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BGCSE BSSE Biology 1428 study materials
BGCSE BSSE Biology 1428 study resources

BGCSE BSSE Biology 1428 practice questions

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Question 1Cells and Cell Biology

Which organelle is the main site of ATP production in a eukaryotic cell?

  1. Mitochondrion Correct answer.
  2. Golgi apparatus
  3. Lysosome
  4. Ribosome

Explanation

Mitochondria carry out aerobic respiration, using the electron transport chain across the inner membrane to generate most of the cell's ATP. Ribosomes build proteins and lysosomes digest material, so neither produces ATP on this scale.

Question 2Cells and Cell Biology

A plant cell is placed in pure water. What happens to the cell?

  1. It becomes turgid as water enters the vacuole Correct answer.
  2. It bursts because the wall cannot resist pressure
  3. It shrinks as water leaves the cell
  4. It shows no change because water cannot cross the membrane

Explanation

Pure water has a higher water potential than the cell sap, so water enters by osmosis and the vacuole swells. The rigid cellulose wall resists further expansion, making the cell turgid rather than bursting.

Question 3Cells and Cell Biology

Which structure controls the movement of substances into and out of a cell?

  1. Cell wall
  2. Nucleolus
  3. Cytoplasm
  4. Cell surface membrane Correct answer.

Explanation

The cell surface membrane is a phospholipid bilayer with embedded proteins that regulates which substances enter or leave. It is partially permeable, unlike the freely permeable cell wall.

Question 4Cells and Cell Biology

Which molecule carries the genetic instructions from the nucleus to a ribosome?

  1. Deoxyribose
  2. Transfer RNA
  3. Messenger RNA Correct answer.
  4. Phospholipid

Explanation

Messenger RNA is transcribed from DNA in the nucleus and carries the base sequence to the ribosome for translation. Transfer RNA brings amino acids but does not carry the message itself.

Question 5Cells and Cell Biology

Which process requires energy from ATP to move substances against a concentration gradient?

  1. Osmosis
  2. Active transport Correct answer.
  3. Diffusion
  4. Facilitated diffusion

Explanation

Active transport uses carrier proteins and ATP hydrolysis to move ions or molecules against their concentration gradient. Diffusion, osmosis and facilitated diffusion are all passive and rely on the gradient itself.

Question 6Cells and Cell Biology

What is the function of the chloroplast in a plant cell?

  1. Storing starch as an insoluble grain
  2. Releasing energy from glucose by respiration
  3. Synthesising proteins from amino acids
  4. Absorbing light energy for photosynthesis Correct answer.

Explanation

Chloroplasts contain chlorophyll and the thylakoid membranes that capture light energy for photosynthesis. Respiration occurs mainly in mitochondria, so chloroplasts are not the energy-releasing organelles.

Question 7Cells and Cell Biology

A cell is observed with a light microscope. The image length is 40 mm and the actual length is 0.05 mm. What is the magnification?

  1. 80
  2. 2000
  3. 800 Correct answer.
  4. 200

Explanation

Magnification equals image size divided by actual size, so 40 mm divided by 0.05 mm gives 800. The units must match before dividing, and both lengths here are in millimetres.

Question 8Cells and Cell Biology

Why do cells with a high rate of protein secretion, such as pancreas cells, contain many ribosomes and a large Golgi apparatus?

  1. They rely on these organelles for ATP production
  2. They must synthesise and package large amounts of protein Correct answer.
  3. They use them to break down toxic hydrogen peroxide
  4. They need extra DNA for rapid cell division

Explanation

Secretory cells need many ribosomes to translate protein and an extensive Golgi apparatus to modify and package it into vesicles. Organelle abundance reflects the cell's specialised function, not a need for extra DNA.

Question 9Cells and Cell Biology

A red blood cell is placed in a concentrated salt solution. Which change is expected?

  1. It becomes turgid
  2. It gains water and swells
  3. It keeps the same volume
  4. It loses water and shrinks Correct answer.

