Bio II Notes 2/11
Bio II Notes 2/11 BIO 1144
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This 4 page Study Guide was uploaded by Rocket on Thursday February 18, 2016. The Study Guide belongs to BIO 1144 at Mississippi State University taught by Thomas Holder in Spring 2016. Since its upload, it has received 34 views.
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Date Created: 02/18/16
Principles of Water + Molecule Movement Physical processes no energy expended 1. Bulk flow : movement of molecules in response to pressure/gravity, high to low 2. Diffusion : movement of molecules along a concentration gradient from high → low concentrations 3. Osmosis : diffusion of water across a selectively permeable membrane, water passes freely through membrane, solutes do not! Transpiration the “cost” land plants pay Ex. Each Individual Corn Plant requires apprx. 55 gallons of water 2% Normal Maintenance (cell elongation/photosynthesis etc.) 98% Transpired Transpiration : the loss of water (vapor form) exiting through stomata of leaves Photosynthesis Leaf Transpiration ❏ Guard Cell Pair: Function: Regulate stomatas; controls water loss Closed→ low in water/ keeps water and oxygen in, CO2 out Open → guard cells full of water (turgid)/ water and oxygen out, CO2 comes in ● Mechanisms: 1. Daytime/Sunlight CO2 low in leaf 2. Guard cells “pump in” Potassium (ATP expended), changes solute(increase) and water concentration(decrease) 3. Water from Xylem moves by osmosis into guard cells → “turgid” (swell) 4. Guard cells swell and open stoma 5. “Pump out” potassium (ATP expended), water moves out, guard cells shrink, closed again Causes of Water Loss Ultimately it’s sunlight energy, heating up leaf causing water to change from into vapor form, which causes evaporation of water from cells Water concentration is lowered in mesophyll, which causes a “pull” of water molecules via osmosis Loss of water from leaf xylem, causes “pull” from stem xylem Root xylem “pulls” water from soil * Transpiration Stream: pathway following transpiration steps* CAT Mechanisms: Once stomata opens, it then becomes a purely physical process “Pulling” of water molecules one at a time C:Cohesion keeps water molecules together A:Adhesion water adheres to cellulose in walls T:Tension “pulling” due to water loss via evaporation from mesophyll * No energy expended “pull” all the way down Translocation Movement of solutes +Similarities between transpiration and translocation: Physical properties of water +Differences Trans L (food/solutes) Trans P (water/minerals) Bidirectional Unidirectional Phloem (short/fat tubes) Xylem (long/slender tubes) Must expenditure of ATP by Plant Sunlight energy (no ATP expenditure by plant) *Food dissolves in water; moved in a form of sucrose Source → Sink Site of excess carbohydrates Storage site/site where sugar is quickly needed Pressure Flow Hypothesis Phloem tissue Sieve tube members companion cells load/unload STMS (ATP expended) At Source: 1. Companion cells “pump” sucrose into STM’s (ATP expenditure) 2. As sucrose concentration increases in STM’s, water potential(pressure) goes down within STM 3. Adjacent xylem tissue has higher water potential than STM’s, water moves into STM’s by osmosis 4. BULK FLOW of Sucrose (higher pressure to lower pressure) At Sink: 1. Companion cells must unload sucrose (ATP expended) 2. Sucrose converted to starch for storage in root cortex 3. Without sucrose, water potential changes, higher water potential in STM 4. Water moves via osmosis from the phloem STM to the adjacent xylem *ATP spent only on companion cells from loading and unloading *No energy expended from movement Bulk Flow (pressure/potential diffs) Osmosis (water concentration diffs) Flowers + Sexual Cycle Flowers only found in angiosperms approx. 300,000 species ❏ Essential processes of Sexual Reproduction occur within flower Meiosis/Cytokinesis: diploid to haploid Syngamy(fertilization) haploid to diploid
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