Chap 3: Biological molecules Flashcards
What are carbohydrates?
Carbohydrates are organic molecules made up of carbon, hydrogen, and oxygen in a ratio of 2:1.
What are simple sugars?
Simple sugars are the basic units of carbohydrates that can pass through cell membranes. Examples include glucose and fructose.
What are double sugars?
Double sugars are formed when two single sugars join together. Examples include maltose and sucrose.
How can a double sugar be split into two single sugar molecules?
Enzymes, such as maltase, can split a double sugar into two single sugar molecules.
What are reducing sugars?
Reducing sugars include glucose, fructose, and maltose.
What are complex carbohydrates?
Complex carbohydrates are made up of many similar molecules of single sugar joined together to form a large molecule.
What are the types of complex carbohydrates?
The types of complex carbohydrates include starch, cellulose, and glycogen.
What is the role of starch in plants?
Starch is the storage form of carbohydrates in plants and can be digested to glucose for energy.
What is the role of cellulose in plants?
Cellulose forms the cell wall of plants, protecting them from bursting or damage. It serves as dietary fiber and cannot be digested in our intestines.
Where is glycogen stored in mammals?
Glycogen is stored in the liver and muscles of mammals as a storage form of carbohydrates.
Why are glycogen and starch suitable as storage materials in cells?
Glycogen and starch are insoluble in water, do not change water potential in cells, cannot diffuse through cell membranes, can be easily broken down to glucose when needed, and have compact shapes that occupy less space.
How is starch broken down in the body?
Starch is broken down by amylase into maltose, which is further broken down by maltase into glucose.
What are the functions of carbohydrates?
- Providing energy for respiration
- Forming supporting structures like cellulose in plants
- Conversion to organic compounds like amino acids and fats
- Formation of nucleic acids like DNA
How can you test for the presence of starch?
The iodine test can be conducted by adding iodine solution to a food sample. If it turns blue-black, starch is present.
What are fats?
Fats are organic molecules composed of carbon, hydrogen, and oxygen, with a higher proportion of hydrogen compared to carbohydrates.
How are fats broken down?
Fats can be broken down into fatty acids and glycerol through the action of lipase.
What are the sources and functions of fats?
Sources: Oils, fatty meat, and fish
Functions: Long-term storage of energy, insulation, solvent for fat-soluble vitamins, essential for cell membranes, reduce water and heat loss from skin surface
How can you test for the presence of fats?
The ethanol emulsion test involves mixing the sample with ethanol and observing the formation of a white emulsion to indicate the presence of fats.
What elements make up proteins?
Proteins are composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
What are the sources and functions of proteins?
Sources: Meat, milk, eggs, seafood, plant foods (soya beans, nuts, grains, vegetables)
Functions: Growth and repair of body cells, synthesis of enzymes and hormones, formation of antibodies
How can you test for the presence of proteins?
The biuret test involves adding a food sample to biuret solution and observing a color change to violet, indicating the presence of proteins.
What are simple sugars commonly found in plants and animals?
Glucose and fructose.
How are maltose and sucrose formed?
Maltose is formed by joining two glucose molecules, and sucrose is formed by joining glucose and fructose molecules.
How can you test for the presence of reducing sugars?
Benedict’s solution can be used to test for reducing sugars. The color change from blue to green, yellow or orange, and red or the formation of a red precipitate indicates the presence of reducing sugars.
