ap bio oral assessment: unit 4

47. Describe the three stages of cell signaling. Provide a real world example. 

47. Describe the three stages of cell signaling. Provide a real world example. 

The three stages of cell signaling include reception, transduction, and response. Reception is when the ligand attaches to a receptor, setting off a chain reaction. This chain reaction is the process of transduction, which can include phosphorylation or the switch-on of enzyme after enzyme. Response is when the cell responds to the transduction and reception, and it usually consists of gene transcription. 

A real world example of this could be the transcription of mRNA in the nucleus. The ligand would bind to the receptor which would be reception. After this the cell will go through either a g protein or tyrosine kinase in order to transmit the signal into the cell and amplify it through a phosphorylation cascade in transduction. Lastly the DNA would be transcribed into mRNA. 

48. How do animal nervous systems detect external and internal signals, transmit and integrate information, and  produce response in the body?

Animal nervous systems detect external and internal signals via dendrites on the neuron’s soma. After attaching to the receptors of the dendrites, the signal travels down through the axon through the exchange of sodium and potassium ions to achieve action potential. 3 sodiums enter and 2 potassiums exit, skipping each bundle sheath to make the signal travel faster. After this, the response is when the neurotransmitters receive the signal to exit the synaptic vesicles and transfer the information to the next set of dendrites.

Step 1 is reception where a ligand binds to a receptor to start the response. Step 2 is transduction where the signal is amplified or transferred by a cascade of proteins. Step 3 is the response where the signal is brought to the target gene to produce the specific response.

49. Describe how the animal reflex arc differs from typical stimulus-response transmission pathways. Provide  reasoning to support the claim that reflex arcs help organisms avoid serious injury.

Reflex is the movement of neurons to the spine but does not reach the brain before motor neurons are activated. Typical stimulus-response reach the brain before motor neurons are released. Reflexes are useful because they push an organism away from a harmful stimulus in a split second. For example, humans move their hand away from a very hot surface immediately, preventing major burns.

50. Describe resting and action potentials.

Resting potential is a neuron at rest where K⁺ enters while Na⁺ exits. Action potential is used to pass on a signal and 2 K⁺ exits while 3 Na⁺ enters.

51. Describe a generalized hormone-signaling pathway, and explain the role of each structure.

Step 1 is reception where a ligand binds to a receptor to start the response. Step 2 is transduction where the signal is amplified or transferred by a cascade of proteins. Step 3 is the response where the signal is brought to the target gene to produce the specific response.

52. What are the ways that hormones can affect target organs?

Hormones can affect target organs by invoking a change through binding to the receptor protein where a signal is generated. The signal in these can cause change in the target organs such as changing the cell activity of the target organ through means of a response or specifically in genes. As such the activity of the cell changes in response to the hormone such as maintaining homeostasis.

For example, an increase in blood-glucose levels will cause the pancreas to secrete insulin which signals cells to store glucose until glucose levels are back to normal. However if insulin is not produced than this can cause diabetes which causes damage to organs such as the kidney and the function of nerves.

53. How do feedback systems control homeostasis in the human body? Provide examples of positive and negative  feedback in the regulation of homeostasis by hormones.

Feedback systems control homeostasis by increasing or decreasing unstable levels. For example, an example of negative feedback is body temperature. If it is too high, our body will produce sweat to help bring the temperature down. An example of positive feedback is the lactation of women during breastfeeding. It will continue to amplify and keep undergoing lactation.

54. Describe how antagonistic hormone pairs, insulin and glucagon, regulate blood glucose levels in humans.

When a human eats, they have an increase in glucose levels and store the excess glucose in the form of glucagon in their pancreas. When glucose levels decrease, the alpha cells in the pancreas releases glucagon and the liver breaks it down to release glucose, which increases/stabilizes the glucose levels. However, when glucose levels are too high, the beta cells in the pancreas release insulin, which allows the liver to store glucose as glycogen and glucose levels decreases/stabilizes.

55. Describe the variety of chemical defenses animals have against infection

When animals are infected by a virus or bacteria, their body will first attempt to defend itself through its first line of defense which includes mucus and skin. This is very external and outerlevel type of defense. If the first line fails, the body will then go into its second line of defense which includes non-specific line of defenses including natural killer cells and macrophages. Natural killer cells induce apoptosis to invaders. Macrophages eat pathogens. The last line of defense is more specific and includes specific t cells and b cells which target the antigens identified by lymphocytes.

56. Describe how damage and disease can affect the functioning of the nervous, endocrine, and immune systems.  Provide examples.

Damage and disease affect the functioning of the nervous, endocrine, and immune system because there can be a delay or lack of proper signaling. For example, if the neurons in your fingers are damaged from a third-degree burn, it is likely that you won’t be able to feel anything since the neurons won’t send the signal through the central nervous system into our brain to detect the stimulus.

Autoimmune disease also causes immune bodies to attack one’s own cells

57. What is apoptosis? Provide a real life example.

Apoptosis is a form of self suicide a cell may perform in order to get rid of any infections in the body. For example, in the immune system, macrophages may eat up infected bacteria, however if they feel they are a danger to the body and unable to rid of the virus they will perform apoptosis. Another example would be tadpoles turning into frogs where they lose their tail through the process of apoptosis.

58. Describe the functions mitosis serves in multicellular organisms.

The main function of mitosis is to help with growth and repair within an organism. Mitosis involves the production of 2 indentical daughter cells each with 46 chromosomes making them diploid. Mitosis occurs in order to help an organism grow or repair damaged tissue. For example, if you were to get a cut on your foot, your epidermal cells (skin cells) would then undergo mitosis in order to heal the wound. Therefore mitosis is vital to help an organism grow and repair tissue.

59. Explain how mitosis maintains genetic consistency.

The purpose of mitosis is to create clones of the original cell. In mitosis, two diploid daughter cells are produced that are identical to the original parent cell. A parent cell contains 46 chromosomes with an organisms DNA, through mitosis, the 2 daughter cells will contain the exact same copies of the 46 chromosomes due the the replication of the chromosomes in S phase. Therefore, through mitosis, cells are able to produce genetically identical cells to maintain genetic consistency through the body although there is possibility of error which may lead to genetic disorder.

60. Explain the action of cyclins and cdks in the regulation of the cell cycle.

Cyclin levels vary in cell depending on mitotic phase and bind to CDKs to turn them off or on. CDKs maintain constant levels and activate cyclins through phosphorylation. Binding of cyclin and CDK1 triggers cells to pass from G2 to mitosis. Together, they drive cells through the phases of mitosis.

61. Explain the consequences of a loss of regulation of mitosis.

Checkpoints during interphase of mitosis regulate the cell and maintain genetic integrity. Mutations in DNA/failure to  regulate the cell properly can lead to the creation of genetically faulty cells that can cause harm to the body. Loss of regulation of mitosis can result in excess cell growth and reproduction causing a buildup of somatic cells leading to the formation of tumors (cancer). Example of regulator is density dependent inhibition/anchorage dependence; loss of this also=cancer.