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UPMSP High School Human Science study materials
UPMSP High School Human Science study resources

UPMSP High School Human Science practice questions

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Question 1Skeletal, muscular and integumentary systems - structure, function and care

How many bones are present in the skeleton of a normal adult human being?

  1. 196
  2. 206 Correct answer.
  3. 186
  4. 216

Explanation

The adult human skeleton is conventionally described as having 206 bones, grouped into the axial skeleton (skull, vertebral column, ribs, sternum) and the appendicular skeleton (limbs and girdles). A newborn has far more separate bones, roughly 270, and the number falls during growth because many bones fuse, for example the sacral and coccygeal vertebrae.

Question 2Skeletal, muscular and integumentary systems - structure, function and care

Which structure attaches a skeletal muscle to a bone?

  1. Ligament
  2. Cartilage
  3. Periosteum
  4. Tendon Correct answer.

Explanation

A tendon is a strong cord of dense regular connective tissue that continues from the muscle's fascia and inserts into the periosteum of a bone, transmitting the pull of contraction. Ligaments have a different job, joining one bone to another at a joint. Cartilage is a flexible supporting tissue and the periosteum is the fibrous covering of bone itself.

Question 3Skeletal, muscular and integumentary systems - structure, function and care

Which organ forms the outer covering of the body and is the largest organ of the human body?

  1. Brain
  2. Liver
  3. Kidney
  4. Skin Correct answer.

Explanation

The skin covers the whole body surface, has an area of about 1.5 to 2 square metres in an adult, and is therefore counted as the largest organ. It performs protection, temperature regulation, sensation, excretion and vitamin D synthesis. The liver is the largest internal gland but not the largest organ overall.

Question 4Skeletal, muscular and integumentary systems - structure, function and care

Which type of muscle appears striated under the microscope yet contracts without conscious control?

  1. Skeletal muscle
  2. Smooth muscle
  3. Voluntary muscle
  4. Cardiac muscle Correct answer.

Explanation

Cardiac muscle fibres show cross-striations because their contractile proteins are arranged in sarcomeres, but the tissue is involuntary. It is regulated by the autonomic nerves and by its own pacemaker tissue, so the heart beats without conscious effort. Skeletal muscle is striated but voluntary, while smooth muscle is involuntary but not striated.

Question 5Skeletal, muscular and integumentary systems - structure, function and care

A young child shows soft, deformed leg bones and bow legs. Deficiency of which vitamin is the most likely cause?

  1. Vitamin C
  2. Vitamin D Correct answer.
  3. Vitamin A
  4. Vitamin K

Explanation

Vitamin D is needed for the absorption of calcium and phosphate from the intestine and for their deposition in the bone matrix. When it is deficient, the bones of a growing child remain soft and bend under body weight, producing the bow legs and other deformities of rickets. Sunlight on the skin allows the body to make this vitamin.

Question 6Skeletal, muscular and integumentary systems - structure, function and care

Which joint allows movement of a limb in all three planes, including rotation?

  1. Shoulder joint Correct answer.
  2. Neck pivot joint
  3. Elbow joint
  4. Wrist gliding joint

Explanation

In a ball-and-socket joint the rounded head of one bone fits into the cup-shaped cavity of another, so movement is possible in three planes as well as rotation. The shoulder and hip are the standard examples in the human body. Hinge, pivot and gliding joints each permit movement in only one or two directions.

Question 7Skeletal, muscular and integumentary systems - structure, function and care

According to the sliding filament theory, which two protein filaments interact to shorten a muscle fibre?

  1. Myosin and collagen
  2. Actin and myosin Correct answer.
  3. Calcium and actin
  4. Collagen and keratin

Explanation

In the sliding filament theory, myosin heads attach to actin filaments and form cross-bridges, then pull the actin filaments towards the centre of the sarcomere. The filaments themselves do not shorten; they slide over one another, and the sarcomere becomes shorter. Calcium ions and ATP are both needed to trigger and repeat this cycle.

Question 8Skeletal, muscular and integumentary systems - structure, function and care

A runner develops painful, tired muscles during a long sprint. Which change best explains this fatigue?

