I85PREP
⌘ K
LC Biology study materials
LC Biology study resources

LC Biology practice questions

One question at a time. Build your LC Biology understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1The scientific method and biological terminology; laboratory practical work and reporting

In a controlled experiment investigating the effect of light intensity on the rate of photosynthesis, which variable is the independent variable?

  1. The mass of the pondweed used
  2. The light intensity applied Correct answer.
  3. The temperature of the water bath
  4. The rate of oxygen production

Explanation

The independent variable is the factor deliberately changed by the investigator, which here is the light intensity set at each trial. The rate of oxygen production is the dependent variable because it is measured as the outcome. Temperature and plant mass are controlled variables held constant to keep the test fair.

Question 2The scientific method and biological terminology; laboratory practical work and reporting

A student writes a hypothesis before an experiment. Which statement best describes the role of a hypothesis in scientific investigation?

  1. It is a fixed law that cannot be altered by new evidence
  2. It is a testable prediction that can be supported or refuted by results Correct answer.
  3. It is a proven fact established before any data are collected
  4. It is a summary of the final conclusions drawn from the data

Explanation

A hypothesis is a proposed, testable explanation or prediction made before data collection. Experimental results either support or refute it, and it is never treated as proven in advance. Conclusions are drawn only after the data have been analysed.

Question 3The scientific method and biological terminology; laboratory practical work and reporting

Which piece of laboratory equipment would be most appropriate for accurately measuring 25 cm³ of water in a school biology practical?

  1. A conical flask of 100 cm³ capacity
  2. A graduated cylinder of 50 cm³ capacity
  3. A graduated pipette of 25 cm³ capacity Correct answer.
  4. A beaker of 250 cm³ capacity

Explanation

A graduated pipette of the required volume delivers a fixed, accurate volume with a single filling, giving the highest precision. Beakers and conical flasks carry only approximate graduations intended for rough measuring. A large graduated cylinder has a coarser scale relative to 25 cm³ than a pipette matched to that volume.

Question 4The scientific method and biological terminology; laboratory practical work and reporting

In a practical, a student counts the number of bubbles released by pondweed per minute as a measure of photosynthetic rate. What term describes this measurement?

  1. The constant
  2. The independent variable
  3. The control
  4. The dependent variable Correct answer.

Explanation

The dependent variable is the factor measured as the outcome of the experiment, here the bubble count per minute. It is expected to change in response to the independent variable. Controls and constants are factors held fixed rather than measured outcomes.

Question 5The scientific method and biological terminology; laboratory practical work and reporting

Which of the following is the correct standard unit for expressing the rate of an enzyme-controlled reaction in a school laboratory report?

  1. Degrees Celsius
  2. Grams per litre
  3. Cubic centimetres
  4. Units per minute Correct answer.

Explanation

A rate expresses change per unit time, so units such as units per minute or cm³ per minute are appropriate. Grams per litre and cubic centimetres describe quantity or concentration, not rate. Degrees Celsius measures temperature, which is a condition rather than a rate.

Question 6The scientific method and biological terminology; laboratory practical work and reporting

A student repeats a measurement five times and obtains values that are very close to one another but all far from the true value. Which description applies?

  1. The results are accurate but not precise
  2. The results are both accurate and precise
  3. The results are precise but not accurate Correct answer.
  4. The results are neither precise nor accurate

Explanation

Precision refers to how closely repeated measurements agree with each other, while accuracy refers to closeness to the true value. Values clustered tightly together but displaced from the true value are precise but inaccurate. This pattern often indicates a systematic error such as a mis-calibrated instrument.

Question 7The scientific method and biological terminology; laboratory practical work and reporting

During a practical on osmosis, a student uses a balance reading 0.00 g with no mass on the pan. What is the purpose of this step?

  1. To sterilise the weighing pan
  2. To calibrate the balance to zero before weighing samples Correct answer.
  3. To measure the density of the samples
  4. To determine the maximum capacity of the balance

Explanation

Setting the balance to read zero with an empty pan, known as taring, removes any offset so that subsequent readings reflect only the sample mass. It does not measure density, capacity, or sterilise equipment. Correct zeroing reduces systematic error in the recorded masses.

