic acids-Admit air into leaves only at night-During day leaves sealed tightrelease CO 2, allowing carb production(pineapple trees, many cacti , ice plants)