organisation biology topic 2

• What is the topic of the second unit for AQA GCSE biology?

  Organization
• What are cells described as in the context of living organisms?

  Cells are the basic building blocks of all living organisms.
• What do we call a group of cells with similar structure and function?

  A tissue
• What is an organ?

  An organ is a group of tissues performing specific functions.
• What is the term for a group of organs performing a specific function?

  An organ system
• What is the final term used to describe all organ systems together?

  An organism
• What are enzymes primarily made of?

  Proteins
• Where are enzymes typically found?

  Enzymes are found in cells, often working inside them.
• What is the active site of an enzyme?

  The active site is a specific part of the enzyme's structure where the substrate binds.
• How do enzymes function as biological catalysts?


  Enzymes speed up reactions in the body and can be reused without changing their shape.
• What model is used to explain how enzymes work?

  The lock and key model.
• What does it mean for the shapes of the substrate and active site to be complementary?

  It means the substrate fits into the active site, but they are not the same shape.
• What role do enzymes play in metabolism?

  Enzymes control metabolic reactions that build up and break down molecules.
• How can we measure the rate of enzyme-controlled reactions?

  By measuring gas production, color change, or pH change over time.
• What happens to the rate of reaction as temperature increases?

  The rate of reaction increases until it reaches the optimum temperature.
• What is the optimum temperature for many living organisms?

  Approximately 37 degrees Centigrade.
• What occurs to an enzyme when the temperature is too high?

  The enzyme denatures, and the shape of the active site is permanently changed.
• How does pH affect enzyme activity?

  Enzymes work best at their optimum pH, and extreme pH can denature them.
• What is the test for starch?

  The iodine test.
• What color change indicates the presence of starch in the iodine test?

  From orange to blue-black.
• What is the test for protein?

  The Biuret test.
• What color change indicates the presence of protein in the Biuret test?

  From blue to lilac.
• What is the test for lipids?

  The ethanol test.
• What indicates the presence of lipids in the ethanol test?

  A cloudy white emulsion forms.
• What is the test for sugars?

  The Benedict's test.
• What color change indicates the presence of sugars in the Benedict's test?

  From blue to brick red.
• What is the function of bile in the digestive system?

  Bile neutralizes stomach acid and emulsifies fats.
• How does emulsification affect lipid digestion?

  It increases the surface area of fats, making it easier for lipase to act.
• What is the role of the pacemaker in the heart?

  The pacemaker controls the resting heart rate by sending regular impulses.
• What is the structure of arteries?

  Arteries have a narrow lumen, thick muscle layer, and thick elastic tissue layer.
• What is the structure of capillaries?

  Capillaries have very thin walls that are only one cell thick.
• Why are capillaries designed with thin walls?

  To allow for a short diffusion distance for substances.
• What are the key components of the human digestive system?

  • Mouth
  • Esophagus (food pipe or gullet)
  • Stomach
  • Pancreas
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
  • Liver
  • Gallbladder
• What are the key enzymes involved in digestion and their functions?

  • Amylase: Breaks down carbohydrates into simple sugars.
  • Protease: Breaks down proteins into amino acids.
  • Lipase: Breaks down lipids into glycerol and fatty acids.
  • Carbohydrase: Breaks down carbohydrates.
• What are the food tests and their indicators?

  1. Iodine test for starch: Blue-black color indicates starch presence.
  2. Biuret test for protein: Lilac color indicates protein presence.
  3. Ethanol test for lipids: Cloudy white emulsion indicates lipid presence.
  4. Benedict's test for sugars: Color change from blue to brick red indicates sugar presence.
• What are the main functions of the heart and blood vessels?

  • The heart pumps oxygenated blood to the body and deoxygenated blood to the lungs.
  • Blood vessels include arteries (carry oxygenated blood), veins (carry deoxygenated blood), and capillaries (allow for gas exchange).
• What is the structure and function of valves in the heart?

  • Valves prevent the backflow of blood.
  • They open to allow blood flow in one direction and close to prevent backward flow.
• What is the difference between oxygenated and deoxygenated blood?

  • Oxygenated blood carries oxygen from the lungs to the body.
  • Deoxygenated blood carries carbon dioxide from the body back to the lungs.
• What is the significance of the double circulatory system?

  • Blood is pumped to the body and lungs separately.
  • Blood enters the heart twice in one full circuit around the body.
• What are the roles of the liver and gallbladder in digestion?

  • The liver produces bile.
  • The gallbladder stores bile and releases it into the small intestine to aid in lipid digestion.