Membrane structure and function Flashcards
What are the general functions of biological membranes?
-Compartmentalization
-Scaffold for biochemical activites
-Selective permable barrier
-Transport solutes
-Response to external stimuli
-Cell to cell communication
-Energy transduction
-Cell growth/mobility
-All are influenced by membrane structure/chemistry
What is the plasma membrane?
-Outer boundary of cell, separates cell from environment
-Thin, fragile, about 5-10 nm thick
-Electron microscope to visualize
-Same membrane ultrastsructure for plants, animals and microorganisms
-DYNAMIC phospholipid bilayer
-Composed of Lipids, proteins and carbohydrates
-Cell cortex or membrane skeleton reinforces plasma membrane
What are the types of membrane lipids?
-Phosphoglycerides
-Sphingolipids
-Cholesterol
Describe phosphoglycerides
Phospholipid
-Fatty acids + phosphate group
-Joined by alcohol residue
Phosphoglyceride
-Type of phospholipid
-Alcohol residue = glycerol
Fatty acids may be
-Fully saturated (no C=C)
-Monosaturated (one C=C)
-Polyunsaturated (multiple C=C)
Describe sphingolipids
Built with sphingosine (instead of glycerol)
-Amino alcohol with a long hydrocarbon chain
Ceramide:
-Structural unit of all sphingolipids
-Fatty acid residue
Sphingomyelin:
-Myelin sheath nerve cell axons
-Phosphocoline group
Cerebroside (single sugar) and Ganglioside (oligosaccharide):
-Glycolipids (CHO attached)
Describe cholesterol
-Sterol
-Carbon rings are flat and rigid
-Smaller and less amphipathic compared to other membrane lipids
-Comprises up to 50% of lipids and animal membranes
-Insertion of cholesterol into plasma membrane provides structural integrity and membrane fluidity
Describe the asymmetric distribution of phospholipids
Explain membrane assembly in the endoplasmic reticulum
What is the function of liposomes?
Describe membrane carbohydrates
What are glycolipids?
What are glycoproteins?
What are the protein classes?
about 30% of the proteins encoded in an animal’s genome are membrane proteins
-Integral
-Peripheral
-Lipid-anchored
What are integral proteins?
What are peripheral proteins?
What are lipid-anchored proteins?
Describe the membrane structure of human red blood cells
What are the factors that influence membrane fluidity
-Temperature
-Cholesterol
-Saturaed and unsaturated fatty acids
What is desaturation?
Describe the dynamic nature of the plasma membrane
Moving from one leaflet to another is rare and energetically unfavourable
Explain cell fusion and mobility of membrane proteins
Explain membrane lipid mobility
-Proteins do not just freely flow around in lipid “sea’
-Membrane domains have functionally specialized regions
Describe membrane domains and polarity of epithelial cells
Describe membrane domains and polarity of mammalian sperm cells
