movement of substances into and out of cells

• osmosis is the movement of a substance from an area of high water concentration to an area of low water concentration against a partially permeable membrane
• the effect of osmosis in animal cells is : when water enters, the cell will swell & burst and when water leaves, the cell will shrivel up known as crenation
• the effect of osmosis on plant cells is: when water enters the cell will swell with water and become turgid and when water leaves the cell loses water, the cell membrane pulls away from the cell wall and is plasmolysed
• animal cells don't have a cell wall so if they gain too much water by osmosis, they will swell and burst known as cell lysis
• flaccid means the cell contents will shrink and pull away from the cell wall
• in pure water, a plant cell will swell up because the water outside the cell is at a higher concentration than the water in the cell.
• in a concentrated solution, the plant cell contents lose water by osmosis and become flaccid
• in a highly concentrated solution, the plant cell goes through plasmolysis which means its protoplasm shrinks as the cell loses more water
• an animal cell in pure water means water will enter the cell due to osmosis and the cell will swell up and become turgid
• and animal cell in a concentrated solution means water is sucked out of the cell by osmosis and the cell shrinks
• diffusion is the net movement of particles from an area of high to low concentration. the movement is random and requires no energy
• active transport is the movement of a substance from an area of low to high concentration across a partially permeable membrane. it requires energy to take place
• active transport moves a substance against its concentration gradient
• osmosis and diffusion move substances down the concentration gradient
• factors the affect movement are diffusion distance, concentration gradient, surface area to volume ratio and temperature
• if the diffusion distance is small, diffusion happens faster because the particles do not have as far to travel
• the higher the concentration gradient, the faster the rate of diffusion
• the smaller the surface area, the lower the rate of diffusion
• higher temperatures increase the energy and movement of the molecules increasing the rate of diffusion
• the alveoli in the lungs have walls which are one cell thick which allows oxygen and carbon dioxide to move quickly through them
• What are the three processes by which substances move into and out of cells?

  Diffusion, osmosis, and active transport
• How does temperature affect the rate of movement of substances into and out of cells?

  Higher temperatures increase kinetic energy, leading to faster movement
• What is the effect of increasing the surface area to volume ratio on the rate of diffusion?

  A larger surface area to volume ratio increases the rate of diffusion
• What is the difference between diffusion and osmosis?

  Diffusion is the movement of particles, while osmosis specifically refers to the movement of water
• What is diffusion?

  Movement of particles from high concentration to low concentration
• What happens to a plant cell placed in pure water?

  The cell becomes turgid as water enters and pushes against the cell wall
• What occurs to red blood cells in a concentrated solution?

  They shrivel as water leaves the cells
• What is active transport?

  Movement of particles from low concentration to high concentration using ATP
• What role do carrier proteins play in active transport?

  They help move substances against the concentration gradient
• How does distance affect the rate of diffusion?

  Shorter distances allow for faster diffusion rates
• What is the significance of the concentration gradient in diffusion?

  A steeper concentration gradient results in a faster rate of diffusion
• What happens to the surface area to volume ratio as cell size increases?

  The surface area to volume ratio decreases
• Why do multicellular organisms require organ systems for substance exchange?

  They have a larger distance from the surface to the inside, making diffusion insufficient
• How does temperature affect the kinetic energy of atoms?

  Higher temperatures increase the kinetic energy of atoms
• What is the method to investigate diffusion using agar cubes?

  • Collect agar cubes of different sizes.
  • Use 0.1 M sodium hydroxide and phenolphthalein for color.
  • Place cubes in 0.5 M hydrochloric acid for 1 minute.
  • Measure the distance of color change after washing.
• What is the method to investigate osmosis using potato strips?

  • Cut equal-sized potato strips.
  • Weigh the starting mass.
  • Place in different concentrations of sucrose solution.
  • Leave for a few hours, then reweigh.
• What is the formula for percentage change in mass?

  Percentage change = (end mass - start mass) / start mass × 100
• What do the results of the potato osmosis experiment indicate about sucrose concentration?

  As sucrose concentration increases, mass loss from the potato increases
• What happens to Visking tubing in a 6% sugar solution after one hour?

  It expands as it gains water due to lower concentration of water inside
• What happens to Visking tubing in an 18% sugar solution after one hour?

  It gets floppy as it loses water due to higher concentration of sugar outside