Plants Anatomy, Physiology & Photosynthesis
Plant anatomy Aerial portion absorb light energy gas exchange of O 2, CO 2 & H 2 O stomata (holes) Structural support Terrestrial portion anchorage H 2 O absorption nutrient uptake
Leaf epidermal peel Stomata regulate uptake and release of gases not by pressure but by simple diffusion. In order to exchange gases stomata must remain open and lose large amounts of water. Is this a good strategy? Leaf cross section
Cohesion and adhesion of water! Water moves due to a concentration gradient and negative pressure!
Typical Ranges for Components of Xylem and Phloem Saps in Higher Plants Concentrations (μg ml -1 ) Substance Xylem Phloem Sugars Absent 140,000-210,000 Amino acids 200-1,000 900-10,000 P 70-80 300-550 K 200-800 2,800-4,400 Ca 150-200 80-150 Mg 30-200 100-400 Mn 0.2-6.0 0.9-3.4 Zn 1.5-7.0 8-23 Cu 0.1-2.5 1.0-5.0 B 3.0-6.0 9-11 NO - 3 1,500-2,000 Absent NH + 4 7-60 45-846
What is photosynthesis? The conversion of electromagnetic energy to chemical energy Light photons supply the energy to remove the carbon from carbon dioxide and link them together to form a compound of glucose. light 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 Recall I mentioned that you learned 1 of the 2 most important chemical equations, well this is the other!
1 st Law of thermodynamics Energy can not be created or destroyed; it can only undergo conversion from one form to another Therefore photosynthesis does not create energy
Photosynthesis Process of converting light energy to chemical energy that is useful for biological systems. Almost all energy on this planet uses energy originally derived through the process of photosynthesis.
The Overall Equation for Photosynthesis The reactants and products of the reaction Light energy Carbon dioxide Water Photosynthesis Glucose Oxygen gas Unnumbered Figure 7.1
How plants capture electromagnetic energy Plant pigments absorb light energy chlorophyll a, chlorophyll b, carotenoids Chlorophyll a
Where are the pigments located within a plant cell? chlorophyll within the thylakoid membrane
chemical equation for photosynthesis light 6 CO 2 + 6 H 2 O C 6 H 12 O6 + 6 O 2 Light dependent reactions: 2H 2 O + 2ADP +2P i +2NADP + O 2 + 2ATP + 2NADPH + 2H + Energy from 4 photons of light No CO 2 used O 2 produced as a waste product H H+ and NADPH, electrons from H end up in NADPH NADPH is 2 times greater in energy than ATP
Light independent reactions 6CO 2 C 6 H 12 O 6 + 6 O 2 used in other reactions Energy and 12H Heat Energy Heat 12NADPH 12 NADP + and 18 ATP 18ADP + 18Pi Light dependent reactions + light independent reactions 6CO 2 + 12NADPH +18ATP + 12H 2 O + 12H + C 6 H 12 O 6 + 12NADP + +18PiH 2 O + 18ADP Summary equation again: 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2
Three phases of photosynthesis Sunlight energy captured Using sunlight energy to synthesize ATP (adenosine triphosphate) Using ATP to synthesize organic compounds from carbon dioxide (fixation of inorganic carbon) Bottom line: we went from light energy to electrical energy and then from electrical energy to chemical bond energy.
Why a carbohydrate? If a plant can produce an energetic molecule, like ATP, why bother synthesizing glucose then later convert it back to ATP? PORTABILITY ATP and NADPH are fairly unstable compounds. Imagine trying to send these compounds around without losing energy as they go.
Summary of Photosynthesis cellular respiration cellulose starch other organic compounds
Respiration vs. Photosynthesis? Respiration takes energy stored in the chemical bonds of glucose and converts it to ATP. Photosynthesis takes energy from light and converts it into glucose.
Photosynthesis Respiration: 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 C 6 H 12 O 6 + 6O 2 6CO 2 +6H 2 O C 6 H 12 O 6 + 6O 2 Photosynthesis Respiration Light Energy 6H 2 O + 6CO 2 Heat Energy
You should be able to: Identify the main regions of a plant (roots, stems and leaves) identify their main functions, the structures within each region that help them carry out those functions, and the physical factors that affect each. Explain how the physical environment, particularly water and light availability, can affect plant growth form. Identify the main purpose of photosynthesis. For both the light dependent and light independent reactions be able to identify: The source of energy driving each set of reactions, and where it ends up. The important molecules needed by each set of reactions. The products of each set of reactions. Explain why glucose is a better way of transporting energy than ATP or NADPH Explain the importance of the polarity of water to the process of getting water from the roots to the leaves. Explain the importance of the products of photosynthesis to the process of respiration and vice-versa. Explain the energetic relationship between photosynthesis and respiration.