CELL SURFACE MEMBRANE AND TRANSPORT Flashcards
What does the fluidity of the cell surface membrane depend on?’
Length of the fatty acid tail (shorter)
Unsaturated is more fluid
What is the functions of the phospholipid bilayer?
Allow lipid soluble substances to enter and leave the cell and prevent water soluble substances making the cell surface membrane partially permeable
Maintains the fluidity of the membrane
Functions of glycolipids
Act as recognition sites
Help maintain the stability
Cell adhesion
Functions of cholesterol
Reduces lateral movement of phospholipids maintaining fluidity
Regulates fluidity depending on temperature
Prevent passage of dissolved polar ions and molecules
Channel proteins
Water filled pores
Allow selected hydrophilic ions and molecules to pass. Specific.
Are used in facilitated diffusion
Carrier Proteins
Change shape allowing for the passage of specific ions or molecules
Can carry both facilitated diffusion and active transport
Functions of the glycoproteins
Act as cell surface receptors for hormones and neurotransmitters
Help in cell adhesion
Act as cell recognition sites
Functions of the glycoproteins
Act as cell surface receptors for hormones and neurotransmitters
Help in cell adhesion
Act as cell recognition sites
Functions of cell surface membrane within the cell
Control the entry and exit of materials in organelles such as mitochondria and chloroplast
Provide and internal transport system-ER
Isolate enzymes that may damage cells - lysosomes’
Provide surfaces on which processes can occur- protien synthesis using ribosomes on RER
Three main stages of cell signaling
Secretion of ligand
Transport of ligand to target cell
Binding of ligand to cell surface receptors on target cells
What is a ligand
Biological molecule which binds specifically to another molecule
Diffusion
Net movement of particles from a region of a higher concentration to a region of a lower concentration down a concentration gradient.
It is a passive process- uses KE of particles rather than ATP from respiration
Factors Affecting Rate of Diffusion
Steepness of concentration gradient
Temperature
Surface area: volume ratio
Explain facilitated diffusion
There are certain substances - large polar molecules e.g Glucose and amino acids and ions such as Na+ and Cl- cannot pass the CSF
Carrier and channel proteins are used
Channel protiens are water filled pores, spefic, gated- move to open and close the pore allowing control of passage of ions
Carrier proteins - change shape.
When a particular molecule specific to the protein is present it binds at a specific binding point causing it to change shape in such a way that the molecule is released inside the membrane
