Carbohydrates

Carbohydrates MDCAT MCQs with answers

46 past paper MCQs on Carbohydrates, from the Biological Molecules unit of MDCAT Biology. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

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1.Monosaccharides have a general formula represented by: (MDCAT 2024)

  1. $\mathrm{C_n(H_2O)_n}$
  2. $\mathrm{C(H_2O)_n}$
  3. $\mathrm{C_6(H_2O)_n}$
  4. $\mathrm{C_n(H_2O)}$
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Correct answer: (a) $\mathrm{C_n(H_2O)_n}$

A monosaccharide carries one water for every carbon, which is what "carbohydrate" means.

2.Polysaccharides in plants are synthesized by the process of: (MDCAT 2024)

  1. hydrolysis
  2. oxidation
  3. condensation
  4. glycolysis
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Correct answer: (c) condensation

Each glycosidic bond is made by removing a molecule of water between two sugars.

3.An oligosaccharide is made up of at least: (UHS MDCAT 2025)

  1. two saccharide units
  2. ten saccharide units
  3. three to ten saccharide units
  4. more than ten saccharide units
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Correct answer: (c) three to ten saccharide units

An oligosaccharide is three to ten monosaccharide units joined by glycosidic bonds.

4.Which one of the following biomolecules is a polymer/polysaccharide? (UHS MDCAT 2025)

  1. Sucrose
  2. Pentose
  3. Lactose
  4. Glycogen
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Correct answer: (d) Glycogen

Glycogen is a branched polymer of glucose; the other three are single or double sugars.

5.Which of the following is a branched polysaccharide found in animals: (KMU MDCAT 2025)

  1. Cellulose
  2. Glycogen
  3. Amylose
  4. Chitin
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Correct answer: (b) Glycogen

Glycogen is the branched storage polysaccharide of liver and muscle.

6.A diabetic patient is advised to avoid both sucrose and lactose, because they both: (KMU MDCAT 2025)

  1. Are structural carbohydrates
  2. Increase blood glucose after hydrolysis
  3. Cannot be digested in human
  4. Act as non-caloric sweeteners
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Correct answer: (b) Increase blood glucose after hydrolysis

Both are disaccharides that hydrolyse to sugars the blood absorbs, so both raise blood glucose.

7.Identify the CORRECT option that matches the sugar with its carbon number and functional group: (KMU MDCAT 2025)

  1. Glyceraldehyde - Triose, Ketone group
  2. Ribose - Pentose, Aldehyde group
  3. Ribulose - Pentose, Aldehyde Group
  4. Galactose - Hexose, Ketone Group
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Correct answer: (b) Ribose - Pentose, Aldehyde group

Ribose is a five carbon sugar with an aldehyde group.

8.At least how many saccharide units must be present in polysaccharide? (SIBA MDCAT 2025)

  1. 1
  2. 2
  3. 10
  4. 11
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Correct answer: (d) 11

An oligosaccharide runs to ten units, so a polysaccharide begins at eleven.

9.Homopolysaccharide that is found in the cell wall of fungi and in the exoskeleton of arthropods is: (SIBA MDCAT 2025)

  1. Cellulose
  2. Glycogen
  3. Starch
  4. Chitin
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Correct answer: (d) Chitin

Chitin is a polymer of a single sugar derivative, so it is a homopolysaccharide.

10.Polysaccharides such as starch and glycogen are mainly used for: (SZABMU MDCAT 2025)

  1. Structural framework only
  2. Short-term and long-term energy storage
  3. Enzyme catalysis
  4. Ready source of energy
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Correct answer: (b) Short-term and long-term energy storage

Starch and glycogen are the storage polysaccharides of plants and animals.

11.Which of the following characteristics is common among sucrose, lactose and maltose? (SZABMU MDCAT 2025)

  1. molecular formula
  2. occurrence in living beings
  3. chemical nature of their monosaccharide units
  4. to act as reducing sugar
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Correct answer: (a) molecular formula

All three are disaccharides of formula $\mathrm{C_{12}H_{22}O_{11}}$.

12.Which monosaccharide will from a gluco pyranose ring in solution? (UHS MDCAT 2024)

  1. Fructose
  2. Glucose
  3. Ribose
  4. Deoxyribose
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Correct answer: (b) Glucose

Glucose closes into a six membered ring, the glucopyranose form.

13.Sugarcane contains ________. (KMU MDCAT 2024)

  1. Fructose
  2. Glucose
  3. Ribose
  4. Sucrose
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Correct answer: (d) Sucrose

Cane sugar is sucrose, a disaccharide of glucose and fructose.

14.Loss of reactivity of sucrose is due to its: (NUMS MDCAT 2024)

  1. High solubility in water
  2. Polar nature
  3. Unavailability of functional group
  4. Alpha 1-2 Glycosidic linkage
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Correct answer: (d) Alpha 1-2 Glycosidic linkage

Both anomeric carbons are locked in the alpha 1,2 link, so sucrose has no free aldehyde group left.

