Metbaolism Flashcards
what is metabolism
Metabolism is the set of processes which derive
energy and raw materials from food stuffs and use
them to support repair, growth and activity of the
tissues of the body to sustain life
What is cell metabolism
• Biological chemistry occurs by making small chemical changes
• Many reactions but only a relatively few reaction types
• Reactions are organised into metabolic pathways, which are distinct but integrated
– Some metabolic pathways occur in all cells
– Others are restricted to some cell types
– Some may be further restricted to compartments within cells
What are the 2 main types of metabolic pathway
• Catabolic pathways – Break down larger molecules into smaller ones (intermediary metabolites) – Release large amounts of free energy – Oxidative – release H atoms – ‘ reducing power’
• Anabolic pathways
– Synthesise larger important cellular components
from intermediary metabolites
– Use energy released from catabolism (ATP)
– Reductive (i.e. use H released in catabolism)
What are fuel molecules metabolised to supply?
Fuel molecules are metabolised to supply:-
1. Building block materials (sugars, amino acids, fatty acids)
– dynamic state of cell components (turnover)
– cell growth and division
– repair
- Organic precursors (Acetyl CoA)
– allow for inter-conversion of building block material - Biosynthetic reducing power (NADH, NADPH)
- Energy for cell function (Adenosine triphosphate, ATP)
What is energy used for?
What sort of work?
- Biosynthetic work (anabolism) - synthesis of cellular components
- Transport work - membranes
(a) maintenance of ion gradients (Na+, K+, Ca2+)
(b) nutrient uptake - Specialised functions
(a) Mechanical work - muscle contraction
(b) Electrical work - nervous impulse conduction
(c) Osmotic work - kidney
What are the standard units of energy?
Units
Standard International Unit = Joule (J) 1,000 Joules = 1 kJ
Calorie (often quoted relating to nutrition) = 1 Kcal 1 kcal = 1,000 calories
1 Kcal = 4.184 (4.20) k Joules
What are the energy values of fat, carbohydrate, protein and alcohol?
Fat Carbohydrate Protein Alcohol
kJoules.g-1 ~37 ~17 ~16 ~29
Kcal.g-1 ~9 ~4 ~4 ~7
What are the energy requirements of the whole body
kcal.24 hours-1 ( x 4.2 for kjoules.24 hours-1) 70 kg man/ 58 kg woman (average 18 year old student)
- Basal Metabolic Rate - approx. 1,700/1,400 kcal (~7000/~5800 kJ)
Energy required by an awake individual during physical, digestive and emotional rest at 18oC Sum of all of the tissues in the body - Activity (Muscular Work) - approx. 1,000 - 3,000 kcal
(4,000-12,000 kJ)
Amount depends on type, intensity and duration of activity
(Skeletal and heart muscle) - Specific Dynamic Action of Food - approx 150 kcal (~650 kJ) Energy cost of ingestion, digestion and absorption of food.
How else is energy used
Energy lost as heat
4. When energy intake (FOOD) > energy required for the above then excess energy is stored.
a. growth - synthesis of new tissue
(repair, children, pregnancy)
b. production of adipose tissue
5. When energy intake < energy requirements then tissue
is lost
6. Can survive approx. 20 - 70 days, if given water
7. Must be important regulatory mechanisms to govern
supply, storage and utilisation of energy
What type of energy is used in biology?
- Energy exists in many forms all of which are interconvertible
- Heat, Light, Mechanical, Electrical, Osmotic, CHEMICAL BOND
- Biology uses chemical bond energy predominantly to drive energy requiring activities
- Used directly without prior conversion to heat
- Humans are isothermal - can not use heat energy for work
All cellular activities are expressions of chemical reactions in which chemical bonds are broken or formed
A characteristic energy change accompanies each chemical reaction:-
• Exergonic - release energy
• Endergonic - require energy
What is Gibbs free energy?
To what extent can energy released be used?
• Useful energy = Free energy G (Gibb’s Free Energy)
• Change in free energy Delta G
• Value negative for exergonic reactions
What’s the difference between an endergonic and exergonic reaction?
Exergonic
Delta G < 0
Reaction is spontaneous
Products have lower energy than reactants
Endergonic
Delta G > 0
NOT spontaneous
Energy input
What are standard conditions?
Standard free energy change
Go 25oC, 1 atmosphere pressure,
1 Molar concentration of reactants and products
Go’ pH = 7.0
What are redox reactions?
Chemical bond energy of fuel molecules is released by oxidation reactions
Oxidation - removal of electrons (e-) or removal of H-atoms (H+ + e-)
All oxidation reactions accompanied by a reduction reaction,
known as REDOX REACTIONS
What are hydrogen carrier molecules?
When fuel molecules are oxidised electrons and protons are transferred to carrier molecules
Major carrier molecules
Nicotinamide adenine dinucleotide
NAD+ NADH + H+
Nicotinamide adenine dinucleotide phosphate
NADP+ NADPH + H+
Flavin adenine dinucleotide
FAD FADH2
• Total concentration of ‘oxidised and reduced’ carriers is constant
• Therefore, must be a cycle between oxidative processes
and reductive processes
• Act as carriers of ‘reducing power’ for
a) ATP production (NADH + H+)
b) Biosynthesis (NADPH)
• Complex molecules
– Contain components from vitamins (B vitamins)
• Converted to reduced form by adding two H atoms (H+ + e-)
• H+ dissociates into solution
