Enzymes and Cell Respiration Flashcards
Enzymes?
A globular protein that increases the rate of biochemical reactions by lowering the activation energy
Metabolism?
Complex network of interdependent and interacting chemical reactions occurring in living organisms
Active site?
Region on the surface of the enzyme to which substrates bind to and start a reaction
Substrates?
Reactant in biochemical reactions
What are the 2 metabolic processes?
Anabolism : synthesis of complex molecules from simpler ones (Input of energy)
Catabolism : breakdown of complex molecules into simpler ones (release energy)
Explain the lock and key hypothesis
Enzymes exhibit specificity to the substrates, substrates fit into the enzyme like a key into a lock
Structural: The 3D structure of the site is specific to the enzyme. If the substrate doesn’t fit, it won’t react
Chemical: Substrates that are not chemically attached to the site won’t react
Why do enzymes exhibit specificity with the substrate?
Due to the matching physical and chemical properties of the enzyme and the active site
Mechanism of enzymes?
Takes place in a watery environment
Enzymes and substrates bump into each other to allow the substrate to bind to the active site
The active site and substrate should collide in the correct orientation and with enough energy to start the reaction
Reaction could be catabolic or anabolic
What is the optimal temperature for enzymes to react?
37° - 38°
When do enzymes denature?
When the temperature is too high, it destroys the quarternary structure of the enzyme
When the pH is too low enzymes won’t be able to react
What is the optimal pH for enzymes?
Depends on the enzyme. Some work best on very acidic environments (the stomach) or on very basic environments (the liver)
What is the relationship between mass and metabolic rate?
Direct relationship.
More mass = higher metabolic rate
Generation of heat by metabolic reactions?
Warm-blooded animals use heat generated by metabolism to maintain a constant body temperature
Heat is the only energy that cannot be used for other reactions
What is enzyme inhibition?
Decreasing or stopping enzyme activity, enzyme production, or any enzyme-related processes
Competitive inhibition?
Competitive inhibitor mimics the shape of the substrate binds to the active site, and competes for the active site.
e.g. Drug methotrexate
Non-competitive inhibition?
Binds to the allosteric site to alter the conformation of the active site shape so the substrate can’t bind to it anymore
End-product inhibition?
When the end product of a pathway is no longer needed and the reaction is stopped at the first step
Mechanism-based inhibition?
Caused by an irreversible bonding of the inhibitor to the active site of a specific enzyme through a covalent bond which causes the enzyme to permanently lose its function
e.g. Penicillin
What is cell respiration?
The gradual and controlled release of energy from organic compounds in cells to form ATP (Adenosine Triphosphate)
What does it mean by respiratory substrates? What are the respiratory substrates used by our body?
Molecules that can be broken down in respiration and release energy
Glucose, Lipids, Proteins (last resort)
How is cell respiration used in our body?
Muscle contraction, Active transportation, Protein synthesis, DNA/RNA replication, Cell signaling, etc.
State the cellular respiration formula
C6H12O6 + 6O2 → 6CO2 + 6H2O
Anaerobic respiration?
Cell respiration that occurs in the absence of oxygen at the cytoplasm.
Only glucose and carbohydrates can be used.
The waste product is lactic acid (lactate)
ATP yield is low
E.g. fermentation, bioethanol
Aerobic respiration?
Cell respiration that occurs in the presence of oxygen at the mitochondria and the cytoplasm
All respiratory substrates can be used
Waste products are carbon dioxide and water
ATP yield is high
E.g. Decomposition of organic matter
Variables affecting cell respiration?
Temperature, pH, oxygen concentration, and substrate concentration
If the temperature is too high, the enzyme will denature, if the temperature is too low, it cannot begin respiration.
What is NAD and what is the role of NAD?
NAD (Nicotinamide Adenine Dinucleotide) is a coenzyme that is the main hydrogen carrier in metabolic reactions. When a NAD loses a hydrogen atom, it becomes reduced NAD or NADH
What is the difference between oxidation and reduction?
Oxidation is where electrons are lost, oxygen is added and hydrogen is lost
Reduction is where electrons are gained, oxygen is removed and hydrogen is added
What are the 5 processes of cell respiration?
Glycolysis
Link reaction
Krebs cycle
Electron transport chain
Chemiosmosis
Glycolysis?
Splitting glucose into pyruvates.
Occurs in the cytoplasm
A hexose sugar is phosphorylated using ATP and then split into two triose phosphates
Oxidation occurs to remove hydrogen and NAD becomes NADH
Two pyruvates are produced and the net yield of two ATP’s
Link reaction?
Pyruvate enters the mitochondrion matrix
Decarboxylation happens when enzymes remove one carbon dioxide and hydrogen from the pyruvate
Hydrogen gets accepted by the NAD to produce NADH
The product is acetyl group that reacts with coenzyme A
Acetyl CoA enters the Krebs cycle
Krebs Cycle?
Acetyl CoA (2C) enters the Krebs cycle and joins a 4C group to form 6C
Oxidative decarboxylation of the 6C sugar to 5C compound produces CO2
Oxidative decarboxylation of the 5C compound to a 4C compound and produce CO2
Two CO2 are produced per molecule of the pyruvate/cycle
Three NADH+ H+ and one FADH2 per molecule of the pyruvate/cycle
One ATP is produced per molecule of pyruvate/cycle
NADH and FADH2 provide electrons for the electron transport chain
Electron Transport Chain?
Occurs in the inner membrane
The electron carriers deposit their electrons and H+ ions
The protons from NADH pass through the first channel and the electrons stay in the inner membrane
Electrons move along the ETC and activate the next channel
H+ from the FADH2 passes through the second channel while electrons stay in the inner membrane
Electrons move along and lose energy while moving
There is now a high concentration of H+ on the other side which helps with chemiosmosis
Chemiosmosis?
The diffusion of ions across a semipermeable membrane through a carrier protein
In this case, the ions are hydrogen protons and the carrier is ATP synthase. The flow of the H+ through the ATP synthase generates ATP
Movement of the H+ drives the rotation of ATP synthase and ATP is made
Chemiosmosis potentially produces 32 ATP molecules, but in most conditions, the yield is slightly lower
Excess H+ and e- are mopped up by using O2 to form water.
