Food storage in living organisms

“In order to love who you are, you cannot hate the experience that shaped you.”

GOOD MORNING, fellow travellers. Did you know that we are travelling straight to a grade one in CSEC biology? Well, if you didn’t, you know now! You can only do this if you keep up with your responsibilities, the most important of which is your schoolwork. This week, we will be looking at food storage in living organisms. Did you realise that animals also store food? This is what happens when you consume more than your body needs; it is all converted to fat and stored, hence, the beginning of obesity.

WHY DO ORGANISMS NEED TO STORE FOOD?

Remember that organisms include both plants and animals. They store food in order to:

■ Provide for themselves when food is scarce. Can you think of times when this might be so? Did you say in winter and in times of drought? If you did, then you are correct!

■ Avoid the need for constant intake and/or constant manufacturing of food. Think about it. If animals were not able to store food for short periods, then they would not be able to stop eating; and if plants were not able to store food, they would not be able to stop manufacturing food.

■ Produce reproductive structures, such as fruits and seeds.

■ Provide for developing embryos.

WHERE IS THE FOOD STORED? STORAGE IN ANIMALS

■ Animals store food either in specific areas of their bodies, e.g., as glycogen in the liver, and as fat all over their bodies, under the skin and around the organs. The storage of glycogen in the liver is short term since, as soon as the animal needs energy, the glycogen will be converted to glucose, which is the substrate used in respiration. Remember, respiration is the process by which the organisms supply themselves with energy. Fat storage is more long term. Some animals use the stored fat as insulation and as a food source in winter, e.g., hibernating animals.

■ In eggs – Food is stored in the form of protein in the yolks of eggs. This provides food for the developing embryo.

STORAGE IN PLANTS

■ Food is stored in special organs formed by roots, stems and leaves, e.g., of storage in a root – carrot; in a stem – sugar cane; in leaves – onion.

■ These storage organs are known as vegetative organs and can be found either above or below the ground. Sugar cane and onions are examples of storage organs found above the ground, while carrot, ginger, and potato are examples of those found below the ground. These are also known as perennating organs, and they allow the plant to survive under unfavourable conditions. These structures also act as means of asexual reproduction, having the ability to produce new plants that are identical to the parent plant. The following are examples of storage organs.

Underground stems:

■ Rhizomes, e.g., ginger.

■ Stem tuber, e.g., Irish potato, yam.

■ Corms, e.g., coco, dasheen.

UNDERGROUND ROOTS

■ Root tubers, e.g., cassava, sweet potato.

■ Roots, e.g., carrot, turnip, radish.

LEAVES

■ Bulbs – onions

STEMS

Sugar cane

SEEDS

In fruits – succulent fruits store mainly sugars to attract animals. The animals, after consuming the fruit, help to disperse the seeds in the fruit.

In seeds, food is stored in cotyledons or endosperms. Starch, proteins and lipids are foods that are stored for the use of the embryo during germination.

Above are diagrams of some of the examples that were given. Check your textbooks and you will be sure to find more examples of these and other storage organs. Have you been asking why storage organs are being studied under the heading of transport? Well, I hope that by now you would have realised that without the transport systems, the foods to be stored would not have arrived at their destinations. In animals, the products of digestion are transported by the blood to the different parts of the body; in plants, the food that is manufactured in the leaves is transported by the phloem to the different storage regions of the plant.

See you next week, when we will start a new topic.