Introduction to Physiology: Homeostasis and Cell Structure and Function Flashcards
What is physiology
A foundational sciences for the understanding and practice of medicine.
- The study of the function the body at the molecular, cellular, organ system and organismal levels.
- The study of how everything maintains homeostasis
Homeostasis
The maintenance of steady state in the internal environment despite changes in the external environment
Or maintenance of constant internal environment (Clause Bernard’s Milieu Interieur) despite changes in the external environment
Extracellular Fluid (ECF)
ECF of multi cellular organisms mimic primordial environment and buffers cell from external environment
Before we had multicullular organisms with “internal environments”, there were…
unicellular organisms
Multicellular organisms have ____ interaction with the outside environment, and require ways to communicate between cells
Less direct
Proteins comprise ___% of the membrane by mass
50%
Integral/Intrinsic/transmembrane Proteins
Ion channels, transport proteins- span the entire cell membrane or are embedded in the membrane
Peripheral/Extrinsic Proteins
Are not embedded and are located on one side of the cell membrane either intra- or extracellular side.
Can water soluble substances dissolve in lipid bilayer?
NO- but some can cross the cell membrane through water-filled channels/pores or may be transported by carrier proteins
Examples of water soluble substances that cannot dissolve in lipid bilayer
Na+, Cl-, Glucose, H2O
How can cell membrane proteins act as?
transporters, channels, receptors, enzymes, antigens
5 types of membrane transports
- simple diffusion
- facillitated diffusion
- primary active transport
- secondary active transport
- osmosis
What does the rate of diffusion depend on in simple diffusion?
- Concentration gradient
- Permeability of the membrane
- Surface area
In simple diffusion, ___ is directly proportional to the ___
Rate of diffusion, concentration difference
In facilitated diffusion, why is rate of diffusion faster?
Due to the presence of the carrier protein at lower conc.
Facilitated diffusion follows all features of a carrier mediated transport- which are…
Saturation, Specificity, Competition
Facilitated Diffusion rate of diffusion…
reaches saturation at high concentration
3 features of ALL forms of carrier-mediated transport
- Chemical specificity/stereospecificity
- Competition
- Saturation
Carrier-mediated transport proteins have a limited number of ___ for the solute
binding sites
At high solute concentrations, rate of transport reaches a ___, as all the binding sites are saturated (occupied)
Plateau
Transport Maximum (Tm) definition
The maximum rate at which the substance can be reabsorbed
Primary active transport
Transport of solutes against the concentration gradient- requiring use of energy (ATP) to pump solutes DIRECTLY-ATPASE activity
Primary active transport follows all features of a carrier mediated transport, which are…
Saturation, Specificity, Competition
Secondary Active Transport
Transport in which transport of a solute is coupled with sodium transport and is transported against its gradient
- Active, carrier mediated process
- Energy is used INDIRECTLY by the carrier
- Driving force is the sodium concentration gradient, created by primary active transport
What makes secondary active transport stop?
If there is no sodium gradient
-Inhibiting Na+K+ pump
Uniport
Transport of a single susbstance
Symport
Transport of more than one substance in the same direction (AKA Cotransport)
Antiport
Transport of more than one substance in opposite directions (AKA countertransport or exchange)
Symporter
Involves more than one type of particle being transported by in the SAME direction at the same time by the same mechanism
Counter transport/Antiport/Exchange
When solutes move in opposite directions across the cell membrane
Osmosis
Movement of water across the cell membrane OR selectively permeable membrane due to DIFFERENCE IN CONCENTRATION OF SOLUTES
The water concentration of a solution is determined by the….
Concentration of solute
Difference between Osmosis and Diffusion
Osmosis occurs because of a pressure difference
Diffusion occurs because of a concentration difference
