Protein & DNA Flashcards
what provides most of the molecular functions of life?
proteins
what is a protein / another name for a protein?
a string (polymer) of amino acids / polypeptide
amino acid structure
central alpha carbon
amino group NH2
carboxyl group CO2H
hydrogen atom
side chain “R” group
how many “R” groups are there?
20 – different amino acids
what chemical differences can the “R” groups have?
polar/nonpolar
acid/base
others
what determines the proteins function?
structure of the protein
what is the key to life as we know it?
protein structure
define polypeptide
a string of amino acids linked together in a chain by peptide bonds
where do peptide bonds join the amino groups?
at the amino group of one end to the carboxyl group of another amino acid
what type of bond is a peptide bond?
covalent
dehydration rxn
molecule of H2O is lost to form a peptide bond
hydrolysis rxn
H2O is added to break a peptide bond
what direction do the O and H point in a peptide bond
opposite directions
can the peptide bond rotate?
no, it’s planar b/c part of O’s double bond is delocalized onto the N
sequence of polypeptide backbone
NCCNCCNCCN
In polypeptide sequence what # covalent bond is a peptide bond?
Every 3rd
When can a polypeptide be called a protein?
If it has a biological function and is long
Small vs. large proteins
Small can be less than 100 amino acids
Large can be more than 30,000
What happens when proteins are digested?
Broken into small polypeptides then into amino acids
Strand polarity (directionality)
Amino end and carboxyl end
Proteins are started at the amino end
New amino acids added to carboxyl end
What determines the folding pattern of the protein?
Amino acid sequence
Primary structure
Sequence of amino acids coded in the gene
Secondary structure
Hydrogen bonds between parts of the backbone
Two types of structure
Helixes
Alpha helixes are 2ndary
Coiled structure w/ side groups of amino acids sticking out from the sides
Sheets
Beta pleated sheets are 2ndary
Straight regions held side by side
Parallel or antiparallel or both
Amino acid side groups stick out from both sides of the sheet
Tertiary structure
Interactions between amino acid side groups
Affected by interaction of side groups w/ H2O
Involves covalent, ionic, hydrogen, and Van Der Waals bonds
Water molecules pull polar groups to the ____ and push non polar groups to the ____
Outside, inside
What environmental factors affect the folding of proteins?
pH, salt concentration, and heat
Quaternary structure
A protein with several polypeptides
What are the parts of a nucleotide?
Sugar, phosphate, and base
What is another name for a nucleic acid?
Polynucleotide – a polymer (string) of nucleotides
Two types of sugars in a nucleotide
DNA or RNA found on the 2’ carbon
Deoxyribose – DNA has two Hs
Ribose – RNA has an OH and an H
Phosphate
Acidic
Forms connecting bridges between the sugars
Attach to the sugar at 3’ and 5’
The backbone of RNA and DNA is alternating _____
Sugar and phosphate
Bases in nucleic acids
Flat rings made of C & N attach to 1’
Adenine, Thymine
Guanine, Cytosine
Uracil (only in RNA)
New units of nucleotide add to which end?
3’
can RNA & DNA both form double helixes?
yes, but dsDNA is more common
what holds the double helix together?
hydrogen bonding between base pairs
A attaches to T with ___ bonds and G attaches to C with ___ bonds
2, 3
when can two single strands of nucleic acids form a double helix?
if the strands are oriented in opposite directions
if the bases are complementary
The sequence of bases in DNA is…
A genetic code that is read and used to make proteins
How is DNA stored and utilized?
Stored in chromosomes and utilized in the form of short RNAs
How does a cell use DNA?
Copies genes into short ssRNA
What are ssRNA copies called?
mRNA
Where are mRNA transported to?
Ribosomes in the cytoplasm
The molecular secret of life is…?
Strings of DNA code for strings of amino acids
