Understanding Viruses: Composition, Types, and Cycles
Concept of Virus
Viruses are very simple, microscopic particles that consist only of a nucleic acid (viral genome) and some envelope proteins (capsid). Therefore, they are not cells and are not surrounded by membranes, forming acellular organizational systems. They exist on the boundary between the living and the nonliving.
Composition of Viruses
The composition of a virus is very simple, consisting of a single molecule of nucleic acid, which can be:
- Single-stranded RNA
- Double-stranded RNA
- Single-stranded
Biological Energy Processes and Genetic Variation
Biological Processes that Generate Energy
1. Photosynthesis: The process by which plants, algae, and some bacteria capture and utilize light energy to convert inorganic matter from their external environment into organic matter used for growth and development.
2. Chemosynthesis: The biological production of organic matter from molecules of carbon and other nutrients, using the oxidation of inorganic molecules.
3. Anaerobic Respiration: A biological process of oxidation-reduction of sugars and other
Read MoreSensory Receptors and Human Body Functions
Sensory Receptors and Their Functions
Sensory receptors are responsible for capturing information and relaying it to the nervous system. These receptors are activated when there are changes triggered by specific stimuli.
- Photoreceptors: Located in the eyes, they detect light stimuli.
- Mechanoreceptors: Stimulated by mechanical changes, pressure, contact, and sound waves.
- Chemoreceptors: Capture information about chemical changes. Taste and smell belong to this group.
- Thermoreceptors: Stimulated by temperature
Human Body Systems: Nutrition and Respiration
Devices Involved in Nutrition
The following systems are involved in human nutrition:
- Digestive system: Digests food and converts it into simpler substances.
- Respiratory system: Provides for the exchange of gases, providing O2 and clearing CO2.
- Circulatory system: Transports oxygen and usable food substances to different cells through the blood.
- Excretory system: Eliminates waste substances from the blood.
Digestive System
The digestive system includes:
- Intestinal tract: Made up of the mouth, esophagus,
Fundamental Concepts in Biology
Two Basic Types of Science
Science can be broadly categorized into two main types:
- Discovery Science: This type of science is primarily based on observation and data analysis. It involves describing the natural world through verifiable data.
- Example: Jane Goodall’s decades-long observation of chimpanzees in their natural habitat.
- Hypothesis-Driven Science: This approach involves formulating a tentative answer to a well-framed question (a hypothesis) and then testing predictions through experiments.
- Example:
Cellular Organelles: Structure and Function
Golgi Apparatus
Functions:
- Finalizes the protein glycosylation process underway in the Rough Endoplasmic Reticulum (RER). This process occurs sequentially from the cis face to the trans face of each dictyosome.
- Synthesizes glycolipids and sphingomyelins.
- Synthesizes complex polysaccharides of the cell wall in plant cells, which will be transported in vesicles for distribution and export.
- Directs proteins.
- Forms the acrosome in spermatozoa.
Chloroplast
Functions:
- Photosynthesis
- Fatty acid biosynthesis
- Reduction