PROPERTIES AND FUNCTIONS OF THE CELLS IN LIVING ORGANISMS

The studies of the cell world is wide almost one of the widest topic in biology as I far as I know. Talking about the introduction to the cells in organisms in my various previous post, today I will be talking about the some properties and function of the cell.

Source - Pixabay

NUTRITION IN CELLS

All living organisms need food to provide energy. They need carbohydrates, proteins and fats for the production of new protoplasm for repair, to grow and for the energy needed to carry out these chemical reactions, as well as to move, to reproduce, and so on. Some cells can make their own basic carbohydrate molecules. They are known
as autotrophs and this is autotrophic nutrition.

There are two main ways in which autotrophs make food.

Photosynthesis: Most autotrophs carry out photosynthesis. They capture light energy with the green pigment chlorophyll and use it to combine carbon dioxide and water molecules to make simple carbohydrates. They then use
these carbohydrates to make more complex carbohydrates such as cellulose and also to make fats. They add nitrates to make proteins.

Chemosynthesis: Some autotrophs use energy from the breakdown of chemicals, such as hydrogen sulphide, to combine small molecules such as carbon dioxide and water to make carbohydrates.

Other cells get their food by taking in materials from other organisms. They may break down (digest) the organism themselves, or it may be digested outside the cell, so that the cell simply
absorbs the products of digestion. Cells that need to feed off other living cells are known as heterotrophs, and this is heterotrophic nutrition.

Carbohydrates, proteins and fats are the nutrients that all living cells need in relatively large amounts. They are known as macronutrients. These foods are broken down into small units, which can be taken into the body by special proteins called enzymes. Enzymes are very important in all the chemical reactions of the cell and the body. They speed up reactions, such as the breakdown of complex carbohydrates into simple sugars in you gut.

The macronutrients are very important for life. However, there are other nutrients that are only needed in very small quantities, but which are also very important for the healthy functioning of the cell (and the whole organism). These are known as micronutrients and they include vitamins and minerals.

There are different ways in which you can see the effect of micronutrients on cells. You can grow colonies of spirogyra in water containing different mixtures of micronutrients, and in pure water. If you keep all the other conditions the same, you can see the effect of the presence or absence of the micronutrients on the growth of the algal cells.

Nitrates are very important micronutrients for plant cells, because the plant cells need them to make proteins. You can investigate the effect of different levels of nitrates on plants by growing plants in pots and giving them different levels of
nitrate fertiliser and then recording how they grow

CELLULAR RESPIRATION

Cells need food to supply energy. The energy in chemical bonds of the food molecules is not available to the cells to use.

Glucose is a sugar that is produced as the result of digestion in heterotrophs and by photosynthesis in most autotrophs. During the process of cellular respiration, glucose is broken down to release energy that be used by the cell. If glucose is broken down using oxygen, this is known as aerobic respiration. It produces the maximum amount of energy. Carbon dioxide and water are produced as waste products.

The reaction can be summed up as follows:
Glucose + oxygen - carbon dioxide + water

• energy (ATP)

It is called aerobic respiration because it uses oxygen from the air. Aerobic respiration takes place in the mitochondria in cells. They have a folded inner membrane that provides a large surface area for the enzymes involved in aerobic
respiration. Cells that use a lot of energy, such as muscle cells, liver cells and the rods and cones of your eye contain many mitochondria because they use a lot of energy.

All your cells need energy to carry out the reactions of life, and respiration provides this energy.

Respiration releases energy from the food we cat, so that the cells of the body can use it. The energy that is used by the cells is stored in the form of a molecule known as ATP, which stands for adenosine triphosphate. This is an adenosine molecule with three phosphate groups attached to it. When energy is needed for any chemical reaction in the cell the third phosphate bond is broken in an hydrolysis reaction. This results in a new compound, ADP or adenosine diphosphate, a free inorganic phosphate group, and the all-important energy needed in the cell. This is a reversible reaction, and so during aerobic respiration the energy from the reactions of glucose with oxygen is used to produce large quantities of ATP ready for use in the cells. This is why cellular
respiration is so very important: ATP is the single energy providing and energy storing molecule for all the processes in living cells.

Your cells need energy from ATP to carry out the basic functions of life, known as metabolism. One of the cells' main functions is to build up large molecules from smaller ones to make new cell material (anabolism). Much of the energy
in respiration is used for these 'building' activities. Cells also break large molecules down into smaller molecules. This is known as catabolism and it also fumarate
requires energy.

