Carbohydrates & Lipids (DP IB Biology: SL)

The table below contains statements that could apply to three polysaccharides. Complete the table with a tick (✓) in each box if the statement applies correctly

Explain the name of the type of reaction that forms the carbohydrates in part (a) from their monomers.

State one feature of starch and explain how this feature allows it to act as a storage substance.

Two molecules of a disaccharide are condensed together to form a larger sugar molecule. The chemical formula of the disaccharide is C₁₂H₂₂O₁₁.

Deduce the formula of the resulting larger sugar molecule.

Sucrose is formed from monosaccharides X and Y.

The diagram below shows the structure of sucrose and monosaccharide Y.

Draw and identify monosaccharide X.

Fructose and glucose have the same molecular formula, C₆H₁₂O₆. However, their differing structures give them different properties; for example, fructose tastes sweeter than glucose.

Suggest one advantage to the food industry of this difference.

Molecular analysis was carried out using various laboratory techniques to distinguish between samples of three different polysaccharides. Starch was separated into its constituent polysaccharides (amylose and amylopectin) before analysis. The results are shown in the table below.

The three samples were amylopectin, glycogen and amylose (not necessarily in that order).

Use your knowledge of polysaccharide structure to assign each sample to one of those three polysaccharides.

Within animal cells, fats are used as a long-term energy storage. A carbohydrate, glycogen, is used as a short-term energy storage molecule as well.

Explain the benefits of having this kind of short-term storage system.

The diagram below shows an incompletely-drawn triglyceride molecule.

Complete the drawing to show a trans-monounsaturated fatty acid chain at position 1 of the glycerol molecule. 

As part of a 50-year study into health and diet, data was gathered in 1960 and 2000 for the numbers of deaths due to cardiovascular disease in a western European country. This data was compared to the percentage of energy provided by trans-fats in the diets of elderly men (aged 70 and above). Some of the research findings are shown below.

Calculate the percentage decrease in numbers of deaths from cardiovascular disease between 1960 and 2000.

Referring to the study described in (b), post-mortem investigations of some patients who had died from cardiovascular disease revealed that fatty deposits in their diseased arteries contained high concentrations of trans-fats.

Explain why this finding, though positively correlated, does not prove causation.

Trans-fats have been favoured by manufacturers of processed foods.

Outline how one structural property of trans-fatty acids makes trans-fats a more attractive ingredient of choice for processed food manufacturers.

Label the four components A-D of a low-density lipoprotein (LDL) complex shown in the diagram below.

State one function of a lipoprotein complex such as that illustrated in question (a).

The graph below shows the data obtained by scientists investigating the effect of omega-3 fatty acid consumption on the relative risk of coronary heart disease in humans.

Figure 1

Using the data in the graph, evaluate whether coronary heart disease can be prevented by increasing omega-3 intake.

Omega-3 fats are all examples of lipids that contain polyunsaturated cis-fatty acids. In the space below, draw the appearance of one carbon-to-carbon double bond as found in a cis-fatty acid's structure. You should include in your drawing all atoms connected to each carbon atom in that double bond.

One mark is available for clarity of communication throughout this question.

Draw a diagram of a section of a molecule of cellulose.

Your drawing should contain no fewer than three monomers joined together.

Outline why lipids are more suitable for long-term energy storage than carbohydrates in animals.

Discuss the advantages and disadvantages of using Body Mass Index (BMI) as a measure of a person's health.

Your answer should include a description of how BMI is calculated, with units, in the absence of a nomogram.

The following diagram shows the structure of a polysaccharide found in plant cells.

Identify the polysaccharide pictured in the diagram.

[1]

[1]

Molecular visualisation software such as Jmol can be used to depict biological molecules.

Identify the molecule in this Jmol visualisation. 

Three molecules of the same monosaccharide are joined in a line into a trisaccharide. 

The molecular formula of the monosaccharide is C₅H₁₀O₅.

Deduce the formula of the resulting trisaccharide. 

The tetrasaccharide stachyose has the molecular formula C₂₄H₄₂O₂₁.

Describe two aspects of its molecular formula that identifies stachyose as a carbohydrate.

A disaccharide has the formula C₁₂H₂₂O₁₁

It is made up of two identical monosaccharides. 

Deduce the formula of the monosaccharides that form the disaccharide.

Draw a molecular diagram of a 10-carbon saturated fatty acid.

Explain why unsaturated fatty acids form different shaped-triglycerides whereas saturated fatty acids do not. 

Below is a typical label printed on a piece of food packaging.

The product in question is a cookie-style snack food, sold in small packets with see-through plastic packaging. 

Suggest and explain one aesthetic reason why a food company might wish to market such a food product despite its high saturated fat content. 

Doctors recommend that the majority of dietary fat intake should come from monounsaturated and polyunsaturated fats. 

Explain why. 

Typical energy content values of various food group molecules are given in the table below. 

State the molecular feature of fats that allows them to contain more energy per gram than carbohydrates or proteins.

The diagram shows a cell with a role in storage.

Identify structures X, Y and Z in this diagram.

[3]

Suggest which tissue this cell forms part of.

[1]

A person's body mass index is 26.4 and their mass is 78.3kg.

Calculate the person's height in metres, to 2 decimal places. The formula for BMI is shown below:

A newspaper heading states that "High fat diets lead to weight loss!" based on the following study and data. 

Scientists carried out a study across five years in which 8254 participants followed one of three diets:

• a Mediterranean diet with added extra virgin olive oil
• a Mediterranean diet with added nuts
• a low fat diet 

None of the diets involved reducing calories or increasing physical activity.

The graph below shows the results of weight loss in participants after five years.

Use the data and information provided to evaluate the newspaper's claim. 

Explain why cholesterol forms associations with proteins called lipoproteins eg. LDL (low density lipoproteins) and HDL (high density lipoproteins).

Outline the series of events by which low density lipoproteins (LDLs) raise the risk of a person suffering from coronary heart disease. 

Many claims about the health benefits and drawbacks of food are made. One such is the claim that a high consumption of trans- fats causes coronary heart disease. 

Evaluate this claim. 

One mark is available for clarity of communication throughout this question.

Compare and contrast the compounds glycogen and starch. 

Sketch a labelled diagram of the part of a trans-fatty acid that identifies its chemical structure as trans-.

A healthy 35 year-old man of height 1.75m has a mass of 95kg. 

He calculated correctly that his Body Mass Index was 31, which places him in the 'obese' category. Online sources he read gave him cause for concern about his future health prospects. 

Evaluate the claim that a BMI of 31 is detrimental to his health.