Bioelements and Biomolecules: Composition and Properties of Living Matter
Bioelements
Bioelements are the chemical elements that constitute living matter.
- Primary (95%): C, H, O, N
- Secondary (4.5%): P, S, Ca, Na, K, Mg, Cl
- Trace (0.5%): Mn, Cu, Zn, Fe
Biomolecules
- Inorganic: Water and mineral salts
- Organic: Carbohydrates, lipids, proteins, nucleic acids, biocatalysts (enzymes, vitamins, and hormones)
Water
Characteristics
Water is formed by two hydrogen atoms and one oxygen atom, linked by single covalent bonds. It is electrically neutral. Water molecules can interact with each
Read MoreCirculatory Systems in Animals: Open, Closed, and Double Circulation
Open and Closed Circulatory Systems
Open Circulatory System
In an open circulatory system, the heart pumps fluid (hemolymph) through open-ended vessels that lead to tissues and body cavities, directly bathing the cells. Molluscs (except cephalopods) exemplify this system. Cephalopods have a compartmentalized heart with one ventricle and one or two atria, enclosed within a pericardial cavity. Arthropods possess a tubular heart, a thickened dorsal vessel. Hemolymph is pumped from the heart into arteries,
Read MoreSensory Systems and Musculoskeletal Anatomy
Sensory Receptors
Sensory receptors are specialized nerve cells that capture stimuli and convert them into nerve impulses. Different types of receptors respond to various stimuli:
- Chemoreceptors: Sensitive to chemical changes.
- Mechanoreceptors: Sensitive to mechanical stimuli like friction and pressure.
- Photoreceptors: Sensitive to light.
- Thermoreceptors: Sensitive to temperature changes.
- Nociceptors: Sensitive to intense pressure, responsible for pain.
Based on their location, receptors are classified
Read MoreCell Theory: Structure, Function, and Evolution of Cells
Cell Theory
All living organisms are composed of cells. The cell is the structural and physiological unit of living things, where metabolic processes occur. Cells contain hereditary information, passed from mother to daughter cells.
Comparison: Prokaryotes vs. Eukaryotes
Prokaryotes
- Typical of small cells (e.g., monera)
- No defined nucleus
- No cell envelope; may have a capsule
- Genetic material is circular DNA; no mitosis
- Lack cytoskeleton and most organelles
- Small ribosomes
- Cell wall usually present
Eukaryotes
- Typical
Human Nervous, Musculoskeletal, and Endocrine Systems
In vertebrates, the NERVOUS SYSTEM consists of:
Nervous Centers
- Brain and spinal cord. Responsible for receiving, processing, and developing responses to sensory information.
Nerve Fibers
- These are the axons of neurons. Responsible for getting sensory stimuli to the nerve centers and transmitting responses of the motor fibers.
Nerves
- Made by the union of nerve fibers.
Nodal Masses
- Clusters of neuronal bodies located along some nerve pathways.
Central Nervous System (CNS)
The CNS is constituted from a large
Read MoreInvertebrate Biology: Annelids, Mollusks, Arthropods
Leaf Structure
Plants faced dehydration when transitioning to land. Photosynthesis requires light and CO2. Leaf structure adapted to solve this. Angiosperm leaves have architectural adaptations to avoid desiccation. Upper and lower surfaces are covered with transparent epidermal cells coated with a waxy cuticle, reducing water loss. Between is the mesophyll, including palisade cells (columnar, below upper epidermis) for photosynthesis. Lacunar mesophyll (loosely arranged cells with spaces) also aids
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