topic 8

• How do you find surface area to volume ratio?

  surface area to volume, simplified
• How is urea removed from the body?

  -via skin through sweat

  -via kidneys in urine after having diffused from cells in the blood plasma for removal
• How does exchange occur in single celled organisms?

  Gases and dissolved substances can diffuse directly into or out of cell across the cell membrane. They have a large SA:V ratio, so enough substance can be exchanged over the membrane to supply the volume of the cell.
• Where does gas exchange occur in mammals?

  alveoli of lungs
• How are alveoli adapted for gas exchange?

  • large surface area

  • good blood supply

  • thin walls (one cell thick) - short diffusion pathway

  • moist - dissolve gases
• How do you calculate rate of diffusion?

  surface area x difference in concentration / length of diffusion path
• What are the three factors which affect rate of diffusion?

  DIstance, concentration gradient/ difference, Surface Area
• What is the equation for aerobic respiration?

  glucose + oxygen -> carbon dioxide + water
• What is the formula equation for aerobic respiration?

  C6H12O6 + 6O2 -> 6CO2 + 6H2O
• When is anaerobic respiration used?

  Anaerobic respiration happens when there's not enough oxygen available.
• What are the disadvantages of anaerobic respiration?

  - produces lactic acid that causes cramps

  - produces less energy
• What is the equation for anaerobic respiration in plants?

  Glucose -> ehtanol + carbon dioxide
• What is the formula for anaerobic respiration in animals?

  glucose -> lactic acid
• How can you measure rate of respiration?

  In aerobic respiration, organisms use up oxygen. By measuring the amount of oxygen consumed by organisms in a given time, you can calculate the rate of respiration. You can do this using a respirometer
• How can you investigate effect of temperature on rate of respiration?

  - soda lime added to both test tubes (absorbs CO2)

  - a ball of cotton wool is placed on top, and in one tube woodlice are added, glass beads are added to the other one

  - set up respirometer

  - syringe adds a known level of liquid to the manometer

  - left for a set period in a water bath at 15 degrees

  - air volume in woodlice tube will decrease, O2 used, CO2 absorbed

  - reduces pressure in tube, drawns liquid in manometer towards the tube.

  -distance moved in a given time is measured, and you can calculate volume of O2 absorbed per minute, this is the rate of respiration

  -repeat with different temperatures
• What are the types of white blood cell?

  phagocytes and lymphocytes
• What is the function of phagocytes?

  engulf and destroy pathogens, this is called phagocytosis
• What is the function of lymphocytes?

  produce antibodies against specific antigens, and antitoxins to neutralise any toxins produced by unwelcome microorganisms
• What is the function of red blood cells?

  transport oxygen and carbon dioxide to and from cells around the body
• What happens to your white blood cell count when you have an infection?

  It will increase, as they multiply
• What are the adaptions of red blood cells?

  Biconcave disc shape (large SA), no nucleus, contain haemoglobin
• What is the product called when oxygen binds to haemoglobin?

  oxyhaemoglobin
• What is the function of platelets?

  blood clotting - stops microorganisms getting into a wound, and prevents excessive bleeding and bruising
• What is plasma?


  Liquid part of blood
• What is carried in the plasma?


  CO2, hormones, nutrients (glucose and amino acids), proteins, antibodies, antitoxins, red blood cells, white blood cells, platelets
• What do arteries do?


  carry blood away from the heart
• What do capillaries do?

  connect arteries and veins, carry blood to cells and tissues

  supply food and O2, and take away CO2
• What do veins do?

  carry blood to the heart
• How are arteries adapted to their function?

  - they have thick layers of muscle to make them strong enough to withstand the high pressure at which they carry blood

  - they have strong elastic fibres to allow them to stretch and spring back to pump the blood
• How are capillaries adapted to their function?

  - they have permeable walls so that substances can diffuse in and out

  - their walls are only one cells thick which increases the rate of diffusion by decreasing the distance over which it occurs

  - capillaries are really close to every cell in the body to exchange surfaces with them
• How are veins adapted to their function?

  - the walls are not thick as blood is not carried at a low pressure

  - they have a big lumen to help blood flow

  - they have valves to keep blood flowing in the right direction
• What is a double circulatory system?

  The circulatory system is made of two circuits joined together. One links your heart and lungs (the pulmonary circuit). This circuit carries deoxygenated blood to the lungs. The other links your heart and body to deliver oxygenated blood to the cells.
• Describe the journey of blood through the heart.

  Deoxygenated blood arrives at the right atrium through the vena cava from tissue around the body. At the same time oxygenated blood arrives at the left atrium through the pulmonary veins from the lungs. The atria muscles contract, raising pressure and causing the tricuspid (right) and bicuspid (left) valves to open. The blood flows into the right and left ventricles.

  
  

  The ventricles contract raising pressure and causing the tricuspid and bicuspid valves to close and the semilunar valves to open. Blood is pumped into the pulmonary artery from the right ventricle and the aorta from the left ventricle.

  
  

  The pulmonary artery carries blood to the lungs where it will be oxygenated before making its way back to the heart. The aorta carries blood to the different parts of the body.

  
  

  High pressure in the aorta and pulmonary artery closes the semilunar valves and the process starts again.
• How do you calculate cardiac output?

  stroke volume x heart rate
• What are the units for heart rate?

  BPM
• What are the units for stroke volume?

  cm^3