Physiology Flashcards
What do membranes do?
Control exit and entry of waste products, they are selectively permeable.
-Maintain ion concentration gradients and participate in the joining of cells
What is the plasma membrane?
- Phospholipid bilayer
- Cholesterol
- Proteins
- Carbohydrates
What does cholesterol add to plasma membrane?
Fluidity and stability
-Stiffens the membrane
3 types of proteins in plasma membrane?
Integral
Transmembrane
Peripheral
Where are integral proteins in membrane?
Embedded in bilayer
-Receptors
What are names of transmembrane proteins and where are they?
Transporters/channels
-Extend through membrane
What is different about peripheral proteins compared to transmembrane and integral?
They do not penetrate the membrane
What makes up the glycocalyx?
Glycoproteins
Glycolipids
Functions of lipid bilayer?
Basic structure of membrane
Hydrophobic interior serves as a barrier
Responsible for fluidity
Function of carrier/transport proteins?
Span the membrane and are substrate specific
Where are docking marker acceptors?
Inner membrane surface
How do docking membrane acceptors work?
Interact with secretory vesicles leading to exocytosis of vesicle contents
How do receptor proteins work?
Bind specific molecules - lock & key
Types of cell adhesion molecules (proteins)?
Cadherins
Integrins
What do cadherins do? And what are they?
Hold cells within tissues together
Cell adhesion molecules
What do integrins do?
Span membrane acting as a link between extra and intra-cellular environments
2 Functions of carbohydrates?
- Serve as self identity markers enabling cells to identify and interact with one another (different cell types have different markers)
- Role in tissue growth
3 types of specialized cell junctions?
Gap junctions
Tight Junctions
Desmosomes
Desmosomes?
Adhering junctions that anchor cells together
Tight junctions?
Join lateral edges of epithelial cells near luminal/apical membrane
Gap junctions?
Communicating junctions that allow movement of charge carrying ions and small molecules between 2 adjacent cells
What does Fick’s law of diffusion relate to?
- Magnitude of conc gradient
- SA of the membrane diffusion is taking place across
- Lipid solubility of substance
- Molecular weight of substance
- Distance which diffusion must take place across
What is an electrochemical gradient?
Where an electrical and a concentration (chemical) gradient may be acting on a particular ion at the same time
Osmosis?
Net diffusion of water down a concentration gradient
What are water channels called?
Aquaporins
Osmolarity?
Concentration of osmotically active particles in a solution
What is osmolarity measured in?
Osmoles/Litre
Osmolarity of body fluids?
~300mOsm
Tonicity?
Effect a solution has on cell volume
Units of tonicity?
NO UNITS
What is carrier-mediated transport?
Substance binds to specific carrier and undergoes transformational change to transport substance
What is saturation another term for?
Transport maximum (Tm)
Fact file of facilitated diffusion?
- Energy?
- Mediated?
- Gradient direction
No energy required
- Carrier mediated
- From high to low conc
Active transport fact file?
Energy?
Gradient?
Types?
-Energy required
-Low concentration to high concentration
-Primary= energy directly required
Secondary= Energy required but not used directly
Secondary active transport energy?
- Energy required but not used directly
- It is stored in the form of an ion concentration gradient (usually Na+)
Mechanisms of secondary active transport?
2 mechanisms
- Symport- contransport= solute and Na+ move in the same direction
- Antiport - exchange/countertransport = Solute and Na+ move in opposite directions
What is K+/Na+ATPase used in? Where is it?
Primary active transport
Plasma membrane of all cells
Ratio of NA:K movement in primary AT?
3 Na out
2 K in
3 important roles of Na+/K+ATPase?
- Establish Na/K concentration gradients across plasma membrane
- Regulate cell volume by controlling concentration of solutes inside the cell
- Energy used to drive the pump indirectly serves as energy source for secondary AT
Types of vesicular transport?
Endocytosis
Exocytosis
Endocytosis?
Membrane pinches off to engulf substance
Exocytosis?
Vesicle fuses with membrane, releasing contents to ECF
What is Em? Units?
Membrane potential - separation of opposite charges across membrane
-mV
Concentration gradient direction for K+?
Outward
Concentration gradient for Na+?
Inward
Electrical gradient for K+/Na+?
Both positively charged so the EG for both will be towards the negatively charged side of the membrane
Equilibrium potential for K+?
When concentration and electrical gradients balance eachother
Membrane potential at Ek?
-90mV