4.1

Biological molecules

12 flashcards to master Biological molecules

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Definition Flip

What chemical elements make up carbohydrates?

Answer Flip

Carbohydrates are composed of carbon, hydrogen, and oxygen. Examples include glucose (C6H12O6) and starch, which are vital energy sources for organisms like plants and animals.

Definition Flip

What chemical elements make up fats?

Answer Flip

Fats are composed of carbon, hydrogen, and oxygen, but with a lower proportion of oxygen compared to carbohydrates. An example is triglycerides, which are important for energy storage in adipose tissue in mammals.

Definition Flip

What chemical elements make up proteins?

Answer Flip

Proteins are composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

Example: enzymes are proteins that catalyze biochemical reactions in organisms like the digestion of food in the human stomach.
Key Concept Flip

What smaller molecules make up starch, glycogen, and cellulose?

Answer Flip

Starch, glycogen, and cellulose are all made from glucose molecules. Starch is found in plants (

Example: potatoes), glycogen in animal liver and muscle cells, and cellulose forms plant cell walls, providing structure to plants.
Key Concept Flip

What smaller molecules make up proteins?

Answer Flip

Proteins are made from amino acids. These amino acids link together via peptide bonds to form polypeptide chains. For instance, haemoglobin in red blood cells is a protein made from amino acids.

Key Concept Flip

What smaller molecules make up fats and oils?

Answer Flip

Fats and oils are made from fatty acids and glycerol. These combine to form triglycerides.

Example: fats stored in seeds provide energy for germination, and oils like olive oil are used for cooking.
Key Concept Flip

Describe the iodine solution test and its expected result for starch.

Answer Flip

Add iodine solution to the sample. If starch is present, the iodine solution will change from brown to blue-black.

Example: testing a potato slice will result in a blue-black color due to the presence of starch.
Key Concept Flip

Describe the Benedict's solution test and its expected result for reducing sugars.

Answer Flip

Add Benedict's solution to the sample and heat. If reducing sugars are present, the solution will change color from blue to green, yellow, orange, or brick red, depending on the concentration of sugar.

Example: testing glucose solution will result in a brick-red color if the glucose concentration is high.
Key Concept Flip

Describe the Biuret test and its expected result for proteins.

Answer Flip

Add Biuret reagent to the sample. If protein is present, the solution will change from blue to purple.

Example: testing egg white will result in a purple color because of its high protein content.
Key Concept Flip

Describe the ethanol emulsion test and its expected result for fats and oils.

Answer Flip

Dissolve the sample in ethanol, then add water. If fats or oils are present, a cloudy white emulsion will form.

Example: testing milk will result in a cloudy white emulsion due to the presence of fat.
Key Concept Flip

Describe the DCPIP test and its expected result for vitamin C.

Answer Flip

Add the sample dropwise to DCPIP solution until the blue colour disappears. The volume of sample needed indicates the amount of vitamin C. Lemon juice will quickly decolourise DCPIP due to high vitamin C content.

Definition Flip

Describe the structure of a DNA molecule.

Answer Flip

DNA consists of two strands coiled together to form a double helix. Each strand contains bases (A, T, C, G). Bases pair up specifically: A with T, and C with G, held together by bonds between the base pairs. The sequence of these bases encodes genetic information in organisms, like eye colour in humans.

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3.3 Active transport 5.1 Enzymes

Key Questions: Biological molecules

What chemical elements make up carbohydrates?

Carbohydrates are composed of carbon, hydrogen, and oxygen. Examples include glucose (C6H12O6) and starch, which are vital energy sources for organisms like plants and animals.

What chemical elements make up fats?

Fats are composed of carbon, hydrogen, and oxygen, but with a lower proportion of oxygen compared to carbohydrates. An example is triglycerides, which are important for energy storage in adipose tissue in mammals.

What chemical elements make up proteins?

Proteins are composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

Example: enzymes are proteins that catalyze biochemical reactions in organisms like the digestion of food in the human stomach.
Describe the structure of a DNA molecule.

DNA consists of two strands coiled together to form a double helix. Each strand contains bases (A, T, C, G). Bases pair up specifically: A with T, and C with G, held together by bonds between the base pairs. The sequence of these bases encodes genetic information in organisms, like eye colour in humans.

About Biological molecules (4.1)

These 12 flashcards cover everything you need to know about Biological molecules for your Cambridge IGCSE Biology (0610) exam. Each card is designed based on the official syllabus requirements.

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