Biological Molecules and enzymes Flashcards
Examples of reducing sugars
All monosaccharides such as glucose fructose and galactose
Lactose and maltose
What is a reducing sugar
Donates electrons to other chemicals
Reducing sugar test and result
Benedict’s test
- add benedict’s reagent to 2cm3 of sample
- heat mixture for two minutes
Positive = orange/green
What are isomers
Glucose has two isomers which have the same molecular formula but different structural formula
Maltose is made up of…
Glucose and glucose
Sucrose is made up of…
Glucose and fructose
Lactose is made up of…
Glucose and galactose
What reaction are disaccharides and polysaccharides formed
Condensation reaction, releases water to form glycosidic bonds between the monosaccharides
What reaction can break the bonds between the monosaccharides
Hydrolysis, uses water to break glycosidic bonds
Name of the bond between monosaccharides
Glycosidic bond
Example of non-reducing sugar
Sucrose
Test for non-reducing sugar and result
Only do if reducing sugar test is negative
- heat sample with acid
- neutralise acid by adding alkali
- add benedict’s reagent
- reheat for two minutes
Positive = orange/ green
What are made from alpha glucose
Glycogen and starch
What are made out of ß glucose
Cellulose
Where is starch found and what is it for
Plants for energy store
Types of starch and their structures
Amylopectin is slightly branched
Amylose is a helix
Why is it good that starch is insoluble
Osmosis is not affected and it can’t diffuse out of cells
What is good about starch
Able to coil up a large amount into a small space in the amyloplasts in the cell
Test for starch and result
Iodine test
-add iodine
Positive = blue/black
Where is glycogen found and what is it used for
Animals (liver and muscles) and bacteria
Used for energy store (can be broken down into glucose for energy)
Structure of glycogen and benefit
other properties and benefits (2)
Highly branched alpha glucose polypeptide
Higher surface area so can be more easily broken down
insoluble - no osmotic effects
compact - can store more energy per unit volume
Where is cellulose found and use
Cell walls of plants
Prevents cells from bursting from turgor pressure
How do ß glucose molecules bond together
Alternate molecules have to rotate to bond to form a straight polymer
bonded by glycosidic bonds
How do the ß glucose chains arrange themselves
Parallel to one another and have strong hydrogen bonds between the chains
Cellulose molecules group to form microfibrils which join into bundles called fibres
Difference between saturated and unsaturated fatty acids
Saturated do not have a double bond in the R group (hydrocarbon chain)
Saturated are bad fats
Uses of lipids (4)
Release energy and water when oxidised (more energy per gram than carbohydrates) C-H bonds
Water proof (eg waxy cuticles)
Insulation underneath skin and myelin sheath around neurones
Protects organs
Test for lipids and results
Emulsion test
- add ethanol
- shake
- add water
- filter
Positive = milky emulsion
Name two groups of lipids
Triglycerides and phospholipids
What is triglyceride made out of
One glycerol and three fatty acids from a condensation reaction
Bonds in lipids
Ester bonds
What do fatty acids end in
COOH
What is a phospholipid made out of
One glycerol, two fatty acids and one phosphate
How are phospholipids arranged
In two parallel layers called a phospholipid bilayer
What are phospholipids used for
Cell membranes
Features of a phospholipid molecule
One end is hydrophilic, the other is hydrophobic
Primary structure of proteins
Amino acids join by peptide bonds during a condensation reaction
DNA determines the sequence of amino acids
What is an amino acid made up of
Anime group (H2N) Variable group (R) Carboxyl group (COOH)
Secondary structure of proteins
Chain of amino acids fold depending on which amino acids are present
Held together by hydrogen bonds
Eg alpha helix or ß pleated sheet
Tertiary structure of proteins
Secondary structure is twisted into a 3D shape called a ß polypeptide
Held by disulphides bridges, ionic bonds and hydrogen bonds
Maintains the shape so protein can do its function
Quaternary structure of proteins
Many ß polypeptides join to form large complex molecules
Joined by hydrogen bonds
Test for proteins
Biuret test
-add NaOH and dilute CuSO4
Positive = pale purple
Structure of cellulose
ß-glucose chains arrange themselves parallel to one another held by strong hydrogen bonds
Functions of proteins (5)
Structural Hormones Antibodies Enzymes Transport
What is an enzyme
Globular proteins lower the activation energy of the reaction it catalysed without being changed chemically themselves and can be reused
What does the primary structure of an enzyme determine
The specific 3D structure
What does the tertiary structure of the active site determine
The properties of the enzyme and it’s ability to combine with complementary substrates
What is the functional part of an enzyme
Active site
Lock and key theory
Enzymes have a rigid structure which substrates fit into
Induced fit theory
Enzymes are flexible and can alter the shape of the active site so substrate can fit due to a change in the environment
Factors affecting enzyme action (6)
Temperature pH Concentration of competitive inhibitors Concentration of non-competitive inhibitors Enzyme concentration Substrate concentration
How does temperature affect enzyme action
Increase in temperature increases KE so frequency of collisions increaSes
After a certain temperature, bonds of the enzymes break causing a change in shape of active site
Active site shape becomes less complementary to the shape of the substrate
Less enzyme-substrate complexes formed
Lose their function and denature
How does pH affect enzyme action
At optimum, ions such as H+ and OH- influence the shape of enzymes by interacting with hydrogen and ionic bonds
Shape becomes more complementary to shape of substrate
Above or below optimum would cause a decrease in rate of reaction
How does concentration of competitive inhibitors affect enzyme action
Have similar shape to substrate so are able to fit into active site
Prevents substrate fitting into enzyme
Fewer enzyme-substrate complexes formed
How does the concentration of non-competitive inhibitors affect enzyme action
Fits into another site of the enzyme which distorts the shape of the active site
Substrate no longer fits into active site
No enzyme-substrate complexes formed
How does enzyme concentration affect enzyme action
Increase in enzyme concentration increases rate of reaction until it is no longer the limiting factor
More enzymes per unit volume so higher frequency of collisions
How does substrate concentration affect enzyme action
Increase in substrate concentration increases rate of reaction until it is no longer the limiting factor
More substrate per unit volume to collide with enzymes so more product formed
Reason for adding a buffer solution
Controls the pH for optimum reaction
A change in pH would cause the rate of reaction to slow down and denature enzymes
Hydroxylating
Addition of hydroxyl group
what are carbohydrates used for
provides/ stores energy
what elements are carbohydrates made up of
C H O
how does alpha and ß glucose differ from one another
ß-glucose has the OH and H inverted on the right so every alternate molecule would need to rotate to bond with each other
how do triglycerides form
condensation reaction forms 3 ester bonds and 2 waters are lost
how can the induced fit theory be proven
non-competitive inhibitors are able to alter shape of enzymes so prove they are flexible
