Chapter 3: Biological Molecules Flashcards
What are carbohydrates?
They are organic moelcules made up of the elements carbon, hydrogen, oxygen.
How can carbs be classified as?
Simple sugars, double sugars or complex carbohydrates.
What are simple sugars?
They are the basic unit of a carbohydrate.
What can simple sugars do in cells?
They can pass through the cell membrane and can be absorbed into the cells.
What are the 2 common single sugars?
Glucose and fructose.
How is a double sugar formed?
When 2 single sugars are joined together.
What are the 2 common double sugars?
Maltose and sucrose.
How can a double sugar be split into 2 single sugars?
By an enzyme.
What are reducing sugars?
Glucose, fructose and maltose
How do we test for reducing sugars?
Reducing sugars will form a red precipitate when boiled with Benedict’s solution.
What is a complex carbohydrate?
It is made up of many similar molecules of a single sugar joined together to form a large molecule.
What are examples of complex carbohydrates that are made up of numerous glucose molecules?
Starch, glycogen, cellulose.
What is the structure of a starch molecule?
A starch molecule is made up of several thousand glucose molecules joined together.
What are the roles of starch?
- It is a store of carbohydrates in plants.
- When needed, it can be digested to glucose to provide energy for cell activities.
Where can starch be found in?
In storage organs of plants.
What is the structure of a cellulose molecule?
It is made up of many glucose molecules joined together.
What are the roles of cellulose?
- The cellulose cell wall protects the cell wall from bursting or damage
- Cellulose cannot be digested in our intestines.
- They serve as dietary fibre that prevents constipation.
Where can cellulose be found in?
Cell walls of plants.
What is the structure of glycogen?
It is a branched molecule and is made up of many glucose molecules joined together
What are the roles of glycogen?
- It is the main store of carbohydrates in mammals
- When needed, it is digested to glucose to provide energy for cell activities.
Where can glycogen be found in?
In the liver and muscles of mammals.
How do plants store glucose?
They store glucose in the form of starch
Animals cannot ________starch in their bodies.
make or store
Where do animals get most of their carbohydrates from and in what form?
From plants in the form of starch
Tell me the relationship between starch, glucose and glycogen.
Starch is consumed and digested by animals, forming glucose, which is then stored in animals as glycogen
Why are glycogen and starch suitable as stores in cells?
- They are insoluble in water, so they do not change the water potential in the cell.
- They are large molecules that cannot diffuse through cell membranes, so they will not be lost from the cell.
- They can be easily broken down into glucose when needed.
- Their molecules have compact shapes, so they occupy less space than all the individual glucose molecules that make up a glycogen or starch molecule.
What happens when starch is digested?
- The bonds within the polysaccharide are broken and the glucose molecules are released. 2. Amylase cannot break down maltose into glucose.
- Maltose is hydrolysed to glucose by maltase.
- Complete digestion of starch gives glucose molecules.
What are the functions of carbohydrates?
- They are needed as a substrate for respiration and to provide energy for all cell activites.
- To form supporting structures
- To be converted into other organic compounds.
- For the formation of nucleic acids
- To synthesise lubricants.
- To synthesise the nectar in some flower
How can we test for starch?
Iodine - any substance containing starch will produce a blue-black colour
What are fats?
They are a type of lipid and are organic molecules made up of the elements carbon, hydrogen and oxygen.
What is the difference between the elements used to make up carbs and fats?
Though they both are made up of the same elements, fats have much less oxygen in comparison to carbs.
What are fats commonly used as?
A store of energy.
What can fats be broken down into?
Fatty acids and glycerol
What are the functions of fats?
- It is a source and long-term storage of energy
- It is an insulating material that prevent excessive heat loss.
- It is a solvent for fat-soluble vitamins and many other vital substances
- It is an essential part of cells, especially in the cell membrane
- It is a way to reduce water loss from the skin surface.
Why are fats a suitable long term-storage material?
Fats have a higher energy value compared to carbohydrates.
How do fats reduce water loss from the skin surface?
Glands in the skin secrete an oily substance. This oily substance forms a thin layer over the skin surface, reducing the rate of evaporation of water.
What other function does the oily substance secreted from your skin have?
It helps to reduce heat loss from the skin.
How can we test for fats?
Ethanol emulsion test - a white emulsion is formed when ethanol and water are added to fats.
What are proteins?
They are organic molecules made up of the elements carbon, hydrogen, oxygen and nitrogen.
What is special about proteins?
They are present in all cells and are the largest and most complex food substance.
What are the functions of proteins?
- They are used in the synthesis of new cytoplasm, for growth and repair of worn-out body cells.
- They are used in the synthesis of enzymes and some hormones.
- They are used in the formation of antibodies to combat disease.
How are protein molecules formed?
Many amino acids are joined in a linear manner to form a polypeptide, which then forms protein when polypeptides are linked together.
How do we test for proteins?
Biuret test - the biuret solution will turn violet in the presence of proteins.
How can we find out what nutrients are in our food?
We can carry out food tests.
