The Cell Nucleus and Cell Cycle: Structure and Function
The Cell Nucleus
Nuclear Pores
In all nuclei, the two membranes forming the nuclear envelope fuse, giving rise to circular holes called nuclear pores.
These are aqueous channels that regulate the exchange of molecules between the nucleus and the cytosol. They allow free circulation and regulate water-soluble molecules as active transport mechanisms.
Chromatin
In the nucleus of eukaryotic cells, DNA is associated with proteins, forming a packed and compact structure called chromatin.
Features
Chromatin
Read MoreGenetic Engineering: Benefits, Risks, and Ethical Concerns
Genetic Engineering: A Double-Edged Sword
Introduction
Genetic engineering aims to eradicate debilitating diseases. While noble, this scientific field carries inherent risks. It has applications in medicine, agriculture, environmental science, and food production. Broadly defined, it encompasses any genetic manipulation enabling an organism to perform new functions or produce new substances. However, this technology has its critics. Just as it offers numerous advantages, there are also disadvantages
Read MoreMicrobiology of Bacteria, Fungi, and Viruses in Food
Bacteria
Bacteria are unicellular, prokaryotic organisms, ranging from 0.2 to 5 microns in size. Their genome consists of a single, large, circular, closed DNA molecule (nucleoid). The cytoplasm contains ribosomes and reserve products. Bacteria possess a plasma membrane and a bacterial wall made of peptidoglycan. The Gram stain differentiates bacteria into two groups: Gram-positive and Gram-negative, based on cell wall characteristics. Bacteria can harbor exogenous genetic material (plasmids and
Read MoreIntroduction to Cell Biology
Cytoskeleton
The cytoskeleton is dynamic, adaptable, and consists of three networks:
- Microtubules
- Microfilaments
- Intermediate Filaments
These three are ATP catalysts.
Microtubules
Composed of the protein tubulin, measuring 25 nm, microtubules form the mitotic spindle and are used in vesicle transport. They are found throughout the cell from the core to the membrane.
Unlike the other two components, microtubules have a channel in the middle. They are organized by proteins called MAPs (Microtubule-Associated
Read MoreProteins: Structure, Classification, and Functions
Proteins: An Overview
Proteins are essential biomolecules primarily composed of carbon, hydrogen, oxygen, and nitrogen. They may also contain sulfur, and some types contain phosphorus, iron, magnesium, copper, and other elements. Proteins are polymers of smaller molecules called amino acids, which are linked together by peptide bonds.
Amino Acids
Amino acids are characterized by a carboxyl group (-COOH) and an amino group (-NH2). The remaining two carbon valencies are saturated with a hydrogen atom
Read MoreThe Circulatory and Lymphatic Systems: A Comprehensive Guide
1. The Blood Circulatory System
Composition of Blood
The blood circulatory system consists of the heart (pump), blood, and blood vessels (tubes). Blood is contained within the vessels and never directly contacts cells, exchanging substances across thin capillary membranes.
Blood is composed of 55% plasma (a yellow liquid containing water, proteins, lipids, and carbohydrates) and 45% cells. These cells, produced in the bone marrow, are:
- Erythrocytes (red blood cells)
- Thrombocytes (platelets)
- Leukocytes