Lec 5: Molecules, energy and biosynthesis Flashcards
Types of biological molecules
- Lipids
- Carbohydrates
- Proteins
- Nucleic acids
diverse group of water insoluble biological molecules
Lipids
energy stores
fats
major components of membrane
-phospholipids
-sterols
are called polyhydroxy aldehydes and ketones
Carbohydrates
general formula for carbohydrates
(CH2O)n
most complex and most abundant organic molecules
Proteins
What does proteins contains
- atleast one carboxyl
- one amino group
contents of nucelic acid
- 5 carbon sugar
- phosphate grouo
- nitrogenous base
Main classes of Nucleic acids
- DNA (deoxyribonucleic acid)
- RNA (ribonucleic acid)
carries coded information, arranged into genes
DNA
instrumental in translating the coded message of DNA into amino acid
RNA
The process of increasing the rate of reaction with the use of a catalyst
Catalysis
any substance that increases rate of reaction
catalyst
Catalyst of biochemical reactions
Enzymes
How does enzyme increase reaction rate
by means of lowering the energy of activation
reactions catalyzed by enzymes are usually
____ to ___times faster than uncatalyzed reactions.
10^3 to 10^17
The kinetic energy required to bring the reactants into position to interact
Activation energy/free energy of activation
molecule form when enzyme binds with substrate
Enzyme-sustrate complex
each enzyme is specific for a certain substrate
Enzyme specificity
The enzyme will act on a particular steric or optical isomer
Stereospecificity
The enzyme will act on a particular type of chemical bond
Bond specificty
highly specific nature of most enzymes arises from the close and complementary fit between enzymes and substrate in a special portion of the enzyme surface
Active site
Two models for enzyme action
- Lock-and-key model
- Induced fit model
that the active site of an enzyme will undergo a conformational change when binding a substrate, to improve the fit
Induced fit model
The active site of an enzyme is structured to fit a specifically shaped substrate
lock-and-key model
Mechanism of catalysis by enzymes
- Enzyme activity
- Turnover number
catalytic potency of an enzyme
Enzyme activity
number of reactions catalyzed per second by the enzyme
Turnover number
Substrate interacts with the active site of the enzyme, forming an enzyme-substrate complex
Enzymatic reaction
How does enzyme accelerate reactions?
- holds substrates in close proximity to one another
- form an unstable intermediate
- presence of proton donors and acceptors
Factors affecting enzyme activity
- Temperature
- Reaction rates
small organic molecules that act as cofactors
Coenzymes
enzyme minus its cofactor; cannot function without its cofactor/coenzyme
Apoenzymes
whole enzyme
Haloenzyme
Classification of enzyme
- Oxidoreductase
- Transferase
- Hydrolase
- Lyase
- Isomerase
- Ligase
Oxidation-reduction reactions
Oxidoreductase
Group transfer
Transferase
Hydrolysis reactions
Hydrolase
Addition or removal of groups to form double bonds
Lyase
Isomerization (intramolecular group transfer)
Isomerase
Ligation of two substrate at the expense of ATP hydrolysis
Ligase
Example of oxidoreductase
Lactate dehydrogenase
Example of transferase
Nucleoside monophosphate kinase
Example of Hydrolase
Chymotrypsin
Example of lyase
Fumarase
Example of Isomerase
Triose phosphate isomerase
Example of Ligase
Aminoacyl-tRNA synthease
The rate at which an enzymatic reaction proceeds depends on;
- concentrations of substrate,
- product
- active enzyme
used in the living cell as a means of controlling enzymatic reaction
Enzyme inhibition
a molecule that binds to an enzyme and blocks its activity
Enzyme inhibitor
Two types of enzyme inihibition
- Competitive inhibition
- Noncompetitive inihibition
substrate molecule is prevented from binding to the active site of an enzyme by a molecule that is very similar in structure to the substrate
competitive inhibition
How to reverse competitive inhibition
increasing substrate concentration
Caused by molecules that bind to a region(s) of the enzyme outside the active site
noncompetitive inhibition
how to reverse noncompetitive inhibition
dilution or removal of inihibitor
Regulation of Metabolic Reactions
- Control of enzyme synthesis
- Control of enzyme activity
enzymes are only synthesized when needed
Control of enzyme synthesis
regulated by modulator molecules
Control of enzyme activity
alters the tertiary structure of the enzyme thus changing the conformation of the active site.
Allosteric site
first enzyme of the sequence that acts as the regulatory enzyme
- limits the rate of accumulation of the product by slowing the entire sequence from the beginning
End-product (feedback) inhibition
several cat-ion cofactors act as allosteric activators for some enzymes
Enzyme activitation
TWO KINDS OF ENERGY-YIELDING Pathways for Animal tissues
- Aerobic metabolism
- Anaerobic metabolism
food molecules are completely oxidized to carbon dioxide and water by molecular oxygen; energy yield is far greater.
Aerobic respiration
food molecules are oxidized incompletely to lactic acid (lactate); absence of oxygen
Anaerobic metabolism
