Why is carbon the backbone of so many biologically relevant molecules?
Carbon is the Key Molecule
of Life
* Carbon also forms and breaks bonds with other C atoms, allowing for the formation of long carbon
chains called carbon skeletons.
- Carbon is the 4th most abundant
element in the universe! - Compounds composed only of carbon and hydrogen
are called hydrocarbons.
How many valence electrons does carbon have and how many chemical bonds does it want to
make to fill its outer shell?
- Carbon has 4 electrons in its
valence shell. This allows it to
form four covalent bonds.
What is the basic formula for a hydrocarbon? A carbohydrate? A protein? A nucleic acid? A
lipid? Also, what are their functional groups?
- Hydroxyl group OH
- Carbonyl group C=O (Aldehydes are at the end of the carbon skeleton, ketones are not)
- Carboxyl group COOH
- Amino Group NH2 (Amino group +
carboxyl group = amino acid (the building blocks of proteins) - Phosphate group PO4
- Methyl group CH3 (important for gene
expression and cell membrane formation)
What is an isomer? Know the three kinds
organic compounds with the
same molecular formula, but different structures
Structural isomers have the same molecular formula but a different arrangement of atoms.
Geometric (or cis/trans) isomers differ in the placement of functional groups around carbons connected by a double bond.
Enantiomers are mirror images of each other
What is a monomer? A polymer? A macromolecule?
Monomer: a subunit (molecule) that serves as a building block for a polymer. (“mono” = one)
Polymer: a large molecule consisting of many identical or similar monomers. (“poly” = many)
Macromolecule: large molecules, essential for life, that are composed of repeating smaller subunits called monomers
There are four classes of
macromolecules in living things:
1) Carbohydrates
2) Lipids
3) Proteins
4) Nucleic acids
What chemical reaction is used to “stick” monomers together to make polymers?
dehydration synthesis= formation of
larger molecules from smaller reactants, accompanied
by the loss of a water molecule
What is a catalyst?
a substance that speeds up a chemical reaction without being consumed in the process.It lowers the activation energy required for a reaction to occur
What is the definition of hydrolysis? How does this relate to breaking down polymers back into monomers?
break bonds between
monomers by adding a molecule of water
What is a monosaccharide? Disaccharide? Polysaccharide?
There are three basic classes of CHOs (carbs):
i) Monosaccharides = single unit sugars, with a basic ratio
of 1C:2H:1O (i.e., CH2O). e.g. glucose & fructose.
ii) Disaccharides = two monosaccharides joined via a
dehydration synthesis. e.g sucrose (table sugar) which is a molecule each of glucose and fructose.
iii) Polysaccharides = may contain hundreds to thousands
of monosaccharides. (E.g., starch)
What is starch? Glycogen? How do they differ?
Starch consists entirely of glucose molecules linked together and can be straight or branched
Starch is the simplest polysaccharide and is
used as an energy storage molecule in plants
Glycogen is a highly branched storage polysaccharide of glucose.
It’s most often found in muscle and liver cells
How is cellulose different from starch or glycogen?
A polymer of glucose, but it contains different linkages that cannot be broken down by most animals.
Certain animals have microbes in their guts that can break the bonds
linking the glucose molecules
What do we mean by primary, secondary, tertiary, and quaternary structure of a protein?
There are four structural levels of proteins:
a) Primary structure: linear sequence.
b) Secondary structure: α-helix or β-pleated sheet.
c) Tertiary structure: complex globular shape.
d) Quaternary structure: interaction of two or more polypeptides.
What holds the secondary structure of proteins together? What about the tertiary structure?
Secondary structures maintained by hydrogen bonds between atoms of the backbone.
Tertiary structures stabilized by interactions between R groups.
What happens when a protein becomes denatured?
They unravel and lose their 3-D shape.
Once they lose their shape, they also lose their functional abilities.
can be caused by pH changes or heat,
for example, and may be reversible, but not always.
What do we call the bond that forms between the carboxyl group of one amino acid with the amino group of another?
A peptide bond.
Most are at least 100 amino acids in length, some are 1000 or more
What are some of the functions of proteins?
- Enzymes= catalyze/regulate chemical reactions
- Transport = embedded, molecular transport across the cell membrane
- Defensive = antibodies
- Signal= chemical messengers that help coordinate activities and reactions in the body
- Receptors = help to transmit and receive signals between different body cells
- Contractile= muscle cells, for example
- Structural = fibrous proteins found in hair and collagen that makes up connective tissues)
What are the four nitrogenous bases in DNA? RNA?
In DNA are adenine (A), guanine (G), cytosine (C), and thymine (T)
In RNA, the bases are adenine (A), guanine (G), cytosine (C), and uracil (U)
What is complimentary base pairing? Which bases pair together?
Complementary base pairing is the specific pairing of nitrogenous bases in nucleic acids:
adenine (A) + thymine (T) in DNA
or adenine (A) + uracil (U) in RNA
and cytosine (C) + guanine (G).
What does hydrophobic and hydrophilic mean? Are lipids hydrophobic or hydrophilic?
All lipids are hydrophobic.
Hydrophobic is water-fearing; repels water; Nonpolar molecules, which are mainly composed of carbon and hydrogen atoms.
Behavior with water: They will not mix with or dissolve in water
e.g cholesterol, and many polymers.
Hydrophilic is Water-loving; attracted to water; Polar molecules, often containing oxygen or nitrogen atoms.
Readily dissolve or mix with water.
Examples: Sugars, salts, and ammonia.
What class of molecules did we look at that are not considered polymers?
Lipids are not considered polymers since they are not built from repeating monomer subunits.
A triglyceride is composed of one molecule of______ and three molecules of ____________.
a 3-carbon glycerol molecule and three molecules of long-chain fatty acids
What is the primary function of fats/triglycerides?
- Long-term energy storage.
- A gram of fat stores more than twice as muchenergy as a gram of carbs.
- Cushions vital organs.
- Insulates the body (warmth).
- Needed to make up cell membranes.
What do we mean when we say fatty acids are saturated? What are they saturated with?
its carbon chain has the max number of hydrogen atoms attached.
They are “saturated” with hydrogen because there are only single bonds between the carbon atoms
allows a hydrogen atom to bond to every possible carbon site. Solid at room temp
Why do double bonds make fats more likely to be a liquid at room temperature?
contain at least one double bond
between C atoms. Therefore, they DON’T have the max # of H’s. This create kinks in the chains and the closely together, so they’re liquid at room temp.
prevents the molecules from packing together tightly which means the bond is weaker and melts at a lower melting point
