Biología Tema 1 - La Composición de la Materia Viva PDF

# La composición de la materia viva ## 1.1. Características que definen a los seres vivos - Una composición química similar. All living beings are composed of the same chemical elements, with carbon being the most important. - Se organizan a partir de unidades similares. All living beings are made...

# La composición de la materia viva ## 1.1. Características que definen a los seres vivos - Una composición química similar. All living beings are composed of the same chemical elements, with carbon being the most important. - Se organizan a partir de unidades similares. All living beings are made up of cells. - Llevan a cabo las mismas funciones vitales: nutrition, which allows them to obtain matter and energy from the environment and transform it into complex substances for its maintenance; relationship, which allows them to detect changes in the environment and maintain their balance by controlling all their functions; and reproduction, which allows them to perpetuate the species. ## 1.2. Los bioelementos - Los seres vivos están compuestos por átomos and molecules of the same chemical elements that make up the rest of the universe, but organized in a special way. This gives living matter a higher degree of complexity, both chemically and structurally. - Bioelements are the chemical elements that participate in the formation of living beings. They are classified, according to their abundance, into primary bioelements, secondary bioelements and trace elements. - **Primary bioelements:** They account for 96% of living matter and are essential for forming the biomolecules that make up living beings. The main element is carbon (C), along with hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P) and sulfur (S). These elements are ideal for life because they are relatively abundant, easily assimilated, have a low atomic mass and form very stable covalent bonds. - **Secondary bioelements:** Although they appear in smaller quantities, these elements play important physiological roles. They are mainly sodium (Na), potassium (K), magnesium (Mg), calcium (Ca) and chlorine (Cl). - **Trace elements:** They are found in very small proportions. However, they are indispensable. Many of them act as catalysts in chemical reactions. They include iron (Fe), copper (Cu), iodine (I) or lithium (Li). ## 1.3. Las biomoléculas orgánicas y los compuestos inorgánicos - **Organic biomolecules:** They are molecules exclusive to living beings, formed by the combination of different bioelements. - **Inorganic compounds:** They are not exclusive to living beings. They include water, mineral salts and some gases. ## El carbono - Carbon is the essential chemical element in life on Earth. Its chemical properties allow it to form structures that serve as the basis for the construction of the organic biomolecules. - The characteristics of the carbon atom are its tetravalency, which allows it to form long chains and provides great molecular variability. ## Los grupos funcionales - A functional group is an atom or group of atoms that replace one or more of the hydrogens attached to the carbon chain and give the molecule its characteristic properties. ## Los tipos de fórmulas de los compuestos del carbono - **Molecular formula:** Indicates the total number of atoms that make up the molecule, such as C2H6. - **Semi-developed formula:** It is the most common formula. It shows all the atoms that are linked to the same carbon atom grouped together, such as CH3-CH3. - **Developed formula:** Indicates how the atoms that make up the molecule are linked to each other, such as H-C-C-H. # El agua y las sales minerales - Water and mineral salts are the inorganic compounds that make up living matter. They differ from organic biomolecules as they are also present in inert matter. ## 2.1. La estructura del agua - Water is the most abundant substance in living matter. - The water molecule is formed by two hydrogen atoms and one oxygen atom. When they bond, they distribute the electrons they share unevenly, being closer to the more electronegative oxygen atom. This gives the water molecule a dipolar character, meaning that it has a part with a higher density of negative charge (electronegative) closer to the oxygen and another part with a higher density of positive charge (electropositive) on the hydrogens. - The dipolar character of water allows it to establish hydrogen bonds with other water molecules, forming groups with higher molecular mass. This makes it a liquid at room temperature. Water can also form hydrogen bonds with other polar substances. ## 2.2. Las sales minerales - Mineral salts are inorganic compounds that perform a wide variety of functions. In organisms, they occur mainly in two forms: as precipitated salts or dissolved in water. ### Las sales precipitadas - They mainly have a skeletal function. This means that they provide structure to skeletal structures. For example, carbonates form the shells or shells of many animals, phosphates deposit in bones or silicates are found in the internal skeleton of sponges. ### Las sales disueltas - In water, salts are dissociated into anions (such as chlorides, phosphates, carbonates, nitrates, bicarbonates, etc.) and cations (such as