MLT GlobePhysiology: Cell physiology & body fluids
44 Physiology MCQs on Cell physiology & body fluids with answers and explanations.
Inside a muscle fibre, glucose is oxidised in mitochondria to yield ATP. This process is known as cellular respiration, which:
Cellular respiration oxidises glucose and other fuels inside cells, mainly in mitochondria, to make ATP. Pulmonary ventilation is a separate process.
Claude Bernard's 'internal environment' (milieu interieur), which homeostasis keeps constant, refers to the:
The internal environment is the extracellular fluid (plasma and interstitial fluid) that bathes all cells. Homeostasis regulates its composition.
Which protein in the epidermis mainly makes the skin waterproof?
Keratinised cells of the stratum corneum, with their lipids, limit water loss. Melanin and carotene are pigments, and collagen is dermal.
Which transport process consumes ATP directly to move ions against their concentration gradients?
The sodium-potassium pump is primary active transport, hydrolysing ATP to move 3 Na+ out and 2 K+ in. The other processes are passive and follow gradients.
ECF volume is adjusted by several organ systems. Which system contributes least to this control?
The kidneys, hormones (ADH, aldosterone, ANP) and gut absorption and losses all affect ECF volume. The reproductive system has no regulatory role.
The Na+/K+-ATPase maintains which ion distribution across the cell membrane?
The pump moves 3 Na+ out and 2 K+ in. This keeps ICF low in Na+ and high in K+, and ECF high in Na+ and low in K+.
In an interphase (non-dividing) nucleus, DNA and its histone proteins exist as loosely coiled:
Between divisions, DNA is dispersed as chromatin. It condenses into visible chromosomes, each with two sister chromatids, only during mitosis or meiosis.
Which pigment protects skin cells from ultraviolet damage by absorbing UV radiation?
Melanin forms caps over keratinocyte nuclei and absorbs UV, protecting DNA. UV light is needed to make vitamin D, which gives no protection.
Differences in skin colour between people are mainly due to the amount and type of:
Carotene and blood haemoglobin add yellow and pink tones, and bilirubin causes jaundice. Differences between people come mainly from the amount and type of melanin melanocytes make.
Which of the following does NOT increase the body's heat production?
Clothing reduces heat loss by insulation but does not generate heat. Muscle activity, shivering and the thermic effect of food all raise metabolic heat.
Which type of substance crosses the intact epidermis most readily?
The keratinised, lipid-rich stratum corneum blocks water-soluble and large molecules. Lipid-soluble agents such as steroids can penetrate, which is why they are used in transdermal patches.
A rescued hiker's core temperature is measured rectally. Hypothermia is diagnosed once it drops below:
Hypothermia is a core temperature below 35 °C. Below 32 °C is moderate and below 28 °C is severe in common grading schemes.
Scattered goblet cells in the intestinal and respiratory epithelium produce:
Goblet cells are unicellular glands secreting mucin, which forms protective mucus. Amylase comes from salivary glands and pancreas; HCl from gastric parietal cells.
After a meal, blood glucose rises, insulin is released and glucose returns to normal. Most homeostatic controls, like this one, work by:
In negative feedback the response opposes the original change, restoring the set point. Positive feedback amplifies change and is used only in a few processes.
Which response helps the body CONSERVE heat rather than lose it?
Pilo-erection traps an air layer in furry animals and is a heat-conserving reflex. Skin vasodilation, sweating and lower heat production all help cool the body.
The total of all chemical reactions in the body, both building up and breaking down, is called:
Metabolism includes anabolism (synthesis) and catabolism (breakdown). Homeostasis is keeping the internal environment stable.
Which cation is present at the highest concentration inside cells?
Intracellular K+ is about 140-150 mmol/L, maintained by the Na+/K+-ATPase. Haemolysed samples therefore show falsely raised serum potassium.
Which anion is present at the highest concentration in extracellular fluid?
Plasma chloride is about 98-107 mmol/L, compared with about 22-29 mmol/L bicarbonate. Phosphate and protein anions dominate inside cells.
Which organelle breaks down worn-out organelles and engulfed material using acid hydrolases?
Lysosomes contain acid hydrolases that digest material within the cell, acting as its digestive system. Peroxisomes handle oxidative reactions and hydrogen peroxide.
In a serum electrolyte panel, which cation is present at the highest concentration?
Serum sodium is about 135-145 mmol/L, far above potassium (3.5-5.0 mmol/L), calcium and magnesium. Potassium predominates inside cells.