Comparative Biology of Transport Systems in Plants and Animals
Transport in Organisms: Fundamentals
In unicellular and simple multicellular organisms, nutrient uptake and waste removal occur primarily via passive transport mechanisms such as diffusion, osmosis, and facilitated diffusion across the external membrane, facilitated by their small size and high surface area-to-volume ratio.
In complex multicellular organisms, diffusion alone is insufficient to meet metabolic demands due to increased cellular volume and distance. Thus, specialized transport systems
The Human Fertilization Process: From Gamete to Zygote
The Intricate Process of Human Fertilization
Initial Contact and Penetration
The process of fertilization begins with the contact between gametes. This meeting typically occurs in the ampullary region of the fallopian tubes within the female genital tract. First, the sperm must penetrate the corona radiata of the secondary oocyte to reach and make contact with the zona pellucida.
The Acrosome Reaction: Unlocking the Egg
This contact triggers the acrosome reaction in the sperm’s head, releasing enzymes
Read MoreAuxin and Ethylene: Regulators of Plant Growth and Signaling
Phytohormones: Definition and Signaling Principles
What is a Phytohormone?
A phytohormone is a naturally occurring organic molecule produced in plants that acts at low concentrations to regulate growth, development, and responses to environmental stimuli.
- They are signal molecules that coordinate physiological processes such as cell division, elongation, differentiation, flowering, and stress responses.
- Examples include auxins, cytokinins, gibberellins, abscisic acid (ABA), ethylene, brassinosteroids,
Plant Cell Signaling Pathways: Hormones and Environmental Cues
Plant Cell Signaling Fundamentals
Cell signaling in plants is a crucial process that allows cells to perceive environmental and endogenous cues, transmit this information, and trigger appropriate responses. The main stages of cell signaling are signal perception, signal transduction (including amplification and second messengers), and cellular response. Additionally, feedback regulation ensures fine control of signaling pathways.
Stages of Plant Cell Signaling
1. Signal Perception (Reception)
Stimuli
Read MoreAnimal Gas Exchange: Lungs, Gills, and Tracheal Systems
The Purpose of Gas Exchange in Animals
Gas exchange is the vital process where oxygen (O₂) is taken into an animal’s body and carbon dioxide (CO₂) is removed. Oxygen is essential for aerobic respiration, a cellular process that generates energy in the form of ATP. This energy fuels all life processes, including movement, growth, and maintaining body temperature. Carbon dioxide, a waste product of this process, must be removed as it can become toxic if it accumulates. All animals perform gas exchange,
Read MoreMicrobial Genetics, Ecology, and Immunity Fundamentals
Chapter 13 – Bacterial Genome Replication and Expression
Discovery of Genetic Material
- Griffith’s experiment: Showed that non-virulent bacteria could transform into virulent forms by taking up DNA from dead virulent cells. Proved DNA is the genetic material.
- Hershey and Chase Experiment: Used radioactive labeling (P for DNA, S for protein) to show that only DNA enters bacterial cells during phage infection. Proved DNA is the genetic material.
Nucleic Acid Structure
- Structure of DNA: Double helix