Chapters 8 & 9:Photosynthesis &

RespirationAka: Energetics

PRODUCERS

PRIMARY CONSUMERS

Secondary Consumers

TOP

• Where do we get all our energy from?

• Ultimately from the Sun

By what process do we get this energy?

Photosynthesis

• Process by which green plants or organism with chlorophyll, convert light energy into chemical energy in the bonds of carbohydrates

• Autotrophic – – Can transfer energy to produce food – can

synthesize food– Plants, some bacteria & protists

• Heterotrophic – – Must obtain energy from preformed food –

gotta eat food – Fungus, all animals, some bacteria &

protists

What is needed for autotrophs to photosynthesize?

• Carbon dioxide (atmospheric)

• Water (in the soil or air)

• Sunlight (or artificial light source)

• Chlorophyll (present in leaves and sometimes stems)

• Enzymes (to regulate the rate of the reaction)

Experiments that lead to our understanding of Photosynthesis

• Van Helmont (1600’s)

• Experiment w/ potted plant to determine what a plant uses to grow.

• Conclusion: Water is necessary for plant growth

In his own words• I took an earthen pot and in it placed 200 pounds of

earth which had been dried out in an oven. This I moistened with rain water, and in it planted a shoot of willow which weighed five pounds. When five years had passed the tree which grew from it weighed 169 pounds and about three ounces. The earthen pot was wetted whenever it was necessary with rain or distilled water only. It was very large, and was sunk in the ground, and had a tin plated iron lid with many holes punched in it, which covered the edge of the pot to keep air-borne dust from mixing with the earth. I did not keep track of the weight of the leaves which fell in each of the four autumns. Finally, I dried out the earth in the pot once more, and found the same 200 pounds, less about 2 ounces. Thus, 164 pounds of wood, bark, and roots had arisen from water alone." (Howe 1965)

• Experimented w/ candle, plant & jar.

• Conclusion: Plants produce oxygen that is necessary for the candle to stay lit.

Priestly (1771)

• Repeated Priestly’s experiment but put plant in darkness with candle.

• Conclusion: Light is needed for photosynthesis & oxygen production.

Ingen-Housz (1779)

General formula for Photosynthesis

• CO2 +H2O (w/chlorophyll & enzymes) + light

C6H12O6 + O2 + H2O

This process actually occurs in

80 chemical reactions

Where in a plant does photosynthesis occur?

• Chloroplasts contain the pigment chlorophyll • Chloroplasts are oval structures consisting

of stacked grana (photosynthetic membranes)

• and a liquid called stroma. Chlorophyll is found in the stacked grana

• Main photosynthetic pigments are chlorophyll a and chlorophyll b

• Other pigments in plastids are accessory pigments to absorb all the wavelengths of light

So what is light? • White light

• Color depends of which wavelength is being reflected.

• So if a leaf is green, green light or wavelengths are being reflected and all other colors are being absorbed. If black, all the wavelengths (or colors) are being absorbed, reflecting nothing.

• Absorbed wavelengths become energy (heat or kinetic).

Is all light the same?• Using a spectroscope, we will look at

different light sources• Sunlight,• Incandescent light• Fluorescent light

Fluorescent light

Incandescent light

Plants just love red and blue light. They don’t utilize

much green or yellow

Why do leaves change color in the fall?

• Since chlorophyll a & b are the densest pigments, they break down first when water is sparse.

• This leaves the other pigments like the carotenoids, cyanins and xanthophylls to remain longer until they break down.

What happens to the energy absorbed by the

chlorophyll of the plants? • The energy will be stored in the bonds

of Adenosine Triphosphate (ATP).

• Animation

3 phosphate groups

Ribose

Adenine

• ATP is made up of adenine, ribose, and three phosphate groups.

• ATP acts as temporary energy storage.• You make and break down ATP molecules

constantly.• ADP + P = ATP• Think of ATP like cash in your pocket• Glucose like an ATM card• Glycogen like your savings

account• Lipids like a Savings Bond

Photosynthesis occurs in 2 major steps

1. Light Reaction –

occurs only in the presence of light. – Occurs in the grana (thylakoids) of the

chloroplasts– Also known as Photolysis because light is

used to split water molecules into hydrogen and oxygen

Light Dependant Reaction

This one is my favorite!

2.Dark Reactions (Light Independent rx)–

can occur in light or darkness. Follows light reaction

• Occurs in the stroma of the chloroplasts

• Also known as Carbon fixation because CO2 will get “fixed up” with the hydrogens and energy from the light reaction to produce Glucose

The Steps in Photosynthesis

THE LIGHT REACTION•  1) The light energy strikes the leaf, passes

into the leaf and hits a chloroplast inside an individual cell.

