Biology

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TISSUE

Tissue is defined as

An aggregation of structurally and functionally identical cells along with their extracellular material, acting in synergy to perform a specific function.

STUDY OF TISSUE

The study of tissues falls under two branches which are as follows;

HISTOLOGY

Histology is the branch of anatomy in which we study the structure and functions of tissues.

HISTOPATHOLOGY

Histopathology is a diagnostic branch of pathology in which we study tissues in light of various diseases.

Reading Time: 8 minutes

MITOSIS

DEFINITION

Mitosis is a type of cell division in which a cell divides into two daughter cells, each with the same number of chromosomes as were present in parent cell.

BACKGROUND

In 1880s a German biologist Walther Fleming observed that in a dividing cell, nucleus passes through a series of changes which he called mitosis.

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THE CELL CYCLE

• The cell cycle is the regular sequence of events that takes place between one cell division and the next.
• Cell cycle consists of two major phases namely

1. Interphase

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INTRODUCTION

• The functional specificity of every enzyme is the consequence of its specific chemistry and configuration.
• Any factor that can alter the chemistry and shape of an enzyme can affect the rate of catalysis.
• Some of the important factors that can affect the rate of enzyme action are as follows;

ENZYME CONCENTRATION

• The rate of reaction depends directly on the concentration of enzyme present at a specific time at unlimited substrate concentration.
• If the concentration of enzymes is increased by two-folds, the reaction rate is doubled.

EXPLANATION

• By increasing the concentration of enzyme molecules, an increase in the number of active sites take place.

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INTROUCTION

Enzymes are globular proteins acting as biological catalysts that increase the rate of various reactions occurring within the biological system.

CHARACTERISTICS OF ENZYMES

Enzymes, the biochemical catalysts, possess the following characteristics

• All enzymes are globular proteins.
• Enzymes catalyse reactions by lowering the activation energy and itself do not get involved in the reaction.
• Their presence does not affect the nature or properties of end products.
• Enzymes are very specific in their action; a single enzyme catalyse only a single chemical reaction or a group of related reactions.

OCCURRENCE OF ENZYMES

• Enzymes may be intra-cellular or extracellular.
• Enzymes which operate within the cell are known as intra-cellular enzyme.

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DEFINITION

Nucleic acids are polymers resulting from the linkage of smaller units called nucleotides.

BACKGROUND:

Nucleic acids were first isolated in 1869, by Fredrich Miescher from the nuclei of pus cells.

NUCLEOTIDES:

Nucleotides are small molecules acting as monomers and join together into a chain forming nucleic acids. Nucleic acids are therefore also known as polynucleotides.

COMPONENTS OF NUCLEOTIDE:

A nucleotide is composed of three components namely

1. Nitrogen containing base
2. Pentose sugar (5 carbon monosaccharide)
3. Phosphate group

NITROGENOUS BASE:

• The nitrogenous bases found in nucleotides (and hence nucleic acids) are heterocyclic compounds.

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INTROUCTION

Lipids are heterogenous group of organic compounds that are relatively insoluble in water and soluble in organic solvents, actually or potentially related to fatty acids and utilized by the living cells

CHEMICAL COMPOSITION

chemically, lipids are esters of fatty acids with alcohol

FATTY ACIDS:

• Fatty acids are carboxylic acids with a hydrocarbon side chain.

Fatty acids are of two types

1. When there is no double bond present in the hydrocarbon chain of fatty acids, these fatty acids are termed as saturated fatty acids

1. When the hydrocarbon side chain of fatty acids contains double bonds, such fatty acids are termed as unsaturated fatty acids.

ALCOHOLS:

Alcohols are a group of organic compounds containing on or more hydroxyl groups attached to a carbon atom.

Reading Time: 7 minutes

INTRODUCTION

Proteins are polymers of amino acids and are the most abundant organic molecules of the living system constituting about 50% of the cellular dry weight.

AMINO ACIDS:

Amino acids are organic compounds containing two functional groups i.e. amino (-NH₂) group and carboxyl (-COOH) group along with a side chain specific to each amino acid.

STRUCTURE OF AMINO ACIDS:

Chemically, an amino acid consists of four components

1. Carboxylic group (-COOH), which is basic in nature.
2. Amino group (-NH₂), which is acidic in nature.
3. R side chain which is specific for each amino acid and accounts for the different types of amino acids.
4. Hydrogen atom linked to the central carbon atom.

If both the carboxyl group and amino groups are attached to the same carbon, the amino acid is termed as α amino acid.

• There are almost 400 identified amino acids occurring in nature however, only 20 are involved in protein formation in living organisms.
• These 20 proteins arrange in various combinations to produce different types of proteins in living organism.

PEPTIDE LINKAGE:

The adjacent amino acids in a polypeptide protein chain are linked together via peptide bonds.

Reading Time: 6 minutes A carbohydrate is either sugar or polymer of sugars consisting of carbon, hydrogen, and oxygen.

DEFINITION:

Carbohydrates are polyhydroxy aldehydes or ketones or compounds which yield them upon hydrolysis

EMPIRICAL FORMULA:

The empirical formula for carbohydrates is C_m(H₂O)_n.

BACKGROUND:

• The term carbohydrates literally mean “hydrates of carbon”.
• This name was assigned because, in most of the carbohydrates, the ratio of hydrogen and oxygen is the same as water (2:1).
• However, there are several non-carbohydrate compounds that appear to be hydrates of carbon i.e. Acetic Acid (C₂H₄O₂).
• Further, some carbohydrates do not satisfy the empirical formula such as rhamnohexose (C₆H₁₂H₅).
• Therefore, carbohydrates cannot always be regarded as hydrates of carbon.

Reading Time: 3 minutes

INTRODUCTION

• Water is the medium of life and is the most abundant compound in all organisms.
• It is the most important component of the cell, typically forming between 70% to 95% of the mass of the cell.
• Almost all reactions of the cell occur in the presence of water, taking part in various biochemical processes such as hydrolysis of macromolecules.

The following are some important properties of water holding biochemical significance.

WATER AS A SOLVENT:

• Due to the polar nature of water, it acts as an excellent solvent for polar molecules and ions

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