Explanation

The external solution has a lower water potential than the cytoplasm, so water leaves the cell by osmosis. An animal cell without a wall shrinks and may become crenated.

Question 10Cells and Cell Biology

Which statement best describes the fluid mosaic model of the membrane?

  1. A rigid double layer of protein surrounds a lipid core
  2. Protein molecules form a solid sheet with pores between them
  3. A single layer of phospholipids is coated with carbohydrate
  4. Proteins float within or span a fluid phospholipid bilayer Correct answer.

Explanation

The model describes phospholipids moving laterally as a fluid bilayer, with proteins embedded within or spanning it like tiles in a mosaic. This fluidity allows membrane proteins to move and supports transport and signalling.

Question 11Cells and Cell Biology

During which stage of mitosis do chromosomes line up along the equator of the cell?

  1. Metaphase Correct answer.
  2. Telophase
  3. Anaphase
  4. Prophase

Explanation

In metaphase the chromosomes align at the cell equator and spindle fibres attach to their centromeres. This alignment ensures that sister chromatids are separated evenly in the following anaphase.

Question 12Cells and Cell Biology

An enzyme is added to a reaction mixture, and the rate of reaction increases. Which explanation is correct?

  1. The enzyme changes the products formed by the reaction
  2. The enzyme lowers the activation energy needed for the reaction Correct answer.
  3. The enzyme raises the temperature of the mixture
  4. The enzyme increases the energy released by the reaction

Explanation

Enzymes are biological catalysts that provide an alternative pathway with a lower activation energy, so more substrate molecules can react at a given temperature. They do not alter the overall energy change or the nature of the products.

Question 13Cells and Cell Biology

A student views onion epidermis cells. Which feature distinguishes these plant cells from human cheek cells?

  1. A cell surface membrane
  2. Cytoplasm
  3. A nucleus
  4. A cellulose cell wall Correct answer.

Explanation

Plant cells have a cellulose cell wall outside the membrane, which gives a regular shape and provides support. Both onion and cheek cells possess a nucleus, a membrane and cytoplasm.

Question 14Cells and Cell Biology

Which statement correctly compares DNA and RNA?

  1. DNA is single-stranded, while RNA is always double-stranded
  2. DNA contains deoxyribose and thymine, while RNA contains ribose and uracil Correct answer.
  3. DNA is found only in the cytoplasm, while RNA is found only in the nucleus
  4. DNA contains uracil, while RNA contains thymine

Explanation

DNA has deoxyribose sugar and the base thymine, whereas RNA has ribose and uracil in place of thymine. DNA is normally double-stranded and located mainly in the nucleus.

Question 15Cells and Cell Biology

A cell is treated with a drug that prevents ATP synthesis. Which process would be affected first?

  1. Osmosis of water into the vacuole
  2. Active transport of ions across the membrane Correct answer.
  3. Diffusion of oxygen into the cell
  4. Movement of carbon dioxide out of the cell

Explanation

Active transport depends directly on ATP hydrolysis by carrier proteins, so blocking ATP synthesis stops it quickly. Diffusion and osmosis are passive and continue as long as a gradient exists.

Question 16Cells and Cell Biology

Why are cells generally small in size?

  1. A small volume gives a large surface area to volume ratio for exchange Correct answer.
  2. Small cells contain fewer organelles than large cells
  3. Small cells avoid the need for a nucleus
  4. Small cells do not need a cell membrane

Explanation

As a cell grows, its volume increases faster than its surface area, reducing the surface area to volume ratio. Small cells therefore exchange gases and nutrients efficiently enough to meet their metabolic demands.

Question 17Cells and Cell Biology

A section of tissue is 0.02 mm thick. What is this thickness in micrometres?

  1. 2 µm
  2. 0.2 µm
  3. 200 µm
  4. 20 µm Correct answer.

Explanation

One millimetre equals 1000 micrometres, so 0.02 mm equals 0.02 × 1000 = 20 µm. Converting between millimetres and micrometres requires multiplying by one thousand.

