Unit 1 Chapter 2 (1st Secondary) Biology

Trypsin is a proteolytic enzyme that breaks down proteins into smaller peptides. Biuret reagent is commonly used to test for the presence of proteins. When trypsin enzyme is present in a sample, it will break down the proteins into smaller peptides. Biuret reagent reacts with the peptide bonds in proteins, causing a color change. In the presence of trypsin enzyme, the biuret reagent will turn violet, indicating the presence of proteins that have been broken down by trypsin.

Casein is a phosphoprotein found in milk. It is the main protein in milk and is responsible for the white color of milk. It is a rich source of essential amino acids and is commonly used in the production of cheese and other dairy products. Thyroxine, insulin, and hemoglobin are not phosphoproteins. Thyroxine is a hormone produced by the thyroid gland, insulin is a hormone produced by the pancreas, and hemoglobin is a protein found in red blood cells that carries oxygen.

Dehydration reactions involve removing OH (hydroxyl) from one molecule and H (hydrogen) from another molecule, resulting in the formation of a covalent bond between the two molecules. This process leads to the synthesis of a larger molecule and the release of water as a byproduct. On the other hand, hydrolysis reactions involve breaking down a larger molecule into smaller subunits by adding OH (hydroxyl) to one subunit and H (hydrogen) to another subunit, with water being consumed in the process. Therefore, OH and H are the components involved in both dehydration and hydrolysis reactions.

Nucleic acids, such as DNA and RNA, are composed of nucleotides, which consist of a sugar molecule, a phosphate group, and a nitrogenous base. Phosphorus is a crucial component of the phosphate group in nucleotides, making it an essential element in nucleic acids. Manganese, calcium, and sulfur do not play a significant role in the structure or function of nucleic acids.

A nucleotide is composed of three components: a nitrogenous base, a phosphoric acid, and a sugar molecule. These three components together make up the structure of a nucleotide.

DNA consists of two spirally coiled strands, known as a double helix. The spiral shape allows the DNA molecule to fit within the nucleus of a cell and also facilitates the replication and transcription processes. The strands are held together by hydrogen bonds between complementary base pairs, adenine with thymine and guanine with cytosine. This spiral structure is crucial for the stability and function of DNA in storing and transmitting genetic information.

Proteins differ from one another in all of the mentioned ways. The number of amino acids in a protein determines its length and size. The type of amino acids present in a protein determines its chemical properties and functions. The order of amino acids in a protein determines its unique sequence and structure, which ultimately determines its specific function in the body. Therefore, all of these factors contribute to the differences observed among proteins.

A nucleotide of DNA is composed of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: adenine, guanine, cytosine, or thymine. In this case, the correct answer is "Deoxyribose, thymine, and a phosphate group" because it accurately represents the components of a DNA nucleotide.

A peptide bond would join two amino acid subunits in the formation of a macromolecule. A peptide bond is a covalent bond that forms between the carboxyl group of one amino acid and the amino group of another amino acid. This bond is formed through a dehydration synthesis reaction, where a water molecule is removed, allowing the amino acids to join together.

Proteins are large, complex molecules that are composed of amino acids. Amino acids are the building blocks of proteins, and they are linked together through peptide bonds to form long chains. This statement is correct because it accurately describes the composition of proteins.

Ferritin is classified as a conjugated protein because it consists of both protein and iron. Conjugated proteins are composed of a protein component and a non-protein component, such as a metal ion or a carbohydrate. In the case of ferritin, the protein component forms a shell-like structure that encloses and stores iron ions. This allows ferritin to regulate the release of iron in a controlled manner, making it an important protein for iron storage in the body.

The hydrolysis of histones produces amino acids only because histones are simple proteins. Hydrolysis is a chemical reaction that breaks down molecules by adding water. In the case of histones, the hydrolysis reaction breaks the peptide bonds between amino acids, resulting in the release of individual amino acids. Since histones are made up of amino acids linked together, the hydrolysis of histones would naturally produce amino acids as the end product.

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Glycerol is a basic unit of oils because oils are triglycerides, which are composed of three fatty acids attached to a glycerol molecule. The glycerol molecule acts as a backbone for the attachment of the fatty acids, forming the structure of oils.

