Transport Systems

• Unicellular organisms have large SA:V ratios which means there is only a short distance between the surface of the organism and the centre
• Unicellular organisms do not need transport systems
• Multicellular organisms are larger than unicellular organisms so they cannot rely on diffusion alone to get nutrients around their body
• Phloem transports sucrose and amino acids from the leaves to the stem and roots
• Xylem transports water and minerals from the roots to the rest of the plant
• Root hair cells

  • Adapted for the efficient uptake of water (by osmosis) and mineral ions (by active transport)
  • Mitochondria in root hair cells release energy for active transport
  • Root hairs increase the surface area of plant roots, increasing the rate at which water and minerals can be taken up
• Root hair cells take up mineral ions and water from the soil

  1. Mineral ions taken up by active transport

  2. Water concentration of cell cytoplasm reduced due to mineral ions

  3. Water moves into root hair cell by osmosis
• Route of water through the plant

  1. Water moves by osmosis into root hair cells, through root cortex and into xylem vessels

  2. Water carried up to leaves where it enters mesophyll cells
• Transpiration


  Loss of water vapour from the parts of the plant that are above ground (leaves, stem, flowers)
• Functions of transpiration

  • Transporting mineral ions
  • Providing water to keep cells turgid to support plant structure
  • Providing water to leaf cells for photosynthesis
  • Keeping the leaves cool
• Factors affecting rate of transpiration

  • Humidity
  • Wind speed
  • Temperature
  • Light intensity
• Humidity

  Transpiration rate decreases in humid air because diffusion gradient decreases as water collects near leaf's stomata
• Wind speed

  Transpiration rate increases as wind speed increases because moving air removes water vapour near stomata, increasing diffusion gradient
• Temperature

  Transpiration rate increases as temperature increases because rate of evaporation from mesophyll cells increases
• Light intensity

  Transpiration rate increases as light intensity increases because stomata of leaves open for photosynthesis
• Investigating factors affecting transpiration

  1. Cut shoot underwater to prevent air entering xylem and place in tube

  2. Set up airtight apparatus with Vaseline to seal gaps

  3. Dry leaves of shoot

  4. Remove capillary tube from beaker to allow single air bubble to form, then place back

  5. Set up lamp 10cm from leaf and allow 5 mins adaptation

  6. Record start and end location of air bubble over 30 mins

  7. Change light intensity and repeat experiment

  8. Calculate rate of transpiration by dividing distance bubble travelled by time period
• Composition of blood:

  • Red blood cells (45%)
  • White blood cells (<1%)
  • Platelets (<1%)
  • Plasma (55%)
• Red blood cells: biconcave discs that carry oxygen around the body
• White blood cells: large cells with a nucleus
• Platelets: fragments of cells
• Plasma: straw coloured liquid
• Role of plasma:

  • Transports CO2 from respiring cells to lungs
  • Transports digested food and mineral ions
  • Transports urea
  • Transports hormones
  • Transports heat energy
• Adaptations of red blood cells:

  • Have biconcave disc shape to increase surface area to volume ratio
  • Contains haemoglobin that binds to oxygen
  • No nucleus to make space for more haemoglobin
  • Thin shape for short diffusion distance
• White blood cells

  Defend against pathogenic microorganisms
• Types of white blood cells

  • Phagocytes
  • Lymphocytes
• Phagocytes

  • Carry out phagocytosis by engulfing and digesting pathogens
  • Have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells
  • Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it
• Lymphocytes

  • Produce antibodies
  • Antibodies are Y-shaped proteins with a shape that is specific (complementary) to the antigens on the surface of the pathogen
  • This is a specific type of immune response as the antibodies produced will only fit one type of antigen on a pathogen
• Immune response to pathogen


  1. Pathogen enters bloodstream and multiplies

  2. Release of toxins and infection of body cells causes symptoms

  3. Phagocytes recognise and engulf/digest pathogen (non-specific response)

  4. Lymphocyte recognises pathogen antigens and produces specific antibodies

  5. Lymphocyte clones itself to produce more antibodies

  6. Antibodies cause agglutination of pathogens

  7. Phagocytes engulf and digest agglutinated pathogens

  8. Patient retains antibodies and memory cells specific to the disease

  9. Secondary immune response triggered if patient encounters same pathogen again
• How vaccines work

  1. Harmless version of pathogen is injected

  2. Antigens trigger immune response in lymphocytes

  3. Lymphocytes produce antibodies specific to the antigen

  4. Memory cells and antibodies remain in bloodstream
• Blood clotting

  • Platelets release chemicals that cause fibrinogen to convert to insoluble fibrin, forming a clot
  • Clot dries into a scab to protect the wound
• Importance of blood clotting

  • Prevents continued/significant blood loss
  • Seals wound to prevent entry of microorganisms
• Pathway of blood through the heart

  1. Deoxygenated blood flows into right atrium

  2. Flows through tricuspid valve into right ventricle

  3. Pumped through semilunar valve into pulmonary artery

  4. Oxygenated blood returns to left atrium

  5. Flows through bicuspid valve into left ventricle

  6. Pumped through semilunar valve into aorta

  7. Valves prevent backflow
• Heart rate

  • Measured by counting beats per minute
  • Controlled by pacemaker cells in right atrium
• Effect of exercise on heart rate

  1. Increased respiration in muscles requires more oxygen and glucose delivery

  2. Nervous system stimulates increased heart rate and blood volume pumped

  3. Adrenaline production also increases heart rate

  4. After exercise, heart rate remains elevated to pay off oxygen debt
• Physically fit person

  • Lower resting heart rate
  • Shorter recovery time after exercise
• Coronary heart disease

  • Fatty deposits (plaque) build up in coronary arteries
  • Reduces blood flow and oxygen supply to heart muscle
• Effects of coronary heart disease

  1. Partial blockage causes angina

  2. Complete blockage causes heart attack
• Treatments for coronary heart disease

  • Stents to widen artery lumen
  • Statins to lower blood cholesterol
• Risk factors for coronary heart disease

  • Obesity
  • High blood pressure
  • High cholesterol
  • Smoking
• Types of blood vessels

  • Arteries
  • Veins
  • Capillaries