Physiology 101 - Practice Test 2

Front: Where are the Krebs cycle enzymes located?

Back: The Krebs cycle enzymes are located in the mitochondrial matrix.

Front: What happens to NADH during anaerobic glycolysis, and why?

Back: NADH is oxidised to NAD⁺. This restores the NAD⁺ needed for glycolysis to keep producing a small amount of ATP when oxygen is limited.

Front: What is a key enzyme that regulates glycolysis?

Back: Phosphofructokinase (PFK) is a key regulatory enzyme. It catalyses the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate.

Front: Where is carbon dioxide produced during cellular respiration?

Back: Carbon dioxide is produced mainly during the Krebs cycle. It is also produced when pyruvate is converted into acetyl-CoA before entering the Krebs cycle.

Front: What is chemiosmosis?

Back: Chemiosmosis is the movement of hydrogen ions through ATP synthase down their concentration gradient. The energy from this movement allows ATP synthase to make ATP.

Front: Explain how the body supplies energy during a mountain climb and how energy pathways change as the climb continues.

Back: At the start of the climb, muscles use their stored ATP and phosphocreatine for immediate energy. The body then relies more on aerobic respiration, which uses oxygen to break down glucose and produce ATP.

Aerobic glucose breakdown includes glycolysis, conversion of pyruvate to acetyl-CoA, the Krebs cycle, and the electron transport chain. Glycolysis produces two pyruvate, two NADH and a net gain of two ATP per glucose. The Krebs cycle releases carbon dioxide and produces energy carriers and a small amount of ATP. NADH and FADH₂ deliver electrons to the electron transport chain. Oxygen accepts the electrons at the end of the chain, and the proton gradient powers ATP production by chemiosmosis. The lecture estimates a total of 36–38 ATP per glucose.

As the climb continues, the body uses glucose in the blood and glycogen stored in the muscles and liver. It can also use fat for energy, with a smaller contribution from protein during prolonged activity. As altitude increases, oxygen’s partial pressure decreases, so less oxygen is available to the body. If oxygen supply cannot meet the muscles’ needs, anaerobic glycolysis contributes more. It makes only a small amount of ATP; pyruvate is converted to lactate, and NADH is oxidised to NAD⁺ so glycolysis can continue.

Front: What is a major function of the nephron loop?

Back: The nephron loop helps create a concentration gradient in the kidney medulla. This gradient helps the kidneys reabsorb water and produce more concentrated urine.

Front: How do the kidneys respond when extracellular fluid pH increases?

Back: When ECF pH increases, the kidneys excrete more bicarbonate ions and secrete fewer hydrogen ions. This helps bring pH back down toward its normal range.

Front: Which glomerular filtration force favours filtration?

Back: Blood hydrostatic pressure in the glomerular capillaries pushes water and small solutes out of the blood and into the glomerular capsule.

Front: Name substances that are filtered at the glomerulus.

Back: Small substances such as water, glucose, sodium ions, amino acids and urea can pass into the filtrate. Blood cells and large proteins, such as albumin, normally remain in the blood.

Front: How does angiotensin II affect sodium reabsorption?

Back: Angiotensin II stimulates the adrenal cortex to release aldosterone. Aldosterone increases sodium reabsorption in the distal nephron, helping the body retain sodium and water.

Front: How does the myogenic mechanism help stabilise GFR when blood pressure rises or falls?

Back: The myogenic mechanism changes the diameter of the afferent arteriole to help keep GFR stable.

When blood pressure rises, such as during exercise, the afferent arteriole wall stretches. Its smooth muscle contracts, causing the arteriole to constrict. This reduces blood flow into the glomerulus and brings GFR back toward normal.

When blood pressure falls, the afferent arteriole is stretched less. Its smooth muscle relaxes and the arteriole dilates, helping increase blood flow into the glomerulus and restore GFR. Efferent arteriole constriction can also help maintain glomerular pressure, but it is generally associated with the renin–angiotensin system rather than the myogenic response itself.

Front: What pathway does sperm take from the testis to the outside of the body?

Back: Epididymis → ductus deferens → ejaculatory duct → urethra. Sperm mature and are stored in the epididymis before travelling through the ductus deferens. They then enter the ejaculatory duct and pass through the urethra.

Front: What does the luteinising hormone surge trigger during the ovarian cycle?

Back: The LH surge triggers ovulation, when the secondary oocyte is released from the ovary. It is released with follicle cells called the corona radiata still attached.

Front: What are the two main parts of a blastocyst?

Back: The blastocyst has an outer layer of cells called the trophoblast and an inner cell mass, also called the embryoblast. The inner cell mass develops into the embryo; the trophoblast contributes to the placenta.

Front: Which blood vessel carries oxygenated blood from the placenta to the foetus?

Back: The umbilical vein carries oxygenated blood from the placenta to the foetus. The umbilical arteries carry blood from the foetus back to the placenta.

Front: What happens during the dilation and expulsion stages of labour?

Back: During the dilation stage, contractions cause the cervix to open and the foetus moves toward the birth canal; the membranes may rupture. During the expulsion stage, the cervix is fully dilated—about 10 cm—and contractions push the baby through the vagina.

Front: Describe the three phases of the uterine cycle and the main hormone changes in each.

1. Menses (about days 1–7): The functional layer of the endometrium is shed. Oestrogen and progesterone are low because the corpus luteum has broken down. FSH begins to rise and stimulates follicle development.

2. Proliferative phase (about days 7–14): The endometrium repairs and thickens, and its blood vessels and glands develop. Developing ovarian follicles release increasing oestrogen. High oestrogen near the end of this phase contributes to an LH surge, which triggers ovulation around day 14.

2. Proliferative phase (about days 7–14): The endometrium repairs and thickens, and its blood vessels and glands develop. Developing ovarian follicles release increasing oestrogen. High oestrogen near the end of this phase contributes to an LH surge, which triggers ovulation around day 14.

3. Secretory phase (about days 14–28): The corpus luteum releases progesterone and some oestrogen. These hormones maintain the endometrium and stimulate its glands to secrete nutrients, preparing it for possible implantation. If pregnancy does not occur, the corpus luteum breaks down, hormone levels fall, and menstruation begins again.