Bromeliads are CAM plants Pineapple is a bromeliad CAM was discovered in the Crassulaceae, a family of plants that includes jade plant.
Developing and non-photosynthetic sink tissues depend on a supply of reduced carbon from the leaves. In this experiment 32 P was used as a tracer to show which leaves were exporting metabolites via the phloem. What happens in the sink tissues?
Poiseuille's Law of The Flow of Liquids Through a Tube: Schooled in physics and mathematics, Poiseuille developed an improved method for measuring blood pressure. The rate of bulk flow depends on the radius of the tube, the viscosity of the liquid and the pressure gradient. Jean Louis Poiseuille (1799-1869)
Transport in the xylem and phloem is by Bulk Flow, also called mass flow (water through a pipe - usually driven by a pressure gradient). The rate and direction do not depend directly on water potential. Poiseuille's Law radius Volume flow rate = pr 4 8h Dx x DY p viscosity Volume flow rate in m 3 s -1 Pressure gradient
Invertase: enzyme that catalyzes the hydrolysis of sucrose Sucrose is a disaccharide composed of glucose and fructose
How does phloem transport work? Phloem sap movement is driven by positive pressure generated by the accumulation of sugar in the sieve tubes in source tissue. high pressure sieve tube low pressure sucrose H 2 O sucrose H 2 O sucrose glucose H 2 O sucrose H 2 O glucose H 2 O source sink CO 2 + H 2 O sucrose H 2 O parenchyma parenchyma
Content of phloem and xylem exudates Phloem Xylem Sugars 100-300 mg ml -1 0 mg ml -1 Amino acids 5-40 mg ml -1 0.1-2 mg ml -1 Inorganics 1-5 mg ml -1 0.2-4 mg ml -1 Total solutes 250-1200 mmol kg -1 10-100 mmol kg -1 Y s -0.6 to -3 MPa -0.02 to -0.2 MPa ph 7.3-8.0 5.0-6.3 Coke = 39 g of sugar/12 oz = 110 mg ml -1 and ph = 2.5
Respiration - the process of mobilizing organic compounds and oxidizing them. The released energy is transiently stored as ATP. The reduced carbon compounds that are substrates for respiration in plants include glucose, sucrose, fructose-containing polymers, lipids, and organic acids. C 6 H 12 O 6 + 6O 2 --> 6CO 2 + 6H 2 O + 686 kcal energy Steps of respiration: Mobilization Glycolysis TCA (citric acid) cycle or Anaerobic fermentation Electron transport and aerobic phosphorylation
The first step: mobilization. Production of glucose from starch. Glucose can be used to produce sucrose in the cytoplasm and that can be loaded into the phloem and transported to sink tissues such as roots and flowers.
Glycolysis - the first step of respiration. Glucose -> 2 pyruvate + 2 ATP and 2 NADH Glycolysis occurs in the cytoplasm, no carbon is released, only about 20% of the energy available in glucose is obtained.
glucose ENERGY-REQUIRING STEPS OF GLYCOLYSIS: 2 ATP invested glucose 6-phosphate fructose 6-phosphate fructose 1,6-bisphosphate
2 glyceraldehyde 3-phosphate 2 NAD + 2 P i 2 NADH dihydroxyacetone phosphate ENERGY-RELEASING STEPS OF GLYCOLYSIS: 2 1,3-bisphosphoglycerate 2 ADP 2 ATP phosphorylation, 2 ATP produced 2 3-phosphoglycerate 2 2-phosphoglycerate H 2 O 2 PEP 2 ADP 2 ATP phosphorylation, 2 ATP produced 2 pyruvate (to TCA cycle) Net energy yield 2 ATP 2 NADH
The fate of pyruvate depends on whether oxygen is available. If oxygen is not available then pyruvate goes through fermentation to recycle NAD +. The reason is because O 2 is required to use NADH and NAD + is required for glycolysis.
Glycolysis 2 ATP C 6 H 12 O 6 energy input 2 ADP 2 NAD + 4 ATP energy output 2 pyruvate 2 NADH 2 ATP net Alcoholic fermentation 2H 2 O 2CO 2 2 acetaldehyde electrons, hydrogen from NADH 2 ethanol
In the absence of oxygen the energy stored as NADH is used to produce ethanol. In this process only 3% of the energy available in glucose is obtained in 2 moles of ATP formed per mole of glucose. 13% of the energy goes off as heat and 84% is present in the 2 moles of ethanol formed. When oxygen is present the pyruvate goes to the mitochondria where it goes through 1) the TCA cycle, also called the Krebs cycle or citric acid cycle and 2) the electron transport chain.
Cytoplasm glucose energy input Glycolysis 2 ATP (net) 2 NADH 2 pyruvate 2 NADH 2 CO 2 6 NADH 2 FADH 2 TCA Cycle 4 CO 2 2 ATP water Electron transport phosphorylation 32 ATP Mitochondrion oxygen
Pyruvate is decarboxylated to acetyl-coa and NADH is produced. Acetyl CoA enters the TCA cycle. pyruvate from glycolysis NAD + coenzyme A NADH CO 2 CoA acetyl-coa
Function of the TCA cycle: Decarboxylation and production of reduced NADH and FADH 2. These reactions occur in the mitochondrial matrix.
Electron transport in chloroplasts and mitochondia generates ATP in the same way. H + are transported out of the stroma/matrix by during electron transport and H + flow back into the stroma/matrix through the ATP synthase and generates ATP in the stroma matrix. In chloroplasts the thylakoid lumen is acidified. In mitochondria, it is the intermembrane space.
The mitochondrial matrix is equivalent to the chloroplast stroma. Most of the TCA cycle occurs in the matrix and ATP synthesis occurs in the matrix. To make ATP, the electron transport chain drives H + out of the matrix into the intermembrane space. The electron donor is NADH and FADH 2 and the terminal acceptor is O 2.
Oxidative phosphorylation NADH and FADH 2 produced in the TCA cycle are the main electron donors, the ultimate electron acceptor is oxygen. The main product is ATP.
The mitochondrial alternate oxidase (AOX) is used to generate heat. Skunk cabbage is a classic example of a plant that generates heat by thermogenic respiration.
Exam on Tuesday Feb 20, 4:05 PM Multiple choice, 50 questions, bring a No. 2 pencil, no electronic devices allowed. Previous exams and a study guide are available on the course website.