Question 18Cells and Cell Biology

A cell has a solute potential of −400 kPa and a pressure potential of +150 kPa. What is its water potential?

  1. +250 kPa
  2. −250 kPa Correct answer.
  3. +550 kPa
  4. −550 kPa

Explanation

Water potential equals solute potential plus pressure potential, so −400 kPa + 150 kPa = −250 kPa. The pressure potential is positive and partly offsets the negative solute potential.

Question 19Cells and Cell Biology

A plant cell with water potential −600 kPa is placed in a solution of water potential −300 kPa. Which statement describes the net movement of water?

  1. Water leaves the cell because the external solution has higher water potential
  2. No net movement occurs because both values are negative
  3. Water enters the cell because the cell has higher water potential
  4. Water enters the cell because the external solution has higher water potential Correct answer.

Explanation

Water moves from higher (less negative) to lower water potential, so it flows from −300 kPa outside to −600 kPa inside. The cell gains water and its turgor pressure rises.

Question 20Cells and Cell Biology

In an experiment, the rate of enzyme-controlled reaction increases with substrate concentration and then levels off. What explains the plateau?

  1. The temperature has fallen to zero
  2. The substrate has been completely used up
  3. The enzyme has been permanently destroyed
  4. All active sites are occupied, so the enzyme is saturated Correct answer.

Explanation

Once substrate concentration is high enough, every enzyme active site is occupied at any moment, so adding more substrate cannot increase the rate further. The plateau reflects enzyme saturation, not substrate exhaustion.

Question 21Biological Molecules and Enzymes

Which element is present in all proteins but absent from carbohydrates and lipids?

  1. Hydrogen
  2. Carbon
  3. Oxygen
  4. Nitrogen Correct answer.

Explanation

Proteins are polymers of amino acids, and every amino acid contains an amino group built around a nitrogen atom. Carbohydrates and most lipids are composed only of carbon, hydrogen and oxygen, so nitrogen is the distinguishing element in proteins.

Question 22Biological Molecules and Enzymes

A solution of reducing sugar is heated with Benedict's reagent. Which colour change shows a positive result?

  1. Blue to brick red Correct answer.
  2. Colourless to milky white
  3. Green to deep purple
  4. Yellow to colourless

Explanation

Benedict's reagent is blue because of copper(II) ions. Reducing sugars reduce these ions to copper(I) oxide, which forms a brick-red precipitate on heating, so a positive test moves from blue through green and yellow to brick red.

Question 23Biological Molecules and Enzymes

Which bond joins two amino acids together in a polypeptide chain?

  1. Phosphodiester bond
  2. Ester bond
  3. Glycosidic bond
  4. Peptide bond Correct answer.

Explanation

A condensation reaction between the carboxyl group of one amino acid and the amino group of the next releases water and forms a peptide bond. Repeated peptide bonds build the polypeptide backbone.

Question 24Biological Molecules and Enzymes

Which statement describes the effect of an enzyme on the activation energy of a reaction?

  1. It removes the need for activation energy entirely
  2. It increases the activation energy and is used up in the process
  3. It raises the activation energy so the reaction is controlled
  4. It lowers the activation energy without being consumed Correct answer.

Explanation

Enzymes are biological catalysts, so they provide an alternative reaction pathway with a lower activation energy. Because they are not used up, a small amount of enzyme can catalyse many reactions.

Question 25Biological Molecules and Enzymes

Which pair of molecules are both polysaccharides?

  1. Glucose and fructose
  2. Glycerol and fatty acids
  3. Sucrose and maltose
  4. Starch and glycogen Correct answer.

Explanation

Starch and glycogen are both large polymers of glucose monomers joined by glycosidic bonds. They act as storage carbohydrates in plants and animals respectively.

Question 26Biological Molecules and Enzymes

A student tests a food sample with biuret reagent and observes a violet colour. Which conclusion is best supported?