  1. Lactic acid build-up in muscle fibres Correct answer.
  2. Uric acid crystals depositing in joints
  3. Excess oxygen accumulating in muscle
  4. Calcium being released from bone tissue

Explanation

During vigorous exercise the oxygen supply cannot keep pace with demand, so muscle fibres respire anaerobically and glucose is broken down to lactic acid. The accumulating acid lowers the pH inside the fibre and interferes with contraction, producing the burning sensation, cramp and fatigue. Rest and oxygen allow the lactic acid to be removed and converted in the liver.

Question 9Skeletal, muscular and integumentary systems - structure, function and care

A woman past menopause fractures her hip after a minor fall, and scanning shows reduced bone density. Which change best explains her condition?

  1. Bone is broken down faster than it is rebuilt Correct answer.
  2. Nerve impulses fail to reach muscle fibres
  3. Bone matrix becomes over-mineralised
  4. Joint cartilage wears away at bone ends

Explanation

Bone is living tissue that is continuously remodelled by bone-destroying osteoclasts and bone-forming osteoblasts. After menopause the fall in oestrogen speeds up resorption more than formation, so bone mass and strength decline and a slight fall can fracture the hip. Adequate calcium, vitamin D and weight-bearing exercise help slow this loss.

Question 10Skeletal, muscular and integumentary systems - structure, function and care

Which pigment produced in the epidermis protects deeper skin cells by absorbing ultraviolet radiation?

  1. Melanin Correct answer.
  2. Sebum
  3. Keratin
  4. Collagen

Explanation

Melanin is produced by melanocytes in the lower epidermis and passed to surrounding keratinocytes, where it absorbs ultraviolet light and reduces damage to DNA. Production increases after repeated sun exposure, which is why skin tans. Keratin is a protective protein, collagen gives the dermis strength, and sebum is an oily secretion of sebaceous glands.

Question 11Skeletal, muscular and integumentary systems - structure, function and care

Which bone cell is primarily responsible for secreting new bone matrix during growth and repair?

  1. Osteocyte
  2. Osteoblast Correct answer.
  3. Osteoclast
  4. Chondrocyte

Explanation

Osteoblasts secrete collagen-rich osteoid and promote its mineralisation, so they build new bone matrix. Osteocytes are mature maintenance cells, osteoclasts resorb bone, and chondrocytes form cartilage.

Question 12Skeletal, muscular and integumentary systems - structure, function and care

Which layer of the skin is avascular and receives nutrients mainly by diffusion from the layer beneath it?

  1. Epidermis Correct answer.
  2. Periosteum
  3. Hypodermis
  4. Dermis

Explanation

The epidermis lacks blood vessels, so its cells are nourished by substances diffusing from capillaries in the dermis. The dermis is vascular, the hypodermis is mainly adipose tissue, and periosteum covers bone.

Question 13Skeletal, muscular and integumentary systems - structure, function and care

What is the basic contractile unit of a skeletal muscle fibre called?

  1. Motor unit
  2. Sarcoplasmic reticulum
  3. Sarcomere Correct answer.
  4. Myofibril

Explanation

A sarcomere is the segment between two Z lines and contains the actin and myosin filaments whose interaction shortens the muscle. A myofibril is a chain of sarcomeres, a motor unit is a neuron plus the fibres it supplies, and the sarcoplasmic reticulum stores calcium.

Question 14Skeletal, muscular and integumentary systems - structure, function and care

During excitation-contraction coupling in skeletal muscle, what is the direct effect of calcium ions released from the sarcoplasmic reticulum?

  1. They break down acetylcholine in the synaptic cleft.
  2. They bind troponin and expose actin's myosin-binding sites. Correct answer.
  3. They attach to myosin heads and hydrolyse ATP.
  4. They enter the muscle nucleus and promote protein synthesis.

Explanation

Calcium binds the troponin complex on the thin filament, which moves tropomyosin away from actin's myosin-binding sites. This allows cross-bridge cycling to begin. Calcium does not split ATP itself, enter the nucleus in this rapid response, or break down acetylcholine.

Question 15Skeletal, muscular and integumentary systems - structure, function and care

Which joint type is represented by the sutures between the bones of the skull?

  1. Hinge
  2. Suture Correct answer.
  3. Saddle
  4. Pivot

Explanation

Sutures are fibrous joints in which dense connective tissue unites the skull bones, and they normally permit little or no movement. Saddle, hinge and pivot joints are synovial joints that allow movement.

Question 16Skeletal, muscular and integumentary systems - structure, function and care

When the biceps brachii contracts to flex the elbow, what happens to the triceps brachii?

