U4AOS2 - Metabolism of food in the human body Flashcards
Structure of Enzymes (inc. how specific they are)
Made up of Proteins
Contain an active site - where the substrate (reactant(s) of a reaction) can bond.
Molecules that the active site will accept are very specific - therefore, enzymes will often only catalyze one or a very small number of reactions (this is unlike inorganic catalysts - which are generally not specific)
Enzyme-Substrate Complex
Purpose of Enzymes (inc. how they accomplish it)
To act as biological catalysts, and to increase the rate of reaction in the body
They accomplish it by providing alternate reaction pathways with a lower activation energy
- this means a greater proportion of molecules will have enough KE to breach the activation energy
- speeds the reaction up
Do enzymes change the amount of product produced?
No - they only increase the rate of reaction
3x Main Points for Enzyme Function
- Specific Active Site for a Specific Substrate
- Interactions weaken the intermolecular bonds of the products, lowering activation energy
- this allows the reaction to occur - forming the products
Are enzymes modified over the course of a catalyzation
No - the enzyme remains unchanged at the end of the reaction (regardless if lock-and-key, induced fit, coenzymes)
Effect of optical isomers on enzymes
Enzymes typically will not accept optical isomers - generally two separate enzymes will be required
Enzyme Lock-and-Key Model
States that only substrates that perfectly fit the active site can bond
(like a lock and key)
Enzyme Induced Fit Model
Suggests that the active site of an enzyme is more flexible
Suggests that the shape of the active site may change shape slightly to fit the substrate
however - at the end of the reaction - the substrate will return to its original position
Why do enzymes experience denaturation?
Because, enzymes themselves, are proteins
Effect of Temperature on Enzymes (inc. high/low/optimal temp)
If temp is lowered - rate of reaction will be too slow
If temp is raised - the protein will begin to denature (as a result of more vibration)
This results in optimum temperatures - where the rate of reaction is highest, without any breakdown in the structure of the protein (generally body temp for humans)
Effect of pH on Enzymes
Changing pH will modify the structure of the enzyme (same with proteins in acids or bases).
Given that enzymes and substrates can bond ionic-ly, if the pH becomes acidic or basic, the enzyme may be unable to bond to substrates
Hydrolysis of Proteins (inc. process and purpose)
Process of chemically digesting proteins
Amide Links (peptide links) will be broken, splitting the protein into amino acids (and consuming water).
(PRIMARY STRUCTURE)
Purpose: to allow the amino acids, which are polar, to travel through the bloodstream, where they can be assembled into a new protein at the required location
Enzyme that catalyzes the hydrolysis of proteins
Protease - type of enzyme that will help to break down proteins
A common one is pepsin
Effect of adding HCl (in the presence of pepsin) to Proteins (and sometimes heating)
Results in the hydrolysis of the protein
- the HCl is the source of H+,
- the enzyme catalyses the reaction
- the heat can increase the rate of reaction
heat and change in pH are the two main reasons for denaturation
Denaturation
disruption or destruction of the secondary, tertiary, (and quaternary only if it’s present)
results in the unfolding of the protein, disrupts the 3D shape, and disables the functionality of a protein
Denaturation vs Hydrolysis of Proteins
Denaturation disrupts secondary, tertiary (and quanternary structures - if present)
VS
Hydrolysis which only disrupts the primary structures
Heat as a cause of denaturation (inc. reversibility)
heat -> increases kinetic energy of molecules
if the kinetic energy is high enough -> the molecules can vibrate so rapidly that the secondary and above bonds can be disrupted
if the heat is raised high enough - this is not reversible
Real life example of heat based denaturation
heating medical supplies to denature the proteins in bacteria - as denatured proteins have less biological activity - and so are no longer harmful
pH as a cause of denaturation (inc. reversibility)
when pH changes, the ionic interactions change (as the acid/base properties change)
if the pH deviates too far from its optimum pH, the denaturation may be irreversible
Real life example of pH based denaturation
Vinegar is often used when boiling an egg, as it’s an acid
this lowers the pH of the solution, denaturing the eggs proteins
Step 1 of Hydrolysis of Starch
Occurs in the mouth, starch (either amylose or amylopectin) is hydrolyzed by saliva in the mouth, which contains the enzyme amylase
This converts starch into maltose (a disaccharide)
Step 2 of Hydrolysis of Starch
The maltose is then hydrolyzed into glucose, with maltase as the enzyme
Why can amylase operate in the mouth, but not the stomach?
