How Proteins are made
Nucleotide order is copied to RNA molecules and decoded to specify the order (sequence) of amino acids in a polypeptide chain that will fold to make a functional protein molecule |
DNA - RNA - Protein |
Transfer RNA
Charged tRNA: tRNA carrying an amino acid |
Small molecules carrying 70-90 nucleotides |
Has a self pairing structure (clover leaf structure) - 3' end of CCA is the amino acid binding site |
3 key roles: carries amino acids, associates with mRNA & interacts with ribosomes (APE) |
Genetic Code
When mRNA is scanned by a ribosome, it is always read 3 nucleotides (3 bases)/a codon at a time to avoid redundancy (multiple condons can be for the same amino acids) |
Start codon: AUG (code for methionine) - acts as initiation signal for translation |
Stop codon: UAA, UAG, UGA - directs ribosomes to end translation |
Redundancy + Wobble
Wobble rule: so long as the first 2 nucleotides pair up, the 3rd one can wobble (doesn’t need to be a perfect fit) |
Ex: CUC (leu) – GAG vs CUU (leu) – GAG |
Pairing of tRNA anticodon and mRNA codon starts by going towards the 5' end |
Membrane proteins
Transporter |
Moves ions and other molecules across the membrane |
Receptor |
Recieves signals from the environment |
Enzyme |
Catalyzes elemental reactions |
Anchor |
Attachment and maintain cell shape and structure |
Enzymes
+(delta)G: endergonic (need to put in energy for reaction, non-spontaneous reaction) |
-(delta)G: exergonic (reaction releases energy, spontaneous reaction) |
Metabolism: building/breaking down of carbon sources to harness or release energy – 2 types of reaction |
Catabolism: breaking down larger macromolecules (proteins, lipids) into their smaller sub-units (amino acids, fatty acids) |
Anabolism: building up reactions, uses atp from catabolism to use and build up larger molecules from smaller sub-units (proteins to nucleic acids_ |
- Enzymes decrease the amount of free energy required to turn reactants to products |
- substrate + active sites: weak noncovalent interactions, transient covalent bonds (always) |
|
|
Translation - Molecules needed
Messenger RNA (mRNA) |
Initiation factors |
Elongation factors |
Aminoacyl tRNA synthetases |
Binds specific amino acid to 3' end of uncharged tRNA |
Transfer RNA (tRNA) |
Ribosome (ribosomal RNA + ribosomal proteins) |
- Arranges order of charged tRNA molecules to match mRNA order
- Organizes mRNA transcript from transcription |
Cell Membrane
Membranes are made up of lipids (hydrophobic with hydrocarbon tails) - majorily made from phospholipids |
Phospholipids have a hydrophilic head and double hydrophobic tails that form a lipid bilayer |
Membrane fluidity is determined by the types of lipid that make up the membrane.
- Saturated fatty acids have linear tails = tighter/less space means less fluidity
- Unsaturated fatty acids have a kink = more space/less packed meaning more fluidity |
Cholesterol |
Cholesterol can increase or decrease membrane fluidity depending on the temperature. |
At normal cell temperature, the interaction of the rigid structure of cholesterol with the phospholipid fatty acid tails reduces the mobility of the phospholipids and the fluidity of the membrane. |
Transport avross the membrane
Diffusion - movement of solute molecules across membranes |
Osmosis - movement of solvent molecules across membranes; involves water |
- Hypertonic solution: More solutes outside than inside – water moves from inside to outside the cell (Cell shrinks) -Isotonic solution: Concentration of solutes is the same inside and outside the cell = no net movement of water -Hypotonic solution: More solutes inside the cell than outside, water moves inside the cell |
Facilitated Diffusion - involves net movement of solutes (ions, small molecules) down a concentration gradient until equilibrium is reached |
Primary Active Transport – uses energy from ATP hydrolysis to pump ions into or out of cells against the concentration gradient |
Secondary Active Transport – can drive the transport of molecules through a different transporter via the creation of an electrochemical gradient. In this example, the active transporter |
|
|
Initiation
How it starts |
Starts by initiation factors binding to 5' cap of mRNA |
Recruits smaller subunit of ribosome |
Other initiation factors bring tRNA charged with Methionine (always the starting amino acid) |
Initiation complex moves along mRNA until start codon AUG is found (P site) |
Large ribosomal subunit joins and binds to the complex |
Initiation factors are released and next charged tRNA is ready to join |
The process |
New charged tRNA joins on (from A site) next to the amino acid (coupled reaction) -> connects Met to the new amino acid (first peptide bond) |
Ribosome shifts onto next codon and (now uncharged) tRNA leaves the complex (from E site) to continue the process |
Process stops when stop codon (UAA, UAG, UGA) is found, tRNA keeps leaving from E site until the amino acids have deattached |
Elongation
Initiation process continues until required length is obtained for the polypeptide chain |
-requires elongation factors (carries GTP – hydrolyses gtp and releases energy) |
Termination
A protein release factor binds to the A site of the ribosome, causing the bond connected to the polypeptide of the tRNA to break |
Carboxyl terminus is created at the end of the polypeptide chain following the bond breakage |
Endomembrane system
Plasma membrane |
Regulates the passage of materials into and out of the cell |
Nuclear envelope |
Organizes/maintains nuclear content - Molecules move in/out of nuclear envelop using nuclear pores |
Endoplasmic reticulum |
Protein (rough) and lipid (smooth) synthesis and transport |
Golgi apparatus |
“Shipping and receiving center” Modify/sort proteins and lipids |
Lysosomes |
Digestive enzymes can help metabolize/breakdown proteins, nucleic acids, carbs |
|
Created By
Metadata
Comments
No comments yet. Add yours below!
Add a Comment
Related Cheat Sheets
More Cheat Sheets by vamsvams15