  1. It contracts strongly to assist elbow flexion.
  2. It generates force equal to that of the biceps.
  3. It relaxes and lengthens as it is stretched. Correct answer.
  4. It contracts isometrically without changing length.

Explanation

Skeletal muscles usually work in antagonistic pairs, so the triceps must relax and be stretched while the biceps shortens. If both contracted strongly, elbow flexion would be resisted. The triceps contracts to extend the elbow, not to assist flexion.

Question 17Skeletal, muscular and integumentary systems - structure, function and care

On a hot day, which combination of skin responses increases heat loss?

  1. Vasodilation of dermal arterioles and increased sweating Correct answer.
  2. Increased sebum secretion and reduced skin blood flow
  3. Vasoconstriction of dermal arterioles and reduced sweating
  4. Contraction of arrector pili muscles and shivering

Explanation

Cutaneous vasodilation brings warm blood to the skin surface, and increased sweating adds evaporative cooling. Together they raise heat loss. Vasoconstriction and shivering conserve or generate heat, so they act in the opposite direction.

Question 18Skeletal, muscular and integumentary systems - structure, function and care

A long bone of an adult increases slightly in diameter without any increase in length. Which cellular activity directly explains this change?

  1. Osteoclast resorption along the endosteum only
  2. Chondrocyte division at the epiphyseal plate
  3. Osteoblast deposition beneath the periosteum Correct answer.
  4. Calcitonin-driven calcium release from bone

Explanation

Increase in bone diameter is appositional growth: osteoblasts beneath the periosteum deposit new circumferential lamellae. Epiphyseal plate activity increases length, not diameter, and osteoclasts mainly enlarge the medullary cavity. Calcitonin lowers blood calcium and does not directly add bone width.

Question 19Skeletal, muscular and integumentary systems - structure, function and care

At the neuromuscular junction of a skeletal muscle fibre, which sequence correctly describes transmission?

  1. Acetylcholine diffuses into the muscle fibre and binds directly to troponin.
  2. The motor neuron action potential crosses gap junctions into the muscle fibre.
  3. Norepinephrine binds alpha receptors on the sarcolemma and triggers muscle contraction.
  4. Acetylcholine binds receptors on the motor end plate and triggers a muscle action potential. Correct answer.

Explanation

The motor neuron releases acetylcholine, which binds nicotinic receptors on the motor end plate. This depolarisation generates a muscle action potential that spreads along the sarcolemma and triggers contraction. Acetylcholine does not enter the fibre to bind troponin, and skeletal muscle fibres are not linked to motor neurons by gap junctions.

Question 20Skeletal, muscular and integumentary systems - structure, function and care

A superficial abrasion injures only the epidermis and heals without a scar. Which feature of the epidermis best explains this outcome?

  1. It contains osteoblasts that deposit new bone matrix.
  2. Basal keratinocytes can divide and replace lost cells. Correct answer.
  3. It contains abundant blood vessels that rapidly rebuild tissue.
  4. Its collagen fibres are arranged in parallel bundles.

Explanation

The epidermis is stratified and its basal layer contains stem cells that divide and replace cells lost from the surface. Because only the epidermis is damaged, regeneration restores it without deep scarring. The epidermis has no blood vessels or osteoblasts, and collagen bundles belong mainly to the dermis.

Question 21Skeletal, muscular and integumentary systems - structure, function and care

Which oily secretion released by the sebaceous glands lubricates the skin and hair?

  1. Keratin
  2. Sweat
  3. Sebum Correct answer.
  4. Melanin

Explanation

Sebaceous glands secrete sebum, a lipid-rich substance that coats the skin and hair, slows water loss, and helps keep the surface supple. Sebum also contributes mildly to limiting the growth of some surface microbes. Sweat is produced by sweat glands, not sebaceous glands.

Question 22Skeletal, muscular and integumentary systems - structure, function and care

Red bone marrow inside the spongy bone of a child's long bone is damaged by disease. Which function will be most directly lost?

  1. Storage of triglycerides as an energy reserve
  2. Formation of blood cells Correct answer.
  3. Production of collagen bundles in tendons
  4. Secretion of synovial fluid into the joint cavity

Explanation

Red bone marrow contains blood-forming stem cells and is the main site of haematopoiesis in a child's long bones. Damage to this marrow therefore reduces the production of red blood cells, white blood cells and platelets. Triglyceride storage occurs mainly in yellow marrow, while synovial fluid and tendon collagen are produced by other tissues.

