transport

• Unicellular organisms


  Single-celled organisms
• Unicellular organisms


  • Every unicellular organism needs to exchange substances to function properly (example: food molecules and waste products)
  • Movement of substances from a high to low concentration occurs across the cell membrane
  • 3 transport processes: diffusion, active transport, osmosis
  • Diffusion of water molecules from a high to low concentration
  • Large surface area to volume ratio: short distance from surface to centre of the organism
  • Unicellular organisms do not require transport systems / exchange surfaces
• Multicellular organisms


  • Many layers of cells, distance from surface to the centre is long
  • Multicellular organisms require specialised transport systems
• Transport systems


  • Circulatory system
  • Vascular system in plants
• Xylem


  Transports water and mineral ions from the roots to other parts of the plant
• Phloem


  Transports sucrose and amino acids between the leaves and other parts of the plant
• Transpiration


  The evaporation of water from the surface of a plant
• Transpiration


  1. Water is constantly being lost from leaves

  2. Concentration gradient: water in roots > water in leaves

  3. Water is drawn up from soil to root hair cells (osmosis)

  4. Water absorbed by root hairs

  5. Vascular bundle in roots draw water like a structure push down into roots
• Root hair cells


  • Single-celled extension of epidermis cells in the root
  • Grow between soil particles and absorb water and minerals from the soil
  • Adaptations: large surface area, contain mitochondria to release energy for active transport, efficient uptake of water by osmosis and minerals by active transport
• Humidity increases


  Rate of transpiration slows down
• Humidity decreases


  Rate of transpiration increases
• Temperature increases


  Rate of transpiration increases
• Light intensity increases


  Rate of transpiration increases
• Wind speed increases


  Rate of transpiration increases
• Potometer

  Piece of apparatus used to estimate the rate of transpiration
• Mass porometer


  Measures the change in mass of a plant as a measure of the amount of water that has evaporated from the leaves and stem
• Bubble potometer


  Measures the uptake of water by a stem as a measure of the amount of water being lost by evaporation and pulling water through the stem to replace it
• Composition of blood


  • Red blood cells
  • White blood cells
  • Platelets
  • Plasma
• Plasma


  Pale yellow liquid which carries just about everything needed in the body, e.g. antibodies, glucose, CO2, heat energy
• Red blood cells


  • Biconcave disc structure to increase surface area
  • Carry oxygen from the lungs and deliver it throughout the body
  • Transport waste such as CO2 back to the lungs to be exhaled
  • No nucleus
  • Contain haemoglobin which reacts with oxygen in the lungs to form oxyhaemoglobin
• White blood cells


  • Protect the body against pathogens by either phagocytosis or antibody production
  • First line of defense: skin, lysozymes, hairs, cilia, stomach acid
  • Phagocytes: surround and engulf bacteria, larger than RBCs, lobed nucleus, granular cytoplasm
  • Lymphocytes: produce antibodies specific to antigens on pathogens
• Phagocytosis


  1. Bacteria is identified and phagocyte moves to it

  2. Cytoplasm surrounds and engulfs the bacteria, cell membrane fuses enclosing bacteria in a vacuole

  3. Enzymes are secreted into the vacuole to digest bacteria

  4. Bacteria is killed and digested

  5. Indigestible residue removed
• Vaccination


  • Exposure to a harmless version of a pathogen
  • Lymphocytes recognise the antigens in the bloodstream and produce antibodies specific to that antigen
  • Primary immune response: memory cells and antibodies remain circulating the bloodstream for long-term immunity
  • Secondary immune response: faster and greater antibody production upon re-exposure to the pathogen
• Arteries


  • Carry blood away from the heart
  • Thick inner and outer layer to maintain high blood pressure
  • Narrow lumen
• Veins


  • Carry blood to the heart
  • Low pressure, thin walls with less muscle and elastic fibres
  • Wide lumen to maximise blood flow
• Capillaries


  • Join arteries and veins
  • Very low pressure
  • Majority of diffusion occurs
  • Very small lumen, red blood cells pass one at a time
• Parts of the circulatory system


  • Pulmonary (related to lungs)
  • Cardiac (related to heart)
  • Renal (related to kidneys)
  • Hepatic (related to liver)
• Heart


  • Made of cardiac muscle that contracts and relaxes without stimulation from the nervous system
  • Has its own blood supply through the coronary arteries
  • 4 chambers: right atrium, left atrium, right ventricle, left ventricle
• Journey of red blood cells


  1. Deoxygenated RBCs from body to right atrium, right ventricle, pulmonary artery, lungs to be oxygenated

  2. Oxygenated RBCs from lungs to left atrium, left ventricle, aorta, body to be used
• Coronary heart disease


  Fatty substance called plaque can build up inside the coronary arteries, reducing blood flow to the heart muscle
• Humans need a circulatory system because we have a small surface area to volume ratio, so diffusion does not occur quickly enough to sustain us
• Exercise increases heart rate to speed up delivery of oxygen and removal of carbon dioxide
• Water transport from roots to leaves

  1. Water enters the roots through osmosis

  2. Water leaves the roots through the xylem where transpiration occurs

  3. As water is lost through transpiration, more water is pulled upwards to replace the loss
• Root hair cells


  • Increase surface area for absorption
  • Water moves to the roots through osmosis
  • Water is needed by plants for photosynthesis