Life At The Cellular Level - Water & pH Flashcards
What does hydrophilic mean?
Water loving, e.g will dissolve in water.
Polar molecules
Examples:
Sugars
Alcohols
Charged particles like ions
Compounds with n-h groups
Aldehydes
Ketones
Water forms a screen around charged particles when dissolved and around enzymes and substrates (favouring a reaction due to ordered water displacement)
What does hydrophobic mean?
Water hating molecules, won’t dissolve in water but will in lipid, non-polar molecules
Examples
Lipids
Fat soluble vitamins
Steroid hormones
Oxygen
In water, hydrophobic molecules arrange themselves to minimise exposure to water (the hydrophobic effect)
What is meant by amphipathic?
Molecules with both hydrophilic and hydrophobic parts.
Many proteins are amphipathic. The hydrophobic parts of the protein chain are located on the inside and hydrophilic parts located on the outside, allowing proteins to be soluble in water.
Examples
Heamoglobin
Cholesterol
Phospholipids (phosphate head is hydrophilic)
What are liposomes and micelles?
If you put many phospholipids into water you will get liposomes and micelles.
Liposomes - a bilayer of phospholipids with a hollow core. This core is filled with the ECF, polar
Micelles - a single layer of phospholipids with no core. This core is hydrophobic, non-polar.
Both are used to deliver drugs
How are lipids transported around the body?
Through the blood in chylomicron.
Chylomicrom is like a liposome but with proteins embedded in its shell and with lipids stored in its core. The hydrophilic head is essential for it to be able to be transported in the aqueous blood plasma.
What is pH?
The way of labelling the concentration of H+ ions in any aqueous solution.
Water tends to dissociate into H+ and OH- ions.
Water has a neutral pH of 7 because it has equal H+ and OH-
Acidic solutions have a greater H+ concentration and lower OH- conc (low pH)
Alkaline solutions have a lower H+ conc and higher OH- conc (high pH)
What is the normal blood pH range?
7.35-7.45
What are buffers?
Buffers are solutions that resist change in pH.
Weak acids and weak bases act as buffers. They partially dissociate.
Give 2 examples of buffers in the body
Cytoplasm of all cells- phosphate buffer system
Blood plasma- bicarbonate buffer system. The conc of bicarbonate depends on the conc of CO2.
Kidney changes the reabsorption of plasma bicarbonate. Lung, increase or decrease of ventilation will change the CO2 levels
