exchange and transport in animals

• why is it necessary to transport substance into organisms

  • it is vital for life, and to transport waste products out of the organisms to prevent from accumulating
  • for example oxygen into animals for respiration, carbon dioxide for plants for photosynthesis, mineral ions and urea to transport out
• Explain the need for exchange surfaces and a transport system in multicellular organisms

  • specialised exchange surfaces allow efficient transport of substances from one area to another
  • exchange surfaces often have a short distance for diffusion and a large surface area
• what are some examples of exchange surfaces

  • root hair cells of plants : they can take up water and nutrients from the soil as they have a large surface area and thin walls
  • alveoli in lungs: helps air diffuse into lungs and covered in tiny capillaries which supply blood
  • villi in small intestine: digested food is absorbed over the membrane of these cells, into the bloodstream
  • stomata: carbon dioxide diffuses through them
• why does having a large surface area help transport substances

  • the greater the surface area, the more particles can move through, resulting in a faster rate of diffusion
• why does having a thin membrane help transport substances

  • provides a short diffusion pathway allowing the process to occur faster
• why does having an efficient blood supply help transport substances

  • creates a steep concentration gradient, so diffusion occurs faster
• how do you calculate rate of diffusion

  • surface area X concentration difference /thickness of membrane
  • this is Fick's law
• what factors affect the rate of diffusion

  • concentration gradient
  • temperature
  • surface area of membrane
• how does concentration gradient affect diffusion

  • the greater the difference in concentration, the faster the rate of diffusion
  • this is because more particles are randomly moving down the gradient than are moving against it
• how does temperature affect rate of diffusion

  • the greater the temperature, the greater the movement of particles, resulting in more collisions and therefore a faster rate of diffusion
• how does the surface area of the membrane affect diffusion

  • the greater the surface area, the more space for particles to move through, resulting in a faster rate of diffusion
• how is alveoli adapted to for gas exchange

  • alveoli are the small 'air sacs' in the lungs
  • they are surrounded by blood vessels with thin walls, allowing gas exchange between the lungs and blood
  • adaption:
  • very small and arranged in clusters ( creates a large surface are) for diffusion to take place over
  • the capillaries provide a large blood supply, maintaining the concentration gradient
  • the walls of the alveoli are very thin, meaning there is short diffusion pathway
• what is the blood made up of

  • plasma
  • red blood cells
  • white blood cells
  • platelets
• what is the structure and function of red blood cells (erythrocytes)

  • they carry oxygen molecules from the lungs to all the cells in the body
  • their biconcave disc shape provides a large surface area
  • they have no nucleus allowing more room to carry oxygen
  • they contain the red pigment haemoglobin, which binds to oxygen to form oxyhaemoglobin
• what is the structure and function of white blood cells (phagocytes and lymphocytes)

  • they are a part of the immune system, which is the body's defence against pathogens
  • they have a nucleus
  • there are a number of types
  • those that produce antibodies against microorganisms
  • those that engulf and digest pathogens
  • those that produce antitoxins to neutralise toxins produced by microorganisms
• what is the structure and function of plasma

  • this is liquid that carries the components in the blood: red blood cells, white blood cells, platelets, glucose, amino acids, carbon dioxide, urea, hormones, protein, antibodies and antitoxins
• what is the structure and function of platelets

  • they help the blood clot from at the site of a wound
  • the clot dries and hardens to form a scab, which allows new skin to grow
  • small fragments of cells
  • no nucleus
  • without them, cuts would result in excessive bleeding and bruising
• what types of blood vessels do the body contain

  • arteries
  • veins
  • capillaries
• what is the arteries structure and function

  • arteries carry blood away from the heart
  • has layers of muscles in the walls to make them strong
  • have elastic fibres allowing them to stretch
  • this helps the vessels withstand the high pressure created by the pumping of the heart
• what is the veins structure and function

  • veins carry blood towards the heart
  • the lumen (tube blood flows through) is wide to allow the low pressure blood to flow through
  • they have valves to ensure the blood flows in the right direction
• what is the capillaries structure and function

  • capillaries allow the blood to flow very close to cells to enable substances to move between them
  • one cell thick walls to create a short diffusion pathway
  • permeable walls so substances can move across them
• what is the heart

  • an organ in the circulatory system
• what is the circulatory system's function

  • it carries oxygen and nutrients to every cell in the body and removes the waste products
• what is the function of the heart

  • it pumps blood around the body in a double circulatory system
  • this means there are two circuits
• how does the heart pump blood around the body

  • there are two circuits, the left and right side for the blood to flow through
  • right side:
  • deoxygenated blood flows into the right atrium through the vena cava
  • the atria contract forcing the blood into the right ventricle into the pulmonary artery to be taken to the lungs
  • the valves then closes to make sure the blood does not flow backwards
  • left side:
  • oxygenated blood flows into the left atrium through pulmonary artery
  • the atria contract forcing the blood into the left ventricle to the aorta to be taken around the body
  • the valves then closes to make sure the blood does not flow backwards
• what is the structure of the heart

  • muscular walls to provide a strong heartbeat
  • the muscular wall of the left ventricle is thicker because blood needs to be pumped all around the body rather than just to the lung like the right ventricle
  • 4 chamber that separate the oxygenated blood from the deoxygenated blood
  • valves to make sure the blood flow backwards
  • coronary arteries cover the heart to provide it's own oxygenated blood supply
• what is the natural resting heart rate

  • 70 beats per minute
• what is the natural resting heart controlled

  • controlled by a group of cells found in the right atrium that acts as a pacemaker
  • this is as they provide stimulation through small electrical impulses which pass as a wave across the heart muscle, causing it to contract
  • without this, the heart would not pump fast enough to deliver the required amount of oxygen to the whole body
• what can be used if someone has an irregular heartbeat

  • an artificial pacemaker
• what is cellular respiration

  • an exothermic reaction which occurs continuously in living cells to release energy for metabolic processes such as aerobic and anaerobic respiration
• what is the equation for aerobic respiration

  • C6H12O6 + O2 - CO2 + H2O
• what is the equation for anaerobic respiration in animals

  • glucose - lactic acid
• what is the equation for anaerobic respiration in plants

  • glucose - ethanol + carbon dioxide
  • this reaction can be used to make bread and alcoholic drinks
• what is the difference between aerobic and anaerobic respiration

  • aerobic respiration uses oxygen whereas anaerobic occurs when there is not enough oxygen
  • aerobic yields the most energy whereas anaerobic does not yield as much energy
  • most aerobic respiration occur in the mitochondria
• Core Practical: Investigate the rate of respiration in living organisms

  • the apparatus consists of two tubes, one containing the living organisms and the other with glass beads to act as a control.
  • Both tubes contain an alkali such as sodium hydroxide to absorb any carbon dioxide given off during respiration. This ensures that any volume changes measured in the experiment are due to oxygen uptake only.
  • Once the apparatus has been set up, the movement of the coloured liquid towards the insect will give a measure of the volume of oxygen taken up by the insect for respiration.
  • The reduction of volume in the tube increases pressure causing the coloured liquid to move.
  • The distance moved by the liquid in a given time is measured will provide the volume of oxygen taken in by the insect per minute.
  • Volume is given by volume of a cylinder V=πr2h, where h is the distance moved by the coloured liquid. The unit of rate of respiration is cm3/min.
• how did you measure cardiac output

  • cardiac output = stroke volume X heart rate