Paper 1

• Meristem


  Produces new cells for growth and is found at the tips of roots and shoots
• Stomata


  Allows diffusion of gases in and out of the leaf, is opened and closed by the guard cells
• Epidermis 


  Covers the outside surfaces of the plant for protection
• Palisade mesophyll 


  Main site of photosynthesis
• Spongy mesophyll 


  Air spaces between cells for gases to diffuse
• Xylem 


  Transports water and minerals through the plant and supports the plant
• Phloem


  Transports dissolved food minerals around the plant
• Many chloroplasts are found at the top of the leaf to trap maximum sunlight
• Water Transport

  •Water enters the plant from soil, through the root hair cells via osmosis.

  •Root hair cells, Xylem and Phloem are Specialised to transport water and minerals and sugars around the plant.

  •Most water will evaporate and diffuse out of the stomata ( Transpiration)

  •At night, stomata close as carbon dioxide isn't needed for photosynthesis, this reduces water loss.
• Factors affecting rate of Transpiration

  •Higher Temperature - higher rate as more energy is transferred to water

  •Faster Air flow- faster rate as it blows away water vapour allowing more to evaporate

  •Higher Light intensity - increases rate as stomata opens

  •More Humidity - lowers rate as there's more water vapour so concentration gradient for diffusion is lower
• Translocation 


  Movement of food through phloem tissue
• Photosynthesis

  •Carbon dioxide + water -> glucose + oxygen

  •Energy is required and supplied from sunlight

  •Endothermic reaction
• Factors affecting photosynthesis 


  •Temperature

  •Carbon dioxide concentration

  •Light intensity

  •water concentration
• Converting glucose


  A plant can store glucose as:

  •insoluable starch - stored in stem, leaves or roots

  •fat or oil - stored in seeds

  •cellulose - strengthens cell wall

  •Proteins - used for growth and enzymes
• Respiration


  •Exothermic reaction

  Releases energy for chemical reactions, movement and to keep warm
• Aerobic respiration

  Glucose + oxygen -> Carbon dioxide + water
• Anaerobic respiration 


  Glucose -> lactic acid

  •Glucose is not fully broken down so it transfers less energy leading to oxygen debt
• Fermentation 


  Glucose -> Ethanol + carbon dioxide
• Metabolism


  Sum of all chemical reactions in cell or body
• Metabolism


  • Controlled by enzymes
  • May need energy • Energy transferred by respiration to make new molecules
• Metabolism includes


  • Conversion glucose → starch, glycogen + cellulose
  • Formation of lipid molecules aglyceral fatty acids
  • Form amino acids to synthesise proteins
  • Breakdown of excess proteins into crea for excretion
• Blood


  •Plasma Components = red blood cells, white blood cells, platelets

  •Transports chemical substances around the body such as: products of digestion, hormones, antibodies, urea and carbon dioxide
• Red blood cells


  •Contain haemoglobin - bind oxygen to transport it from lungs to tissues and cells for respiration

  •No nucleus - so it has more room for haemoglobin

  •Very small to fit through capillaries

  •Large surface area - so oxygen can quickly diffuse
• Arteries


  •From heart to organs

  • Carries oxygenated blood

  •Thick walls made from muscle and elastic fibres
• Veins


  •From organs to heart

  •Carries deoxygenated blood

  •Thinner walls and has valves to prevent backflow
• Capillaries

  • Allows substances to pass in and out of the cell
  • Narrow ,thin walls - one cell thick
• White blood cells

  • Protects body from infection
  • Can change shape - to surround and engulf microorganisms
• Platelets

  • Fragments of cells, collects at wounds and triggers blood clotting
• Adaptations of alveoli

  • Large,moist surface area
  • Good blood supply
  • Close to capillaries - small distance for gases to diffuse
• Amylase

  • Produced by salivary glands and pancreas
  • Is carbohydrase
  • Turns starch to sugar
• Protease

  • Produced in stomach, pancreas and small intestine
  • Turns proteins to amino acids
• Lipase

  • Produced by pancreas and small intestine
  • Turns lipids into fatty acids and glycerol
• Bile

  • Made in liver
  • Stored in gallbladder
  • Neutralises hydrochloric acid and emulsifies fats
• Xylem tissue

  • Arranged end to end but the end walls break down to form hollow tubes
  • Cell wall is strengthened by a substance called lignin
• Phloem Tissue

  • The end walls of cells allow sugars through but support the tubes
  • Arranged end to end in tubes
  • Companion cell
• Root hair cell

  • Lots of mitochondria for active transport of minerals
  • Long projection to increase surface area to increase absorption of water and minerals
• Diffusion

  • Allows molecules to move
  • Movement is down a concentration gradient
  • Particles move from a high concentration to a low concentration
• Osmosis

  • Allows molecules to move
  • Movement is down a concentration gradient
  • Particles move from a high concentration to a low concentration
  • Diffusion in the case of water
• Active transport

  • Moves substance against a concentration gradient from low to high concentration
  • Requires energy from respiration
  • Allows mineral ions to be absorbed into plant root hair from very dilute solutions in the soil
  • Allows sugar molecules to be absorbed from lower concentrations in the gut into the blood, which has a higher concentration
• Mitosis

  1. One set of chromosomes are pulled to each end of the cell
  2. Nucleus divides
  3. Cytoplasm and cell membranes divide to form two identical cells