AQA GCSE Biology B3

AQA GCSE Biology B3 What is Osmosis? It is the diffusion of water through a semi (partially) permeable membrane. the movement of water molecules from an area of high concentration to low. What are Isotonic drinks (sports drinks)? Isotonic drink are drinks that contains a similar level of sugar, ions and water of that of human body. The sugar replaces the amount of sugar released during exercise, and the water and ions replaces the water and ions that are lost via sweating. What two ways are materials exchanged in humans? 1) Villi in the small intestine 2) Alveoli in the lungs What makes the villi so effective at exchanging materials in humans? It has a large surface area. It also has an extensive network of blood capillaries which help absorb products of digestion. The capillaries help to maintain the concentration gradient. Capillaries have very thin walls, why is this good for exchange of materials in the human body? It is good as it provides a short diffusion path. What are Alveoli's? Are at the end of each bronchiole there is an area that leads to little clumps of tiny air sacks where the exchange of carbon dioxide and oxygen takes place. What maximizes the exchange in the alveoli? Large surface area (due to there being millions of alveoli in the lungs) so there is larger surface area for the exchange of materials. They have an excellent supply of blood due to the capillaries being so close to the surface (short diffusion pathway). How are substances exchanged in the alveoli? by diffusion What diffuses in and out of the alveoli? Carbon dioxide diffuses out from the blood into the alveoli. Oxygen diffuses in to the blood from the alveoli. What happens to the rib-cage and diaphragm during inspiration (breathing in)? The ribs move up and out due to the intercostal muscle contracting. The diaphragm also contracts and flattens. What happens to the rib-cage and diaphragm during expiration (breathing out)? The rib cages move down and in as the intercostal muscle relaxes. The diaphragm also relaxes but moves upwards. What does the stomata allow? Allows the exchange of carbon dioxide and oxygen by diffusion. It also allows the loss of water vapour. What is transpiration? Is the loss of water vapour from the stomata in a plant What is the prime condition for Transpiration? A warm, dry and windy condition. How does light affect Transpiration? Transpiration increases in bright light as the stomata opens wider in increased light. Why is transpiration faster in high temperatures? Because evaporation and diffusion are faster in higher temperatures causing more water to be lost via the stomata increasing and speeding up transpiration. Why is transpiration faster in windy conditions? Because water vapour is removed quicker by the wind, speeding up diffusion of more water vapour. Why is transpiration slower in humid conditions? It is slower as in humid condition there is a high concentration of water vapour present in the air and in the plant slowing down diffusion. If the loss of water is faster than the rate at which it is being replaced by the roots in a plant what happens? The guard cells surrounding the stomata close up the stomata and prevent any more water loss (transpiration) and also stop photosynthesis as Co2 cannot enter the leaves. What does the roots absorb form the soil? Water and ions What helps to increase the roots surface area? Root hairs What is the job of the Xylem? Movement of water through a plant - from its roots to its leaves via the stem. Explain the process of how the water reaches the Xylem and leaves the leaves? Water is absorbed from the soil through root hair cells by osmosis. It is transported through the xylem vessels up the stem to the leaves. It then evaporates from the leaves (transpiration). What is the job of the phloem? Transport dissolved sugars from the leaves to the rest of the plant. What does the heart do? Pumps blood around the body What does the blood do? Carries the substances around the body What does the arteries do? They carry the blood away from the heart Artery (diagram) (Insert) What does the veins do? Return blood to the heart Veins (diagram) (insert) What are capillaries? They are tiny blood vessels that are close to the body's cells where