Question 23Skeletal, muscular and integumentary systems - structure, function and care

A person stands and pushes hard against a solid wall. The arm muscles tense visibly, but the elbow joint does not move. Which type of contraction is occurring?

  1. Isotonic concentric contraction
  2. Isokinetic contraction
  3. Isotonic eccentric contraction
  4. Isometric contraction Correct answer.

Explanation

In an isometric contraction, muscle tension increases while the muscle length and joint angle stay essentially unchanged, as when pushing against an immovable wall. Isotonic contractions involve movement of a load, and isokinetic contraction is a controlled constant-velocity movement used in specialised testing and rehabilitation rather than this static effort.

Question 24Skeletal, muscular and integumentary systems - structure, function and care

In a resting skeletal muscle fibre, which protein lies along the actin filament and blocks the myosin-binding sites?

  1. Troponin
  2. Tropomyosin Correct answer.
  3. Myosin head
  4. Titin

Explanation

Tropomyosin is a long fibrous protein that runs along the groove of the actin filament and covers the myosin-binding sites when the muscle is relaxed. When calcium binds troponin, the troponin-tropomyosin complex shifts and exposes those sites so cross-bridges can form. Troponin regulates this shift but is not the protein that physically covers the binding sites.

Question 25Digestive system, nutrients and balanced diet

Which enzyme present in human saliva starts the breakdown of starch into simpler sugars?

  1. Salivary amylase Correct answer.
  2. Pepsin
  3. Trypsin
  4. Lingual lipase

Explanation

Starch is a polysaccharide, and salivary amylase (also called ptyalin) hydrolyses its glycosidic bonds in the mouth to give maltose. This is why a piece of bread tastes slightly sweet if it is chewed for a long time. Proteases such as pepsin and trypsin act on proteins lower down the alimentary canal, so they cannot begin starch digestion in the mouth.

Question 26Digestive system, nutrients and balanced diet

Which nutrient is the quickest source of energy that body cells can use at once, for example during heavy exercise?

  1. Fats
  2. Dietary fibre
  3. Carbohydrates Correct answer.
  4. Proteins

Explanation

Carbohydrates are digested into glucose, which is absorbed rapidly and can be oxidised at once or released from liver and muscle glycogen stores. Fats store more than twice as much energy per gram, but they are mobilised more slowly and therefore are not the quickest source during sudden heavy work. Proteins are mainly used for growth, repair and enzyme formation.

Question 27Digestive system, nutrients and balanced diet

A person who cannot see properly in dim light, a condition called night blindness, is most likely deficient in which vitamin?

  1. Vitamin K
  2. Vitamin B1
  3. Vitamin C
  4. Vitamin A Correct answer.

Explanation

Vitamin A is needed to make rhodopsin, the light-sensitive pigment of the rods in the retina. When vitamin A is deficient, the rods cannot respond to dim light and night blindness develops, later followed by dryness of the eye (xerophthalmia). Vitamin C and vitamin B1 are not involved in rhodopsin formation, and vitamin K acts in blood clotting.

Question 28Digestive system, nutrients and balanced diet

A child eats plenty of energy-rich food but very little protein, and develops a swollen abdomen, thin hair and poor growth. Which deficiency disease matches this picture?

  1. Scurvy
  2. Rickets
  3. Marasmus
  4. Kwashiorkor Correct answer.

Explanation

Kwashiorkor is protein-energy malnutrition in which protein intake is too low while energy intake is nearly adequate. Low plasma protein reduces blood osmotic pressure, so fluid collects in the tissues and the child develops oedema of the abdomen and legs, along with thin hair and slow growth. Marasmus differs because there is severe shortage of both protein and energy, giving extreme wasting without oedema.

Question 29Digestive system, nutrients and balanced diet

In which part of the human alimentary canal is most of the digested food absorbed into the blood?

  1. Large intestine
  2. Small intestine Correct answer.
  3. Oesophagus
  4. Stomach

Explanation

The small intestine, especially its middle part the ileum, contains millions of finger-like projections called villi, whose microvilli give an enormous surface area. Each villus has blood capillaries and a lymph vessel (lacteal), so amino acids and monosaccharides enter the blood and fatty acids enter the lymph. Absorption of digested food therefore takes place mainly here, while the large intestine reabsorbs chiefly water and salts.

