unit 1 aos3

• Specialisation and organisation of plant cells into tissues for specific functions in vascular plants


  Intake, movement and loss of water
• Specialisation and organisation of animal cells into tissues, organs and systems with specific functions


  Digestive, endocrine and excretory
• Regulation of body temperature, blood glucose and water balance in animals by homeostatic mechanisms

  1. Stimulus-response models

  2. Feedback loops

  3. Associated organ structures
• Malfunctions in homeostatic mechanisms: type 1 diabetes, hypoglycaemia, hyperthyroidism
• Palisade mesophyll cells


  Contain chloroplasts which contain chlorophyll for capturing light energy and are the site of photosynthesis
• Xylem


  To carry water from the roots to the leaves
• Phloem


  To carry sugars made in photosynthesis to other parts of the plant
• Stomata


  To allow CO2 (input of photosynthesis) and O2 (output of photosynthesis) to enter and exit the leaf
• Transpiration


  Water is drawn up through the plant (via the xylem) from the roots to the leaves. At the leaves, water vapour is lost via open stomata (during gas exchange).
• Increased air flow


  Water vapour lost faster
• Increased temperature


  Water vapour lost faster
• Increased humidity


  Transpiration rate decreases (lower concentration gradient)
• Factors that affect the rate of photosynthesis

  • Temperature
  • Light
  • Concentration of reactants
• Excretory system


  To remove waste products from the bloodstream (e.g. urea)
• Regulation of water balance

  Low water concentration (or high solute concentration) in blood is detected by osmoreceptors in the hypothalamus which sends a message to the pituitary gland to release ADH hormone. ADH acts on the kidney to put more water back into the blood stream (increase reabsorption of water) which will increase water concentration.
• Homeostasis


  The maintenance of a relatively stable internal environment, within narrow limits, despite changes in the external environment
• Positive feedback loops amplify the stimulus/change in a system
• Negative feedback loops reverse/counteract the stimulus/change in a system, returning the system back to its 'setpoint' (original state)
• Thermoregulation


  1. Alpha cells in pancreas produce glucagon

  2. Beta cells in pancreas produce insulin
• Blood glucose regulation


  1. When blood glucose levels (BGL) are high, specialised beta cells in the pancreas release the hormone insulin into the blood stream. This hormone causes body cells to take up glucose from the blood stream. Excess glucose is converted to glycogen and stored in liver or muscle cells. This causes BGL levels to drop and return to the set point.

  2. When blood glucose levels (BGL) are low, specialised alpha cells in the pancreas release the hormone glucagon into the blood stream. This hormone causes liver and muscle cells to convert glycogen back into glucose and release it into the blood stream. This causes BGL levels to rise and return to the set point.
• Enzymes function best at their optimal pH
• Either side of the optimal (that is the pH is lower or higher than the optimal) the enzyme will start to denature. This means that it will lose its complex 3D shape and no longer be able to bind to the substrate (starch).
• You can't see the cells underneath the skin like red blood cells or muscle cells or bone cells
• Your body is made of trillions of cells
• Cells work together and are very organized with specific functions
• Cells carry your whole DNA code but use specific parts of your DNA code depending on the cell's function
• Cells can make up body tissue, tissues can make up an organ, and organs are part of an organ system
• Organ systems do not work in isolation, they work together and are part of a big team
• 11 major human body systems

  • Circulatory
  • Digestive
  • Endocrine
  • Excretory
  • Integumentary
  • Lymphatic and Immune
  • Muscular
  • Nervous
  • Reproductive
  • Respiratory
  • Skeletal
• Circulatory system


  Transports blood, gases, and nutrients
• Heart


  • Pumping machine that transports blood
  • Has four chambers: right atrium, right ventricle, left atrium, left ventricle
  • Has valves to prevent backflow of blood
• Arteries


  Vessels that typically carry blood away from the heart
• Veins


  Vessels that typically carry blood back to the heart
• Capillaries


  Tiny blood vessels throughout the body
• Blood is always red, though the shade can vary slightly due to the amount of oxygen present
• Digestive system


  Breaks down and absorbs food to provide nutrients
• Digestion


  1. Starts in the mouth with enzymes in saliva

  2. Further processed in the stomach with acid and enzymes

  3. Nutrients absorbed in the small intestine

  4. Water reabsorbed in the large intestine

  5. Waste passes through the anus
• The digestive system includes accessory structures in addition to major structures
• Endocrine system


  Includes glands that secrete hormones, which act as messengers to targets
• Hormones


  Have the ability to act as messengers on the targets they bind to in order for some action to occur