15.Upon initial hydrolysis starch yields: (UHS MDCAT 2023)

  1. Maltose
  2. Glucose
  3. Sucrose
  4. Mannose
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Correct answer: (a) Maltose

Starch is broken first to maltose and only then to glucose.

16.Which of the following carbohydrates are sweetest among all? (SZABMU MDCAT 2023)

  1. Monosaccharides
  2. Disaccharides
  3. Oligosaccharides
  4. Polysaccharides
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Correct answer: (a) Monosaccharides

The simple sugars taste sweetest, and sweetness falls as the chains grow longer.

17.Chemically, cell wall of fungi is made up of: (SZABMU MDCAT 2023)

  1. Cellulose
  2. Lignin
  3. Chitin
  4. Murein
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Correct answer: (c) Chitin

The fungal wall is chitin, the same polymer as the arthropod skeleton.

18.These carbohydrates are sweetest among all carbohydrates: (NUMS MDCAT 2023)

  1. Monosaccharides
  2. Disaccharides
  3. Oligosaccharides
  4. Polysaccharides
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Correct answer: (a) Monosaccharides

The simple sugars taste the sweetest of all the carbohydrates.

19.Most of the monosaccharides form a ring structure when in solution. For example ribose will form a five cornered ring known as (UHS MDCAT 2023)

  1. Glucopyranose
  2. Ribofuranose
  3. Glyceradehyde
  4. Acetaldehyde
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Correct answer: (b) Ribofuranose

Ribose closes into a five membered ring, the ribofuranose form.

20.Which statement is true about regarding both starch and cellulose? (UHS MDCAT 2023)

  1. They are both polymers of glucose.
  2. They are geometric isomers of each other
  3. They can both be digested by humans.
  4. They are both used for energy storage in plants.
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Correct answer: (a) They are both polymers of glucose.

Both are chains of glucose; they differ in the linkage, which is why we can digest only starch.

21.Which one of the following is a polymer of alpha-d glucose? (PMC MDCAT 2022)

  1. Cellulose
  2. Glycogen
  3. Insulin
  4. Chitin
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Correct answer: (b) Glycogen

Glycogen is a branched polymer of alpha glucose; cellulose is built of the beta form.

22.Which of the following is true about glucose and fructose? (PMC MDCAT 2022)

  1. Have the same structural formula
  2. Have different molecular formula
  3. They are building blocks of sucrose
  4. They are aldohexoses
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Correct answer: (c) They are building blocks of sucrose

Sucrose is glucose joined to fructose; the two sugars share a formula but differ in structure.

23.Which of the following is a respiratory fuel? (PMC MDCAT 2022)

  1. Sucrose
  2. Glucose
  3. Galactose
  4. Mannose
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Correct answer: (b) Glucose

Glucose is the sugar that enters glycolysis directly.

24.When alpha glucose is condensed with beta fructose, which of the following can be produced? (PMC MDCAT 2022)

  1. Maltose
  2. Lactose
  3. Water
  4. Peptide Bond
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Correct answer: (c) Water

The glycosidic link is made with the loss of a molecule of water.

25.Dietary fibers are (PMC MDCAT 2022)

  1. Cellulose
  2. Glycogen
  3. Starch
  4. Proteoglycans
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Correct answer: (a) Cellulose

Cellulose passes through us undigested and gives the diet its roughage.

26.Glucose and Ribose form ring structures when: (PMC MDCAT 2022)

  1. React with an appropriate enzyme
  2. Dissolved in water
  3. Immersed in oil
  4. They are in crystalline state
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Correct answer: (b) Dissolved in water

In water the open chain closes on itself and an equilibrium is set up between the forms.

27.At least, how many carbon atoms must be found in an amylose starch? (PMC MDCAT 2022)

  1. 7
  2. 66
  3. 70
  4. Many thousands
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Correct answer: (d) Many thousands

Amylose is a long unbranched chain of glucose units, so its carbons run into thousands.

28.The temporary storage of energy in the human body is: (PMC MDCAT 2022)

  1. Cellulose
  2. Glycogen
  3. ATP
  4. Fats
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Correct answer: (b) Glycogen

Glycogen is the short-term carbohydrate store of liver and muscle.

29.Cellulose is _____ (PMC MDCAT 2022)

  1. hexose polysaccharlde
  2. heptose polysaccharlde
  3. heteropolysaccharlde
  4. pentosepolysaccharlde
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Correct answer: (a) hexose polysaccharlde

Cellulose is a polymer of glucose, a six carbon sugar.

30.Amylopectin is ______ and insoluble in ______ (PMC MDCAT 2022)

  1. branched sugar, water
  2. unbranched sugar, ethanol
  3. branched sugar, cold water
  4. unbranched sugar, hot water
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Correct answer: (a) branched sugar, water

Amylopectin is the branched fraction of starch and does not dissolve in cold water.

31.Reducing sugar among the following is: (PMC MDCAT 2022)

  1. galactose
  2. gluconic acid
  3. glycogen
  4. sucrose
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Correct answer: (a) galactose

Galactose has a free aldehyde group, so it reduces Fehling’s solution.

