2.4 ( Cell Membranes & Transport) Flashcards
(15 cards)
What is a cholesterol? and the function of it?
- A type of lipids
- Regulates fluidity of membrane
- Embedded within phospholipid
- Preventing them from packing too close together when temp are low
- This prevents from freezing and fracturing
What is the result of the interaction between cholesterol and tails of phospholids ?
- They bind to the tails, stabilising them
- Causing phospholipid to pack more closely together
What does cholesterol contribute to other than fluidity?
- Contributes to impermeability of membrane to ions
- Increases mechanical strength
- Increases stability of membranes
What does glycolipids and glycoprotein contain?
- Contain carbohydrate chains that exist on the surface
- Enables them to act as receptor molecules
What are the three main receptor types?
- signalling receptor for hormones and neurotransmitters
- receptors involved in endocytosis
- receptors involved in cell adhesion and stabilisation
- as the carbohydrate chains can form H bonds with water molecules
Membrane become less fluid when there is?
- An increased proportion of saturated fatty acids
- The chains pack together tightly
- Therefore high number of IMF between chains
- Lower temperature
- Molecules have less energy
- Therefore not moving as freely
- Causes structure to be more closely packed
Membranes become more fluid when there is?
- An increased proportion of unsaturated fatty acids chains
- because these chains are bent
- which means chains are less tightly packed together
- less IMF
- Higher temperature
- Molecules have more energy
- Therefore move more freely
What is water potential?
- Tendency of water to move out of a solution
- A dilute solution has a high water potential
- A concentrated solution has a low water potential
Effect of hypertonic solution to RBC?
- red blood cells have higher water potential than solution
- net movement of water out
- cell shrinks and shrivelled
Effect of isotonic solution on RBC?
- water potential equal between RBC and solution
- no net movement of water
- normal cell
Effect of hypotonic solution to RBC?
- RBC have lower water potential than solution
- Net movement of water in
- Cell swell, may lyse (burst)
Why can’t animal cell be plasmolysed?
- Animal cell doesn’t have cell wall
- Only plant cell can be plasmolysed
Comparison of plant cells and animals cells with solution of different water potential v1
Similarity:
- Presence of cell membrane composed of a phospholipid bilayer, and is partially permeable
- Osmosis of water into and out of cell can occur
DIfference
1. Animal cell lacks cell wall, while plant cells has cell wall that is fully permeable
Comparison of plant cells and animals cells with solution of lower water potential (less negative)
Cell placed in solution with lower water potential:
- plant cells
- water leaves cell through partially permeable cell surface membrane by osmosis
- volume of cell decreases
- protoplast shrinks/ pulls away from cell
- cell is plasmolysed
- animal cells
- water leaves cell through partially permeable cell surface membrane by osmosis
- volume of cell decreases
- cell shrinks/ shrivels up
Comparison of plant cells and animals cells with solution of higher water potential (more negative)
- plant cells
- water enters cell through partially permeable cell surface membrane by osmosis
- volume of cell increases
- protoplast expands/ pushes against cell wall
- cell wall withstands increased in pressure that is created
- pressure continues increases until cell is rigid and firm (turgid)
- animal cells
- water enters cell through partially permeable cell surface membrane by osmosis
- volume of cell increases
- no cell wall to withstand increased in pressure created
- cell membrane eventually stretched too far and cell bursts
