active transport / diffusion / osmosis

• Active transport


  Moves substances from a low to a high concentration against the concentration gradient
• Active transport needs energy which comes from respiration
• Active transport examples

  • Root hair cells absorb mineral ions which are in a low concentration in the soil
  • Sugar is absorbed from a low concentration in small intestine, into the blood which has a higher sugar concentration
• Plants need ions for healthy growth
• Sugar molecules are used for cell respiration
• Diffusion takes place in other areas of our bodies and the bodies of plants


  For example: in our lungs, the small intestine, the leaves and roots of plants
• Factors that speed up the rate of diffusion include temperature, concentration gradient, surface area, and the permeability of the membrane
• Stem cell


  An undifferentiated cell which can become another type of cell
• Sources of stem cells in humans

  • Embryos
  • Adult stem cells
• Embryonic stem cells


  • Can become most other types of cells, can be used to treat diseases/conditions, but are rejected by the body and raise ethical concerns
• Adult stem cells


  • Can form some other types of cells, not rejected by the body, but can cause transfer of viruses and can differentiate into fewer types of cells than embryos
• Plant stem cells


  Meristem tissue can differentiate into any other type of plant cell at any point in the plant's life
• Advantages of plant stem cells

  • Can clone rare plants to stop them from going extinct
  • Can clone plants with special features like disease resistance or nice tasting fruit
• Mitosis


  1. DNA replicates to make 2 copies of each chromosome

  2. One set of DNA is pulled to each side of the cell

  3. The nucleus divides

  4. The cytoplasm and cell membranes divide and two identical cells are formed

  5. The cell grows and increases the number of mitochondria and ribosomes

  6. The DNA lines up down the centre of the cell
• Red blood cells


  • Their shape gives them a large surface area for absorbing oxygen
  • They contain haemoglobin which allows them to carry oxygen
  • They don't have a nucleus which leaves more space for carrying oxygen
• The job of red blood cells is to carry oxygen from the lungs to all the cells in the body
• Coronary heart disease


  A disease of the coronary arteries where fatty deposits build up, narrowing the arteries and reducing blood flow and oxygen to the heart muscle
• Cardiovascular diseases are diseases of the heart or blood vessels
• Coronary heart disease can result in a heart attack
• Health


  The state of physical and mental wellbeing
• Communicable diseases


  Diseases that can spread from person to person or between animals and people, caused by bacteria, viruses, parasites or fungi
• Non-communicable diseases


  Diseases that cannot spread between people or between animals and people
• Coronary heart disease is an example of a non-communicable disease