  1. The sample contains lipid droplets
  2. The sample contains starch only
  3. The sample contains peptide bonds Correct answer.
  4. The sample contains reducing sugar

Explanation

Biuret reagent changes from blue to violet in the presence of peptide bonds, which are characteristic of proteins and short peptides. The violet colour therefore indicates protein-type material rather than carbohydrate or lipid.

Question 27Biological Molecules and Enzymes

At low substrate concentration the rate of an enzyme-controlled reaction rises steeply, but at high substrate concentration it levels off. What explains the plateau?

  1. The substrate has been completely used up
  2. All active sites are occupied at any moment Correct answer.
  3. The enzyme has been permanently denatured
  4. The pH of the solution has fallen to zero

Explanation

Rate depends on how often substrate molecules collide with free active sites. Once every enzyme molecule is working at maximum capacity, adding more substrate cannot increase the rate further, so the graph plateaus.

Question 28Biological Molecules and Enzymes

Which change to a globular enzyme would most directly destroy its active site shape?

  1. Adding more substrate to the reaction mixture
  2. Increasing the substrate concentration slightly
  3. Breaking hydrogen and ionic bonds that hold the tertiary structure Correct answer.
  4. Adding a cofactor that binds to the active site

Explanation

The precise shape of an active site depends on the tertiary structure held together by hydrogen bonds, ionic bonds and other weak interactions. Disrupting these bonds causes denaturation and changes the active site so the substrate no longer fits.

Question 29Biological Molecules and Enzymes

Which description best explains why enzymes are described as specific?

  1. Each enzyme works only at a single fixed temperature
  2. Each enzyme's active site is complementary to one substrate shape Correct answer.
  3. Each enzyme can catalyse every reaction in a cell
  4. Each enzyme is used up after one reaction

Explanation

Specificity arises because the active site has a shape and chemical character complementary to a particular substrate. Only molecules that fit and interact correctly can form an enzyme-substrate complex, so most enzymes act on one substrate or a closely related group.

Question 30Biological Molecules and Enzymes

A triglyceride is hydrolysed completely. Which products are formed?

  1. One glucose and three fatty acids
  2. One glycerol and three fatty acids Correct answer.
  3. Three glycerols and one fatty acid
  4. One glycerol and three amino acids

Explanation

A triglyceride consists of a glycerol molecule joined by ester bonds to three fatty acid chains. Complete hydrolysis breaks all three ester bonds, releasing one glycerol and three fatty acids.

Question 31Biological Molecules and Enzymes

Which feature of the phospholipid molecule allows it to form a bilayer in water?

  1. A hydrophilic phosphate head and hydrophobic hydrocarbon tails Correct answer.
  2. A hydrophobic phosphate head and hydrophilic tails
  3. Two hydrophilic fatty acid tails and a hydrophobic head
  4. A hydrophilic glycerol core with no charged groups

Explanation

The phosphate head is polar and interacts with water, while the two fatty acid tails are non-polar and are repelled by water. In water the molecules arrange so heads face outward and tails face inward, producing a bilayer.

Question 32Biological Molecules and Enzymes

An enzyme has an optimum pH of 2. A sample is moved to pH 7 and then returned to pH 2. What is the most likely result?

  1. Activity rises because pH 7 is closer to neutral
  2. Activity stays low because the change to pH 7 denatured the enzyme Correct answer.
  3. Activity returns fully because pH changes are always reversible
  4. Activity is unchanged because pH has no effect on enzymes

Explanation

Extreme pH changes break the ionic and hydrogen bonds maintaining tertiary structure, and this denaturation is usually permanent. Returning the enzyme to its optimum pH cannot restore an active site whose shape has already been destroyed.

Question 33Biological Molecules and Enzymes

Which statement about the induced fit model of enzyme action is correct?

  1. The substrate changes shape permanently to fit a rigid site
  2. Enzymes lower activation energy by binding products only
  3. The active site is exactly rigid and never changes
  4. The active site adjusts slightly as the substrate binds Correct answer.

Explanation

In the induced fit model the active site is flexible and moulds around the substrate as the enzyme-substrate complex forms. This closer contact strains bonds in the substrate and helps lower the activation energy.

