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Bio 1010U - Module 1 pt.2 : Trans, Organi,+ Enzyme Cheat Sheet by

Study guide for Translation, Cell/Membrane Organization and Enzymes+Metabolism

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

Moves ions and other molecules across the membrane
Recieves signals from the enviro­nment
Catalyzes elemental reactions
Attachment and maintain cell shape and structure


+(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 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


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


Initiation process continues until required length is obtained for the polype­ptide chain
-requires elongation factors (carries GTP – hydrolyses gtp and releases energy)


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
Digestive enzymes can help metabo­liz­e/b­rea­kdown proteins, nucleic acids, carbs


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