Photosynthesis and Cellular Respiration Living systems are made of matter but require energy to carry on life functions. What is the source of ALL energy on Earth? (fuel, food, etc.) Photosynthesis and Cellular Respiration

Be able to label crest, trough, amplitude, wavelength and normal.

Matter is recycled; energy is not. Autotrophs (producers) capture the sun’s energy in a process called photosynthesis and store it in the bonds of a glucose molecule constructed from existing atoms. Molecules are passed from prey to predator, but only 10% of the available energy is passed on to the next trophic level. 90% of the energy is used for life processes or lost as heat.

Energy from the sun arrives on earth in the form of visible light, a type of electromagnetic radiation Notice this is backwards from our mneumonic. The order from LONGest wavelength, LOWEST frequency to shortest wavelength, highest frequency is … Radio, Micro, Infrared, Visible, UV, Xray, Gamma (Red Martians Invaded Venus Using Xray Guns)

How objects appear different colors White light is a mixture of all wavelengths (and colors) of light White light When light hits an object three things can happen to the light it’s absorbed (stays in the material) it’s transmitted (passes through) it’s reflected (bounces back) The wavelength that is reflected determines the color we see. Green light Is reflected and transmitted We see the Plant as green Red and blue light Is absorbed

Figure 10.6 Why leaves are green: interaction of light with chloroplasts Plants appear green because pigments in the leaf absorb all wavelengths except green (which is reflected).

The wavelength of light a compound absorbs can be determined by a spectrophotometer Spectrophotometers measure % transmittance (how much light went through). If a sample has a low % transmittance, it will have a high % absorption because the pigments in the test tube sample did not allow the light to be transmitted (passed on to the photoelectric tube).

Energy Pathway: The Big Picture cellular respiration photosynthesis Chemical energy for use in the form of ATP Light energy from the sun Chemical energy stored in glucose, fats, or carbohydrates Photosynthesis traps energy from the sun in the chemical bonds of a molecule such as a carbohydrate. In respiration, the carbohydrate energy is harvested and stored in the phosphate bonds of an ATP molecule.

Anabolism Two organelles are vital for energy capture and transfer to ATP, which makes it available for cells to use. Chloroplasts (found in autotrophs) and mitochondria (found in all cells) have a double membrane structure. One theory, called the endosymbiont hypothesis, proposes that at one time these organelles were free-living organisms that developed a symbiotic relationship with a multicellular organisms. All the chemical reactions occurring in a living organism are called metabolism. Anabolic reactions (anabolism) is a synthesis reaction where a molecule is assembled. Photosynthesis is an example of anabolism Catabolic reactions (catabolism) are decomposition reactions where a molecule is broken down. Glucose is broken down and the energy harvested to put phosphates back on to AMP or ADP molecules. This process is called phosphoryllation and uses an enzyme called ATP synthase which is located in both thyllakoid and mitochondrial membranes. Catabolism

Overview of Cellular Respiration ADP + Pi + energy In mitochondria, the energy released from the catabolism of glucose is used to make ATP from ADP and Pi . The process is called phosphoryllation. Releasing energy requires oxygen. If none is available, organisms undergo fermentation instead. ATP

Overview of Photosynthesis In photosynthesis, energy from the sun (in packets called photons) is absorbed by pigment molecules (primarily chlorophyll) and used to produce glucose from CO2 If you delete six of the water molecules in both the reactants and products, this equation is exactly the same as the respiration on the previous slide

Photoautotrophs: Use sunlight to produce food molecules; includes plants and cyanobacteria

Photosynthesis takes place in the chloroplasts of plant cells Figure: 7.2a Caption: (a) In plants, photosynthesis takes place in organelles called chloroplasts.  Leaf cross-section Cells containing chloroplasts Leaves contain millions of chloroplasts

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DAY TWO

Review “big picture” www.ftexploring.com

Photosynthesis Review Occurs in the chlorplast Chlorophyll and accessory pigments capture electromagnetic energy by absorbing photons of light. The energy from light is captured and converted to chemical energy which is stored in the bonds of a biomolecule. Chemical energy is harvested to make ATP during cellular respiration.

Different plant pigments absorb different wavelengths of light. Chlorophyll a Chlorophyll b Carotenoids Amount of light absorbed Why is it advantageous for a plant to have more than one kind of pigment? (Each photosynthetic pigment has a distinct absorption spectrum.) 400 500 600 700 Wavelength of light (nm) Pigments include chlorophyll (a and b), carotenoids, xanthophylls and anthocyanins.

Figure 10.9 Location and structure of chlorophyll molecules in plants Notice that the porphyrin ring contains a single atom of magnesium. (Just as a hemoglobin molecule contains a single atom of iron) These are called “trace elements”. The plant (or animal) doesn’t need a large quantity but they are vital for proper cellular function.

