How energy is transferred within and between organisms.
Energy is needed to sustain many processes and functions to allow organisms to survive. Some
organisms, such as heterotrophs cannot manufacture their own food, deriving their energy intake
from other organisms. Primary and secondary consumers fall under this definition. They gain their
energy from plant material and animal matter. Plants are classed as autotrophs, meaning they can
manufacture their own food. This is completed through the process of photosynthesis.
The main energy source for food chains and organisms originates from the sun. Photosynthesis
occurs in the chloroplasts of the leaves. In the light dependent part of photosynthesis, plants use
energy from the sun in the form of photons to excite electrons produced by the photolysis of water.
These electrons then pass down the electron transfer chain, loosing energy as they go along. This
energy is used by proteins in the thylakoid membrane to actively transport protons into the cell. The
greater H+ ion concentration inside the lumen leads to chemiosmosis – facilitated diffusion of the
protons through an ATP synthase protein. This energy can be used to form ATP from ADP and Pi,
which then combines with NADP, along with an electron, to form reduced NADP. The energy stored
in this molecule then moves into the Calvin cycle, where it reduces GP to TP which is then used to
form glucose. Glucose is one of the main food sources of a plant, so it can be used in respiratory
processes to facilitate growth. The light energy from the sun is converted into chemical energy
through this process, without which plants would not be able to survive.
The glucose produced from the light independent reaction can then be used to form starch and
cellulose. Large amounts of starch occur in storage organs like seeds and tubers and cellulose is a
major component of plant cell walls. When plants, the producers of the food chain, are eaten by the
heterotrophs like primary consumers, energy moves up the food chain. When these consumers are
eaten, energy then passes to the next trophic level and so on until it reaches the apex predator.
However, energy is lost between trophic levels, such as in excreted materials. Only around 10-20% of
energy is actually passed on. Furthermore, plants only convert between 1 and 3 percent of the suns
energy into organic matter. The majority of the sun’s energy is reflected back into space by clouds,
light doesn’t always fall on a chlorophyll molecule and a plant may not have enough photosynthetic
pigments to absorb a large range of light wavelengths. This means that higher predators need to eat
more than ones at lower trophic levels in order to meet their energy requirements. Consequently,
primary consumers must have enough energy for their own processes, but must also provide enough
energy for the secondary consumer to survive when eaten. This explains why many food chains have
a maximum of five trophic levels, as energy requirements would be too large for further trophic
Energy is needed to sustain many processes and functions to allow organisms to survive. Some
organisms, such as heterotrophs cannot manufacture their own food, deriving their energy intake
from other organisms. Primary and secondary consumers fall under this definition. They gain their
energy from plant material and animal matter. Plants are classed as autotrophs, meaning they can
manufacture their own food. This is completed through the process of photosynthesis.
The main energy source for food chains and organisms originates from the sun. Photosynthesis
occurs in the chloroplasts of the leaves. In the light dependent part of photosynthesis, plants use
energy from the sun in the form of photons to excite electrons produced by the photolysis of water.
These electrons then pass down the electron transfer chain, loosing energy as they go along. This
energy is used by proteins in the thylakoid membrane to actively transport protons into the cell. The
greater H+ ion concentration inside the lumen leads to chemiosmosis – facilitated diffusion of the
protons through an ATP synthase protein. This energy can be used to form ATP from ADP and Pi,
which then combines with NADP, along with an electron, to form reduced NADP. The energy stored
in this molecule then moves into the Calvin cycle, where it reduces GP to TP which is then used to
form glucose. Glucose is one of the main food sources of a plant, so it can be used in respiratory
processes to facilitate growth. The light energy from the sun is converted into chemical energy
through this process, without which plants would not be able to survive.
The glucose produced from the light independent reaction can then be used to form starch and
cellulose. Large amounts of starch occur in storage organs like seeds and tubers and cellulose is a
major component of plant cell walls. When plants, the producers of the food chain, are eaten by the
heterotrophs like primary consumers, energy moves up the food chain. When these consumers are
eaten, energy then passes to the next trophic level and so on until it reaches the apex predator.
However, energy is lost between trophic levels, such as in excreted materials. Only around 10-20% of
energy is actually passed on. Furthermore, plants only convert between 1 and 3 percent of the suns
energy into organic matter. The majority of the sun’s energy is reflected back into space by clouds,
light doesn’t always fall on a chlorophyll molecule and a plant may not have enough photosynthetic
pigments to absorb a large range of light wavelengths. This means that higher predators need to eat
more than ones at lower trophic levels in order to meet their energy requirements. Consequently,
primary consumers must have enough energy for their own processes, but must also provide enough
energy for the secondary consumer to survive when eaten. This explains why many food chains have
a maximum of five trophic levels, as energy requirements would be too large for further trophic
