Notes, summaries, assignments, exams, and problems for Biology

A biosensor is an analytical device containing immobilized biological material (enzymes, antibodies, nucleic acid, hormone) which specifically interact with an analyte and produce physical, chemical, or electrical signals that can be measured. An analyte is a compound (e.g., glucose, urea, drug, pesticide) whose concentration has to be measured.

Biosensors consist of two main components: a "sensing element" and "transducers."

• Sensing element: May be either enzymes, antibodies, DNA, tissues, or whole cells.
• Transducers: Convert a biochemical reaction or response into electrical signals.

The basic components of biosensors are: analyte (sample), sensing element, and transducer.

Principle of Biosensors

The analyte, on binding to the biological material,... Continue reading "Pharmaceutical Biotechnology and Recombinant DNA Technology" »

Vital Human Body Systems

The human body relies on several key systems to function effectively:

• Respiratory System: Obtains oxygen for cells and expels CO2.
• Digestive System: Allows food to enter the body, breaking it down into nutrients.
• Excretory System: Removes waste products from the body.
• Circulatory System: Transports nutrients and oxygen to the cells and removes waste.

The Digestive System and Tract

The digestive system allows food to enter the body and converts it into nutrients, which are then absorbed into the blood. The digestive tract is a tube eight meters long. It has an inner layer of cells called the mucosa. Layers of muscle surround this tube; when these layers contract, they push food down.

The Mouth and Dental Structure

In the mouth,... Continue reading "Human Body Systems and Digestive Anatomy" »

1. Evidence of Earth's Ancient Non-Living Systems and Evolution

• Geosphere:
  • Oldest crust: Acasta Gneiss (4.04 Ga); Zircon crystals in Jack Hills Conglomerate (4.4 Ga).
  • Plate tectonics likely began ~3.2 Ga, evidenced by diamond inclusions transitioning from peridotite to eclogite.
• Atmosphere:
  • Initial gases (Hydrogen, Helium) lost to solar winds; later volcanic outgassing formed a CO₂ and water-rich atmosphere.
  • Oxygen appeared ~2.3 Ga due to cyanobacteria, evidenced by oxidized minerals (Banded Iron Formations).
• Hydrosphere:
  • Water sources: Asteroids (carbonaceous chondrites) and volcanic outgassing.
  • Oceans formed as Earth cooled and water vapor condensed.

2. Definition of Life and Origin of Components

• Definition: Life is distinguished by:
  • Barrier-separated

... Continue reading "The Dawn of Life: Early Earth Systems and Abiogenesis" »

Sickle Cell Anaemia and Malaria Resistance

Sickle cell anaemia is a genetic mutation in humans characterized by a disorder in the amino acid sequence of the haemoglobin molecule. This results in red blood cells taking on a sickle shape. Malaria is caused by a parasite that thrives in red blood cells; consequently, individuals with sickle-shaped cells possess immunity to malaria. This explains why the condition is more prevalent in tropical regions where malaria is common. However, individuals with sickle cell anaemia typically have a significantly shorter life expectancy.

Artificial and Natural Selection

Artificial selection is utilized to produce varieties of animals and plants with increased economic importance.

Defining Natural Selection

Natural

... Continue reading "Genetic Inheritance, Natural Selection, and Hormonal Regulation" »

Cellular and Structural Organization

Eukaryotic Cell

An organism or cell that possesses a clearly defined nucleus.

Prokaryote

A single-celled organism lacking a nucleus and membrane-bound organelles (e.g., bacteria).

Organism

Any living thing.

Cell

The smallest basic unit of life responsible for all life processes.

Tissue

An aggregate of cells in an organism that have similar structure and function.

Organs

A collection of tissues that structurally form a functional unit specialized to perform a particular function.

Organ System

A biological system consisting of a group of organs that work together to perform one or more functions.

Key Cellular Components and Specialized Functions

• Ribosome

  The site where protein synthesis occurs.

