biology

• Why are enzymes important for living cells?

  Enzymes are important because they enable living cells to carry out numerous chemical reactions quickly.
• What is the problem with increasing the temperature to speed up chemical reactions?

  Increasing temperature can require a lot of energy, damage cells, and accelerate unwanted reactions.
• What is a catalyst?

  A catalyst is a substance that increases the speed of a chemical reaction without being changed or used up.
• How can catalysts be reused in chemical reactions?

  Catalysts can be reused because they are not changed or consumed in the reaction process.
• What is an enzyme?

  An enzyme is a specific type of catalyst made by living organisms.
• What are enzymes made of?

  Enzymes are made of long chains of amino acids, which fold to form unique shapes.
• What factors are being examined in relation to enzyme activity in this video?

  Temperature and pH
• How does temperature affect the rate of enzyme-controlled reactions?

  • Rate increases with temperature due to higher kinetic energy
  • Rate drops after about 37 degrees as enzymes begin to denature
  • Denaturation occurs around 45 degrees, causing permanent damage
• What role do substrates play in enzyme reactions?

  Substrates are the reactants that enzymes act upon to produce products.
• At what temperature does the rate of enzyme-controlled reactions start to drop rapidly?

  About 37 degrees
• What happens to enzymes at high temperatures?

  High temperatures break bonds holding enzymes together, changing the active site's shape
• What is the term used when an enzyme can no longer bind to its substrate due to shape change?

  Denatured
• What is the optimum temperature for enzyme activity mentioned in the video?

  37 degrees
• What is optimal temperature in relation to enzymes?

  • The temperature at which the rate of reaction is highest
  • Different enzymes have different optimal temperatures
• What is the active site of an enzyme?

  The active site is a specific region of the enzyme that has a unique shape complementary to the substrate.
• How does pH affect enzyme activity?

  • pH measures acidity; extreme pH levels lower the rate of reaction
  • High or low pH can break bonds holding the enzyme together
  • Enzymes can become denatured at extreme pH levels
• What is the optimal pH for most enzymes in the human body?

  About 7 (neutral pH)
• What is the optimal pH for enzymes that function in the stomach?

  About 2
• What happens to the active site of an enzyme when pH changes?

  • Initially changes shape slightly, slowing down the reaction
  • Eventually changes shape so much that the substrate cannot fit
  • This leads to denaturation of the enzyme
• What happens if a substrate does not fit the active site of an enzyme?

  If the substrate does not fit the active site, the reaction will not be catalyzed.
• What are the two main models of enzyme action?

  • Lock and Key Model: Substrates fit perfectly into the active site.
  • Induced Fit Model: Enzyme changes shape slightly to fit the substrate better.
• How did the understanding of enzyme action change from the lock and key model to the induced fit model?

  Scientists now understand that enzymes change shape slightly to fit substrates better, rather than fitting perfectly like a key in a lock.
• How can you describe the induced fit model using a common analogy?

  • The induced fit model can be likened to putting your hand into a rubber glove, which molds around your hand for a perfect fit.
• Why can single-celled bacteria rely on diffusion for substance exchange?

  Because they have a high surface area to volume ratio.
• What do large multicellular organisms require for substance exchange instead of diffusion?

  They require specialized exchange surfaces and transport systems.
• What resources do single-celled organisms need to absorb from their surroundings?

  Oxygen, glucose, and amino acids.
• What waste products do single-celled organisms need to get rid of?

  Carbon dioxide.
• How does the surface area to volume ratio change as organisms get larger?

  The surface area to volume ratio decreases as organisms get larger.
• How is the surface area of a cube calculated?


  • Calculate the area of one face (length × width).
  • Multiply by 6 (since a cube has six faces).
• What is the surface area of a cube with a side length of 1 cm?

  6 square centimeters.
• What is the volume of a cube with a side length of 1 cm?

  1 cubic centimeter.
• For a medium cube, what is the surface area and volume?

  Surface area is 24 square centimeters and volume is 8 cubic centimeters.
• For the largest cube, what are the surface area and volume?

  Surface area is 54 square centimeters and volume is 27 cubic centimeters.
• How does the increase in size affect the surface area and volume of cubes?

  As cubes get larger, their volume increases more quickly than their surface area.
• Why do larger organisms require specialized exchange surfaces?

  Because they have a low surface area to volume ratio, making diffusion insufficient.
• What specialized structures do humans have for gas exchange?

  Humans have lungs with millions of alveoli.
• What structures in the intestines help with nutrient absorption?

  The intestines have villi that increase surface area for absorption.
• How does diffusion distance change as organisms get larger?

  The diffusion distance increases significantly as organisms get larger.
• How much further do molecules have to diffuse in humans compared to bacteria?

  Molecules have to diffuse 50,000 times further in humans than in bacteria.
• What transport systems do larger organisms often have?

  Larger organisms often have circulatory systems to transport molecules.