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Biology Comprehensive Practice Test 3

An online Biology practice test covering What Is the Human Cell? A Simple Guide, and Biological Molecules, Enzymes & Food Tests — progressing from foundational knowledge to application, analysis and higher-order reasoning.

EDUSAMBAM Editorial Team·45 questions · 100 marks·Basic → Advanced·Last updated: November 2026
45
Questions
100
Marks
5
Sections
100%
Auto-Graded
SectionQuestionsMarks eachTotal marks
A — Multiple Choice15230
B — True / False10220
C — Fill in the Blank10220
D — Column Matching5 pairs210
E — Short Answer5420
Total45—100

Fill-in-the-blank answers are checked against accepted spellings of the key term. Short answers are marked against a marking guide: write a full answer (at least 8 words) and you earn marks for each key idea you include. After you submit, every question shows the correct answer with a short explanation.

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Section A — Multiple Choice

30 marks

15 questions · 2 marks each. Choose the best answer.

1.Which organelle contains most of a eukaryotic cell's DNA?Basic2 pts
Why: The correct answer is D. The nucleus holds most of the cell's DNA. Ribosomes make proteins, lysosomes break down materials, and the Golgi apparatus modifies and packages proteins.
2.Ribosomes are directly involved in:Basic2 pts
Why: The correct answer is A. Ribosomes read messenger RNA and join amino acids together to make proteins.
3.The plasma membrane is mainly a:Basic2 pts
Why: The correct answer is C. The plasma membrane is a phospholipid bilayer with embedded proteins. It is selective about what crosses it. Cellulose walls are found in plant cells, not animal cells.
4.Which molecule is a polymer made from amino acids?Basic2 pts
Why: The correct answer is B. Proteins are chains of amino acids. Starch is made of glucose units, DNA of nucleotides, and a triglyceride is not a polymer.
5.Enzymes accelerate reactions primarily by:Basic2 pts
Why: The correct answer is A. Enzymes provide an alternative pathway with a lower activation energy. They are not used up, and they do not change the overall energy change.
6.A very high temperature can reduce enzyme activity because:Intermediate2 pts
Why: The correct answer is D. Heat can break the bonds that hold the enzyme's shape. The active site then no longer fits the substrate (denaturation).
7.The iodine test is commonly used to detect:Intermediate2 pts
Why: The correct answer is C. Iodine solution turns blue-black when starch is present. Biuret detects protein, the emulsion test detects lipids, and DCPIP is used for vitamin C.
8.A positive Benedict's test after heating can indicate:Intermediate2 pts
Why: The correct answer is B. Benedict's reagent changes from blue to green, yellow, orange or brick-red when heated with reducing sugars such as glucose.
9.The Biuret test is associated with:Intermediate2 pts
Why: The correct answer is D. Biuret reagent turns from blue to purple or violet when peptide bonds are present, so it indicates protein.
10.The emulsion test is commonly used for:Intermediate2 pts
Why: The correct answer is A. In the emulsion test a cloudy white emulsion forms when lipids dissolved in ethanol are mixed with water.
11.If an enzyme's active site changes shape, the most direct consequence is likely:Advanced2 pts
Why: The correct answer is C. Enzyme activity depends on the shape of the active site. If the shape changes, the substrate may not fit and the reaction slows.
12.Which statement best describes hydrolysis?Advanced2 pts
Why: The correct answer is B. Hydrolysis uses a water molecule to break a bond, for example when digestion splits starch into sugars.
13.Why are controls important in food tests?Advanced2 pts
Why: The correct answer is A. A control gives something to compare with, so a colour change can be linked to the sample and not to contaminated reagents.
14.A positive qualitative food test generally tells you that:Advanced2 pts
Why: The correct answer is D. A qualitative test shows whether something is detected. It does not measure the amount or say anything about health.
15.Which statement best connects structure and function?Advanced2 pts
Why: The correct answer is C. In biology, shape and chemical features decide how molecules interact. Changing the structure, as in a denatured enzyme, can change the function.

Section B — True / False

20 marks

10 questions · 2 marks each.

