Tutorial - Week 1 - Revision of chemical bonds & biochemical calculations Flashcards
What is valency?
The number of electrons an atom can accept into it’s outer (valence) shell in order to have a full outer shell
Name the element and it’s valency
Interactions between atoms result in
_____________
Chemical bonds
What are the types of chemical bonds?
Covalent bonds, ionic bonds, hydrogen bonds, van der Waals interactions
___________ bonds hold atoms together to form _________ molecules.
Covalent
stable
Define Polar covalent bonds and give an example
The electrons are unequally shared by the atoms and spend more time close to one atom than the other.
For instance in the O-H bond, the O is more electronegative and
slightly negative (d-), whereas the H is more positive (d+)
Define non polar covalent bonds and give examples
The electrons are shared by the
atoms more or less equally (e.g. H2, O2, CH4)
T/F: covalent bonds are weak and break easily
False: Covalent bonds are stable, and don’t break easily
T/F: Covalent bonds are stronger than ionic bonds.
True
What are the types of diagrams for visualising chemical bonding?
Electron distribution diagram
Lewis dot structure and structural formula
Space-filling model
List the name and molecular formula and draw all the diagrams for visualising hydrogen (H2)
List the name and molecular formula and draw all the diagrams for visualising oxygen (O2)
List the name and molecular formula and draw all the diagrams for visualising Water (H2O)
List the name and molecular formula and draw all the diagrams for visualising methane (CH4)
What is the difference between covalent and ionic bonds?
Covalent bonds are when atoms share electrons and are bonded together due to their electron shells being filled.
Ionic bonds occur when two charges elements attract each other and stay together due to the attraction of the charge
What is hydrogen bonding? Give an example
Is an electrostatic attractions between a H-atom in a polar covalent bond with a atom,
or chemical group, with a pair of electrons.
(e.g. in the O-H bond in the water molecule, the H will have a slight positive charge,
because the electrons are pulled more strongly towards the O. Therefore the H will be
attracted to neighbouring atoms with lone electrons).
Some functional groups are H-bonds _________ (_____,_____), and others can work as H-bonds _________ (_______,________).
Donors - OH, NH2
Acceptors - C=O, C-N
Which side are the hydrogen donors and which side the hydrogen acceptors?
Where are the hydrogen bonds in these?
Are h-bonds stronger or weaker than covalent and ionic?
Weaker
What is one of the most important, if not the most important h-bond in life?
The h-bonds in between complimentary bases of DNA
Are h-bonds intermolecular or intramolecular?
Both!
In terms of van der Waals forces:
Where do they normally occur?
Normally occur between neutral apolar molecules/groups with non-polar covalent bonds
In terms of van der Waals forces:
When do they normally occur?
It occurs when electron distribution around an atom undergoes fluctuations, which create instantaneous dipoles
(positive and negative)
In terms of van der Waals forces, what special conditions for the molecules needs to happen?
The molecules/groups need to be very close together.
What are van der Waals/London dispersion forces sometimes referred to as?
Hydrophobic interactions
How strong are individual van der Waals interactions? How strong can the overall interaction be?
Example?
Weak when they are individual but can be strong when many atoms/groups are close together.
Gekko’s use these forces to stick to walls
What is the force in the image?
van der Waals/London dispersion forces
What is the hydrophobic effect?
Do they interact with water?
The aggregation of nonpolar molecules in aqueous solution, excluding water molecules; Hydrophobic groups interact with each other to avoid contact with water.
Is the hydrophobic effect a chemical bond?
Not exactly a chemical bond but the exclusion of water is promoted by hydrophobia
The close proximity of hydrophobic groups due to hydrophobic effect can lead to ____________________
van der Waals interactions
What is the hydrophobic effect important for?
This effect is important for the arrangement of lipids in cell membranes, and in protein folding.
What bond/effect is this?
The hydrophobic effect
Label each of these non-covalent bonds between biomolecules when in aqueous solvent
Biomolecules are compounds of ________ with a variety of _________________
carbon
functional groups
The chemistry of living organisms is organised around ________
carbon
Carbon (C) can form (list all 4)
- Single covalent bonds with hydrogen atoms (H)
- Single or double bonds with oxygen (O) and nitrogen (N) atoms
- Can form single bonds with up to four other C atoms
- Two carbon atoms can share two (or three) electron pairs to form double (or triple) bonds.
Which has the highest bond strength? Which has the lowest?
As bond strength ________, the atoms in the bond are pulled more tightly together and the length ________
increases
decreases
The strength of a bond is measured by the ______ _________ ____ _______ ___. The stronger the bond, the greater the
energy required to break it.
energy required to break it
What are functional groups?
- chemical groups that can participate in chemical reactions, some of the functional groups are important
for the formation of biological molecules (i.e. DNA, proteins, carbohydrates and lipids)
Name all examples of functional groups
- Hydroxyl group (OH), present in alcohol molecules
- Carbonyl (C=O), part of other functional groups
- Carboxyl/carboxylic acid (COOH/ COO-)
- Amino group (NH2/NH3+)
- Sulfhydryl/thiol group (SH)
- Phosphate group (OPO3H2/OPO32-)
- Methyl group (CH3), common in biomolecules
_________, is an abbreviation and any group, in which a carbon or hydrogen atom is attached to the rest of the molecule
R-group
Functional groups are collections of _________
attached to the ____________ of an organic
molecule and confer __________ ___________.
atoms
carbon skeleton
specific properties
How many functional groups minimum does every single biomolecule have?
At least one
What are the four types of macromolecules?
Proteins
Carbohydrates
Lipids
Nucleic acid
Name all these molecules
Are these polar or non-polar groups?
_______________: are hydrophilic (i.e. ‘water- loving’, dissolve easily in water), can form H-bonds with water
Polar molecules/groups
Polar molecules/groups: are ___________ (i.e. ‘water- loving’, dissolve easily in water), can form ______________________
hydrophilic
H-bonds with water
_________________: are hydrophobic (i.e. ‘water phobia’, do not dissolve in water). They cannot form H-bonds with water.
Non-polar molecules/groups
Amphipathic molecules: possess ________ and _________ ___________
polar
non-polar groups
Name the reactants, coefficients, products, and reactant side and product side
Chemical reactions occur when ____________ between atoms are _________ or _______.
chemical bonds
formed
broken
The substances that go into a chemical reaction are called _____________ or ____________, and the substances produced at end of the reaction are ___________.
reactants or substrates
products
Equations must be balanced to reflect the law of __________________ which is ____________________________________
conservation of matter
no atoms are created or destroyed in a normal chemical reaction
List the following equations used in the labs:
- Calculate concentration
- Make dilution
- Determine number of moles
- Use lambert-beer law
Write the calculations checklist
