Lecture 3 Flashcards
What atoms make up more than 99% of the cell mass
C, N, O, H
What is the atomic number
number of protons or # of electrons
How to calculate atomic weight
number of protons + # neutrons
What is an isotope
same number of protons different number of neutrons
What’s the difference between an element and an atom?
- element is a substance that can’t be broken down to any other chemical form; made up of a single type of atom
- atom is the smallest part of and element that still retains its distinctive chemical properties
what is composed of elements
a periodic table
Whats the difference between a molecule and a compound
- a molecule has two or more atoms join together chemically
- a compound is a molecule that contains at least 2 different elements
What determines how atoms interact
outermost electron because unfilled electron shells are less stable that a filled one therefore an atom with an unfilled electron shell will interact with another atom to complete their outermost cell
What is a covalent bond
- strong bonds being formed by the sharing of electrons between adjacent atoms
- the shared electrons complete the outer shell of both atoms
What is bond length
when attractive forces (+ and -) and repulsive forces (+ and +) are in balance
Compare single vs. double bonds
- single bonds: free rotation around the bond axis when a single pair of electrons is shared
- double bonds: no free rotation around the bond axis when two pairs of electrons are shared
What is bond strength/ dissociation energy
the amount of energy required to break a chemical bond
what is electronegativity and what is its implication on covalent bonds
- generally, a single covalent bond between two atoms results in an unequal sharing of electrons due to the difference in electronegativity resulting in polar covalent bonds
- electronegativity is the indication of an atoms ability to attract an electron
What is a dipole moment
- it measures the polarity of a bond or molecule
- it is a vector quantity and is the sum of the magnitude and direction of each individual bond dipole
what are non-Covalent interaction and give examples
- bond that does not involve sharing electrons
- individually weak, but cumulatively very strong
- examples: charge-charge electrostatic interactions, hydrogen bonds, Van Der Waals
What feature of non covalent bonds are important to the dynamic nature of the cell?
- non covalent interactions are weak enough that they are continually being formed and reformed at room temperature
ionic bonds
- result from a gain or loss of electron
- generally from atoms with only 1 or 2 electrons in their outer shell
- two atoms held together with electrostatic interactions
Hydrogen bond
- an interaction between a covalently bonded hydrogen atom on a donor group and a pair of non bonded electrons on a acceptor group
what is a donor group and hydrogen acceptors
- donor group is a hydrogen attached to an electronegative atom (usually N or O)
- hydrogen acceptors are electronegative atoms (usually N or O)
acid
substances that release protons when dissolved in water
base
substance that accepts protons when dissolved in water
What is sugars general formula
(CH2O)n
What are sugars
- they are called carbohydrates because of their composition
- the simplest sugars are called monosaccharides
- monosaccharides can be joined together through glycosidic bonds to form disaccharides ( 2 monomers together), oligosaccharides (2-10 monomers) and polysaccharides (>10 monomers)
What are sugars used for
- energy source (ex. glucose or can be stored as glycogen)
- can be used for structure (ex. cellulose that forms cell wall)
- slime, mucus
- modification of lipids and proteins
- involved in information storage of our DNA