Question 8The scientific method and biological terminology; laboratory practical work and reporting

A student wishes to examine the effect of pH on amylase activity. Which set of conditions should be kept constant to make the test valid?

  1. pH and substrate concentration
  2. Enzyme concentration and pH
  3. Temperature and substrate concentration Correct answer.
  4. Temperature and pH

Explanation

Only the independent variable, pH, should be varied, so all other influential factors must be held constant. Temperature and substrate concentration strongly affect enzyme rate and must therefore be controlled. Including pH among the constants would remove the very variable under test.

Question 9The scientific method and biological terminology; laboratory practical work and reporting

In a report, a student states that a result is 'significant'. Which condition best supports the use of this term?

  1. The result agrees with the student's original hypothesis
  2. The result was observed in a single trial
  3. The result differs from the control by a large enough margin to be unlikely due to chance Correct answer.
  4. The result was obtained using the most expensive equipment available

Explanation

In science, a significant result is one unlikely to have arisen by chance alone, usually assessed statistically. A single trial cannot establish significance because random variation is not accounted for. Agreement with a hypothesis or the cost of equipment does not determine statistical significance.

Question 10The scientific method and biological terminology; laboratory practical work and reporting

Which of the following is the most appropriate way to record raw quantitative data during a laboratory practical?

  1. As a single average value with no individual readings
  2. In a clearly labelled table with units in the column headings Correct answer.
  3. Only after the experiment is complete, from memory
  4. As a written paragraph describing the observations

Explanation

Raw data should be recorded immediately in a structured table with clearly labelled headings and units, so that individual readings are preserved. Recording from memory later introduces error and loses detail. A single average discards the individual values needed to assess variability.

Question 11The scientific method and biological terminology; laboratory practical work and reporting

A student measures the length of a root tip as 12 mm using a ruler marked in millimetres. Which value correctly reflects the precision of the instrument?

  1. 12 mm ± 0.5 mm Correct answer.
  2. 12 mm ± 5 mm
  3. 12 mm ± 12 mm
  4. 12 mm exactly, with no uncertainty

Explanation

When reading an analogue scale, the uncertainty is typically half the smallest division. With a millimetre scale, the smallest division is 1 mm, so the uncertainty is about ± 0.5 mm. Claiming exactness or an uncertainty larger than the reading itself is not justified.

Question 12The scientific method and biological terminology; laboratory practical work and reporting

Which statement correctly distinguishes a control group from a controlled variable in an experiment?

  1. A control group is a comparison treatment without the test factor, while a controlled variable is a factor kept constant Correct answer.
  2. A control group is a factor kept constant, while a controlled variable is the treatment being tested
  3. Both terms refer to the factor deliberately changed by the investigator
  4. Both terms refer to the outcome measured at the end of the experiment

Explanation

A control group provides a baseline for comparison and lacks the experimental treatment, allowing the effect of the test factor to be isolated. A controlled variable, by contrast, is any factor held constant across all groups. The two concepts serve different roles and should not be confused.

Question 13The scientific method and biological terminology; laboratory practical work and reporting

A student plots a graph of enzyme activity against temperature. Which convention should be followed when labelling the axes?

  1. Temperature on the y-axis with units, activity on the x-axis without units
  2. Both axes labelled without units to keep the graph clean
  3. Activity on the y-axis with units, temperature on the x-axis with units Correct answer.
  4. Only the y-axis labelled, since the x-axis is always the independent variable

Explanation

The independent variable, temperature, is conventionally placed on the x-axis and the dependent variable, activity, on the y-axis. Both axes must carry labels and appropriate units so the graph can be interpreted. Omitting units removes essential information about the quantities shown.

Question 14The scientific method and biological terminology; laboratory practical work and reporting

Why is it important to include replicates in a biological experiment?

