Class Notes (808,211)
Canada (493,074)
Biology (2,220)
BIO120H1 (1,171)

BIO240H Lecture 2.doc

4 Pages
Unlock Document

University of Toronto St. George
Jennifer Harris

Lecture 2 Intro to Nucleic Acids & Proteins Nucleic Acid Chains 1. DNA is synthesized from deoxyribonucleoside triphosphates, otherwise known as: dNTP’s – things that are used to make this linear structure. 2 phosphates get removed during this process. 2. RNA is synthesized from ribonucleoside triphosphates, or: NTP’s 3. Nucleotides are linked by: phosphodiester bonds (through phosphate groups) Base Pairing - DNA is double stranded while RNA is single stranded – in order for replication & transmission of info contained in DNA strand, it needs to be double-stranded. Basis of exactly how those strands together is mediated through process called base pairing – ensures that base opposite of it in opposing strand is specific base b/c not all bases are complementary to each other. 1. Holds DNA double helix together 2. A-T – 2 H-bonds G-C – 3 H-bonds - H-bonds form, helping to keep 2 strands together - Strands run anti-parallel 3 forces that keep DNA together: 1. H-bonds – dipole-dipole interactions with each other 2. Van der Waals – are induced dipoles (slight variation in positive & negative charge) – clouds of e- that when they come near each other induce dipoles in each other. 3. Hydrophobic interactions – tendency to avoid water – stacking b/w bases which are very hydrophobic particularly ring structure – tend to like to stack in certain way. DNA Structure - Info is always read 5’ to 3’ – DNA is composed of 2 antiparallel strands. Has ladder-like structure. Same info present on 1 strand is on other b/c of complementarity of bases & this redundancy is extremely important for preservation of info. - DNA structure is organized into double helix – ladder twists around itself forming major groove & minor groove. Interactions with turns of helix make DNA more stable. Review Q’s 1. Strands in double helix are antiparallel (go in opposite direction) – this means that 1 strand is 5’  3’ while its partner is 3’  5’ 2. What are 2 ends of DNA strand composed of? 5’ = P, 3’ = OH Sequence of 2 strands are: complementary. Strands can be unzipped (reversible – can be reannealed). This is important for: DNA replication (making copy of DNA), protein synthesis (i.e. making RNA copy  protein) Unzipping Helix 1. Heating denatures double-stranded DNA by: disrupting H-bonds b/w bases (specifically those H-bonds mediating base pairing holding 2 strands together) 2. Temp at which DNA denatures is called: T M 3. Denaturation of DNA is reversible process Review Q’s 1) Why is T oM DNA rich in G-C base pairs higher than T of DMA rich in A-T base pairs? G-C have 3 H- bonds; A-T have 2 2) Why do high temp organisms such as bacteria around undersea vents have G-C rich genomes? DNA would denature Intro to Protein Structure Ex: Primary (sequence) - AA sequence Secondary (local folding) - a-helix, B-sheet Tertiary (long-range folding) - 3D structure Quaternary (multimeric organization) Supramolecular (large-scale assembly) - protein assemblies Protein Structure 1. Proteins are composed of AA 2. AA side-chain or R group is variable & determines type of AA (only part of entire AA that varies – analogous to base in nucleotide) 3. 4 major categories of AA: basic (positively charged AA), acidic (negatively charged), uncharged polar (1s with hydroxyl groups on them), non-polar (hydrophobic AA) Mutational steps b/w codons 1) What is min # of mutational steps b/w AA? - # mutations b/w codons for different AA’s 2) How many mutational steps required to get from a codon for proline to one for cysteine, minimum? 2 (CCG  UGC) 3) … maximum? 3 (CCG  UGC) Review Q’s 1. Groups of AA’s with similar properties tend to be clustered in codon table. 2. Codons of AA’s with similar properties tend to have fewer mutational steps b/w them. 3. 1 random mutation in codon is less likely to result in dramatic change in AA properties than 2 random mutations. Synthesis of Proteins - Reactions of carbonyl group with amino group of next AA in condensation reaction that forms peptide bond (molecule of water is lost). - Proteins also have direction: go from N-terminus (where amine group is hanging off) to C-terminus (where carboxyl group is hanging off). Side chains are always attached to alpha-C – never connected to C attached to peptide bond. Review Q’s 1. Why are properties of AA side chains important? Folding & function – properties of side chain determine property of protein as whole (3D structure determines function) 2. What kind of covalent bond connects AA in chain to form proteins?
More Less

Related notes for BIO120H1

Log In


Don't have an account?

Join OneClass

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

Sign up

Join to view


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.