Chapter 3: Biological Molecules🧬 Flashcards
Water’s role in the body
- Structural: component of cell, lubricant for joints
- Coolant: evaporation
- Reactant: hydrolysis, photosynthesis
- Solvent/ transport: blood, urine
Carbohydrates definition
Organic molecules made up of carbon, hydrogen and oxygen (H and O atoms in the ratio 2:1)
Carbohydrates function
Support: cell wall in plant (cellulose)
Reactants: glucose as substrate for respiration, formation of nucleus acids, to synthesise substances (eg lubricants, nectar)
Converted to other organic compounds (eg amino acids and fats)
Types of carbohydrates
Simple carbohydrates:
1. Monosaccharides (single sugars)- energy source:
- glucose
- fructose
- galactose
2. Disaccharides (double sugars)- transport form:
- maltose
- sucrose
- lactose
Complex carbohydrates:
1. Polysaccharides- storage form:
- Starch
- Cellulose
- Glycogen
Reducing sugars
All monosaccharides and disaccharides, except sucrose, are reducing sugars
Monosaccharides
Sweet and water soluble
Can pass through cell membrane and be absorbed into cell
Molecular formula: C6H12O6
Impt egs:
Glucose: in plants and animals
Fructose: common in plants, rare in animals
Galactose: found in the milk sugar of mammals
Disaccharides
2 monosaccharides bonded chemically
General formula: C12H11O6
Formation: condensation
Break down: hydrolysis
Disaccharides: Forming
Condensation:
2 simple molecules chemically join together to form a larger molecule with the removal of 1 water molecule
glucose + glucose -> maltose + water
glucose + fructose —> sucrose + water
glucose + galactose —> lactose + water
Disaccharides: Break down
Hydrolysis:
Water is used to break down a complex molecule into smaller molecules
(opposite of condensation)
Polysaccharides
Many monosaccharides chemically bonded together
Impt egs: Starch, Cellulose, Glycogen
Polysaccharides Structure
Glycogen: tree-like branches
Cellulose: even rows
Starch: loops or tree-like branches
Polysaccharides Role
Glycogen: main storage of glucose in animals
Cellulose: Structural support for plants and dietary fibres to prevent constipation
Starch: Storage form in plants and digested to glucose for energy
Polysaccharides Occurrence
Glycogen: Stored mainly in liver and muscles of mammals
Cellulose: Cell wall of plants
Starch: Storage organs of plants
Glycogen and starch’s suitability as storage materials
- insoluble in water: does not change water potential in cell
- large molecules: cannot diffuse out of cell
- easily broken down to glucose
- compact
Reducing sugars test
Benedict’s Test:
1. Add 2cm3 of Benedict’s solution to 2cm3 of food sample in a test tube.
2. Shake.
3. Heat contents in a boiling water Barth for 2-3 min.
Observe for colour changes
Starch Test
Iodine Test
- Add 2cm3 of food sample to a test tube.
- Add few drops of iodine solution to test tube.
- Observe for results: Brown to blue-black means starch is present
Fats description
Type of lipid
Organic molecules made up of carbon, hydrogen and oxygen ( no fixed proportion but hydrogen is WAYYY more than oxygen )
Fats use
- Energy storage: long-term as they have higher energy value than carbs
- Insulation (heat and water loss): secretes thin layer of oil that premiers heat and water loss
- Solvent for fat- soluble vitamins and hormones
- Synthesis of cell membrane
Fat molecule and enzyme
Fat molecule —> 1 glycerol molecule + 3 fatty acid molecules
Enzyme: lipase
Saturated vs Unsaturated Fats: Structure
Saturated fats: fatty acid chain is straight
Unsaturated fats: has kinks
Saturated vs Unsaturated Fats: Physical State
Saturated: most are solid at room temperature
Unsaturated: most are liquids at room temperature
Saturated vs Unsaturated Fats: examples
Saturated: butter, cream, cheese
Unsaturated: vegetable oil, nuts
Fats: food test
Ethanol emulsion test
- Add 2cm3 of ethanol to 2cm3 of food sample in a test tube
- Shake contents vigorously
- Add 2-3cm3 of water into test tube. Shake mixture.
Observation: if a white emulsion forms, fats are present
Emulsion
Suspension of drops of one liquid in another liquid