calcium, magnesium, iron, sodium, potassium, etc.). These ions have different functions. - **Regulatory functions:** They contribute to the maintenance of homeostasis or stability of the internal environment through processes such as: - Maintaining salinity and pH constant within the organism. - Regulation of enzyme activity. - Regulation of osmotic pressure and cell volume. - **Specific functions:** They include: - Muscle contraction: where sodium, potassium and magnesium are involved. - Blood coagulation: where calcium plays a key role. - Transmission of the nerve impulse: where sodium, potassium and calcium act. # Los glúcidos - Glúcidos or carbohydrates are organic biomolecules mainly composed of carbon, hydrogen and oxygen, following the general formula (CH2O)n. - They are classified into three main groups, depending on their size and structure: monosaccharides, disaccharides and polysaccharides. - They are also called sugars because of their sweet taste. ## 3.1. Los monosacáridos - Monosaccharides are the simplest glúcidos, they cannot be broken down into simpler molecules. - Important monosaccharides are glucose, fructose and ribose. ## 3.2. Los disacáridos - Disaccharides are simple glúcidos formed by two monosaccharides linked by a covalent bond called O-glycosidic. - Some important disaccharides are sucrose, lactose and maltose. ## 3.3. Los polisacáridos - Polysaccharides are complex glúcidos formed by hundreds or thousands of monosaccharide molecules linked by O-glycosidic bonds. - They are characterized by having no sweet taste. - Some important biological polysaccharides are cellulose, starch and glycogen. ## 3.4. Las funciones de los glúcidos - Glúcidos have important functions for the cell. - **Energy function:** - Glucose is the main energy source for the cell. It is used as fuel in cellular respiration. - Monosaccharides, disaccharides and polysaccharides are transformed in the cell into glucose, also providing energy. - Some polysaccharides are storage molecules of energy for the cell. Starch is stored in plant cells, especially in tubers and seeds. Glycogen is stored in liver and muscle cells in animals. - **Structural function:** - Cellulose is the main component of the plant cell walls. - Ribose and deoxyribose are part of the structure of nucleic acids. - **Other functions:** - Some glúcidos are precursors of other substances with regulatory function; for example, glucose is the precursor of vitamin C or ascorbic acid. - Some glúcidos are linked to some proteins of cell membranes, glycoproteins, involved in the recognition between cells. # Los lípidos - Lipids are a very diverse group of biomolecules composed of carbon, hydrogen, oxygen and, sometimes, phosphorus. They are characterized by being low density, insoluble in polar solvents such as water and soluble in apolar organic solvents such as ether or chloroform. ## 4.1. La clasificación de los lípidos - Lipids are classified into two main groups: saponifiable lipids and non-saponifiable lipids, depending on whether or not they contain fatty acids in their structure. - **Saponifiable lipids:** They are the most abundant. They are esters of fatty acids. These lipids react with strong bases (NaOH or KOH), yielding fatty acid salts and alcohols as reaction products. This reaction is known as saponification. Saponifiable lipids include fats, phospholipids, glycolipids and waxes. - **Non-saponifiable lipids:** They do not contain fatty acids in their composition; therefore, they do not give the saponification reaction. They include terpenes and steroids. ## 4.2. Los ácidos grasos - Fatty acids are organic acids with the following characteristics: - They have a long hydrocarbon chain, with an even number of carbon atoms, ranging from 12 to 24. - They have a carboxyl group as a functional group, attached to one end of the chain. - They can be saturated fatty acids, when the carbon chain only has single bonds, and unsaturated fatty acids, if the chain has one or more double bonds. - The most common double bonds in living organisms have the cis isomeric form, which causes the curvature of the hydrocarbon chain. When the double bond has the trans form, the fatty acid has a linear structure, similar to that of saturated fatty acids. ## 4.3. Los lípidos saponificables y sus funciones - **Fats:** They are formed by a molecule of glycerol (an alcohol) linked to one, two or three fatty acids, the latter being called triacylglycerides. - They are hydrophobic molecules, meaning they repel water, as they do not contain polar groups or electrical charges. Their functions include: - *Storing energy* in animal adipose cells, or in some plant parts such as seed oils or fruits. - *Providing thermal insulation* in the organism, located under the skin of animals living in cold habitats. - *Protecting* vital organs such as the heart, kidneys, etc. - **Phospholipids:** They are lipids in which a phosphate group is part of the molecule. - They are classified into two major groups: *phosphoglycerides* and *sphingolipids*. - *Phosphoglycerides* are formed by glycerol linked to two fatty acids and a phosphate group, which in turn is bonded to another alcohol. - *Sphingolipids* are formed by sphingosine (an aminoalcohol) linked to a fatty acid and a phosphate group linked