Topic 1 - A Flashcards
What are enzymes?
Large globular proteins which lower the activation energy of the reaction in catalyses.
What are the properties of an enzyme?
They relate to the tertiary structure of it’s active site and it’s ability to combine with complementary substrate to form an enzyme substrate complex.
Why are enzymes soluble in water?
Due to the presence of hydrophyllic side groups on their constituent amino acid.
inside of globular protein - HYDROPHOBIC
outside of globular protein - HYDROPHYLLIC
Why do enzymes have one specific substrate?
Enzymes are proteins which means thy have a sequence of amino acids gives it a specific 3D shape thus creating a specific active site
Explain the induced fit theory?
- the active site is not initially an exact for the substrate
- as the substrate moves into the active site it forces between the two molecules
- this strain distorts a particular bond lowering the activation energy
- now the active site is tightly enveloped to the substrate
- a enzyme substrate complex has now been formed which lowers the activation energy
Describe a co-factor?
A non-protein substance an enzymes requires before it can catalyse a reaction.
Explain the two types of co-factors?
Activators - inorganic groups that are permanently bound to an enzyme, a type of prosthetic group (iron, zinc, copper)
Co-enzymes - organic molecules that temporarily bind to the enzyme, when transferring a chemical group necessary for the reaction.
What makes different orders of amino acids?
The ionic, hydrogen, disulphide bonds are in different places
What bonds form the secondary structure of a polypeptide in amino acids?
Hydrogen bonds allow alpha helix and beta pleated sheets to form.
What is activation energy?
The energy needed to break down bonds.
Example of intracellular reaction?
Synthesis of ATP
Example of extracellular reaction?
Pepsin and amalyse breaking down food particles
What are the six factors which affect enzymes?
- temperature
- pH
- enzyme concentration
- substrate concentration
- concentration of competitive inhibitors
- concentration of non-competitive inhibitors
How do you work out the pH?
-log10(no . of pH)
Explain temperature’s effect on enzymes?
- As the temp. increases so does the rate of reaction
- more kinetic energy so more enzyme substrate complexes are being formed which increases the rate of reaction. - Optimum temperature
- fastest/highest rate of reaction - As temp. increases further the slower the rate of reaction
- 3D structure of enzyme changes as hydrogen bonds are broken and active site changes shape meaning. enzymes denature. Substrate is no longer complementary to active site so you can’t form enzyme substrate complex.
Explain pH’s effect on enzymes?
1 + 3. With the pH when you move away from optimum pH the enzyme denatures
- Ionic bonds break so the active site changes changes shape and it is no longer complementary to the enzyme substrate complex
- Optimum pH
- fastest/highest reaction
Explain the substrate and enzyme concentration effect on enzymes?
Substrate:
- As the substrate conc. increases there is a bigger chance of enzyme substrate complex forming.
- When it plateaus it shows all enzymes in active site are in use.
Enzyme:
- As the enzyme conc. increases there is a bigger chance of enzyme substrate complex forming
- When it plateaus it shows all enzymes are in use
What are enzyme inhibitors?
They slow down the rate of enzyme controlled reaction.
Explain the difference on competitive and non-competitive inhibitors?
Competitive inhibitors have a similar shape to the substrate and for in the active site and this prevents enzyme substrate complex forming whereas non-competitive inhibitors bind onto the allosteric site and causes enzyme and active site to change shape so substrate can’t fit and no enzyme substrate complex is formed.
Describe the process of competitive inhibitors
- the inhibitor has a similar shape to the substrate and so it competes with the substrate for the active site.
- this slows down the rate of enzyme controlled reaction however the vmax is still reached
- if the presence of substrate concentration increases then the degree of inhibition reduces
Describe the process of competitive inhibition?
- the inhibitor binds to the enzyme at the allosteric site and alters the shape of the active site so less enzyme substrate complex form
- this slows down the rate of enzyme controlled reaction however the vmax isn’t reached
- in the presence of a fixed mass of non-competitive inhibitors, increasing the substrate concentration does not reduce the degree of inhibition
- certain non-competitive inhibitors can permanently inactive an enzyme
What is the meaning of metabolic pathway?
A series of reactions in which steps is catalysed by an enzyme.
Describe the process of metabolic pathway regarding inhibitors?
A - B - C - D - E
enzyme 1 enzyme 2 enzyme 3 enzyme 4
The end product of this metabolic pathway is E
E is the non-competitive inhibitor of enzyme 1
As the levels of E build up so does inhibition
As the levels of E fall, inhibition is reduced so more E is formed
What makes up proteins?
- charged amino acids
- covalent bonds
- ionic bonds
- hydrogen bonds
Draw the structure of a protein?
H
H2N - C - COOH
R
to make a dipeptide
Describe the primary structure of proteins?
It is a sequence of amino acids
-limitless possibilities (50-2000)
Describe the secondary structure of proteins?
- Amino acids between carboxyl groups and amino acids form.
