Short Answer Flashcards
Post Transcriptional Modifications
Post Transcriptional modifications occur after transcription has taken place. It occurs because the pre m-RNA is vulnerable to enzymes and conditions outside the cell nucleus. It must undergo additional modifications to exit the nucleus and go to the ribosome.
- The addition of 50 to 250 adenine nucleotides by the enzyme poly-A polymerase. They are added one at a time to the 3’ end. They are called the poly (A) tail and allows mRNA to be translated efficiently and protects it from RNA digesting enzymes in the cytosol.
- A sequence of 7 Gs added to the 5’ end of a pre-mRNA molecule. The 5’ cap functions as the initial attachment site for mRNAs to ribosomes to allow for translation (aka: capping & tailing)
- The pre-mRNA molecule is made of exons (coding) and introns (non-coding). The introns are spread across the gene and need to be taken out in order to prevent incorrectly folded proteins. A process called mRNA splicing removes (done by spliceosomes & snRNP) the introns from the pre-mRNA and joins the exons together. The exons may be joined in different combinations in a process called alternative splicing that allows more than one possible polypeptide to from from a single gene.
Human reflex arc
Reflex arc: a neural circuit that travels through the spinal chord but does not require for the coordination of the brain (allows for reflex action).
Example: Finger touches something hot
1. A pain receptor in the finger stimulates an afferent neuron
2. The afferent neuron transmits the impulses to the spinal cord.
3. interneurons integrate the information (sent to brain & spinal chord)
4. One efferent neuron stimulates the flexor muscle to contract
5. The other efferent neuron sends inhibitory signals that keep the extensor muscle from contracting
6. The bicep muscle contracts, withdrawing the hand from the pain (response)
Cyclic electron Transport/Cyclic Phophorylation
Phosphorylation: the transfer of a phosphate group, usually from ATP, to another molecule.
Only requires photo system 1.
Reduced ferredozin donates electrons back to plastoquinone. Which gets reduced and oxidized and keeps moving protons across the thylakoid membrane without Photosystem 2.
The result of this is that the energy absorbed from light is converted into the chemical energy of ATP without water reduction or reduction of NADP+ to NADPH.
referred to as cyclic phosphorylation because the light energy captured is ultimately used to drive the phosphorylation of ADP to ATP
Action Potential Graph/Seven neural stages(human reflex)
Action potential: the voltage difference across a nerve cell membrane when the nerve is excited.
Threshold potential: potential at which an action potential is generated by a neuron
refractory period: period of time during which the threshold required for the generation of action potential is much higher than normal.
Difference between Ammonia, urea and uric acid
Ammonia -NH3
By product of deamination and is a highly toxic substance. Can only be transported and secreted in very dilute solutions. They are excreted by animals with an abundant supply of water (bony fish & marine invertebrates) as they are able to secrete ammonia directly from the body in this very dilute form.
Urea -H2NCONH2
Combination of ammonia and HCO3 by the liver. Urea is a very soluble substance with 0.001% the toxicity of ammonia. It’s eliminated with less water than ammonia. It’s secreted by mammals, some reptiles and most amphibians.
Uric Acid -C5H4N4O3
Non toxic substance with low solubility. When urine is concentrated in its final stages, uric acid forms crystals that are expelled from the body with minimal amounts of water (bird poop is uric acid crystals).
Concentration of beakers
Hypotonic
a solution that has a lower solute concentration than another concentration. Animal cells may swell up to the point of bursting.
Hypertonic
solution that has a higher solution concentration than another solution. Cells expend energy and shrink
Isotonic
solution that has the same concentration as another solution. No change in cell size or shape.
Chargaff
Adenine -30.9%
Thymine -29.4%
Guanine -19.9%
Cytosine -19.8%
