▪️🔹1.1 Carbohydrates -chemical elements Flashcards
What type of compounds are carbohydrates?
Organic compounds
What elements do carbohydrates contain?
Carbon, hydrogen and oxygen
What is the basic unit of a carbohydrate?
A monosaccharide
What do two monosaccharides combine to form?
A disaccharide
What do many monosaccharide molecules combine to form?
A polysaccharide
What are monosaccharides?
Small organic molecules that are the building blocks for larger carbohydrates
What is the general formula of monosaccharides?
Cn(H2O)n
Name the value (n) of carbon atoms in triose and hexose
Triose= 3 carbon atoms Hexose= 6
Give an example of a hexose carbohydrate?
Glucose is a hexose sugar
How many isomers does glucose have an what are these?
How do these differ?
2 isomers
a- glucose and B- glucose
They are based on the different positions of an (OH) and (H) in the structure of the molecule
What does the different forms of glucose result in?
The biological differences of polymers such as starch and glucose
Define monosaccharide
An individual sugar molecule
Name 4 functions of monosaccharides
1) source of energy in respiration
2) building blocks for larger molecules e.g glucose makes polysaccharides starch, glycogen and cellulose
3) parts of nucleotides (D in DNA, R in RNA)
4) intermediates in reactions (triose are intermediates in reactions of respiration and photosynthesis)
How are disaccharides formed?
Composed of 2 monosaccharides bonded together with the formation of a glycosidic bond and the elimination of water (condensation reaction)
Name the monomers present in, and biological role of maltose
Glucose + Glucose
Needed for germinating seeds
Name the monomers present in, and biological role of sucrose
Glucose + fructose
Needed for transport in the phloem of flowering plants
Name the monomers present in, and biological role of lactose
Glucose + galactose
Found in mammalian milk
Which test tests for reducing sugars?
Name the positive result
Benedicts test
Blue - green -orange —> brick red
Why do non-reducing sugars not change during a normal Benedicts test?
Because the disaccharide is not broken down to its monosaccharides, this is done by heating with hydrochloric acid and then adding alkali, positive result should now occur
Name an enzyme that can detect sucrose by hydrolysing it into glucose and fructose
Name a negative of this
Sucrase
It is specific, only hydrolyses sucrose no other non reducing sugars
How can you get a quantitative measurement of the concentration of sugar
Using a biosensor, provides an accurate measurement, used in conditions such as diabetes
Define a polymer
A large complex polymer formed from large values of monosaccharides linked by glycosidic bonds
Why is starch (a polysaccharide) a better storage product in the body than glucose (reasons why we convert starch to glucose)
1) starch is insoluble so has no osmotic effect
2) you can’t diffuse out of a starch cell
3) starch is a compact molecule and can be stored in a small space
4) starch carries a lot of energy in its C-H and C-C bonds
What is starch made out of?
A-glucose molecules bonded in two different ways forming amylose and amylopectin
Describe amylose
1)linear unbranched molecule with a-1-4 glycosidic bonds between (C1) and (C4) in the next.
2)repeated, forming a chain which could into a helix
(Need to know how it’s drawn)
Describe amylopectin
-chains of glucose monomers joined with a-1-4 glycosidic bonds
-these are cross linked within a-1,6-glycosidic bonds.
(Need to know how it’s drawn)
Describe a test to identify starch
The iodine, potassium iodide test
Colour change = orange/brown —> blue/black
Qualitative test not quantitive
What is glycogen used for?
The main storage product in animals
Describe the structure of glycogen
Similar to amylopectin it has a-1,4 and a-1,6 bonds but glycogen molecules have shorter a-1,4 linked chains so are more branched than amylopectin
(Learn diagram)
What is the purpose of cellulose
Structural polysaccharide found in plant cell walls
- Describe the structure of the polysaccharide cellulose?
- What rotates the glucose molecules by 180 degrees
Has many long parallel chains of B-glucose
Glucose monomers are joined by B-1,4 glycosidic bonds
-the B- link rotates the adjacent molecules by 180 degrees which allow hydrogen bonds to form between the OH groups of adjacent parallel chains creating stability
Describe the different layers inside cellulose
1) 60-70 cellulose molecules are tightly corsslinked to form microfibrils
2) micofibrils are held in bundles called fibres
3) cell wall has many givers that run parallel within a layer but at an angle to adjacent layers
4) laminated structure contributes to cell walls strength
Explain how cellulose fibres are permeable
Because of the spaces between the fibres, this allows water and it’s solutes to penetrate through the spaces in the cell wall to access the cell membrane
Where is chitin (structural polysaccharide) found?
In the exoskeleton if insects and in fungal cell walls
Describe the structure of chitin
Has long chains of B-1,4 linked monomers with groups derived from amino acids added to form a hetropolysaccharide
-monomers are rotated through 180 degrees and chains are cross linked by hydrogen bonds, forming microfibrils