32.Maximum how many carbon atoms does an oligosaccharide contain? (PMC MDCAT 2022)

  1. 3
  2. 7
  3. 70
  4. Many thousands
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Correct answer: (c) 70

An oligosaccharide runs to ten units, and a hexose unit has six carbons, so about seventy at most.

33.Which of the following is milk sugar? (PMC MDCAT 2022)

  1. Sucrose
  2. Lactose
  3. Maltose
  4. Starch
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Correct answer: (b) Lactose

Lactose is the sugar of milk.

34.Which of the following is not a carbohydrate: (NUMS MDCAT 2022)

  1. Glucose (C6H12O6)
  2. Sucrose (C12H22O11)
  3. Rhamnose (C6H12O5)
  4. Lactic acid (C2H4O2)
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Correct answer: (d) Lactic acid (C2H4O2)

Lactic acid is a carboxylic acid, not a sugar or a polymer of one.

35.Which of the following molecules would yield glucose and fructose on hydrolysis? (NUMS MDCAT 2022)

  1. Starch
  2. Maltose
  3. Sucrose
  4. Lactose
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Correct answer: (c) Sucrose

Sucrose is glucose joined to fructose.

36.How many monosaccharide molecules do oligosaccharides yield upon hydrolysis? (PMC Practice 2021)

  1. 2
  2. 5
  3. 10
  4. All of these
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Correct answer: (d) All of these

An oligosaccharide yields from two to ten monosaccharide units.

37.Which bond provides stability to complex carbohydrate molecules? (PMC Practice 2021)

  1. C-H
  2. C-N
  3. C-O
  4. C-C
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Correct answer: (c) C-O

The glycosidic link between sugar units is a carbon oxygen bond.

38.Starch is present in tubers, fruits, and grains but absent in animal cells. Instead, animals have a substance stored in liver and muscles known as: (UHS MDCAT 2019)

  1. Galactose
  2. Glucagon
  3. Glycogen
  4. Glucose
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Correct answer: (c) Glycogen

Glycogen is the storage polysaccharide of liver and muscle.

39.Which is an example of a Disaccharide? (UHS MDCAT 2019)

  1. Starch
  2. Lactose
  3. Fructose
  4. Glycogen
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Correct answer: (b) Lactose

Lactose is glucose joined to galactose.

40.The covalent bond or bridge between two monosaccharides to form a disaccharide is called a: (UHS MDCAT 2019)

  1. Hydroxyl bond
  2. Hydrogen bond
  3. Carboxyl bond
  4. Glycosidic bond
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Correct answer: (d) Glycosidic bond

The link between two sugar units is a glycosidic bond.

41.Glycosidic bond is formed by the: (UHS MDCAT 2018)

  1. Removal of Oxygen
  2. Addition of Oxygen
  3. Removal of water
  4. Addition of water
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Correct answer: (c) Removal of water

The glycosidic bond is made by condensation, with a molecule of water lost.

42.The type of carbohydrate which has high molecular weight and is sparingly soluble in water is: (UHS MDCAT 2017)

  1. Monosaccharides
  2. Disaccharides
  3. Polysaccharides
  4. Maltose
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Correct answer: (c) Polysaccharides

A polysaccharide is a long chain, so it is heavy and barely soluble.

43.Give the general formula of monosaccharides and polysaccharides. (UHS MDCAT 2017)

  1. (CH2O)n and Cn(H2O)2n
  2. (CH2O)2n and Cn(H2O)n
  3. (CH2O)n and Cn(H2O)n-1
  4. (CH2O)n-1 and Cn(H2O)n+1
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Correct answer: (c) (CH2O)n and Cn(H2O)n-1

A monosaccharide is $(\mathrm{CH_2O})_n$; a polysaccharide loses a water at each link.

44.In a laboratory experiment when an unknown compound was added in a test tube containing iodine, the colour became intense blue. What could be the unknown compound? (UHS MDCAT 2016)

  1. Cellulose
  2. Raffinose
  3. Ribose
  4. Starch
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Correct answer: (d) Starch

Starch gives the deep blue colour with iodine.

45.The compounds which on hydrolysis yield polyhydroxy aldehyde or ketone subunits are: (UHS MDCAT 2016)

  1. Lipids
  2. Proteins
  3. Polynucleotides
  4. Carbohydrates
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Correct answer: (d) Carbohydrates

A carbohydrate hydrolyses to polyhydroxy aldehydes or ketones, that is to simple sugars.

46.Monosaccharides are major components of: (UHS MDCAT 2015)

  1. DNA, ATP, Ribulose bisphosphate and Cysteine
  2. DNA, NAD and Insulin
  3. DNA, NADP, ATP and Ribulose bisphosphate
  4. DNA, RNA and Myosin
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Correct answer: (c) DNA, NADP, ATP and Ribulose bisphosphate

Ribose and deoxyribose are the sugars of the nucleic acids, of ATP and of ribulose bisphosphate.

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