Chapter 4 Flashcards
Define: Plasma membrane
Outer boundary of the cell that separates it from the world is a thin, fragile structure
Estimated thickness of plasma membrane
5-10 nm
Do all membranes have the same ultrastructure?
Yes
How can you observe the plasma membrane?
An electron microscope
What are the 7 functions of the plasma membrane?
- Compartmentalization
- Scaffold for biochemical activities
- Selectively permeable membrane
- Transport solutes
- Response to external stimuli
- Cell-cell communication
- Energy transduction
What is the plasma membrane made of?
Lipids and proteins
Define: Amphipathic
Property of a molecule having both hydrophobic and hydrophilic regions
What is insulation for a nerve cell?
Myelin sheath
Define: Phosphoglycerides
Lipids with phosphate group
Define: Phosphoglycerides
Phospholipids built on glycerol backbone
Define: Sphingolipids
Derivative of sphingosine
Define: Sphingosine
An amino alcohol that contains a long hydrocarbon chain
Define: Ceramides
Basic structural units of all sphingolipids, consists of sphingosine linked to fatty acid by amino group
Define: Cholesterol
Smaller and less amphipathic molecule
What sterol makes up to 50% of animal membrane lipids
Cholesterol
Can lipid bilayers self-assemble?
Yes
Liposome functions in the bilayer
- deliver drugs within the body
- membrane proteins inserted into liposomes
What are membrane carbohydrates?
Plasma membrane of eukaryotic cells have carbohydrate, glycoproteins and glycolipids
What is the function of membrane carbohydrates?
Mediates interactions of cell and the environment
What is an example of an important carbohydrate in plasma membrane?
Blood type
What determines blood type?
Glycolipid carbohydrates of RBC plasma membrane
Blood type A
Adds enzyme V-acetylgalactosamine to end chain
Blood type B
Adds enzyme galactose to chain terminus
Blood type AB
Both enzymes present
Blood type O
Lacks enzyme capable of attaching either terminal sugar
What is integral membrane protein function?
Receptors that bind ligands, channels, or transporters to move ions/solutes across membrane
Are integral membrane proteins amphipathic?
Yes
What are peripheral membrane proteins?
Associate with membrane by weak electrostatic bonds
What are lipid anchored membrane proteins
Covalently bonded to a lipid group that resides within membrane
What are lipid rafts?
Outer leaflet of plasma membrane contains specialized regions
What is the function of lipid rafts?
Provide favourable environment for cell-surface receptors
Phospholipids move in what way?
Laterally
Define: Flippases
Enzymes that move certain phospholipids from one leaflet to the other
Define: Apical plasma membrane
Absorbs substances from lumen
Define: Lateral
Cell contact
Define: Basal
Substratum contact, ion gradient
Cell with the most highly differentiated structure, covered in continuous plasma membrane
Sperm cells
What is Brownian movement
Phospholipids can find for brief periods to certain areas
What can detect and demonstrate distribution of different proteins?
Antibodies
What is spectrin?
Has alpha and beta subunit, wound around each other and head to tail orientation. Major component of internal membranes skeleton
What is ankyrin?
Mediate interaction with interval membrane proteins
Where is Actin found?
Present in microfilaments
What is glycophorin A?
Transmembrane dimer, each subunit single pass protein, heavily glycosylated
What does G3PD stand for?
Glyceraldehyde – three – phosphate dehydrogenase
Four basic mechanisms which solute moves across membranes:
- Passive
- Active
- Nonmediated
- Transporter mediated
How do you calculate net flux?
Difference between influx in efflux 
Define: Osmosis
Diffusion of water through semi permeable membrane
Cells (shrink, swell, stay same) in a hypotonic solution?
Swell
Cells (shrink, swell, stay same) in a hypertonic solution?
Shrink
Cells (shrink, swell, stay same) in a isotonic solution?
Stay same 
Are ions permeable or impermeable to membranes
Impermeable
Three ways ion channels can exist
Open, closed, or gated
Three major categories of gated channels:
- Voltage gated channels
- Ligand gated channels
- Mecano gated channels
Voltage gated channels confirmational state depends on what?
Difference in ionic charge on the two membrane sides
Ligand gated channels confirmational state depends on what?
Binding of specific molecules
Mecano gated channels confirmational state depends on what?
Mechanical forces applied to membrane
Gradients are generated by what?
Active transport
Define: Facilitated diffusion
Process by which the diffusion rate of a substance is increased through interaction with a substance specific membrane protein
What molecules is facilitated diffusion used for?
Sugars and amino acids
Facilitated diffusion transport involves what done to the molecule?
Confirmational changes
Can facilitated transporters mediate movement of solutes in both directions?
Yes
What is a facilitative transporter?
Transmembrane proteins that bind to specific substance and changes its confirmation so as to facilitate diffusion of the substance down its concentration gradient
Define: Active transport
Energy requiring process, a substance binds to a specific transmembrane protein which changes its confirmation to allow passage of the substance through the membrane against the electrochemical gradient
What is an active site?
Part of an enzyme molecule that is directly involved in binding the substrate
What is an example of primary active transport in humans?
NA/K ATPase, Sodium potassium ATPase
What does NA/K ATPase do?
Pumps potassium in, sodium out
What is the ratio of sodium: potassium pumped?
3:2
What type of pump is ATPase?
P type pump 
Describe a P – type pump
Phosphorylation causes changes in confirmation an ion affinity that allowed transport against gradients
What is an E1 conformation?
Ion binding sites are accessible to inside of the cell
What is an E2 conformation?
Ion binding sites accessible to outside of the cell
What is a V type pump?
Actively transport H across walls of cytoplasmic organelles
What are ABC transporters?
ATP binding cassette
What is co-transport?
Coupling transport to existing ion gradients 
What drives cotransport of glucose?
Diffusion of sodium ions down concentration gradient
What is the secondary active transport of glucose?
Symport
Define: Neurons
Specialized cells for information transmission using changes in membrane potentials
Define: Dendrites
Receive incoming information, cell body contains nucleus and metabolic centre of cell
Define: Axon
Long extension for conducting outgoing impulses
Define: Resting potential
Membrane potential of nerve or muscle cell subject to changes when activated
Define: Depolarization
When cells stimulated, sodium channels open
Define: Action potential
When cells stimulated, voltage gated sodium channels open
Excitable membranes exhibit what type of behavior?
All or none
Where are action potential is generated?
Nodes of Ranvier
What does the speed of neural impulse depend on?
Axon diameter and weather axon is myelinated
Define: Postsynaptic cell
A cell that receives neurotransmitters from another cell across a synapse
Define: Synapse
Specialized junction of a neuron with its target cell
Define: Presynaptic cell
A cell that sends neurotransmitters to another cell across the synapse
Define: Synaptic cleft
Narrow gap between two excitable cells