SECTION1 Flashcards
(31 cards)
What are monosaccharides?
- Soluble substances.
- Sweet-tasting.
- Many join to form polysaccharides.
3 examples of monosaccharides.
Glucose, galactose, fructose.
What are disaccharides and how are they formed?
- 2 monosaccharides.
- Formed in condensation reaction.
- Glysocidic bonds.
3 examples of disaccharides and their monosaccharides.
- Maltose - 2 glucose
- Sucrose - glucose and sucrose
- Lactose - glucose and glactose
Monosaccharides and some disaccharides are reducing sugars what is the test for reducing sugars?
BENEDICTS TEST
- Add a liquid form of a sample to a test tube.
- Fill with an equal amount of Benedicts reagent.
- Heat in a water bath.
Positive test=orange-brown.
What is reduction? And what are reducing sugars?
Reduction in the gain of electrons or hydrogen.
Reducing sugars are sugars which can donate (reduce) another chemical.
How are polysaccharides formed?
- From many monosaccharides.
- In condensation reactions.
- Glycosidic bonds
What are polysaccharides?
- Very large molecules.
- Insoluble in water.
- This makes them good for storage.
Some disaccharides are non-reducing sugars, what is the test for non-reducing sugars?
- Add a liquid form of a sample to a test tube.
- Add with equal amount of dilute hydrochloric acid.
- Place in a water bath for 5 minutes - the hydrochloric acid will hydrolyse any disaccharides into monosaccharides.
- Add hydorgencarbonate solution to the test tube to neutralise the hydrochloric acid (test with pH paper
- Re-test with Benedicts reagent, boiling it in a water bath.
Positive test=orange-brown
What is starch and how is it formed?
- A polysaccharide.
- Found in plants.
- Formed by joining 200-100,000 a-glucose monosaccharides in condensation reactions forming glcosidic bonds.
- Major energy source.
- Main role is storage.
- Found in plant cells.
- Never found in animal cells.
What is the test for starch?
- Add 2 drops of iodine to a 2cm^3csample.
- Shake or stir
Positive test=blue-black
Describe the 2 structures of starch.
- Branched or unbranched chains.
* Unbranched wound into helical chains.
How is starch adapted for its function?
- Insoluble- doesn’t affect water potential- water not drawn into cells via osmosis
- Large and insoluble - doesn’t diffuse out of cells
- Compact- can store a lot in a small space.
- When hydrolysed forms a-glucose- easily transported and ready for respiration.
- The branched form has many ends- enzymes can act on each end simultaneously- glucose released rapidly.
Where is glycogen found?
In animal and bacteria cells.
Describe glycogens structure
Like starch but shorter chains and more highly branched.
How is glycogen stored in animals?
- Small granules
* Mostly in muscles and liver
How is glycogen adapted to its function?
- Insoluble- doesn’t affect water potential- water not drawn into cells via osmosis
- Large and insoluble - doesn’t diffuse out of cells
- Compact- can store a lot in a small space.
- Highly branched (more than starch) - enzymes can act on each end simultaneously- glucose monomers released rapidly- ready for respiration.
What is the structure of cellulose?
- Polysaccharide
- Made from B-glucose
- Straight unbranched chains
- Chains run parallel to each other
- Hydrogen bonds form cross-linkages between adjacent chains
- Each hydrogen bond alone is week-together they are strong
Describe the forms of cellulose
- Cellulose molecules grouped together to form microfibrils
* Microfibrils arranged in parallel groups-fibres
What is cellulose used for?
- Major component of cell walls-provides cell rigidity
- Cellulose cell walls prevents bursting from osmosis
- Exerts inwards pressure-stops further influx of water
How is cellulose suited to provide support and rigidity?
- Made up of B-glucose- so form straight, unbranched chains
- Hydrogen bonds between chains add collective strength
- Grouped as microfibrils-grouped as fibres-provides more strength
What characteristics do all lipids share?
- Contain carbon, hydrogen and oxygen
- They are insoluble in water
- Soluble in organic solvents
- Proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
What are the roles of lipids and how do they do those roles?
- Cell membranes - Phospholipids make it more flexible, transfer lipid soluble substances
- Energy source - When oxidised provide over twice the amount of energy as the same mass of carbohydrate, release valuable water
- Waterproofing - Lipids-insoluble in water
- Insulation - slow conductors of heat, act as electrical insulators in myelin sheath around nerve cells
- Protection - stored around delicate organs
How are triglycerides formed?
- 3 fatty acids and glycerol
- Ester bonds
- Condensation reactions
