2.1.5

• All cells contain...

  a plasma membrane containing a phospholipid bilayer
• Phospholipid bilayer structure

  A) hydrophobic

  B) hydrophilic

  C) phosphate head

  D) lipid tail

  
• the hydrophobic centre of the phospholipid bilayers allows...

  only other hydrophobic molecules to pass through

  It prevents any charged or large molecules passing through

  separate two aqueous regions
• functions of a cell membrane inside a cell

  barrier between organelle and cytoplasm

  Separates the internal contents of organelles

  Location of chemical reactions
• functions of a cell membrane outside the cell

  Barrier between cytoplasm and environment

  Site of cell signalling

  allow formation of concentration gradients
• the fluid mosaic model gets its name because...

  the phospholipid molecules can move making the membrane flexible

  the surface is randomly covered in proteins
• Fluid mosaic model diagram

  A) carrier protein

  B) channel protein

  C) intrinsic protein

  D) extrinsic protein

  E) cholesterol

  F) glycolipid

  G) glycoprotein

  
• cholesterol function in bilayer

  Interacts with fatty tails decreasing fluidity, increasing stability and decreasing the movement of water soluble molecules across the membrane
• protein channel function

  allows water soluble molecules and ions to diffuse through the membrane
• carrier protein function

  change shape to transfer large molecules or ions from one side of the membrane to the other
• Glycoprotein function

  allows tissue formation

  present as antigens

  act of hormone receptors
• glycolipid function

  used to recognise other cells

  can act as antigens
• diffusion

  the net movement of particles to an area of high concentration to an area of lo concentration down the concentration gradient
• equilibrium

  no net movement of particles
• diffusion is what type of process?

  passive , requires no metabolic energy as particles have their own kinetic energy already
• factors affecting diffusion across a plasma membrane:

  concentration gradient - the greater the gradient the greater the diffusion

  particle size / charge - due to a membranes hydrophobic core and tightly packed bilayer

  temperature - the higher the temperature the more kinetic energy particles have the faster they diffuse

  surface area - the greater the membrane area the more diffusion can occur

  distance - the greater the diffusion distance the slower the rate of diffusion

  presence of carrier / channel protein - facilitated diffusion
• not all substances diffuse across the cell membrane at the same...

  rate due to the hydrophobic centre
• what molecule is the exception to a membranes hydrophobic centre?

  water as its molecules are very small
• facilitated diffusion

  large or hydrophilic substances diffuse across the cell membrane via protein molecules
• facilitated diffusion is what type of process?

  passive , requires no metabolic energy
• Protein channel diagram

  A) hydrophilic

  B) selective

  C) triggered

  
• Carrier protein diagram

  A) specific

  B) binding

  C) tertiary

  
• active transport

  the movement of particles from an area of low concentration to an area of high concentration against the concentration gradient
• active transport is what type of process?

  active , requires metabolic energy
• in a cell membrane active transport requires?

  carrier proteins
• Active transport diagram

  A) site

  B) carrier

  C) p

  D) adp

  E) p

  
• osmosis

  the net movement of water molecules from an area of higher water potential to an area of low water potential through a partially permeable membrane
• water potential ψ


  the pressure exerted by water molecules on a membrane ( kPa)
• pure water has a water potential of

  0
• a solution has a water potential with a charge of 


  -
• the more concentrated a solution...

  the lower the water potential
• water will always move to an area with..

  the lowest water potential
• when water moves into a cell via osmosis what pressure increases?

  hydrostatic pressure inside the cell increases
• haemolysis

  the bursting of a red blood cell due to extreme hydrostatic pressure
• cell bursting due to high hydrostatic pressure does not occur in plant cells because...

  they have a cell wall so the cell only becomes turgid
• plasmolysis

  occurs when water moves out of the cell via osmosis causing the cell membrane to separates from the cell wall. The gap fills up with the solution previously outside the cell.
• endocytosis and exocytosis are what types of processes?

  active , require metabolic energy to occur
• Endocytosis diagram

  A) cavity

  B) vesicle

  C) into

  
• exocytosis diagram

  A) golgi

  B) apparatus

  C) vesicles

  D) vesicles

  E) fuse

  
• endocytosis involves

  entering