KS 4 Biology Movement In and Out of

KS 4 Biology • Movement • In and Out of Cells 1 of 44 © Boardworks Ltd 2004

Contents Movement In and Out of Cells What is diffusion? Diffusion and life processes Active transport Osmosis Experiments: diffusion and osmosis Multiple-choice quiz 2 of 44 © Boardworks Ltd 2004

Smells and liquids spreading out Why can you smell cooked food from a distance? Why does the colour of concentrated fruit drink change when it is added to water? Why can you smell perfume or aftershave when someone walks past you? 3 of 44 © Boardworks Ltd 2004

Smells and liquids spreading out Smelling cooked food or perfume and diluting juice in water all involve things moving around and spreading out. These processes are all examples of diffusion. Diffusion involves the movement of molecules. What type of molecules are moving in these examples? 4 of 44 © Boardworks Ltd 2004

Moving molecules The molecules in every substance are always moving. In which state are molecules able to spread out? ice (solid) water (liquid) water vapour (gas) Diffusion involves the movement of gas and dissolved molecules. Why don’t solid molecules diffuse? 5 of 44 © Boardworks Ltd 2004

Diffusion and changing concentrations When smelling body spray where is the smell strongest and where is the smell weakest? Smell is strongest at source. Diffusion means the smell spreads out and gets weaker further away from the source. How does the concentration of smell molecules change during diffusion? Smell molecules move from an area of high concentration to an area of lower concentration. This is called a concentration gradient. 6 of 44 © Boardworks Ltd 2004

Changing concentrations Diffusion can be represented on a simple diagram. Where will the molecules be after diffusion? before diffusion after diffusion What has happened to the concentration of the molecules? Diffusion is the movement of gas or dissolved molecules from higher to lower concentration. Molecules diffuse down a concentration gradient. What does this mean? 7 of 44 © Boardworks Ltd 2004

Diffusion animation 1 8 of 44 © Boardworks Ltd 2004

Diffusion animation 2 9 of 44 © Boardworks Ltd 2004

Diffusion animation 3 10 of 44 © Boardworks Ltd 2004

Contents Movement In and Out of Cells What is diffusion? Diffusion and life processes Active transport Osmosis Experiments: diffusion and osmosis Multiple-choice quiz 11 of 44 © Boardworks Ltd 2004

Why is diffusion so important? Diffusion explains why you can smelly smells and what happens when you dilute a concentrated fruit drink. More importantly, diffusion is an essential process that is going on inside your body right now and keeping you alive! Diffusion occurs in the organ systems that control your breathing, circulation, digestion and other life processes. 12 of 44 © Boardworks Ltd 2004

Diffusion and life processes Diffusion is the movement of gas or dissolved molecules. What gas and dissolved molecules do body cells need? Your body’s survival depends on oxygen and dissolved food molecules getting into your cells. How do these vital substances cross boundaries within the body to get to where they are needed? Oxygen and dissolved food molecules must diffuse into and out of the blood for transportation around the body. Where does diffusion take place within the body? 13 of 44 © Boardworks Ltd 2004

Diffusion and breathing Breathing involves the exchange of gases in the lungs, a process which occurs by diffusion. What is the vital gas that you breathe in? oxygen What is the waste gas that you breathe out? carbon dioxide The lungs have a huge surface area to maximize the exchange of oxygen and carbon dioxide with each breath. Where in the lungs does gas exchange take place? 14 of 44 © Boardworks Ltd 2004

Diffusion and breathing Gas exchange takes place in the alveoli, the tiny air sacs at the end of the bronchioles. What are these blood vessels around each alveolus called? 15 of 44 © Boardworks Ltd 2004

Diffusion and breathing – oxygen Inhaling increases the concentration of oxygen molecules in an alveolus. At this point, how does this compare with the concentration of oxygen in deoxygenated blood in the capillary? When you inhale, the concentration of oxygen inside each alveolus is higher than in deoxygenated blood from the body oxygen into alveoli oxygenated blood to the body 16 of 44 © Boardworks Ltd 2004

Diffusion and breathing – oxygen How is the concentration of oxygen in the blood increased? Oxygen molecules diffuse across the lining of the alveolus into the blood in the capillary, moving from higher to lower concentration. diffusion When you inhale, the concentration of oxygen inside each alveolus is higher than in deoxygenated blood from the body oxygen into alveoli oxygenated blood to the body 17 of 44 © Boardworks Ltd 2004

Diffusion and breathing – carbon dioxide Deoxygenated blood from the body is low in oxygen but has high levels of carbon dioxide. How does this compare with concentration of carbon dioxide in the alveolus? The concentration of carbon dioxide in deoxygenated blood is higher than in deoxygenated blood from the body oxygenated blood to the body 18 of 44 © Boardworks Ltd 2004

Diffusion and breathing – carbon dioxide How is the concentration of carbon dioxide in the blood reduced? Carbon dioxide molecules diffuse from the blood in the capillary into the alveolus, moving from higher to lower concentration. diffusion The concentration of carbon dioxide in deoxygenated blood is higher than in deoxygenated blood from the body carbon dioxide out of alveoli oxygenated blood to the body 19 of 44 © Boardworks Ltd 2004

