Ions, Vitamins, Minerals Flashcards
Quantify the following units:
Molar (M) Milimolar (mM) Micromolar (uM) Nanomolar (nM) Picomolar (pM) Femtomolar (fM)
Mole (M) - one mole per litre
mM - 10^-3
uM - 10^-6
nM - 10^-9
pM - 10^-12
fM - 10^-15
Diffusion:
What is diffusion?
Diffusion occurs rapidly over what type of distances and slowly over what type of distances?
What do multicellular organisms evolve to bring individual cells within diffusion range?
What acts as a diffusion barrier?
What type of molecules diffuse easily? What type of molecules don’t?
Diffusion - process whereby atoms/molecules intermingle bc of their random thermal motion
Diffusion fast over microscopic distances
Diffusion slow over macroscopic distances
multicellular organisms evolve circulatory systems to bring individual cells within diffusion range
Cell membrane acts as diffusion barrier
Lipid soluble (non polar) molecules can diffuse more easily than water soluble (polar) molecules
How do molecules cross the epithelium to enter the bloodstream?
Paracellular transport- through tight junctions and lateral intercellular spaces
Transcellular transport - through the epithelial cells
Membrane transport:
Solutes can cross cell membranes by?
Types of transport proteins?
What type of transport protein transports solutes faster?
Solutes can cross cell membranes by:
- simple diffusion
- facilitated diffusion
- active transport
Two types of transport proteins:
Channel proteins - aqueous pores. Can have ion channels - specific to ions
Carrier proteins - binds to solute and undergoes conformational change to transport it across membrane. Can carry out uniport, symport or anti port
Transport much faster through channel protein than carrier proteins
Types of active transport?
What is facilitated transport/diffusion?
Active transport requires energy:
-Primary active transport - linked directly to cellular metabolism, uses ATP
-Secondary active transport - derives energy from conc grad of another substance that’s actively transported
Facilitated transport:
Enhances rate a substance can flow down its conc grad, doesn’t require energy
Examples of primary active transporters?
Examples of secondary active transporters?
Examples of facilitated diffusion?
Primary active transporters:
- Na+/K+ ATPase (pancreatic HCO3- secretion)
- H+/K+ ATPase (stomach - parietal cell)
Secondary active transporters:
- SGLT-1 co-transport (small bowel absorption of monosaccharides)
- HCO3-/Cl- counter transport (pancreatic HCO3- secretion)
- Na+/H+ counter transport (pancreatic HCO3- secretion)
Facilitated diffusion:
GLUT-5, GLUT-2 (small bowel absorption of monosaccharides)
Absorption of carbohydrates:
Via what type of transport are glucose and galactose absorbed?
Through what type of transporter protein?
When is this type of transport especially effective?
Absorption of glucose & galactose is by secondary active transport. Carrier protein = SGLT-1 on apical membrane
SGLT1 can transport glucose uphill against its conc grad (esp effective when glucose levels in the lumen are below those in the enterocyte)
How is fructose absorbed? Through what type of transporter protein if any?
What concs of fructose is this effective at?
Fructose is absorbed via facilitated diffusion
Carrier protein = GLUT-5 on apical membrane
Effective at relatively low concs of fructose in the lumen as tissue and plasma levels are low
How does glucose exit at the basolateral membrane?
Through what type of transporter protein if any?
Exit of glucose at the basolateral membrane is by facilitated diffusion
Carrier protein = GLUT-2, high capacity, low affinity facilitative transporter
Water & electrolytes:
What % of water presented to the GI tract is absorbed?
Absorption of water is powered by the absorption of what?
Where is the greatest amount of water absorbed?
How are many ions absorbed?
How are calcium and iron absorbed?
99% of the H2O presented to the GI tract is absorbed
Absorption of water is powered by the absorption of ions
Greatest amount of water is absorbed in the small intestine, esp the jejunum
Many ions slowly absorbed by passive diffusion
Calcium and iron are incompletely absorbed, this absorption is regulated
How much water is absorbed a day in the small bowel?
How much water a day is absorbed in the large bowel?
Water absorbed in small bowel : ~8L
Water absorbed in the large bowel: ~ 1.4L
Standing gradient osmosis:
Driven by what ion?
Transport of this ion becomes more efficient when?
Describe its transport at each of these locations:
- proximal bowel?
- jejunum?
- ileum?
- colon
Driven by Na+
-transport of Na+ from lumen into enterocyte-complex
Becomes more efficient as travel down intestine:
-counter transport in exchange for H+ (proximal bowel)
-Co-transport with amino acids, monosaccharides (jejunum)
-Co-transport with Cl- (ileum)
-restricted movement through ion channels (colon)
Absorption of other ions:
How is Cl- transported in:
-Ileum
-Colon
What type of transport is this?
How is K+ transported in small intestine and the colon?
What type of transport is this?
Cl- co-transported w Na+ (ileum), exchanged with HCO3- (colon) into enterocytes. - secondary active transport
K+ diffuses in via paracellular pathways in small intestine, leaks out between cells in colon
-passive transport
Standing gradient osmosis:
What happens to Intracellular sodium (in the enterocyte)?
Active transport of Na+ into the lateral intercellular spaces by Na+K+ATPase transport in the lateral plasma membrane
Standing gradient osmosis:
Why are Cl- and HCO3- transported into the intercellular spaces?
What causes the fluid in the intercellular spaces to be hypertonic?
Cl- and HCO3- transported into the intercellular spaces due to electrical potential created by the Na+ transport
High conc of ions in the intercellular spaces causes the fluid there to be hypertonic
