• counter current heat xchange - arteries contain warm blood and as that blood travels to its target it gets cooled, cool blood in veins returns warm. the warm blood gives off heat to the blood returning , saving energy
• a protein complex is made following the four protein structures
• primary structure - amino acid sequence
• secondary structure - H bonds to make alpha helices, beta sheets (backbone bonds)
• tertiary structure - all bonds included (covalent, van der waals, ionic) among the amino acid side chains. this determines the overall shape of the polypeptide
• if there are two or more polypeptide chains, this determines the overall shape of the protein. (multi subunit complex). the chains will bond to each other
• synthesis of mRNA to DNA -

replication - a DNA helix is split by helicase, and proteins such as single stranded proteins help the split strands from coming back together. topoisomerase makes temporary cuts in the DNA backbone to ease the tension of the unwinding of DNA. at the replication fork, there will be a leading strand which uses DNA polymerase to polymerize the new strand of DNA continuously. this polymerizes away from the towards, but the lagging strand (made up of okazaki fragments) is polymerized away from the fork, causing it to be fragmented as the unzipping left over by the leading strand exposes new DNA . after these polymerizing strands, the RNA primers are replaced by DNA and the fragments are sealed together via help of DNA ligase. the result is a semiconservative model of DNA, a hybrid of both the old DNA and the newly polymerized strand. transcription - the gene we want to synthesize a copy of will be on one of the strands, so the strand that the gene is on will be the template strand. to get to the template strand, we unwind the DNA strand again. RNA polymerase binds to the promoter at the top of the gene, and this is initiation. it polymerizes during elongation, and when the pol reaches a stop codon on the template strand, it terminates the elongation and this is called termination. translation - the RNA transcript is first spliced with its introns cut out, 5 cap and poly A tail attached to guide the transcript to the ribosome. codons on the RNA will match up to anticodons on TRNA, which hold the amino acids to be made into polypeptides. the codon on the RNA is what determins the amino acid on the TRNA. the finished polypeptide will leave the ribosome in the cytosol to the ER, then leave the ER in a vesicle made of the ER to the cis face of the golgi, processed in the medial golgi, then leave the golgi via its trans face. from there it will leave in a vesicle and taken to the cell membrane via the cytoskeleton tracks. the membrane of the vesciel will fuse with that of the cell membrane.

a competitive inhibiting drug would bind on the active site of an enzyme on the cell membrane, competing with the substrate of that enzyme.

stimulus pathway - sensory receptor such as skin senses the cold sensation via sensory neurons. these neurons send signals to the neurons in CNS , which then send signals to the motor neurons in the effector, such as muscles or glands, which prompt you to shiver.