FBISE Examinations Biology (HSSC) Syllabus

Distinguish between competitive and non-competitive enzyme inhibition.

A competitive inhibitor resembles the substrate and binds to the active site, blocking the substrate; a non-competitive inhibitor binds elsewhere (allosteric site), changing the active site's shape so substrate cannot react.

How can the effect of a competitive inhibitor be reduced?

By increasing the substrate concentration, since substrate and inhibitor compete for the active site.

What is a cofactor and a coenzyme?

A cofactor is a non-protein helper required for enzyme activity; inorganic cofactors are metal ions (e.g., Zn2+, Mg2+), while organic cofactors are called coenzymes (often derived from vitamins, e.g., NAD).

Define autotrophic nutrition.

A mode of nutrition in which an organism makes its own organic food from simple inorganic substances (CO2 and water), e.g., green plants by photosynthesis.

Define heterotrophic nutrition and name its main types.

Nutrition in which an organism obtains ready-made organic food from other organisms; main types are holozoic, saprotrophic (saprophytic), and parasitic nutrition.

What is saprotrophic (saprophytic) nutrition?

Nutrition in which an organism (e.g., fungi, many bacteria) feeds on dead and decaying organic matter by secreting enzymes onto it and absorbing the digested products.

What is parasitic nutrition?

Nutrition in which an organism (parasite) lives on or inside another living organism (host) and obtains food from it, usually harming the host.

List the four main processes of holozoic nutrition in their correct order.

Ingestion, digestion, absorption (and assimilation), and egestion.

Name the parts of the human alimentary canal in order from mouth to anus.

Mouth (buccal cavity), pharynx, oesophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (colon), rectum, and anus.

Which enzyme is present in saliva, and what does it digest?

Salivary amylase (ptyalin), which begins the digestion of starch into maltose.

What three substances are found in gastric juice and what is the role of each?

Pepsin (digests proteins into peptides), hydrochloric acid (provides acidic pH and kills bacteria), and mucus (protects the stomach lining).

What is the role of bile in digestion, and where is it produced and stored?

Bile emulsifies fats into small droplets to increase surface area for lipase action; it is produced by the liver and stored in the gall bladder.

Name three enzymes in pancreatic juice and the food each acts on.

Pancreatic amylase (starch), trypsin (proteins), and pancreatic lipase (fats).

Where does most absorption of digested food occur, and what structures increase its surface area?

In the small intestine (mainly the ileum); its surface area is greatly increased by villi and microvilli.

What is a villus and what feature aids absorption of fats versus other nutrients?

A villus is a finger-like projection of the small intestine lining; amino acids and glucose pass into its blood capillaries, while fatty acids and glycerol enter the central lacteal (lymph vessel).

What is the main function of the large intestine (colon)?

Absorption of water and mineral salts from undigested material, forming and storing faeces.

What causes marasmus and what causes kwashiorkor?

Marasmus is caused by a severe deficiency of total calories (energy and protein), while kwashiorkor is caused mainly by a severe protein deficiency.

What deficiency causes the disease scurvy, and what causes rickets?

Scurvy is caused by a deficiency of vitamin C; rickets is caused by a deficiency of vitamin D (or calcium), leading to soft, deformed bones.

Distinguish between obesity and anorexia nervosa as disorders of nutrition.

Obesity is excess body fat from consuming more calories than are used; anorexia nervosa is a psychological eating disorder of self-starvation due to an intense fear of gaining weight.

How do gases enter and leave plant leaves, and what controls this exchange?

Gases (CO2 and O2) diffuse through tiny pores called stomata, which are opened and closed by guard cells.

How does gaseous exchange differ in a plant during the day versus at night?

In the day, photosynthesis dominates so net CO2 is taken in and O2 released; at night only respiration occurs, so O2 is taken in and CO2 released.

Through which structures do woody stems and roots carry out gaseous exchange?

Woody stems exchange gases through lenticels, and roots exchange gases through root hairs and air spaces in the soil.

List the parts of the human respiratory tract through which air passes, in order.

Nostrils/nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli of the lungs.

What structural features make the alveoli efficient for gaseous exchange?

They have a very large surface area, extremely thin (one-cell-thick) moist walls, and a rich network of capillaries, giving a short diffusion distance.

Describe the roles of the diaphragm and intercostal muscles during inhalation.

During inhalation the diaphragm contracts and flattens and the external intercostal muscles contract to raise the ribs, increasing thoracic volume and drawing air in.

How is most carbon dioxide transported in the blood?

Most carbon dioxide is transported as bicarbonate ions (HCO3-) dissolved in the blood plasma; smaller amounts are carried bound to haemoglobin and dissolved in plasma.

What is asthma and what happens to the airways during an attack?

Asthma is an allergic respiratory disorder in which the bronchioles become narrowed due to muscle constriction, inflammation, and excess mucus, causing difficulty in breathing and wheezing.

What is emphysema and what is its main cause?

Emphysema is a lung disorder in which the walls of the alveoli break down, reducing surface area for gas exchange; it is most commonly caused by cigarette smoking.

How does water enter root hairs and move up to the leaves in a plant?

Water enters root hairs by osmosis and is carried up through the xylem to the leaves, mainly by the transpiration pull created as water evaporates from the leaves.

Distinguish between the functions of xylem and phloem in plant transport.

Xylem transports water and dissolved minerals upward from roots to leaves; phloem transports manufactured food (sugars) from leaves to other parts in a process called translocation.