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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
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DNA - RNA - Protein
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Charged tRNA: tRNA carrying an amino acid
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Small molecules carrying 70-90 nucleotides
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Has a self pairing structure (clover leaf structure) - 3' end of CCA is the amino acid binding site
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3 key roles: carries amino acids, associates with mRNA & interacts with ribosomes (APE)
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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)
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Start codon: AUG (code for methionine) - acts as initiation signal for translation
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Stop codon: UAA, UAG, UGA - directs ribosomes to end translation
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Wobble rule: so long as the first 2 nucleotides pair up, the 3rd one can wobble (doesn’t need to be a perfect fit)
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Ex: CUC (leu) – GAG vs CUU (leu) – GAG
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Pairing of tRNA anticodon and mRNA codon starts by going towards the 5' end
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Transporter
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Moves ions and other molecules across the membrane
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Receptor
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Recieves signals from the environment
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Enzyme
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Catalyzes elemental reactions
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Anchor
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Attachment and maintain cell shape and structure
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+(delta)G: endergonic (need to put in energy for reaction, non-spontaneous reaction)
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-(delta)G: exergonic (reaction releases energy, spontaneous reaction)
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Metabolism: building/breaking down of carbon sources to harness or release energy – 2 types of reaction
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Catabolism: breaking down larger macromolecules (proteins, lipids) into their smaller sub-units (amino acids, fatty acids)
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Anabolism: building up reactions, uses atp from catabolism to use and build up larger molecules from smaller sub-units (proteins to nucleic acids_
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- Enzymes decrease the amount of free energy required to turn reactants to products
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- substrate + active sites: weak noncovalent interactions, transient covalent bonds (always)
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Messenger RNA (mRNA)
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Initiation factors
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Elongation factors
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Aminoacyl tRNA synthetases
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Binds specific amino acid to 3' end of uncharged tRNA
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Transfer RNA (tRNA)
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Ribosome (ribosomal RNA + ribosomal proteins)
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- Arranges order of charged tRNA molecules to match mRNA order
- Organizes mRNA transcript from transcription |
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Membranes are made up of lipids (hydrophobic with hydrocarbon tails) - majorily made from phospholipids
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Phospholipids have a hydrophilic head and double hydrophobic tails that form a lipid bilayer
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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 |
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Cholesterol
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Cholesterol can increase or decrease membrane fluidity depending on the temperature.
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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.
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Diffusion - movement of solute molecules across membranes
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Osmosis - movement of solvent molecules across membranes; involves water
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- 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
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Facilitated Diffusion - involves net movement of solutes (ions, small molecules) down a concentration gradient until equilibrium is reached
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Primary Active Transport – uses energy from ATP hydrolysis to pump ions into or out of cells against the concentration gradient
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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
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How it starts
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Starts by initiation factors binding to 5' cap of mRNA
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Recruits smaller subunit of ribosome
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Other initiation factors bring tRNA charged with Methionine (always the starting amino acid)
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Initiation complex moves along mRNA until start codon AUG is found (P site)
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Large ribosomal subunit joins and binds to the complex
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Initiation factors are released and next charged tRNA is ready to join
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The process
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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)
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Ribosome shifts onto next codon and (now uncharged) tRNA leaves the complex (from E site) to continue the process
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Process stops when stop codon (UAA, UAG, UGA) is found, tRNA keeps leaving from E site until the amino acids have deattached
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Initiation process continues until required length is obtained for the polypeptide chain
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-requires elongation factors (carries GTP – hydrolyses gtp and releases energy)
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A protein release factor binds to the A site of the ribosome, causing the bond connected to the polypeptide of the tRNA to break
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Carboxyl terminus is created at the end of the polypeptide chain following the bond breakage
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Plasma membrane
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Regulates the passage of materials into and out of the cell
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Nuclear envelope
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Organizes/maintains nuclear content - Molecules move in/out of nuclear envelop using nuclear pores
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Endoplasmic reticulum
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Protein (rough) and lipid (smooth) synthesis and transport
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Golgi apparatus
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“Shipping and receiving center” Modify/sort proteins and lipids
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Lysosomes
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Digestive enzymes can help metabolize/breakdown proteins, nucleic acids, carbs
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