chapter 13

Question 1

Identify the general structure of an amino acid at pH 7 + the chemical properties found among amino acids.

Answer 1

amino group to the left with a side chain (R) lower middle connected to center C and then carboxyl group connect to the right of the center C

Question 2

four levels of protein structure

Answer 2

primary
secondary
tertiary
quaternary

Question 3

how do amino acids differ

Answer 3

by the R group/side chains (properties on them are determines by this)

Question 4

three types of side chains

Answer 4

1. charged acidic (-) or charged basic (+)
2. polar/ neutral ( uncharged includes an oxygen)
3. nonpolar (Carbon and hydrogens H and aromatic)

Question 5

peptide bond forms a backbone with… (3 things)

Answer 5

1. R-group orientation - side chains extend out + can interact with eachother / water
2. directionality - end with free amino group and free carboxyl goup
3. flexibility - single bonds on either side can rotate

Question 6

N- terminus

Answer 6

free amino group

Question 7

C - terminus

Answer 7

free carboxyl group thats encoded by 3’ end of mRNA

Question 8

how are polypeptide sequences written?

Answer 8

N- terminus to the left which is encoded by 5’ end of mRNA

Question 9

primary structure of protein

Answer 9

sequence of amino acids

Question 10

secondary strucutre of proteins

Answer 10

1st level of folding of a polypeptide chain: regular repeating shapes as alpha helices or beta sheets

Question 11

tertiary structure of proteins

Answer 11

3D shapes found as alpha helices or beta sheets

Question 12

quaternary

Answer 12

3D shape of multisubunit protein complex

Question 13

In sickle cell anemia, the 6th amino acid of the beta-globin
polypeptide is changed from glutamic acid (Glu, G) to valine
(Val, V). This is a change in which level of protein structure?

Answer 13

primary

Question 14

what are the rules used by cells to interpret nucleic acid sequences to synthesize amino acid sequences

Answer 14

genetic code

Question 15

What is the most number of codons that code for a single amino acid?

Answer 15

6

Question 16

how many nucleotides = 1 codon

Answer 16

3 nucleotides which code for one amino acid

Question 17

amino acids are encoded by ____ codons

Answer 17

multiple

Question 18

unambigous means…

Answer 18

each codon has only a single “meaning”

Question 19

do all organisms essentially use the same code if so what does this reflect

Answer 19

yes and reflects existence of a universal common ancestor of all life … “universal”

Question 20

punctuation means

Answer 20

it includes a start and 3 stop codons (for translation)

Question 21

tRNAs

Answer 21

adaptor molecule that brings in correct amino acid to each codon on the mRNA for ribosome to assemble

secondary structure is a cloverleaf w. 3 stem loops

1 stem loop = anticodon
an aminoacyl-tRNA (charged) has amino acid attached to its 3’ end

Question 22

aminoacyl-tRNA synthetases

Answer 22

these enzymes attach correct amino acids to tRNAs (to each adapter molecule) using ATP to drive reaction

each of these are specific for 1 amino acid

products are tRNAs (charged)

Question 23

ribosomes

Answer 23

contain rRNA + proteins

read mRNAS 1 codon at a time
- match each codon in mRNA with the correct tRNA
- catalyze the formation of peptide bonds between amino acids brought in by the charged tRNAs, leading to protein synthesis.

Question 24

mRNAs

Answer 24

carries info for assembling sequence of amino acids into polypeptide
- carries copy of gene sequence to protein synthesis machinery

produced by transcription of DNA sequence of a gene (in eukaryotes, it is assembled by splicing of the pre-mRNA)

have an 5’ untranslated region follow by coding sequence w. a start codon follow by coding codons then by a stop codon and followed by 3’ untranslated region

Question 25

structure of tRNA

Answer 25

secondary is cloverleaf tertiary is L shapes

Question 26

where do the amino acids used to make proteins come from?

Answer 26

synthesized by enzymes and food we eat

Question 27

stages of translation (3)

Answer 27

1. initiation 2. elongation 3. termination

Question 28

initiation stage of translation

Answer 28

The ribosomal subunits, mRNA, and the 1st charged tRNA assemble on the start codon (AUG)

Question 29

elongation

Answer 29

1. The ribosome slides along the mRNA 2. Matches aminoacyl-tRNAs with codons 3. catalyzes peptide bond formation between amino acids. This step is repeated for each codon.

Question 30

termination

Answer 30

A stop codon is reached and the polypeptide is released from the ribosome.

Question 31

The hemoglobin protein is normally found as a globular- shaped tetramer (four subunits joined together). In sickle cell anemia, the 6th amino acid of the beta-globin polypeptide is changed from glutamic acid to valine. This single amino acid change causes hemoglobin to clump into rods. What is the highest level of protein structure that is changed by the sickle cell anemia mutation?

Answer 31

quaternary

Question 32

What types of interactions can be involved in holding together the tertiary and quaternary levels of protein structure?

Answer 32

hydrogen bonds, covalent (S-S) bonds, ionic bonds, hydrophobic interactions

Question 33

The genetic code is the set of rules used by the cell to

Answer 33

Translate RNA sequences into protein sequences - specifies which amino acid is encoded by each three “letters” of RNA sequence

Question 34

How is the information in the genetic code table stored in the cell?

Answer 34

two key components of translation: tRNAs + the aminoacyl-tRNA synthetases tRNAs’ anticodons recognize the codons of the mRNA. * The aminoacyl-tRNA synthetases attach the correct amino acids to each tRNA. Together with the ribosome, they enable the correct amino acid to be matched to each mRNA codon during translation

Question 35

how do you identify termination

Answer 35

release factor protein bound to the stop codon on the mRNA, so translation is about to end and everything will be released.