Biological Molecules and Digestion Flashcards
Molecule
Two or more atoms held together by chemical bonds
Biological Molecule
A molecule that is produced inside a living organism
4 main biological molecules
- Proteins
- Lipids
- Carbohydrates
- Nucleic Acids
Proteins Examples
- Form cell structures
- Used for growth and repair
- Enzymes (catalysts)
- Haemoglobin (binds to oxygen)
- Collagen (provides structural support)
Lipids Examples
- Triglycerides (Energy store)
- Phospholipids (forms a phospholipid bilayer used to form membranes in and around cells)
- Cholesterol
- Also used as certain hormones
Carbohydrates Examples
- Starch (Energy store that breaks down into glucose and is used for respiration, found in plants)
- Glycogen (Energy store that breaks down into glucose and is used for respiration)
- Cellulose (structural molecule used to strengthen cell walls)
Nucleic Acids Examples
- DNA
- RNA
- Used to produce and transfer genetic material
Polarisation
- When atoms covalently bond, the electrons shared aren’t evenly distributed
- One region is more negatively charged
- This uneven distribution means the molecule is polarised
Hydrogen Bonding
- When atoms covalently bond, the electrons shared aren’t evenly distributed
- One region is more negatively charged this uneven distribution is polarised
- These polar molecules form hydrogen bonds
Hydrogen Bonding with water
- Uneven distribution of charge between the oxygen atom and the hydrogen atoms as the oxygen atom is bigger
- The hydrogens become more positively charged and the oxygen becomes more negatively charged
- As water is made up of many water molecules, a negative oxygen is weakly attracted to a positively charged hydrogen from another water molecule
Polymerisation
When monomers join together to form a long chain polymer
Macromolecules
Large molecules
Carbohydrates
- Carbon molecules combined with water
- Can be large or small
- Any molecule with carbon is an organic molecule
Monosaccharides
Single sugar molecules
Isomer
- Compounds with the same chemical formula but different arrangements of atoms
- E.g. alpha and beta glucose
Disaccharide
2 monosaccharides joined together by a glycosidic bond formed by a condensation reaction
Polysaccharide
Many monosaccharides joined together by glycosidic bonds joined together in a condensation reaction
3 main monosaccharides
- Glucose
- Fructose
- Galactose
Monomer
A singe unit that forms a chain of polymers when many join together
3 main disaccharides
- Maltose
- Sucrose
- Lactose
How do disaccharides form?
- Monosaccharides join and a molecule of water is removed (condensation reaction)
- A glycosidic bond forms between the 2 monosaccharides
Maltose Formation
Glucose + Glucose –> Maltose + Water
Lactose Formation
Glucose + Galactose –> Lactose + Water
Sucrose Formation
Glucose + Fructose –> Sucrose + Water
Hydrolysis
Addition of water to cause breakdown
Hydrolysis Reactions
- Water is added to a disaccharide to break the glycosidic bond
- The constituent monosaccharides are released
Sucrose Hydrolysis
Sucrose + Water –> Glucose + Fructose
Lactose Hydrolysis
Lactose + Water –> Glucose + Galactose
Maltose Hydrolysis
Maltose + Water –>
2 Glucose
Test for Reducing Sugars
- Heat Benedict’s Solution in a water bath for 5 minutes
- Add the food being tested to the solution
- If reducing sugars are present the the solution should change colour from blue to brick red
Test for Non-Reducing sugars
- Add dilute HCL acid to (sucrose) to hydrolyse it
- Boil the solution and neutralise it with sodium hydrocarbonate
- Repeat the Benedict’s test
Types of Starch
- Amylopectin
- Amylose
Amylopectin
- Branched (branches are longer than glycogen but less)
- Forms 1-4 and1-6 glycosidic bonds
- Highly branched so many enzymes can act on it simultaneously
- Forms alpha glucose when hydrolysed
Amylose
- Unbranched (forms coils which are compact)
- Forms 1-4 glycosidic bonds
- Forms alpha glucose when hydrolysed
- Insoluble in water so it doesn’t impact water potential
- Compact so more of it can be stored in a small space