to another alcohol. - All phospholipids are amphipathic, meaning they have a hydrophilic or polar head (the phosphate and alcohol groups) and a hydrophobic or apolar tail (the fatty acids). Their function is to form the basis of all cell membranes. They have the ability to form a bilayer where the polar head is on the outside or aqueous side and the apolar tails are hidden in the interior. Sphingolipids are specific to the myelin sheaths that coat the neuron axons. ## 4.4. Los lípidos insaponificables y sus funciones ### Los esteroides - These are formed by a derivative of a cyclic molecule called *sterane*. - Their functions include forming part of the cell membrane, such as cholesterol, which provides it with greater rigidity; or regulating some processes, such as sexual reproduction in the case of sex hormones; or calcium metabolism, such as vitamin D. ### Los terpenos - These are formed by derivatives of a molecule called *isopreno*. - Their functions include: - Participating in photosynthesis, such as pigments called xanthophylls and carotenoids. - Regulating some cell processes, such as β-carotene, which is the precursor of vitamin A. # Las proteínas - Proteins are formed by carbon, hydrogen, oxygen, nitrogen and, to a lesser extent, sulfur and phosphorus. They are macromolecules formed by the union of simpler units called amino acids. - Proteins are the most abundant biomolecules in living beings after water. There are thousands of different proteins, each with a specific function in the organism. ## 5.1. Los aminoácidos - Amino acids are organic molecules that contain an amino group (-NH2), a carboxyl group (-COOH) and a side chain or functional group (R). - There are many different amino acids, determined by the R group; however, only twenty of them make up proteins. These amino acids are called α-amino acids because the amino group, the carboxyl group and the radical are linked to a carbon atom called the α-carbon. ## 5.2. Las funciones de las proteínas - Proteins perform important functions for living beings. - **Structural function:** Many proteins are part of cellular and organic structures. Examples of proteins that carry out this function are glycoproteins, part of the cell membrane, and involved in signaling; collagen in tendons, providing flexibility and strength to tissues; keratin in nails or hair, providing hardness; histones that are part of chromatin and chromosomes. - **Reserve function:** Some proteins provide amino acids for offspring development, such as ovalbumin in eggs or casein in milk. - **Transport function:** Some proteins are responsible for transporting other substances; for example, hemoglobin transports oxygen; lipoproteins transport lipids through the blood. - **Defense function:** Antibodies defend the organism against pathogens; fibrinogen and thrombin are involved in blood clotting after a wound or hemorrhage. - **Contractile function:** Some proteins allow organisms to move, such as actin and myosin, responsible for muscle contraction. - **Hormonal function:** Protein hormones regulate many processes in the body; for example, insulin and glucagon regulate glucose metabolism; luteinizing hormone (LH) and follicle-stimulating hormone (FSH) regulate the ovarian cycle. - **Enzymatic function:** Enzymes catalyze or accelerate the chemical reactions of metabolism. Some examples are amylase, which breaks down starch, or lipase, which breaks down lipids. ## 5.3. Las enzimas - Enzymes are proteins that catalyze, meaning they increase the rate of chemical reactions in the cell. - Although there is a wide variety of enzymes, they all share common characteristics: - They are catalysts, meaning that they act in small quantities and are recovered indefinitely (they are not consumed). - They are highly specific, meaning that they act on one or a few substrates and each reaction is catalyzed by a specific enzyme. ## 5.4. The structure of proteins - Proteins have a three-dimensional structure, or native structure, which gives them the ability to carry out a biological function. - If they lose this structure, they lose their function. This process is called denaturation. - The four levels of protein structure are: - **Primary structure:** It is the sequence or order of amino acids that make up the protein. This structure is maintained by covalent and stable peptide bonds,. - **Secondary structure:** It is a folding of the polypeptide chain. Interactions between different amino acids that are close in the primary structure take place, and the structure is maintained by these non-covalent bonds, mainly hydrogen bonds. There are two types of secondary structure, α-helix and β-sheet. - **Tertiary structure:** It is the shape that the molecule adopts in space. Most proteins have a globular shape in which the polypeptide chain folds, resulting in compact shapes close to the sphere. They are soluble in water. This structure is maintained by different types of interactions (hydrophobic, ionic...) between amino acid residues that may be very far apart in the primary structure but end up close when the polypeptide chain folds. - **Quaternary structure:** It is the union of several protein chains or monomers to form dimers, trimers, tetramers, etc.. Many proteins do not reach this level of