  1. To eliminate the need for a control group
  2. To reduce the influence of random variation on the conclusions Correct answer.
  3. To make the experiment take longer and appear more thorough
  4. To guarantee that the hypothesis will be supported

Explanation

Replicates allow the investigator to assess natural variability and reduce the impact of random error on conclusions. They do not guarantee a particular outcome, since results may still refute the hypothesis. A control group remains necessary regardless of the number of replicates.

Question 15The scientific method and biological terminology; laboratory practical work and reporting

A student uses a light microscope and wishes to view a specimen at higher magnification. Which adjustment is most appropriate?

  1. Replace the eyepiece with a lower-power one
  2. Move the stage away from the lens and refocus with the coarse adjustment only
  3. Rotate to a higher-power objective lens and refocus using the fine adjustment Correct answer.
  4. Increase the light intensity without changing the objective lens

Explanation

Increasing magnification requires switching to a higher-power objective and then refocusing carefully with the fine adjustment, since the working distance is very small. Using the coarse adjustment at high power risks driving the lens into the slide. Changing light intensity or lowering the eyepiece power does not increase magnification.

Question 16The scientific method and biological terminology; laboratory practical work and reporting

Which of the following best describes a 'fair test' in the context of a biological investigation?

  1. An investigation in which all variables are allowed to change freely
  2. An investigation in which only the independent variable is allowed to affect the dependent variable Correct answer.
  3. An investigation carried out by more than one student
  4. An investigation that produces the expected result

Explanation

A fair test isolates the effect of the independent variable by keeping all other influential factors constant. Allowing variables to change freely would confound the results and make conclusions unreliable. The number of investigators or agreement with expectations does not define fairness.

Question 17The scientific method and biological terminology; laboratory practical work and reporting

A student records the following masses of a potato cylinder before and after immersion in a solution: 2.50 g and 2.18 g. Which calculation correctly gives the percentage change in mass?

  1. (2.50 + 2.18) ÷ 2 × 100 = 234% decrease
  2. (2.50 − 2.18) ÷ 2.18 × 100 = 14.7% decrease
  3. (2.18 − 2.50) ÷ 2.50 × 100 = −12.8% decrease
  4. (2.50 − 2.18) ÷ 2.50 × 100 = 12.8% decrease Correct answer.

Explanation

Percentage change is calculated by dividing the change in mass by the original mass and multiplying by 100. Here the change is 0.32 g and the original mass is 2.50 g, giving a 12.8% decrease. Dividing by the final mass or averaging the masses does not give percentage change.

Question 18The scientific method and biological terminology; laboratory practical work and reporting

Which of the following is the most appropriate reason for discarding an anomalous result from a data set?

  1. It was recorded in a different colour of ink
  2. It was the first reading taken in the experiment
  3. It is clearly due to an identifiable procedural error such as a misread instrument Correct answer.
  4. It differs from the other readings and the student prefers a cleaner graph

Explanation

An anomalous result may be excluded only when there is a clear, documented reason such as a known procedural error. Discarding data merely because they are inconvenient or differ from the rest undermines the integrity of the investigation. The order of recording or the ink colour is irrelevant to validity.

Question 19The scientific method and biological terminology; laboratory practical work and reporting

In a laboratory report, which section should contain a detailed description of the procedure so that another student could repeat the investigation?

  1. The method section Correct answer.
  2. The conclusion section
  3. The introduction section
  4. The results section

Explanation

The method section describes the procedure, materials, and conditions in sufficient detail for replication. The results section presents the data obtained, and the conclusion interprets those data against the hypothesis. The introduction provides background and the aim rather than the procedural detail.

Question 20The scientific method and biological terminology; laboratory practical work and reporting

A student claims that a treatment caused an observed effect, but the experiment lacked a control group. Which criticism is most valid?

  1. Without a control, the effect cannot be attributed specifically to the treatment Correct answer.
  2. Without a control, no measurements can be recorded
  3. Without a control, the independent variable cannot be identified
  4. Without a control, the experiment cannot be repeated

Explanation

A control group provides the baseline needed to separate the effect of the treatment from other influences such as time or environmental conditions. Without it, any change observed could have arisen from factors other than the treatment. Controls are not required for repeatability, measurement, or identifying the independent variable.

