Bio/Biochem Flashcards
What does it mean when an amino acid is “essential?”
An essential amino acid is one that an organism cannot synthesize on its own, and therefore must consume in its diet.
Explain the relationship between microtubules and globular proteins.
Microtubules are formed through the binding of globular proteins to one another in quarternary structures, which are usually the result of intermolecular forces such as hydrogen bonds, not covalent bonds that could be hydrolyzed.
Tubulin is a globular protein that is assembled to form microtubules.
What is the main function of the Golgi Apparatus?
The Golgi apparatus is involved in the packaging and delivery of proteins (to the cell membrane).
What is the main function of Lysosomes?
They contain hydrolytic enzymes and fuse with vesicles, dissolving their contents.
They are not involved in protein transport.
What is the main function of the Endoplasmic reticulum?
The ER is involved in the synthesis of proteins, which must then be passed to the Golgi if they are to be transported to the cell membrane.
What is the main function of the Mitochondria?
The mitochondria is the location of various oxidation processes that produce energy in the form of ATP, including the Citric Acid Cycle, Fatty Acid Metabolism, and the Electron Transport Chain.
Briefly explain how a lac operon works in the presence of lactose.
When lactose is present, it binds the lac repressor, causing the repressor to DISSOCIATE from the lac operon, and thereby allowing transcription of the proteins required to metabolize lactose.
How do calcium ions act as a signaling molecule in the synaptic end bulb of a neuron?
They signal the release of vesicles from the synaptic end bulb of a neuron.
The synaptic end bulb of a neuron receives a nerve impulse (action potential) that causes depolarization. This depolarization opens voltage-gated Ca2+ channels in the membrane. Opening of these channels allows an influx of calcium ions from the synaptic cleft, which signals the migration and release of vesicles containing neurotransmitter to the synaptic end bulb. Therefore, calcium ions are acting as messenger molecules that initiate the secretion of the neurotransmitter.
What are some examples of physiological processes that exhibit positive feedback?
- The release of oxytocin from the posterior pituitary during childbirth. Oxytocin causes uterine contractions, but also causes release of more oxytocin from the pituitary, causing more uterine contractions.
- Blood clotting is another example. Platelets release chemicals that attract more platelets, which is repeated in turn until the bleeding stops.
- Spreading of an action potential. An action potential generated at one voltage-gated channel depolarizes the membrane sufficiently to activate other voltage-gated channels in its vicinity, which in turn do the same to channels in their vicinity.
What are some things you know about viruses?
- Viruses are highly simplified, non-cellular infectious agents which are structurally different from bacteria (bacteria are cellular prokaryotes).
- Most viruses must not only use the same nucleotide bases, but they must use the same bases as their host cells, so that they can utilize host cell machinery.
- Viruses are acellular and do NOT have cell walls nor do they have cellular organelles.
Explain the “wobble” in genetic coding.
In many cases, a single amino acid may correspond to multiple codons, in which case the first two bases are almost always the same, and the difference exists in the third base. This variance in the base at the third position is referred to as “wobble.”
Explain entropy of protein folding.
Protein folding involves a transition from a more disordered state to a more ordered state. This is possible because the net ΔS of the surroundings is positive, resulting in a negative ΔG for the overall process, therefore spontaneous folding is not prevented.
The reduction in the solvation layer is associated with a significant positive entropy which overcomes the entropic penalty associated with increased order in the folded state. This phenomenon is sometimes called the “hydrophobic effect.” This allows the net Gibbs free energy change to be negative and therefore the process is still spontaneous.
