Tutorial - Week 6 - REVISION (PAGE 36 TUT 7) Flashcards
Nucleic acids:
- 2 types of nucleic acid
- polymers of…?
- Nucleotides are linked by…?
- Polynucleotide chains have a…?
- Nucleotide chains are read from…?
Label and describe the parts of a nucleotide
What are the roles of nucleotides? (3 points)
Label these two nucleic acids
Differences between DNA and RNA
- 3D structure
- Sugar of each?
- Bases differences?
- Location?
- Stability?
- Type?
- Function
DNA is formed by
two…?
complementary
antiparallel strands
What is the direction of DNA?
5’ to 3’
Base pairing is very specific and follows which rule? What binds to what?
Chargaff’s rule:
[purines] = [pyrimidines]
[A]=[T]
[G]=[C
A-T has how many bonds?
What kinds of bonds are they?
2
hydrogen bonds
G-C has how many bonds?
What kinds of bonds are they?
3
Hydrogen bonds
- Base pairing and H-bonds are very important to…?
- Which base pairs have the strongest pairing bond?
- Hold the complimentary strands
- G-C Pairing is stronger than A-T
What is mRNA a messenger between?
messenger between DNA and protein
How does the DNA sequence becomes a functioning protein?
What is it called when more than one codon can code for the same amino acid?
Redundancy in the genetic code means that most amino acids are specified by more than one mRNA codon.
- Which amino acid is tRNA linked to?
- How is the AA attached to which end of the tRNA?
- What group of the AA is activated to facilitate formation of peptide bond?
- Theres a link between the AA and the __________ in the mRNA
- Codons = ?
- tRNA with the correct anticodon binds to…?
- The corresponding amino acid
- AA is covalently attached via an ester bond at the
3’ end of tRNA - Carboxyl group of AA is activated to facilitate
formation of peptide bond - Link between AA and information in the mRNA
- sequences of 3 bases that code for 1 AA
- the respective codon in the mRNA while being
translated in the ribosome
What kind of molecule is this?
tRNA molecule
- How many standard AAs are there?
- They all have what features?
- At physiological pH they are called? Meaning?
- They are ampho…? Meaning?
- They are ________ molecules. What feature is the centre of this?
- There are 20 standard amino acids
- They have an amino group and a carboxylic acid group bounded to
the same carbon atom (a-Carbon) - At physiological pH they are zwitterions
(contain both negative and positive charges) - They are amphoteric
(contain both acid and base properties) - They are chiral molecules
(a-Carbon is a chiral center: it
is bound to four different groups )
Label the different parts
Top COO- is the carboxyl group
H3N+ is the amino group
H on right of image is the hydrogen atom
R is the sidechain group
C in the centre is the alpha-carbon which is a chiral centre and is bound to the four other different groups
What are enantiomers?
each of a pair of molecules that are mirror images of each other - for example amino acids
If these two chemical both have the same chemical make up and are both Alanine, then what in their nomenclature allows us to differentiate them?
What are they two one another?
The L- or the D- before their names (means L (left-handed) and D (right-handed))
Enantiomers
Mirror images of amino acids are ________, they cannot be ___________, and are called __________
isomers
superimposed
enantiomers
Which one is L-Alanine and which one is D-Alanine?
All molecules with a chiral centre are __________. Meaning?
optically active
The use of polarized light is the only way to distinguish these two isomers
- L -Amino acids: rotate polarised light to the left
- D -Amino acids: rotate polarised light to the right
Enantiomers have identical…/
Physico-chemical properties
Biology, selected one of the enantiomers of AAs (L- or D-) for convenience. Which one and give examples of the effects
L -Amino acids are predominant in nature (e.g. all enzymes, protein
receptors are made of L -amino acids, and they bind/recognise only
proteins/substrates that have the same L -configuration.
Some peptides have D -amino acids in their composition - what are they found in in nature?
- Components of bacterial walls
- Amphibian antimicrobial peptides
- The 20 common amino acids differ how?
- How are they classified?
- What are the 5 groups they are divided into?
- They differ in the structure of their side chains
- Divided into groups
- Classified based on the chemistry of the R group
(side chain): - Non-polar or hydrophobic
- Uncharged Polar
- Charged Polar
- Acidic (-)
- Basic (+)
- Non-polar or hydrophobic
T/F: The peptide bond is often written as a double bond
In the peptide bond what is being shared between what?
What does the sharing of the electrons in this way result in?
False - often written as a single bond
In this bond, there is a pair of electrons from
the Nitrogen shared between the two atoms C-N
This pushes the electrons from the carbonyl double bond towards the oxygen, forming an oxygen anion
Explain Peptide bond resonance
Shared electrons between C-O and C-N
Resonance effect increases stability of the C-N bond, makes it shorter, and decreases rotation around that bond
What process is being shown here?
Polymerisation of amino acids
- Amino acids polymerise to form…? Via?
- What is released during the bonding of two AAs and what is added to allow for the splitting of two AAs?
- Peptide bonds are _____________
that link…?
- Amino acids in a polypeptide chain are called _________
- This peptide has ______ amino acid residues = ___________
- This peptide has ______ peptide bonds
- The overall charge of this peptide is …?
- residues
- 5 = (Ser-Gly-Tyr-Ala-Leu; SGYAL)
- 4
- 0
Label the charge values across the bottom of the spectrum
pKa = ?
pl = ?
pl = (formula)?
pKa = pH at which the H + dissociates: the lower the pKa, the stronger the acidic
properties of the group
pI = isoelectric point, is the pH at which the net charge is 0 (iso = equal)
pI = (pK 1 + pK 2 )/2 = 5.97
Label and describe each level of protein structure
What are the chemical interactions that stabilise higher levels of
protein structure? Describe each
What determines the intermolecular bonds?
Why are these interactions important?
What are lipids?
Are they soluble in water?
Do they form polymers like other biomolecules?
What do they possess?
What are the important biological functions they have?
What are the types of lipids that function as energy storage? Draw each
- What are fatty acids?
- What do mammals not have to produce fatty acids with a doulble bond after carbon 9? (Counting from the COOH)
- How are fatty acids that have a double bond after carbon 9 obtained?
- Essential fatty acids are known as Omega (w = omega symbol when drawn in the greek way) fatty acids (w6 and w3), notation in which
the location of the bond is…?
- Fatty acids that humans and other mammals need (e.g. vision & nervous system) but cannot synthesise
- Mammals don’t have enzymes to produce fatty acids with a double after carbon 9
(counting from the COOH) - Fatty acids that have a double bond after carbon 9 need to be obtained via diet
- counted from the CH 3 terminal
What are the three membrane structure lipids? Draw each
Lipid bilayer: Phospholipids, sphingolipids and cholesterol are virtually ________ in water
But they are _________
insoluble
amphipathic
How do the structural lipids form the lipid bilayer?
When mixed with water they cluster together and form a lipid bilayer
- via hydrophobic effect = reduction of contact with water; hydrophobic groups in contact with each other
- Expose the polar group to water
What model is used to describe the surface of the lipid membrane? Explain
Fluid mosaic model: mosaic with a pattern (lipid and protein organization), but fluid, dynamic
- Interactions between its components are noncovalent
- Components can move laterally in the plan of the membrane
What are the lipid and protein components of the lipid bilayer?
What are the lipids involved in signalling, both intracellularly and extracellularly? Name and describe all
