Cell Membranes And Their Transport Systems Flashcards
(29 cards)
What are membranes
-selectively permeable barriers
-maintain constant internal environment and enclose cell contents
-very thin
What are phospholipids
-has a dynamic structure so components are free to move around
*amphipillic: both hydrophilic and hydrophobic parts
*polar head: negatively charged phosphate group
*non polar tail: no charge
*phospholipid: “self-assembles” to create the bilayer. They migrate but rarely flip
Two types of tails
Saturated and Unsaturated
Saturated: single bonds only
Unsaturated: at least one double bond
Double bond creates a kink in the fatty acid chain of the tail
What do higher concentrations of saturated fatty acids cause?
Reduces cell membrane fluidity
What do higher concentrations of unsaturated fatty acids cause?
Promote membrane fluidity
What do concentrations of unsaturated phospholipids affect?
It affects membrane fluidity
2 types of carbohydrates
Glycolipids and glycoproteins
3 roles of carbohydrates
Maintain membrane stability, cell protection and aids in cell adhesion
What is a lipid
Has polar and non polar regions, wedges itself between phosplipid tails and can migrate and flip between membrane layers
Proteins function
Serve as enzymes, carrier proteins, channel proteins, receptors, cell adhesion and recognition
Two types of proteins
Integral proteins- firmly inserted into the brain
Peripheral-loosely attached to the membrane
Membrane fluidity is affected by
Extreme temps- hot (More kinetic energy, phospholipids move further away and membranes have more fluid )
Cold (Less kinetic energy, phospholipids pack together and membranes have less fluid )
Concentration of unsaturated fatty acids
Cholesterol levels - it maintains fluidity by preventing lipids from getting too close together or too far apart from each other
Red blood cells quantity
Equal amounts of lipid and protein
Small amounts of carbohydrates
Nerve cells quantity
Higher amounts of lipid in the cell membrane
Passive transport
moves down a concentration gradient
Three types: simple diffusion, facilitated diffusion and osmosis
-uses inherent kinetic energy
Active transport
-moves against a concentration gradient
-has directionality
-requires a specific carrier protein
Two types: primary and secondary
-needs external energy source
Simple diffusion
small, uncharged non polar molecules
Properties:
-no metabolic energy is required
-uses kinetic energy
-the rate of diffusion is proportional to the concentration gradient
Facilitated diffusion
uses specific proteins
-the rate of diffusion is proportional to the concentration gradient
Simple diffusion and facilitated diffusion kinetics:
Simple diffusion= linear relationship between concentration and rate of diffusion
Facilitated diffusion= the rate of diffusion reaches a plateau since the proteins become fully occupied
Osmosis
net movement of water down a concentration gradient
Primary active transport:
movement of Na+ and K+ uses the Na+/K+/ATPase pump
-maintains ion concentration differences inside the cell
-hydrolysis of ATP results in= phosphorylation of the pump —> results in conformational change of pump
-causes transport of 3Na+ out and 2K+ into the cell
Secondary active transport (co-transport):
*A substance against its concentration gradient—> active transport
*Ion movement down its concentration gradient—> usually facilitated diffusion
-energy used for secondary active transport comes from the electrochemical gradient across the membrane.
What are the two types of secondary active transports?
Symport;
*transported substances move in the same direction
-Antiport;
*Transported substances move in the opposite direction
What is endocytosis?
Moves large molecules into the cell
Three types: phagocytosis, pinocytosis and receptor- mediated
