Transport in cells

• What is diffusion?


  The spreading out of particles from an area of higher concentration to an area of lower concentration
• Which types of molecules can diffuse through cell membranes?


  Very small molecules, such as oxygen and glucose
• What factors increase the rate of diffusion across a cell membrane?


  1. A high concentration gradient
  2. A high temperature
  3. A large surface area
• What is osmosis?


  The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
• What is active transport?


  The movement of a substance against the concentration gradient
• What is required for active transport that is not required for diffusion and osmosis?


  Energy from respiration
• What are two examples of substances absorbed through active transport?


  • Mineral ions for plant growth from soil into root hair cells
  • Glucose for cell respiration from the gut into the bloodstream
• What is diffusion?


  Diffusion is the gradual movement of particles from areas of higher concentration to areas of lower concentration.
• Why do particles diffuse?


  Particles diffuse due to their natural tendency to spread out evenly.
• In which states of matter does diffusion occur?


  Diffusion occurs in both solutions and gases.
• What is an example of diffusion in gases?


  The smell of perfume diffusing through the air in a room is an example of diffusion in gases.
• How does the concentration gradient affect the diffusion rate?


  A larger concentration gradient results in a faster diffusion rate.
• How does temperature influence diffusion?


  A higher temperature increases the diffusion rate because particles have more energy and move faster.
• What are the functions of cell membranes in relation to diffusion?


  • Hold the cell together
  • Allow substances to move in and out by diffusion
• What types of molecules can diffuse through cell membranes?


  Very small molecules like oxygen, glucose, amino acids, and water can diffuse through cell membranes.
• Why can't large molecules like starch and proteins diffuse through cell membranes?


  Large molecules cannot fit through the cell membrane.
• How does the movement of particles occur across the cell membrane?


  Particles move from areas of higher concentration to areas of lower concentration, but they move randomly in both directions.
• What effect does the surface area of the membrane have on diffusion rate?


  A larger surface area of the membrane increases the diffusion rate because more particles can pass through at once.
• What is osmosis?


  The movement of water molecules across a partially permeable membrane
• How does osmosis differ from diffusion?


  Osmosis specifically refers to the movement of water molecules
• What type of membrane is involved in osmosis?


  A partially permeable membrane
• What is a characteristic of a partially permeable membrane?


  It has very small holes that allow tiny molecules to pass through
• Why do water molecules move during osmosis?


  Because there are more water molecules on one side than the other
• What happens to the concentration of a strong sugar solution during osmosis?


  It becomes more dilute as water moves in
• What is the definition of osmosis in terms of diffusion?


  Osmosis is a type of diffusion of water particles
• What is the procedure to observe osmosis using potato cylinders?


  1. Cut potato into identical cylinders.
  2. Prepare beakers with different sugar solutions (including pure water).
  3. Measure the mass of each cylinder.
  4. Leave cylinders in solutions for 24 hours.
  5. Dry and measure the mass again.
  6. Calculate percentage change in mass.
• What is the dependent variable in the osmosis experiment with potato cylinders?


  The chip mass
• What is the independent variable in the osmosis experiment with potato cylinders?


  The concentration of the sugar solution
• What factors must be controlled to ensure a fair test in the osmosis experiment?


  • Volume of solution
  • Temperature
  • Time
  • Type of sugar used
• What errors might occur during the osmosis experiment?


  Potato cylinders not fully dried or water evaporation from beakers
• How can the effect of errors be minimized in the osmosis experiment?


  By repeating the experiment and calculating a mean percentage change
• What is the concentration of a very concentrated sugar solution used in the experiment?


  1 mol/dm³
• What is the significance of measuring the percentage change in mass of potato cylinders?


  • Indicates the net movement of water
  • Helps to quantify the effect of different sugar concentrations
  • Allows comparison between different experimental conditions
• What is the process called when substances are absorbed against a concentration gradient?

  Active transport
• How do root hair cells contribute to a plant's ability to absorb water and minerals?


  • Root hairs grow into the soil
  • Millions of microscopic hairs increase surface area
  • Allows absorption of water and mineral ions
• Why do plants need mineral ions from the soil?

  For healthy growth
• Why can't root hair cells use diffusion to take up minerals from the soil?


  Because the concentration of minerals is usually higher in the root hair cells than in the soil
• What happens to minerals if they followed the rules of diffusion in root hair cells?


  They would move out of the root hairs
• What is the method used by root hair cells to draw in minerals?

  Active transport
• What does active transport allow plants to do regarding mineral absorption?


  Absorb minerals from a very dilute solution against a concentration gradient