1. Biological Molecules Flashcards
List 3 common examples of polysaccharides.
Starch
Glycogen
Cellulose
What is the principle role of carbohydrates?
production and storage of energy
What is the general formula of a carbohydrate?
CnH₂On
where n is any number between three and eight.
Number of hydrogen atoms is always twice that of Carbon and Oxygen
What 3 elements do all carbohydrates contain?
Carbon
Oxygen
hydrogen
How is maltose formed?
condensation of two glucose molecules
How is lactose formed?
condensation of a glucose molecule and a galactose molecule
How is sucrose formed?
condensation of a glucose molecule and a fructose molecule
What are monosaccharides?
monomers from which larger carbohydrates are made
List 3 common examples of disaccharides.
lactose
sucrose
maltose
What is the name of a 5c monosaccharide?
Pentose
Can you name 2 common examples of a 5c monosaccharide.
ribose
deoxyribose
What type of sugar is glucose?
Hexose.
what are the 2 types of glucose?
a-glucose
b-glucose
What is a glycosidic bond?
covalent chemical bonds that link carbohydrates to other molecules .
List the 2 most common features of monosaccharides.
sweet tasting
soluble
No.of carbon atoms - name - molecular formula
3 - Triose - C₃H₆O₃
4 - Tetrose - C₄H₈O₄
5 - Pentose - C₅H₁₀O₅
6 - Hexose - C₆H₁₂O₆
7 - Heptose - C₇H₁₄O₇
What is the above table an example of?
Monosaccharides.
What are carbohydrates as a monomer unit?
Monosaccharides
What do pairs of monosaccharides combine to form?
disaccharides
What do monosaccharides form when combined in much larger numbers?
polysaccharides
Glucose + Glucose combine to form?
maltose
glucose + fructose combine to form?
sucrose
glucose + galactose combine to form?
lactose
What are polysaccharides?
polymers, formed by combining together many monosaccharide molecules.
how are monosaccharides joined to create a polysaccharide?
by glycosidic bonds that were formed by condensation reactions
Why are polysaccharides insoluble?
they are very large molecules
What makes polysaccharides suitable for storage?
they are large insoluble molecules
What happens when polysaccharides are hydrolysed?
They break down into disaccharides or monosaccharides
where can starch be found?
give a common example.
many plants in the form of small granules or grains.
e.g chloroplasts
how is starch formed?
The joining of between 200 and 100,000 a-glucose molecules by glycosidic bonds in a series of condensation reactions.
When monosaccharides join what molecule is removed?
What is the reaction therefore called?
Water.
condensation reaction.
What is hydrolysis?
addition of water that causes breakdown.
what happens when water is added to a disaccharide under suitable conditions?
The glycosidic bond is broken which releases the constituent monosaccharides.
How do we test if a disaccharide is a reducing sugar?
Benedicts solution
How do we know if a disaccharide is non-reducing when using Benedicts solution?
the colour of the solution does not change when the benedicts reagent is used
What must be done to a disaccharide in order for it to be detectable as a non-reducing sugar?
must be hydrolysed into its monosaccharide components through hydrolysis.
Name 2 features of ionic bonding.
lose/gain electrons
metal + non-metal
name an example of ionic bonding.
e.g sodium chloride
metal + non metal
name 4 features of covalent bonding.
sharing of electrons.
non-metals
small molecules
giant lattice
list 3 examples of covalent bonding.
oxygen
water
nitrogen
when do hydrogen bonding occur?
between polar molecules
what are monomers?
the building blocks of polymers
list 3 examples of monomers?
amino acids
nucleotides
fatty acids
what are polymers?
a long chain of monomers / repeating units
How are polymers formed from monomers?
through a condensation reaction
sucrose is a disaccharide containing what monomers?
glucose and fructose
What are starch, glycogen and cellulose classed as?
polysaccharides
where and how is glycogen stored?
small granules in the muscles and liver
why does osmosis not occur in starch and glycogen?
because they are insoluble
to whom is glycogen the most important?
animals with a higher metabolic rate
why is the mass of a carbohydrate that is stored relatively small?
