Niveditha

The human eye is a spherical, hollow, sensory organ specialized to receive light, focus it, convert it into electrical signals, and send those signals to the brain. Its structure can be understood by dividing it into three main layers and then looking at the structures inside.

OUTER LAYER (Protective Layer)

Cornea

The cornea is the transparent, curved front portion of the eye that allows light to enter. Its curvature bends (refracts) incoming light sharply, making it responsible for most of the eye’s focusing power. Because it has no blood vessels, it receives oxygen directly from the air and nutrients from the tear fluid.

Sclera

The sclera is the opaque, white, tough outer coat that maintains the shape of the eyeball and gives attachment points to eye muscles. It protects delicate inner tissues from injury and maintains internal pressure.

Introduction

Metabolism generally occurs by orderly, step-wise, sequence that are dependent on the basic laws of thermodynamics. These metabolic pathways consists of a series of progressive, individual chemical reactions.

A Single Step

A single step involves the conversion of a precursor (A) to a given product (B). This reaction is catalysed by a protein molecule, Ea, called an enzyme. An enzymatic reaction is reversible, the forward reaction is described by a rate constant, Kf, whereas the reverse reaction is described by Kr.

Numerous Step

Such a sequence may continue for numerous individual steps, so that the original substrate, A, is converted to the ultimate product, P. This is a typical liner metabolic pathway.

A dichotomous key is a tool used to identify organisms or objects by following a series of choices. The word “dichotomous” means “two parts,” so each step in the key gives two contrasting statements. You choose the statement that matches the organism you are trying to identify, and that choice leads you to the next step. By continuing this process, you eventually reach the name of the organism.

A dichotomous key works like a decision path. At each stage, you compare two features, such as “has wings” or “does not have wings.” These pairs of statements are based on observable characteristics like shape, size, colour, body parts, or behaviour. Because every step has only two options, it becomes easy to sort and identify even very similar organisms.

Scientists commonly use dichotomous keys in biology to identify plants, animals, fungi, or insects. Students also use them in labs, especially in classification topics.…

The skin is the largest organ of the human body, and it is made of three main layers: the epidermis, the dermis, and the hypodermis.

Epidermis

The epidermis is the outermost layer and works like a protective shield. It contains dead cells on the surface and new cells forming at the bottom. This layer also has melanocytes, which produce melanin, the pigment that gives the skin its colour and protects it from sunlight.

dermis

Below the epidermis lies the dermis, a thicker and stronger layer that supports and nourishes the skin. It contains hair follicles, sweat glands, oil glands, nerves, and blood vessels. Because of these structures, the dermis gives the skin strength, elasticity, and the ability to feel sensations like touch, pain, and temperature.

hypodermis

Definition

Metabolism is a set of life - sustaining chemical reactions that occur within living organisms. It is the sum total of all the chemical reactions that occur within the organism.

Functions

Each cellular sub-unit has specific, purposeful functions to perform in establishing and maintaining the life of the cell. However, all the cells have in common two major general functions : energy generation and energy utilisation. Metabolism is the process of turning food into energy. Metabolism is also known for the excretion of metabolic wastes.

Metabolic Pathways

The chemical reaction of metabolism are organised into metabolic pathways. There are hundreds of metabolic pathways. The 4 major metabolic pathways are of : Proteins, Carbohydrates, Fats, and Nucleic Acids - later.

Monera

Examples: Bacteria, blue-green algae (cyanobacteria)Key Features:

• Organisms are prokaryotic — no true nucleus or membrane-bound organelles.

• Usually unicellular (some form colonies).

• Reproduce asexually by binary fission.

• Nutrition can be autotrophic (photosynthetic/chemosynthetic) or heterotrophic.

An organism’s metabolism is the sum total of all the chemical reactions that occur within the organism. These chemical reactions fall into two basic categories:

• Anabolism: building polymers (large molecules that the cell needs).

• Catabolism: breaking down polymers to release energy.

This means that metabolism is composed of synthesis (anabolism) and degradation (catabolism).

It is important to know that the chemical reactions of metabolic pathways do not take place on their own. Each reaction step is facilitated, or catalyzed, by a protein called an enzyme. Enzymes are important for catalyzing all types of biological reactions—those that require energy as well as those that release energy.

Consider the metabolism of sugar (a carbohydrate). This is a classic example of one of the many cellular processes that use and produce energy. Living things consume sugars as a major energy source, because sugar molecules have a great deal of energy stored within their bonds. For the…

What are Anatomical Terminologies?

Anatomical terminologies are scientific words used to describe the location, position, and direction of body parts.They help in understanding how organs and structures are arranged in the body and make medical communication clear and precise.

Anatomical Position

The body is always described in the anatomical position, which means:

• Standing upright

• Facing forward

Introduction

Haemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. A healthy human has 12 to 20 grams of hemoglobin in every 100 mL of blood.

In mammals, hemoglobin makes up about 96% of a red blood cell's dry weight (excluding water), and around 35% of the total weight (including water). Hemoglobin has an oxygen-binding capacity of 1.34 mL of O2 per gram

The mammalian hemoglobin molecule can bind and transport up to four oxygen molecules. Hemoglobin also transports other gases. It carries off some of the body's respiratory carbon dioxide (about 20–25% of the total) as carbaminohemoglobin, in which CO2 binds to the heme protein. The molecule also carries the important regulatory molecule nitric oxide bound to a thiol group in the globin protein, releasing it at…

Introduction

The 2 types of sugars present in the nucleic acids - RNA and DNA - are Ribose (RNA) and Deoxyribose (DNA).

Structure

Deoxyribose is a Pentose sugar that has one less oxygen atom than Ribose. The chemical formula of Deoxyribose is C5H10O4 and the chemical formula of Ribose is C5H10O5. The molecular structure of 2 - deoxy - D - ribose is that is has a hydrogen at the second carbon rather than a hydroxyl group.

Why DNA has Deoxyribose and RNA has Ribose?

Introduction - MAIN

DNA's are polymers made up of monomers known as nucleotide. DNA has double helix structure since there are two strands of nucleotide.

Nucleotide

The 5 major nucleotide - Cytosine, Thymine, Uracil, Adenine, and Guanine - are categorised into 2 major categories, the purines [9 carbon] - Adenine and Guanine - and pyrimidines [5 carbon] - Cytosine, Thymine, and Uracil. Cytosine bond only with Guanine (Car on the Garage) and Adenine only bond with Thymine (Apple on the Tree) - In RNA, Adenine bonds only with Uracil. Since Thymine is energetically expensive to create (because of the methyl group), Uracil is used in RNA.

3 Major Parts of Nucleotide

The Nucleotide have 3 major parts - The Phosphate Group, The Pentose Sugar, and the nitrogenous base. The phosphate group is the backbone of the DNA, along with pentose sugar which helps as a bridge between phosphate group and…