Question 30Digestive system, nutrients and balanced diet

Bile is produced by the liver and stored in the gall bladder. What is its main action in the digestion of food?

  1. It converts starch into maltose
  2. It digests proteins into amino acids
  3. It carries glucose across the intestinal wall
  4. It breaks fats into tiny droplets Correct answer.

Explanation

Bile salts lower the surface tension between fat and water and emulsify large fat globules into many tiny droplets. This greatly increases the surface area on which pancreatic lipase can act, so fats are digested faster. Bile contains no digestive enzymes itself, and it also helps to neutralise the acidic chyme entering the duodenum.

Question 31Digestive system, nutrients and balanced diet

A person can swallow food even while lying flat, and the food still reaches the stomach. What pushes the food along the oesophagus?

  1. Waves of muscular contraction in the wall Correct answer.
  2. Fine hair-like cilia lining the tube
  3. Gravity pulling the food downwards
  4. Air pressure from the lungs

Explanation

The walls of the oesophagus contain smooth muscle that contracts in rhythmic waves behind the food bolus; this movement is called peristalsis. Because the push comes from the muscular wall and not from gravity, food can travel to the stomach in any body position. The same reflex moves food through the stomach and intestine.

Question 32Digestive system, nutrients and balanced diet

A patient takes a drug that strongly reduces hydrochloric acid secretion in the stomach. Which digestive enzyme will be most affected?

  1. Salivary amylase
  2. Trypsin
  3. Pancreatic lipase
  4. Pepsin Correct answer.

Explanation

Gastric chief cells secrete inactive pepsinogen, which is converted into active pepsin only by hydrochloric acid, and pepsin works best at a pH of about 1.5 to 2. If acid secretion falls, activation of pepsinogen and the acidic condition the enzyme needs are both lost, so protein digestion in the stomach is disturbed. Trypsin and pancreatic lipase work in the alkaline small intestine and would not be harmed by less stomach acid.

Question 33Digestive system, nutrients and balanced diet

Which vitamin is formed in human skin when it is exposed to sunlight and is needed for the absorption of calcium?

  1. Vitamin C
  2. Vitamin A
  3. Vitamin D Correct answer.
  4. Vitamin B12

Explanation

Ultraviolet rays of sunlight convert a cholesterol derivative in the skin into vitamin D, which the liver and kidney then modify into its active form. This vitamin increases calcium absorption from the intestine and helps deposit calcium and phosphate in bone. Its deficiency causes rickets in children and osteomalacia in adults.

Question 34Digestive system, nutrients and balanced diet

A balanced diet must contain some fat even when carbohydrates supply most of the energy. Which reason best explains this?

  1. Fat is the only nutrient that can be stored in the body
  2. Fat stops proteins from being digested in the stomach
  3. Fat is needed to absorb vitamins A, D, E and K and to supply essential fatty acids Correct answer.
  4. Fat supplies the nitrogen needed for making enzymes

Explanation

Vitamins A, D, E and K are fat-soluble, so they are absorbed along with dietary fat and bile salts; a fat-free diet therefore leads to deficiency of these vitamins. Fat also provides linoleic and linolenic acids, which the human body cannot synthesise and which must come from food. In addition, fat is an energy store of about 9 kcal per gram and protects and insulates organs.

Question 35Digestive system, nutrients and balanced diet

A person in a hilly village uses only rock salt and never eats iodised salt, seaweed or sea fish. Which deficiency disease is most likely to develop because of this diet?

  1. Scurvy, caused by low vitamin C intake
  2. Goitre, caused by low iodine intake Correct answer.
  3. Rickets, caused by low vitamin D intake
  4. Beriberi, caused by low thiamine intake

Explanation

Iodine is needed by the thyroid gland to make thyroid hormones. When iodine intake stays low, the thyroid enlarges as a visible swelling called goitre. Iodised salt supplies the missing iodine and prevents this deficiency disease.

Question 36Digestive system, nutrients and balanced diet

A balanced diet includes coarse cereals, whole pulses, fruits and vegetables even though they supply little energy. Which function is mainly served by the fibre in these foods?

  1. It adds bulk that helps the large intestine retain water and move waste Correct answer.
  2. It supplies essential amino acids for muscle repair
  3. It provides most of the body's calcium for bones
  4. It is converted into vitamin A in the liver

Explanation

Dietary fibre is mainly cellulose that human enzymes cannot digest. It adds bulk, holds water and helps the large intestine move waste out regularly. It does not supply amino acids, vitamins or minerals in significant amounts.

