1 Movement Across Membranes 2 1. Diffusion 3 DiffusionDiffusion Particles in liquids and gases move in random directions with a certain amount of kinetic

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Movement Across Movement Across MembranesMembranes

Movement Across Movement Across MembranesMembranes

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1. Diffusion1. Diffusion1. Diffusion1. Diffusion

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DiffusionDiffusionDiffusionDiffusion

Particles in liquids Particles in liquids and gases move in and gases move in random directions random directions

with a certain with a certain amount of kinetic amount of kinetic

energyenergy

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The overall effect of this is The overall effect of this is that particles become evenly that particles become evenly distributed in their containerdistributed in their container

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Kinetic Energy can Kinetic Energy can be increased by be increased by increasing the increasing the temperaturetemperature

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Examples:Examples:

• Diffusion of CODiffusion of CO2 2 into stomata of into stomata of leaves during photosynthesis.leaves during photosynthesis.

• Diffusion of ODiffusion of O22 into the alveoli of the into the alveoli of the lungslungs

• Diffusion of ODiffusion of O22 to respiring cells to respiring cells

• Diffusion of glucose, amino acids etc. Diffusion of glucose, amino acids etc. into the villi during digestion.into the villi during digestion.

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2. Osmosis2. Osmosis2. Osmosis2. OsmosisThe cell membrane is The cell membrane is partially partially

permeablepermeable – it allows small, – it allows small, particles to pass through by simple particles to pass through by simple

diffusiondiffusion

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The cell membrane is partially The cell membrane is partially permeable – it allows small, permeable – it allows small,

uncharged or high energy particles uncharged or high energy particles to pass through by simple diffusionto pass through by simple diffusion

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• Osmosis is simply a special case of Osmosis is simply a special case of diffusion…diffusion…

• ……that applies to WATERthat applies to WATER

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Water PotentialWater PotentialWater PotentialWater Potential

‘‘Water potential’ is a measure of Water potential’ is a measure of the amount of kinetic (movement) the amount of kinetic (movement)

energy water molecules haveenergy water molecules have

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Water potential (Water potential () is a measure ) is a measure of the amount of kinetic energy of the amount of kinetic energy

water molecules havewater molecules have

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In pure water at STP, the In pure water at STP, the molecules are given a water molecules are given a water

potential of 0potential of 0

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““Osmosis is the diffusion of water Osmosis is the diffusion of water molecules from areas of high water molecules from areas of high water

potential to areas of lower water potential potential to areas of lower water potential through a partially permeable membrane”through a partially permeable membrane”

OsmosisOsmosisOsmosisOsmosis

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Osmosis is the diffusion of water Osmosis is the diffusion of water molecules from areas of high water molecules from areas of high water

potential to areas of lower water potential potential to areas of lower water potential through a partially permeable membrane.through a partially permeable membrane.

OsmosisOsmosisOsmosisOsmosis

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Osmosis and Animal Osmosis and Animal CellsCellsOsmosis and Animal Osmosis and Animal CellsCells

Cells placed in Cells placed in a solution of a solution of higher water higher water

potentialpotential

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potentialpotentialWaterWater

enters by enters by osmosisosmosis

Cell Cell bursts bursts (lysis)(lysis)

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Cells placed in Cells placed in a solution of a solution of lower water lower water

potentialpotential

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Cells placed in Cells placed in a solution of a solution of lower water lower water

potentialpotential

Water leaves Water leaves by osmosisby osmosis

Cell shrivels Cell shrivels (crenation)(crenation)

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Osmosis and Plant Osmosis and Plant CellsCellsOsmosis and Plant Osmosis and Plant CellsCells


potentialpotential

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potentialpotentialWaterWater

enters by enters by osmosisosmosis

Cell Cell becomes becomes TURGIDTURGID

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Cells placed in a Cells placed in a solution of lower solution of lower water potentialwater potential

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Cells placed in a Cells placed in a solution of lower solution of lower water potentialwater potential

Water leaves Water leaves by osmosisby osmosis

Cell shrivels Cell shrivels (PLASMOLYSED)(PLASMOLYSED)

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These cells are placed in strong These cells are placed in strong sugar solution – would they sugar solution – would they

become turgid or plasmolysed?become turgid or plasmolysed?

plasmolysedplasmolysed

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• When plant cells lose water and When plant cells lose water and plasmolyse…plasmolyse…

• ……the plant is unable to support itself the plant is unable to support itself and starts to WILT.and starts to WILT.

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Osmosis and Plant Osmosis and Plant CellsCellsOsmosis and Plant Osmosis and Plant CellsCellsAnd when And when turgidturgid the cell contents the cell contents exert outward pressure on the cell exert outward pressure on the cell

wallwall

This helps to This helps to supportsupport plants and plants and keep them upright.keep them upright.

