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

archaea, extremophiles, cyanobacteria, bacteria.

Understanding Digestion: Mechanical & Chemical Processes

Digestion is the complex process by which food is broken down into nutrients the body can use. It involves both mechanical and chemical actions.

Mechanical Digestion

Mechanical digestion is the physical act of breaking down food by non-chemical means. This process begins in the mouth with chewing. The food is then manipulated by the tongue and cheeks to mix with saliva, forming a soft ball called a bolus. While the original text mentions the small intestine and defecation here, these are later stages of the overall digestive process, not specifically mechanical digestion in the initial stages.

Chemical Digestion

Chemical digestion involves breaking down food into simpler nutrients that... Continue reading "Human Body Systems: Digestion, Respiration & Key Organs" »

Challenges in Cartilage Repair

Chondral defects represent a challenging clinical problem, aggravated by the increase in the elderly population in developed countries. Consequently, many strategies—including arthroplasty, the stimulation of reparative tissues through arthroscopic abrasion, drilling, or microfracture¹—have been developed to treat injured cartilage. However, these procedures cannot successfully reproduce the tissue characteristics of hyaline cartilage^{2, 3}.

New biologically based strategies, such as the replacement of damaged surfaces with healthy tissue (osteochondral grafts)⁴ or the implantation of cultured expanded autologous chondrocytes, have been used for cartilage repair⁵. Nevertheless, the difficulty in obtaining sufficient... Continue reading "Chondrogenic Differentiation of Adipose-Derived Stem Cells" »

Key Characteristics of Birds

Birds are terrestrial vertebrates with feathered bodies. They are descended from reptiles, but they are considered to be more evolved as they have a more developed nervous system. Some of their main characteristics are the following:

• They have a fusiform or spindle-shaped body which is covered by feathers, except the legs which are covered by scales.
• Two of their limbs are wings, which in the majority of cases allow them to fly.
• They have a beak, but no teeth.
• They have a highly developed sense of sight.
• They are homeotherm or warm-blooded animals, which means that their internal temperature stays at around 42 ºC regardless of the temperature around them.

The Body of Birds

The body of birds has a very characteristic shape... Continue reading "Fascinating Biology and Anatomy of Birds" »

DNA is the molecule that gives cells and organisms their biological characteristics. Types of Nucleotides: Adenine, Cytosine, Thymine, Guanine. DNA/RNA: DNA has a double helix structure, while RNA does not. In DNA, thymine is present, whereas in RNA, uracil is present. RNA can exit the nucleus, but DNA cannot. Ribose Nucleotide does not contain thymine. Transcription is the process of copying a part of the genetic message from DNA to RNA. Translation is the process in which RNA moves from the nucleus to the cytoplasm. Genetic Code refers to the relationship between the sequence of nitrogenous bases in DNA and the sequences of amino acids that form proteins. Transcription occurs in the nucleus, while translation occurs in the cytoplasm. In prokaryotic... Continue reading "DNA and Genetic Engineering: A Comprehensive Overview" »

Peripheral Nervous System

Consists of nerves and supports it collects info about the body's external and internal environment.

Central Nervous System

Consists of the brain and spinal cord, processes info, and creates a response.

Cell Body

The largest part of the typical neuron.

Dendrites

Short branched extensions that receive impulses from other neurons and carry them to the cell body.

Axon

Long fiber that carries impulses away from the cell body.

Myelin Sheath

Insulating membrane that surrounds a single, long axon.

Resting Potential

Electrical charge across the cell membrane of a resting neuron.

Action Potential

A nerve impulse that charges more negatively charged to more positively charged.

Threshold

The minimum level of a stimulus that is required to cause... Continue reading "Understanding the Nervous System and Sensory Organs" »

Elastic Fibers

Elastic fibers maintain the position of alveoli and bronchioles. When fibers recoil during exhalation, they reduce the size of alveoli and push air out.

Pneumocyte Type I

Pneumocyte type I cells are squamous epithelial cells that are unusually thin, providing an ideal site for gas diffusion.

Pneumocyte Type II

Pneumocyte type II cells are scattered among the squamous cells and produce surfactant.

Breathing

Deep breathing, also known as diaphragmatic breathing, involves the contraction of the diaphragm to change the volume of the lungs, allowing air to be exhaled passively. Shallow breathing, or costal breathing, occurs when the rib cage alters its shape, changing the thoracic volume.

Dalton's Law

Dalton's Law states that the partial pressure... Continue reading "Elastic Fibers and Gas Exchange in the Respiratory System" »

Unit 1: Cellular Metabolism and Cell Types

Catabolism and Anabolism

Catabolism refers to all chemical reactions where substances are broken down into simpler ones, releasing energy.

• Cellular respiration: C₆H₁₂O₆ + 6O₂ (glucose) → 6CO₂ + 6H₂O + Energy (ATP)

Anabolism refers to all the chemical reactions where simple substances are joined together to form more complex ones.

• Photosynthesis: H₂O + CO₂ + Sunlight → C₆H₁₂O₆ + 6O₂

Heterotrophic Nutrition

Heterotrophic nutrition: Heterotrophic organisms cannot synthesize organic compounds from inorganic compounds. They incorporate organic matter which has been made by other organisms.

1. Some glucose molecules are used in cellular respiration and others are used in other processes.
2. Cellular respiration takes

Respiratory System: Nutrients and O2

The respiratory system captures oxygen from the air and transfers it into the blood. Cells use oxygen and nutrients to produce energy. Blood removes carbon dioxide (CO2), which is expelled from the body along with water vapor.

Respiratory system function: Gas exchange with the atmosphere.

Nasal Cavity

The nasal cavity is divided into two chambers. Each chamber has an external opening (nostril) and an internal opening to the pharynx (choana). A partition called the nasal septum separates the chambers. The nasal cavity is the entry point for air.

Characteristics

• Abundant capillaries with circulating blood.
• Abundant nooks that allow the air to travel further and remain inside longer, heating the air.
• Internally covered