Question 21The scientific method and biological terminology; laboratory practical work and reporting

A student measures the rate of respiration in yeast at five temperatures and reports a mean for each. Which additional statistic would best indicate the reliability of each mean?

  1. The single highest reading at that temperature
  2. The temperature at which the highest mean occurred
  3. The range of the replicate readings at that temperature Correct answer.
  4. The total number of temperatures tested

Explanation

The range of replicates shows how widely the readings vary, giving an indication of reliability and random error. A single highest value ignores the spread of the other readings and is not a measure of reliability. The position of the peak mean and the number of temperatures tested describe the experiment's design rather than the precision of each mean.

Question 22The scientific method and biological terminology; laboratory practical work and reporting

When preparing a slide of onion epidermis for microscopy, why is a drop of iodine solution commonly added?

  1. To make the cells move so that organelles can be observed
  2. To increase the magnification of the specimen
  3. To stain the cells so that structures such as the nucleus become visible Correct answer.
  4. To dissolve the cell wall and release the contents

Explanation

Iodine acts as a stain that increases contrast, making features such as the nucleus and cell wall easier to distinguish. It does not alter magnification, which depends on the lenses used. It also does not induce movement or dissolve the cellulose cell wall.

Question 23The scientific method and biological terminology; laboratory practical work and reporting

A student concludes that increasing light intensity increases the rate of photosynthesis based on data that plateau above a certain intensity. Which refinement of the conclusion is most scientifically sound?

  1. The rate increases indefinitely as light intensity rises
  2. The rate increases with light intensity up to a point, after which another factor becomes limiting Correct answer.
  3. Light intensity has no effect on the rate of photosynthesis
  4. The rate decreases steadily as light intensity rises

Explanation

A plateau in the data indicates that beyond a certain light intensity another factor, such as carbon dioxide concentration or temperature, limits the rate. The conclusion should therefore describe an initial increase followed by a limit rather than a continuing rise. Ignoring the plateau misrepresents the observed data.

Question 24The scientific method and biological terminology; laboratory practical work and reporting

A student reports a mean value of 4.6 units from replicate readings of 4.2, 4.4, 4.8, and 5.0. Which statement about this mean is most accurate?

  1. The mean should be calculated using only the two middle readings
  2. The mean conceals the spread of the readings, which should be reported alongside it Correct answer.
  3. The mean is invalid because the readings differ from one another
  4. The mean proves that all readings were identical

Explanation

A mean summarises central tendency but hides the variability between individual readings, so the range or another measure of spread should accompany it. Variation among replicates is expected and does not invalidate the mean. Means are calculated from all readings, not selected ones.

Question 25Food, nutrition, digestion and enzymes

Which food biomolecule is the primary immediate source of energy for most body cells and is broken down to glucose during digestion?

  1. Vitamin
  2. Lipid
  3. Protein
  4. Carbohydrate Correct answer.

Explanation

Carbohydrates are digested to monosaccharides such as glucose, which cells oxidise in respiration to release energy quickly. Proteins and lipids can also yield energy but are not the body's preferred immediate fuel. Vitamins are micronutrients and are not broken down as an energy source.

Question 26Food, nutrition, digestion and enzymes

A student tests a food sample with Benedict's reagent and obtains a brick-red precipitate after heating. Which nutrient is indicated?

  1. Starch
  2. Protein
  3. Fat
  4. Reducing sugar Correct answer.

Explanation

Benedict's reagent changes from blue to a brick-red precipitate when heated with a reducing sugar such as glucose. The colour change results from reduction of blue copper(II) ions to red copper(I) oxide. Starch, protein and fat give negative results with this reagent.

Question 27Food, nutrition, digestion and enzymes

Which structure in the human digestive system is the main site of absorption of digested nutrients into the blood?

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

Explanation

The small intestine has a very large surface area created by villi and microvilli, and its walls are richly supplied with blood capillaries. These features allow efficient absorption of glucose, amino acids and fatty acids. The stomach mainly stores and begins protein digestion, and the large intestine mainly absorbs water.

Question 28Food, nutrition, digestion and enzymes

Which enzyme catalyses the breakdown of starch into maltose?

