ORGANISATION TOPIC 2 CHANTELLE

• Cells


  Basic building blocks of all living organisms
• Unicellular organisms


  Made from one cell
• Multicellular organisms


  Made up of collections of cells
• Complex multicellular organisms


  • Cells are specialised to carry out particular functions
  • Specialised cells form tissues
  • Tissues form organs
  • Organs form organ systems
• Organ systems in humans

  • Digestive system
  • Respiratory system

  
• Organ systems


  Provide dissolved materials that need to be moved quickly around the body in the blood by the circulatory system
• Digestion


  A process in which relatively large, insoluble molecules in food are broken down into smaller, soluble molecules that can be absorbed into the bloodstream and delivered to cells in the body
• Small soluble molecules from digestion

  • Glucose
  • Amino acids
• Alimentary canal


  The channel or passage through which food flows through the body, starting at the mouth and ending at the anus
• Accessory organs


  Produce substances that are needed for digestion to occur (such as enzymes and bile)

  
• Stomach


  Starts protein digestion by producing proteases like pepsin, which digest proteins into amino acids
• Acid in stomach


  Aids protein digestion by helping proteins unravel so enzymes can break the bonds holding the amino acids together, and inhibits microorganisms

  
• Large intestine


  Home to hundreds of species of bacteria that play an essential role in human digestion of food

  
• Role of gut bacteria


  • Break down substances we can't digest
  • Supply essential nutrients
  • Synthesise vitamin K
  • Provide competition with harmful bacteria
• Antibiotics


  Can disrupt the gut microbiota and cause short-term problems with digestion
• Digestive enzymes


  Work outside of cells to digest large, insoluble food molecules into smaller, soluble molecules which can be absorbed into the bloodstream
• Metabolism


  The sum of all the reactions happening in a cell or organism, in which molecules are synthesised (made) or broken down
• Enzymes


  Biological catalysts made from protein that speed up chemical reactions in cells

  
• Enzyme action


  1. Substrates temporarily bind to the active site

  2. Chemical reaction occurs

  3. Products are released

  4. Enzyme remains unchanged

  
• Enzyme specificity


  The complementary nature between the shape of the active site on the enzyme and its substrate(s)

  
• Enzyme shape


  Determined by the order of amino acids in the protein

  
• Lock and key model

  Enzyme is like a lock, substrate is the key that fits into the active site
• Induced-fit model


  Substrate and active site change shape slightly to fit more perfectly together
• Optimum temperature for enzymes

  Around 37°C in the human body
• Denaturation


  Breaking of bonds that hold the enzyme together, causing loss of shape and activity

  
• Increasing temperature from 0°C to optimum

  Increases enzyme activity

  
• Optimum pH for most enzymes

  pH 7
• Acidic/alkaline conditions


  Can cause enzymes to denature and lose activity
• Carbohydrases


  Break down carbohydrates to simple sugars
• Amylase


  A carbohydrase that breaks down starch into maltose, then maltase breaks down maltose into glucose
• Proteases


  Break down proteins into amino acids
• Pepsin


  A protease enzyme made in the stomach
• Lipases


  Break down lipids (fats) to glycerol and fatty acids
• Bile


  Produced in the liver, stored in the gallbladder, has two main roles: neutralise stomach acid and emulsify fats
• Products of digestion


  Used to build new carbohydrates, lipids, proteins, and for respiration to release energy

  
• Adaptations of gas exchange surfaces

  • Large surface area
  • Thin walls
  • Good ventilation
  • Good blood supply
• Diffusion


  The process by which gas exchange occurs
• Ventilation of the lungs

  1. Air passes through trachea, bronchi, bronchioles, alveoli

  2. Diaphragm contracts to increase chest cavity volume and draw air in

  3. Diaphragm relaxes to decrease chest cavity volume and expel air
• Ventilation of the lungs

  Air passes through the following structures when we breathe in: Trachea, Bronchus (plural: bronchi), Bronchiole, Alveoli (the site of gas exchange where oxygen diffuses into the blood and carbon dioxide diffuses out)
• Diaphragm


  • A thin sheet of muscle that separates the chest cavity from the abdomen; it is ultimately responsible for controlling ventilation in the lungs
  • When the diaphragm contracts it flattens and this increases the volume of the chest cavity (thorax), which causes a decrease in air pressure inside the lungs relative to outside the body, drawing air in
  • When the diaphragm relaxes it moves upwards back into its domed shape and this decreases the volume of the chest cavity (thorax), which causes an increase in air pressure inside the lungs relative to outside the body, forcing air out