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

Metabolic Pathways

Metabolic pathways consist of chains and cycles of enzyme-catalyzed reactions. Chemical reactions occur in a sequence of small steps. Some form a chain, while others form a cycle where the end product is the reactant that starts the pathway. These are categorized as:

• Anabolic pathways: Build up molecules.
• Catabolic pathways: Break down molecules.

Functions of Membrane Proteins

• Hormone binding sites: For example, insulin.
• Immobilized enzymes: With the active site on the outside (e.g., small intestine).
• Cell adhesion: To form tight junctions between groups of cells in tissues and organs.
• Cell-to-cell communication.
• Channels for passive transport: Allow hydrophilic particles across via facilitated diffusion.
• Pumps: Proteins for active

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" »

Moss Theory and 2 Examples

• Growth of face happens as response to functional needs and neurotrophic influences and is mediated via soft tissues in which jaws are embedded.
• Soft tissue growth causes both bone and cartilage to react.
• Growth of cranial vault is a direct response to growth of brain.
• Growth of eyes increases size of orbit.
• Major determinant of growth of maxilla and mandible is enlargement of nasal and oral cavities, which grow in response to functional needs. Important for orthodontic treatment with functional appliances and orthopedic treatment.

Endocrine System Regulation

How is the endocrine system regulated? Endocrine gland activity is regulated by the brain. The brain manages the endocrine system through two glands: the hypothalamus and the pituitary glands. The hypothalamus directs, and the pituitary glands produce and secrete.

Neuron Structure and Classification

Neurons: These transmit messages (nerve impulses) and have a unique appearance.

• Cell body: This is where the nucleus is located; it contains most of the cytoplasm and organelles. It forms part of the grey matter.
• Dendrites: These are branched projections connected to other neurons that receive information from them.
• Axon: A long tail structure where information passes from here to the next neuron or cell. A group of axons is

In Situ Tests: Parameters, Methods, Limitations

In situ tests: Values of different parameters are obtained from theoretical interpretation of the test result. Compared with laboratory tests, in situ tests reduce some limitations such as:

• Disturbance of soil samples (matters less; no transport of the sample).
• Change in the stress state of the sample.
• Small size of laboratory samples may be unrepresentative (a larger portion of the soil is involved).

Other limitations appear:

• Some disturbance is always present.
• Less control over test conditions (in the laboratory we can control water conditions).
• If the parameters of the theoretical model are two or more, only a relationship between them is obtained (for example, E and ν, or c and φ).

Common In Situ

The Ubiquitin Proteasome System and Protein Degradation

Ubiquitin (Ub) serves as a critical marker for protein breakdown. Before a protein is degraded, it undergoes a process called ubiquitination, where multiple ubiquitin molecules are covalently attached to the target protein. Specifically, the glycine on the carboxyl terminus of the ubiquitin attaches to a lysine residue on the target protein. This ubiquitination process involves three enzymes and occurs in three distinct steps.

Experimental Detection of Ubiquitin

To experimentally determine the presence of ubiquitin or its conjugates, researchers typically use:

• SDS-PAGE: Denatured proteins are placed in an SDS-PAGE gel to observe their molecular weights and shifts.
• Western Blot: Specific antibodies

Nutritional Needs

D(calciferol); it helps the calcification of our bones, it is present in milk and dairy products, fish liver oil. C(ascorbic acid), antioxidant and it keeps mucus normal and healthy, it is present in citrus fruits, strawberries, and vegetables.

Structural

The most important structural nutrients are proteins, although certain lipids, cell membranes, and certain salts such as the ones that form our skeleton.

Energy Needs

Our body needs energy to perform any physical activity. Energy nutrients (carbohydrates and fats) can be obtained from proteins, this process is possible due to cell respiration.

Different Caloric Values

One gram of fat 9 kcal, one gram of carbohydrates 3.75 kcal, one gram of protein 4 kcal.

Basal Metabolic Rate and