- Formation of alpha helix or beta pleated sheets are stabilised through hydrogen bonds (between NH +CO groups)
Describe the tertiary structure of proteins?
Overall 3D shape of polypeptide formed due to interactions between ‘R’ group, amino acids and side chains.
Role of hydrogen and ionic bonds?
- Amino acids coil and more bonds form between different parts of a peptide.
- This results in attraction between positive and negative charges on molecules.
Role of disulfide bridges?
Covalent - form when 2 amino acid cysteine come close together
- extremely strong
- makes protein stable
- difficult to break
Describe the quaternary structure of proteins?
Overall structure for protein molecules including multiple polypeptides and prosthetic groups.
2x alpha peptide
2x beta peptide
Test for Protein
Biuret is added
+ve - turns purple
-ve - stays blue
How does an enzyme relate to it’s tertiary structure?
- the protein binds to the named enzyme active site to form an enzyme substrate complex
- this lowers the activation energy for breaking down the protein by putting stain on peptide bonds making them easier to break
- the tertiary structure is 3D structure of the polypeptide, where hydrogen and ionic bonds are formed, disulfide bridges form when the ‘R’ group of cystenine come close together
- tertiary structure determines shape of active site
- shape makes the enzyme specific to its substrate
State the functions of lipids?
- insulation (keep body at opt. temp.)
- store of energy
- protects organs
- forms myelin sheath around neurons (increases speed)
- water source (respiration)
- used to make and stabilise cell membranes
- lipid derived hormones
What are lipids made of?
- carbon
- hydrogen
- oxygen
How do lipids exist?
- fats
- oils
- waxes
Are lipids good conductors of heat?
No.
Describe structure of tryglycerides?
1 glycerol attached to 3 hydrophobic fatty acid tails
glycerol: H
H - C - OH
H - C - OH
H - C - OH
H
fatty acid: O
(double bond)
OH - C - R
What is eterification?
- condensation reaction between 1 glycerol and 3 fatty acids and water in formed
- ester bond formed
State the difference between a saturated fatty acid and unsaturated fatty acid?
saturated fatty acid: NO carbon double bond
- fats form stronger bonds and have more energy to move as they have straight line
unsaturated fatty acid: HAVE a carbon double bond
- oils aren’t as closely packed (fluid) weaker bonds and less energy due to kinks
What are phospholipids? (5)
- main component of cell membrane
- hydrophillic phosphate head
- two hydrophobic fatty acid tail
- uneven distribution of charges
- gather in a circle when in water
Describe the test for emulsion?
- Add ethanol
- Shake vigorously
- Add water
- +ve - white, milky, cloudy emulsion should form on top
- ve - stays the samr
State what a monosaccharide is and examples?
ONE single unit of sugar e.g. glucose, galactose and fructose
State what a disaccharide is and examples?
TWO sugars bonded together by a glycosidic bond formed by a condensation reaction by hydroxyl group.
Maltose - two alpha glucose molecules
Lactose - galactose and glucose
Sucrose - glucose and fructose (non-reducing)
Draw out an alpha glucose and beta glucose and state the difference?
…
difference is OH group switched
Describe glucose?
- simple sugar
- C6H1206
- 16 kj/g1
What is the most abundant organic polymer?
Cellulose
Why is cellulose strong?
Long, straight beta molecules are joined by beta glycosidic 1-4 bonds. Glucose chains form rope like microfiblis, which are layered networks.
What is starch made of?
Alpha glucose (polysaccharide)
Why is starch coiled and why is this important?
It is tightly bonded due to bonds which are 25% amylose (carbon 1-4 glycosidic bonds) and its helical structure makes it more resistant to digestion.
Why is starch branched?
It contains the water soluble polysaccharide amylopectin (1-4, 1-6)
What are the properties of starch?
compact- can pack alot due to structure
insoluble - won’t affect water potential
large - can’t diffuse through membrane
Describe the biochemical test for starch?
- Add iodine
- +ve - blue-black colour
- ve - brown-orange (no change)
What is glycogen?
Multi-branched polysaccharide of glucose which is an energy store for animals (not plant)
Where is glycogen found and what does it store?
In the liver muscles where it stores carbohydrates.
Describe the structure of amylopectin?
Similar to amylopectin as it has alpha 1-6 glyocosidic bonds that produce an even more branched structure.
Why does glycogen have short chains?
Animals need energy quicker so it is stored as small granules in the liver then broken down quicker than starch as it is insoluble and compact
Describe the biochemical test for reducing sugars?
- Add benedicts solution (blue)
- Heat it in a hot water bath
- +ve - green to brick red precipitate formed (colour depends on concentration of sugar)
Describe the biochemical test for non-reducing sugars?
- Do benedicts test - heat it - no change (blue)
- Add hydrochloric acid
- Boil it in a water bath
- Neutralise acid with sodium hydrogen carbonate
- Add benedicts solution - heat it - green-brick red
Why do you boil the solution when testing for non-reducing sugars?
It beaks the glycosidic bonds between sucrose so they are no longer a reducing sugar but glucose and fructose