  1. Catalase
  2. Protease
  3. Amylase Correct answer.
  4. Lipase

Explanation

Amylase is a carbohydrase that hydrolyses starch into maltose, a disaccharide. Salivary amylase begins this in the mouth and pancreatic amylase continues it in the small intestine. Lipase acts on fats, protease on proteins and catalase on hydrogen peroxide.

Question 29Food, nutrition, digestion and enzymes

Which substance is produced when lipase digests a lipid?

  1. Fatty acids and glycerol Correct answer.
  2. Peptides and starch
  3. Maltose and water
  4. Amino acids and glucose

Explanation

Lipase hydrolyses the ester bonds in triglycerides, releasing fatty acids and glycerol. These products are then absorbed by the villi. Amino acids come from protein digestion and maltose from starch digestion.

Question 30Food, nutrition, digestion and enzymes

Which vitamin is needed for the absorption of calcium in the intestine and is produced in the skin on exposure to sunlight?

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

Explanation

Vitamin D promotes calcium absorption in the small intestine and is synthesised in the skin when ultraviolet light converts a cholesterol derivative. A deficiency can lead to rickets in children because bones fail to mineralise properly. Vitamin A is linked to vision, vitamin C to collagen formation and vitamin K to clotting.

Question 31Food, nutrition, digestion and enzymes

A student wants to demonstrate that a food sample contains protein. Which procedure and positive result are correct?

  1. Add Benedict's reagent and heat; a red precipitate shows protein
  2. Add ethanol and water; a white emulsion shows protein
  3. Add iodine solution; a blue-black colour shows protein
  4. Add biuret solution; a purple colour shows protein Correct answer.

Explanation

The biuret test uses sodium hydroxide and copper sulfate solution, which turns from blue to purple in the presence of peptide bonds. This colour change is the accepted positive result for protein. The other procedures test for starch, reducing sugar and fat respectively.

Question 32Food, nutrition, digestion and enzymes

Which statement best explains why the inner surface of the small intestine is folded into villi?

  1. To secrete hydrochloric acid for protein digestion
  2. To store bile produced by the liver
  3. To increase the surface area available for absorption Correct answer.
  4. To slow the movement of food so digestion takes longer

Explanation

Villi are finger-like projections that greatly increase the surface area of the small intestine, allowing faster and more complete absorption of digested nutrients. Each villus contains capillaries and a lacteal to transport absorbed products away. Slowing food movement, acid secretion and bile storage are not functions of villi.

Question 33Food, nutrition, digestion and enzymes

Which condition would most directly reduce the activity of salivary amylase in the mouth?

  1. An increase in substrate concentration
  2. A fall in pH from 7 to 2
  3. A rise in temperature from 37 °C to 60 °C Correct answer.
  4. An increase in enzyme concentration

Explanation

Enzymes are proteins whose active sites depend on their three-dimensional shape. Heating well above the optimum temperature denatures amylase, altering the active site so the substrate can no longer bind. A pH change can also reduce activity, but the fall described here concerns stomach conditions rather than the mouth.

Question 34Food, nutrition, digestion and enzymes

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

  1. It hydrolyses fats into fatty acids and glycerol
  2. It emulsifies fats into small droplets, increasing the surface area for lipase Correct answer.
  3. It neutralises stomach acid to activate pepsin
  4. It breaks down proteins into amino acids

Explanation

Bile salts emulsify large fat globules into many small droplets, greatly increasing the surface area on which lipase can act. Bile is not itself an enzyme, so it does not chemically digest fats. It also helps neutralise acidic chyme from the stomach.

Question 35Food, nutrition, digestion and enzymes

A person's diet lacks iron. Which symptom is most likely to develop?

  1. Night blindness caused by a lack of rhodopsin
  2. Scurvy caused by defective collagen
  3. Anaemia caused by reduced haemoglobin production Correct answer.
  4. Rickets caused by poor calcium deposition

Explanation

Iron is a component of haemoglobin, the red pigment that carries oxygen in red blood cells. A deficiency reduces haemoglobin production, leading to anaemia with tiredness and breathlessness. Rickets, scurvy and night blindness are linked to vitamins D, C and A respectively.

