Tutorial - Week 6 - REVISION (PAGE 36 TUT 7)

Question 1

Answer 1

Question 2

Nucleic acids:

1. 2 types of nucleic acid
2. polymers of…?
3. Nucleotides are linked by…?
4. Polynucleotide chains have a…?
5. Nucleotide chains are read from…?

Answer 2

Question 3

Label and describe the parts of a nucleotide

What are the roles of nucleotides? (3 points)

Answer 3

Question 4

Label these two nucleic acids

Answer 4

Question 5

Differences between DNA and RNA

1. 3D structure
2. Sugar of each?
3. Bases differences?
4. Location?
5. Stability?
6. Type?
7. Function

Answer 5

Question 6

DNA is formed by
two…?

Answer 6

complementary
antiparallel strands

Question 7

What is the direction of DNA?

Answer 7

5’ to 3’

Question 8

Base pairing is very specific and follows which rule? What binds to what?

Answer 8

Chargaff’s rule:
[purines] = [pyrimidines]
[A]=[T]
[G]=[C

Question 9

A-T has how many bonds?

What kinds of bonds are they?

Answer 9

2

hydrogen bonds

Question 10

G-C has how many bonds?

What kinds of bonds are they?

Answer 10

3

Hydrogen bonds

Question 11

1. Base pairing and H-bonds are very important to…?
2. Which base pairs have the strongest pairing bond?

Answer 11

1. Hold the complimentary strands
2. G-C Pairing is stronger than A-T

Question 12

What is mRNA a messenger between?

Answer 12

messenger between DNA and protein

Question 13

How does the DNA sequence becomes a functioning protein?

Answer 13

Question 14

What is it called when more than one codon can code for the same amino acid?

Answer 14

Redundancy in the genetic code means that most amino acids are specified by more than one mRNA codon.

Question 15

1. Which amino acid is tRNA linked to?
2. How is the AA attached to which end of the tRNA?
3. What group of the AA is activated to facilitate formation of peptide bond?
4. Theres a link between the AA and the __________ in the mRNA
5. Codons = ?
6. tRNA with the correct anticodon binds to…?

Answer 15

1. The corresponding amino acid
2. AA is covalently attached via an ester bond at the
   3’ end of tRNA
3. Carboxyl group of AA is activated to facilitate
   formation of peptide bond
4. Link between AA and information in the mRNA
5. sequences of 3 bases that code for 1 AA
6. the respective codon in the mRNA while being
   translated in the ribosome

Question 16

What kind of molecule is this?

Answer 16

tRNA molecule

Question 17

1. How many standard AAs are there?
2. They all have what features?
3. At physiological pH they are called? Meaning?
4. They are ampho…? Meaning?
5. They are ________ molecules. What feature is the centre of this?

Answer 17

1. There are 20 standard amino acids
2. They have an amino group and a carboxylic acid group bounded to
   the same carbon atom (a-Carbon)
3. At physiological pH they are zwitterions
   (contain both negative and positive charges)
4. They are amphoteric
   (contain both acid and base properties)
5. They are chiral molecules
   (a-Carbon is a chiral center: it
   is bound to four different groups )

Question 18

Label the different parts

Answer 18

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

Question 19

What are enantiomers?

Answer 19

each of a pair of molecules that are mirror images of each other - for example amino acids

Question 20

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?

Answer 20

The L- or the D- before their names (means L (left-handed) and D (right-handed))

Enantiomers

Question 21

Mirror images of amino acids are ________, they cannot be ___________, and are called __________

Answer 21

isomers

superimposed

enantiomers

Question 22

Which one is L-Alanine and which one is D-Alanine?

Answer 22

Question 23

All molecules with a chiral centre are __________. Meaning?

Answer 23

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

Question 24

Enantiomers have identical…/

Answer 24

Physico-chemical properties

Question 25

Biology, selected one of the enantiomers of AAs (L- or D-) for convenience. Which one and give examples of the effects

Answer 25

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.

Question 26

Some peptides have D -amino acids in their composition - what are they found in in nature?

Answer 26

- Components of bacterial walls - Amphibian antimicrobial peptides

Question 27

1. The 20 common amino acids differ how? 2. How are they classified? 3. What are the 5 groups they are divided into?

Answer 27

1. They differ in the structure of their side chains 2. Divided into groups - Classified based on the chemistry of the R group (side chain): 3. - Non-polar or hydrophobic - Uncharged Polar - Charged Polar - Acidic (-) - Basic (+)

Question 28

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?

Answer 28

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

Question 29

Explain Peptide bond resonance

Answer 29

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

Question 30

What process is being shown here?

Answer 30

Polymerisation of amino acids

Question 31

1. Amino acids polymerise to form...? Via? 2. What is released during the bonding of two AAs and what is added to allow for the splitting of two AAs? 3. Peptide bonds are _____________ that link...?

Answer 31

Question 32

1. Amino acids in a polypeptide chain are called _________ 2. This peptide has ______ amino acid residues = ___________ 3. This peptide has ______ peptide bonds 4. The overall charge of this peptide is ...?

Answer 32

1. residues 2. 5 = (Ser-Gly-Tyr-Ala-Leu; SGYAL) 3. 4 4. 0

Question 33

Label the charge values across the bottom of the spectrum

Answer 33

Question 34

pKa = ? pl = ? pl = (formula)?

Answer 34

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

Question 35

Label and describe each level of protein structure

Answer 35

Question 36

What are the chemical interactions that stabilise higher levels of protein structure? Describe each What determines the intermolecular bonds? Why are these interactions important?

Answer 36

Question 37

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?

Answer 37

Question 38

What are the types of lipids that function as energy storage? Draw each

Answer 38

Question 39

1. What are fatty acids? 2. What do mammals not have to produce fatty acids with a doulble bond after carbon 9? (Counting from the COOH) 3. How are fatty acids that have a double bond after carbon 9 obtained? 4. 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...?

Answer 39

1. Fatty acids that humans and other mammals need (e.g. vision & nervous system) but cannot synthesise 2. Mammals don’t have enzymes to produce fatty acids with a double after carbon 9 (counting from the COOH) 3. Fatty acids that have a double bond after carbon 9 need to be obtained via diet 4. counted from the CH 3 terminal

Question 40

What are the three membrane structure lipids? Draw each

Answer 40

Question 41

Lipid bilayer: Phospholipids, sphingolipids and cholesterol are virtually ________ in water But they are _________

Answer 41

insoluble amphipathic

Question 42

How do the structural lipids form the lipid bilayer?

Answer 42

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

Question 43

What model is used to describe the surface of the lipid membrane? Explain

Answer 43

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

Question 44

What are the lipid and protein components of the lipid bilayer?

Answer 44

Question 45

What are the lipids involved in signalling, both intracellularly and extracellularly? Name and describe all

Answer 45