Exam 3

Question 1

translation

Answer 1

information in an mRNA is translated into a protein

Question 2

necessary components for translation

Answer 2

1. mRNA with genetic code
2. ribosomes
3. transfer RNAs (tRNAS)

Question 3

genetic code

Answer 3

series of codons on an MRNA
* codon: sequence of 3 nucleotides

Question 4

codon function

Answer 4

• specifiy a particular amino acid
• signal where translation should start or step on mRNA
• necessary b/c mRNA have 5’ and 3’ untranslation regions which are not supposed to be translated

Question 5

characteristics of genetic code

Answer 5

• 64 codons
• universal
• redundant
• 64 codons and 20 AA
• 1 start and 1 stop codon

Question 6

ribosomes

Answer 6

enzyme complexes that translate the info in mRNAS into proteins
* made of 2 subunits
1. large ribosomal subunit
2. small ribosomal subunit
* each subunit is made of multiple ribosomal proteins and RNAs

Question 7

ribosome function

Answer 7

• small subunit - positions mRNA
• large subunit - peptide bond formation, * recognition of stop codon and protein release
• both bind tRNA
• enzymatic function - catalyze rxns (ribozymes)

Question 8

tRNA function

Answer 8

carry the amino acids to ribosome to be incorporated into a protein

Question 9

uncharged tRNA vs charged tRNA

Answer 9

uncharged: no AA
charged: AA

Question 10

3 Phases of Translation

Answer 10

1. initiation: assembly of mRNA, ribosome, and initiator tRNA
2. elongation: starts at start codon (met) and AAS are added until stop codon
3. termination: new protein is released from ribosome, ribosome disassembles

Question 11

Prokaryotic Initiation Steps

Answer 11

• mRNA has a 5’ ribosome binding sequence - complementary to rRNA in small ribosomal subunit
• initiator tRNA binds to start codon (AUG)
  large ribosomal subunit joins and initiation is complete

Question 12

Eukaryotic Initiation steps

Answer 12

1. Small ribosomal subunit + initiator tRNA binds to the mRNA 5’ cap
2. Complex scans mRNA until it finds the start codon
3. Large ribosomal subunit joins the complex and initiation is complete

Question 13

Ribosome tRNA Binding Sites

Answer 13

P site: where initiator tRNA binds
A site: where the next tRNA binds, carrying the next AA to be added to the protein
E site: where uncharged tRNAs are ejected

Question 14

translocation

Answer 14

movement of the ribosome down the length of the mRNA

Question 15

Translation Termination

Answer 15

• No tRNAS binds to the stop codon
• Release factor (a protein) binds to the stop codon
• Synthesized protein is released from the ribosome
• Ribosome complex falls apart

Question 16

Primary structure

Answer 16

sequence of AA in a protein

Question 17

secondary structure

Answer 17

folding of protein caused by interactions within peptide backbone
* h-bonding
* ex. alpha-helix, beta pleated sheets

Question 18

super secondary structure

Answer 18

forms when 𝛼-helices and 𝛽-pleated sheets combine in various ways to form motifs

Question 19

Tertiary Structure

Answer 19

the highest level of structure for a single protein
Stabilized by interactions between the R-groups of the amino acids

Question 20

stabilizing tertiary structures

Answer 20

• Electrostatic interactions: H-bonds and ionic bonds between R-groups
• Disulfide bridges: cysteine has a sulfhydryl (SH) group
• SH groups of cysteine can form covalent bonds called disulfide (S-S) bridges
• Disulfide bridges: cysteine has a sulfhydryl (SH) group
• SH groups of cysteine can form covalent bonds called disulfide (S-S) bridges
• Hydrophobic interactions

Question 21

domain

Answer 21

subunit on a protein with a specific function

Question 22

DNA binding domain (DMD)

Answer 22

any protein that directly binds to DNA needs a DNA binding domain

Question 23

transcriptional activation domain (TAD)

Answer 23

Activating transcription of a gene requires a transcriptional activation domain (TAD) to attract/interact w/ RNA polymerase

Question 24

Quaternary Structure

Answer 24

interaction of 2 or more proteins to form a multi-protein complex

Question 25

Chaperone proteins:

Answer 25

enzymes that help proteins fold/refold into the proper shape

Question 26

Epigenetic Modifications

Answer 26

modifications that change the expression of genes w/ out changing the DNA sequence of the gene Often change the chromatin structure of a gene

Question 27

What do epigenetic modifications change

Answer 27

how tightly DNA and histones bind to each other

Question 28

Euchromatin

Answer 28

DNA & histones are loosely associated and DNA very accessible to transcription factors/RNA pol. binding

Question 29

Heterochromatin

Answer 29

DNA & histones are tightly associated and DNA is not very accessible to transcription factors/RNA pol.

Question 30

Methyl group

Answer 30

physical barrier to binding of transcription factors (inhibits gene transcription)

Question 31

Hydrophobic Ligands

Answer 31

* Can diffuse across the plasma membrane * Bind to intracellular receptors (IRs) in the cytoplasm * IRs have an intracellular ligand binding domain which causes the IR to transduce a signal into the cell

Question 32

Hydrophilic Ligands

Answer 32

* Polar and can’t diffuse across the plasma membrane * Hydrophilic ligands must bind to membrane-bound receptors which have 3 protein domains 1. Extracellular ligand binding domain 2. Transmembrane domain (goes through the plasma membrane) 3. Intracellular signaling domain (transduces the signal)

Question 33

Agonists

Answer 33

mimic the action of ligands that would normally bind to the receptor (activate receptors)

Question 34

Antagonists

Answer 34

bind to but do NOT activate receptors Blocks other ligands from binding to receptor

Question 35

Embryonic development

Answer 35

gene-directed changes that occur after fertilization that lead to the formation of an organism

Question 36

Homeotic genes

Answer 36

genes critical for making sure anatomical structures develop in the correct location and correct number

Question 37

Morphogens

Answer 37

diffusible ligands (signaling molecules) that affect cell fate during development * gradients

Question 38

Central nervous system (CNS

Answer 38

consists of brain, spinal cord, and interneurons within the brain and spinal chord

Question 39

Peripheral nervous system (PNS)

Answer 39

consists of sensory neurons and motor neurons

Question 40

sensory neurons

Answer 40

carry info about body & environment to CNS

Question 41

interneurouns

Answer 41

provide a link between the sensory neurons, brain, and motor neurons

Question 42

Motor neurons (PNS):=

Answer 42

carry impulse from CNS to effectors (muscles, glands)

Question 43

Dendrites

Answer 43

receive signals (using receptors) and send electrical pulses (action potentials) to the cell body

Question 44

Axon:

Answer 44

conducts the action potential to the axon terminals (ends)

Question 44

cell body

Answer 44

has nucleus and other metabolic machinery, can decide whether or not to transmit action potential to axon

Question 45

Axon terminals:

Answer 45

transmit the signal through a synapse to the next cell