Week 4 Notes
Week 4 Notes CBIO 2200
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This 8 page Class Notes was uploaded by Bailey Dickinson on Thursday September 1, 2016. The Class Notes belongs to CBIO 2200 at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by in Fall 2016. Since its upload, it has received 12 views. For similar materials see Anatomy and Physiology I in Cellular biology at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months.
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Date Created: 09/01/16
WEEK 4 NOTES (8/30-9/1) “Name one Passive transport process. Describe why this process is passive, and which way substances are moving across the membrane.” • Diffusion of oxygen across the plasma membrane. From higher to lower concentration • Facilitated diffusion is saturable- you have as many places as can be occupied by the substrate. Every protein interacting with a solute molecule- so can’t go any faster because we don’t have any proteins that are waiting for a solute. Tonicity: one solution relative to something else and reference point is the cell interior Osmolarity: a measure of how many particles are present in the solvent Filtration: the flow of liquid through a filter (or membrane that acts like a filter) due to hydrostatic pressure Active transport processes: require energy (provided directly by ATP or energy provided indirectly by another process) One phosphate group getting clipped off of the ATP provides energy. Primary active transport • Hydrolysis of ATP provides energy to drive the mechanism • Usually catalyzed by membrane protein “pumps” • Can result in the formation of a concentration gradient across a membrane • Na+/K+ ATP-ase in an important example 2 K+ are pumped in and 3 Na+ are pumped out. This creates a Cells work really hard to keep sodium out. The ATP phosphorylates the protein pump and the ATP is hydrolyzed (by the up-pump) for that energy to be released. The protein pump is dephosphorylated and the K+ ions dissociate from it. The pump has different affinities for K+ and Na+ depending on its shapes. Electrochemical gradient. The sodium goes into the cell just because it wants to move down its concentration gradient Secondary active transport • ATP is used indirectly • Transport of 2 or more substances that are “coupled” to each other • Movement of one substance “downhill” drives the movement of another substance “uphill” • (Water builds up behind a dam and you can release it to create energy) • We can use it to drive cells out or drive cells in. The energy is coming from the sodium gradient. • Opposite directions (antiport) Same direction (symport) Is the inside of the plasma membrane positive or negative relative to the outside? What role do you think active transport plays in generating this difference in charge? Negative- because the outside is more positive. 3 out and 2 in. Separation of concentration and a separation of charge. Vesicular Transport • Large molecules or particles are brought into the cell • Sacs or vesicles are formed from invaginations of the plasma membrane -Endocytosis -Phagocytosis -Pinocytosis -Exocytosis These only occur in living cells The transport of a molecule is described as: moving down its concentration gradient, rate of transport is saturable (reaches a maximum), energy is NOT required. Facilitated diffusion Digestion in the stomach requires the production of highly concentrated acid (HCl). What transport process do you think is involved in acid production in the stomach? Moving against concentration gradient. Active transport. Actually, secondary active transport. What is an electrochemical gradient (p. 528-529) a) Concentration b) Charge Transcription (Side information: Some people respond to some drugs differently because some people have genes that metabolize certain drugs faster than others) Weak hydrogen bonds between strands- can be broken easily The information about the proteins is stored in the nucleotides Protein structure is linked to DNA structure • Proteins are like words- amino acids are letters • DNA is like words- nitrogenous bases are like the letters • 3 BASE TRIPLET = 1 amino acid (3 nitrogenous bases in a particular order code for a specific amino acid) Some amino acids have more than one code for them. Protein synthesis • Proteins dictate the function(s) of the cell • Protein synthesis is directed by genetic information • Genetic information is DNA in the nucleus • DNA à RNA à Protein • We go form DNA to RNA because RNA represents just a section of DNA • RNA can leave the nucleus Protein synthesis includes 2 processes, or steps (transcription and translation) Transcription is like taking notes in shorthand. DNA à RNA (mRNA) Translation is from RNA à proteins (nucleotide language to the amino acid language) (tRNA) The cytosol is where to protein synthesis machinery is RNA is similar to DNA • Composed of nucleotides -Sugar-phosphate “backbone” with nitrogen-containing bases RNA is different than DNA • Uracil replaces thymine as the nitrogen-containing base • Ribose replaces deoxyribose as the sugar in the “backbone” • RNA is always found as a single strand 3 main kinds of RNA • tRNA (transfer RNA) -Picks up amino acids in the cytosol and brings them to the ribosome for the polypeptide synthesis • rRNA (ribosomal RNA) -Makes up part of the ribosome • mRNA (messenger RNA) -The “copy” of the DNA sequence that travels to the ribosome and directs protein synthesis. “Gets the message”. The mRNA is complementary. The gene is the specific part of the DNA that codes for a specific protein The mRNA strand is complementary to the template strand with Uracil. The mRNA strand is therefore the same as the DNA coding strand with Uracil instead. Translation- mRNA code becomes a protein Translation • Triplet code of the mRNA is converted to the “language” of amino acids • mRNA interacts with other kinds of RNA to build a protein (or strands of amino acidss Introns are spliced out and exons remain. It’s now believed that introns still play a role, we are just not sure what their purpose is Each group of three bases is a codon tRNA has anticodon mRNA has codon The recognition between the anticodon and the codon occurs based on the complementary base pairing The ribosome forms the peptide bonds between the amino acids AUG is start codon P side translates, A site is where the transfer RNA carrying the next amino acid goes, the E site is where the transfer RNA is released. The amino acid polypeptide chain grows out of the P site How is DNA replication similar to transcription? How is translation different to transcription? During DNA replication, 1 nucleotide is deleted from a sequence that normally codes for a polypeptide. What effect will this deletion have on any resulting amino acid sequences? -Frame shift. All of the codes from that one on are messed up.