1/19: Cell Membrane, Membrane Transport, & Membrane Potential I Flashcards
What are the functions of the plasma membrane?
- Separate cytoplasm from ECF
- Regulate exchange between ECF and cytoplasm
- Communicate with other cells
- Provide structural attachments between cells or between cell and extracellular matrix
What is the plasma membrane described by?
The fluid mosaic model
What 4 different types of organic molecules make up the plasma membrane?
- Phospholipids
- Steroids
- Protiens
- Carbohydrates
What is the consistency of the plasma membrane at body temperature?
Thick oil
What kind of substances are phospholipids?
Amphipathic
What are phospholipids organized into?
A bilayer
Hydrophilic heads
Hydrophobic tails
What are the functions of phospholipids?
Creates a barrier
What substances are permeable?
Hydrophobic substances
What are examples of hydrophobic substances?
Small, nonpolar molecules
ex: Gases (O2, CO2), fatty acids, steroids
Lipophilic substances
ex: ethanol
Water
What substances are non-permeable substances?
Larger molecules
Polar molecules
Charged substances
ex: glucose, ions, amino acids, proteins
What are two functions of cholesterol?
- Help keep membrane fluid over a wide range of temperatures
- Help make membrane water tight
A proteins shape determines ________
Function
What are factors that alter protein shape?
- Mutations
- pH, temp, Osm
- Covalent/Allosteric modulation
What structures do mutations change?
1⁰ structure
What structures does pH, T, osm change?
Loss of 2⁰, 3⁰, and 4⁰ structure - denaturation (causes the structure to unfold)
What structures does covalent/allosteric modulation change?
2⁰, 3⁰, and 4⁰ structure and how cells regulate proteins
What are types of structural classifications?
Transmembrane proteins
Integral proteins
Peripheral proteins
What are receptor proteins?
Bind to specific chemical signals (ligands) and transmit that information to the cytoplasm
What are properties of receptor proteins?
- Specificity
- Saturation
- competition
What does specificity mean?
Shape of the binding site determines what will bind
Each type of protein will interact with only ______ type of substance or class of substances
one
ex: Insulin receptor only binds to insulin, enzyme maltase will only interact with substrate maltose, glucose transporter will only bind to and transport glucose
Within the solution of the body there are a ______ number of proteins and therefore a _____ number of binding sites
Set; set
What does saturation refer to?
The fraction of total binding sites that are occupied at any given time
What is saturation dependent on
Protein and the substance
What is transport rate proportional to?
Substrate concentration until the carriers are saturated
What is a competitive inhibitor?
A chemical substance (exogenous ligand) that binds to the active site of the protein and blocks the endogenous ligand from binding
When bound, what kind of effect to competitors have?
Do not produce an effect
What is the level of inhibition dependent on?
The concentration of the protein, endogenous ligand, and competitive inhibitor
What are examples of competitive inhibitors?
Penicillin
ACE inhibitors
Beta blockers
What do primary ligands do?
Activate the receptor resulting in a response
What do agonists do?
Activate the receptor resulting in a response
What do antagonists do?
Block receptor activity resulting in no response
Response of a cell to a chemical signal is mediated by what?
Receptor mediated NOT signal mediated
No receptor =
No response
Two different ligands binding to same receptor =
Same response
One ligand binding to two different receptors =
Two different responses
What is affinity directly proportional to?
- Number of ligands bound to receptors at any given [ligand]
- 1/Kd (Kd=[ligand] where 1/2 receptor occupied)
Which drug has a higher affinity for this receptor?
Drug 2
Because drug 1 requires more drug to get 1/2 the receptors occupied than drug 2 which means that drug 1 has a lower affinity
Which receptor would have the largest Kd value?
Protein 3
Because the higher the Kd value = the lower the affinity
The higher the Kd =
The lower the affinity
What is a transmembrane protein?
Span entire membrane all the way through
What is an integral protein?
Embedded in membrane, doesn’t go whole way through
What is a peripheral protein?
Outside of membrane
What is signal transduction?
Steps that occur from the time the ligand binds to receptor til you have a change in cell function
For saturation to occur, what does the saturation of transporters need to be like?
Constant
