Chapter 5 ~ Plasma Membrane Flashcards
What is the role of cell membranes?
It provides a partially permeable membrane
Cell communication/cell signalling
Site of chemical reaction
What is a cell membrane formed of?
Describe the formation of answer to q1?
It is formed of a phospholipid bilayer
It contains hydrophilic phosphate heads on the outside and hydrophobic fatty acid tails on the inside
Describe the fluid mosaic model
The phospholipids are free to move within the layers and proteins are embedded within the bilayer which vary in size and shape
What are the two types of proteins?
Intrinsic and extrinsic
Describe extrinsic proteins include 2 examples.
Extrinsic proteins are present on one side of the bile layer. They contain hydrophilic groups on the outer surface which interact with polar heads of phospholipids/intrinsic proteins. They provide mechanical support.
Glycolipids and glycoproteins are examples which are used in cell recognition/cell signalling
Describe intrinsic proteins
Present in both layers.
There are carrier proteins which have tubes filled with water which enables water soluble ions to diffuse
There are proteins which bind with other ions and large molecules and change shape to transport them
Describe the function of cholesterol
It is to regulate fluidity
What factors affect membrane structure?
Temperature and solvent
Describe how high temperature affects membrane structure
High temperature increases the kinetic energy of the phospholipid which causes them to move more. This increases fluidity and increases permeability which causes the structure to begin to break. This makes it easier for particles to cross.
Describe how solvent affect membrane permeability
Organic solvent, for example, alcohol dissolve within the phospholipid bile layer which causes fluidity to increase, which makes it more permeable
What is simple diffusion?
When particles move from the area of high concentration to an area of low concentration down the concentration gradient
Must be lipid, soluble and small 
What is facilitated diffusion?
This is diffusion across a membrane through protein channels and carrier proteins
What is active transport?
This is the movement of molecules/ions into and out of cells from a lower concentration to a higher concentration against the concentration gradient. This uses energy in the form ATP and carrier proteins..
It is a selective process as only certain molecules combine into the receptor site
Explain the process of active transport
1.active transport by protein
2.it is hydrolyse into ADP and PI
3. this causes protein to change, shape and open inwards inside of the membrane
4. This causes molecules to be released on other side of the membrane.
5. PI molecules release, which results in protein reverting into original shape
What type of transport is endocytosis
How many types of endocytosis is there?
Endocytosis is a type of both transport into the cell.
There is phagocytosis, which occurs with solids and pinocytosis, which occurs with liquids
