Textbook Notes (368,098)
Canada (161,641)
Biology (657)
BIOLOGY 1A03 (168)
Chapter 2

Biology Chapter 2.docx

5 Pages
118 Views
Unlock Document

Department
Biology
Course
BIOLOGY 1A03
Professor
Lovaye Kajiura
Semester
Spring

Description
Biology Chapter 2: Water and Carbon: The Chemical Basis of Life Bernard Ho September 11, 2010 Chemical Evolution − Proposition that in early Earth, simple compounds in the atmosphere and ocean combined to form larger, more complex substances − Process responsible for this pattern was the conversion of kinetic energy in sunlight and heat to chemical energy in the form of bonds between atoms that formed large, complex compounds − Hypothesis was that one complex compound was able to self-replicate and as it multiplied, chemical evolution became biological evolution − Eventually a self-replicating molecule became surrounded by a membrane − FUNCTION FOLLOWS STRUCTURE − Chemical evolution got under way because o Abundant sources of outside energy were available to trigger endergonic reactions o Some of these molecules produced by chemical evolution are found in organisms living today Building Blocks of Chemical Evolution − An atom is most stable when its valence shell is filled − One way that shells can be filled is through the formation of chemical bonds − Covalent bonding (sharing of electrons) o As two hydrogen atoms move closer together, their positively charged nuclei repel each other and negatively charged electrons repel each other o But each protons attract both electrons and vice versa o Covalent bonds form when the attractive forces overcome the repulsive forces o Nonpolar covalent bond − Asymmetric sharing of electrons results in polar covalent bonds (dependent on electronegativity) − Ionic bonding (transferring of electrons) − The degree to which electrons are shared in chemical bonds forms a continuum − Mass of one mole of any molecule is the same as its molecular weight (sum of n= m mass numbers of all atoms in a molecule) expressed in grams ( M ) − Molarity is the number of moles of the substance present per litre of solution Properties of Water − Water is vital as a universal solvent − When two liquid water molecules approach each other, partial positive charge on hydrogen attracts partial negative charge on oxygen to form hydrogen bonds − Hydrogen bonding allows almost any charged or polar molecule to dissolve in water − Cohesion o Binding between like molecules o Adhesion (binding between unlike molecules) o Water is cohesive due to its hydrogen bonds o Because hydrogen bonding exerts a pulling force at the surface of any body of water, water molecules are not stable at the surface o Water is most stable when its total SA is minimized so it will resist any force that increases its SA o Resistance makes water surface act as if it had an elastic membrane (surface tension) − Water is denser as a liquid than solid o Water expands from liquid to solid o Hydrogen bonds in ice cause the water molecules to form a regular and repeating structure, giving fairly large amounts of space between molecules − Water has a high capacity for absorbing energy o Specific heat is the amount of energy required to raise the temperature of o 1 gram of substance by 1 C o Large amounts of energy needed to break hydrogen bonds Acid-Base Reactions and pH − Water molecules continuously undergo a chemical reaction (dissociation) into hydrogen ions and hydroxide ions − Substances that give up
More Less

Related notes for BIOLOGY 1A03

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit