Special Features of Plant Cells Lecture 11 Know that all plant cells have plastids organelle in cells of certain groups of eukaryotes that is the site of such activities as food manufacture and storage plastids are bounded by two membranes that the plastid can be modified for several specialized functions chloroplasts for photosynthesis amyloplasts for storage of starch and also senses gravity and chromoplasts for storage of carotenoid pigments The cell wall provides structural support there are two types of cell walls primary cell wall are found in plant cells that are growing enlarging when cell growth has ceased some plant cells lay down a secondary cell wall Know the model of the structure of the primary cell wall rods of cellulose mibrofibrils embedded in a matrix of other shorter chain polysaccharides that the primary cell wall can be stretched and enlarged to accommodate cell growth Know that secondary walls are composed of approximately equal parts Cellulose microfibrils and lignin The lignin is composed of phenolic compounds that are polymerized into a matrix that is a stiff rigid glue Once the secondary wall has been formed the cell can no longer grow Secondary walls are found in collenchyma cells tracheids vessel elements and fibers sclerids Plant cells have a large central vacuole containing a concentrated solution of potassium salts The primary function of the central vacuole is to generate turgor pressure a positive internal hydrostatic pressure which keeps plant cells rigid and provides the driving force for plant cell enlargement Plasmodesmata are cytoplasmic connections between neighboring plant cells Plasmodesmata permit the movement of small molecules between plant cells Proteins and RNAs can also be actively transported through plasmodesmata Lecture 12 photosynthesis You should be able to write a chemical equation that describes photosynthesis know that it occurs in two separate reactions the light rxn and the Calvin cycle The light rxn takes place on the thylakoid membranes and light captured by chlorophyll leads to electron transport and finally to the formation of ATP from ADP and the reduction of NADP to NADPH The Calvin cycle takes place in the stroma of the chloroplast and fixes CO2 into carbohydrates using ATP and NADPH produced by the light reactions Know the difference between and action spectrum and an absorption spectrum and what the roles of chlorophyll b and carotenoids are in photosynthesis Know that the enzyme that carries out CO2 fixation is Rubisco and this enzyme converts a 5 carbon sugar RuBP into two 3 carbon sugars PGA Six turns of the Calvin cycle are needed to make one glucose Excess glucose can be stored as starch Know what photorespiration is why it is a problem and under what conditions it occurs photorespiration is the process by which RuBP sugar has oxygen added to it by enzyme Rubisco instead of CO2 during normal photosynthesis This occurs when CO2 to O2 levels are low and photorespiration works to produce more CO2 due to this deficiency Photosynthesis occurs when the CO2 to O2 levels are high limiting photorespiration Be able to explain the differences between the photosynthetic schemes of C3 plants C4 plants and CAM plants and the advantages of each C3 plants Fix CO2 into 2 molecules of PGA a 3 carbon compound When the temperature is high C3 plants suffer from photorespiration C4 plants Nature s solution to photorespiration problem Fixes CO2 into a 4 carbon compound malate CO2 to O2 levels are high promoting photosynthesis and limiting photorespiration C4 plants make malate in mesophyll cells site of CO2 fixation which are transported to the bundle sheath cells site of Calvin cycle where CO2 released enters the Calvin cycle ultimately yielding sugars and starch spatial separation mesophyll and bundle sheath cells more efficient than C3 plants at high temps and moderately dry conditions CAM plants A C4 modification temporal separation time night and day of CO2 fixation and calvin cycle use malate to fix CO2 stored in the vacuole as malic acid aka Crassulacean Acid opening closing of stomates in CAM plants opposite compared to C4 plants CAM plants at night stomates are open CO2 is fixed into malate at day stomates are closed CO2 released from malate and Calvin cycle operates Save H2O grow in dry and hot areas pactus and pineapples Objectives for Lecture 13 Plant nutrition Know what nutrients are and the difference between macronutrients and micronutrients Know that carbon hydrogen oxygen nitrogen phosphorus potassium and calcium are macronutrients Know that the amount of nitrogen phosphorus and potassium are often limiting for plant growth that nitrogen in the soil is mostly in the form of nitrate which quickly leaches from the soil Know that mineral ion uptake requires active transport and that most ion and water uptake occurs through the youngest parts of roots including the root hairs which greatly increase the surface area of the root Know what the terms apoplast and symplast refer to Understand the role of the endodermis in allowing plants to maintain mineral ion concentrations in the xylem that are higher than in the surrounding soil Know what the casperian strip is where it is located and its role in mineral ion uptake Casparian strip located on cell wall of endodermis Know what the terms apoplast and symplast refer to Understand the role of the endodermis in allowing plants to maintain mineral ion concentrations in the xylem that are higher than in the surrounding soil Apoplastic route diffusion through cell walls symplastic route uptake in the cytoplasm of a cell and movement from cell to cell via plasmodesmata Transcellular route uptake in the cytoplasm of a cell and movement from cell to cell across plasma membrane For the apoplastic pathways before entering the vascular cylinder nutrients must enter the cytoplasm of a cell to pass through the endodermis The cell walls of the endodermis have a water tight waxy layer Casparian strips that forces minerals and water to enter the cytoplasm This allows the mineral content of the xylem to be regulated and maintained at a higher concentration than in the soil Be able to outline the nitrogen cycle understand the terms nitrogen fixation nitrification ammonification denitrification and know what the precursor and product is in each of these reactions know that each of these reactions is carried out only by bacteria nitrogen fixation incorporation of atmospheric nitrogen into
View Full Document
Unlocking...