Question 36Food, nutrition, digestion and enzymes

Which sequence correctly describes the passage of food through the human alimentary canal?

  1. Mouth → oesophagus → small intestine → stomach → large intestine
  2. Mouth → stomach → small intestine → oesophagus → large intestine
  3. Mouth → oesophagus → stomach → small intestine → large intestine Correct answer.
  4. Mouth → stomach → oesophagus → small intestine → large intestine

Explanation

Food passes from the mouth into the oesophagus, which carries it by peristalsis to the stomach. Digestion continues in the small intestine, and water is absorbed in the large intestine before egestion. The oesophagus always precedes the stomach.

Question 37Food, nutrition, digestion and enzymes

Which statement correctly describes the action of a digestive enzyme?

  1. It is permanently changed into the product
  2. It increases the activation energy of the reaction
  3. It lowers the activation energy needed for the reaction Correct answer.
  4. It is used up in the reaction it catalyses

Explanation

Digestive enzymes are biological catalysts that speed up hydrolysis by lowering the activation energy required. They are not consumed or permanently altered, so a small amount can catalyse many reactions. The substrate binds to the active site and is converted to products.

Question 38Food, nutrition, digestion and enzymes

A test tube contains starch solution and amylase at 37 °C. After 20 minutes, which result would confirm that digestion has occurred?

  1. Biuret solution turns purple
  2. Ethanol produces a cloudy emulsion
  3. Benedict's reagent gives a brick-red precipitate after heating Correct answer.
  4. Iodine solution turns blue-black

Explanation

Amylase hydrolyses starch to maltose, a reducing sugar. Testing with Benedict's reagent after heating would therefore give a brick-red precipitate, confirming that a reducing sugar has been produced. A blue-black iodine result would indicate that starch remained undigested.

Question 39Food, nutrition, digestion and enzymes

Which feature of a villus is most directly linked to the rapid transport of absorbed glucose away from the small intestine?

  1. A single layer of epithelial cells
  2. The presence of a lacteal
  3. The presence of mucus-secreting cells
  4. A dense network of blood capillaries Correct answer.

Explanation

Glucose and amino acids are absorbed into the blood capillaries inside each villus and carried away by the hepatic portal vein. The capillary network maintains a steep concentration gradient for continued absorption. The lacteal transports fatty acids and glycerol instead.

Question 40Food, nutrition, digestion and enzymes

An enzyme is extracted from the small intestine and tested at different pH values. Activity is highest at pH 8 and falls sharply at pH 2. Which conclusion is best supported?

  1. The enzyme is denatured by acid and has an alkaline optimum Correct answer.
  2. The enzyme is a carbohydrase that works only in the mouth
  3. The enzyme is unaffected by pH changes
  4. The enzyme requires acid conditions to function

Explanation

The enzyme shows maximum activity around pH 8 and loses activity in strongly acidic conditions because the acid disrupts the bonds holding the active site shape, causing denaturation. This pattern is typical of pancreatic enzymes such as trypsin in the small intestine. It does not indicate a requirement for acid.

Question 41Food, nutrition, digestion and enzymes

Which combination of food tests would distinguish between a sample of glucose solution and a sample of starch solution?

  1. Iodine solution and biuret solution
  2. Biuret solution and ethanol
  3. Benedict's reagent and iodine solution Correct answer.
  4. Benedict's reagent and ethanol

Explanation

Benedict's reagent gives a brick-red precipitate with glucose but stays blue with starch, while iodine turns blue-black with starch but stays brown with glucose. Using both tests therefore distinguishes the two samples. The other combinations include tests for protein or fat that would be negative for both samples.

Question 42Food, nutrition, digestion and enzymes

A person has had part of the ileum removed. Which nutritional consequence is most likely?