16.All proteins are enzymes.Basic2 pts
Why: The answer is False. Many proteins are not enzymes. Examples are haemoglobin, collagen and antibodies.
17.Enzymes are generally unchanged at the end of the reactions they catalyse.Basic2 pts
Why: The answer is True. Enzymes are not used up. They can catalyse the same reaction many times.
18.A negative iodine test proves that a food contains no carbohydrates of any type.Basic2 pts
Why: The answer is False. Iodine detects starch only. Sugars and other carbohydrates are not detected by it.
19.The cell membrane helps maintain different conditions inside and outside the cell.Basic2 pts
Why: The answer is True. Selective transport across the membrane keeps the inside of the cell different from its surroundings.
20.DNA and RNA are nucleic acids.Basic2 pts
Why: The answer is True. Both are polymers of nucleotides.
21.Lipids can contribute to membranes and energy storage.Intermediate2 pts
Why: The answer is True. Phospholipids form membranes, and fats store energy.
22.A qualitative test always gives an exact concentration.Intermediate2 pts
Why: The answer is False. Qualitative tests show presence or absence. Measuring concentration needs a quantitative method.
23.Substrate concentration can affect enzyme reaction rate under suitable conditions.Advanced2 pts
Why: The answer is True. More substrate usually raises the rate until the enzymes are saturated.
24.Extreme pH can alter the structure and activity of many enzymes.Advanced2 pts
Why: The answer is True. Extreme pH can change the charges that hold an enzyme's shape and can denature it.
25.Controls are unnecessary when comparing two food samples.Advanced2 pts
Why: The answer is False. Controls are needed to show that the reagents work and that the result is caused by the sample.

Section C — Fill in the Blank

20 marks

10 questions · 2 marks each. Type the missing word or term.

26.The monomers that form proteins are ______ acids.Intermediate2 pts
Why: Proteins are chains of amino acids.
27.The enzyme region where a substrate binds is the ______ site.Intermediate2 pts
Why: The active site has a shape that fits the substrate.
28.The main carbohydrate storage polymer in plants is ______.Intermediate2 pts
Why: Plants store glucose as starch. Animals store it as glycogen.
29.Enzymes are biological ______ because they speed up reactions without being used up.Intermediate2 pts
Why: A catalyst speeds up a reaction without being used up.
30.Glucose and fructose are examples of simple sugars called ______.Intermediate2 pts
Why: Monosaccharides are single sugar units.
31.The permanent change in an enzyme's shape caused by high temperature or extreme pH is called ______.Advanced2 pts
Why: Denaturation destroys the shape of the active site.
32.Fats and oils belong to a group of biological molecules called ______.Advanced2 pts
Why: Fats and oils are lipids.
33.The reaction that joins two molecules and releases water is called a ______ reaction.Advanced2 pts
Why: Condensation reactions build larger molecules and release water.
34.The organelle that releases most of a cell's usable energy as ATP is the ______.Advanced2 pts
Why: Mitochondria carry out most aerobic respiration and make ATP.
35.The small units that join to form a nucleic acid such as DNA are called ______.Advanced2 pts
Why: DNA and RNA are polymers of nucleotides.

Section D — Column Matching

10 marks

Use the ▲ ▼ buttons to reorder Column B until each row lines up with the correct term in Column A. 2 marks per correct pair.

36–40.Match each term in Column A with the correct description in Column B.Advanced10 pts
Column A
Carbohydrate
Lipid
Protein
Iodine test
Biuret test
Column B
Membranes and energy storage
Starch detection
Protein detection
Energy supply or structural roles
Structure, transport, catalysis and signalling
Why: Carbohydrates supply energy or form structures; lipids form membranes and store energy; proteins have roles in structure, transport, catalysis and signalling; the iodine test detects starch; the Biuret test detects protein.

Section E — Short Answer

20 marks

5 questions · 4 marks each. Answer in one or two full sentences (at least 8 words). Marks are given for each key idea in the marking guide.

41.Explain why enzyme activity depends on three-dimensional protein structure.Advanced4 pts
42.A food gives a positive Benedict's test but a negative iodine test. What can reasonably be concluded?Advanced4 pts
43.Why is a control important when carrying out a biochemical food test?Advanced4 pts
44.Distinguish hydrolysis from condensation using biological molecules as examples.Advanced4 pts
45.Explain how membrane structure supports selective transport.Advanced4 pts
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