Question 37Digestive system, nutrients and balanced diet

During chewing, which teeth are best adapted for cutting and biting off a piece of food rather than grinding it?

  1. Molars
  2. Incisors Correct answer.
  3. Premolars
  4. Canines

Explanation

Incisors are chisel-shaped front teeth used for cutting and biting food. Molars and premolars have broad surfaces for crushing and grinding, while canines are pointed for tearing.

Question 38Digestive system, nutrients and balanced diet

The pancreas sends digestive juice into the small intestine. Which combination of enzymes does this juice normally contain?

  1. Bile salts, mucus and vitamin B12
  2. Salivary amylase, maltase and ptyalin
  3. Pepsin, rennin and hydrochloric acid
  4. Trypsin, pancreatic amylase and lipase Correct answer.

Explanation

Pancreatic juice is alkaline and contains trypsin for proteins, pancreatic amylase for starch and lipase for fats. These enzymes enter the small intestine through the pancreatic duct and act there.

Question 39Digestive system, nutrients and balanced diet

After a protein-rich meal of dal and paneer is digested, in what form are most of its proteins absorbed into the blood?

  1. Glycerol and mineral salts
  2. Fatty acids and glycerol
  3. Glucose molecules
  4. Amino acids Correct answer.

Explanation

Proteins are broken down by proteases into amino acids, which are absorbed through the small intestine into the blood. Fatty acids and glycerol come from fats, while glucose comes from carbohydrates.

Question 40Digestive system, nutrients and balanced diet

The lining of the small intestine has millions of finger-like villi. Which combination best explains how villi improve absorption?

  1. They increase surface area and have capillaries near the surface Correct answer.
  2. They store bile and release it when fatty food arrives
  3. They push undigested food into the large intestine by peristalsis
  4. They secrete hydrochloric acid and pepsin to digest protein

Explanation

Villi are finger-like folds that greatly increase the inner surface area of the small intestine. Each villus has a rich network of blood capillaries close to the surface, so digested nutrients can diffuse into the blood quickly.

Question 41Digestive system, nutrients and balanced diet

In which part of the human alimentary canal is most of the remaining water absorbed from undigested food, turning it into semi-solid faeces?

  1. Stomach
  2. Mouth
  3. Oesophagus
  4. Large intestine Correct answer.

Explanation

The large intestine absorbs most of the remaining water from undigested food. As water is removed, the waste becomes semi-solid faeces before being stored in the rectum.

Question 42Digestive system, nutrients and balanced diet

A midday meal contains 60 g carbohydrate, 20 g protein and 10 g fat. Using 4 kcal per gram for carbohydrate and protein, and 9 kcal per gram for fat, what energy does the meal provide?

  1. 440 kcal
  2. 360 kcal
  3. 410 kcal Correct answer.
  4. 320 kcal

Explanation

Carbohydrate supplies 60 × 4 = 240 kcal and protein supplies 20 × 4 = 80 kcal. Fat supplies 10 × 9 = 90 kcal. Adding these gives 240 + 80 + 90 = 410 kcal.

Question 43Digestive system, nutrients and balanced diet

A person chews a piece of bread and swallows it. Which sequence correctly traces the main enzymes acting on its starch as it moves through the alimentary canal?

  1. Salivary amylase → pancreatic amylase → maltase Correct answer.
  2. Bile → pepsin → trypsin
  3. Pepsin → salivary amylase → lipase
  4. Lipase → maltase → hydrochloric acid

Explanation

Starch digestion begins in the mouth, where salivary amylase breaks starch into maltose. Pancreatic amylase continues this in the small intestine, and maltase finally breaks maltose into glucose.

Question 44Digestive system, nutrients and balanced diet

The stomach secretes hydrochloric acid and pepsin, yet its own walls are usually not digested. Which secretion protects the stomach lining from this action?

  1. Mucus from the stomach lining Correct answer.
  2. Bile from the liver
  3. Pancreatic juice from the pancreas
  4. Saliva from salivary glands

Explanation

The stomach lining secretes mucus, which forms a protective layer over the inner wall. This layer reduces damage from hydrochloric acid and pepsin so the stomach is not digested by its own secretions.

