Why do organisms need exchange surfaces? • Minerals to maintain water potential and to help enzyme reaction • Nutrients/proteins • Oxygen for aerobic respiration • Water • Glucose as a source of energy • Fats to make membranes and store as energy

They also need exchange surfaces to get rid of waste products • CO2 –Respiration • Urea • Ammonia • Plants get rid of oxygen-photosynthesis • Excretion metabolic waste-waste made in cells

What does a good exchange surface look like? • Large surface area-provides more space for molecules to pass through-achieved by folding walls and membranes • Thin barrier to reduce diffusion distance

Larger organisms need a larger area to exchange more substances

Examples of exchange surfaces • Small intestine- where nutrients are absorbed • Liver- where levels of sugars in blood are adjusted • Root hairs of plants-where water/minerals are absorbed • Hyphae of fungi-nutrients are absorbed

Lungs

Air can pass through the lungs through the nose, along the trachea (windpipe), bronchi and bronchioles. Finally air reaches tiny air filled sacs called alveoli. < Exchange of gases takes place

Lungs are protected by ribs. Movement of the ribs with action of diaphragm (layer of muscle under lungs) help to produce breathing movements (ventilation)

Oxygen passes from the air to alveoli to blood capillaries. Carbon dioxide passes from blood to air in the alveoli

Large surface area: • Space for molecules to pas through • Surface area of lung is 70m2

Barrier permeable to oxygen and carbon dioxide • Plasma membrane that surround cytoplasm of cells are the barrier Thin barrier to reduce diffusion distance: • Alveolus wall