Chem: Fuel

3 main purposes of food for survival:

growth and development, provision of energy, repair and rebuild the body

what are energy contents?

the amount of chemical energy stored in food that is released during metabolism. measured in kcal or kJ

where can the body get energy from

Carbohydrates, lipids (fats and oils), protein

what is energy value

the energy available to a body from food/nutrient

why is the energy value of a food lower than its energy content?

because energy is lost during: incomplete digestion, metabolic/heat loss, nutrient processing

where does the energy in food originate from

the sun where photosynthesis converts light energy into glucose which is stored as starch.

what are biomolecules

organic molecules that are produced by a living organism that are essential to carry out biological processes

types of biomolecules:

carbs, lipids (fats), protein + nucleic acids

how do we yield energy

through cellular respiration whichis the oxidation of glucose.

protein storage

proteins are not stroed and are used for the energy only as a last resort

what is protein synthesis

the process where cells build proteins from amino acids through condensation reaction which is catalysed by enzymes.

what is condensation reaction

a chemical process where two molecules combine to form one larger molecule, releasing water as a byproduct to form new bonds. endothermic.

what is protein digestion

the process by which proteins are broken down into amino acids through exothermic hydrolysis reactions.

what is hydrolysis reaction

a chemical process where a larger molecule is broken down into smaller units by the addition of water, often involving the cleavage of bonds. adding water to split bonds. exothermic.

why do molecules with less oxygen produce more energy?

because molecules with fewer oxygen atoms have more C-H bonds which are higher energy and release more energy during oxidation.

what does more oxygen atoms present mean?

meaning that they have already been partially oxidised and are more stable.

what is a fuel

a substance with stored energy that can undergo a reaction (combustion) to release energy that can be used for heat or power.

what is a biofuel

a renewable fuel that is produced from living or recently deceased plant or animal matter. (bioethanol, biodiesel, biogas)

what is non renewable.

means that it cannot be replenished in a lifetime and is being consumed at a faster rate than it is being produced.

what is renewable.

means that it can be replinshed naturally in a liftime and is being produced at a faster rate than it is being consumed.

renewable fuels examples:

bioethanol, biodiesel, biogas, biomass

non-renewable fuels examples:

coal, natural gas, crude oil (petrol), coal seam gas, liquefied petroleum gas, uranium

which food group has the highest energy content?

Lipids (fats and oils) have the highest energy content.

what is the energy content of a macronutrient

the maximum amount of energy that the body can extract from the given mass of the macronutrient (via oxidation). measured in kJ/g or kcal.

why do we not measure macronutrients in moles

because they contain a mixture of compounds with different molecular weights, making moles an impractical measure for energy content.

what is the primary energy source for most cells

glucose which is oxidised to form CO2 through cellular respiration

what is a fossil fuel

non renewable fuel source that is created by the fossilisation of dead plant and animal matter (coal, crude oil, natural gas)

what is a combustion reaction

when a fuel is burnt in oxygen releasing energy and producing carbon dioxide and water.

what are the two types of combustion

incomplete and complete combustion

complete combustion

when a fuel is burnt in excess oxygen producing CO2 and H20

incomplete combustion

when a fuel is burnt in limited oxygen producing CO (carbon monoxide)

combustion equation

fuel + O2 > CO2 + H20 (balance using CHO)