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Active TransportActive TransportActive TransportActive TransportActive transport moves Active transport moves

substances substances againstagainst a a concentration gradient.concentration gradient.

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Active TransportActive TransportActive TransportActive TransportMovement involves the Movement involves the

hydrolysis of ATP to supply hydrolysis of ATP to supply energyenergy

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Active TransportActive TransportActive TransportActive TransportStructural changes in the Structural changes in the

carrier proteins result in the carrier proteins result in the movement of materialmovement of material

What is active What is active transport?transport?

Movement of substances in and out of cells by diffusion involves molecules moving down a concentration gradient from high to low concentration.

Sometimes substances move into cells from low to high concentration. This is called active transport.

Active transport needs energy to make it happen.

How do molecules move along the concentration gradient during active transport?

high concentration

low concentration

diffusion active transport

Active transport and Active transport and plantsplants

Plants need mineral elements from the soil for healthy growth. Minerals enter a plant though its roots.

The concentration of minerals in the soil is lower than that inside a root hair cell, so how do minerals enter the root cell?

soil

mineralelement

root hair cell

Active transport and Active transport and plantsplants

Minerals enter a root cell by active transport.

The plant uses energy to move minerals up the concentration gradient from the soil into its root cells.

Why is it important for plants to use energy in this way?

soil

mineralelement

root hair cell

active transport

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Summary:Summary:

• Active Transport is:Active Transport is:

• ““The movement of molecules The movement of molecules AGAINST their concentration AGAINST their concentration gradient, using ENERGY from gradient, using ENERGY from respiration.”respiration.”

• In mammals, nerves and brain cells In mammals, nerves and brain cells carry out Active Transport and use carry out Active Transport and use 1/3 of all the energy in your body!1/3 of all the energy in your body!

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So you could get fit just by So you could get fit just by thinking about it!!thinking about it!!

Salt Glands Salt Glands in marine in marine animalsanimals

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Why is Cyanide such an Why is Cyanide such an effective poison?effective poison?

• MurderMurder::

• Gregor RasputinGregor Rasputin

• Nazi gas Chambers (Zyklon B)Nazi gas Chambers (Zyklon B)

• Irwin RommellIrwin Rommell

• Eva BraunEva Braun

• Hermann GoeringHermann Goering

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Why is Cyanide such an Why is Cyanide such an effective poison?effective poison?• SuicideSuicide::

• Adolf HitlerAdolf Hitler

• Irwin RommellIrwin Rommell

• Hermann GoeringHermann Goering

• Heinrich HimmlerHeinrich Himmler

• Eva BraunEva Braun

• Alan TuringAlan Turing

• Tamil TigersTamil Tigers

What is Cyanide?What is Cyanide?

• Hydrogen Cyanide ( HCN)Hydrogen Cyanide ( HCN)

• Found naturally in apple pips, Found naturally in apple pips, apricot, cherry and peach stones, apricot, cherry and peach stones, clover leaves, elderberrysclover leaves, elderberrys

• Component of cigarette smokeComponent of cigarette smoke

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How does it kill?How does it kill?

• Destroys the final enzyme in the Destroys the final enzyme in the respiration chain ( in mitochondria)respiration chain ( in mitochondria)

• Without ATP energy, active transport Without ATP energy, active transport cannot occurcannot occur

• Without aerobic respiration, brain Without aerobic respiration, brain and heart cells die in 30 seconds.and heart cells die in 30 seconds.

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Jonestown Religious Cult – Jonestown Religious Cult – Mass suicide. 900 dead.Mass suicide. 900 dead.

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Concentrations of ions in a plant cellConcentrations of ions in a plant cell

Fresh waterFresh water

• KK++ 0.10.1

• ClCl-- 1.31.3

• cell membranecell membrane cytoplasmcytoplasm cell wall vacuolecell wall vacuole

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120

65

75

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Compare the ways potassium and chloride ions Compare the ways potassium and chloride ions a) enter the cytoplasm from the water (2)a) enter the cytoplasm from the water (2)b) pass from the cytoplasm into the vacuole (2)b) pass from the cytoplasm into the vacuole (2)

Fresh waterFresh water

• KK++ 0.10.1

• ClCl-- 1.31.3

• cell membranecell membrane cytoplasmcytoplasm cell wall vacuolecell wall vacuole

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120

65

75

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Documents

1 Movement Across Membranes 2 1. Diffusion 3 DiffusionDiffusion Particles in liquids and gases move in random directions with a certain amount of kinetic