Cellular transport

• The plasma membrane regulates the flow of liquids, dissolved solids and gases, in and our of the cell. It provides structure for the cells to act as a specialised unit. It protects the cytosolic contents from the environment
• The plasma membrane is responsible for maintaining the homeostasis of the cell
• cell membranes are semi permeable, what does this mean?


  They have control over which molecules can or cannot pass through.
• What is diffusion?


  the net movement of substances from an area of a high concentration to a low concentration, down a concentration gradient
• Net movement is the overall movement
• In diffusion, the molecules are always moving, even when equilibrium is reached
• Passive transport uses no energy, what are the two examples of this?


  diffusion and osmosis
• Active transport requires energy, as the molecules are moving against the regular flow
• the cell membrane contains pumps that require energy that they receive in the form of ATP
• What is ATP?


  a cell currency or energy store that is produced by the mitochondria
• osmosis is when water moves down a concentration gradient, across a partially permeable membrane
• What are solutes?


  substances that can be dissolved in solvents
• What are some examples of where active transport takes place?


  mineral ions into plant roots, glucose from the gut into intestinal cells
• What are the types of active transport?


  Endocytosis, exocytosis, pinocytosis, phagocytosis
• Intracellular means inside the cell
• Extra cellular means outside the cell
• Pinocytosis is the same as phagocytosis, except the cells’ plasma membrane surrounds droplets of fluid containing dissolved solutes
• The sodium potassium pump helps maintaining a resting membrane potential of the cell
• What is the resting membrane potential?


  when cells contain ions on both sides of the membrane, not in equal ratios
• What does the sodium potassium pump do?


  pumps sodium out and potassium in the cell
• In the sodium Potassium pump, ions can be positive OR negative. it is maintains the electrical potential of the membrane
• Why is endocytosis important?


  Most molecules needed for the cell to survive cannot normally pass through the plasma membrane
• What happens in exocytosis?


  Material is exported out the cell via secretory vesticles
• Why is exocytosis important?


  it removes waste materials from the cell and secretes cellular products such as hormones and enzymes
• Facilitated diffusion is when molecules still have a net movement of particles moving down a concentration gradient, but they may be too large or have other characteristics that prevent them from directly travelling across the selective cell membrane, therefore, they have to go through a protein channel
• What are some factors that affect the rate of diffusion?


  distance, temperature, characteristics of the solvent/molecules/barrier
• where does the energy in facilitated diffusion come from?


  a concentration is a form of potential energy for this process
• What does hypertonic mean?


  when a substance has a higher solute concentration
• What does hypotonic mean?


  when a substance has a lower solute concentration
• What does isotonic mean?


  when two things are of equal concentration
• The cell membrane is made up of a phospholipid bilayer, two layers of lipids which have a polar head and a non polar tail
• What does it mean when a molecule is polar?


  they have an unequal sharing of electrons amongst atoms
• What does it mean when a molecule is non polar?


  They have an equal sharing of electrons amongst atoms
• very small, non polar molecules can directly pass through the phospholipid bilayer, this is simple diffusion
• What are transport proteins?


  some act as channels, some change their shape to get things across, some open and close based on some kind of stimulus
• Polar molecules need the help of transport proteins in order to pass the cell membrane on their own, this is facilitated diffusion
• In facilitated diffusion, the proteins help things pass
• what is active transport?


  the movement of molecules down a concentration gradient
• Why does active transport require energy?


  because the movement of molecules is against the regular flow, so energy is required to make them move the opposite direction
• Active transport typically requires ATP energy, which is made up of three phosphates. When the bond for the last phosphate is broken, it releases a great amount of energy. This forces molecules to go against their concentration gradient