Question 34Biological Molecules and Enzymes

A competitive inhibitor is added to an enzyme-catalysed reaction. Which change in a graph of rate against substrate concentration is expected?

  1. The curve becomes a straight line through the origin
  2. The maximum rate falls and the curve plateaus at a lower value
  3. The maximum rate is unchanged but a higher substrate concentration is needed Correct answer.
  4. The initial rate rises above the uninhibited value

Explanation

A competitive inhibitor binds to the active site, so its effect can be overcome by raising the substrate concentration. Given enough substrate, the enzyme still reaches the same maximum rate, but more substrate is required to get there.

Question 35Biological Molecules and Enzymes

Which structural difference explains why starch is a suitable storage carbohydrate while cellulose is not?

  1. Starch has beta-glucose units joined by strong cross-links
  2. Cellulose contains nitrogen, which makes it resistant to enzymes
  3. Starch is branched and coiled, making it compact and easily hydrolysed Correct answer.
  4. Cellulose is branched and therefore more compact than starch

Explanation

Starch is built from alpha-glucose and its branched, coiled chains pack into compact granules that are readily hydrolysed to release glucose. Cellulose chains of beta-glucose form straight, cross-linked microfibrils that are strong and only slowly digested, so cellulose serves a structural role.

Question 36Biological Molecules and Enzymes

A enzyme is immobilised on beads and used repeatedly in a continuous reactor. Which advantage is most directly explained by immobilisation?

  1. The enzyme becomes permanently more heat-sensitive
  2. The enzyme is consumed gradually with each reaction cycle
  3. The enzyme can be recovered and reused, reducing cost Correct answer.
  4. The substrate no longer needs to contact the active site

Explanation

Immobilised enzymes are held in place on a solid support, so they can be separated from the product stream and used again. This reusability lowers enzyme costs and allows continuous operation rather than batch processing.

Question 37Nutrition and Digestion

Which enzyme begins the chemical digestion of starch in the human mouth?

  1. Lipase
  2. Pepsin
  3. Salivary amylase Correct answer.
  4. Trypsin

Explanation

Salivary amylase is released by the salivary glands and hydrolyses starch into shorter chains such as maltose while food is chewed. This is the first chemical step of carbohydrate digestion and it stops once the enzyme is inactivated by stomach acid.

Question 38Nutrition and Digestion

What is the main role of bile in digestion?

  1. Absorbing glucose into the blood
  2. Breaking proteins into amino acids
  3. Emulsifying fats into smaller droplets Correct answer.
  4. Neutralising vitamins in the colon

Explanation

Bile is produced by the liver and stored in the gall bladder before being released into the small intestine. It contains bile salts that emulsify large fat droplets into many smaller ones, increasing the surface area for lipase to act on.

Question 39Nutrition and Digestion

Which region of the alimentary canal is the main site of absorption of digested nutrients?

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

Explanation

The small intestine has a very large surface area created by villi and microvilli, plus a rich blood supply, so most digested nutrients are absorbed there. The stomach absorbs only limited substances such as some water and alcohol.

Question 40Nutrition and Digestion

Which food test uses Benedict's solution and gives a brick-red colour when positive?

  1. Test for lipid
  2. Test for reducing sugar Correct answer.
  3. Test for protein
  4. Test for starch

Explanation

Benedict's solution is blue and turns brick-red after heating with a reducing sugar such as glucose. The colour change comes from reduction of copper(II) ions to copper(I) oxide.

Question 41Nutrition and Digestion

Which type of teeth are adapted for tearing and gripping food in a typical mammal?

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

Explanation

Canines are pointed, cone-shaped teeth positioned at the corners of the mouth and are used for gripping and tearing food. Their shape reflects this function, especially in carnivores.

Question 42Nutrition and Digestion

A person's diet lacks vitamin C over several months. Which deficiency disease is most likely to develop?

