Transport

• Xylem


  Made of dead cells, has a thick cell wall, cell wall is made of lignin, impermeable, no cytoplasm, transports water and minerals to leaves, flows from the roots.
• Phloem


  Made of living cells, thin cell wall, cell wall is made of cellulose, permeable, has a cytoplasm lining, transports sucrose to growing parts and storage organs, flows from the leaves.
• Transpiration

  The evaporation of water from the leaves of a plant.
• Transpiration stream


  The flow of water up the xylem by cohesion and adhesion.
• Functions of the water that is transported via the transpiration stream:

  Photosynthesis, cooling of the leaf, it contains dissolved mineral ions, keeps the cells turgid.
• Flow of water from soil to surrounding air:

  Soil -> root hair cell -> root cortex -> xylem -> spongy mesophyll cells -> air spaces -> stomata -> surrounding air
• Factors that effect the rate of transpiration

  Wind speed, light intensity, temperature, humidity.
• Effect of light intensity on transpiration

  Increased light intensity ….

  increased photosynthesis ….

  increased stomata opening for enhanced

  carbon dioxide and oxygen exchange ….

  increased rate of transpiration.
• Effect of temperature on transpiration

  Increased temperature …

  increased particle energy …

  increased particle movement … increased

  rate of evaporation from mesophyll cells …

  increased rate of transpiration.
• Effect of wind speed on transpiration

  Increased wind speed …

  Increased air movement across the leaf

  surface …

  increased removal of water molecules from

  air …

  increased diffusion gradient …

  increased diffusion of water vapour from

  stomata …

  increased rate of transpiration.
• Effect of humidity on transpiration

  Decreased humidity …

  Dry air …

  increased diffusion gradient -> increased

  diffusion of water vapour from stomata …

  increased rate of transpiration.
• Red blood cell

  Transports oxygen

  around the body,

  Biconcave (increased SA:V ratio) = increased rate

  of diffusion into / out of cell.

  ● Lots of haemoglobin (carry oxygen) = carries

  oxygen as oxyhaemoglobin.

  ● No nucleus (increased volume) = more Hb.

  ● Small and flexible = ability to travel through

  capillaries.
• White blood cell - phagocyte


  Destroys pathogens

  therefore preventing

  infection and disease.

  • Has pseudopods / sleeves of cytoplasm = capable

  of engulfing microorganisms

  ● Has digestive enzymes = capable of digesting

  microorganisms.
• White blood cell - lymphocyte


  Destroys pathogens

  therefore preventing

  infection and disease.

  • Release antibodies. Antibodies are complementary

  to the antigen of the surface of the pathogen.

  Antibodies inactivate or kill the pathogen.

  ● Produce antitoxins. Antitoxins neutralise the

  toxins released by pathogens.

  ● Produce memory cells. Memory cells provide

  immunological memory.
• Platelet


  Aids clotting at the site

  of a wound therefore

  preventing blood loss and

  bacteria entry.

  Release an enzyme that causes soluble fibrinogen

  to turn into insoluble fibrin.

  ● Fibrin traps red blood cells and platelets to form a

  clot/scab.
• Plasma


  Transports blood cells,

  platelets and dissolved

  substances (carbon

  dioxide, soluble products

  of digestion, urea,

  hormones) as well as

  heat around the body.

  Acts as a good solvent. This therefore enables

  substances such as glucose and amino acids to be

  transported in the blood. Carbon dioxide is

  transported in blood plasma as carbonic acid.
• Vaccine


  Non-virulent (harmless) pathogens can be placed into a blood stream via a vaccine to provide immunity
• Non-virulent (harmless) pathogens


  • Have the same antigens as virulent (harmful) pathogens
  • Are a dead or weakened form of the pathogen and therefore do not cause harm to the body
• Immune system response to non-virulent (harmless) pathogens


  1. Phagocytes engulf pathogen

  2. Lymphocytes produce antibodies and antitoxins

  3. Destroying the non-virulent (harmless) pathogen
• Memory cells


  Special lymphocytes that remain in the blood stream, providing immunological memory
• If infected by the virulent (harmful) form of the pathogen in the future


  The memory cells are ready to rapidly produce the required antibodies in order to rapidly destroy the disease causing pathogens
• Why does the heart need valves?


  To prevent the back flow of blood.
• Atrial systole


  Atria contract, atrioventricular valves are forced open, blood enters the ventricles.
• Ventricular systole


  Ventricles contract, semi-lunar valves are forced open, blood enters the arteries.
• Diastole


  Atria and ventricles relax, all valves close, blood returns to the atria.
• Why heart rate increases during exercise: 


  Heart rate increases during exercise in order to pump blood more rapidly around the body

  Increased blood supply to deliver increased oxygen and glucose more rapidly for increased

  respiration and removes waste products, such as carbon dioxide, more rapidly.

  Heart rate is controlled by nerves but the hormone adrenaline, produced by the adrenal

  glands, causes an increase in heart rate. Adrenaline results in a full range of effects known

  as the ‘fight or flight’.

  Resting heart rate may also vary depending upon age, fitness and illness.
• Factors that increase the risk of developing coronary heart disease.

  Smoking, diabetes, high blood pressure, obesity, high cholesterol diet.
• Arteries


  Delivers blood away

  from the heart

  Has a thick layer of

  muscle.

  Have a small lumen.

  Blood travels at a high

  pressure

  Do not have valves

  present
• Veins


  Delivers blood to the

  heart

  Has a thin layer of

  muscle.

  Has a large lumen to

  allow blood to flow easily.

  Blood travels at a low

  pressure

  Has valves present
• Capillaries


  Tiny vessels in close contact with cells. Only one cell thick to help increase the rate of diffusion of O 2 , glucose and CO 2

  between respiring cells and the blood Connect arteries to veins. Carry both oxygenated and deoxygenated blood. Valves not present. The walls are very thin. Blood flows at a low pressure
• What is the circulatory system made up of?

  Heart, blood vessels and blood
• What is the function of the circulatory system?

  The circulatory system, via the transporting of blood, provides the raw materials needed by cells whilst also removing waste products.
• Why is the circulatory system termed the double circulatory system in mammals and birds?

  It is made up of two circuits. One circuit links the heart and lungs whilst the other circuit links the heart and the rest of the body.
• What is the advantage of the double circulatory system?

  A higher blood pressure can be maintained enabling a greater flow of blood to the tissues to enable cells to receive oxygenated blood more quickly.
• Blood vessels - lungs

  Pulmonary artery and pulmonary vein
• Blood vessels - Heart


  Vena cava and aorta
• Blood vessels - liver


  Hepatic vein and hepatic portal vein
• Blood vessels - kidneys


  Renal vein and renal artery