*BIOLOGY - B2 - transport

• villi 


  tiny hair like projections that line the inside of the small intestine they allow small molecules to be absorbed the the gut wall into the blood stream
• xylem - transport water an minerals

  phloem - transport sugars
• Uptake by diffusion practical

  
• cells need oxygen, water, glucose, mineral ions and nutrients. Cells need to remove carbon dioxide and lactic acid.
• a unicellular organism can rely on diffusion to move substances in and out
• diffusion is the movement of substances from and area of high concentration to low concentration
• volume - ammount of matter in a given area
• amoeba and bacteria can rely on diffusion
• pag-the larger the cube the small the surface area to volume ratio, substances would diffuse in and out more slowly sue to the size of the cube
• what is an exchange surface?

  an area that allows substances to move from one area to the other e.g, alveoli within lungs and villi in the small intestine
• why do we need exchange surfaces?

  to increase surface area to volume ratio

  shorten diffusion distance
• AVEOLI DIAGRAM

  
• alveoli allows the exchange of oxygen and carbon dioxide within the lungs to enter the bloodstream
• diffusion - due to the random movement by particles it is a passive process which means that no energy is needed
• concentration gradient is the difference between 2 areas
• factors effecting diffusion:

  concentration gradient

  temperature

  distance particle must travel faster when:

  large conc gradient

  higher temp and shorter distance
• Cellular diffusion diagram

  
• Diffusion and the leaf

  
• cellular diffusion 


  substances move in and out of cells by diffusion across a PARTIALLY PERMEABLE MEMBRANE
• Active transport

  
• Active transport 


  requires energy (ATP) to move molecules from an area of low concentration to an area of high concentration

  against the concentration gradient

  e.g mineral ions moving into root hair cells, glucose in small intestines
• active transport diagram

  
• Diffusion and active transport

  
• osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
• solute 


  something that dissolves e.g salt and sugar
• water potential is the concentration of free water molecules, a measure of the ability of water molecules to move freely is a solute
• plant cells and osmosis:

  TURGID: water moves into the vacuole and pushes on the cell wall

  move solutes inside the cell that outside

  FLACID: water moves out of the vacuole

  move solutes outside the cell

  PLASMOLYSED: too much water leaves the vacuole, the cell membrane pulls on the cell wall , more solutes outside the cell than inside
• Animal cells and osmosis:

  SHRIVELLED: water moves at the cells and shrivels, more solutes outside the cell

  NORMAL: no net movement of water, equal level of solutes inside and out.

  LYSIS: water moves into the cell it bursts as there is no cell wall. more solutes inside the cell than out
• Exchange surface

  
• Osmosis Practice problems

  
• hypotonic solutions: contains lots of solutes, water will leave cell if in thsi solution
• hypertonic: contains very little solutes water will enter cells if in this solution.
• isotonic solutions: equal concentration of solutes inside and outside the cell no net movement of water.
• Osmosis potato practical

  
• Osmosis potato practical pt2

  
• Osmosis practical graph

  
• circulatory system:

  made up of the heart and blood vessels as blood remains in these structures it is known as a closed system
• red = oxygenated blood, oxygen attached to red blood cells by haemoglobin

  blue = deoxygenated blood, lack of oxygen attached to red blood cells

  lumen describes the gap between the blood vessels
• Circulation x

  
• Diffusion, osmosis and at