Biological Membranes - osmosis/active transport/endo- & exo- cytosis Flashcards
define water potential
measures the tendancy of water molecules to move across a membrane
what happens to water molecules and solutes on either side of a partial permeable membrane?
(talk about Concentration as well)
Low solute concentration | High solute concentration
higher no. of ‘free’ water molecules | lower no. of ‘free’ water molecules
high water potential | lower water potential
partially permeable
membrane
When a solute is in the solution the water molecules are attracted to the solute because they are polar. Now the water molecules are less freely to move and have a less of a tendancy to move across the membrane.
what is pure water? what happens to pure water when solutes are added?
Pure water (e.g. distilled water)
water molecules freely move and can move easily across the membrane.
highest water potential 0kpa (kilopascals)
what is osmosis?
the movement of water from a higher water potential to a lower water potential through a partially permeable membrane.
moves to from less negative water potential (closer to pure water) to more negative water potential (further away from water).
Different types of water potential in animal cells:
HYPOTONIC: high water potential on outside of the cell. Water will move inside the cell = cytolysis (cell burst)
ISOTONIC: same water potential in and outside of the cell. No net movement of water
HYPERTONIC: low water potential on outside of the cell. Water will move outide = cell becomes crenated (shrivels)
Different types of water potential in plant cells:
HYPOTONIC: high water potential. Water moves inside = cell becomes turgid, the cytoplasm and cell membrane pushes against the cell wall
ISOTONIC: same water potential inside and outide of the cell. No net movement of water
HYPERTONIC: Low water potential outside. Water moves outside = cell becomes plasmalysed, cytoplasm and cell membrane move away from the cell wall
What is ATP? What is it made of?
Adeosine tri phosphate
Made of a pentose sugar (oxygenated ribose sugar). Attached to the sugar is a adenine base also a phosphate chain (made of 3 phosphates with a anhydride bond between the 2nd & 3rd phosphate)
The anhydride bond can be broken to release energy and broken into ADP
What 3 things require ATP as an immediate source of energy?
active transport
endocytosis
exocytosis
define active transport
the movement of molecules or ions from a low concentration to a high concentration using ATP.
how does active transport use carrier proteins?
It has ATP on the outside of the carrier protein (in a membrane) and is broken down into ADP+Pi (forms ADP and phosphate).
The energy released (from the ATP being broken down) changes shape of the carrier protein, causing the molecules/ion to enter the cell
What is Bulk transport? What are the 2 types of Bulk Transport?
Used to move larger materials in or out of the cell (e.g. proteins, part of the cell, whole cells)
Bulk transport requires energy to move the vesicles to/from the membrane.
2 types of bulk transport:
Exocytosis (out of cell)
Type of exocytosis:
-protein secretion
Endocytosis (into the cell)
Types of endocytosis:
-pinocytosis (extracellular fluid, liquids/dissolve in water)
-phagocytosis (solid matter)
explain endocytosis
both phagocytosis and pinocytosis
Phagocytosis:
the solid particle moves towards the plasma membrane of a cell, then the membrane moves around the solid particle (pseudopodium). As it full creates encloses the particle and breaks off, it creates a phagosome (food vacuole).
Pinocytosis:
The plasma membrane of a cell engulfs extracellular fluid into a vesicle into the cell
explain exocytosis
A vesicle full of proteins inside a cell moves towards the the cell membrane. The membrane of the vesicle starts to bind to the membrane of the cell, which means it opens the vesicle to the extracellular environment (outside of the cell)