•  2) The light energy, upon entering the chloroplasts, is captured by the chlorophyll inside a grana. Electrons are excited.

NADPH & ATP are formed•  3) Inside the grana some of the energy is

used to split water into hydrogen and oxygen.

•  4) The oxygen is released into the air.

THE DARK REACTION – Calvin Cycle

5) The hydrogen (from NADPH) is taken to the stroma along with the grana's remaining light energy (ATP).

6) Carbon dioxide enters the leaf and passes into the chloroplast.

7) In the stroma the remaining light energy (ATP) is used to combine hydrogen (from NADPH) and carbon dioxide to make carbohydrates. This occurs during the Calvin Cycle

8) The energy rich carbohydrates are carried to the plant's cells.

 9) The energy rich carbohydrates are used by the cells to drive the plant's life processes.

Great Summary of Photosynthesis & Respiration

• A good one

Chapter 9: Respiration

aka: Getting energy from the cake

Think of Photosynthesis like baking a cake.

The plant takes the raw materials (CO2 & H2O), puts them together using energy (heat), & synthesize the cake.

In order to get the energy out of the cake, the plant & us must ingest it (eat), digest it (break it down into its monomers) & then we must “burn it” to release the energy stored in the bonds of the cake.

THIS IS RESPIRATION

How do we get the energy out of the food that we have consumed?

Cellular Respiration• Is the process by which

organisms obtain the energy that they need by releasing the chemical energy stored in nutrients

• Nutrient = Glucose• Chemical Energy = ATP

Occurs in the Mitochondria

of Eukaryotic organisms

Respiration occurs on the Cristae

Two Types of Respiration

• Aerobic RespirationAerobic Respiration – needs oxygen to release the energy in food

C6H12O6  +  6O2    6CO2  +  6 H2O  + 36 ATP

• Anaerobic RespirationAnaerobic Respiration – can release the energy from food without the need of oxygen. (Some bacteria & yeast)

C6H12O6    2CO2  +  2 Ethanol  +  2 ATP

C6H12O6    2Lactic Acid  +  2 ATP

Anaerobic RespirationAnaerobic Respiration

• Also known as Fermentation• Occurs in the cytoplasm of

yeast & some bacterial cells

• Since the organism are very small & simple, do not need much ATP

Anaerobic Respiration occurs in two steps1. Glycolysis

Glucose (6 Carbons) is broken down into 2 Pyruvic (3 Carbons each) acid molecules + 2 ATP (activation energy)

Produces 4 ATP, netting 2 ATP

2 ATP

Fermentation• The 2 Pyruvic Acids will

break down into:

1. Alcohol + CO2 (if yeast & some bacteria)

2. Lactic Acid (some bacteria)

Both forms will not produce any more ATP molecules

Uses for Fermentation

• Yeast & some bacteria

Used in baking, wine making & brewing industry

• Bacteria

Lactic acid production is used in cheese processing, buttermilk, sour cream, yogurt, sauerkraut, pickles. The souring of dairy products is actually the production of lactic acid by anaerobic bacteria

Aerobic RespirationAerobic Respiration• Occurs in the Mitochondria

• Yields more ATP per molecule of glucose (36 – 38 molecules) of ATP/Glucose

• Occurs in 3 basic steps

1.1. GlycolysisGlycolysisUsing 2 ATP as activation energy, a glucose molecule is broken down into 2 Pyruvic Acid molecules. 4 ATP are produced, leaving 2 ATP netted Occurs in cytoplasm

2. Krebs CycleKrebs Cycle – in the Mitochondria, the 2 Pyruvic acids are broken down, releasing CO2 & producing 2 ATP

3. Electron Transport ChainElectron Transport Chain – Oxygen combines with hydrogen

32 ATP are produced

Krebs CyclePyruvic AcidPyruvic Acid

2 Carbon Dioxides

Carbon DioxideCarbon Dioxide

How much more efficient is Aerobic Respiration than Anaerobic Respiration at releasing ATP from one molecule of

glucose?

Aerobic respiration yields 2 + 2 + 3236 ATPAnaerobic respiration yields 2 ATP 2 ATP

_______

36: 2

Aerobic Respiration is 18x’s more efficient!!!

Muscle FatigueMuscle Fatigue• You are a big organism & need a lot of ATP to

keep you fueled.

• At times though, you may not be breathing correctly & therefore, aren’t taking in enough O2 to remain an aerobic organism.

• During this time, your body (muscle cells) convert to anaerobic respiration to give you some ATP. Hey 2 ATP are better than none!

• Lactic acid accumulates in your muscle cells, acid burns the cells, causing you to cramp up & thus stop your activity & breathe normally