B2

• Transpiration


  Evaporation of water from leaves
• Translocation


  Transport of nutrients in plants
• Translocation


  1. Transport of sugar via photosynthesis

  2. phloem cells form to make phloem tubes

  3. Pores in tubes enable movement of sap / h20 and sugars

  4. Once sugar gets to destination it is stored or used
• Transpiration


  1. Stomata open, more H₂O into plant

  2. Increase light intensity

  3. Wind blows water vapour increases

  4. Concentration gradient difference

  5. Continuation of water evaporation

  6. Chain of transpiration heat
• Leaf structure


  • Waxy cuticle to prevent water loss
  • Upper epidermis transparent
  • Spongy mesophyll- space for gas exchange
  • Palisade mesophyll cells- where photosynthesis happens
  • Lower epidermis with stomata
  • Guard cell- transpiration
• Stomata open and close to maximise CO₂ intake and reduce H₂O outtake
• Turgid


  Large gap to define location
• Stomata close at night as photosynthesis is not taking place
• Stomata are on the underside of leaves, less likely for water to evaporate
• Meristem


  1. Growing tips by roots and the

  2. Differentiate

  3. Specialise
• Red blood cell


  • Makes up half of blood by volume
  • Carry oxygen from lungs to tissues
  • Oxygen binds with Haemoglobin
  • Haemoglobin splits so oxygen can diffuse into tissues
  • No nucleus, more space for haemoglobin and oxygen
• White blood cell


  • Essential for immune system
  • Phagocytes - ingest pathogens
  • Antibodies - bind and destroy
  • Antitoxins - neutralise
• Platelets


  • Fragments of cells
  • No nucleus
  • Help with blood clotting
  • Stop microorganisms getting in
• Plasma


  • 50% of volume of blood
  • Carries dissolved substances - amino acids, glucose, urea, hormones, antibodies
• Artificial blood lacks red blood cells
• Blood transfusion uses real blood cells
• Arteries


  • Thick walls of muscle and elastic tissue
  • Narrow lumen
  • Carrying blood at high pressure
• Capillaries


  • Small
  • In close contact with all tissues
  • Exchange substances with cells
  • Permeable walls for diffusion
  • Small lumen
  • Large cross-sectional area
  • Low blood pressure to allow exchange
  • One cell thick
• Veins


  • Bigger lumens
  • Thin walls of elastic and muscle
  • Low pressure
  • Valves to prevent backflow
• Gas exchange in lungs

  1. Air breathed in

  2. Passes down trachea

  3. Into bronchi

  4. Into bronchioles

  5. Into alveoli for gas exchange
• Alveoli


  • One layer of thin cells
  • Moist walls allow gases to dissolve
  • Large surface area
  • Oxygen higher concentration than in blood
  • Carbon dioxide lower concentration than in blood
• Active transport


  1. Movement of molecules against concentration gradient

  2. From lower to higher concentration

  3. Requires energy from cells

  4. Takes place across a membrane

  5. Requires special transport proteins

  6. Energy comes from cellular respiration

  7. Energy stored in ATP
• Root hair cells


  • Hair-like projections
  • Large surface area for absorption
  • Minerals at higher concentration inside
  • Lots of mitochondria
• Circulatory system


  • Transports oxygen and nutrients
  • heart
  • Blood vessels
• Double circulatory system


  1. Heart

  2. Thick muscular walls

  3. Valves prevent backflow

  4. Deoxygenated blood: Vena cava, right atrium, right ventricle,

  5. Oxygenated blood: lungs, pulmonary vein, left atrium, left ventricle, aorta, body

  6. Pacemaker cells in right atrium send electrical impulses
• Arteries carry blood away from the heart, veins carry blood towards the heart
• Coronary arteries supply oxygen to the heart muscle and tissues
• Phloem

  • Made of sieve tube elements- living cells with perforated end-plates to allow stuff through
  • Sieve tubes have no nucleus and can't survive on their own so they have companion cells
  • Translocation- transport food (ions) substances up and down
• Xylem

  • dead xylem cells
  • no end, long hollow tube
  • Strengthened by lignin
  • thick walls made of cellulose which makes them great supports
  • Transpiration stream- transport water and minerals up from the roots
• correct direction of flow in double circulatory system

  1. left side of heart
  2. body organs
  3. right side of heart
  4. lungs
• Mitosis

  1. Cell has two copies spread out in long strings
  2. DNA forms X-shaped chromosomes (each arm and exact copy)
  3. Chromosomes line up at the centre and cell fibres pull them apart - two arms go at opposite ends
  4. Membrane formed around each set of chromosome that become nuclei of the two new cells
  5. cytoplasm divides
  6. two new genetically identical cells
• Explain how guard cells change shape to open stomata.


  > Guard cells photosynthesise producing sugars

  > Water moves into guard cells that makes it become turgid and open up

  > guard cells curves to make an opening
• Cell cycle

  1. Cell structure grows and new proteins made
  2. Synthesis- cell replicates it's DNA so that when it splits in mitosis the two new cells will contain identical DNA
  3. cell keeps growing and proteins needed for cell division are made
  4. Mitosis- cycle ends here
• what is cytokinesis

  • after movement of chromosomes
  • Cell membrane pinches inwards and separates and closes the two nuclei creating identical daughter cells
  • That will grow independently
• Vili

  • located in small intestines where dissolved food molecules are dissolved out of digestive system into blood
  • covered in villi
  • Increases surface area
  • Single layer surface cells
  • very good blood supply to assist quick absorption
• Leaves adapted for efficient gas exchange

  • Maximise diffusion of O2 and CO2
  • Broad so large surface area for diffusion
  • Thin, short distance for gases to travel
  • Air spaces inside leaf to let gases move easily to cells and also increases surface area
  • Stomata to let gases diffuse out and allow water to escape
• Enzyme substrate relationship

  Lock and key
• Diffusion

  • moving from high concentration
  • down concentration gradient
  • to an area of low concentration
• Osmosis

  • movement of water through partially permeable membrane
  • From an area of high water concentration to an area of low concentration
• Light and rate of transpiration

  • light- the brighter the light, the greater transpiration rate
  • Bright light increases rate of photosynthesis causing stomata to open and to let Co2 in
  • Stomata closes at night and water cannot escape