Transcript PROTEIN SYNTHESIS - Brandywine Heights Area School District

Protein Synthesis
Honors Biology
I. PROTEIN SYNTHESIS
• Process of using DNA to make protein
• Function of protein in body
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Enzymes
Immunity
Communication between cells
Build muscles
Express genes (skin color, eye color, etc…)
II. Review of DNA Structure
The discovery of DNA and modern research
has allowed us to know the following about the
structure of DNA:
1. Nucleotides are monomers of nucleic acid
2. Nucleotides consist of:
– Deoxyribose (5 carbon sugar)
– Phosphate
– Nitrogen base (A,T,C,G)
3. Double helical structure
- Backbone = phosphate and sugar
- Rungs – nitrogen bases
4. A and G – purines (double rings)
C and T – pyrmidines (single rings)
DNA
DNA
BASES
III. FUNCTION OF DNA
• Stores genetic information
• Contains recipe to make any and all
protein your body needs to function
everyday
IV. Helpers for Protein
Synthesis
1. RNA - ribonucleic acid
– Acts as a messenger between DNA and
ribosomes
Structure of RNA:
– 5 carbon sugar – ribose
– phosphate
– nitrogen bases (A, U, C, G) – Uracil replaces
Thymine in RNA
– Single strand of nucleotides
3 types of RNA
1.mRNA – messenger RNA
decodes DNA and relays “recipe” to the
ribosome
2.tRNA – transfer RNA
Transfers a specific amino acid to the ribosome
to be used in protein synthesis
3. rRNA – part of the ribosome
Types of RNA
Other need to know vocab for
protein synthesis
1. Codon – 3 nitrogen bases that code for an
amino acid.
2. Anticodon – 3 nitrogen bases of tRNA
3. RNA polymerase – an enzyme that matches
up compleentary bases of mRNA to bases
of DNA (A-U, C-G)
4. Promoter – “start” signal. Signals RNA
polymerase to begin matching up
complementary bases
V. Protein Synthesis
3 Stages of Protein Synthesis:
1. Transcription - “write recipe down”
2. Translation - “put recipe together”
3. Elongation - “glue” amino acids
together to form protein
SUMMARY
1. Transcription
• Process where mRNA copies down the
“recipe” to make a protein
• Transcribe = “to write down”
• Occurs in nucleus of cell
Steps of Transcription
1. Helicase unwinds and unzips DNA
(only in area of the recipe) creating 2
strands. An active strand and
“dummy”strand of DNA.
2.Active strand is the one to be used to
make the protein (the template)
3. Special sequence of DNA is
recognized by RNA polymerase as the
“start signal” (promoter)
Steps of transcription cont…
4. RNA polymerase “reads” the DNA codons and
matches up complementary bases between DNA
and mRNA (A-U, C-G), using DNA as a template
5. RNA polymerase continues to move along the
area of the DNA with the recipe, matching up
complementary bases
6. When RNA polymerase hits the “stop codon”
mRNA drops off DNA
7. At this point mRNA has “copied” the recipe to
make a specific protein.
8. DNA winds back up and mRNA gets modified
before leaving the nucleus
TRANSCRIPTION
mRNA modification
• While still in the nucleus, mRNA gets modified.
• mRNA consists of exons and introns
• An enzyme comes along and splices out the introns
(pieces of DNA) that is not part of the recipe
needed for the protein.
• Exons are then spliced together to create the “real
recipe” (functional mRNA) for the protein your body
needs
• Exons are then capped and tailed for protection
and then leave the nucleus via nuclear pores.
EXONS AND INTRONS
WHY COPY DNA????
• DNA is too large to leave the nucleus,
so it needs a messenger to bring
genetic information to the ribosome in
the cytoplasm.
• This messenger is the mRNA
2. TRANSLATION
• Occurs in the cytoplasm (at ribosome)
• Process of decoding mRNA into protein
• Code being translated from language of
nucleic acids into polypeptide
STEPS OF TRANSLATION
1. mRNA bonds to a ribosome at the “start
codon”
2. The ribosome reads each codon of mRNA
and signals tRNA (complementary nitrogen
bases which are carrying a specific amino acid.
(Also called an anticodon)
3. Complementary tRNA matches up with
mRNA codon, and drops off a specific amino
acid.
IN CYTOPLASM
Translation cont….
4. The ribosome continues to move along the mRNA
“reading” the mRNA codons and signaling tRNA to
bring amino acids to the ribosome.
5. Each time a specific amino acid is dropped off, it
bonds to the previous amino acid.
6.This continues until the ribosome hits the “stop”
codon.
7. At this point, the mRNA breaks off and returns to
the nucleus where it is disassembled to be used
again.
8. All that is left is a string of amino acids in a specific
order. This specific order is what determines the
name and type of protein that was just made.
TRANSLATION ON
RIBOSOME
TRANSLATION
3. ELONGATION
• The string of amino acids is bonded
together (during the process of
translation) to create the protein that
your body needs.
TRANSLATION
Other information:
• This process is very fast, less than a minute
to make a protein.
• The newly synthesized polypeptide may coil
and fold int 3D shape (tertiary structure)
and/or several may bond together forming a
quaternary structure.
• Changes in the sequence o DNA can cause
a change in amino acid sequence, which can
cause a different or wrong protein to be
made.
VI. MUTATION
• What will occur if the amino acids are
not in the right order?
(won’t make the right protein with the right
function. This is a mutation)
• What happens if you did not eat enough
protein in your diet and the tRNA could
not pick up a specific amino acid
needed to make the particular
protein???
• What happens if you did not eat enough
protein in your diet and the tRNA could not
pick up a specific amino acid needed to
make the particular protein???
• If you don’t have the correct amino acid, it
can not be put in the right order during
translation, and this can cause the process
to make a different protein with a different
function.
• Mutations can be caused by
– DNA replication error
– Mutagens in the environment
VII. GENE EXPRESSION /
REGULATION
• Genes are expressed when they are
“turned on” – meaning that it is being
transcribed (goes through protein
synthesis) into a protein.
• By regulating gene expression, cells are
able to control which part of genome will
be expressed.
VIII. GENE EXPRESSION IN
DEVELOPMENT
• Every cell in developing zygote contains
all of the organism’s genes, only small
number of genes expressed
• Certain genes are turned on and off as
proteins are needed at different times
during the organism’s life
Development
• As organisms grow from zygote the cells
differentiate
• Differentiate - cells develop into different
types of cells and tissue.
• Ex. Nervous cells, skin cells, muscle, etc…
• The development of form in an organisms is
called morphogenesis.
Morphogenesis
• Homeotic genes regulate where certain
anatomical structures go.
• Ex. Appendages, organs, etc…
• Homeotic gene is the master genes of
development and determine how the body will
be organized
• These genes regulate development by
switching genes on and off, which controls
the rate of cell division in certain areas of the
developing organism, this results in specific
patterns of structural development
IX. Gene Expression and
Cancer
• Proto-oncogenes - regulate cell growth, cell
division and the ability of cells to stick
together.
• Ensure that mitosis runs smoothly
• A mutation that leads to over expression of
proteins that control mitosis can effect the cell
cycle and lead to cancer.
• Some genes act as Tumor suppressor genes
that prevent cell division from occurring too
often.
• In cancer tumor suppression genes are
damaged