Carbohydrates Flashcards
What 3 elements do carbohydrates contain?
Carbon, hydrogen and oxygen
Carbohydrates contain carbon which means they are what type of compound?
Organic compounds
What is a polymer?
A polymer is a long chain of identical monomers.
What reaction joins small molecules together to form 1 large molecule called a polymer?
Polymerisation
What the three forms do carbohydrates exist in?
Monosaccharides,disaccharides and polysaccharides
What molecules make up monosaccharides?
Small reducing sugar molecules.
What are three properties of monosaccharides?
Monomers, sweet to taste and crystalline
What is the general formula of a monosaccharide?
(CH2O) or Cn(H2O)
What is a monosaccharide with three carbons called and what is an example of it?
Triose sugar e.g. glyceralsehyde
What is a monosaccharide called with 5 sugars and what is an example of one?
Pentose sugar e.g. deoxyribose and ribose sugar
What is a monosaccharide with 6 carbons called and what is an example of one?
Hexose e.g. glucose, xylose, fructose and galactose
How many isomers does glucose have?
2
What is an isomer?
Molecules that have the same chemical formula but a different arrangement of atoms.
What are the two types of glucose called?
Alpha and beta glucose
Where is the OH found in alpha glucose?
Below the ring
Where is the OH found in beta glucose?
Above the ring
What are disaccharides?
Two monosaccharide units joined together with a glycosidic bond to form a disaccharide.
When two monosaccharides form a disaccharide what type of reaction is it? What other product is formed?
Condensation reaction so water is also formed
What are three examples of disaccharide sugars?
Maltose, sucrose and lactose
What do two glucose monomers make?
Maltose
What does a glucose and fructose monomer make?
Sucrose
What does a glucose and galactose monomer make?
Lactose
What type of sugars are monosaccharides and what does this mean they can do?
Reducing sugars so they are able to give electrons to other molecules
What 2 disaccharides are reducing sugars?
Maltose and lactose
What type of sugar is sucrose and what does that mean?
Non reducing sugar so will not donate electrons
What does a reducing agent do?
Helps to reduce by giving electrons to oxidise itself
What does an oxidising agent do?
Helps to oxidise by removing electrons to get reduced itself
How do you test for glucose?
Benedict solution and heat
What colour change will you see if glucose is present?
Light blue to brick red
Why does glucose turn the benedicts to brick red?
It is a reducing sugar so it donates an electron so reduces it from copper 2+ to copper+
If the reducing sugar test is negative what test do you do after on the sugar?
Non reducing sugar test
What happens in the non reducing sugar test if a non reducing sugar is present?
Light blue to brick red
What must happen before doing the non reducing sugar test?
Boil with acid to break down the non reducing sugar
Why does the non reducing sugar turn the blue solution to brick red?
Once boiled the non reducing sugar is broken down into a reducing sugar whoch donates its electrons so the Cu2+ gets reduced to Cu+
What are polysaccharides?
Polymers formed by combining together many monosaccharide molecules
How are monosaccharides joined and how were the bonds formed?
Joined by glycosidic bonds that were formed by condensation reactions
Why are they suitable for storage?
They are large, insoluble molecules
When hydrolysed what do polysaccharides break down into?
Disaccharides and polysaccharides
Where is starch found?
In plants in the form of small granules or grains large amounts occur in seeds and storage organs such as potato tubers
How is starch formed?
Joining of 200-100000 alpha glucose molecules by glycosidic bonds in a series of condensation reactions
What is the structure of starch?
Chains can be branched or unbranched the unbranched chain is wound into a tight coil making the molecule very compact
What is the main role of starch?
Energy storage
How is starch’s structure suitable for energy storage? (5)
- Insoluble so doesn’t affect water potential so water isn’t drawn into cells by osmosis
- Large and insoluble so doesn’t diffuse out of cells
- Compact so lots can be stored in a small space
- When hydrolysed it forms alpha glucose which is easily transported and ready to use in respiration
- Branched from means it has many ends so enzymes can act on glucose molecules simultaneously so glucose monomers are released very rapidly
How do you test for starch?
Add two drops of a sample onto a spotting tile or 2 cm cubed into a test tube add two drops of iodine solution and shake or stir
What colour does the iodine turn if starch is present?
Blue- black
Where is glycogen found?
Found in animal and bacteria
What is glycogen made up of?
Alpha glucose
What is the structure of glycogen like?
Shorter chains and a more highly branched structure than starch
Where is glycogen found?
Stored as small granules mainly in muscles and the liver
Why is glycogen’s structure suitable for storage?
- Insoluble doesn’t tend to draw water into the cells by osmosis
- Insoluble doesn’t diffuse out of cells
- Compact lots of it can be stored in a small space
- More highly branched so has more ends which can be acted on simultaneously by enzymes so more rapidly broken down to form glucose monomers used in respiration. This is important because animals have a high metabolic rate and are more active than plants so need more energy.
How is cellulose different to starch and glycogen?
Made up of beta glucose
What is the structure of cellulose?
Straight unbranched chains that run parallel to eachother allowing hydrogen bonds to form cross linkages between adjacent chains
How is cellulose a valuable structural material?
Hydrogen bonds are in large numbers so strengthen it massively
What happens when cellulose molecules are grouped?
They form microfibrils which are arranged in parallel groups called fibres
What does cellulose do in plants?
Major component of the plant cell wall and provides rigidity to the plant cell
What does the cellulose cell wall do?
Prevents the cell wall from bursting as water enters by osmosis it does this by exerting an inward pressure that stops any influx of water so plant cells are turgid and push against each-other making the plant rigid
