Biology - Biological Molecules Flashcards
What are the three major types of biological molecules found in living organisms?
Carbohydrates, lipids, proteins.
What are carbohydrates and what are they made of?
They are organic molecules made up of elements carbon, hydrogen and oxygen. Hydrogen : Oxygen = 2:1
Classes of carbohydrates
- Single sugars/Monosaccharides (glucose - plants and animals, fructose - plants, rarely animals, galactose, ribose)
- Double sugars/Disaccharides (maltose, sucrose, lactose)
Sugars are sweet and soluble in water and provides energy to do work. - Complex carbohydrates/Polysaccharides (starch, glycogen, cellulose)
Not sweet and insoluble in water.
What are organic compounds?
Organic compounds refer to carbon-containing compounds that are found in living organisms. These compounds contain both hydrogen and oxygen.
What are macromolecules?
- All organic compounds are macromolecules
- Large molecules composed of thousands of covalently bonded atoms
- Some are polymers built from repeating units called monomers
How are the saccharides related?
Monosaccharides are linked together by condensation reaction to form disaccharides and polysaccharides.
What is condensation reaction?
Links stuff. A condensation reaction (a chemical reaction) where two molecules are joined together to form a large molecule usually with the removal of one water molecule.
E.g. glucose + glucose –> maltose + water (the link between the two maltose thingies is the glycosidic bond)
What is hydrolysis?
Opposite of condensation reaction, breaks stuff down. A reaction in which a water molecule is needed to break a complex molecule into simpler substances. E.g. disaccharide into its monosaccharide units
What are polysaccharides?
- Complex carbohydrates aka polysaccharides
- Made of many monosaccharides linked together through condensation reaction
- May occur as long, straight or branched cells
- Some are polymers of monosaccharides
What is maltose and sucrose, and how can they be broken down?
Maltose occurs in germinating grains, and one molecule consists of two glucose molecules bonded together. glucose + glucose –> maltose
A sucrose molecule is made up of one glucose and fructose molecule joined together. glucose + fructose –> sucrose
A double sugar can be split into two single sugars by enzymes. e.g. maltose (with enzyme maltase) –> glucose + glucose
What are reducing sugars and how to test for them?
Glucose, fructose and maltose are reducing sugars. Reducing sugars produce a red precipitate when tested with the same amount of Benedict’s solution, which is mixed in a test tube and placed in a boiling water-bath.
What are complex carbohydrates?
- Made up of many similar molecules of single sugars joined together to form a large molecule
- Starch, glycogen and cellulose are made of of numerous glucose molecules. The glucose molecules are linked in different ways (different structures, chemical, biological properties)
What are the characteristics of starch?
- Made up of thousands of glucose molecules joined together
- Storage form of carbohydrates in plants
- When needed, can be digested to glucose to provide energy for cell activities
- Found in storage organs in plants
- Broken down into maltose (disac) by enzyme amylase, and maltose into glucose by enzyme maltase (monomer)
What are the characteristics of cellulose?
- Many glucose molecules joined together
- Bonds between glucose units different from starch
- Cellulose cell wall protects plant cells from bursting/damage.
- Cannot be digested.
- Serve as dietary fibre –> prevents constipation
What are the characteristics of glycogen?
- Branched molecule, many glucose molecules joined together
- Storage form of carbs in mammals. When needed, it is digested to glucose to provide energy for cell activities.
- In animals, stored mainly in the liver and muscles
What are the functions of carbohydrates?
- substrate for respiration to provide energy for cell activities
- form supporting structures e.g. cell walls
- formation of nucleic acids, e.g. DNA
- synthesise lubricants (mucus)
- synthesise nectar in flowers
What are fats?
- Type of lipid
- Organic molecules made up of carbon, hydrogen, oxygen (much less oxygen)
- Fats occur as solid in room temp, oils occur as liquid in room temp
What are triglycerides?
- Major group of lipids
- Also known as fats
- Made of two compounds; 3 fatty acid molecules + 1 glycerol molecule –? linkage between the glycerol and the fatty acids is the Ester linkage
- All triglycerides are macromolecules, but they are NOT polymers.
e.g. tristearin needs to be broken down into glycerol + 3 stearic acid molecules by the enzyme lipase
Structure of fatty acids and what happens when saturated vs unsaturated?
Organic molecule, has a carboxyl group (- COOH).
When saturated, the fatty acid chain is straight.
When unsaturated, the chain has kinks where double bond occurs.
Function and structure of glycerol
Glycerol is the alcohol that usually makes up triglyceride.
Has 3 carbons (in the middle)
Each carbon bears a hydroxyl group (- OH)
What are the functions of fats?
- Source and long-term source of energy (higher energy value than carbs)
- Insulating material; prevents excessive heat loss
- Reduce water loss from skin surface; glands secrete oily substance
How can we test for fats?
Ethanol emulsion test –> test for presence of fats
White emulsion formed when ethanol and water are added to fats
emulsion = suspension of small drops of liquid into another liquid
add ethanol –> shake –> add water –> shake
What are proteins?
Organic materials made up of carbon, hydrogen, oxygen, nitrogen. Sulfur may be present. Proteins are always present in all cells.
What is the structure of proteins?
- Built up from amino acids
- An amino acid is made up of an amino group (–NH2), acidic/carboxyl group (-COOH) and a side chain (R)
