Transport in cells

• What is diffusion?

  The net movement of particles from an area of high concentration to an area of low concentration.
• What three main factors affect the rate of diffusion?

  Surface Area

  Temperature

  Concentration Gradient
• How does Surface Area affect the rate of diffusion?

  Larger surface area means a faster diffusion
• Give examples of substances that are transported by the diffusion in the lungs and kidneys.

  Lungs: oxygen diffuses into the blood from the lungs and carbon dioxide diffues in the lungs from the blood during gaseous exchange, both down their concentration gradient.

  Kidney: Urea diffuses from cells into blood plasma so it can be excreted via urine.
• How are single-cell organisms adapted for diffusion?

  High surface area-to-volume ratio.
• How is surface area to volume calculated

  Surface area = Number of sides.

  Volume = Length x Width x Depth.

  Ratio = Surface Area:Volume

  
• What four factors increase the effectiveness of gas exchange surface.

  Large surface area.

  Thin membrane (short diffusion path)

  Efficent Blood supply (Animals)

  Ventaliation (Animals)
• What is osmosis?

  Osmosis is the movement of water molecules from an area of lower solute concentration to an area of higher solute concentration across a partially-permeable membrane.
• What is meant when a substance is isotonic to a cell?

  The concentration of the external and internal (inside the cell) solutions are the same.
• What is meant when a solution is hypertonic to a cell

  The concentration outside the cell, external, is higher then the concentration inside the cell.
• What is meant when a solution is hypotonic to a cell?

  The concentration outside the cell, external, is lower then the internal, inside the cell.
• What may happen when an animal cell is placed in a hypotonic solution?

  Water moves into the cell, causing it burst.
• What happens when an animal cell is placed in a very hypertonic solution?

  Water moves out of the cell causes it to shrivel up.
• How do plant cells and stems remain rigid?

  Turgor pressure - water moves in via osmosis and causing the vacoule to swell and the cytoplasm to press against the cell wall
• What may happen when a plant cell is placed within a very hypertonic solution?

  Water moves out of the cell by osmosis. The vacoule and cell wall decrease in size. The cell membrane may pull away from the cell, causing the cell to become plasmolysed.

  
• Label this:

  A) Hypertonic

  B) Plasmolysed

  C) Isotonic

  D) Flaccid

  E) Hypotonic

  F) Turgid

  
• What is active transport?

  Active transport is the movement of particles from a more dilute solution to a more concentrated solution against a concentration gradient, using energy from respiration (glucose).
• How do plant root cells use active transport?

  Root hair cells use mineral ions from a more dilute solution in soils. Ions such as magnesium and nitrates are required for healthy growth.
• How is active transport used to absorb the products of digestions?

  Active transport is used to transport glucose from a lower concentration in the gut to a higher concentration in the blood. Glucose is then transported to the tissues where it can be used in respiration.