Gene Expression and Protein Synthesis (1) Flashcards
Exam 1
True or False:
The nucleus is the smallest organelle.
False:
The nucleus is the largest organelle
What is the function of the nucleus?
Stores genetic information
What is the function of the nucleolus?
formation of ribosomes (using RNA)
What is the nuclear envelope?
double membrane around the nucleus
What are nuclear pores?
regulate passage of substances
-hold membrane together
What is the nucleoplasm?
material in nucleus
What is chromatin?
- Diffuse DNA (some RNA)
- -prior to division –> converts to chromosome
What is a gene traditionally?
a segment of DNA that codes for a particular protein
- codes first for mRNA –> protein
- -TONS of PROTEINS
- -20,000 genes
What is the current definition of a gene?
An information-containing segment of DNA that codes for the production of a molecule of RNA that plays a role in synthesizing one or more proteins
Amino Acid sequence of a protein is determined by the ____ sequence in the DNA
nucleotide
How many separate human DNA molecules (chromosomes) are there?
How many pairs does that make and where do they come from?
- 46 separate
- 23 pairs
- –set from each parent
Genome Definition
all the genes in 23 pairs
What is genomics?
study of the whole genome and how its genes and noncoding DNA interact to affect structure and function of the whole organism
A single gene can code for ___ ____ proteins
- many
- different
The function and regulation of most genes is ___
unknown
True or False:
All humans are at least 99.9% genetically identical
True
Genetic Code Definition
a system that enables these four nucleotides to code for amino acid sequences of all proteins
Proteome Definition
Specific proteins expressed in a given cell at a particular time
True or False:
DNA language is the same as protein language
false
DNA language is different than protein language
Codon Definition
three letter (nucleotide) unit of mRNA
- -codes for single amino acids
- -61 triplets (3 are stop codons)
What is a stop codons and a start codon?
stop codons: signal “end of message”
start codon: (methionine [AUG]) begins the amino acid sequence
From ___ to ___ to ___
DNA
RNA
Protein
Molecular Genetics Definition
how genes control the building of specific proteins
Gene Expression Definition
protein codes for functions in the cell
What are the two steps of gene expression?
- Transcription
2. Translation
Cells differ in structure and function because….
- different proteins do different jobs
- only certain genes are expressed
Gene expression is controlled in the ___ which leads to…
- Cell
- specialization of cells in tissue
What are the three types of RNA?
- Messenger RNA (mRNA) (pre-mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
Which RNA are produced in the nucleus?
mRNA and tRNA
Which RNA are produced in the nucleolus?
rRNA
What is the function of mRNA?
- transcription
- translation
What is the function of tRNA?
-transfers amino acids to ribosomes
What is the function of rRNA?
component of ribosome that joins the large and small subunits
What is made when a gene is activated during protein synthesis?
mRNA
What is the process of protein synthesis?
DNA –> mRNA –> Protein
- Transcription: DNA –>mRNA
- Translation mRNA –> Protien
Where does transcription take place?
nucleus
Where does translation take place?
cytoplasm
True or False:
Transcription is the creation of mRNA from DNA
True
Introns…
stay inside the nucleus
Exons…
exit the nucleus
Alternative Splicing Definition
variations in the way axons are spliced
–allows for a variety of proteins to be made from one gene
Ribosomes are located…
- outside the nucleus
- rough ER
- nuclear envelope
What is the function of ribosomes?
- read mRNA- build the protein
- facilitate pairings between codons and anticodons of tRNA
What happens at the p-binding site?
amino acid chain is growing
what happens at the a-binding site?
newly arrived tRNA comes in
what happens at the e-binding site?
exit
What are the three steps of translation?
- initiation
- elongation
- termination
What happens during initiation?
- A small ribosomal subunit binds to mRNA; an initiator tRNA pairs with the mRNA start codon: AUG
- The large ribosomal subunit completes the ribosome. Initiator tRNA occupies the P site. The A site is ready for the next tRNA
What happens during elongation?
-ribosome slides to read next codon
-releases initiator tRNA (now at E site)
-next tRNA (anticodon) binds at the A site
-peptide bond form between growing amino acid chain
(process repeats until stop codon reached)
What happens during termination?
- The ribosome comes to a stop codon on the mRNA. A release factor binds to the site
- The release factor hydrolyzes the bond between the last tRNA at the P site and the polypeptide, releasing them. The ribosomal subunit dissociate.
What happens during translation?
- some proteins packaged others exported
- proteins headed for secretion are made on ribosomes on the rough ER
- –newly made protein is threaded into rough ER
- —–modified and packaged into a transport vesicle
Chaperone Protein Definition
- old proteins that are designed to help primary structure to fold into its proper form
- prevents improper association
What do stress proteins or heat-shocked proteins do?
-help damaged proteins fold back to functional form
How does protein processing and secretion work?
