Cellular respiration, metabolism and enzymes Flashcards
Metabolism:
→ sum of all chemical reactions within a cell
Catabolism:
→ releases energy to breakdown complex molecules
Anabolism:
→ consumes energy to synthesis of complex molecules
Change in free energy (ΔG):
→ difference between free energy of final and initial states
Differences between anabolic reactions and catabolic reactions:
Adenosine triphosphate=
Adenine nitrogenous base + ribose sugars + 3 phosphate groups
Hydrolysis of ATP:
How does ATP function in powering cellular work? (3)
➔ By coupling exergonic with endergonic reactions
Chemical work: Hydrolysis of ATP into ADP is an exergonic reaction as it releases energy. This energy is then used to push endergonic reactions to make complex molecules.
Transport work: Hydrolysis of ATP releases energy which helps pump potassium out of cells and sodium into our cells. Active transport of cells across a membrane.
Mechanical work: Hydrolysis of ATP can allow for energy to be used to contract muscles and do work.
ATP is a renewable resource that can be regenerated by __ ____ to ADP.
+ phosphate
What are enzymes?
→ biological catalyst that speeds up a reaction without being consumed by the reaction.
What are the characteristics of enzymes? (4)
- Enzymes are reaction-specific
- Lock and key complex
- Since enzymes are proteins, can change shape.
- When an enzyme changes shape to better grasp substrate → induced fit
What is activation energy?
The minimum energy required to start reaction/energy required to contort/bend the reactant molecule so that
bonds can break.
How do Enzymes lower Activation energy?
- Enzyme has an active site to which substrate binds → Enzyme-substrate complex
- Active site reshapes to better grasp substrate known as
→ induced fit. Substrates are held together via weak interactions = hydrogen or ionic bonds - Active site can lower Activation energy and speed up
reaction
- Acting as a template for substrate orientation, bringing
substrates together in a way that the new bond is going
to form.
- Stresses the substrate and stabilises the transition state
to speed up the production of products.
- Provides a favourable microenvironment
- Participates directly in the catabolic reaction
BUT: enzyme must return to its original shape in order to
catalyse reaction again, - Substrates are converted to products
- Products are released leaving the active site exposed to more substrates to bind to, further increasing speed of reaction.
Optimal conditions: (2)
- Optimal temperature
- Optimal pH
Cofactor →
→ non-protein helper required to activate enzyme
- Inorganic (___, ___, ___,___)
- Organic = ____ (_____).
- Inorganic (Z, Fe, Cu ions)
- Organic = coenzyme (vitamins)
What is an enzyme inhibitor?
→ selectively inhibits the action of specific enzyme
What are the effects of an enzyme inhibitor? (2)
- Permanent
- Reversible
What is competitive inhibition? (2)
→ competitive inhibitor binds to the active site and takes place of the substrate so that substrate-enzyme binding cannot take place
→ competes with the substrate for the active site
How does an allosteric enzyme oscillate?
The allosteric enzyme oscillates between active (can bind with substrate) and inactive (changed shape therefore cannot bind with substrate) forms.
Cooperativity: (5)
➔ substrate binds to one active site which stabilizes conformational changes in other subunits
➔ Binding of one substrate molecule to one active site locks all subunits in active form to quickly catalyse reaction
➔ E.g., haemoglobin (not an enzyme) – when one Oxygen binds to one active site, haemoglobin becomes more likely to bind 3 more Oxygens
➔ This mechanism amplifies the response of enzymes to substrates: One substrate molecule primes an enzyme to act on additional substrate molecules more readily.
➔ Considered allosteric regulation because even though substrate is binding to an active site, its binding affects catalysis in another active site.
Feedback Inhibition: (2)
- Final product binds to and inactivates the enzyme to prevent excess of product accumulating.
- The product of one enzyme-substrate reaction becomes substrate for next enzyme in metabolic pathway.
Level of energy throughout the process:
Coupling of endergonic and exergonic reactions
- Exergonic reaction is catabolic which breaks down complex molecules into simpler molecules, releasing energy, going from a high energy state to a low energy state
- In the diagram, energy is released in form of e-
- Electron will be picked up via endergonic reaction by NAD+, which becomes reduced (gains 2e-)
- NAD+ picks up 2e- and Hydrogen to become neutral → depleted carrier
- This depleted carrier is reduced, an increase in energy, becoming NADH → energized carrier → stored energy
- NADH drops off e- and is oxidised leading to another set of an endergonic reaction
- Net exergonic ‘downhill’ reaction
- Energy is lost as heat when energy is transferred
- Reaction not efficient
What is the difference the between uncontrolled reaction and cellular respiration? (2)
a) Uncontrolled reaction → if the electrons harvested are directly transferred to water, there will be an explosive release of energy as heat and light ∴ not enough energy for cellular work
b) Cellular respiration → controlled release of energy because electron carrier transports electrons to an electron transport chain which allows for the slow release of ATP energy at each step and eventually, the electrons combine with Oxygen (final e- acceptor) to form water
What steps are involved in cellular respiration? (5)
How does the Regulation of Cellular Respiration take place? (3)
The end products ATP and citrate (from citric acid cycle) inhibit early enzyme (Phosphofructokinase) in glycolysis to prevent production or accumulation or waste of products that are not required.
AMP – adenosine monophosphate (low energy form)
When there is a high accumulation of AMP or ADP, it will stimulate cellular respiration so that more energy can be produced. Stimulates Phosphofructokinase to break glucose molecule.
Versatility of Cellular respiration:
What is biosynthesis? (2)
- Anabolic pathway required to synthesise more complex molecules
- Glycolysis and citric acid cycle function as metabolic interchanges → the intermediates produced as a result of the reactions can further form other complex molecules via an anabolic pathway
