Blood

• Multicellular organisms require transport systems to supply their cells and remove waste products.
• In humans, one of the functions of the circulatory system is to transport substances.
• The heart is a crucial part of the circulatory system.
• Circulation is controlled by the heart rate.
• Blood vessels are a part of the circulatory system.
• White blood cells are a type of blood cell.
• Platelets are a type of blood cell.
• Blood transports materials and distributes heat around the body, and it also helps to protect against disease.
• Blood contains plasma, which is the liquid part of the blood containing useful things like glucose, amino acids, minerals, vitamins (nutrients) and hormones, as well as waste materials such as urea.
• Plasma makes up just over half the volume of blood.
• Red blood cells transport the oxygen required for aerobic respiration.
• Red blood cells are small and flexible so they can fit through narrow blood capillaries.
• Red blood cells are thin, so there is only a short distance for the oxygen to diffuse to reach the centre of the cell.
• Red blood cells lose their nucleus during their development so they can pack in more haemoglobin.
• Oxygen is a gaseous element making up about 20% of the air, which is needed by living organisms for respiration.
• In the lungs, oxygen passes through narrow blood capillaries and is released to respiring cells.
• Red blood cells have adaptations that enable them to carry a maximum amount of oxygen.
• Red blood cells contain the protein haemoglobin, which transports oxygen round the body, giving them their red colour.
• Red blood cells have a biconcave shape, which is the shape of a disc that is curved inwards on both sides, to maximise their surface area for oxygen absorption.
• One of the three main food groups, proteins are needed by the body for cell growth and repair.
• Chromosomes are structures found in the nucleus of most cells.
• Haemoglobin can combine reversibly with oxygen, meaning it can combine with oxygen as blood passes through the lungs, and release the oxygen when it reaches the cells.
• The plural of nucleus is nuclei.