Introduction to Metabolism Flashcards
Define the term : Metabolism
Mechanisms which couple the demand for energy, with the fuel supply
Define the term : Anabolism
SYNTHESIS of new molecules to store energy
Define the term : Catabolism
DEGRADATION of molecules to release energy
Define the term : Oxidation
Gain of oxygen
OR
Loss of hydrogen
OR
Loss of electrons from molecules
Define the term : Reduction
Loss of oxygen
OR
Gain of hydrogen
OR
Addition of electrons
Function of ATP
Adenosine Triphosphate
The essential link between anabolism and catabolism
Energy currency
How many stage of metabolism are there ?
3 stages
Describe what happens in stage 1 of metabolism
Digestion in the GI tract
Absorption and Transport in the blood
Describe what happens in stage 2 of metabolism
In the cell cytoplasm :
- Anabolic
- Catabolic
reactions occur
Where does stage 2 of metabolism occur ?
In the cell cytoplasm
Anabolic
Nutrients built into storage molecules
e.g. glycogen/protein/adipose
Catabolic
Nutrients/ Storage molecules are broken down
e.g. pyruvate / acetyl CoA
Where does stage 3 of metabolism occur ?
In the mitochondria
Describe what happens in stage 3 of metabolism
IN mitochondria :
Catabolism requiring oxygen to completely break down food and generate ATP.
State the 2 nutritional states
Absorptive (fed)
Post-absorptive (fasting)
Energy is stored in the absorptive state and released in the post-absorptive
How do we capture energy release from food ?
The process of cellular respiration (stages 2+3) enables stepwise oxidation of food (e.g. glucose)
Captured as chemical energy, to store in high energy phosphate bonds of ATP.
What is Redox ?
Reduction and Oxidation of molecules
Cellular respiration utilises these reactions to power the synthesis of ATP
State the 2 key coenzymes involves in metabolism
NAD - Nictotinamide adenine dinucleotide
FAD - Flavin adenine dinucleotide
How is NAD produced ?
Vitamin B3 - Niacin
How is FAD produced ?
Vitamin B2 - Riboflavin
State the stages of cellular respiration
Glycolysis
Citric acid cycle / Krebs cycle
Oxidative phosphorylation
Where is energy stored in ATP ?
Energy is stored in phosphate bonds
Energy produced by catabolism is used to drive anabolism and other energy requiring processes.
How much energy is released when ATP is hydrolysed to ADP + Pi ?
-30.5 kJ/mol of energy is released
Describe the stages in cellular respiration
Stage 1 :
Digestion in the GI tract - absorption and transport to cells
Stage 2 : Glycolysis in the cell cytoplasm
Stage 3 : Citric Acid cycle and ox. phos. in mitochondria
… Ultimately yielding ATP
Describe the 1st Law of Thermodynamics
The total energy of a system is constant
Energy can neither be created nor destroyed
Energy can be converted from one form to another
State some types of energy
Kinetic energy
Potential energy
What is Gibbs free energy ?
The energy needed to transform substrates into the transition state.
All reactions need to overcome the energy barrier
Describe Gibbs free energy for a graph where free energy of substrate is equal to product
Delta G = 0
Describe Gibbs free energy for a graph where free energy of substrate is higher than the product
Delta G = negative
So reaction is favourable
Describe Gibbs free energy for a graph where free energy of substrate is lower than the product
Delta G = positive
So reaction is unfavourable
Exergonic
Favourable
-delta G
Releases more energy than input
Endergonic
Unfavourable
+delta G
Requires more energy input than it yields
Explain how enzyme reactions can be coupled to utilise ‘free energy’
1st step of glycolysis : Phosphorylation of glucose : endergonic
Coupled to hydrolysis of ATP –> ADP + Pi :
exergonic
State an example of a catabolic reaction
Breakdown of glucose to pyruvate
Mobilisation of fatty acids from lipid stores to feed into cellular respiration
Metabolism is not 100% effective at capturing food energy.
What form of energy is most commonly lost in the process ?
Thermal energy
