Energy Flow Through Living Things: Photosynthesis & Cellular Respiration Chapter 8&9

8-1 Energy and Life Living things need energy to survive comes from food energy in most food comes from the sun Plants use light energy from the sun to produce food autotrophs organisms that make their own food Ex - plants heterotrophs organisms that must obtain energy from the foods they consume animals

Chemical Energy and ATP Energy – the ability to do work Forms: light, heat, electricity, chemical compounds chemical compound that cells use to store and release energy is adenosine triphosphate (ATP) ATP - basic energy source for all cells

Chemical Energy and ATP The three phosphate groups are the key to ATP's ability to store and release energy. ATP consists of: adenine ribose (a 5-carbon sugar) 3 phosphate groups Adenine Ribose 3 Phosphate groups ATP is used by all types of cells as their basic energy source. ATP

Chemical Energy and ATP Storing Energy ADP has two phosphate groups instead of three. A cell can store small amounts of energy by adding a phosphate group to ADP. ATP ADP Energy + Energy Adenosine Triphosphate (ATP) Adenosine Diphosphate (ADP) + Phosphate Partially charged battery Fully charged battery

Chemical Energy and ATP Releasing Energy Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates. 2 Phosphate groups P ADP

Chemical Energy and ATP ATP energy uses: cellular activities: active transport, protein synthesis muscle contraction Most cells have only a small amount of ATP, because it is not a good way to store large amounts of energy. Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose.

8-2 Photosynthesis Photosynthesis - the process in which green plants use the energy of sunlight to convert water and carbon dioxide into high-energy carbohydrates and oxygen

The Photosynthesis Equation The equation for photosynthesis is: 6CO2 + 6H2O C6H12O6 + 6O2 carbon dioxide + water sugars + oxygen Light Light

The Photosynthesis Equation Light energy H2O Light-Dependent Reactions (thylakoids) O2 ADP NADP+ ATP NADPH Photosynthesis is a series of reactions that uses light energy from the sun to convert water and carbon dioxide into sugars and oxygen. CO2 + H20 Sugar Calvin Cycle (stroma)

Light and Pigments photosynthesis requires chlorophyll pigments - light-absorbing molecules that gather the sun's energy The main pigment in plants is chlorophyll. There are two main types of chlorophyll: chlorophyll a chlorophyll b

Light and Pigments Chlorophyll absorbs light well in the blue-violet and red regions of the visible spectrum. 100 80 60 40 20 Chlorophyll b Estimated Absorption (%) Chlorophyll a Photosynthesis requires light and chlorophyll. In the graph above, notice how chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum. Wavelength (nm) 400 450 500 550 600 650 700 750 Wavelength (nm)

Light and Pigments Chlorophyll does not absorb light will in the green region of the spectrum. Green light is reflected by leaves, which is why plants look green. 100 80 60 40 20 Chlorophyll b Estimated Absorption (%) Chlorophyll a Photosynthesis requires light and chlorophyll. In the graph above, notice how chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum, whereas chlorophyll b absorbs light in the blue and red regions of the visible spectrum. 400 450 500 550 600 650 700 750 Wavelength (nm)

Light Energy Light is a form of energy compound that absorbs light also absorbs energy from that light chlorophyll absorbs light  the energy is transferred directly to electrons in the chlorophyll molecule  raising the energy levels of these electrons high-energy electrons are what make photosynthesis work

Pop Quiz Word Bank ADP Ribose Phosphate groups Bonds ATP Adenine Adenosine This molecule is called _____. Energy in this molecule is stored in the _____. 3. 5. 4.

8-3 Inside a Chloroplast Inside a Chloroplast In plants, photosynthesis takes place inside chloroplasts. Plant Chloroplast Plant cells

Inside a Chloroplast Chloroplasts contain thylakoids—saclike photosynthetic membranes. Single thylakoid Chloroplast

Inside a Chloroplast Thylakoids are arranged in stacks known as grana. A singular stack is called a granum. Stroma – space outside of the thylakoids Granum Stroma Chloroplast

Inside a Chloroplast Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters called photosystems, which are the light-collecting units of the chloroplast. Photosystems Chloroplast

Photosynthesis Reactions reactions of photosystems include: light-dependent reactions (requires light) take place within the thylakoid membranes uses water, ADP, and NADP+ produces oxygen, ATP, and NADPH light-independent reactions (Calvin cycle) takes place in the stroma ATP and NADPH not stable enough to store the energy they carry for more than a few minutes uses ATP and NADPH energy to build high-energy sugars for long term storage

Photosynthesis Reactions The two sets of photosynthetic reactions work together. The light-dependent reactions trap sunlight energy in chemical form. The light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and water.