Complex sugars protect the cell wall from being dissolved in water. Elodea is a fully submerged plant, and the cell wall of plants is composed of complex sugars called cellulose. Cellulose provides structural support and prevents the cell wall from breaking down in water. Simple sugars, derived lipids, and conjugated proteins do not have the same protective effect on the cell wall.

There are about 20 amino acids in all which can be linked together in different ways to make numerous protein molecules.

Diagram Y shows a condensation polymerization reaction because it depicts the formation of a larger molecule by the removal of a small molecule, such as water, during the reaction. This process is characteristic of condensation polymerization, where monomers join together to form a polymer while releasing a small molecule as a byproduct. In contrast, diagram X does not show the removal of a small molecule and therefore does not represent a condensation polymerization reaction.

Protein molecules are composed of long chains of amino acids. These amino acids are made up of carbon, hydrogen, oxygen, and nitrogen atoms. Carbon provides the backbone for the structure of the amino acids, while hydrogen and oxygen are also essential for the formation of various functional groups within the amino acids. Nitrogen is crucial for the formation of peptide bonds between amino acids, which are responsible for linking the amino acids together to form the protein molecule. Therefore, the correct answer is carbon, hydrogen, oxygen, and nitrogen.

Protein molecules are composed of amino acids. Amino acids are the building blocks of proteins and are linked together through peptide bonds to form long chains. These chains then fold into specific three-dimensional structures, which determine the function of the protein. Carbohydrates, fatty acids, and nucleotides are not the primary components of proteins.

Both ribose and deoxyribose are pentoses, meaning they have five carbon atoms. They both enter into the structure of nucleotides, which are the building blocks of DNA and RNA. Additionally, they are both monosaccharides, which means they cannot be hydrolyzed to form simpler sugars. However, the statement that both ribose and deoxyribose have an OH group attached to C2' is incorrect. Ribose has an OH group attached to C2', while deoxyribose lacks this group, hence the name "deoxy" indicating the absence of an oxygen atom.

Table salt is iodized in large part to prevent the enlargement of the thyroid gland. The thyroid gland requires iodine to produce thyroid hormones, which are essential for regulating metabolism and growth. Without enough iodine, the thyroid gland can become enlarged, leading to a condition called goiter. By adding iodine to table salt, it ensures that individuals receive enough iodine in their diet to prevent goiter and maintain proper thyroid function.

The percentage of each base can be calculated by dividing the number of bases of that type by the total number of bases and multiplying by 100. In this case, there are 66 adenine bases out of a total of 240 bases. To find the percentage of thymine and guanine, we subtract the percentage of adenine from 100 and divide by 2 since thymine and guanine are present in equal amounts. This gives us (100-27.5)/2 = 36.25/2 = 18.125 for both thymine and guanine. Therefore, the percentage of thymine and guanine is 18.125%, which can be rounded to 18.1%.

Nucleotides are the building blocks of DNA and RNA. They consist of a nitrogenous base attached to a sugar molecule. The sugar molecule in DNA is deoxyribose, while in RNA it is ribose. The carbon atoms in the sugar molecule are numbered from 1' to 5'. In a nucleotide, the nitrogenous base is attached to the 1' carbon of the sugar molecule through a glycosidic bond. Therefore, the correct answer is 1' carbon.

Proteins called enzymes carry out catalysis in biological systems. Enzymes are specialized proteins that act as catalysts, speeding up chemical reactions in living organisms. They bind to specific substrates and facilitate the conversion of these substrates into products. Enzymes are essential for various biological processes such as metabolism, digestion, and DNA replication. They are highly specific and can be regulated to control the rate of reactions in cells. Other macromolecules like carbohydrates, lipids, and nucleic acids do not possess the same catalytic properties as enzymes.

In the structure of an amino acid, there are 20 different groups (B). This is because there are 20 different amino acids that make up proteins, each with a unique side chain or R group. These side chains can vary in size, shape, and chemical properties, which contribute to the diversity and functionality of proteins. Therefore, there are 20 different groups (B) in the structure of an amino acid.

The diagram shows a molecule of an amino acid, which consists of an amino group (-NH2) and a carboxyl group (-COOH). These are the functional groups in this molecule. Therefore, the correct answer is A and C, as option A represents the amino group and option C represents the carboxyl group.