because fat is the main storage molecule in animals.
where can glycogen be found?
animal cells and bacteria
what is the importance of glycogen?
major carbohydrate storage product of animals
describe how glycogen is formed.
lots of branched chains of a-glucose
what does having ‘branches’ mean for glycogen?
enzymes can work quickly on the ends of the branches, this hydrolyses glucose molecules that can be used in respiration
what is the main role of glycogen?
energy storage
How is glycogen suitable for its role?
insoluble
compact
highly branched
describe the effects of glycogen being insoluble.
does not draw water into the cell
does not diffuse of the cell
Glycogen is compact, what does this mean?
a lot can be stored in a small place
glycogen is highly branched, how does this help it break down?
being highly branched allows the ends to be worked on by enzymes allowing glycogen to be broken down into glucose monomers
what can groups of microfibrils be arranged to form?
fibres
what is cellulose a major component of ?
plant cell walls
what effect does cellulose have on the cell wall of a plant?
provides rigidity to the cell wall.
stops the cell from bursting
how does cellulose stop the plant cell from bursting?
it stops the cell wall from bursting by exerting an inward pressure that stops any influx of water
how is cellulose made?
monomers of b-glucose
In cellulose are the chains branched or unbranched?
unbranched and straight.
describe the structure of cellulose.
straight unbranched chains run parallel to each other allowing hydrogen bonds to form cross-linkages between adjacent chains.
what effect do the hydrogen bonds have on the cellulose molecule?
each hydrogen bond adds very little strength but the overall number of them makes the molecule very strong.
how are cellulose molecules grouped together?
grouped together to form microfibrils, which in turn are arranged to form fibre groups.
what is the main role of starch?
energy storage
name the five ways in which starch is suitable for its role.
insoluble large molecule compact branched hydrolysed form is an energy source
when hydrolysed what does starch form?
why is this useful?
a-glucose, an energy source for respiration
what effect does starch’s branched form have on its ability to break down?
many ends which can be acted on by enzymes which break down the chain into monosaccharides.
what effect does being insoluble have on starch?
does not draw water into the cell
where can starch be found?
In what form?
many parts of a plant in small grains.
what is the importance of starch?
it forms a major energy source in most diets and is an important component of food.
describe how starch is formed.
chains of a-glucose monosaccharides linked by glycosidic bonds
Are the chains branched or unbranched in starch?
can be both
describe the two chains present in starch.
Amylose - a long unbranched chain of a-glucose with a coiled structure
Amylopectin - long branched chain of a-glucose
How do you test for proteins?
Biuret test
Describe how to perform a biuret test, and what results show a positive outcome
Mix the ground sample to be tested with distilled water.
Add biuret reagent
Positive result for proteins indicated by a purple/violet or blue colour
How do you test for lipids?
emulsion test
describe how to perform a emulsion test, and what results show a positive outcome
mix ground sample to be tested with ethanol.
Add distilled water.
positive result for lipids indicated by a cloudy white emulsion.
How do you test for reducing sugars?
benedicts test
describe how to perform a benedicts test for reducing sugars, and what results show a positive outcome?
Benedcits reagent mixed with sample to be tested.
Heat in a water bath or over a bunsen burner.
Positive result indicated by a change of colour to brick red from blue
describe how to perform a benedicts test for non-reducing sugars, and what results show a positive outcome?
proceed with this test only after a negative benedicts test for reducing sugars
Add dilute hydrochloric acid to sample to be tested.
heat solution to boiling point using a water bath, this is the stage at which acid hydrolysis may occur.
cool the solution under cold water and add sodium hydrocarbonate to make the solution alkaline, as much powder as needed until fizzing stops.
Use universal indicator paper to ensure that the solution is alkaline, else the benedicts reagent will not work
Add benedicts reagent to solution and heat to boiling point.
positive result indicated by a brick red solution
How do you test for starch?
iodine test
describe how to perform a iodine test, and what results show a positive outcome?
combine iodine solution with sample to be tested.
Positive result indicated by a change of colour from orange/yellow to blue/black
