Chapter 6 Interactions Between Cells And The Extracellular Environment Flashcards
What are selectively permeable membranes?
Just certain substances can go through
What is carrier mediated transport?
Facilitated diffusion
Active transport through a membrane = requires ATP and can be primary and secondary
What is non-carrier mediated transport
Diffusion (passive transport)
Osmosis
Diffusion
Movement of solute along its concentration gradient (for simple and facilitated diffusion) - from regions of higher concentration to region of lower concentration
Simple diffusion
Movement of molecules from one location to another
Facilitated diffusion
Carrier-mediated
Is assisted by another molecule
What affects the rate of diffusion?
- Concentration difference
- Membrane permeability
- Temperature
- Mass of the solute molecule
- Surface area of the membrane
- Medium through which solute must pass
- Distance
Diffusion through the bilayer
Right through the membrane
Non-polar substances diffuse easily
Small polar molecules can diffuse easily
Net diffusion
Movement in both direction but the net diffusion follows the concentration gradient until the gradient no longer exist = equalibrium
Diffusion through channels
Channels are proteins
Channels selectively allow certain substances to pass
Can be open or gated
Electrochemical gradient must exist
Why do substance move in and out of cells
In order to maintain homeostasis and perform physiological functions
What process is the diffusion of water
Osmosis
What are aquaporins
Channel proteins that allow water to pass through
Osmotic pressure
Pressure require to prevent the flow of water - region with higher solute concentration
Total body water percentages
67% ICF
33% ECF:
20% blood plasma
80% ISF
What makes a solution
Solvent + solute
What is toncity
The effect of a solution on osmotic movement of water
isotonic
equal osmotic pressure inside and outside the cell
hypertonic
higher osmotic pressure in the external solution
Hypotonic
lower osmotic pressure in the external solution
different types of carrier-mediated transport
faciliated diffusion active transport endothelial transport endocytosis exocytosis
What is Faciliated diffusion
diffusion along the concentration gradient; assisted by another molecule
passive transport - doesn´t require ATP
What is active transport and what types
- Transport of solute against its concentration gradient 2. Requires ATP
Primary transport - in membrane integrated pump
Secondary transport - Ion concentration gradient is used as the energy source to move a second solute;
Sodium Potassium pump
3 Na+ out and 2 K+ in = inside of cell more negative
What is epithelial transport and what pathways are there
Transport of substances across epithelial cells
Pathways:
- Praracellular pathway - substance moves between adjacent (german angrenzend) cells of epithelium
- Transcellular pathway - substance moves in through apical or basolateral membrane, through cytoplasm and exits through opposite membrane
endocytosis
membrane forms vesicle, including small amount of ECF - brings that fluid + extracellular substances into the cell
exocytosis
membrane vesicle joins membrane and releases cellular products into ECF
membrane potential
difference in charge across the cell membrane - cause by different factors
What is the concentration of Potassium and Sodium
Na+ 12mM inside the cell, 145 mM outside the cell
K+ 150 mM inside the cell, 5 mM outside the cell
What equation is used to work out membrane potential
by Nernest Equation => Eion = 61/Z log(Cout/Cin)
Z: valence of the ion (available electrons)
Cout: extracellular concentration of ion
Cin: intracellular concentration of ion
What is a resting membrane potential
membrane potential of a cell not producing electrical impulses - determined by relative concentrations of ions inside and outside the cell
What is cell signalling and what 4 ways can signals travel
chemical communication in between cells
4 different transport ways of signal:
1. Paracrine signal - signal to nearby cell
2. Endocrine signal - related to hormones, travel through bloodstream to distant target
3. Synaptic signal - neurons release neurotransmitter to regulate usually nearby target cells
4. Diffusion
signal receptors in the cell membrane
for hydrophilic signals - require second messenger - another substance that enters cytoplasm with signal
signal receptors in the cytoplasm or nucleus
for hydrophobic (non-polar) signals
What is the difference between anions and cations
Anions - negatively charged
Cations - positively charged
What is potassiums equilibrium potential
-90 mV
