Section 8-1 Notes
Energy and Life Energy is the ability to do work. Living things depend on energy. Without the ability to obtain and use energy, life would cease to exist. Where does the energy that living things need come from?
Autotrophs and Heterotrophs Plants and some other types of organisms are able to use light energy from the sun to produce food. Autotrophs are organisms that make their own food. EX: plants Heterotrophs obtain energy from the foods they consume because they cannot use the sun s energy directly.
Chemical Energy All organisms must release the energy in sugars and other compounds. Energy comes in many forms: Light Heat Electricity
Chemical Energy Living things use chemical fuels as well. One of the principal chemical compounds that cells use to store and release energy is adenosine triphosphate (ATP). ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups.
Adenine Ribose 3 Phosphate groups
Storing & Releasing Energy Adenosine diphosphate (ADP) is a compound that looks almost like ATP, except there is only 2 phosphate groups. This difference is the key to the way in which living things store energy. Simply by breaking the bond between the second and third phosphate, energy is released.
ADP ATP
Using Biochemical Energy Cells use the energy provided by ATP to carryout these cellular activities: Active transport Synthesis of proteins Synthesis of nucleic acids Responses to chemical signals Producing light (fireflies)
Using Biochemical Energy Cells have only a small amount of ATP to last them for a few seconds of activity. Cells can regenerate ATP from ADP as needed by using energy in foods like glucose.
Section 8-2 Notes
Photosynthesis The key cellular process identified with energy production is photosynthesis Several scientists investigated the process Van Helmont s Experiment 1643 He concluded that trees gain most of their mass form water
Photosynthesis Priestley s Experiment 1771 Finds that plants release oxygen Jan Ingenhousz 1779 He finds that aquatic plants produce oxygen bubbles in the light but not in dark Concludes that plants need sunlight to produce oxygen
Photosynthesis Equation Light 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high energy sugars and oxygen Plants get CO 2 from the air or water Plants use the sugars to make complex carbohydrates such as starches
Plants also need a source of sunlight and chlorophyll (found in chloroplasts) Plants use molecules called pigments to absorb the light. Main pigment is chlorophyll Two types Chlorophyll a Chlorophyll b
When chlorophyll absorbs light, the energy is sent to the electrons in the chlorophyll molecules This raises the energy levels of the electrons These high energy electrons make photosynthesis work
Chlorophyll absorbs blue-violet and red light from the visible light spectrum (fig.8-5) Chlorophyll does not absorb light in the green region well. Plants look green because the leaves reflect the green light.
Section 8-3 Notes
Inside a Chloroplast Photosynthesis takes place inside chloroplasts. Chloroplasts contain saclike membranes called thylakoids. Thylakoids are arranged in stacks known as grana. Proteins organize chlorophyll and other pigments into clusters known as photosystems.
Inside a Chloroplast The reactions of photosynthesis are in two parts: 1.) Light dependent reactions-take place within the thylakoid membrane. 2.) Light independent reactions (Calvin cycle)- take place in the stroma, the region outside the membrane.
Light Water CO 2 O 2 Sugars
Electron Carriers Cells use electron carriers to transport high-energy electrons from chlorophyll to other molecules. This process is called electron transport. One of these carrier molecules is a compound known as NADP +.
Electron Carriers NADP + accepts and holds 2 high-energy electrons along with a hydrogen ion (H + ). This converts the NADP + into NADPH and energy can be trapped in chemical form. The NADPH can then carry high-energy electrons to chemical reactions elsewhere in the cell.
Light-Dependent Reactions There are five steps: A) Photo system II- Light absorbed is used to break up water molecules into energized electrons, hydrogen and oxygen. B) Electron Transport Chain- High energy electrons from A move through the electron transport chain to photosystem I.
Light-Dependent Reactions C) Photo system I- Electrons released by A are energized again here. Enzymes in the membrane use the electrons to form NADPH. NADPH is used to make sugar in the Calvin cycle. D) Hydrogen Ion Movement- The inside to the membrane fills up with positively charged hydrogen ions. E) ATP Formation- As hydrogen ions pass through ATP synthase, their energy is used to covert ADP into ATP.
Light Independent Reactions There are four steps: A) CO 2 Enters the Cycle- six carbon dioxide molecules are combined with six 5-carbon molecules to produce twelve 3-carbon molecules. B) Energy Input- Energy from ATP and high-energy electrons from NADPH are used to convert the twelve 3-carbon molecules into higher-energy forms.
C) 6-Carbon Sugar Produced- Two 3- carbon molecules are removed from the cycle to produce sugars, lipids, amino acids, and other compounds. D) 5-Carbon Molecules Regenerated- The 10 remaining 3-carbon molecules are converted back in to six 5-carbon molecules, which are used in the next cycle.
Factors Affecting Photosynthesis A shortage of water can stop or slow the process. Temperature of the enzymes needs to be between 0 o C and 35 o C. The intensity of light.