5.3- Diffusion Flashcards
Whta is simple diffusion>
The net movement of particles from a region of high to low concentration
PASSIVE
Why does simple diffusion occur
The particles in gas or liquid have kinetic energy
This movement is random adn an unequal distribution eventual becomes equal - particles on stop but movement is equal in both directions
Why is diffusion fast over fast distance but slow over large
Because particles move at high speed
Collid lots- large
Plasma membrane- simple diffusion
Small lipid soluble, uncharged molecules
Random process relying on kinetic energy of particles
E,g, o2, co2, h20, steroid hormones
What is facilitate diffusion
The hydrophobic interior of the membrane repels substances sith a positive or negative charge
Polar molecules e.g. H20 move at SLOW rate
Transmembrane channels- gated , open adn closed - regulating flow of ions or small polar molecules
Can also involve carrier proteins which change chaos when a specific molecule binds
Carrier proteins
Down a. Concentration gradient
Doesn’t require EXTERNAL energy
PASSIVE
Factors affecting rate of diffusion
Temperature- higher temp= higher rate of diffusion= more Ke adn more speed
Concentration difference= greater means faster
Surface area= as surface area to volume ratio increase sm so does diffusion rate
Distance- greater= slower
Size of molecule
Simple diffusion summar
I assisted diffusion
Occurs through phospholipids
Transports small, non polar particles
Occurs directly through cell surface membranes
Rat of diffusion is directly proportional to concentration gradient and membrane permeability of solute molecule
FACILITATED diffusion summary
Transport a substance across a biological membrane
Carrier protein or protein channels
Movement of molecules down grading
Large and polar
Rate depends on kinetics of carrier- meditated transport
Differentiation
Different cell types have differnent membranes with different proportions of protein channels and carriers
Why is diffusion not enough to met the needs of the cell
Moving LARGE amounts
Ensuring one way flow
Concentration gradient- so you can go from low to high
Speed - diffusion isn’t very fast
What is active transport
The movement of ions or molecules against concentration gradient across membranes
Uses ATP to drive protein ‘oumps’ within membrane
Active transport across plasma membranes
- The molecule or ion binds t the receptors in the channel f the carrier protein on the outside of the cel
- On the inside of the cell , atom binds to the carrier protein adn is hydrolysed to ADP adn Pi
- Binding of the phosphate molecule to the carrier protiens causes the protein to change shape ( active configuration) opening up to the inside of the cell
- The molecule or ion is released inside the cell
- The phosphate molecule is released form the carrier protein and recombined with ADP to form ATP
- The carrier protein returns to original shape ( binding configuration ) available to take up glucose
What is bulk transport
Another form of active transport
Large molecules like enzymes , hormones or whole cells like bacteria are too large to move through channel or Carrier proteins
Phagocytosis
Solids
Phinocytosis
Liquids
Endocytosis
Bulk transport- moving into cells
1. The cell membrane first invaginates ( bends inwards) when it comes into contact with the material to be transported
- The membrane enfolds the material until eventually the membrane fuses, forming a vesicle
- The vesicle pinches off and moves into the cytoplasm, to transfer the material for any further processing within the cell
Exocytosis
Leaving cell
Vesicle moves towards an fuses with cel surface membrane
Content of the vesicle released outside outside of the ell
What is osmosis
Net movement of water molecules to an area of HIGH to LOW water potential
Partially permeable membrane
Type of diffusion
Water potential
A measure of the water molecule concentration, which are able to diffuse
Pascals or kPa
Psi
Pure water water potential
O pka - so everything else has a negative water potential
Animal cells- hypotonic solution
Cell membrane burst
Water moves into cell by osmosis
Hydrostatic pressure increases inside the cell adn membrane cannot withstand pressure
What is a hypotonic solution
When cell is placed in solution with a HIGHER water potential than the cytoplasm
What is a hyper tonic solution?
When cell is placed ina solution with a LOWER water potential than the cytoplasm
What is cremation
REDUCTION in volume of cell surface membrane to pucker
Placed in hypertonic solution
Water leaves cell by osmosis
Reduction in volume of cell
Red blood cells- hypertonic and hypotonic solutions
HAEMOLYSIS- haemoglobin released
Crenation- haemoglobin more concentration, giving cell a darker appearance
Plant cells- hypotonic
Tugor
Water enters
Increased hydrostatic pressure pushed membrane against cell wall
Tugor pressure increase preventing more water entering
Plasmolysis / flaccid
HYPERTONIC solution
Water leaves
Cell membrane pulled away from cell wal
Reduction in volume
