Cellular Structures, Metabolism, and Reproduction Processes
Cellular Biology Fundamentals
Cell Types
Prokaryotic Cells
Single-celled organisms. They possess a cell wall and plasma membrane but lack a true nucleus. DNA is scattered throughout the cytoplasm, and they contain ribosomes.
Eukaryotic Cells
Have a true nucleus and organelles dispersed in the cytoplasm. They can be unicellular or multicellular.
Cellular Structures and Organelles
Cell Wall
Provides protection and form, primarily found in plant cells.Plasma Membrane
Regulates the entry and exit of substances into cells (found in plant and animal cells).Nucleus
Controls and directs the functions and division of cells (plant and animal).Cytoplasm
Contains cellular organelles and is the medium where metabolic reactions occur (plant and animal).Mitochondria
Produces energy for cells through cellular respiration (plant and animal).Golgi Apparatus
Processes and packages substances for the cell or the organism (plant and animal).Endoplasmic Reticulum
Involved in the synthesis and transport of proteins and lipids (plant and animal).Lysosomes
Perform cellular digestion (plant and animal).Centrosome or Centriole
Involved in the movement of cells and the distribution of chromosomes during cell division (animal cells only).Vacuoles
Store water and various substances (plant and animal).Chloroplasts
Carry out photosynthesis (plant cells only).Ribosomes
Site of protein synthesis (plant and animal).Fundamental Biological Processes
Nutrition
The process by which organisms obtain matter and energy. The stages include:
- Ingestion
- Digestion
- Absorption
- Egestion (removal of undigested waste)
- Excretion (removal of metabolic waste)
Types of Nutrition
Heterotrophic Nutrition
Food is obtained from outside sources; organisms must consume matter and energy from other media (e.g., animals).Autotrophic Nutrition
Organisms produce their own food (e.g., plants, algae).Metabolism
The sum of all chemical reactions that occur within a cell.
Catabolism
Decomposition of complex molecules into simpler ones (complex $\rightarrow$ simple). This process releases energy.Anabolism
Synthesis of complex molecules from simpler ones (simple $\rightarrow$ complex). This process consumes energy.Plant Energy Processes
Photosynthesis
Carried out by chloroplasts using chlorophyll. It uses light energy to convert inorganic matter into organic matter.
Chemical Equation:
CO₂ + H₂O + Light Energy $\rightarrow$ Glucose + O₂
Respiration
Occurs in the mitochondria, releasing chemical energy from glucose.
Chemical Equation:
Glucose + O₂ $\rightarrow$ CO₂ + H₂O + Chemical Energy
Cell Reproduction
Prokaryotic Cell Reproduction
Asexual reproduction, typically via Bipartition (simple division).
O $\rightarrow$ 8 $\rightarrow$ 0 0
Eukaryotic Cell Reproduction: Mitosis
The process of nuclear division, consisting of four main phases:
Prophase
Chromosomes condense (already duplicated) and the nuclear membrane begins to disappear.
Metaphase
Chromosomes align at the center (equator) of the cell.
Anaphase
The chromatids separate and are pulled toward opposite poles.
Telophase
Chromosomes decondense, the nuclear membrane reappears, and the cell divides (cytokinesis).
Note: Mitosis takes place in all somatic cells for growth and repair. Sex cells (gametes) are produced in the gonads via meiosis (a different division process).