To work- primary structure must fold into precise secondary/ tertiary structures
What happens when translation is finished?
primary structure and amino acid sequence is formed
How are proteins to be used in the cytosol made?
Made by free ribosomes in cytosol
Where are proteins destined for packaging into lysosome for secretion from the cell assembled?
Assembled in the rough ER/ Golgi complex
What is going on inside the ER?
a complex system of channels (cisternae) enclosed by a membrane
Rough ER Definition
Parallel, flattened sacs
- -continuous with outer membrane of the nuclear envelope
- -studded with ribosomes
- —produces phospholipids/proteins that go to the cell membrane
What does the rough ER form?
forms transport vesicles
Where do transport vesicles go for further modification?
- golgi complex
- -cell membrane
What is the Golgi apparatus?
system of cisternae (“transfer station”)
What does the Golgi apparatus synthesize?
- carbs
- finishing touches on proteins
Where are vesicles sorted and repackaged?
Golgi apparatus
How does the Golgi apparatus modify newly synthesized proteins?
Receives newly synthesized proteins from rough ER
–modifies via splicing (cutting amino acid sequence) and adding/removing sugars
Where do proteins assemble?
on surface of ER
How are proteins assembled?
-threaded through a pore in the ER membrane not cisterna
What happens in post-transitional modification?
- remove amino acid segments
- fold protein
- stabilized protein
- -disulfide bonds
- add carbohydrates
What happens when the rough ER is finished with protein processing?
a transport vesicle would bubble off of surface of rough ER and carry the protein to the Golgi complex
What happens when the protein is transported to the Golgi apparatus?
further modification go protein and carbohydrates added
After proteins are done modifying at the Golgi apparatus, what happens?
proteins bud off into cytoplasm
–some then become lysosomes or migrate to the cell membrane
Genes can be turned __ and __
Some cells can even turn some genes ____ ____
- on
- off
- permanently off
True or false:
cells can turn genes on only when needed
True
this can be controlled by chemical messengers such as hormones
What are enzymes?
easy definition and official definition
- protein catalyst
- biological catalyst that enable biochemical reactions to occur rapidly at normal body temperature
What can enzymes do?
- increase the rate of a reaction
- reusable- not changed by reaction
- doesn’t change the nature of the reaction (could occur, super slow)
- lower the activation energy
- enzymes work fast
Activation energy definition
energy required for a reaction to occur
what happens with activation energy?
- orient substrate molecules in a precise way
- rearrange the electrons in the substrate
- strain the bond of substrate (force closer together, force reaction)
Why must enzymes come into contact with reactants (substrates)?
1) Substrate binds to enzyme
2) From enzyme - substrate complex
3) Break down –> products/enzyme
What happens in the first step of enzymatic reactions?
- Substrate becomes bound to the enzyme
- -binds on active site (region where substrate binds to)
What happens in the second step of enzymatic reactions?
- Enzyme-substrate complex
lock-and-key and Induced fit
What are the two models of the enzyme substrate complex?
- Lock-and-key –> enzyme substrate fit specifically
2. Induced fit –> shape change
What happens in the third step of enzymatic reactions?
- Breaks down to release products and enzyme
- -bond broken by hydrolysis = reaction products
How is the concentration of enzymes measured?
Via rate of conversion of substrate to product- rate of enzyme activity
What is the rate of enzyme activity?
how quickly a product is produced
What can effect the rate of enzyme activity (rate at which substrates are converted to products)
- temperature and pH
- concentration of cofactor/coenzymes
- concentration of enzyme itself
- concentration of substrate
- influence of products on the ability of others to take place
What specifically does temperature and pH do to enzyme activity?
- Can alter the ability of enzyme to bind to substrate
- enzymes vary in optimum pH
- Temperature optimum for human enzymes (37 degrees C)
Some metal ions function as ____ for enzymes
cofactors
bind to enzyme –> change the conformation
Some organic molecules function as ____ - directly participate as a substrate in a chemical reaction
coenzymes
What do transfer stations do?
Move molecules around and detect transporters
What does the mitochondria contain and what is it surrounded by?
- Organelles specialized for synthesizing ATP
- Surrounded by a double membrane (inner membrane - folds and spaces and matrix- contains ribosomes, enzymes for ATP synthesis, and mitochondrial DNA
What is most important for energy transfer molecule?
Adenosine triphosphate (ATP)
Hydrolysis of ATP is catalyzed by ____
Adenosine triphosphatases (ATPases)
Phosphorylation Definition and Equation
-Addition of a phosphate group to a molecule
ATP + H20 —(ATPase—> ADP + Pi + Energy
What does instability do in the use and production of ATP?
instability is the effective energy carrier
What does glycolysis do and where does it take place?
- splits glucose into pyruvate
- happens in the cytosol
What is Aerobic Respiration apart of and where does it take place?
- Citric Acid Cycle
- Electron Transport Chain
