Transport & Homeostasis
During childbirth, uterine contractions stimulate oxytocin release, which strengthens the contractions. What type of feedback is this?
Positive feedback
How many ATP are produced net during glycolysis from one glucose molecule?
2 ATP
Name the two products released when a triglyceride undergoes lipolysis.
Glycerol and free fatty acids
A sweat gland releases its product through a duct onto the skin. Is it endocrine or exocrine?
Exocrine
A child has excessive growth hormone before the epiphyseal plates close. What growth disorder can result?
Gigantism
A steroid molecule crosses the plasma membrane from high concentration to low concentration without a transport protein. Name the transport mechanism.
Simple diffusion
Match each process to its location: glycolysis, Krebs cycle, and electron transport chain.
Cytosol; mitochondrial matrix; inner mitochondrial membrane
What carbon-containing product of beta oxidation can enter the Krebs cycle?
Acetyl-CoA
A hormone travels bound to a carrier protein and changes gene transcription after entering its target cell. Is it most likely water-soluble or lipid-soluble?
Lipid-soluble
One hormone increases water reabsorption directly. Another increases sodium reabsorption, with water following. Name both hormones.
ADH directly conserves water; aldosterone increases sodium reabsorption
A cell contains 300 mOsm of nonpenetrating solute and enters a 200 mOsm solution of nonpenetrating solute. Predict the direction of net water movement and the cell-volume change.
Water moves into the cell, so the cell swells
Complete aerobic oxidation yields about 30–32 ATP per glucose. Only 4 are made directly by glycolysis and the Krebs cycle combined. Where does the remainder come from?
The electron transport chain and chemiosmosis
Before most amino-acid carbon skeletons can enter energy pathways, what must happen to the amino group?
It must be transferred or removed, then its nitrogen is disposed of mainly as urea
Low blood calcium directly stimulates parathyroid cells. Classify the stimulus as humoral, neural, or hormonal.
Humoral
Compare the major adrenal hormone in the immediate stress response with the hormone that supports a slower, sustained response.
Epinephrine is immediate; cortisol supports the slower response
A toxin stops the sodium-potassium pump. As the sodium gradient gradually weakens, what happens to sodium-glucose cotransport into the cell?
It decreases
A compound prevents NADH from donating electrons to the electron transport chain. Predict one immediate effect on ATP production.
Oxidative ATP production decreases
After a mixed meal, which direction should dominate for glycogen, triglyceride, and body protein: synthesis or breakdown?
Synthesis
A hypothalamic neuron makes a hormone that travels down its axon and enters the blood from the pituitary. Which pituitary lobe releases it?
Posterior pituitary
A patient produces little or no insulin because pancreatic beta cells were destroyed. Which form of diabetes best fits?
Type 1 diabetes
A membrane remains equally permeable, but its surface area doubles while diffusion distance is cut in half. Relative to the original condition, how should diffusion rate change?
It should increase substantially
A cell can perform glycolysis but cannot regenerate NAD+ from NADH. Which pathway stops first, and why?
Glycolysis stops because it requires NAD+
During prolonged fasting, adipose tissue releases fatty acids and glycerol. Explain one major metabolic fate of each in the liver.
Fatty acids undergo beta oxidation; glycerol can support gluconeogenesis
A patient receives excess thyroid hormone. Predict the resulting changes in TRH and TSH if negative feedback remains intact.
Both TRH and TSH decrease
In the male reproductive axis, identify the pituitary hormone that acts on Leydig cells and the hormone Leydig cells release.
LH stimulates Leydig cells to release testosterone
One glucose molecule completes glycolysis, conversion of pyruvate to acetyl-CoA, and the Krebs cycle. Before the electron transport chain begins, how many ATP, NADH, and FADH₂ have been produced in total?
4 ATP, 10 NADH, and 2 FADH₂