  1. Reduced absorption of most digested nutrients, leading to weight loss Correct answer.
  2. Reduced absorption of water only, leading to constipation
  3. Loss of bile production by the liver
  4. Loss of protein digestion in the stomach

Explanation

The ileum is the main region of the small intestine for absorbing digested nutrients, with its large surface area of villi. Removing part of it reduces the absorptive surface, so less glucose, amino acid and fat is absorbed and weight loss may follow. Water absorption in the colon and stomach or liver functions are unaffected.

Question 43Food, nutrition, digestion and enzymes

The graph of enzyme activity against substrate concentration rises steeply and then levels off. Which explanation best accounts for the plateau?

  1. All active sites are occupied, so the enzyme is working at maximum rate Correct answer.
  2. The substrate has been completely used up
  3. The pH of the solution has fallen below the optimum
  4. The enzyme has become denatured by excess substrate

Explanation

At low substrate concentration, increasing substrate increases the rate because more collisions occur between substrate and active sites. The plateau occurs when every active site is occupied at any moment, so adding more substrate cannot increase the rate further. This is enzyme saturation, not denaturation or substrate exhaustion.

Question 44Food, nutrition, digestion and enzymes

Which structural feature of the alimentary canal is correctly matched with its function?

  1. Stomach - absorption of most amino acids
  2. Teeth - increase the surface area of food for enzyme action Correct answer.
  3. Liver - secretion of lipase into the duodenum
  4. Colon - secretion of hydrochloric acid

Explanation

Chewing with teeth physically breaks food into smaller pieces, increasing the surface area exposed to enzymes such as amylase. This is mechanical digestion. Amino acids are mainly absorbed in the small intestine, lipase is secreted by the pancreas, and hydrochloric acid is secreted by the stomach.

Question 45Cellular structure, transport across membranes and cell division

Which structure controls the entry and exit of substances in a cell and is described as selectively permeable?

  1. The cell wall
  2. The nucleus
  3. The cell membrane Correct answer.
  4. The ribosome

Explanation

The cell membrane is a phospholipid bilayer with embedded proteins that allows some substances to pass while restricting others, which is what selectively permeable means. The cell wall is fully permeable and provides support rather than regulation.

Question 46Cellular structure, transport across membranes and cell division

A student views a cell and observes a rigid outer layer outside the cell membrane. Which cell type is being observed?

  1. A nerve cell
  2. A plant cell Correct answer.
  3. An animal cell
  4. A red blood cell

Explanation

A rigid layer outside the membrane is a cellulose cell wall, which is characteristic of plant cells. Animal cells such as red blood cells and nerve cells lack a cell wall and are bounded only by a flexible membrane.

Question 47Cellular structure, transport across membranes and cell division

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

  1. The chloroplast
  2. The mitochondrion Correct answer.
  3. The Golgi apparatus
  4. The lysosome

Explanation

The mitochondrion carries out the later stages of aerobic respiration, including the Krebs cycle and oxidative phosphorylation, generating most of the cell's ATP. Chloroplasts perform photosynthesis, while the Golgi and lysosomes handle modification and digestion respectively.

Question 48Cellular structure, transport across membranes and cell division

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

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

Explanation

In metaphase the chromosomes become arranged along the metaphase plate at the cell equator, attached to spindle fibres. Prophase involves chromosome condensation, anaphase involves separation of chromatids, and telophase involves nuclear reformation.

Question 49Cellular structure, transport across membranes and cell division

What is the main difference between diffusion and osmosis?

  1. Osmosis requires ATP while diffusion does not
  2. Diffusion only occurs in living cells
  3. Osmosis moves water across a membrane while diffusion moves any particles Correct answer.
  4. Osmosis moves solutes while diffusion moves water

Explanation

Osmosis is specifically the movement of water across a selectively permeable membrane from a region of higher water potential to lower water potential. Diffusion is the general movement of any particles from higher to lower concentration.

Question 50Cellular structure, transport across membranes and cell division

Which part of the chromosome holds the two sister chromatids together before anaphase?

  1. The telomere
  2. The centromere Correct answer.
  3. The spindle
  4. The nucleolus

Explanation

The centromere is the region where sister chromatids remain joined and where spindle fibres attach. Telomeres are protective end sequences, the nucleolus makes ribosomes, and the spindle is a microtubule structure.