Edexcel IGCSE Biology 复习笔记 2.8.6 Human Transport Systems: Red Blood Cells & Plasma

Edexcel IGCSE Biology 复习笔记 2.8.6 Human Transport Systems: Red Blood Cells & Plasma

Red Blood Cells

 

  • Red blood cells are specialised cells which carry oxygen to respiring cells
  • They are adapted for this function in 3 key ways
    • They are full of haemoglobin, a protein that binds to oxygen to form oxyhaemoglobin
    • They have no nucleus which allows more space for haemoglobin to be packed in
    • The shape of a red blood cell is described as being a 'biconcave disk'  this shape gives them a large surface area to volume ratio to maximise diffusion of oxygen in and out

     

 

 

 

Red-Blood-Cells

 

Red blood cells

 

 

Plasma

 

  • Plasma is a straw coloured liquid which the other components of the blood are suspended within
  • Plasma is important for the transport of many substances including:
    • Carbon dioxide - the waste product of respiration, dissolved in the plasma as hydrogencarbonate ions and transported from respiring cells to the lungs
    • Digested food and mineral ions - dissolved particles absorbed from the small intestine and delivered to requiring cells around the body
    • Urea - the waste substance produced in the breakdown of proteins by the liver. Urea is dissolved in the plasma and transported to the kidneys
    • Hormones - chemical messengers released into the blood from the endocrine organs (glands) and delivered to target tissues/organs of the body
    • Heat energy - created in respiration (an exothermic reaction), heat energy is transferred to cooler parts of the body or to the skin where heat can be lost

转载自savemyexam

更多IGCSE课程
翰林国际教育资讯二维码