Studied by 10 people
DNA Polymerase Functions?
-Reads template strands of parent DNA
-Adds new nucleotides to growing DNA strand
-Is self-correcting; can proofread and correct mistakes
What are the protein machines that replicate DNA?
-DNA polymerase | reads template strand and adds new nucleotides
-Primase | Synthesizes RNA primer
-Helicase | opens DNA double helix
-Single-Stranded Binding Protein | prevents reformation of base pairing prematurely
What are Mutations?
Damage to DNA
-The only source of new genes
-Caused by errors in DNA replication or accidental damage
-May alter or inhibit DNA replication or Protein Synthesis
What are the steps to Excision Repair?
-Excision | various enzymes cut out the damaged portion of the DNA
-Re-Synthesis | DNA polymerase remakes the DNA based on a healthy strand
-Ligation | DNA ligase - connects a newly made portion of the strand to the rest of the DNA strands; seals it up
Where is DNA located?
The majority of DNA is located in the Nucleus, but small amounts are found in the mitochondria and Chloroplasts.
How is information stored in DNA molecules?
information is stored in the sequence of Nucleotides in DNA
What are Chromosomes made of?
-Chromosomes are made of chromatin
-Chromatin is made of DNA and proteins
What direction does DNA polymerase write?
5’ to 3’
Protein Synthesis Steps
-Replication (DNA)
-Transcription (RNA)
-Translation (PROTEIN)
What is mRNA?
Messenger RNA
-Directs the synthesis of Proteins
Where does Transcription occur?
In the Nucleus (sometimes in Mitochondria and chloroplasts)
Where does Translation occur?
In the cytosol (sometimes in Mitochondria and chloroplasts)
What are the types of RNA synthesized and what happens after they are synthesized?
-mRNA (messenger RNA) | carries the message of how to make protein; processed in nucleus prior to export
-tRNA (transfer RNA) | Exported from Nucleus to cytosol
-rRNA (ribosomal RNA) | Exported from Nucleus to cytosol, forms part of ribosome
various others
How is RNA polymerase different from DNA polymerase?
-does not require a primer
-does not proofread
-has a far greater error rate
-performs multiple activities
*Opens DNA helix
*Adds RNA nucleotides
*Closes DNA helix
*Makes a single copy of RNA
where does RNA polymerase bind to the DNA at?
The promoter sites
How is mature mRNA formed?
-primary mRNA capped on 5’ end w/nucleotide
-Polyadenylation is added to 3’ end
-the Primary mRNA undergoes splicing
what is an Exon?
protein coding region shorter than intron
what is an Intron?
Non-coding region
What is a spliceosome?
catalyst for splicing reactions
What are ribozymes?
Catalytic RNA molecules
What is a codon?
sequence of 3 mRNA nucleotide bases
What is the Start codon?
AUG - Methionine amino acid
What is the Stop codon?
UAA, UAG, UGA
What makes up ribosomes?
RNA + Protein - 2 subunits
What happens once translation is completed?
-Ribosomal subunits separate
-Polypeptide Release
-mRNA degraded | so that mRNA will not bind to another ribosome and make more protein
What are Post Translational Modifications (PLMs)?
The process required for a polypeptide to become a fully functional protein
What is a Gene?
A unit of heredity containing the instructions that dictate the characteristics or phenotype of an organism
How is gene Expression determined?
Gene expression is primarily controlled at the level of transcription, largely as a result of binding of proteins to specific sites on DNA
How is Gene Expression Regulated?
DNA>RNA>Protein
-Cell Type
-Developmental Stage
-Environment
Where is Gene Regulation shut down at?
Transcriptional control
What are Operons?
Cluster of genes transcribes as single mRNA common in bacteria
What does the membrane surround in the cell?
-the entire cell
-surrounding organelles (nucleus, lysosome, and ER)
-Inside certain organelles (Mitochondria and Chloroplast)
What are the major functions of membranes?
-Barriers | regulates what goes in and out of the cell
-Cell Signaling | passes information about environment or other cells
-Energy Metabolism | important proteins inside the membrane that aids in ATP synthesis inside the mitochondria.
What is the Fluid Mosaic Model?
The idea that the phospholipid bilayer is covered in proteins discovered by Singer and Nicholson in 1972
What are the 3 most common lipids?
-Phospholipid | Most abundant lipid
-Sterols | very common in animal cells (Chlesterol)
-Glycolipids | sugar attached to a hydrophilic head
What is Membrane fluidity?
Movement of lipids in the bilayer
-Rotating (Most common)
-Exchanging with adjacent lipids
-Flip flop between bilayer (Rarest)
What increases Membrane fluidity?
-being an unsaturated chain (Bent)
-Being a shorter chain
-no cholesterol
-Increase in temperature
What decreases Membrane fluidity?
-Being a saturated chain (non bent)
-Being a longer chain'
-Having cholesterol
-Decrease in temperature
What are the important membrane proteins?
-Transporters and Channels | allow passage of larger molecules across membrane
-Anchors | Keep cells together
-Receptors | receive messages, generates intracellular responses
-Enzymes
What are porins?
Very large transmembrane channels formed by Beta sheets.
What are Aquaporins?
Channel within membrane that can be formed by alpha helices
Is the inside of channels hydrophobic or hydrophilic?
hydrophilic
What two carbohydrates are membrane proteins?
-Glycoproteins | short sugar chains attached to protein
-Proteoglycans | proteins with long chain polysaccharides attached
What are the functions of carbohydrates that are membrane proteins?
-Protection
-Identification (blood types)
-Adhesion
What is a Thylakoid membrane?
A membrane with photosynthetic pigments that absorb light
What happens if you bleach the membrane of a cell?
Proteins move within the membrane to put it back to normal
How does passive transport work in the membrane?
passive transport is driven by diffusion because of the electrochemical gradient (Membrane potential + Concentration gradient)
What are the two major classes of Membrane transport proteins?
Channels - only passive
Transporters - passive & active
What are gap junctions?
two channel proteins that allow transport between two cells
What are three examples of ion channels?
Voltage-gated channel | Membrane potential (electrical charge builds up causing it to open or close)
Ligand-gated channel | ligand binding (something binds to the channel causing it to open or close)
Mechanically gated/stress-activated channel | Mechanical stress, pressure, force, etc. cause the channel to open
What is the Patch-Clamp experiment?
heating a glass pipette and stretching it to receive a very fine point and filled with solution in order to remove a patch of membrane from the cell
What is membrane potential?
result of unequal distribution of ions across the membrane (produces electrical signal when ions cross)
What are the three active transport pumps?
Gradient-Driven Pump | Concentration gradient as source of energy
ATP-Driven Pump | ATP provides energy to transport ions
Light-Driven Pump | uses Retinal pigment to change shape of protein (mainly in plants and bacteria)
Note
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