Chapter 2- Water Flashcards
The structure and function of the cell are stabilized by what?
Weak interactions
How can weak interactions stabilize the structure and function of the cell?
Many weak bonds can result in large stable structures. Weak bonds allow transient interactions so a substrate can bind to an enzyme and the product can leave the enzyme or a hormone can bind to its receptor and then dissociate from the receptor after the signal has been received.
What did Robert Brown view and conclude?
He saw under a microscope, that pollen granules suspended in water were moving around. He concluded that the water and gas molecules in the environment are bouncing randomly about at a rate determined by temperature. The movement of the particles is known as Brownian motion.
How is Brownian motion observed in the cell?
Water facilitates the flow of energy and information transformations through Brownian motion. Enzymes find their substrates, fuels can be progressively modified to yield energy, and signal molecules can diffuse from their sites of origin to their sites of effect.
What causes cells to be mobile?
Water
What about water makes it a solvent for charged or polar molecules?
Its polarity and ability to form hydrogen bonds.
The hydrophobic effect
When molecules sequester themselves away from water
What processes are reversible, weak non covalent forces important in?
Replication of DNA, the folding of proteins into 3D forms,the specific recognition of reactants by enzymes the detection of molecular signals.
What are the three fundamental, non covalent bonds?
- Ionic bonds or electrostatic interactions
- Hydrogen bonds
- Van der waals interactions
All differ in geepometry, strength, and specificity. And are greatly affected in different ways by water.
Ionic bonds def
The interactions between distinct electrical charges on atoms. Usually take place between two atoms, one completely positive charge, and one completely negative charge.
The energy of an electrostatic interaction equation
E=kq1q2/Dr
E is energy, q1 and q2 are the charges on the atoms, r is the distance between the two atoms (in angstroms), D is the dielectric constant, k is proportionality constant.
How does water affect the electrostatic interaction of a molecule?
It decreases it because of its polar characteristics. Water can dissolve virtually any molecule with sufficient partial charge or complete charges on the molecules to interact with water.
Ex. When salt dissolves, the ionic bind between Na+ and Cl- is destroyed and the individual ions bind to water.
Are hydrogen bonds or covalent bonds stronger?
Covalent, energy of covalent is418 kj/mol compared to hydrogen bonds of 8-20 kj/mol
Van der waals interactions def
Neither polar nor charges molecules can interact with each other through van der waals interactions. The basis is that the distribution of electronic charge around an atom changes with time, and at any time, the charge distribution isn’t symmetric and regions will be partially negative and others partially positive.
What is the van der waals contact distance?
Ranges from 3-4 angstroms. It is the distance between two molecules that have van der waals attractions. If the molecules go closer than the contact distance, they feel very strong repulsive forces because of their electron clouds overlapping.
What is the basis of the fact that oil and water separate?
When non polar molecules are added to water, the coalesce into a single larger molecule, becoming more organized. The second law of thermodynamics in that entropy measures randomness
Why are non polar solute molecules driven together in water?
They are driven together because when they associate, the release water molecules. This is called the hydrophobic effect, and is driven by entropy.
Amphiphilic molecule def
Also called amphipathic molecule. A molecule with two distinct chemical personalities, one part that can react with water, and another that cannot react with water. When exposed to water, an amphiphilic molecule orients itself such that the hydrophilic head groups interact with the aqueous medium and the hydrophobic tails are sequestered away from the water and interact only with one another.
How do proteins spontaneously assume an ordered structure and yet entropy increases?
The hydrophobic effect introduces order. Some amino acids have non polar side chains and they have strong tendency to associate with one another in the interior of the protein. Because of these interactions between the hydrophobic amino acids, we see an increase in the entropy of water.
Why is maintaining the proper pH in the body so vital?
Alterations to the pH ca drastically affect the internal electrostatic environment of an organism, which can alter the weak bonds that maintain the structure of biomolecules. Altered structure usually means loss of function.
Does a strong acid have a small or large ka value?
Larger the ka, the stronger the acid.
What is a buffer?
An acid-base conjugated pair that resists changes in the pH of a solution.
They are important in biochemistry because the biomolecules being investigated by scientists are sensitive to pH so biochemists use buffers to maintain the right pH
In vitro vs in Vivo
In vitro means in glass, or in effect, in a test tube. I vivo means in the living organism.
What is compensated respiratory alkalosis
It is the name for the mechanism of blood-pH control where the conjugated acid base pair of H2CO3/ HCO3- acts as a buffer. Protons released by an added acid will combine with the bicarbonate ion and the pH isn’t affected. The buffer system is effective because we can rapidly adjust the quantity of the buffer. If there is an influx of acid in the blood, reactions will proceed but the ration of H2CO3/ HCO3- is maintained.