  1. Rickets
  2. Scurvy Correct answer.
  3. Anaemia
  4. Beriberi

Explanation

Vitamin C is needed for the synthesis of collagen, so a prolonged deficiency causes scurvy, with bleeding gums and poor wound healing. Other vitamins cause different deficiency diseases, so matching the vitamin to its disease is essential.

Question 43Nutrition and Digestion

Which structure prevents food from entering the trachea during swallowing?

  1. Uvula
  2. Villus
  3. Sphincter
  4. Epiglottis Correct answer.

Explanation

During swallowing the epiglottis folds down over the opening of the trachea, so the bolus passes into the oesophagus instead of the airway. This protects the lungs from choking.

Question 44Nutrition and Digestion

Why does the stomach secrete hydrochloric acid?

  1. To kill ingested bacteria and provide an acidic pH for pepsin Correct answer.
  2. To stimulate peristalsis in the colon
  3. To absorb amino acids directly into the blood
  4. To emulsify fats before they reach the duodenum

Explanation

Stomach acid lowers the pH, which kills many swallowed microbes and provides the low pH needed for pepsin to work effectively. Pepsinogen is also converted to active pepsin in acidic conditions.

Question 45Nutrition and Digestion

Villi in the small intestine increase the rate of absorption mainly because they

  1. store absorbed glucose as glycogen
  2. increase the surface area available for diffusion Correct answer.
  3. secrete digestive enzymes into the lumen
  4. prevent food from moving too quickly

Explanation

Each villus has a large surface area and a thin wall with a dense capillary network, so the rate of diffusion and active transport of nutrients rises. Surface area is a key factor in the rate of absorption.

Question 46Nutrition and Digestion

Which molecule is the final product of the complete digestion of a protein?

  1. Amino acids Correct answer.
  2. Glycerol
  3. Monosaccharides
  4. Fatty acids

Explanation

Proteases hydrolyse peptide bonds so that proteins are eventually broken down into amino acids, which can be absorbed. Fatty acids, glycerol and monosaccharides come from the digestion of lipids and carbohydrates.

Question 47Nutrition and Digestion

A student chews a piece of bread for several minutes and notices it tastes sweet. Which explanation is most accurate?

  1. Salivary amylase has converted some starch into sugars Correct answer.
  2. Gastric acid has hydrolysed the bread into glucose
  3. Bile has started to break down the bread
  4. Pepsin has digested the bread proteins into sugars

Explanation

Salivary amylase hydrolyses starch in bread into shorter sugars such as maltose, which taste sweet. The effect appears only after prolonged chewing because the enzyme needs time to act.

Question 48Nutrition and Digestion

Which statement best describes the role of the liver in digestion?

  1. It produces bile, which is stored in the gall bladder Correct answer.
  2. It absorbs most of the water from undigested food
  3. It secretes lipase directly into the duodenum
  4. It stores faeces before they are egested

Explanation

The liver produces bile, which passes to the gall bladder for storage and concentration before release into the small intestine. Bile salts then emulsify fats to aid lipase action.

Question 49Nutrition and Digestion

Which combination of adaptations would most increase the efficiency of nutrient absorption in the ileum?

  1. Thin walls, dense capillaries, and folded epithelium Correct answer.
  2. Thick walls, dense capillaries, and folded epithelium
  3. Thick walls, few capillaries, and smooth epithelium
  4. Thin walls, few capillaries, and smooth epithelium

Explanation

Absorption is fastest when the diffusion distance is short (thin walls), the concentration gradient is maintained by a rich blood supply, and the surface area is large (folded epithelium). All three features act together.

Question 50Nutrition and Digestion

An enzyme that digests lipids is added to a tube containing a large fat droplet and water at the optimum temperature. Which change would most speed up the reaction?

  1. Increasing the size of the fat droplet
  2. Cooling the mixture to near freezing
  3. Adding bile salts to the mixture Correct answer.
  4. Adding a strong acid to the mixture

Explanation

Bile salts emulsify the fat into many small droplets, greatly increasing the surface area exposed to lipase. A larger surface area allows more enzyme molecules to act at once, so the reaction is faster.