Biological Molecules Flashcards
What are carbohydrates made of?
Monosaccharides
How do monosaccharides join together?
By a condensation reaction.
Sucrose is made from:
Glucose and fructose
Lactose is made from;
Glucose and galactose
Maltose is made from:
Glucose and glucose
What type of reaction breaks polymers?
Hydrolysis reaction.
State the Benedict’s Test for Sugars:
1) Reducing sugars include all monosaccharides and some disaccharides.
2) Add Benedict’s reagent (blue coloured) to a sample and heat it in a water bath.
3) If the test is positive a coloured solution will form.
The more Reducing it is the more red the precipitate is.
A more accurate way to do this would be to filter the solution and weigh the precipitate.
State the Benedict’s test for non-Reducing sugars:
1) Add dilute HCl to the solution
2) Heat in water bath then add equal volume of Na2CO3
2) Add Benedict’s reagent (blue coloured) to a sample and heat it in a water bath.
3) If the test is positive a coloured solution will form.
The more Reducing it is the more red the precipitate is.
A more accurate way to do this would be to filter the solution and weigh the precipitate
Definition of a polysaccharide:
A carbohydrate (e.g. starch, cellulose, or glycogen) whose molecules consist of a number of sugar molecules bonded together.
What is starch made from?
Alpha glucose.
What are the 2 types of polysaccharides present in starch?
Amylose
Amylopectin
Describe the structure of amylose:
A long, unbranched chain of alpha-glucose. The angles of the glycosidic bonds give it a coiled structure. This makes it compact, and is so good for storage as you can fit more in a small space.
Describe the structure of amylopectin:
A long, branched chain of alpha-glucose. It’s side branches allow the enzymes to easily break down the molecule to get at the glycosidic bonds easily. This means glucose is quickly released.
Suggest a benefit of starch:
Starch is insoluble in water and doesn’t affect water potential so it doesn’t cause water to enter cells by osmosis, which would make them swell. This makes starch a good for storage.
What is glycogen made from?
Alpha-Glucose
Describe the structure of glycogen:
A long, highly branched chain of alpha-glucose. Side branches allow the enzymes that break down the molecule to break the glycosidic bonds quickly.
Lots of branches means energy can be quickly released.
Compact molecule.
What is glycogen the main energy store of?
Animals
What is starch the main energy source of?
Plants
What is cellulose used as?
It is used in plants cell walls.
Describe the iodine test for starch:
Add iodine dissolved in potassium iodide solution to the test sample.
If there is any starch present, the sample changes from a browny-orange colour to a blue-black colour.
What is cellulose made from?
Beta-Glucose
Describe the structure of cellulose and describe why this is:
Cellulose is made of long, unbranded chains of beta-glucose.
When the glucose molecules bind, they form straight cellulose chains.
These chains are linked by H bonds to form strong divers called microfibres. The strong fibres mean cellulose provides structural support for cells.
Maltose is a sugar. Describe how a molecule of maltose is formed:
Two molecules of alpha-glucose are joined by a glycosidic bond. A molecule of water is released/a condensation reaction takes place.
Describe the structure of a triglyceride:
Triglycerides have one molecule of glycerol with 3 fatty acid attached to it.
What are there properties of a triglyceride?
They’re hydrophobic (repel water).
Describe how triglycerides are formed:
A glycerol molecule comes into contact with the fatty acid, an ester bond is formed between the two OH groups on the glycerol and fatty acid forming an ester bond.
A molecule of water is released.
This occurs another 2 times as triglycerides have 3 fatty acid groups.
Define an unsaturated fatty acid:
An unsaturated fatty acid has at least 1 double bond between carbon atoms.
Define a saturated fatty acid:
Saturated fatty acids don’t have any double bonds between their carbons atoms.
Describe the structure of a phospholipid:
There are 2 fatty acids attached to a glycerol molecule and one phosphate molecule attached.
Describe the properties of phospholipids:
They’re hydrophobic (attracts water (the phosphate group)).
They’re hydrophilic (repels water(the fatty acid)).
How does the structure of a triglyceride relate to its function?
Mainly used as energy storage molecules because:
• long hydrocarbon chains of the fatty acid release lots of chemical energy when broken down.
• they’re insoluble and so don’t affect water potential.
Why are triglycerides insoluble?
The triglyceride ms clump together as insoluble droplets in cells because the fatty acid tails are hydrophobic - the tails face inwards, shielding themselves from water.
How does the structure of a phospholipid relate to its function?
Phospholipids make up the bilayer of cells because:
• Their heads are hydrophilic and their tails are hydrophobic, so they form a double layer with their heads facing out towards the water on each side.
• The centre of the bilayer is hydrophobic so water-soluble substances can’t easily pass through it - the membrane acts as a barrier to those substances.
Describe the emulsion test for lipids:
1) shake the substance in a test tube with ethanol until the substance dissolved.
2) pour the solution into water
3) any lipid present will form a milky emulsion. The more lipid the more noticible milky colour.
What type of bond is made from a condensation reaction between a glycerol and a fatty acid molecule?
Ester bond.