structure, the monomer being the functional protein. # Los ácidos nucleicos - Nucleic acids, DNA and RNA, are macromolecules responsible for storing and transmitting genetic information. ## 6.1. Los nucleótidos - Nucleic acids are polymers formed from smaller subunits called nucleotides, which contain carbon, hydrogen, oxygen, nitrogen and phosphorus - There are five different nucleotides with a common structure, composed of three different components: - A pentose: a five-carbon monosaccharide, which can be: - β-D-ribofuranose (D-ribose) in RNA. - β-D-deoxyribofuranose (D-2-deoxyribose) in DNA. - A nitrogenous base: an organic cyclic compound that contains two or more nitrogen atoms, which can be of two types: - A purine: adenine (A) or guanine (G). - A pyrimidine: cytosine (C), thymine (T) or uracil (U). - The nitrogenous bases A, G, C and T are found in DNA, while in RNA, T is replaced by U. - A molecule of phosphoric acid ## 6.2. La formación de los ácidos nucleicos - Nucleic acids are formed by many nucleotides, linked to each other to form long chains. - The linkage of nucleotides is achieved by an ester bond between a hydroxyl group of phosphoric acid from one nucleotide and a hydroxyl group of the pentose from the next nucleotide. Therefore, each phosphoric acid molecule forms two ester bonds, one with the pentose of a nucleotide and the other with the pentose of the following nucleotide. This linkage is called a phosphodiester linkage. ## 6.3. EI ADN - Deoxyribonucleic acid or DNA is made up of deoxyribonucleotides, whose pentose is ß-D-deoxyribofuranose (D-2-deoxyribose) and the nitrogenous bases, A, T, C or G. - DNA is the molecule of heredity, whose information is defined by the sequence of nucleotides and determines the characteristics of each individual. In eukaryotic cells, it is found in the nucleus. ## 6.4. El ácido ribonucleico (ARN) - Ribonucleic acid or RNA is made up of ribonucleotides, whose pentose is ß-D-ribofuranose (D-ribose), and the nitrogenous bases are A, U, C or G. - **Characteristics of RNA:** - It is single-stranded, meaning it does not form a double helix like DNA, except in some viruses, such as reoviruses. - Its size is smaller than that of DNA, as it contains fewer nucleotides - It can be found in both the nucleus and cytoplasm of eukaryotic cells. - Its three-dimensional structure can be very complex, often forming folds and base pairings in different regions of the molecule. It forms hairpin structures. - **Types of RNA:** - **Messenger RNA (mRNA):** It is the RNA that carries the information for the synthesis of proteins. This RNA is synthesized in the nucleus and moves to the cytoplasm. - **Ribosomal RNA (rRNA):** It associates with a large number of different proteins to form ribosomes. It is composed of molecules of different sizes that, in some areas, have a secondary hairpin structure. - **Transfer RNA (tRNA):** It transports amino acids to ribosomes, placing them according to what the mRNA sequence indicates to synthesize proteins. They are small molecules, formed by a single chain, folded, so that it has a secondary hairpin structure in some areas. Each tRNA binds to a specific amino acid. ## 6.5. Funciones de los ácidos nucleicos - Nucleic acids perform three important functions in the cell - **DNA** transmits genetic information from one cell to its offspring. - The genetic information contained in DNA is necessary for cellular functions to take place. Most of the information contained in DNA is used to synthesize proteins. RNA is involved in this process. - DNA allows genetic changes in organisms and, therefore, evolution. - These important functions that nucleic acids perform in cells are carried out through two fundamental processes, which are replication and protein synthesis, which has two distinct steps: transcription and translation. # La replicación y la síntesis de proteínas - **Replication:** It is the process by which a DNA molecule is duplicated, creating two identical copies of itself. - **Protein synthesis:** - **Transcription:** It is the process by which the information from a segment of DNA, corresponding to a gene, is copied into a messenger RNA molecule. Transcription takes place in the nucleus of eukaryotic cells and is catalyzed by an enzyme called RNA polymerase. This enzyme can synthesize an RNA chain as it moves along the DNA chain. The copy is made according to base complementarity, and in it, T is replaced by U. - **Translation:** It is the process by which a protein is synthesized with a specific amino acid sequence, based on the information contained in the mRNA. Translation takes place in the cytoplasm of eukaryotic cells and is carried out by ribosomes, which can read the information from the mRNA, which is encoded in the form of three-nucleotide triplets (codons), and join the amino acids in a specific sequence. # El enlace peptídico: formación de un dipéptido - This shows how amino acids join together. - **Amino acid 1** is shown on the left of the image. - **Amino acid 2** is shown on the right of the image. - The **peptide bond** is formed at the center by releasing a molecule of water. # Carácter anfótero - The structure of an amino acid is shown. - Amino acids can act as both acids and bases under different pH conditions.