• Mitochondria

  The site where

... Continue reading "Fundamental Concepts in Cellular Biology and Life Processes" »

Primary Functions of Human Blood

Blood performs several critical roles in the body:

• Transport: Nutrients, oxygen, carbon dioxide, and hormones.
• Immune Defense: Protecting against toxins and pathogens.
• Waste Elimination: Removing metabolic waste products.
• Homeostasis: Controlling pH levels and ion concentrations.
• Fluid Regulation: Restricting fluid loss at injury sites.
• Temperature Regulation: Maintaining stable body temperature.

Blood Composition and Volume

Blood consists of plasma (46–63%) and formed elements (37–54%).

• Plasma: Composed of water (92%), plasma proteins (7%), and other solutes (1%).
• Formed Elements: Composed of red blood cells (99.9%), white blood cells (0.1%), and platelets (0.1%).

Blood Volume:

• Males: 5–6 liters (approximately 46%

... Continue reading "Blood Composition and Hematology Essentials" »

Somite Development and Function

Somites are paired blocks of paraxial mesoderm that form sequentially on either side of the neural tube during early embryonic development. They begin forming near Hensen’s node and continue caudally as the embryo elongates.

Somite Differentiation

Each somite differentiates into three main structures:

• Dermatome → forms the dermis of the skin.
• Myotome → forms skeletal muscles of the body and limbs.
• Sclerotome → forms vertebrae and ribs.

Chronology of Development

The number of somite pairs is a reliable morphological indicator of embryonic age. In chick embryos, somite formation begins around 18 hours of incubation. By 24 hours, approximately 4 pairs are visible.

New somite pairs appear at regular intervals (~every... Continue reading "Human Embryonic Development: Placental and Somite Formation" »

Two-Compartment IV Bolus Model

The two-compartment intravenous (IV) bolus model describes the kinetics of drugs that do not distribute instantaneously throughout the body. Following rapid IV injection, drugs distribute quickly into a central compartment (blood/well-perfused tissues) and slowly into a peripheral compartment (tissues), displaying a biexponential plasma concentration decline over time.

Compartment Definitions

• Central Compartment (V_c): Blood and highly perfused tissues (liver, kidneys, heart). Elimination mainly occurs here.
• Peripheral Compartment (V_p): Poorly perfused or slowly equilibrated tissues (muscles, adipose, skin).

Biexponential Decline

The plasma level-time plot is not a straight line on a semi-log scale; it shows a rapid... Continue reading "Two-Compartment vs. One-Compartment IV Bolus Pharmacokinetics" »

1. Introduction

Tissue culture is the in vitro aseptic culture of cells, tissues, organs or whole plant under controlled nutritional and environmental conditions [1] often to produce the clones of plants. The resultant clones are true-to type of the selected genotype. The controlled conditions provide the culture an environment conducive for their growth and multiplication. These conditions include proper supply of nutrients, pH medium, adequate temperature and proper gaseous and liquid environment.

Plant tissue culture technology is being widely used for large scale plant multiplication. Apart from their use as a tool of research, plant tissue culture techniques have in recent years, become of major industrial importance in the area of plant... Continue reading "Ikokok" »

pBR322 was the first artificial cloning vector created in the laboratory by Francisco Bolivar and Raymond L. Rodriguez. Compared to its pUC counterparts, pBR322 is larger in size, resulting in a slower rate of replication. This E. coli cloning vector contains an origin of replication (ori), restriction sites, and antibiotic-resistant genes.

pBR322 is a widely used cloning vector in E. coli with significant applications in molecular cloning.

pBR322 Nomenclature

• p: Plasmid
• BR: Bolivar and Rodriguez
• 322: Numerical designation

Constructed in 1977 in the laboratory of Herbert Boyer at the University of California, San Francisco, it was the first synthetic plasmid designed for use as a cloning vector. As one of the most studied plasmids, it is 4,362 base... Continue reading "pBR322: The First Artificial Cloning Vector" »