The optimum pH of Amylase is 6, but the pH in the stomach is about 1.5
so the amylase enzyme undergoes denaturation
Enzyme required to hydrolyze sucrose
Sucrase
Enzyme required to hydrolyze lactose
Lactase
Hydrolysis of Cellulose
Celluose is constructed from β-glucose (as opposed to the other forms using α-glucose)
This means it requires cellulase (as opposed to amylase), which the body doesn’t produce
Therefore - humans cannot hydrolyze cellulose - its however, still helpful as fibre, just not as a source of energy
Differentiation ability of humans to hydrolyze lactose (inc symptoms for those who cant)
Lactose requires the enzyme lactase to hydrolyze
However - a significant portion of the population is lactose intolerant, meaning that they do not produce the required enzyme, lactase.
People often report stomach aches or vomiting as symptoms
Glycemic Index (inc glucose as a reference)
indicates how quickly carbohydrates (only starch in VCE) impact glucose level
GI of glucose is assigned 100, everything else is a comparison to glucose, therefore, no units
High GI - causes a quick spike in blood sugar, but decreases quickly
Low GI - causes a gradual increase in blood sugar
Does the GI index measure energy density
No - GI values are not a measure of energy density - only a measure of the ease to hydrolyze carbohydrates - the energy density depends on the food
GI of Amylose
Low GI
- has no branching, therefore, stronger intermolecular bonds
- less surface area for water and enzymes to act on
- glucose will be produced slower -> low GI
GI of Amylopectin
Low GI
- has branching, therefore, weaker intermolecular bonds
- greater surface area for water and enzymes to act on
- glucose will be produced faster -> high GI
GI of Cellulose
GI of 0
Cannot be hydrolyzed by humans - no effect on glucose production
Bile - tool for emulsifying triglycerides (inc. what it creates)
Type of salt, produced in the liver
Given its an emulsifier - it will break down large clumps of triglycerides into smaller chunks
Then - a hydrophobic end of the bile will dissolve in the fat, and a hydrophilic end will dissolve in water
Creating: miscelles droplets - which can be hydrolyzed
Why do triglycerides need to be emulsified
Because they are non-polar molecules, and insoluble in water
emulsification makes them polar in water, allowing them to be hydrolyzed
Hydrolysis of Triglycerides (inc. requirement)
Required to be emulsified
The emulsified triglyceride then undergoes hydrolyzed, catalyzed by lipase
This separates the glycerol backbone and the 3 fatty acids (creating 3 water)
Transporting Glycerol/3xfatty acids (after the hydrolysis)
They are transported to be reformed into lipids (in adipose tissues)
Adipose Tissues (inc. purpose)
Tissues found under the skin and around muscles
Purpose: long term energy storage, excess triglycerides are stored in these molecules
Consumption of Fatty Acids
When fatty acids are required - they will be transported to muscle cells, and undergo oxidation
(producing CO2 and H2O)
Oxidative Randicity (inc. targeted bonds, way to tell)
Deterioration of lipids through atmospheric oxygen
Targeted bonds: generally only C=C bonds, however, sometimes C-C bonds will be targeted (much slower tho)
Way to tell: They will smell badly, and go off
Factors that effect the speed of Oxidative Randicity (3)
- presence of C=C increases the speed
- number of C=C bonds (more = faster)
- lowering temperature - reduces the rate of reaction - lowering oxidative randicity
Preventing Oxidative Randicity (without antioxidants)
Remove the presence of sunlight and oxygen
Autooxidation (inc. free radicals)
Spontaneous oxidation of a compound in the presence of oxygen
caused by free radicals (molecules or atoms with unpaired electrons), which are highly unstable
Antioxidants
Reducing agents, which are oxidized in preference to the triglyceride
They slow down oxidative rancidity
Coenzymes (inc. what they are derived from, and purpose)
Small, non-protein, organic molecules that bind to the active site of an enzyme
Often derived (not always) from vitamins
Purpose: They modify the binding properties of the active site of the enzyme, to suit the shape of the substrate.
then they can act as a a carrier of electrons and/or groups of atoms
Are Coenzymes altered as a result of a reaction
Sometimes, however - they are regenerated in future reactions