ATP (adenosine triphosphate) can be used as short-term energy storage. ATP is a molecule that stores and releases energy in cells. It is commonly referred to as the "energy currency" of the cell because it provides the energy necessary for cellular processes. When ATP is broken down into ADP (adenosine diphosphate) and inorganic phosphate, energy is released, which can be used for various cellular activities. Carbohydrates, triglycerides, and proteins are also sources of energy, but ATP is specifically designed for short-term energy storage and transfer within cells.

Cytosine binds with guanine in a DNA molecule through a triple bond. This triple bond is formed between the nitrogenous bases of cytosine and guanine. The triple bond provides a strong and stable connection between the two bases, contributing to the stability and structure of the DNA molecule.

The G:C association would require the most energy to break because it is a stronger bond compared to the other options. G:C forms three hydrogen bonds, while A:T and A:U only form two hydrogen bonds. The additional hydrogen bond in G:C makes it more stable and harder to break, thus requiring more energy.

A tri-peptide consists of three amino acids joined together by two peptide bonds. Peptide bonds are formed when the carboxyl group of one amino acid reacts with the amino group of another amino acid, resulting in the formation of a peptide bond and the release of a water molecule. Therefore, a tri-peptide would have two peptide bonds connecting the three amino acids.

The complementary DNA strand is created by pairing each nucleotide with its complementary base. In this case, the template strand has the sequence 3’ T A C C G A T T G C A 5’. The complementary strand will have the same sequence but with the complementary bases. A pairs with T, T pairs with A, C pairs with G, and G pairs with C. Therefore, the complementary DNA strand is 5’ATGGCTAACGT 3’.

Albumin is a protein that is primarily found in the plasma of blood. It is the most abundant protein in the blood and plays a crucial role in maintaining the osmotic pressure and transporting various substances such as hormones, fatty acids, and drugs. Albumin also helps in the regulation of blood volume and pH balance. While plants do have proteins, albumin is not typically found in plant tissues such as roots or leaves. Similarly, while saliva also contains proteins, albumin is not a major component of saliva. Therefore, the correct answer is plasma of blood.

Proteins are macromolecules that perform a wide range of functions in the body. They are involved in digestion, as enzymes help break down food. They also play a role in the immune system, as antibodies help fight against pathogens. Additionally, proteins are responsible for transporting oxygen in the blood, as hemoglobin binds to oxygen molecules. However, proteins do not carry genetic information. Genetic information is carried by DNA, which is a nucleic acid.

The given molecule is most likely a carbohydrate because it is composed of carbon, hydrogen, and oxygen atoms in a ratio of 1:2:1. Carbohydrates are organic compounds that serve as a major source of energy for living organisms and are commonly found in foods such as sugars, starches, and fibers.

There are three different amino acids, and we need to form tripeptides without repeating any amino acid. This means we can choose any of the three amino acids for the first position, then we have two options left for the second position, and finally only one option for the third position. So, the total number of different tripeptides that can be formed is 3 * 2 * 1 = 6.

Glycogen can be used as intermediate-term energy storage because it is a polysaccharide that is synthesized and stored in the liver and muscles. When energy is needed, glycogen can be broken down into glucose, which can then be used for energy production. This process allows for a relatively quick release of energy when needed, making glycogen an ideal choice for intermediate-term energy storage.

The percentage of (C) in the double helix molecule can be determined by subtracting the percentages of (A) and (T) from 100%. Since the percentage of (A) is 10% and the percentage of (T) is 20%, the combined percentage of (A) and (T) is 30%. Subtracting this from 100% gives us 70%, which represents the combined percentage of (G) and (C). Since (G) and (C) are always present in equal amounts in DNA, the percentage of (C) in the double helix molecule is half of 70%, which is 35%.

The alkyl group is what gives an amino acid its uniqueness. Amino acids are made up of a central carbon atom that is bonded to four different groups: an amino group, a carboxyl group, a hydrogen atom, and an alkyl group. It is the specific arrangement and composition of the alkyl group that differentiates one amino acid from another. The alkyl group can vary in size and structure, which leads to the diversity of amino acids and their different properties and functions in biological systems.