Pigments are found in chloroplasts. Outer membrane Inner membrane Stroma Thylakoids Granum Pigments are found in chloroplasts. Figure: 7.2b Caption: (b) The internal membranes of chloroplasts form flattened, vesicle-like structures called thylakoids, some of which form stacks called grana. EXERCISE Using the drawing in part (b) as a guide, label the structures in the micrograph in part (b). Outer membrane Inner membrane Stroma Granum Thylakoid

Remember that chloroplasts contain more than one type of pigment Remember that chloroplasts contain more than one type of pigment. Chlorophyll (a, b, c) are the main ones but it also includes xanthophyll, anthyocyanins, phycobillins, etc. (look at your trackstar).

Factors affecting the rate of photosynthesis *LIGHT INTENSITY *TEMPERATURE *CO2 LEVEL

Photosynthesis: The Big Picture Light Dependent Reactions Occur in thylakoid membranes of grana Energy from the high energy electron of chlorophyll is used to make ATP and NADPH Light Independent Reactions (Calvin Cycle) Occur in enzyme-rich stroma ATP and NADPH are used to make glucose from CO2 (carbon fixation)

Photosynthesis Equation Light energy 6CO2 + 12 H2O + C6H12O6 + 6O2 + 6 H2O Two components: Light-dependent reactions Light-independent reactions Chemical energy (ATP, NADPH) Light energy Chemical energy (ATP, NADPH) Chemical energy (C6 H12O6) H2O O2 CO2 Energy Harvest Synthesis

When a photon of light strikes chlorophyll, an electron can be promoted to a higher energy state Electrons can be promoted to discrete high-energy states: e– Blue photons excite electrons to a higher energy state e– Red photons excite electrons to a high-energy state Figure: 7.6a Caption: (a) When a photon strikes chlorophyll, an electron can be promoted to a higher energy state, depending on the energy in the photon. Photons 1 2 Energy state of electrons in chlorophyll

Light excites e- in chl.a in PSII e- move to electron acceptor E- from PSI enter second e.t.c. which ends by making NADPH e- transferred along electron transport chain; as they lose energy, H+ protons move into thylakoid Light excites e- in chl a of PSI.

Moving Electrons LEO = lose electrons “oxidized” GER = gain electrons “reduced” OR OIL RIG Oxidized is lost ……….Reduced is gained

Replacing electrons 2H2O  4H+ + 4e- + O2 Water molecules inside the thylakoid membranes are split by an enzyme Process is called photolysis Results: 2H2O  4H+ + 4e- + O2

Chemiosmosis The movement of protons (H+) into the stroma releases energy which is used to phosphoryllate ADP + Pi to form ATP.

SUMMARY

Alternative Carbon Pathways C3 plants = Fix carbon exclusively through the Calvin cycle (see previous slide) C4 plants = used when CO2 levels are low (hottest part of the day, stomates closed) Includes corn, sugar cane, grasses Can produce same amount of carbs with half the water loss CAM plants = “crussulacean acid metabolism” CO2 incorporated into organic acids at night and released for fixation during the day Includes cacti, pineapples

Cellular Respiration Overview

Glycolysis Occurs in the cytoplasm Use 2 ATP to break 6-carbon sugar into two 3-carbon pyruvate; produces 4 ATP (net gain of 2) and 2 NADH If oxygen present, pyruvates continue to Krebs cycle If no oxygen present, pyruvates continue to fermentation (lactic acid or alcohol)

Alcohol fermentation: no oxygen present Pyruvate is converted to ethanol and CO2 is released. Glycolysis is believed to have been what ancient prokaryotes used for energy production long before oxygen levels were high enough to support electron transport chain.

Lactic Acid fermentation Pyruvate is directly reduced by NADH to form lactate. (NADH becomes NAD+) Used in human muscle cells when there is not enough oxygen getting to the muscles such as during strenuous exercise. A chemical pathway removes lactic acid as oxygen becomes available.

The Krebs cycle is the first part of cellular respiration. Pyruvate is oxidized to form acetyl CoA carbon dioxide released NADH produced coenzyme A (CoA) bonds to two-carbon molecule

The Krebs cycle Produces energy-carrying molecules including ATP NADH and FADH2 Citric acid is formed and CO2 is released

Electron Transport Chain The second part of cellular respiration when protein carriers are used to make NADH and FADH2 and ATP. high-energy electrons enter electron transport chain energy is used to transport hydrogen ions across the inner membrane hydrogen ions flow through a channel in the membrane One glucose nets up to 36 ATP Water is released as a waste product. Notice that proteins in the membrane pass along high-energy electrons in this ETC just as they did in photosystems II and I of photosynthesis.