IBBiologySLTopic QuestionsForm & FunctionCarbohydrates & Lipids

Syllabus Edition

First teaching 2023

First exams 2025

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Carbohydrates & Lipids (SL IB Biology)

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11 mark

Carbon is one of the most abundant elements found in the molecules of living organisms. 

Which of the following statements does not refer to a property of carbon that allows it to play an integral biochemical role in the molecules of living things. 

  • It has four electrons in its outer shell meaning it can form four covalent bonds with other atoms

  • When it bonds with hydrogen it creates a dipole that allows it to form hydrogen bonds with water and other polar molecules

  • It can form double and triple bonds with adjacent carbon atoms to allow unsaturated compounds to form

  • Produces a tetrahedral-shaped structure which allows the formation of varied carbon compounds which have different 3-D shapes

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2
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Which of the following bonds link two monosaccharides together to form a disaccharide?

  • Hydrogen

  • Ester

  • Glycosidic

  • Peptide

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3
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The diagram below shows a component of a triglyceride.

e-2

Which of the following correctly identifies this component?

  • Saturated fatty acid

  • Monounsaturated fatty acid

  • Polyunsaturated fatty acid

  • Phospholipid

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4
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Which of the following features does not explain why lipids are excellent long-term storage compounds?

  • They can be saturated or unsaturated

  • Less body mass is required to store a given amount of energy

  • They are insoluble and will not affect the osmolarity of the cell

  • Lipids are energy dense molecules

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5
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Which of the following are involved in the formation of lipids?

   I. condensation

   II. amino acids

   III. hydrolysis

   IV. fatty acids

  • I and II

  • I and IV

  • II and III

  • II, III and IV

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11 mark

Which property of carbon makes it a good basis for organic molecules?

  • It exists in hard and stable forms like graphite and diamond.

  • It forms a varying number of covalent bonds to other atoms.

  • It can form millions of different compounds in association with hydrogen and oxygen.

  • It forms strong, ionic bonds with other atoms.

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21 mark

Two biological molecules are shown in Diagram 1 below.q1-2-2-carbohydrated-lipids-medium-ib-hl-biology

Which row of the table correctly identifies features of these molecules?

  Molecule 1 Molecule 2
A Has 3 fatty acid chains Fatty acid chains are all saturated
B Contains 3 glycosidic bonds Has 2 ester bonds and a phosphate group
C Has 3 saturated fatty acid chains Has 1 unsaturated fatty acid chain
D Molecule is polar Molecule is polar

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    31 mark

    The molecular structure of starch makes it suited to its function.

    Which statement best explains why?

    • Many condensation reactions, in the breakdown of amylose and amylopectin, release stored energy.

    • Many hydrolysis reactions, in the formation of amylose and amylopectin, allow the release of stored energy to fuel cellular processes.

    • Amylose has a branched structure and amylopectin is coiled to give a compact structure for transport around the plant through the phloem.

    • The amylose-amylopectin complex is insoluble, so it does not affect the osmolarity of the cell.

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    41 mark

    There is a naturally-occurring polysaccharide which has the structure of an unbranched chain of the molecule acetylglucosamine held together by β-1,4 glycosidic bonds. Between these unbranched chains are many types of a much weaker bond.

    There are –CH2OH groups that alternate on each side of the polysaccharide chain.

    Which of the following polysaccharides has a structure similar to that described above?

    • Glycogen 

    • Cellulose 

    • Amylopectin 

    • Amylose

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    51 mark

    Which of the structures in Diagram 2 correctly shows the structure of β-glucose and of α-glucose?

    q4-2-2-carbohydrated-lipids-medium-ib-hl-biology

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      61 mark

      Which of the following statements correctly describes a feature of carbohydrates OR lipids?

      • Glycosidic bonds form during hydrolysis reactions, joining monosaccharides together to form disaccharides and polysaccharides.

      • A triglyceride is an example of a polymer as it is formed from many smaller, repeating subunits joined together by covalent bonds. 

      • A triglyceride is not an example of a polymer although it is formed from smaller subunits joined together. 

      • Glycosidic bonds join disaccharides together to form monosaccharides and polysaccharides.

