Medical Biochemistry Chapter 2 Flashcards
life evocvled in what
water
organism typically contain
70tom 90%
Water is the perfect way, and what types of reactions occurs in aqueous solutions
solvent and chemical
Water has a what heat capacity
high
Water acts as a heat buffer to maintain internal temperatures
True
Is water more dense than ice?
yes
Water is a critical determinant of what?
structure and function of proteins, nucleic acids, and membranes
Water has a how many electron pairs and what geometrical shape does it have?
4 and tetrahedral
What does the elctronegavity of the oxygen have on water?
water serves as hydrogen bound donor and acceptor
Hexagonal ice forms a what lattice
regular
What is the entropy of hexagonal ice?
low
Why is ice more dense than water?
contains more hydrogen bond per water molecule
Ice doesn’t absorbs heat when melting which allows the delta S to be lesser?
False; Ice does absorbs heat when melting which allows the delta S to be greater
Water is a good solvent for
polar and charge molecules such as amino acids, peptides, alcohols, carbohydrates, nucleic acids
Water is a good solvent for
polar and charge molecules such as amino acids, peptides, alcohols, carbohydrates, nucleic acids
Water is a poor solvent for
non polar molecules such as non polar gases, aromatic rings, aliphatic chains, and lipids
Water is a poor solvent for
non polar molecules such as non polar gases, aromatic rings, aliphatic chains, and lipids
The high dielectric constant of water (ability to screen charges)
reduces the attraction between oppositely-charged ions in salt crystal
The stronger electrostatic interactions between the solvated ions and water molecules
lowers the energy of the system
What happens to the dissolving of NaCl?
entropy increases, spontaneous, positive enthalpy
Dissolved particles affect what?
boiling point. melting point, osmolarity, viscosity, surface tension, taste, and color
The cytoplasm of cells have
highly concentrated solutions and high osmotic pressure
What happens in hypotonic environments?
Water moves into he cel, stress the plasma membrane, and causes lysis
What cells have prevented?
!. Bacteria and plants have rigid cell walls of sufficient strength to resist osmotic pressure
2. Some freshwater protists have an organelle that pumps water out of cell
3. In multicellular animals, blood plasma and interstitial fluid is maintained at as osmolarity close to cytosol. They also pump out ions into interstitial fluid, or pump water directly using aquaporins
What does the effect of osmolarity depends on
number of dissolved particles and not their mass
When water is a reactant, what happens to reactuons?
produced or consumed in reaction
all forms can form
vam dẻ waals (weak bonds)
all forms of weak attractions are based on
attraction between electrical charges
What are bond measured in?
kJ or kcal
Strong covalent bonds
493 kj/mol
Weak bonds
4-30 kJ/ mol, broken by thermal energy.
Hydrogen bonds
dipole movement of NH/OH molecules
Ionic interactions
electrostatic interactions between permeantly charge species, or between the ion and a permanent dipole
dipole interactions
electrostatic interactions between uncharged polar molecules
Van der Waals interactions
weak interactions between all atoms, regardless of polarity, attractive and repulsive components
Hydrophobic effect
the ordering of water molecules around non polar substances
What is hydrogen bonds?
strong dipole-dipole or charge-dipole interaction that a rises between an acid and a base
hydrogen bonds with neutral atom
2-6
hydrogen bonds with one charged atom
12-21 kJ/mol
regarding hydrogen bonds, what two most frequent electronegative bonded to?
nitrogen and oxygen
When is hydrogen bonds are the most strongest?
when the bonded molecules are oriented to maximize electrostatic interaction
In comparison to covalent bonds and hydrogen bonds, which one is weaker?
hydrogen is weaker and have a 2-21 kJ/mol, which indicates that the bond distance is greater with H bonds
What is the source of unique properties of water?
H-bonds
Why is H bond important?
structure and function of DNA, proteins, lipids, and sugars
What is h bond involved in?
enzyme/substrate, hormone/receptors interactions, mRNA with tRNA
What can water both serve as
h-bond donor and H-bond acceptor
With four h-bonds per water molecules gives water its?
-high boiling
-high melting point
-large surface tension
True or false: Hydrogen bonds between neighboring molecule are weak relative to the H-O covalent bonds
True
Ionic bons
opposite charges attract, neutralized oppositely charged groups; 12-17 kJ/mol
Where does van Der waals forces arise from?
nonspecific attractive forces that occurs when two atoms come close to each other, induces fluctuating charges caused by the nearness of the molecules
Van der Waals radius
attractive and repulsive forces balance at a certain distance which is specific for each atom
Organic molecules that tend to form H-bonds are
water soluble
The energy of H-bonds is much greater Thant that of Van der Waals interactions
molecules will form H-bonds in preference of van der Waals interaction
What cannot form H-bonds H-bonds?
Benzene and oil
Nonpolar may seem ordered, however there’s a favorable entropy form water’s point of view
more self interactions; less clustering
Polar molecules form
excellant H bond and soluble in water
