Flashcards in Cell Membranes and Transport Deck (24):
What the two functions of ORGANELLE membranes?
-isolate organelles from cytoplasm, allowing cellular processes to occur separately
-site of biochemical reactions
How does the plasma membrane appear under an electron microscope?
A double line 7-8nm wide
What three things are cell membranes mainly composed of? (Use PPC)
Cholesterol (animal cells)
How did Singer and Nicholson describe a cell membrane's structure in 1972 and why?
'Fluid mosaic model'
Proteins scattered like a mosaic throughout phospholipids and membrane components can move (fluid)
What are the main component of membranes?
What mass on average do proteins make up of a cell membrane?
What are the two surfaces of a membrane?
Extracellular (facing outside)
Cytosolic (facing inside)
What three proteins can be found in the membrane?
What are the 5 functions of CELL SURFACE membranes?
-allow take up of selected nutrients
-allows secretion of chemicals
-enables cell recognition
-allows cell to change shape
-keep cellular components inside cell
The point at which the protoplast is just about to pull away from the cell wall
Higher water potential in cell, water flows out down a water potential gradient
Water potential equal inside and outside the cell
Lower water potential inside the cell= water flowing in by osmosis down a water potential gradient
What does cholesterol do in membranes?
Maintain fluidity, increasing stabilty
Highest water potential (pure water)?
What is water potential measured in?
Conc of dissolved substances inside the cell. Always negative. "Measure of the reduction in water pot due to the presence of solute molecules."
Pressure exerted on the cell contents by the cell wall and cell membrane.
Red blood cells have a low water pot. In water, water flows in down water pot grad. No cell wall to stop cell expansion so continues until it bursts (haemolysis).
Red blood cells in hypertonic solution:-
Water will flow out, cells will be crinkled (crenated).
Secretory vesicles carry their contents to the cell surface membrane, merge with it and the secretion is released.
Two types of endocytosis:-
Phagocytosis and pinocytosis
Solid material taken into cell in a vesicle. Lysosomes fuse w/ vesicle and empty their enzymes into it. Enzymes digest material and producta are absorbed into cytoplasm.