Notes, summaries, assignments, exams, and problems for Biology

SPERMATOZOA 

Receptors

Internal receptors perceive changes inside the body, such as a rise in blood pressure. External receptors perceive stimuli in the external environment.

Types of Receptors

• Mechanoreceptors: Perceive mechanical stimuli (pressure).
• Thermoreceptors: Perceive changes in temperature.
• Chemoreceptors: Detect chemical substances in the air, water, etc.
• Nociceptors: Perceive pain stimuli.
• Photoreceptors: Light sensitive.

Nervous System

The nervous system analyzes internal and external stimuli perceived by receptors, generating responses. It carries out this function through nerve impulses transmitted by cells called neurons. This system coordinates fast, short-lived responses (e.g., muscle contraction).

Endocrine System

The endocrine system is made up... Continue reading "Sensory Systems and Nervous Coordination" »

Sensory receptors are responsible for perceiving infortion, which they convert into a nerve impulse. The nerve impulse travels to the brain and produces a feeling.

Antioxidants and Exercise

Key antioxidants include Vitamin C, Vitamin E, Carotenoids, Glutathione (GSH), and Coenzyme Q10 (Q10).

Enzymatic Antioxidant Systems

• Superoxide Dismutase (SOD)
• Catalase
• Glutathione Peroxidase

Functions of Antioxidants

• Neutralize free radicals by donating electrons (e-) and hydrogen ions (H+).
• Decrease lipid peroxidation both at rest and after exercise.
• Note: Supplementation may not necessarily decrease overall oxidative stress markers.
• Note: Vitamin E supplementation does not appear to decrease neutrophil count after exercise.

Benefits and Roles of Oxidative Species

• Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) are important for cellular development, function, and as stimuli (cellular messaging) – involved

Two Main Circuits of the Cardiovascular System

Pulmonary Circulation

Pulmonary circulation refers to the circulation of blood in which deoxygenated blood is pumped from the heart to the lungs and oxygenated blood is returned back to the heart. Pulmonary circulation only occurs between the heart and the lungs.

Systemic Circulation

Systemic circulation refers to the circulation of blood in which oxygenated blood is pumped from the heart to the body and deoxygenated blood is returned back to the heart. Systemic circulation occurs between the heart and the entire body.

Pericardial Sac

The pericardial sac is the outermost layer of the heart. It surrounds the heart and protects it.

Heart Valves

Atrioventricular (AV) Valves

The AV valves prevent backflow into... Continue reading "The Cardiovascular System: Pulmonary and Systemic Circulation" »

The Endocrine System

The endocrine system is a set of organs and tissues responsible for secreting hormones. It is distributed throughout the body, similar to the nervous system. However, the endocrine system uses chemical substances instead of nerve impulses.

Types of Hormones and Glands

• Pituitary: Located in the head.
  • Growth hormone: Stimulates the growth of all body tissues, especially the skeleton.
  • Thyroid-stimulating hormone: Regulates the production of thyroid hormones.
• Testes: Male gonads.
  • Testosterone: Stimulates the production of sperm and the development of secondary sexual characteristics.
• Thyroid: Located in the neck, in front of the trachea.
  • T3 and T4: Increase cell metabolism, oxygen consumption, protein synthesis, and glucose utilization.

Golgi Apparatus Functions

• Packaging, modification, and distribution of materials synthesized in the cell.
• Pathway: Rough ER (cis) → Cisternae → Vesicles (trans).

Cellular Protein Export Pathway

After proteins are synthesized by ribosomes, they are transported to the rough endoplasmic reticulum where they can be modified. Vesicles carrying the protein then bud off the rough endoplasmic reticulum and are transported to the Golgi apparatus for further modification. Following this, vesicles carrying the protein bud off the Golgi apparatus and transport the protein to the plasma membrane. Here, the vesicles fuse with the membrane, expelling their content (the modified proteins) outside the cell. The membrane then returns to its original state. This... Continue reading "Cellular Processes Explained: Division, Transport, and Key Structures" »

Spontaneous Generation

Spontaneous generation proposes that life began from inanimate objects.

Oparin's Theory

Alexander Ivanovich Oparin developed this abiogenic theory.

1. Components of the atmosphere (methane, ammonia, hydrogen, and water vapor) reacted due to the energy of storms, solar radiation, and continuous volcanic eruptions, creating simple organic molecules.
2. The Earth cooled down, and intense rain produced primitive seas where organic molecules accumulated.
3. Organic molecules joined, creating bigger molecules; some of them were insulated from the water inside structures called coacervates.
4. Some of the coacervates developed molecules in their interior that were able to self-replicate; these were the first organisms and the origin of all cells.

Yeast

Yeast is an unicellular saprophytic fungus present in the air and on the surface of fruit. Yeast causes the spoilage of fruit, jam, honey, and is used in the production of bread, beer, and wine. It feeds on carbohydrate foods, flourishes at 25C-30C, is killed above 60C, requires moisture for growth, can live with or without oxygen, and requires time to grow. It reproduces asexually through budding, where a cell develops a bud, the nucleus moves towards the bud, the nucleus divides in two, a wall develops and divides the bud from the parent cell, and the bud separates from the cell. Yeast has granular cytoplasm, food vacuoles, vacuole, and a cell wall.

Food Preservation

Food preservation involves long term storage, preventing enzyme activity... Continue reading "Food Preservation Methods and Microbial Growth" »