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Transcript
Proteins
Proteins Review
Proteins are composed of C, H, O, N and sometimes S
Proteins are made of amino acids
Proteins are held together by peptide bonds (covalent bonds
between amino acids)
Proteins are coded for by the sequence of DNA nucleotides
Proteins are the building blocks of all materials
Proteins can be enzymes (catalysts for reactions)
Proteins Pre-Production: Understanding DNA
and RNA
DNA (deoxyribonucleic acid)
RNA (ribonucleic acid)
• Double helix strand of
nucleotides
• Bases A, T, C, G
• Contained in the nucleus
• Deoxyribose sugar
• Single strand of nucleotides
• Bases A, U, C, G
• RNA does not have thymine, it has
uracil
• Several types in cell
• Ribose sugar
Proteins Pre-Production: Understanding DNA
and RNA
DNA
RNA
Proteins Pre-Production: Understanding DNA
and RNA
RNA: types
RNA: Types
• mRNA: messenger RNA, carries
code of DNA as codons to
ribosomes
• tRNA: transfer RNA, brings
amino acids and matches it to
codons using anti-codons
• mRNA
• tRNA
Checkpoint #1
1. Create a Venn diagram for DNA and RNA
2. You already know how DNA replication occurs. With that in mind,
what predictions could you make about how mRNA is formed from
DNA? In other words, how does the code of DNA become a strand
or RNA?
3. Name and describe two types of RNA involved in protein synthesis?
4. Using your macromolecule notes, give examples and functions of at
least three proteins.
Production: Transcription
• RNA molecules are made by copying part of the nucleotide sequence
• RNA polymerase – enzyme that helps match complementary RNA
nucleotides to DNA nucleotides
• During transcription, RNA polymerase splits the DNA and matches
complementary nucleotides to form a strand of mRNA (messenger
RNA).
Production: Transcription
• What do you notice about the DNA to RNA base pairs?
Production: Transcription
• Instead of Thymine, RNA has Uracil.
•A–U
• C–G
Production: Transcription
• mRNA forms a “language” to become protein. Three mRNA
nucleotides together from a codon and that will be used for
translation
• UCGCACGGUUUC  UCG – CAC – GGU – UUC (Three Codons)
Production: Transcription
• Each codon represents a specific amino acid
• There are 20 amino acids
• What would the codon AUG stand for?
• What do you notice is different about
this codon?
Production: Translation
• During translation the cell uses information from messenger RNA to
produce proteins.
• The ribosome moves along the mRNA strand and matches tRNA
(transfer RNA) anticodons to the codons of the mRNA
• Each tRNA is carrying the specific amino acid coded for by the mRNA
• The ribosomes assists with forming peptide bonds between the
amino acids so a long chain (polypeptide) is formed
Production: Translation
Further resources
• Listen to Bozeman explain it!
• https://www.youtube.com/watch?v=h3b9ArupXZg
• Text page reference: Page 300-306
• Short animation: http://www.dnalc.org/resources/3d/12transcription-basic.html
Checkpoint #2
1.
2.
3.
4.
5.
What happens during transcription?
What happens during translation?
What is the codon and anticodon?
What roles do mRNA and tRNA play in protein synthesis?
Using the genetic code, identify amino acids that have the following
messenger RNA strand codes: UGGCAGUGC
6. Challenge: determine the amino acid sequence coded for by the
DNA strand AATTCGGCTACG
Post-Production
• Proteins are long chains of amino acids held together by peptide
bonds. They form polypeptide chains.
• Proteins have 4 levels of structure
1. Primary Structure: sequence of amino acids
2. Secondary Structure: hydrogen bonding twists strand into a helix
3. Tertiary Structure: folding of the helix
4. Quaternary Structure: individual peptides are linked to one another
Post-Production
• Protein Folding
Protein Types
• Structural – keratin (hair, nails)
• Movement – actin and myosin in muscles
• Defense – antibodies in bloodstream, venom
• Storage – albumin in egg whites nourish an embryo
• Signaling – insulin promotes glucose uptake
• Catalyzing reactions – amylase in saliva digests carbohydrates
Structural proteins
Proteins: Enzymes
• Enzymes
• Make it easier for reactions to occur
• Act as catalysts to speed up a reaction
• They lower the activation energy (energy necessary for the rxn. to occur)
• Lock and Key Model
• Makes enzymes only work for specific reaction
• Important in controlling reactions of the body
Ex.: amylase, catalase, lactase
• “Enzymes are proteins that end in –ase”
Enzyme Structure – Lock and Key
Proteins: Enzymes
• Insulin
Denaturing Proteins
• Denature: when the shape of the protein gets permanently
changed
• Enzyme can’t function any longer
• Caused by: change in pH or temp
• Cold = usually slows enzymes down
• Hot = denatures enzymes
• Too acidic or basic = usually denatures enzymes
*Important to maintain homeostasis!
Denaturing Proteins
Checkpoint #3
1. If a codon changed from UUU to UUC, what effect would that have
on the overall protein?
2. Explain the importance of the proteins hemoglobin and insulin.
3. Why do you think it is important for enzymes to function with a lock
and key model?
4. A child goes to the doctor with an extremely high fever. Explain why
the doctor is very concerned and what might he/she do for
treatment.
5. Outline the four levels of structure for proteins.