Cellular respiration and photosynthesis. Aerobic cellular respiration

Photosynthesis and respiration are two processes that underlie life. They both occur in the cage. The first - in plant and some bacterial, the second - and in animals, and in plant, and in mushroom, and in bacterial.

It can be said that cellular respiration and photosynthesis are processes that are opposite to each other. In part this is correct, since oxygen is absorbed during the first stage and carbon dioxide is released, and in the second case, vice versa. However, these two processes are incorrect even to compare, since they occur in different organoids using different substances. The goals for which they are needed are also different: photosynthesis is necessary for obtaining nutrients, and cellular respiration is for the production of energy.

Photosynthesis: where and how does this happen?

It is a chemical reaction aimed at obtaining organic substances from inorganic substances. An obligatory condition for photosynthesis is the presence of sunlight, since its energy acts as a catalyst.

Photosynthesis, characteristic of plants, can be expressed by the following equation:

• 6CO ₂ + 6H ₂ O = C ₆ H ₁₂ O ₆ + 6 O ₂ .

That is, from six molecules of carbon dioxide and the same molecules of water in the presence of sunlight, the plant can get one molecule of glucose and six oxygen.

This is the simplest example of photosynthesis. In addition to glucose, other more complex carbohydrates, as well as organic substances from other classes, can be synthesized in plants.

Here is an example of the production of amino acids from inorganic compounds:

• 6CO ₂ + 4H ₂ O + 2SO ₄ ^2- + 2NO ₃ ^- + 6H ⁺ = 2C ₃ H ₇ O ₂ NS + 13 O ₂ .

As you can see, from two molecules of carbon dioxide, four water molecules, two sulfate ions, two nitrate ions and six hydrogen ions using solar energy, two molecules of cysteine and thirteen - oxygen can be obtained.

The process of photosynthesis occurs in special organelles - chloroplasts. They contain the pigment chlorophyll, which acts as a catalyst for chemical reactions. Such organelles are found only in plant cells.

Structure of chloroplast

It is an organoid that has the shape of an elongated ball. The size of the chloroplast is usually 4-6 microns, but in the cells of some algae it is possible to detect giant plastids - chromatophores, whose size reaches 50 microns.

This organelle belongs to two-membrane. It is surrounded by outer and inner shells. They are separated from each other by an intermembrane space.

The internal environment of the chloroplast is called the stroma. It contains thylakoids and lamellae.

Thylakoids are flat disc-shaped bags of membranes containing chlorophyll. This is where photosynthesis takes place. Going into piles, thylakoids form granules. The number of thylakoids in the facial can vary from 3 to 50.

Lamella are structures formed by membranes. They are a network of branched channels, the main function of which is to provide a connection between the faces.

Chloroplasts also contain their own ribosomes, necessary for protein synthesis, and their own DNA and RNA. In addition, there may be inclusions consisting of reserve nutrients, mainly starch.

Cell respiration

There are several types of this process. There is anaerobic and aerobic cellular respiration. The first is characteristic of bacteria. Anaerobic respiration occurs in several types: nitrate, sulfate, sulfuric, iron, carbonate, fumarate. Such processes allow bacteria to obtain energy without the use of oxygen.

Aerobic cellular respiration is characteristic of all other organisms, including animals and plants. It occurs with the participation of oxygen.

In fauna, cellular respiration occurs in special organoids. They are called mitochondria. In plants, also cellular respiration occurs in the mitochondria.

Stages

Cellular breathing takes place in three stages:

1. Preparatory stage.
2. Glycolysis (anaerobic process, does not require oxygen).
3. Oxidation (aerobic stage).

Preparatory stage

The first stage is that complex substances in the digestive system are split into simpler ones. Thus, amino acids are obtained from proteins, fatty acids and glycerin from lipids, and glucose from complex carbohydrates. These compounds are transported into the cell, and then directly into the mitochondria.

Glycolysis

It consists in the fact that under the action of enzymes glucose is cleaved to pyruvic acid and hydrogen atoms. In this case, ATP (adenosine triphosphoric acid) is formed. This process can be expressed by the following equation:

• C ₆ H ₁₂ O ₆ = 2 C ₃ H ₃ O ₃ + 4H + 2ATP.

Thus, in the process of glycolysis from one molecule of glucose, the body can receive two molecules of ATP.

Oxidation

At this stage, the pyruvic acid formed during glycolysis reacts with oxygen under the action of enzymes, resulting in the formation of carbon dioxide and hydrogen atoms. These atoms are then transported to cristae, where they oxidize to form water and 36 ATP molecules.

So, in the process of cellular respiration, in total 38 ATP molecules are formed: 2 at the second stage and 36 - at the third stage. Adenosine triphosphoric acid is the main source of energy that the mitochondria supply to the cell.

Structure of mitochondria

The organoids in which respiration occurs are also found in animals, in plant cells , and in fungal cells. They have a globular shape and a size of about 1 micron.

Mitochondria, like chloroplasts, have two membranes, separated by an intermembrane space. What is inside the shells of this organoid is called a matrix. It contains ribosomes, mitochondrial DNA (mtDNA) and mtRNA. In the matrix passes glycolysis and the first stage of oxidation.

From the inner membrane are formed folds, similar to the crests. They are called cristae. Here passes the second stage of the third stage of cellular respiration. During it, the most molecules of ATP are formed.

Origin of two-membrane organoids

Scientists have proved that the structures that provide photosynthesis and respiration appeared in the cell through symbiogenesis. That is, once they were separate organisms. This explains why both in mitochondria and in chloroplasts have their ribosomes, DNA and RNA.