Life Sciences Grade 10 Revision 2 | Past Paper Questions & Answers Explained

Life Sciences Grade 10

Religion Studies Grade 10 : Study Guide | Past Paper Questions and Answers | Revision 2

The table below shows amounts of different types of food eaten by a learner and organic compounds. The total of organic compounds she ate is 144,9 grams 

Question : Organic Compounds in Food

The table shows the amounts of carbohydrates, proteins, and fats found in different foods eaten by a learner. The total mass of organic compounds consumed is 144.9 grams.

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Question: Identify the food type that is made mostly of fats.

The food type that is made mostly of fats is peanut butter.

From the table, peanut butter contains 50 grams of fats, which is far higher than its carbohydrate (20 grams ) and protein (25 grams ) content. This shows that fats are the main organic compound present in peanut butter.

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Question: State the monomers of fats.

The monomers of fats are fatty acids and glycerol.

Fats are complex molecules that are broken down during digestion into fatty acids and glycerol. These smaller units are absorbed by the body and used for energy storage, insulation, and cell structure.

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Question: Calculate the value of A, Show all working.

We follow the steps below to calculate the value of A.

Firstly we been given the Total organic compounds eaten = 144.9 g

Step 1: Calculate the total known mass from the table

For Potatoes we have:

Carbohydrates = 17 g ,  Proteins = 2 g , Fats = 0 .1 g , giving us a  Total  of 19. 1 g

For Chicken (excluding protein A) we have

Carbohydrates = 0 grams, Fats = 3 . 8 g giving us a total of  3.8 g

For Peanut butter we got, Carbohydrates = 20 g, Proteins = 25 g, Fats = 50 g giving a total of 95 g

Therefore the Total known mass is 19 .1 g + 3 .8 g + 95 g which gives a total of 117 .9 g

Step 2: Calculate the missing value (a)

144 point 9 g – 117 . 9 g = 27 g

Hence The value of A, = 27 g

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Question: Give the chemical reagent used to test for proteins.

The chemical reagent used to test for proteins is Biuret reagent. (Millon’s reagent can also be used)

When Biuret reagent is added to a substance containing proteins, the solution changes from blue to purple, confirming the presence of proteins.

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Question: Explain the colour change when a starch test using iodine is done on the potatoes.

When iodine solution is added to potatoes, the colour changes from brown to blue-black.

The diagram below shows a plant cell

Question: Name the useful substances that part B contains

Part B represents the vacuole. The vacuole stores useful substances such as sugars, which are used as an energy source, minerals, which support various metabolic processes, and pigments dissolved in water, which may contribute to colour in plant tissues and help attract pollinators.

Question: State the function of part C

Part C represents the nucleus and performs the following functions 

1, The nucleus controls the activities of the cell by acting as the control centre. It regulates important processes such as growth, metabolism, protein synthesis, and cell division, ensuring that the cell functions properly.

2, The nucleus also transmits hereditary characteristics from parents to offspring. It contains DNA, which carries genetic information responsible for inherited traits. During reproduction, this genetic material is passed on, ensuring continuity of characteristics across generations.

Question: Give the Letter and the Name of the part that is selectively permeable

The selectively permeable structure in the plant cell is labeled A, and it is called the cell membrane. The cell membrane controls the movement of substances into and out of the cell, allowing essential materials such as oxygen, water, and nutrients to enter while preventing harmful substances from passing through freely.

This selective permeability helps maintain a stable internal environment within the cell. By regulating the exchange of materials, the cell membrane ensures that cellular processes occur efficiently and that the cell remains healthy and function.

Question: Explain the advantage for this cell having many part D’s

Part D, represents the chloroplasts. Having many chloroplasts increases the rate of photosynthesis in the cell. More chloroplasts mean that a larger surface area is available to absorb light energy, which allows the plant to produce more glucose for energy and growth.

Chloroplasts contain chlorophyll, which traps light energy needed for photosynthesis. When a cell has many chloroplasts, it can manufacture more food, supporting faster growth and providing energy for other life processes of the plant.

Question : Cell Structure

The diagram below represents the cell structure.

Question: Does the diagram represent a plant cell or an animal cell?

The diagram represents a plant cell. This is evident because it contains structures that are unique to plant cells and are involved in support and food production.

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Question: Give Three visible reasons why the cell is a plant cell.

One visible reason is the presence of a cell wall, which provides strength and support to the cell. Animal cells do not have a cell wall.

Another visible reason is the presence of chloroplasts, which contain chlorophyll and are responsible for photosynthesis. Chloroplasts are found only in plant cells.

A third visible reason is the presence of a large central vacuole, which stores water and dissolved substances and helps maintain the shape of the cell. Animal cells do not have a large permanent vacuole.

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Question : Identify part C in the diagram.

Part C is the cytoplasm. The cytoplasm is a jelly-like substance that fills the cell and holds all organelles in place. Most metabolic reactions in the cell occur in the cytoplasm.

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Question: Identify part E in the diagram.

Part E is the cell membrane. The cell membrane surrounds the cytoplasm and controls the movement of substances into and out of the cell.

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Question: Give the Letter of the part that controls cell activities.

The letter is D. Part D represents the nucleus, which controls all cell activities and contains the genetic material of the cell.

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Question: Give the Letter of the part that releases energy during cellular respiration.

The letter is A. Part A represents the mitochondrion, where glucose is broken down using oxygen to release energy for the cell.

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Question: Describe how part E is adapted to its function.

Part E, the cell membrane, is selectively permeable. This means it allows certain substances such as oxygen and nutrients to enter the cell while preventing harmful substances from entering, thereby maintaining a stable internal environment

The table below shows nutritional information for some common food sources and organic compounds.

Question: Name the food source that would be best suited to provide high amounts of energy.

Potatoes are the best food source for providing high amounts of energy. This is because potatoes contain a large quantity of carbohydrates. Carbohydrates are broken down into glucose during digestion, and glucose is used by cells during respiration to release energy.

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Question: Name the food source that has the least amount of protein.

Bananas have the least amount of protein. They contain only small quantities of protein compared to the other foods listed. Bananas mainly supply carbohydrates and vitamins rather than building nutrients such as proteins.

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Question : Write down Two organic compounds that are found in high amounts in sausages.

Sausages contain a high amount of protein. Proteins are needed for growth, repair of body tissues, and the formation of enzymes and hormones. Since sausages are made from animal tissue, they naturally contain large amounts of protein.

Sausages also contain a high amount of fats. Fats provide long-term energy, help insulate the body, and protect internal organs. Processed meats such as sausages often have added fats, increasing their fat content.

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Question: What are the monomers of proteins?

The monomers of proteins are amino acids. Amino acids are small molecules that join together in long chains to form proteins. The sequence and type of amino acids determine the function of each protein.

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Question: Name the chemical reagent used to test for proteins.

The chemical reagent used to test for proteins is the Biuret reagent. When the Biuret reagent is added to a food sample containing protein, it changes colour from blue to purple. This colour change occurs because the reagent reacts with peptide bonds in proteins.

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Question: Describe how to test for the presence of starch in a food sample.

To test for starch, a few drops of iodine solution are added to the food sample. If starch is present, the iodine changes colour from brown to blue-black. If the colour remains brown, it shows that starch is absent from the sample.