Carbohydrates Flashcards
What elements make up carbohydrates
Carbon, hydrogen and oxygen
Examples of disaccharides
Maltose, lactose, sucrose
What is an isomer
Same molecular formula, different arrangement of atoms
Isomers of glucose and the structural difference
Alpha and beta
The hydroxyl group is below for a and above b
What is the test for reducing sugars
Benedict’s test: add 2cm3 of sample with equal volume of Benedict’s reagent (copper sulfate) and heat between 70 and 90 for 5 minutes. Goes from blue to brick red (copper oxide) if reducing sugar is present
What colour does benedicts reagent go when reducing sugars are present and why
From blue to red as they contain a group that reduces the cu 2+ ions to cu+ when heated in an alkaline solution
All monosaccharides are reducing sugars, true or false
True
How is a glycosidic bond formed in disaccharides
Water taken away to form oxygen bridge known as a 1-4 glycosidic bond
Test for non reducing sugar and why
Boil 2cm3 of sample with 2cm3 dilute hydrochloric acid for 5 mins to hydrolyse disaccharides into monosaccharides
Then neutralise with sodium hydrogen carbonate ( benedicts doesn’t work in acidic)
Then do normal Benedicts test if red it was non reducing
What is the test for starch
Add iodine in potassium iodide, if changed to blue black then starch is present
Detail the formation of starch
Polysaccharide mainoy of the polysaccharide amylose. Condensation between many alpha glucose. Monomers, water released to from 1-4 glycosidic bonds. Chains can be branched or unbranched and unbranched is wound into a tight coil. Amylose is tightly coiled/compact insoluble polysaccharide and amylopectin is a branched polysaccharide.
Why is starch suited to its function
-Helicle shape of coiled starch makes for a compact polysaccharide (fits many subunits/lots of energy into small space) and coiled by hydrogen bonds in the chain
- insoluble so water isn’t drawn into cells by osmosis/ W.p not affected
-Large so doesn’t diffuse out of cells
-When hydrolysed forms a glucose for respiration to make ATP
It is a storage polysaccharide for energy
In what organisms is glycogen found
Animals and bacteria
What’s the structure of glycogen
Short chains and highly branched, made of alpha glucose
Where is glycogen found
Granules in muscles and the liver
How is glycogens structure suited for its function
-function in carb storage
insoluble so doesn’t draw water into cells
-insoluble so can’t diffuse out of cells
-Compact (much in small space)
-Highly branched so enzymes can break down ends into monomers fro respiration
Detail the formation of cellulose
Polymer of B glucose, condensation reaction between monomers forming 1-4 glycosidic bonds, every second B glucose rotates 180, forms straight unbranched chains that run parallel with hydrogen bonds to from micro fibrils. Many microfibrils combine to form macro fibres which combine to cellusolose
Where is cellulose found
Cell walls
How are hydrogen bonds made in cellulose
Adjacent molecules are rotated 180 which allow H bonds between OH groups
How is the structure of cellulose suited to its function
-many hydrogen bonds add strength
- long unbranched chains made of b glucose
- fibres and micrfibrils add strength
It is a fibrous polysaccharide that is tensile and can withstand osmotic forces when cells absorb water by zo and become turgid, spaced allow material to pass through freely to the CSM/provides rigidity to cell wall and stops cells bursting by exerting inward pressure (cells turgid to max SA for photosynthesis)
List some common monosaccharides
Glucose( hexose C6H12O6), galactose and fructose
What is maltose
A disaccharide formed from the condensation of two glucose molecules
What is sucrose
A disaccharide formed by the condensation of one glucose and one fructose
What is lactose
A disaccharide formed by the condensation of a glucose and a galactose
What bond joins monosaccharides
Glycosidic (mainly 1-4)
Draw out alpha and beta glucose
Do it
