Chap3 movement of substances

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Chap3 movement of substances

Chap3 movement of substances

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  • Natural = plasma membrane, tonoplast Artificial = visking tubing, cellophane paper
  • Both osmosis and diffusion taking place.

Chap3 movement of substances Chap3 movement of substances Presentation Transcript

  • Chapter 3: Movement of Substances
  • Lesson Objectives (a) define diffusion and discuss its importance in nutrient uptake and gaseous exchange in plants and humans. (b) define osmosis and discuss the effects of osmosis on plant and animal tissues. (c) define active transport and discuss its importance as an energy-consuming process by which substances are transported against a concentration gradient, as in ion uptake by root hairs and uptake of glucose by cells in the villi.
  • Methods of Transport Across Membranes 1. Diffusion 2. Osmosis 3. Active Transport
  • What did we observe?
  • 3.1 Diffusion • substances will move from where it is more concentrated to where it is less concentrated, down its concentration gradient. • Diffusion is defined as the random movement of particles down a concentration gradient • Energy is not required
  • 3.1 Diffusion • Concentration gradient = The difference in concentration between two regions • The steeper the concentration for a substance, the faster the rate of diffusion
  • 3.1 Diffusion • Each substance diffuses down its own concentration gradient, independent of the concentration gradients of other substances.
  • Thinking Questions! • What is (i) a natural and (ii) an artificial example of a partially permeable membrane? • Can diffusion occur across a partially permeable membrane? • Can all particles move across a partially permeable membrane?
  • Research Questions! • Describe how diffusion occurs in animals. a) movement of food substances across the walls of small intestines into blood b) movement of dissolved food substances and oxygen from blood into tissue fluid and into cells c) movement of carbon dioxide from blood into air spaces (in the lungs) and vice versa for oxygen
  • Research Questions! • Describe how diffusion occurs in plants. a) movement of carbon dioxide into the leaf through the stomata during the day and vice versa for oxygen at night b) movement of water vapour out of the leaf through the stomata during transpiration c) movement of mineral salts into the root hair cells
  • Factors that increases rate of diffusion Conditions which increase the rate of diffusion (1) Steeper concentration gradient (2) The shorter the distance over which diffusion occurs, the faster the diffusion rate (3) Greater surface area to volume ratio (4) Larger number of pores and greater numbers of pores (if partially permeable membrane is present) (5) Smaller and lighter molecules (6) The higher the temperature, the greater the speed of motion of the particles
  • 3.2 Osmosis
  • 3.2 Osmosis • Water molecules will move from where it is more concentrated to where it is less concentrated, down its water potential gradient. • Osmosis is defined as the NET movement of water molecules down a water potential gradient across a partially permeable membrane
  • 3.2 Osmosis • Water potential = a measure of the tendency of water molecules to move from one place to another • direction of osmosis is determined only by a difference in total solute concentration
  • 3.2 Osmosis – Types of solutions • 3 types of solutions: – solution with the higher concentration of solutes is hypertonic. – solution with the lower concentration of solutes is hypotonic. – Solutions with equal solute concentrations are isotonic
  • How does osmosis affects cells?
  • How does osmosis affects cells?
  • How does osmosis affects cells?
  • How does osmosis affects cells?
  • How does osmosis affects cells?
  • How does osmosis affects cells?
  • Importance of Turgor pressure • Helps to support the soft tissues of plants so that they remain firm • Absence of turgor in cells results in plant cells becoming flaccid (soft)  plant will wilt • Causes the opening and closing of the stomata • Causes the opening and closing of flowers
  • How does osmosis affects cells?
  • Active Transport • Substances move against their concentration gradient, from the side where they are less concentrated to where they are more concentrated. • Requires ENERGY
  • Comparing Diffusion and Active Transport
  • Research Questions! • Describe where active transport occurs in humans. a) in small intestine during the uptake of food substances • Describe where active transport occurs in plants. a) in roots during the uptake of mineral salts
  • Processes Diffusion Osmosis • Refers only to water molecules • Takes place across a partially permeable membrane Similarities • Energy not required • Movement of substances down a concentration gradient • Refers to any substance, gaseous or liquid • Membrane is not required Movement of Substances Into or Out of Cells Differences
  • Movement of particles (molecules or ions) against a concentration gradient. Energy is required. Movement of particles (molecules or ions) down a concentration gradient. Processes Diffusion Osmosis Net movement of water molecules across a partially permeable membrane, from a solution of higher water potential to a solution of lower water potential. Active Transport Movement of Substances Into or Out of Cells
  • Thinking Question • Give students a teabag in water scenario. Ask them what happens?
  • Scenario 1 It was a fine sunny day, and Mr Q was driving to work as usual. He was drinking his favorite icy cold Coke drink when… Suddenly!!! A car came from nowhere and bang into Mr Q’s car! !!!!!!!!!! One of Mr Q’s finger was CHOPPED OFF! You happen to walk past, and full of integrity (hopefully..), you ran as fast as you can to his help! You quickly throw his severed finger into the drink to preserve the finger, so that the doctor can mend it back. Is this the right thing to do? Why???
  • Scenario 2 It was a fine sunny day, and Mr Viresh was out sun-tanning in his yacht. Suddenly!!! A strong gush of tsunami came and blew his yacht far far away! !!!!!!!! Mr V landed on a deserted island with no one but himself!!! He peed so much out of fear that he feels so dehydrated… He started drinking the seawater to hydate himself. Is that the right thing to do??? Why???