Test tube A is identified as biuret on albumen because biuret test is used to detect the presence of proteins, and albumen is a protein. Test tube B is identified as benedict on glucose because benedict test is used to detect the presence of reducing sugars, and glucose is a reducing sugar. Test tube C is identified as iodine on starch because iodine test is used to detect the presence of starch, and starch gives a blue-black color with iodine. Test tube D is identified as sudan IV on palm oil because sudan IV test is used to detect the presence of lipids, and palm oil is a lipid.

During prolonged fasting, the body primarily relies on carbohydrates as its main source of energy. Once the carbohydrate stores are depleted, the body then starts breaking down fats to produce energy. Lastly, if the fasting continues for an extended period, the body starts breaking down proteins for energy. This sequence ensures that the body utilizes its energy sources in the most efficient manner, preserving proteins as much as possible.

A dipeptide molecule consists of two amino acids linked by a peptide bond. The peptide bond is formed between the carboxyl group of one amino acid and the amino group of the other amino acid. Therefore, there are not two free carboxylic groups and two free amino groups in a dipeptide molecule.

The number of triple hydrogen bonds found in a molecule of DNA is equal to the number of adenine-thymine pairs. Since the number of thymine bases is given as 150, it means there are 150 adenine bases as well. Each adenine-thymine pair forms two hydrogen bonds, so the total number of triple hydrogen bonds is 150 (adenine-thymine pairs) multiplied by 2 (hydrogen bonds per pair), which equals 300. Therefore, the correct answer is 300.

A molecule of DNA consists of two strands, each made up of a chain of nucleotides. Each nucleotide in DNA consists of a phosphate group, a sugar molecule, and a nitrogenous base. In a DNA molecule, there are two phosphate groups, one on each end of the double helix structure. Therefore, the number of free phosphate groups found in the molecule is 2.

The question asks for the maximum number of different polypeptide chains that can be formed from three similar amino acids. Since the amino acids are similar, there is only one possible arrangement of the three amino acids to form a chain. Therefore, the maximum number of different polypeptide chains that can be formed is one.

Amino acids combine to form specialized proteins in the body. Enzymes are proteins that act as catalysts in biochemical reactions. Hormones are chemical messengers that regulate various bodily functions. Ligaments are tough connective tissues that connect bones to each other and provide stability to joints. Therefore, enzymes, hormones, and ligaments are all structures that can be formed when amino acids combine into specialized proteins in the body.

The correct answer represents the backbone arrangement of peptide bonds as Cα-C-N-Cα-C-N. This arrangement shows the connection between the alpha carbon (Cα) and the nitrogen (N) atoms in the peptide bond, with the carbon (C) atoms in between. This arrangement is characteristic of the peptide backbone structure, where the amino group (NH2) and the carboxyl group (COOH) are attached to the alpha carbon.

Hydrogen bonds play a crucial role in protein structure by forming between amino acids to hold the protein in its secondary-structure shape. Secondary structure refers to the folding patterns of the protein, including alpha helices and beta sheets. These hydrogen bonds form between the amino acid backbone, specifically between the carbonyl oxygen of one amino acid and the amino hydrogen of another amino acid. This stabilizes the protein structure and helps maintain its overall shape. Hydrogen bonds between amino acids in the polypeptide chain and water molecules do not directly contribute to the secondary structure, and hydrogen bonds within amino acids do not hold the protein in its secondary structure shape.

DNA is composed of repeating units called nucleotides. These nucleotides consist of a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base. Therefore, the correct answer is deoxyribonucleotides, as they contain the deoxyribose sugar that is characteristic of DNA. Ribonucleosides and ribonucleotides contain a different sugar molecule (ribose) and are found in RNA, not DNA.

The primary structure of a protein refers to the sequence of amino acids in its polypeptide chain. This is the first level of protein structure and is determined by the specific order of amino acids in the chain. It is the primary structure that ultimately determines the protein's overall shape and function. The other options are incorrect because they describe other levels of protein structure, such as the 3D structure formed by interactions between multiple polypeptides or the additional bonds formed in the polypeptide chain.

The bond (X) in the diagram represents a phosphodiester bond. This type of bond is formed between the phosphate group of one nucleotide and the sugar group of another nucleotide in a nucleic acid molecule. It is a strong covalent bond that links the nucleotides together to form the backbone of DNA and RNA strands.