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      71 mark

      Which of the following occurs when sucrose is formed from monosaccharides?

      • Condensation of glucose and fructose, using water.

      • Condensation of glucose and galactose, using water.

      • Condensation of glucose and fructose, releasing water.

      • Condensation of glucose and galactose, releasing water.

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      81 mark

      Apart from being used for energy storage, lipids have a number of other roles. Which of the following is not a role of whole lipids?

      • Protection for soft internal organs.

      • Buoyancy aid. 

      • Improving intestinal absorption of nutrients. 

      • Regulators of gene expression. 

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      91 mark

      Which of the following chemical formulae shows a carbohydrate molecule?

      • C18H34O2

      • C18H32O16

      • C18H32O2

      • C3H8O3

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      10
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      Which is the correct reason that cellulose passes through the gut undigested?

      • There are no enzymes present in the human digestive system capable of cellulose digestion.

      • Cellulose is not a required nutrient of the human body.

      • Cellulose provides bulk for effective peristalsis which forces the food through the alimentary canal.

      • It takes too long for the glucose monomers in cellulose to be hydrolysed, so cellulose is egested before it can be digested.

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      1
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      The diagram below shows several different biological molecules (Q, R, S and T).

      kuoJPYLt_h-1

      Which row of the table below correctly identifies some of the products of hydrolysis of the molecules above?

        Q R S T
      A. α-glucose ß-glucose α-glucose glycerol
      B. α-glucose ß-glucose ß-glucose fatty acids
      C. ß-glucose α-glucose ß-glucose glycerol
      D. ß-glucose α-glucose α-glucose fatty acids

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        2
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        A study was conducted to investigate the effect of different fatty acids on the levels of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) in the human bloodstream. An increase in LDL levels in the blood has been linked to an increase in the risk of developing coronary heart disease (CHD). The results are shown in the graphs below.
        h-2

        Which of the following conclusions would be the most valid concerning the data?

        • trans monounsaturated fatty acids led to the most significant change in the HDL levels, leading to a decreased risk of developing CHD

        • All the fatty acids led to an increase in the HDL levels in the bloodstream, which would lead to a decrease in the risk of developing CHD

        • cis monounsaturated fatty acids caused the greatest decrease in LDL levels and would result in a lowered risk of developing CHD

        • cis monounsaturated fatty acids led to a smaller decrease in LDL levels than cis polyunsaturated fatty acids which would lead to a greater decrease in the risk of developing CHD

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        3
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        Which of the following most accurately describes the formation of a lipid?

        • An ester bond forms between the -COOH group of three fatty acids and an -OH group on one glycerol molecule, along with the release of three molecules of water

        • An ester bond forms between the -COOH group of three fatty acids and a -CH group on one glycerol molecule, along with the release of three molecules of water

        • An ester bond forms between the -COOH group of three fatty acids and an -OH group on one glycerol molecule, along with the absorption of three molecules of water

        • An ester bond forms between the -COOH group of three fatty acids and a -CH group on one glycerol molecule, along with the absorption of three molecules of water

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        4
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        A study was conducted to investigate the effect of saturated fat intake on the risk of developing coronary heart disease (CHD) in women.

        • The study involved 20 women, aged between 35 and 50, divided into two groups (A and B) of 10.
        • Group A was given a diet rich in saturated fats, while group B followed a diet low in saturated fats.
        • The levels of low-density lipoprotein (LDL) in their blood was monitored over a six month period. High LDL levels has been linked to an increase in the risk of developing CHD.

        At the end of the study the levels of LDL in group A was much higher than that of group B. The scientists concluded that saturated fats increases the risk of developing CHD.

        Which evaluation of their conclusion would be most valid?

        • The conclusion of the scientist may not be valid as they would have to repeat the investigation over a longer period of time, using animal test subjects

        • The conclusion of the scientists may not be valid as they should have monitored a larger number of women between the ages of 20 and 35

        • The conclusion of the scientists may not be valid as they should have taken into consideration the medical history of the women

        • The conclusion of the scientists may not be valid as they should have repeated their investigation with women over the age of 75

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