Anabolism + catabolism = metabolism

Another important use of the ATP energy from respiration is to make muscles contract. Muscles work all the time in your body, even when you are not aware of using them. Even when you asleep, your heart is beating, your rib muscles and diaphragm contract as you breathe, your gut is churning - and all of these muscular activities use energy

We are warm-blooded'. This means that our bodies are the same temperature inside, almost regardless of the temperature around us. On cold days, we use energy to keep our body warm, while place before on hot days, we use energy to sweat and keep our body cool.

The ATP produced by aerobic respiration in cells also provides energy for the active transport of some materials across cell boundaries.

Aerobic respiration is not a simple process. It is made up a many different reactions. Some of them take place in the cytoplasm and do not use oxygen, These are the reactions of glycolysis. Another set of reactions form a cycle that repeats all the time. These reactions are known as the Krebs cycle and they take place in the mitochondria. Carbondioxide is produced. Hydrogen ions and electrons are also removed during the Krebs cycle.

They are passed along an electron transport chain where ATP is made. The final stage of the electron transport chain is when the hydrogen ions and electrons at combined with oxygen to form water. Which is the other waste product of the process.

ANAEROBIC RESPIRATION

Sometimes cells cannot get all the oxygen they need, but they still break down glucose to make ATP. This type of respiration is known as anaerobic respiration because it does not use oxygen. It can take place in the cells of most types ot organisms, including humans. Anaerobic respiration is basically the process of glycolysis, which takes place before the Krebs cycle in aerobic respiration.

Anaerobic respiration produces far less ATP than acrobic respiration. In animal cells, anaerobic respiration produces a different waste product, called lactic acid. The body cannot get rid of lactic acid by breathing it out, as it does with carbondioxide, so when the exercise is over, lactic acid has to be broken down. This needs oxygen, and the amount of oxygen needed to break down the lactic
acid is known as the oxygen debt. After exercise, the lactic acid is oxidised by oxygen to produce carbon dioxide and water.

Anaerobic respiration
Glucose lactic acid + energy (ATP)

Anaerobic respiration does not only affect animals, it takes place in all living organisms. In some ways, we have out anaerobic respiration to good use, both in our industries and in our homes. For example, one of the microorganisms that is most useful to people is yeast, a single-celled fungi.

When yeasts have plenty at oxygen, they respire aerobically, breaking down sugar to provide energy for the cells, and producing water and carbon dioxide as waste products.

However, yeast also respire anaerobically. when yeast cells break down sugar in the absence of oxygen, they produce ethanol (commonly referred to as alcohol) and carbon dioxide. The anaerobic respiration of yeast is sometimes referred to as fermentation.

The yeast cells nced aerobic respiration because it provides more energy than anaerobic, so it allows them to grow and reproduce. However, once there are large numbers of yeast cells, they can survive for a long time in low oxygen conditions and will break down all the available sugar to produce ethanol.

People have used yeast for making bread and alcoholic drinks tor thousands ot years. Yeast was used to make bread in Egypt in 4 000 BC, and some ancient wine found in Iran dates back to 5 000 BC

When fruits fall to the ground and begin to decay, Wild yeasts present on the skin break down the fruit sugar and form ethanol and carbon dioxide. These fermented fruits can cause animals to become drunk when they eat them -and this is probably how our ancestors discovered alcohol.

We now use this same reaction in a controlled way to make beers and emu (oguro in my local diat). In both cases, the yeast has to be supplied with carbohydrates to act as an energy source for respiration.

Large amounts of ethanol are poisonous to yeast as well as to people. This is why the alcohol content of wine is seldom higher than 14 percent-once it gets much higher, it kills all the yeast and stops the Fermentation.

The fermentation of maize and sugar cane to produce ethanol for use as a fuel in motor cars is another important use of anaerobic fermentation.
This is a way in which we can reduce the amounts of carbon dioxide produced and given off in the atmosphere.

It is not just the anaerobic respiration of yeast that is important. The anaerobic fermentation of milk with different types of bacteria can give us cheese and yoghurt, which are staple parts of the human diet in many areas of the world. The use of anaerobic respiration to break down human and animal waste products to produce biogas(methane) at a domestic and small village level is Increasing in many parts of the world. There is Increasing interest in using this on a larger scale to produce another more eco-friendly fuel.

REFERENCES

. https://byjus.com/biology/cells/

. https://www.britannica.com/science/cell-biology

. https://sciencing.com/six-main-cell-functions-6891800.html