GCSE Biology (B2)

• Organelles


  Also called subcellular structures, the parts that make up a cell like the nucleus, ribosomes, and mitochondria
• Organelles


  • Each individual organelle has a specific role to play
  • When combined, multiple organelles will form a single cell
• Cells


  Come in all sorts of shapes and sizes and contain different combinations and numbers of organelles
• Specialized cells


  Different types of cells like epithelial cells, muscle cells, and glandular cells
• Tissues


  A group of similar cells that work together to carry out a particular function
• Tissues


  • Epithelial tissue
  • Muscle tissue
  • Glandular tissue
• Organs


  A group of different tissues that work together to perform a particular function
• Organs


  • Stomach
  • Pancreas
  • Liver
• Organ systems


  A group of organs that work together to perform a particular function
• Organism


  The highest level, with multiple organ systems working together
• Enzymes


  Catalysts made by living organisms
• Enzymes


  • They are large proteins made up of long chains of amino acids
  • They can fold into different shapes, each shape catalyzing a particular chemical reaction
• How enzymes work

  1. Enzyme has an active site with a unique shape

  2. Substrate fits into active site

  3. Enzyme speeds up the chemical reaction
• Substrate


  Reactant in a chemical reaction
• Products


  Smaller pieces that a substrate is broken into
• Enzymes speed up chemical reactions without being consumed or changed in the process
• Lock and key model


  • Substrate has to fit perfectly into the active site of the enzyme
• Induced fit model


  • Enzyme changes shape slightly to better fit the substrate
• The active site of an enzyme is complementary to the substrate
• The induced fit model is more realistic than the lock and key model
• Anki.com has a learning platform with videos, practice questions and progress tracking for sciences and maths
• How temperature and pH affect the functioning of enzymes and the rate of enzyme controlled reactions

  1. Increase in temperature increases rate of reaction

  2. Rate starts to drop rapidly at high temperatures due to bonds breaking and active site changing shape

  3. Enzyme becomes denatured at high temperatures

  4. Optimal temperature is the temperature at which rate of reaction is highest
• Denatured


  Enzyme cannot bind to substrate and catalyze reaction anymore due to active site changing shape
• Optimal temperature


  Temperature at which rate of reaction is highest
• How pH affects enzymes

  1. If pH gets too high or too low, it will lower the rate of reaction

  2. At first, active site just changes a bit so substrate can still fit but less well

  3. Soon, active site changes shape so much that substrate can't fit at all and enzyme becomes denatured
• Optimal pH


  pH at which enzyme works best
• Most enzymes in our body work best at neutral pHs of around 7
• Enzymes that work in the stomach have an optimal pH of around 2 to function in the acidic environment
• Foods normally have a mix of different nutrients in them, not just one
• Carbohydrates

  Found most in starchy foods like bread, pasta and potatoes, as well as in fruits and vegetables. Provide energy for chemical reactions and movement.
• Lipids


  Fats and oils. Found in oily fish, nuts, seeds, dairy products and avocados. Provide energy and insulation, protect organs.
• Proteins


  Found in nuts, seeds, meat, fish, legumes. Act as building blocks for growth and repair of tissue. Can also provide energy.
• Vitamins


  Organic molecules made by living organisms. Needed in small amounts. Examples: Vitamin A, C, D.
• Mineral ions


  Inorganic, simple molecules. Needed in small amounts. Examples: Calcium, Iron.
• Fiber


  Type of carbohydrate not absorbed into the body. Found in wholemeal foods, fruits and vegetables. Helps food move through intestines.
• Water


  Needed for chemical reactions, makes up about 70% of the body. Obtained from drinks and water-rich foods.
• Enzymes


  Essential for helping us break down the large molecules that we eat into the much smaller soluble molecules that we can absorb through our intestinal lining
• Main groups of nutrients to be broken down

  • Carbohydrates
  • Proteins
  • Fats
• Carbohydrates


  Found mainly in foods like pasta, potatoes and rice, used by the body mainly as an energy source
• Starch


  The main type of carbohydrate