Light- dependent reactions Inside a Chloroplast H2O CO2 Light NADP+ ADP + P Light- dependent reactions Calvin Cycle Calvin cycle The process of photosynthesis includes the light-dependent reactions as well as the Calvin cycle. Chloroplast O2 Sugars

Electron Carriers electrons in chlorophyll absorb sunlight  electrons gain energy Cells use electron carriers to transport these high-energy electrons from chlorophyll to other molecules One carrier molecule is NADP+. transport electrons NADP+ accepts and holds 2 high-energy electrons along with a hydrogen ion (H+) - NADP+  NADPH energy of sunlight can be trapped in chemical form NADPH carries high-energy electrons to chemical reactions elsewhere in the cell to make carbohydrates

Factors Affecting Photosynthesis Many factors affect the rate of photosynthesis, including: Water Temperature Intensity of light

9-1 Chemical Pathways Food serves as a source of raw materials for the cells in the body and as a source of energy. Animal Cells Animal Mitochondrion Plant Photo Credits: left: ©Bob Gurr/DRK Photo; middle bottom: ©John Durham/Science Photo Library/Photo Researchers, Inc. ; middle top: ©Ron Boardman/Stone; right: ©Keith Porter/Photo Researchers, Inc. Plant Cells

Both plant and animal cells carry out the final stages of cellular respiration in the mitochondria. Outer membrane Intermembrane space Mitochondrion Animal Cells Inner membrane Photo Credits: left: ©Bob Gurr/DRK Photo; middle bottom: ©John Durham/Science Photo Library/Photo Researchers, Inc. ; middle top: ©Ron Boardman/Stone; right: ©Keith Porter/Photo Researchers, Inc. Plant Cells Matrix

Chemical Energy and Food One gram of the sugar glucose (C6H12O6), when burned in the presence of oxygen, releases 3811 calories of heat energy calorie - the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius Cells gradually release the energy from glucose and other food compounds beginning with glycolysis - releases a small amount of energy.

Overview of Cellular Respiration If oxygen is present: cellular respiration - the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen glycolysis  Krebs cycle  electron transport chain equation: 6O2 + C6H12O6 → 6CO2 + 6H2O + Energy oxygen + glucose → carbon dioxide + water + Energy

Overview of Cellular Respiration Electrons carried in NADH Electrons carried in NADH and FADH2 Pyruvic acid Glucose Glycolysis Cytoplasm Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place inside the mitochondria. Mitochondrion

Overview of Cellular Respiration Glycolysis – cytoplasm Krebs cycle and electron transport - mitochondria Glycolysis Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Glycolysis takes place in the cytoplasm. The Krebs cycle and electron transport take place inside the mitochondria. Cytoplasm Mitochondrion

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Glycolysis the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound ATP Production cell uses up 2 molecules of ATP to start the reaction When glycolysis is complete, 4 ATP molecules have been produced  a net gain of 2 ATP molecules NADH Production removes 4 high-energy electrons  electron carrier called NAD+  becomes an NADH molecule. The NADH molecule holds the electrons until they can be transferred to other molecules.

Glycolysis 2 ATP 2 ADP 4 ADP 4 ATP Glucose 2 Pyruvic acid Glycolysis is the first stage in cellular respiration. During glycolysis, glucose is broken down into 2 molecules of pyruvic acid. Glucose 2 Pyruvic acid

Glycolysis 2 ATP 2 ADP 4 ADP 4 ATP Glucose 2 Pyruvic acid

Glycolysis 2 ATP 2 ADP 4 ADP 4 ATP Glucose 2 Pyruvic acid

Glycolysis 2 ATP 2 ADP 4 ADP 4 ATP Glucose 2NAD+ 2 Pyruvic acid

Glycolysis 2 ATP 2 ADP 4 ADP 4 ATP Glucose 2NAD+ 2 Pyruvic acid 2

Glycolysis 2NAD+ 2 ATP 2 ADP 4 ADP 4 ATP 2 Pyruvic acid 2 To the electron transport chain

Glycolysis The Advantages of Glycolysis very fast - cells can produce thousands of ATP molecules in a few milliseconds does not require oxygen

Fermentation oxygen is not present  glycolysis is followed by a different pathway - fermentation Fermentation – release of energy (ATP) from food in the absence of oxygen cells convert NADH to NAD+ by passing high-energy electrons back to pyruvic acid Anaerobic – does not require oxygen

Fermentation Alcoholic Fermentation equation: Yeasts and a few other microorganisms use alcoholic fermentation Forms ethyl alcohol and carbon dioxide as wastes equation: pyruvic acid + NADH → alcohol + CO2 + NAD+

Fermentation Lactic Acid Fermentation pyruvic acid that accumulates from glycolysis  converted to lactic acid regenerates NAD+ so that glycolysis can continue converts glucose into lactic acid equation: pyruvic acid + NADH → lactic acid + NAD+

Fermentation The first part of the equation is glycolysis. Lactic acid fermentation converts glucose into lactic acid. The first part of the equation is glycolysis. The second part shows the conversion of pyruvic acid to lactic acid.

Fermentation The second part shows the conversion of pyruvic acid to lactic acid. Lactic acid fermentation converts glucose into lactic acid. The first part of the equation is glycolysis. The second part shows the conversion of pyruvic acid to lactic acid.

The Totals The complete breakdown of glucose through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP.

Comparing Photosynthesis and Cellular Respiration The energy flows in photosynthesis and cellular respiration take place in opposite directions.

Comparing Photosynthesis and Cellular Respiration On a global level, photosynthesis and cellular respiration are also opposites. Photosynthesis removes carbon dioxide from the atmosphere and cellular respiration puts it back. Photosynthesis releases oxygen into the atmosphere and cellular respiration uses that oxygen to release energy from food.