Gas exchange animation 20 of 44 © Boardworks Ltd 2004

Diffusion and digestion Carbohydrates, proteins and fat are made up of large molecules that cannot be used directly by the body. Digestion breaks large food molecules into smaller molecules that can be used by the body. Dissolved food molecules then need to be transported from the small intestine into the bloodstream. Where in the small intestine does this diffusion take place? 21 of 44 © Boardworks Ltd 2004

Inside the small intestine 22 of 44 © Boardworks Ltd 2004

Cross-section of a villus Each villus separates the digested food in the small intestine from a network of capillaries. 23 of 44 © Boardworks Ltd 2004

Diffusion from the small intestine Each villus has a surface layer that is one cell thick. How does the concentration of dissolved food molecules in the small intestine compare with the blood entering a villus? The concentration of dissolved food molecules is higher in the small intestine than in the blood entering the villus. blood entering villus wall of small intestine 24 of 44 inside the small intestine blood leaving villus © Boardworks Ltd 2004

Diffusion from the small intestine How is the concentration of dissolved food molecules in the blood increased? Dissolved food molecules diffuse from the small intestine into the blood, moving from higher to lower concentration. The concentration of dissolved food molecules is higher in the small intestine than in the blood entering the villus. blood entering villus wall of small intestine 25 of 44 inside the small intestine diffusion blood leaving villus © Boardworks Ltd 2004

Diffusion in and out of cells Oxygen and dissolved food molecules are transported to the body’s cells in the bloodstream. How does the concentration of these useful substances in the blood compare with the concentration inside the cells? The concentration of oxygen and dissolved food molecules is higher in the blood arriving at the cells than inside the cells. 26 of 44 © Boardworks Ltd 2004

Diffusion in and out of cells How do oxygen and dissolved food molecules pass from the blood into the cells? Oxygen and dissolved food molecules diffuse into the body cells, moving from higher to lower concentration. diffusion The concentration of oxygen and dissolved food molecules is higher in the blood arriving at the cells than inside the cells. What process involving these useful substances takes place inside the cell? 27 of 44 © Boardworks Ltd 2004

Diffusion in and out of cells The cells use the food and oxygen for respiration. Carbon dioxide is the waste product of respiration and will poison a cell if it is not removed. How is it removed? diffusion Carbon dioxide molecules diffuse from the cells into the bloodstream, moving from higher to lower concentration. How is this waste carbon dioxide removed from the body? 28 of 44 © Boardworks Ltd 2004

Contents Movement In and Out of Cells What is diffusion? Diffusion and life processes Active transport Osmosis Experiments: diffusion and osmosis Multiple-choice quiz 29 of 44 © Boardworks Ltd 2004

What is active transport? Movement of substances in and out of cells by diffusion involves molecules moving down a 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 energy to make it happen. How do molecules move along the concentration gradient during active transport? 30 of 44 © Boardworks Ltd 2004

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 lower than that inside a root hair cell, so how do minerals enter the root cell? root hair cell mineral element soil 31 of 44 © Boardworks Ltd 2004

Active transport and plants 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? active transport root hair cell mineral element soil 32 of 44 © Boardworks Ltd 2004

Contents Movement In and Out of Cells What is diffusion? Diffusion and life processes Active transport Osmosis Experiments: diffusion and osmosis Multiple-choice quiz 33 of 44 © Boardworks Ltd 2004

What is osmosis? Osmosis is a special type of diffusion. Diffusion involves gas or dissolved molecules, but osmosis only involves the movement of water molecules. water molecule Osmosis occurs across a semipermeable membrane which has tiny holes in it. These holes are small enough for water molecules to pass through but larger molecules cannot pass through. 34 of 44 © Boardworks Ltd 2004

What happens during osmosis? Osmosis is a type of diffusion, so what do you think happens to water molecules during this process? osmosis water molecule semipermeable membrane Osmosis is the movement of water molecules from a region of high water concentration to a region of low water concentration across a semipermeable membrane. 35 of 44 © Boardworks Ltd 2004

Osmosis experiment A bag made from a semipermeable membrane is tied to a glass tube and filled with a strong sugar solution. This bag is placed in a weak sugar solution. strong sugar solution weak sugar solution What happens to the water molecules in the weak solution? What happens to the liquid inside the semipermeable bag? 36 of 44 © Boardworks Ltd 2004

Osmosis experiment The volume of liquid in the semipermeable bag increases. The liquid rises up the glass tube and then stops. Why does this happen? strong sugar solution weak sugar solution Water molecules diffuse across the membrane from the weak sugar solution into the strong sugar solution. This continues until the concentration is the same on both sides of the membrane. 37 of 44 © Boardworks Ltd 2004

Osmosis animation 1 38 of 44 © Boardworks Ltd 2004

Osmosis animation 2 39 of 44 © Boardworks Ltd 2004

Contents Movement In and Out of Cells What is diffusion? Diffusion and life processes Active transport Osmosis Experiments: diffusion and osmosis Multiple-choice quiz 40 of 44 © Boardworks Ltd 2004

Experiment to demonstrate diffusion 41 of 44 © Boardworks Ltd 2004

Experiment to investigate osmosis 42 of 44 © Boardworks Ltd 2004

Contents Movement In and Out of Cells What is diffusion? Diffusion and life processes Active transport Osmosis Experiments: diffusion and osmosis Multiple-choice quiz 43 of 44 © Boardworks Ltd 2004

Multiple-choice quiz 44 of 44 © Boardworks Ltd 2004