Question 45Digestive system, nutrients and balanced diet

A sailor on a long voyage eats no fresh fruit or vegetables and develops bleeding gums and slow-healing wounds. Which nutrient is most likely lacking in his diet?

  1. Vitamin A
  2. Vitamin D
  3. Iron
  4. Vitamin C Correct answer.

Explanation

Vitamin C is needed for collagen synthesis, which keeps gums, skin and blood vessels healthy; a lack causes scurvy with bleeding gums and poor wound healing. Vitamin A is linked to vision, vitamin D to calcium absorption, and iron to haemoglobin, so none of these matches scurvy.

Question 46Digestive system, nutrients and balanced diet

Most glucose and amino acids pass into blood capillaries inside the villi, but the products of fat digestion are absorbed mainly into which structures?

  1. The gastric pits of the stomach lining
  2. The hepatic portal vein, before passing to the liver
  3. The bile canaliculi of the liver
  4. Lacteals, the lymph vessels inside each villus Correct answer.

Explanation

Fat digestion products, mainly fatty acids and glycerol, are absorbed by the villi and enter the lacteals, which are lymph capillaries, rather than the blood capillaries. Glucose and amino acids enter the blood capillaries and travel by the hepatic portal vein to the liver. Gastric pits and bile canaliculi are not absorption routes for fats.

Question 47Digestive system, nutrients and balanced diet

A teenager eats iron-rich spinach daily but drinks strong tea with every meal and avoids citrus fruit; blood tests show anaemia. The doctor advises lemon juice with meals and tea between meals. Which explanation best supports this advice?

  1. Tea supplies calcium that competes with iron, and lemon supplies iodine.
  2. Lemon juice neutralises stomach acid needed to make haemoglobin.
  3. Vitamin C in lemon juice is converted into haemoglobin in the stomach.
  4. Vitamin C aids iron absorption, while tea tannins hinder it. Correct answer.

Explanation

Vitamin C in citrus fruit promotes the absorption of non-haem iron from plant foods, while tannins in strong tea form complexes that inhibit iron absorption. Separating tea from meals and adding lemon juice therefore improves iron uptake and helps correct anaemia. Vitamin C is not converted into haemoglobin, and lemon juice does not neutralise stomach acid in a way that makes haemoglobin.

Question 48Digestive system, nutrients and balanced diet

A labourer and an office clerk of the same age and body mass eat meals with the same total energy. The labourer loses weight, while the clerk gains weight. Which change is most appropriate?

  1. The labourer needs more energy-giving carbohydrate and fat, while the clerk needs less energy-dense food. Correct answer.
  2. Both should increase protein to the same high level, because protein supplies the extra energy for muscular work.
  3. Both should eat identical meals, because energy requirement depends only on body mass and age.
  4. The clerk should eat more fat, and the labourer should eat less carbohydrate to balance the extra work.

Explanation

Energy requirement rises with physical activity, so a labourer doing heavy work needs more energy from carbohydrate and fat than a clerk doing desk work. Eating the same intake leads to weight loss in the labourer and weight gain in the clerk. Protein is mainly for growth and repair, not the main fuel for muscular work, and requirement is not fixed by body mass alone.

Question 49Respiratory and circulatory systems - gas exchange, blood and lymph

In the human lungs, exchange of oxygen and carbon dioxide between air and blood takes place across the walls of which structures?

  1. Alveoli Correct answer.
  2. Bronchi
  3. Trachea
  4. Pleura

Explanation

Alveoli are tiny air sacs whose walls are one cell thick and are wrapped in a dense net of capillaries, giving a very large surface area and a short diffusion path. Oxygen diffuses into the blood and carbon dioxide diffuses out across this thin alveolar-capillary membrane. The bronchi and trachea only conduct air, and the pleura is the covering membrane of the lung.

Question 50Respiratory and circulatory systems - gas exchange, blood and lymph

Most of the oxygen carried by blood from the lungs to the tissues is transported in which form?

  1. Dissolved in plasma water
  2. Bound to haemoglobin Correct answer.
  3. Bound to plasma albumin
  4. As bicarbonate ions

Explanation

Roughly 97 per cent of oxygen is carried inside red blood cells combined with haemoglobin, and only a small amount dissolves physically in plasma. Because each haemoglobin molecule binds four oxygen molecules, blood can carry about 20 mL of oxygen per 100 mL, far more than plasma could dissolve on its own. Bicarbonate and albumin are carriers for carbon dioxide, not oxygen.