Fundamentals of Cell Biology and Human Organ Systems
Levels of Biological Organization
- Tissues
- Sets of specialized cells which have the same function and the same origin.
- Organs
- Structural and functional units of living beings.
- Organ Systems
- Sets of different organs which carry out functions that are independent from each other but coordinated.
- Organism
- The complete unit of the living organism.
Cell Structure and Organelles
- Cellular Membrane
- Consists of lipids and proteins. It surrounds the cell, separating it from its surroundings and allowing various substances to pass through to the cell from the exterior but restricting others.
- Cytoplasm
- The space existing between the cellular membrane and the nuclear envelope, where solid structures (organelles) are found.
- Nucleus
- Generally spherical in shape and confined by a nuclear envelope. This is a double membrane which has nuclear pores to allow substances to pass to and from the cytoplasm.
- Ribosomes
- Made up of proteins and RNA. Their function is to synthesize proteins.
- Endoplasmic Reticulum
- A set of membranes that form sacs and tubes, which are joined together with the cellular and nuclear membranes.
- Vacuoles
- Sacs which store substances.
- Lysosomes
- Store digestive substances which are transported to the vacuoles.
- Golgi Apparatus
- Consists of 5–10 flat sacs which produce glucose and store biomolecules.
- Vesicles
- Very small sacs which store and transport substances.
- Mitochondria
- Responsible for the respiration of the cell, a set of reactions by means of which the cell obtains energy.
- Chloroplast (Only in Plant Cells)
- Responsible for photosynthesis.
- Centrosome (Only in Animal Cells)
- Related to the movements of the cell and its organelles, and the shape of the cell.
- Cilia and Flagella
- These allow the cell to move. Found in bacteria and animal cells.
Cell Division: Mitosis
During mitosis, the DNA fibers are duplicated and packaged separately in bar-like structures called chromosomes.
Nutrition and Vital Functions
Nutrition allows living organisms to obtain the matter and energy they need for making their own matter and for carrying out their vital functions.
The Digestive System
The Digestive System is formed by the digestive tract and associated glands. It processes food to obtain water, proteins, fats, and sugars. This process is divided into three main parts:
- Digestion: Occurs in the mouth, the stomach, and the small intestine. It consists of the separation of usable substances from the foods.
- Absorption: Occurs in the small intestine. The usable substances pass into the bloodstream.
- Expulsion of Wastes: Occurs in the large intestine. Undigested remains and unusable substances are expelled.
Other Vital Organ Systems
Respiratory System
Formed by the respiratory paths and the lungs. It facilitates the exchange of gases in the alveoli, where the blood takes oxygen and releases carbon dioxide (CO₂).
Circulatory System
Formed by the heart and the blood vessels. It circulates the blood throughout the body. Its functions include:
- Transporting food substances, water, and oxygen from the digestive system to the cells.
- Collecting CO₂ and waste substances produced by the cells.
Excretory System
Formed by the kidneys and the urinary tracts. It is responsible for the elimination of waste substances transported in the blood, which may be toxic. The kidneys filter the blood and separate these substances, which are expelled in the urine. The sweat glands also participate in the excretion process by producing sweat.
Mechanics of Respiration
Inhalation
Air enters the lungs. The lungs swell, and the muscles related to respiration work to broaden the thoracic cage. The diaphragm contracts and descends, and the intercostal muscles tense, lifting the ribs.
Exhalation
Air leaves the lungs. The lungs relax, and the muscles cause the size of the thoracic cage to decrease. The diaphragm and the intercostal muscles relax, and the rectus abdominus muscles pull the ribs back.
Basic Food Groups
- Milk, milk derivatives, and eggs.
- Meat, poultry, and fish.
- Fats and oils.
- Cereals, pulses, potatoes, and sugars.
- Vegetables.
- Fruit.
Key Nutritional Definitions
- Calorie
- The amount of heat required to increase the temperature of one gram of water by one degree Centigrade.
- Nutrients
- Substances we need for obtaining energy and for making our own living matter.