Transport and Circulation

We’ll be discussing Cellular Transport Plant Tissues and Transport in Plants Trends and Various Strategies Used by Animals to Transport Materials Transport in Man Disorders of the Circulatory System

FACTORS AFFECTING TRANSPORT OF MATERIALS SOLUBILITY OF MOLECULES “LIKE DISSOLVES LIKE” 2. CONCENTRATION 3. SIZE 4. CHARGE 5. TEMPERATURE/PRESSURE/ ENVIRONMENTAL CONDITONS

FLUID MOSAIC MODEL OF A UNIT MEMBRANE

Membranes and cellular transport solubility - “LIKE DISSOLVES LIKE” phosholipids can bridge 2 env’ts and bind H2O-soluble molecules(proteins) to H2O-insoluble mat’ls

Active vs Passive Transport

Transport of large molecules

Summary of Transport Processes Diffusion Osmosis Facilitated Diffusion Pumps Endocytosis/exocytosis Direction High to Low Low to High N/A Transport Mechanism Pores Channels Membrane Energy Required? No Yes Type of particle Small, nonpolar Water Small-medium Ions Small-large Examples of particles CO2, O2 H2O Glucose, fructose, Na+, Ca+2 Na+, K+, H+ Food, waste

Transport within the eukaryotic cell Endomembrane system Endoplasmic reticulum manufacturing and transport facility proteins produced in rough ER are packaged in vesicles Golgi apparatus modification and storage facility receiving end and shipping end Vacuole large membrane bound sacs usually stores undigested nutrients Cyclosis/cytoplasmic streaming

Transport in Plants

Core Concepts Transport at cellular level depends on the selective permeability of membranes. Transport at the cellular level may involve any one or a combination of the following: Passive transport (diffusion, facilitated diffusion, osmosis) through the cell membrane Active transport (e.g. “proton pumps” )through the cell membrane Transport of large molecules involving endocytosis, vesicles, and exocytocis Cyclosis (cytoplasmic streaming Endoplasmic reticulum, Golgi Apparatus, Vacuole Plant Transport Root hairs, mycorrhiza , and a large surface area of cortical cells enhance water and mineral absorption. The waxy Casparian strip of the endodermis regulates movement of water and minerals from the cortex to the stele. Nutrients from the soil and air are transported within a plant by the vascular tissue which are continuous throughout the plant body. Uptake and release of water and solutes by individual cells, such as the absorption of water and minerals from the soil by the root cells. Short distance or lateral transport of minerals and water in the roots either move across the root cortex to the vascular cylinder in 3 ways or a combination of routes: through a continuum of cytosol based on the plasmodesmata which are protoplast connecting channels through walls (symplast). Through a continuum of cell walls and extra cellular spaces (apoplast). by repeated crossing of the plasma membranes and walls of the cells along the pathway (trans-membrane) Long-distance transport of sap is accomplished by the xylem and phloem The xylem vessels and tracheids are the main conducting vessels that move water and minerals to various plant parts as described in the Cohesion-Tension theory. The sieve tubes of the phloem are the main conducting vessels that move food to various plant parts as described in the Pressure Flow Theory.

Vascular tissues: xylem and phloem Tracheids* Vessel elements* Parenchyma cells Fiber Phloem Sieve-tube members Companion cells Sclerenchyma fibers Both are continuous throughout the plant body

Transport occurs on three levels Uptake and release of water and solutes by individual cells Short-distance transport of substances by tissues and organs Long-distance transport of minerals in water and sap within xylem and phloem by the whole plant body

Transport in Plants occurs in three levels: 1. uptake and release of water and solutes by individual cells e.g. absorption of water and minerals from the soil by the root cells. 2. short-distance transport of substances from cell to cell at the level of tissues and organs, e.g. sugar loading from photosynthetic cells of mature leaves into the sieve tubes of phloem 3. long-distance transport of sap e.g. within the xylem and phloem at the level of the whole plant.

A variety of physical processes are involved in the different types of transport Sugars are produced by photosynthesis in the leaves. 5 Through stomata, leaves take in CO2 and expel O2. The CO2 provides carbon for photosynthesis. Some O2 produced by photosynthesis is used in cellular respiration. 4 CO2 O2 Light H2O Sugar Transpiration, the loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upward. 3 Sugars are transported as phloem sap to roots and other parts of the plant. 6 Water and minerals are transported upward from roots to shoots as xylem sap. 2 Roots absorb water and dissolved minerals from soil Root hairs & mycorrhizae increase surface area for absorption 1 Roots exchange gases with the air spaces of soil, taking in O2 and discharging CO2. In cellular respiration, O2 supports the breakdown of sugars. 7 O2 H2O CO2 Minerals

ACTIVE TRANSPORT (USE OF “PUMPS”) TRANSPORT OF IONS AT THE CELLULAR LEVEL DEPENDS ON SELECTIVELY PERMEABLE MEMBRANES Controls the movement of solutes into and out of the cell With specific transport proteins Enable plant cells to maintain an internal environment different from their surroundings

Short-distance H2O transport from the soil to the root xylem occurs through diffusion

Short distance or lateral transport of minerals and water in the roots either move across the root cortex to the vascular cylinder in 3 ways or a combination of routes: through a continuum of cytosol based on the plasmodesmata which are protoplast connecting channels through walls (symplast). Through a continuum of cell walls and extra cellular spaces (apoplast). by repeated crossing of the plasma membranes and walls of the cells along the pathway (trans-membrane)

WATER AND MINERALS ASCEND FROM ROOTS TO SHOOTS THROUGH THE XYLEM ROOT PRESSURE TRANSPIRATION–COHESION–TENSION THEORY Tension – negative pressure

Stomata help regulate the rate of transpiration Lower epidermal tissue Trichomes (“hairs”) Cuticle Upper epidermal tissue Stomata 100 m Stomata help regulate the rate of transpiration Leaves – broad surface areas Increase photosynthesis Increase water loss through stomata (transpiration) Turgid Flaccid

Turgid Flaccid

Translocation – transport of organic molecules in the plant ORGANIC NUTRIENTS ARE TRANSLOCATED THROUGH THE PHLOEM (PRESSURE – FLOW MODEL of PHLOEM SAP TRANSPORT) Vessel (xylem) H2O Sieve tube (phloem) Source cell (leaf) Sucrose Sink cell (storage root) 1 Loading of sugar (green dots) into the sieve tube at the source reduces water potential inside the sieve-tube members. This causes the tube to take up water by osmosis. 2 4 3 This uptake of water generates a positive pressure that forces the sap to flow along the tube. The pressure is relieved by the unloading of sugar and the consequent loss of water from the tube at the sink. In the case of leaf-to-root translocation, xylem recycles water from sink to source. Transpiration stream Pressure flow Translocation – transport of organic molecules in the plant Phloem sap Mostly sucrose Sugar source  sugar sink Source is a producer of sugar Sink is a consumer/storage facility for sugar

Pressure – flow model high solute concentration at sugar source increase in hydrostatic pressure at source end of phloem attracts & draws more H2O from xylem bulk flow of H2O from source end of phloem move sugars towards a sugar sink