MCAT Biology : Systems Biology and Tissue Types
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Example Question #81 : Hormones
The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the sub-arachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.
Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma.
Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma.
During a hematoma, the intracrainal pressure could increase and push on certain regions of the brain. The compression of a certain region could either excite or inhibit the area. If a forty-year-old patient is showing signs of diabetes with excess bone growth, which region could be compressed and what hormone will be shown in excess from a blood test?
Posterior pituitary; luteinizing hormone
Anterior pituitary; testosterone
Posterior pituitary; growth hormone
Anterior pituitary; growth hormone
Anterior pituitary; luteinizing hormone
Anterior pituitary; growth hormone
Post-puberty bone growth and diabetes-like hyperglycemia are symptoms associated with excess in growth hormone (GH). GH is released by the anterior pituitary and promotes bone growth pre-puberty but acromegaly in post-puberty. In addition, GH increases blood glucose level and therefore mimics diabetes.
Example Question #754 : Mcat Biological Sciences
The cellular membrane is a very important structure. The lipid bilayer is both hydrophilic and hydrophobic. The hydrophilic layer faces the extracellular fluid and the cytosol of the cell. The hydrophobic portion of the lipid bilayer stays in between the hydrophobic regions like a sandwich. This bilayer separation allows for communication, protection, and homeostasis.
One of the most utilized signaling transduction pathways is the G protein-coupled receptor pathway. The hydrophobic and hydrophilic properties of the cellular membrane allows for the peptide and other hydrophilic hormones to bind to the receptor on the cellular surface but to not enter the cell. This regulation allows for activation despite the hormone’s short half-life. On the other hand, hydrophobic hormones must have longer half-lives to allow for these ligands to cross the lipid bilayer, travel through the cell’s cytosol and eventually reach the nucleus.
Cholesterol allows the lipid bilayer to maintain its fluidity despite the fluctuation in the body’s temperature due to events such as increasing metabolism. Cholesterol binds to the hydrophobic tails of the lipid bilayer. When the temperature is low, the cholesterol molecules prevent the hydrophobic tails from compacting and solidifying. When the temperature is high, the hydrophobic tails will be excited and will move excessively. This excess movement will bring instability to the bilayer. Cholesterol will prevent excessive movement.
Epinephrine binds to its receptor on the surface of the cell. Molecule A also binds to the same receptor at the active site, thereby inactivating the receptor. What type of regulation is this?
Cooperation
None of the above
Negative feedback
Competitive inhibition
Non-competitive inhibition
Competitive inhibition
Molecule A is competing with epinephrine for the binding site. However when bound, molecule A blocks the receptor rather than activating it. Competitive inhibitors can be overcome by increasing the concentration of substrate so it outcompetes the inhibitor for the enzyme active site.
Example Question #721 : Systems Biology And Tissue Types
If a person has low blood glucose levels, which of the following is false?
Cortisol levels will be higher than normal in the body
Glycogenolysis will be stimulated in the liver
Gluconeogenesis will be inhibited in the liver
Insulin release will be inhibited
Glucagon levels will be higher than normal in the body
Gluconeogenesis will be inhibited in the liver
Cortisol and glucagon are both elevated when a person is experiencing low blood glucose levels. Glucagon is responsible for elevating blood glucose levels by stimulating glycogenolysis in the liver, and cortisol increases blood glucose levels by stimulating gluconeogenesis in the liver.
Example Question #1 : Types Of Hormones
ACTH is this type of hormone __________.
I. eicosanoid
II. steroid
III. polypeptide
IV. paracrine
V. None of these is a correct description
IV
III
I
V
II
III
There are many types of hormones, including all of the categories listed.
Gaseous? The dissolved gas, NO, is now known to be an important second messenger. Paracrine hormones are those that act on cells in close proximity to the secreting cell. ACTH is a polypeptide hormone secreted by the pituitary and conveyed by the bloodstream to the adrenal gland a meter away, so it is clearly not paracrine. ACTH causes the secretion of steroid hormones, but it is not a steroid.
Example Question #2 : Types Of Hormones
Which of the following is NOT a characteristic of steroid hormones?
They are synthesized by smooth endoplasmic reticulum.
They require carrier proteins to travel through the bloodstream
They are derived from amino acids
They are hydrophobic
They are derived from amino acids
Steroid hormones are hydrophobic molecules, synthesized by smooth endoplasmic reticulum. As they are hydrophobic, they require a hydrophilic carrier protein to transport them through the bloodstream. Steroid hormones are generally derived from cholesterol, not amino acids.
Example Question #3 : Types Of Hormones
Which of the following is a direct hormone?
Adrenocorticotropic hormone (ACTH)
Growth hormone (GH)
Follicle-stimulating hormone (FSH)
Thyroid-stimulating hormone (TSH)
Growth hormone (GH)
The pneumonic to remember the hormone of the anterior pituitary is "FLAT PEG." Hormones in the word "FLAT" are tropic hormones, meaning that they act upon other endocrine glands as their target organs. Hormones in the word "PEG" are direct hormones, meaning they act directly on non-endocrine organs.
F - Follicle-stimulating hormone
L - Luteinizing hormone
A - Adrenocorticotropic hormone
T - Thyroid-stimulating hormone
P - Prolactin
E - Endorphins
G - Growth hormone
Example Question #4 : Types Of Hormones
Which of the following statements is a key difference between a peptide hormone and a steroid hormone?
One travels a shorter distance than the other
They attach to receptors in different parts of the target cell
They affect the body for different lengths of time
Only one travels through the bloodstream in order to reach target cells
They attach to receptors in different parts of the target cell
All hormones travel through the bloodstream in order to reach their target cells, but nonpolar hormones typically require a carrier protein. A key difference between peptide hormones and steroid hormones is their solubility. Peptide hormones are polar, which makes it difficult for them to pass through cell membranes. As a result, they attach to a receptor on the outside of the membrane. Steroid hormones, on the other hand, are nonpolar and can pass through cell membranes. They enter the nucleus and directly affect the cell at the transcription level.
Example Question #5 : Types Of Hormones
Which of the following hormones would not require a carrier protein in the bloodstream?
Aldosterone
Triiodothyronine
Testosterone
Oxytocin
Oxytocin
There are three main types of hormones: peptide hormones, steroid hormones, and tyrosine derivatives. Only peptide hormones are soluble in water, and do not require carrier proteins in the bloodstream. Oxytocin is a peptide hormone, so it will not require a carrier protein.
Aldosterone and testosterone are all steroid hormones, and require a carrier protein. Triiodothyronine (T3) is a tyrosine derivative, and also requires a carrier.
Example Question #6 : Types Of Hormones
Which of the following hormones is a steroid hormone?
Epinephrine
Testosterone
Luteinizing hormone
Follicle-stimulating hormone
Testosterone
It is important to know the three types of hormones: steroid, peptide, and tyrosine-derived hormones. Thyroid-stimulating hormone and the catecholamines (including epinephrine) are tyrosine-derived hormones. Luteinizing hormone, follicle-stimulating hormone, and growth hormone are all peptide hormones. Steroid hormones include testosterone and estrogen.
Example Question #7 : Types Of Hormones
Which of the following is a peptide hormone?
Estrogen
Thyroid-stimulating hormone
Epinephrine
Luteinizing hormone
Luteinizing hormone
It is important to know the three types of hormones: steroid, peptide, and tyrosine-derived hormones. Thyroid-stimulating hormone and the catecholamines (including epinephrine) are tyrosine-derived hormones. Luteinizing hormone, follicle-stimulating hormone, and growth hormone are all peptide hormones. Steroid hormones include testosterone and estrogen.
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