Movement Across Membranes 1 1 Diffusion 2 Diffusion

Movement Across Membranes 1

1. Diffusion 2

Diffusion Particles in liquids and gases move in random directions with a certain amount of kinetic energy 3

Diffusion The overall effect of this is that particles become evenly distributed in their container 4

Diffusion Kinetic Energy can be increased by increasing the temperature 5

Examples: • Diffusion of CO 2 into stomata of leaves during photosynthesis. • Diffusion of O 2 into the alveoli of the lungs • Diffusion of O 2 to respiring cells • Diffusion of glucose, amino acids etc. into the villi during digestion. 6

2. Osmosis The cell membrane is partially permeable – it allows small, particles to pass through by simple diffusion 7

The cell membrane is partially permeable – it allows small, uncharged or high energy particles to pass through by simple diffusion 8

• Osmosis is simply a special case of diffusion… • …that applies to WATER 9

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Water Potential ‘Water potential’ is a measure of the amount of kinetic (movement) energy water molecules have 13

Water Potential Water potential (y) is a measure of the amount of kinetic energy water molecules have 14

Water Potential In pure water at STP, the molecules are given a water potential of 0 15

Osmosis “Osmosis is the diffusion of water molecules from areas of high water potential to areas of lower water potential through a partially permeable membrane” 16

Osmosis is the diffusion of water molecules from areas of high water potential to areas of lower water potential through a partially permeable membrane. 17

Osmosis and Animal Cel Cells placed in a solution of higher water potential 18

Osmosis and Animal Cel Cells placed in a solution of higher water potential Water enters by osmosis Cell bursts (lysis) 19

Osmosis and Animal Cel Cells placed in a solution of lower water potential 20

Osmosis and Animal Cel Water leaves by osmosis Cells placed in a solution of lower water potential Cell shrivels (crenation) 21

Osmosis and Plant Cells placed in a solution of higher water potential 22

Osmosis and Plant Cells placed in a solution of higher water potential Cell Water becomes enters by TURGID osmosis 23

Osmosis and Plant Cells placed in a solution of lower water potential 24

Osmosis and Plant Cells placed in a solution of lower water potential Cell shrivels (PLASMOLYSED) Water leaves by osmosis 25

Osmosis and Plant Cells These cells are placed in strong sugar solution – would they become turgid or plasmolysed? plasmolysed 26

• When plant cells lose water and plasmolyse… • …the plant is unable to support itself and starts to WILT. 27

Osmosis and Plant Cells And when turgid the cell contents exert outward pressure on the cell wall This helps to support plants and keep them upright. 28

Osmosis and Plant Cells 29

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Active Transport Active transport moves substances against a concentration gradient. 31

Active Transport Movement involves the hydrolysis of ATP to supply energy 32

Active Transport Structural changes in the carrier proteins result in the movement of material 33

What is active transport? Movement of substances in and out of cells by diffusioninvolves molecules moving downa concentration gradient from high to low concentration. high concentration diffusion active transport low concentration Sometimes substances move into cells from low to high concentration. This is called active transport. Active transport needs energyto make it happen. How do molecules move along the concentration gradient during active transport?

Active transport and plants 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 lowerthan that inside a root hair cell, so how do minerals enter the root cell? root hair cell mineral element soil

Active transport and plants The plant uses energy to move minerals up the concentration gradient from Minerals enter a root cell by active transport. the soil into its root cells. Why is it important for plants to use energy in this way? active transport root hair cell mineral element soil

Summary: • Active Transport is: • “The movement of molecules AGAINST their concentration gradient, using ENERGY from respiration. ” • In mammals, nerves and brain cells carry out Active Transport and use 1/3 of all the energy in your body! 37

So you could get fit just by thinking about it!! 38

Salt Glands in marine animals 39

Why is Cyanide such an effective poison? • Murder: • Gregor Rasputin • Nazi gas Chambers (Zyklon B) • Irwin Rommell • Eva Braun • Hermann Goering 40

Why is Cyanide such an effective poison? • Suicide: • Adolf Hitler • Irwin Rommell • Hermann Goering • Heinrich Himmler • Eva Braun • Alan Turing • Tamil Tigers 41

What is Cyanide? • Hydrogen Cyanide ( HCN) • Found naturally in apple pips, apricot, cherry and peach stones, clover leaves, elderberrys • Component of cigarette smoke 42

How does it kill? • Destroys the final enzyme in the respiration chain ( in mitochondria) • Without ATP energy, active transport cannot occur • Without aerobic respiration, brain and heart cells die in 30 seconds. 43

Jonestown Religious Cult – Mass suicide. 900 dead. 44

Concentrations of ions in a plant cell Fresh water • K+ 0. 1 120 75 • Cl- 1. 3 65 106 • cell membrane cytoplasm cell wall vacuole 45

Compare the ways potassium and chloride ions a) enter the cytoplasm from the water (2) b) pass from the cytoplasm into the vacuole (2) Fresh water • K+ 0. 1 120 75 • Cl- 1. 3 65 106 • cell membrane cytoplasm cell wall vacuole 46